| \input texinfo @c -*-texinfo-*- |
| @c Copyright (C) 1988-1996, 1998-2012 Free Software Foundation, Inc. |
| @c |
| @c %**start of header |
| @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use |
| @c of @set vars. However, you can override filename with makeinfo -o. |
| @setfilename gdb.info |
| @c |
| @include gdb-cfg.texi |
| @c |
| @settitle Debugging with @value{GDBN} |
| @setchapternewpage odd |
| @c %**end of header |
| |
| @iftex |
| @c @smallbook |
| @c @cropmarks |
| @end iftex |
| |
| @finalout |
| @c To avoid file-name clashes between index.html and Index.html, when |
| @c the manual is produced on a Posix host and then moved to a |
| @c case-insensitive filesystem (e.g., MS-Windows), we separate the |
| @c indices into two: Concept Index and all the rest. |
| @syncodeindex ky fn |
| @syncodeindex tp fn |
| |
| @c readline appendices use @vindex, @findex and @ftable, |
| @c annotate.texi and gdbmi use @findex. |
| @syncodeindex vr fn |
| @syncodeindex fn fn |
| |
| @c !!set GDB manual's edition---not the same as GDB version! |
| @c This is updated by GNU Press. |
| @set EDITION Tenth |
| |
| @c !!set GDB edit command default editor |
| @set EDITOR /bin/ex |
| |
| @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER. |
| |
| @c This is a dir.info fragment to support semi-automated addition of |
| @c manuals to an info tree. |
| @dircategory Software development |
| @direntry |
| * Gdb: (gdb). The GNU debugger. |
| @end direntry |
| |
| @copying |
| Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, |
| 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
| 2011, 2012 |
| Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Free Software'' and ``Free Software Needs |
| Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,'' |
| and with the Back-Cover Texts as in (a) below. |
| |
| (a) The FSF's Back-Cover Text is: ``You are free to copy and modify |
| this GNU Manual. Buying copies from GNU Press supports the FSF in |
| developing GNU and promoting software freedom.'' |
| @end copying |
| |
| @ifnottex |
| This file documents the @sc{gnu} debugger @value{GDBN}. |
| |
| This is the @value{EDITION} Edition, of @cite{Debugging with |
| @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN} |
| @ifset VERSION_PACKAGE |
| @value{VERSION_PACKAGE} |
| @end ifset |
| Version @value{GDBVN}. |
| |
| @insertcopying |
| @end ifnottex |
| |
| @titlepage |
| @title Debugging with @value{GDBN} |
| @subtitle The @sc{gnu} Source-Level Debugger |
| @sp 1 |
| @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN} |
| @ifset VERSION_PACKAGE |
| @sp 1 |
| @subtitle @value{VERSION_PACKAGE} |
| @end ifset |
| @author Richard Stallman, Roland Pesch, Stan Shebs, et al. |
| @page |
| @tex |
| {\parskip=0pt |
| \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par |
| \hfill {\it Debugging with @value{GDBN}}\par |
| \hfill \TeX{}info \texinfoversion\par |
| } |
| @end tex |
| |
| @vskip 0pt plus 1filll |
| Published by the Free Software Foundation @* |
| 51 Franklin Street, Fifth Floor, |
| Boston, MA 02110-1301, USA@* |
| ISBN 978-0-9831592-3-0 @* |
| |
| @insertcopying |
| @end titlepage |
| @page |
| |
| @ifnottex |
| @node Top, Summary, (dir), (dir) |
| |
| @top Debugging with @value{GDBN} |
| |
| This file describes @value{GDBN}, the @sc{gnu} symbolic debugger. |
| |
| This is the @value{EDITION} Edition, for @value{GDBN} |
| @ifset VERSION_PACKAGE |
| @value{VERSION_PACKAGE} |
| @end ifset |
| Version @value{GDBVN}. |
| |
| Copyright (C) 1988-2012 Free Software Foundation, Inc. |
| |
| This edition of the GDB manual is dedicated to the memory of Fred |
| Fish. Fred was a long-standing contributor to GDB and to Free |
| software in general. We will miss him. |
| |
| @menu |
| * Summary:: Summary of @value{GDBN} |
| * Sample Session:: A sample @value{GDBN} session |
| |
| * Invocation:: Getting in and out of @value{GDBN} |
| * Commands:: @value{GDBN} commands |
| * Running:: Running programs under @value{GDBN} |
| * Stopping:: Stopping and continuing |
| * Reverse Execution:: Running programs backward |
| * Process Record and Replay:: Recording inferior's execution and replaying it |
| * Stack:: Examining the stack |
| * Source:: Examining source files |
| * Data:: Examining data |
| * Optimized Code:: Debugging optimized code |
| * Macros:: Preprocessor Macros |
| * Tracepoints:: Debugging remote targets non-intrusively |
| * Overlays:: Debugging programs that use overlays |
| |
| * Languages:: Using @value{GDBN} with different languages |
| |
| * Symbols:: Examining the symbol table |
| * Altering:: Altering execution |
| * GDB Files:: @value{GDBN} files |
| * Targets:: Specifying a debugging target |
| * Remote Debugging:: Debugging remote programs |
| * Configurations:: Configuration-specific information |
| * Controlling GDB:: Controlling @value{GDBN} |
| * Extending GDB:: Extending @value{GDBN} |
| * Interpreters:: Command Interpreters |
| * TUI:: @value{GDBN} Text User Interface |
| * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs |
| * GDB/MI:: @value{GDBN}'s Machine Interface. |
| * Annotations:: @value{GDBN}'s annotation interface. |
| * JIT Interface:: Using the JIT debugging interface. |
| * In-Process Agent:: In-Process Agent |
| |
| * GDB Bugs:: Reporting bugs in @value{GDBN} |
| |
| @ifset SYSTEM_READLINE |
| * Command Line Editing: (rluserman). Command Line Editing |
| * Using History Interactively: (history). Using History Interactively |
| @end ifset |
| @ifclear SYSTEM_READLINE |
| * Command Line Editing:: Command Line Editing |
| * Using History Interactively:: Using History Interactively |
| @end ifclear |
| * In Memoriam:: In Memoriam |
| * Formatting Documentation:: How to format and print @value{GDBN} documentation |
| * Installing GDB:: Installing GDB |
| * Maintenance Commands:: Maintenance Commands |
| * Remote Protocol:: GDB Remote Serial Protocol |
| * Agent Expressions:: The GDB Agent Expression Mechanism |
| * Target Descriptions:: How targets can describe themselves to |
| @value{GDBN} |
| * Operating System Information:: Getting additional information from |
| the operating system |
| * Trace File Format:: GDB trace file format |
| * Index Section Format:: .gdb_index section format |
| * Copying:: GNU General Public License says |
| how you can copy and share GDB |
| * GNU Free Documentation License:: The license for this documentation |
| * Concept Index:: Index of @value{GDBN} concepts |
| * Command and Variable Index:: Index of @value{GDBN} commands, variables, |
| functions, and Python data types |
| @end menu |
| |
| @end ifnottex |
| |
| @contents |
| |
| @node Summary |
| @unnumbered Summary of @value{GDBN} |
| |
| The purpose of a debugger such as @value{GDBN} is to allow you to see what is |
| going on ``inside'' another program while it executes---or what another |
| program was doing at the moment it crashed. |
| |
| @value{GDBN} can do four main kinds of things (plus other things in support of |
| these) to help you catch bugs in the act: |
| |
| @itemize @bullet |
| @item |
| Start your program, specifying anything that might affect its behavior. |
| |
| @item |
| Make your program stop on specified conditions. |
| |
| @item |
| Examine what has happened, when your program has stopped. |
| |
| @item |
| Change things in your program, so you can experiment with correcting the |
| effects of one bug and go on to learn about another. |
| @end itemize |
| |
| You can use @value{GDBN} to debug programs written in C and C@t{++}. |
| For more information, see @ref{Supported Languages,,Supported Languages}. |
| For more information, see @ref{C,,C and C++}. |
| |
| Support for D is partial. For information on D, see |
| @ref{D,,D}. |
| |
| @cindex Modula-2 |
| Support for Modula-2 is partial. For information on Modula-2, see |
| @ref{Modula-2,,Modula-2}. |
| |
| Support for OpenCL C is partial. For information on OpenCL C, see |
| @ref{OpenCL C,,OpenCL C}. |
| |
| @cindex Pascal |
| Debugging Pascal programs which use sets, subranges, file variables, or |
| nested functions does not currently work. @value{GDBN} does not support |
| entering expressions, printing values, or similar features using Pascal |
| syntax. |
| |
| @cindex Fortran |
| @value{GDBN} can be used to debug programs written in Fortran, although |
| it may be necessary to refer to some variables with a trailing |
| underscore. |
| |
| @value{GDBN} can be used to debug programs written in Objective-C, |
| using either the Apple/NeXT or the GNU Objective-C runtime. |
| |
| @menu |
| * Free Software:: Freely redistributable software |
| * Free Documentation:: Free Software Needs Free Documentation |
| * Contributors:: Contributors to GDB |
| @end menu |
| |
| @node Free Software |
| @unnumberedsec Free Software |
| |
| @value{GDBN} is @dfn{free software}, protected by the @sc{gnu} |
| General Public License |
| (GPL). The GPL gives you the freedom to copy or adapt a licensed |
| program---but every person getting a copy also gets with it the |
| freedom to modify that copy (which means that they must get access to |
| the source code), and the freedom to distribute further copies. |
| Typical software companies use copyrights to limit your freedoms; the |
| Free Software Foundation uses the GPL to preserve these freedoms. |
| |
| Fundamentally, the General Public License is a license which says that |
| you have these freedoms and that you cannot take these freedoms away |
| from anyone else. |
| |
| @node Free Documentation |
| @unnumberedsec Free Software Needs Free Documentation |
| |
| The biggest deficiency in the free software community today is not in |
| the software---it is the lack of good free documentation that we can |
| include with the free software. Many of our most important |
| programs do not come with free reference manuals and free introductory |
| texts. Documentation is an essential part of any software package; |
| when an important free software package does not come with a free |
| manual and a free tutorial, that is a major gap. We have many such |
| gaps today. |
| |
| Consider Perl, for instance. The tutorial manuals that people |
| normally use are non-free. How did this come about? Because the |
| authors of those manuals published them with restrictive terms---no |
| copying, no modification, source files not available---which exclude |
| them from the free software world. |
| |
| That wasn't the first time this sort of thing happened, and it was far |
| from the last. Many times we have heard a GNU user eagerly describe a |
| manual that he is writing, his intended contribution to the community, |
| only to learn that he had ruined everything by signing a publication |
| contract to make it non-free. |
| |
| Free documentation, like free software, is a matter of freedom, not |
| price. The problem with the non-free manual is not that publishers |
| charge a price for printed copies---that in itself is fine. (The Free |
| Software Foundation sells printed copies of manuals, too.) The |
| problem is the restrictions on the use of the manual. Free manuals |
| are available in source code form, and give you permission to copy and |
| modify. Non-free manuals do not allow this. |
| |
| The criteria of freedom for a free manual are roughly the same as for |
| free software. Redistribution (including the normal kinds of |
| commercial redistribution) must be permitted, so that the manual can |
| accompany every copy of the program, both on-line and on paper. |
| |
| Permission for modification of the technical content is crucial too. |
| When people modify the software, adding or changing features, if they |
| are conscientious they will change the manual too---so they can |
| provide accurate and clear documentation for the modified program. A |
| manual that leaves you no choice but to write a new manual to document |
| a changed version of the program is not really available to our |
| community. |
| |
| Some kinds of limits on the way modification is handled are |
| acceptable. For example, requirements to preserve the original |
| author's copyright notice, the distribution terms, or the list of |
| authors, are ok. It is also no problem to require modified versions |
| to include notice that they were modified. Even entire sections that |
| may not be deleted or changed are acceptable, as long as they deal |
| with nontechnical topics (like this one). These kinds of restrictions |
| are acceptable because they don't obstruct the community's normal use |
| of the manual. |
| |
| However, it must be possible to modify all the @emph{technical} |
| content of the manual, and then distribute the result in all the usual |
| media, through all the usual channels. Otherwise, the restrictions |
| obstruct the use of the manual, it is not free, and we need another |
| manual to replace it. |
| |
| Please spread the word about this issue. Our community continues to |
| lose manuals to proprietary publishing. If we spread the word that |
| free software needs free reference manuals and free tutorials, perhaps |
| the next person who wants to contribute by writing documentation will |
| realize, before it is too late, that only free manuals contribute to |
| the free software community. |
| |
| If you are writing documentation, please insist on publishing it under |
| the GNU Free Documentation License or another free documentation |
| license. Remember that this decision requires your approval---you |
| don't have to let the publisher decide. Some commercial publishers |
| will use a free license if you insist, but they will not propose the |
| option; it is up to you to raise the issue and say firmly that this is |
| what you want. If the publisher you are dealing with refuses, please |
| try other publishers. If you're not sure whether a proposed license |
| is free, write to @email{licensing@@gnu.org}. |
| |
| You can encourage commercial publishers to sell more free, copylefted |
| manuals and tutorials by buying them, and particularly by buying |
| copies from the publishers that paid for their writing or for major |
| improvements. Meanwhile, try to avoid buying non-free documentation |
| at all. Check the distribution terms of a manual before you buy it, |
| and insist that whoever seeks your business must respect your freedom. |
| Check the history of the book, and try to reward the publishers that |
| have paid or pay the authors to work on it. |
| |
| The Free Software Foundation maintains a list of free documentation |
| published by other publishers, at |
| @url{http://www.fsf.org/doc/other-free-books.html}. |
| |
| @node Contributors |
| @unnumberedsec Contributors to @value{GDBN} |
| |
| Richard Stallman was the original author of @value{GDBN}, and of many |
| other @sc{gnu} programs. Many others have contributed to its |
| development. This section attempts to credit major contributors. One |
| of the virtues of free software is that everyone is free to contribute |
| to it; with regret, we cannot actually acknowledge everyone here. The |
| file @file{ChangeLog} in the @value{GDBN} distribution approximates a |
| blow-by-blow account. |
| |
| Changes much prior to version 2.0 are lost in the mists of time. |
| |
| @quotation |
| @emph{Plea:} Additions to this section are particularly welcome. If you |
| or your friends (or enemies, to be evenhanded) have been unfairly |
| omitted from this list, we would like to add your names! |
| @end quotation |
| |
| So that they may not regard their many labors as thankless, we |
| particularly thank those who shepherded @value{GDBN} through major |
| releases: |
| Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0); |
| Jim Blandy (release 4.18); |
| Jason Molenda (release 4.17); |
| Stan Shebs (release 4.14); |
| Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9); |
| Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4); |
| John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); |
| Jim Kingdon (releases 3.5, 3.4, and 3.3); |
| and Randy Smith (releases 3.2, 3.1, and 3.0). |
| |
| Richard Stallman, assisted at various times by Peter TerMaat, Chris |
| Hanson, and Richard Mlynarik, handled releases through 2.8. |
| |
| Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support |
| in @value{GDBN}, with significant additional contributions from Per |
| Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++} |
| demangler. Early work on C@t{++} was by Peter TerMaat (who also did |
| much general update work leading to release 3.0). |
| |
| @value{GDBN} uses the BFD subroutine library to examine multiple |
| object-file formats; BFD was a joint project of David V. |
| Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore. |
| |
| David Johnson wrote the original COFF support; Pace Willison did |
| the original support for encapsulated COFF. |
| |
| Brent Benson of Harris Computer Systems contributed DWARF 2 support. |
| |
| Adam de Boor and Bradley Davis contributed the ISI Optimum V support. |
| Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS |
| support. |
| Jean-Daniel Fekete contributed Sun 386i support. |
| Chris Hanson improved the HP9000 support. |
| Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support. |
| David Johnson contributed Encore Umax support. |
| Jyrki Kuoppala contributed Altos 3068 support. |
| Jeff Law contributed HP PA and SOM support. |
| Keith Packard contributed NS32K support. |
| Doug Rabson contributed Acorn Risc Machine support. |
| Bob Rusk contributed Harris Nighthawk CX-UX support. |
| Chris Smith contributed Convex support (and Fortran debugging). |
| Jonathan Stone contributed Pyramid support. |
| Michael Tiemann contributed SPARC support. |
| Tim Tucker contributed support for the Gould NP1 and Gould Powernode. |
| Pace Willison contributed Intel 386 support. |
| Jay Vosburgh contributed Symmetry support. |
| Marko Mlinar contributed OpenRISC 1000 support. |
| |
| Andreas Schwab contributed M68K @sc{gnu}/Linux support. |
| |
| Rich Schaefer and Peter Schauer helped with support of SunOS shared |
| libraries. |
| |
| Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree |
| about several machine instruction sets. |
| |
| Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop |
| remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM |
| contributed remote debugging modules for the i960, VxWorks, A29K UDI, |
| and RDI targets, respectively. |
| |
| Brian Fox is the author of the readline libraries providing |
| command-line editing and command history. |
| |
| Andrew Beers of SUNY Buffalo wrote the language-switching code, the |
| Modula-2 support, and contributed the Languages chapter of this manual. |
| |
| Fred Fish wrote most of the support for Unix System Vr4. |
| He also enhanced the command-completion support to cover C@t{++} overloaded |
| symbols. |
| |
| Hitachi America (now Renesas America), Ltd. sponsored the support for |
| H8/300, H8/500, and Super-H processors. |
| |
| NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors. |
| |
| Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D |
| processors. |
| |
| Toshiba sponsored the support for the TX39 Mips processor. |
| |
| Matsushita sponsored the support for the MN10200 and MN10300 processors. |
| |
| Fujitsu sponsored the support for SPARClite and FR30 processors. |
| |
| Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware |
| watchpoints. |
| |
| Michael Snyder added support for tracepoints. |
| |
| Stu Grossman wrote gdbserver. |
| |
| Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made |
| nearly innumerable bug fixes and cleanups throughout @value{GDBN}. |
| |
| The following people at the Hewlett-Packard Company contributed |
| support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0 |
| (narrow mode), HP's implementation of kernel threads, HP's aC@t{++} |
| compiler, and the Text User Interface (nee Terminal User Interface): |
| Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann, |
| Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase |
| provided HP-specific information in this manual. |
| |
| DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project. |
| Robert Hoehne made significant contributions to the DJGPP port. |
| |
| Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its |
| development since 1991. Cygnus engineers who have worked on @value{GDBN} |
| fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin |
| Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim |
| Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler, |
| Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek |
| Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In |
| addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton, |
| JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug |
| Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff |
| Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner, |
| Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin |
| Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela |
| Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David |
| Zuhn have made contributions both large and small. |
| |
| Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for |
| Cygnus Solutions, implemented the original @sc{gdb/mi} interface. |
| |
| Jim Blandy added support for preprocessor macros, while working for Red |
| Hat. |
| |
| Andrew Cagney designed @value{GDBN}'s architecture vector. Many |
| people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick |
| Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei |
| Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason |
| Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped |
| with the migration of old architectures to this new framework. |
| |
| Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s |
| unwinder framework, this consisting of a fresh new design featuring |
| frame IDs, independent frame sniffers, and the sentinel frame. Mark |
| Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the |
| libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and |
| trad unwinders. The architecture-specific changes, each involving a |
| complete rewrite of the architecture's frame code, were carried out by |
| Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane |
| Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel |
| Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei |
| Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich |
| Weigand. |
| |
| Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from |
| Tensilica, Inc.@: contributed support for Xtensa processors. Others |
| who have worked on the Xtensa port of @value{GDBN} in the past include |
| Steve Tjiang, John Newlin, and Scott Foehner. |
| |
| Michael Eager and staff of Xilinx, Inc., contributed support for the |
| Xilinx MicroBlaze architecture. |
| |
| @node Sample Session |
| @chapter A Sample @value{GDBN} Session |
| |
| You can use this manual at your leisure to read all about @value{GDBN}. |
| However, a handful of commands are enough to get started using the |
| debugger. This chapter illustrates those commands. |
| |
| @iftex |
| In this sample session, we emphasize user input like this: @b{input}, |
| to make it easier to pick out from the surrounding output. |
| @end iftex |
| |
| @c FIXME: this example may not be appropriate for some configs, where |
| @c FIXME...primary interest is in remote use. |
| |
| One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro |
| processor) exhibits the following bug: sometimes, when we change its |
| quote strings from the default, the commands used to capture one macro |
| definition within another stop working. In the following short @code{m4} |
| session, we define a macro @code{foo} which expands to @code{0000}; we |
| then use the @code{m4} built-in @code{defn} to define @code{bar} as the |
| same thing. However, when we change the open quote string to |
| @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same |
| procedure fails to define a new synonym @code{baz}: |
| |
| @smallexample |
| $ @b{cd gnu/m4} |
| $ @b{./m4} |
| @b{define(foo,0000)} |
| |
| @b{foo} |
| 0000 |
| @b{define(bar,defn(`foo'))} |
| |
| @b{bar} |
| 0000 |
| @b{changequote(<QUOTE>,<UNQUOTE>)} |
| |
| @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} |
| @b{baz} |
| @b{Ctrl-d} |
| m4: End of input: 0: fatal error: EOF in string |
| @end smallexample |
| |
| @noindent |
| Let us use @value{GDBN} to try to see what is going on. |
| |
| @smallexample |
| $ @b{@value{GDBP} m4} |
| @c FIXME: this falsifies the exact text played out, to permit smallbook |
| @c FIXME... format to come out better. |
| @value{GDBN} is free software and you are welcome to distribute copies |
| of it under certain conditions; type "show copying" to see |
| the conditions. |
| There is absolutely no warranty for @value{GDBN}; type "show warranty" |
| for details. |
| |
| @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc... |
| (@value{GDBP}) |
| @end smallexample |
| |
| @noindent |
| @value{GDBN} reads only enough symbol data to know where to find the |
| rest when needed; as a result, the first prompt comes up very quickly. |
| We now tell @value{GDBN} to use a narrower display width than usual, so |
| that examples fit in this manual. |
| |
| @smallexample |
| (@value{GDBP}) @b{set width 70} |
| @end smallexample |
| |
| @noindent |
| We need to see how the @code{m4} built-in @code{changequote} works. |
| Having looked at the source, we know the relevant subroutine is |
| @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN} |
| @code{break} command. |
| |
| @smallexample |
| (@value{GDBP}) @b{break m4_changequote} |
| Breakpoint 1 at 0x62f4: file builtin.c, line 879. |
| @end smallexample |
| |
| @noindent |
| Using the @code{run} command, we start @code{m4} running under @value{GDBN} |
| control; as long as control does not reach the @code{m4_changequote} |
| subroutine, the program runs as usual: |
| |
| @smallexample |
| (@value{GDBP}) @b{run} |
| Starting program: /work/Editorial/gdb/gnu/m4/m4 |
| @b{define(foo,0000)} |
| |
| @b{foo} |
| 0000 |
| @end smallexample |
| |
| @noindent |
| To trigger the breakpoint, we call @code{changequote}. @value{GDBN} |
| suspends execution of @code{m4}, displaying information about the |
| context where it stops. |
| |
| @smallexample |
| @b{changequote(<QUOTE>,<UNQUOTE>)} |
| |
| Breakpoint 1, m4_changequote (argc=3, argv=0x33c70) |
| at builtin.c:879 |
| 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3)) |
| @end smallexample |
| |
| @noindent |
| Now we use the command @code{n} (@code{next}) to advance execution to |
| the next line of the current function. |
| |
| @smallexample |
| (@value{GDBP}) @b{n} |
| 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\ |
| : nil, |
| @end smallexample |
| |
| @noindent |
| @code{set_quotes} looks like a promising subroutine. We can go into it |
| by using the command @code{s} (@code{step}) instead of @code{next}. |
| @code{step} goes to the next line to be executed in @emph{any} |
| subroutine, so it steps into @code{set_quotes}. |
| |
| @smallexample |
| (@value{GDBP}) @b{s} |
| set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") |
| at input.c:530 |
| 530 if (lquote != def_lquote) |
| @end smallexample |
| |
| @noindent |
| The display that shows the subroutine where @code{m4} is now |
| suspended (and its arguments) is called a stack frame display. It |
| shows a summary of the stack. We can use the @code{backtrace} |
| command (which can also be spelled @code{bt}), to see where we are |
| in the stack as a whole: the @code{backtrace} command displays a |
| stack frame for each active subroutine. |
| |
| @smallexample |
| (@value{GDBP}) @b{bt} |
| #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") |
| at input.c:530 |
| #1 0x6344 in m4_changequote (argc=3, argv=0x33c70) |
| at builtin.c:882 |
| #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242 |
| #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30) |
| at macro.c:71 |
| #4 0x79dc in expand_input () at macro.c:40 |
| #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195 |
| @end smallexample |
| |
| @noindent |
| We step through a few more lines to see what happens. The first two |
| times, we can use @samp{s}; the next two times we use @code{n} to avoid |
| falling into the @code{xstrdup} subroutine. |
| |
| @smallexample |
| (@value{GDBP}) @b{s} |
| 0x3b5c 532 if (rquote != def_rquote) |
| (@value{GDBP}) @b{s} |
| 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \ |
| def_lquote : xstrdup(lq); |
| (@value{GDBP}) @b{n} |
| 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ |
| : xstrdup(rq); |
| (@value{GDBP}) @b{n} |
| 538 len_lquote = strlen(rquote); |
| @end smallexample |
| |
| @noindent |
| The last line displayed looks a little odd; we can examine the variables |
| @code{lquote} and @code{rquote} to see if they are in fact the new left |
| and right quotes we specified. We use the command @code{p} |
| (@code{print}) to see their values. |
| |
| @smallexample |
| (@value{GDBP}) @b{p lquote} |
| $1 = 0x35d40 "<QUOTE>" |
| (@value{GDBP}) @b{p rquote} |
| $2 = 0x35d50 "<UNQUOTE>" |
| @end smallexample |
| |
| @noindent |
| @code{lquote} and @code{rquote} are indeed the new left and right quotes. |
| To look at some context, we can display ten lines of source |
| surrounding the current line with the @code{l} (@code{list}) command. |
| |
| @smallexample |
| (@value{GDBP}) @b{l} |
| 533 xfree(rquote); |
| 534 |
| 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\ |
| : xstrdup (lq); |
| 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\ |
| : xstrdup (rq); |
| 537 |
| 538 len_lquote = strlen(rquote); |
| 539 len_rquote = strlen(lquote); |
| 540 @} |
| 541 |
| 542 void |
| @end smallexample |
| |
| @noindent |
| Let us step past the two lines that set @code{len_lquote} and |
| @code{len_rquote}, and then examine the values of those variables. |
| |
| @smallexample |
| (@value{GDBP}) @b{n} |
| 539 len_rquote = strlen(lquote); |
| (@value{GDBP}) @b{n} |
| 540 @} |
| (@value{GDBP}) @b{p len_lquote} |
| $3 = 9 |
| (@value{GDBP}) @b{p len_rquote} |
| $4 = 7 |
| @end smallexample |
| |
| @noindent |
| That certainly looks wrong, assuming @code{len_lquote} and |
| @code{len_rquote} are meant to be the lengths of @code{lquote} and |
| @code{rquote} respectively. We can set them to better values using |
| the @code{p} command, since it can print the value of |
| any expression---and that expression can include subroutine calls and |
| assignments. |
| |
| @smallexample |
| (@value{GDBP}) @b{p len_lquote=strlen(lquote)} |
| $5 = 7 |
| (@value{GDBP}) @b{p len_rquote=strlen(rquote)} |
| $6 = 9 |
| @end smallexample |
| |
| @noindent |
| Is that enough to fix the problem of using the new quotes with the |
| @code{m4} built-in @code{defn}? We can allow @code{m4} to continue |
| executing with the @code{c} (@code{continue}) command, and then try the |
| example that caused trouble initially: |
| |
| @smallexample |
| (@value{GDBP}) @b{c} |
| Continuing. |
| |
| @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))} |
| |
| baz |
| 0000 |
| @end smallexample |
| |
| @noindent |
| Success! The new quotes now work just as well as the default ones. The |
| problem seems to have been just the two typos defining the wrong |
| lengths. We allow @code{m4} exit by giving it an EOF as input: |
| |
| @smallexample |
| @b{Ctrl-d} |
| Program exited normally. |
| @end smallexample |
| |
| @noindent |
| The message @samp{Program exited normally.} is from @value{GDBN}; it |
| indicates @code{m4} has finished executing. We can end our @value{GDBN} |
| session with the @value{GDBN} @code{quit} command. |
| |
| @smallexample |
| (@value{GDBP}) @b{quit} |
| @end smallexample |
| |
| @node Invocation |
| @chapter Getting In and Out of @value{GDBN} |
| |
| This chapter discusses how to start @value{GDBN}, and how to get out of it. |
| The essentials are: |
| @itemize @bullet |
| @item |
| type @samp{@value{GDBP}} to start @value{GDBN}. |
| @item |
| type @kbd{quit} or @kbd{Ctrl-d} to exit. |
| @end itemize |
| |
| @menu |
| * Invoking GDB:: How to start @value{GDBN} |
| * Quitting GDB:: How to quit @value{GDBN} |
| * Shell Commands:: How to use shell commands inside @value{GDBN} |
| * Logging Output:: How to log @value{GDBN}'s output to a file |
| @end menu |
| |
| @node Invoking GDB |
| @section Invoking @value{GDBN} |
| |
| Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started, |
| @value{GDBN} reads commands from the terminal until you tell it to exit. |
| |
| You can also run @code{@value{GDBP}} with a variety of arguments and options, |
| to specify more of your debugging environment at the outset. |
| |
| The command-line options described here are designed |
| to cover a variety of situations; in some environments, some of these |
| options may effectively be unavailable. |
| |
| The most usual way to start @value{GDBN} is with one argument, |
| specifying an executable program: |
| |
| @smallexample |
| @value{GDBP} @var{program} |
| @end smallexample |
| |
| @noindent |
| You can also start with both an executable program and a core file |
| specified: |
| |
| @smallexample |
| @value{GDBP} @var{program} @var{core} |
| @end smallexample |
| |
| You can, instead, specify a process ID as a second argument, if you want |
| to debug a running process: |
| |
| @smallexample |
| @value{GDBP} @var{program} 1234 |
| @end smallexample |
| |
| @noindent |
| would attach @value{GDBN} to process @code{1234} (unless you also have a file |
| named @file{1234}; @value{GDBN} does check for a core file first). |
| |
| Taking advantage of the second command-line argument requires a fairly |
| complete operating system; when you use @value{GDBN} as a remote |
| debugger attached to a bare board, there may not be any notion of |
| ``process'', and there is often no way to get a core dump. @value{GDBN} |
| will warn you if it is unable to attach or to read core dumps. |
| |
| You can optionally have @code{@value{GDBP}} pass any arguments after the |
| executable file to the inferior using @code{--args}. This option stops |
| option processing. |
| @smallexample |
| @value{GDBP} --args gcc -O2 -c foo.c |
| @end smallexample |
| This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set |
| @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}. |
| |
| You can run @code{@value{GDBP}} without printing the front material, which describes |
| @value{GDBN}'s non-warranty, by specifying @code{-silent}: |
| |
| @smallexample |
| @value{GDBP} -silent |
| @end smallexample |
| |
| @noindent |
| You can further control how @value{GDBN} starts up by using command-line |
| options. @value{GDBN} itself can remind you of the options available. |
| |
| @noindent |
| Type |
| |
| @smallexample |
| @value{GDBP} -help |
| @end smallexample |
| |
| @noindent |
| to display all available options and briefly describe their use |
| (@samp{@value{GDBP} -h} is a shorter equivalent). |
| |
| All options and command line arguments you give are processed |
| in sequential order. The order makes a difference when the |
| @samp{-x} option is used. |
| |
| |
| @menu |
| * File Options:: Choosing files |
| * Mode Options:: Choosing modes |
| * Startup:: What @value{GDBN} does during startup |
| @end menu |
| |
| @node File Options |
| @subsection Choosing Files |
| |
| When @value{GDBN} starts, it reads any arguments other than options as |
| specifying an executable file and core file (or process ID). This is |
| the same as if the arguments were specified by the @samp{-se} and |
| @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the |
| first argument that does not have an associated option flag as |
| equivalent to the @samp{-se} option followed by that argument; and the |
| second argument that does not have an associated option flag, if any, as |
| equivalent to the @samp{-c}/@samp{-p} option followed by that argument.) |
| If the second argument begins with a decimal digit, @value{GDBN} will |
| first attempt to attach to it as a process, and if that fails, attempt |
| to open it as a corefile. If you have a corefile whose name begins with |
| a digit, you can prevent @value{GDBN} from treating it as a pid by |
| prefixing it with @file{./}, e.g.@: @file{./12345}. |
| |
| If @value{GDBN} has not been configured to included core file support, |
| such as for most embedded targets, then it will complain about a second |
| argument and ignore it. |
| |
| Many options have both long and short forms; both are shown in the |
| following list. @value{GDBN} also recognizes the long forms if you truncate |
| them, so long as enough of the option is present to be unambiguous. |
| (If you prefer, you can flag option arguments with @samp{--} rather |
| than @samp{-}, though we illustrate the more usual convention.) |
| |
| @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This |
| @c way, both those who look for -foo and --foo in the index, will find |
| @c it. |
| |
| @table @code |
| @item -symbols @var{file} |
| @itemx -s @var{file} |
| @cindex @code{--symbols} |
| @cindex @code{-s} |
| Read symbol table from file @var{file}. |
| |
| @item -exec @var{file} |
| @itemx -e @var{file} |
| @cindex @code{--exec} |
| @cindex @code{-e} |
| Use file @var{file} as the executable file to execute when appropriate, |
| and for examining pure data in conjunction with a core dump. |
| |
| @item -se @var{file} |
| @cindex @code{--se} |
| Read symbol table from file @var{file} and use it as the executable |
| file. |
| |
| @item -core @var{file} |
| @itemx -c @var{file} |
| @cindex @code{--core} |
| @cindex @code{-c} |
| Use file @var{file} as a core dump to examine. |
| |
| @item -pid @var{number} |
| @itemx -p @var{number} |
| @cindex @code{--pid} |
| @cindex @code{-p} |
| Connect to process ID @var{number}, as with the @code{attach} command. |
| |
| @item -command @var{file} |
| @itemx -x @var{file} |
| @cindex @code{--command} |
| @cindex @code{-x} |
| Execute commands from file @var{file}. The contents of this file is |
| evaluated exactly as the @code{source} command would. |
| @xref{Command Files,, Command files}. |
| |
| @item -eval-command @var{command} |
| @itemx -ex @var{command} |
| @cindex @code{--eval-command} |
| @cindex @code{-ex} |
| Execute a single @value{GDBN} command. |
| |
| This option may be used multiple times to call multiple commands. It may |
| also be interleaved with @samp{-command} as required. |
| |
| @smallexample |
| @value{GDBP} -ex 'target sim' -ex 'load' \ |
| -x setbreakpoints -ex 'run' a.out |
| @end smallexample |
| |
| @item -init-command @var{file} |
| @itemx -ix @var{file} |
| @cindex @code{--init-command} |
| @cindex @code{-ix} |
| Execute commands from file @var{file} before loading the inferior (but |
| after loading gdbinit files). |
| @xref{Startup}. |
| |
| @item -init-eval-command @var{command} |
| @itemx -iex @var{command} |
| @cindex @code{--init-eval-command} |
| @cindex @code{-iex} |
| Execute a single @value{GDBN} command before loading the inferior (but |
| after loading gdbinit files). |
| @xref{Startup}. |
| |
| @item -directory @var{directory} |
| @itemx -d @var{directory} |
| @cindex @code{--directory} |
| @cindex @code{-d} |
| Add @var{directory} to the path to search for source and script files. |
| |
| @item -r |
| @itemx -readnow |
| @cindex @code{--readnow} |
| @cindex @code{-r} |
| Read each symbol file's entire symbol table immediately, rather than |
| the default, which is to read it incrementally as it is needed. |
| This makes startup slower, but makes future operations faster. |
| |
| @end table |
| |
| @node Mode Options |
| @subsection Choosing Modes |
| |
| You can run @value{GDBN} in various alternative modes---for example, in |
| batch mode or quiet mode. |
| |
| @table @code |
| @anchor{-nx} |
| @item -nx |
| @itemx -n |
| @cindex @code{--nx} |
| @cindex @code{-n} |
| Do not execute commands found in any initialization files. Normally, |
| @value{GDBN} executes the commands in these files after all the command |
| options and arguments have been processed. @xref{Command Files,,Command |
| Files}. |
| |
| @item -quiet |
| @itemx -silent |
| @itemx -q |
| @cindex @code{--quiet} |
| @cindex @code{--silent} |
| @cindex @code{-q} |
| ``Quiet''. Do not print the introductory and copyright messages. These |
| messages are also suppressed in batch mode. |
| |
| @item -batch |
| @cindex @code{--batch} |
| Run in batch mode. Exit with status @code{0} after processing all the |
| command files specified with @samp{-x} (and all commands from |
| initialization files, if not inhibited with @samp{-n}). Exit with |
| nonzero status if an error occurs in executing the @value{GDBN} commands |
| in the command files. Batch mode also disables pagination, sets unlimited |
| terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm |
| off} were in effect (@pxref{Messages/Warnings}). |
| |
| Batch mode may be useful for running @value{GDBN} as a filter, for |
| example to download and run a program on another computer; in order to |
| make this more useful, the message |
| |
| @smallexample |
| Program exited normally. |
| @end smallexample |
| |
| @noindent |
| (which is ordinarily issued whenever a program running under |
| @value{GDBN} control terminates) is not issued when running in batch |
| mode. |
| |
| @item -batch-silent |
| @cindex @code{--batch-silent} |
| Run in batch mode exactly like @samp{-batch}, but totally silently. All |
| @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is |
| unaffected). This is much quieter than @samp{-silent} and would be useless |
| for an interactive session. |
| |
| This is particularly useful when using targets that give @samp{Loading section} |
| messages, for example. |
| |
| Note that targets that give their output via @value{GDBN}, as opposed to |
| writing directly to @code{stdout}, will also be made silent. |
| |
| @item -return-child-result |
| @cindex @code{--return-child-result} |
| The return code from @value{GDBN} will be the return code from the child |
| process (the process being debugged), with the following exceptions: |
| |
| @itemize @bullet |
| @item |
| @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an |
| internal error. In this case the exit code is the same as it would have been |
| without @samp{-return-child-result}. |
| @item |
| The user quits with an explicit value. E.g., @samp{quit 1}. |
| @item |
| The child process never runs, or is not allowed to terminate, in which case |
| the exit code will be -1. |
| @end itemize |
| |
| This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent}, |
| when @value{GDBN} is being used as a remote program loader or simulator |
| interface. |
| |
| @item -nowindows |
| @itemx -nw |
| @cindex @code{--nowindows} |
| @cindex @code{-nw} |
| ``No windows''. If @value{GDBN} comes with a graphical user interface |
| (GUI) built in, then this option tells @value{GDBN} to only use the command-line |
| interface. If no GUI is available, this option has no effect. |
| |
| @item -windows |
| @itemx -w |
| @cindex @code{--windows} |
| @cindex @code{-w} |
| If @value{GDBN} includes a GUI, then this option requires it to be |
| used if possible. |
| |
| @item -cd @var{directory} |
| @cindex @code{--cd} |
| Run @value{GDBN} using @var{directory} as its working directory, |
| instead of the current directory. |
| |
| @item -data-directory @var{directory} |
| @cindex @code{--data-directory} |
| Run @value{GDBN} using @var{directory} as its data directory. |
| The data directory is where @value{GDBN} searches for its |
| auxiliary files. @xref{Data Files}. |
| |
| @item -fullname |
| @itemx -f |
| @cindex @code{--fullname} |
| @cindex @code{-f} |
| @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a |
| subprocess. It tells @value{GDBN} to output the full file name and line |
| number in a standard, recognizable fashion each time a stack frame is |
| displayed (which includes each time your program stops). This |
| recognizable format looks like two @samp{\032} characters, followed by |
| the file name, line number and character position separated by colons, |
| and a newline. The Emacs-to-@value{GDBN} interface program uses the two |
| @samp{\032} characters as a signal to display the source code for the |
| frame. |
| |
| @item -epoch |
| @cindex @code{--epoch} |
| The Epoch Emacs-@value{GDBN} interface sets this option when it runs |
| @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print |
| routines so as to allow Epoch to display values of expressions in a |
| separate window. |
| |
| @item -annotate @var{level} |
| @cindex @code{--annotate} |
| This option sets the @dfn{annotation level} inside @value{GDBN}. Its |
| effect is identical to using @samp{set annotate @var{level}} |
| (@pxref{Annotations}). The annotation @var{level} controls how much |
| information @value{GDBN} prints together with its prompt, values of |
| expressions, source lines, and other types of output. Level 0 is the |
| normal, level 1 is for use when @value{GDBN} is run as a subprocess of |
| @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs |
| that control @value{GDBN}, and level 2 has been deprecated. |
| |
| The annotation mechanism has largely been superseded by @sc{gdb/mi} |
| (@pxref{GDB/MI}). |
| |
| @item --args |
| @cindex @code{--args} |
| Change interpretation of command line so that arguments following the |
| executable file are passed as command line arguments to the inferior. |
| This option stops option processing. |
| |
| @item -baud @var{bps} |
| @itemx -b @var{bps} |
| @cindex @code{--baud} |
| @cindex @code{-b} |
| Set the line speed (baud rate or bits per second) of any serial |
| interface used by @value{GDBN} for remote debugging. |
| |
| @item -l @var{timeout} |
| @cindex @code{-l} |
| Set the timeout (in seconds) of any communication used by @value{GDBN} |
| for remote debugging. |
| |
| @item -tty @var{device} |
| @itemx -t @var{device} |
| @cindex @code{--tty} |
| @cindex @code{-t} |
| Run using @var{device} for your program's standard input and output. |
| @c FIXME: kingdon thinks there is more to -tty. Investigate. |
| |
| @c resolve the situation of these eventually |
| @item -tui |
| @cindex @code{--tui} |
| Activate the @dfn{Text User Interface} when starting. The Text User |
| Interface manages several text windows on the terminal, showing |
| source, assembly, registers and @value{GDBN} command outputs |
| (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this |
| option if you run @value{GDBN} from Emacs (@pxref{Emacs, , |
| Using @value{GDBN} under @sc{gnu} Emacs}). |
| |
| @c @item -xdb |
| @c @cindex @code{--xdb} |
| @c Run in XDB compatibility mode, allowing the use of certain XDB commands. |
| @c For information, see the file @file{xdb_trans.html}, which is usually |
| @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX |
| @c systems. |
| |
| @item -interpreter @var{interp} |
| @cindex @code{--interpreter} |
| Use the interpreter @var{interp} for interface with the controlling |
| program or device. This option is meant to be set by programs which |
| communicate with @value{GDBN} using it as a back end. |
| @xref{Interpreters, , Command Interpreters}. |
| |
| @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes |
| @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, , |
| The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The |
| previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and |
| selected with @samp{--interpreter=mi1}, is deprecated. Earlier |
| @sc{gdb/mi} interfaces are no longer supported. |
| |
| @item -write |
| @cindex @code{--write} |
| Open the executable and core files for both reading and writing. This |
| is equivalent to the @samp{set write on} command inside @value{GDBN} |
| (@pxref{Patching}). |
| |
| @item -statistics |
| @cindex @code{--statistics} |
| This option causes @value{GDBN} to print statistics about time and |
| memory usage after it completes each command and returns to the prompt. |
| |
| @item -version |
| @cindex @code{--version} |
| This option causes @value{GDBN} to print its version number and |
| no-warranty blurb, and exit. |
| |
| @end table |
| |
| @node Startup |
| @subsection What @value{GDBN} Does During Startup |
| @cindex @value{GDBN} startup |
| |
| Here's the description of what @value{GDBN} does during session startup: |
| |
| @enumerate |
| @item |
| Sets up the command interpreter as specified by the command line |
| (@pxref{Mode Options, interpreter}). |
| |
| @item |
| @cindex init file |
| Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was |
| used when building @value{GDBN}; @pxref{System-wide configuration, |
| ,System-wide configuration and settings}) and executes all the commands in |
| that file. |
| |
| @anchor{Home Directory Init File} |
| @item |
| Reads the init file (if any) in your home directory@footnote{On |
| DOS/Windows systems, the home directory is the one pointed to by the |
| @code{HOME} environment variable.} and executes all the commands in |
| that file. |
| |
| @anchor{Option -init-eval-command} |
| @item |
| Executes commands and command files specified by the @samp{-iex} and |
| @samp{-ix} options in their specified order. Usually you should use the |
| @samp{-ex} and @samp{-x} options instead, but this way you can apply |
| settings before @value{GDBN} init files get executed and before inferior |
| gets loaded. |
| |
| @item |
| Processes command line options and operands. |
| |
| @anchor{Init File in the Current Directory during Startup} |
| @item |
| Reads and executes the commands from init file (if any) in the current |
| working directory as long as @samp{set auto-load local-gdbinit} is set to |
| @samp{on} (@pxref{Init File in the Current Directory}). |
| This is only done if the current directory is |
| different from your home directory. Thus, you can have more than one |
| init file, one generic in your home directory, and another, specific |
| to the program you are debugging, in the directory where you invoke |
| @value{GDBN}. |
| |
| @item |
| If the command line specified a program to debug, or a process to |
| attach to, or a core file, @value{GDBN} loads any auto-loaded |
| scripts provided for the program or for its loaded shared libraries. |
| @xref{Auto-loading}. |
| |
| If you wish to disable the auto-loading during startup, |
| you must do something like the following: |
| |
| @smallexample |
| $ gdb -iex "set auto-load python-scripts off" myprogram |
| @end smallexample |
| |
| Option @samp{-ex} does not work because the auto-loading is then turned |
| off too late. |
| |
| @item |
| Executes commands and command files specified by the @samp{-ex} and |
| @samp{-x} options in their specified order. @xref{Command Files}, for |
| more details about @value{GDBN} command files. |
| |
| @item |
| Reads the command history recorded in the @dfn{history file}. |
| @xref{Command History}, for more details about the command history and the |
| files where @value{GDBN} records it. |
| @end enumerate |
| |
| Init files use the same syntax as @dfn{command files} (@pxref{Command |
| Files}) and are processed by @value{GDBN} in the same way. The init |
| file in your home directory can set options (such as @samp{set |
| complaints}) that affect subsequent processing of command line options |
| and operands. Init files are not executed if you use the @samp{-nx} |
| option (@pxref{Mode Options, ,Choosing Modes}). |
| |
| To display the list of init files loaded by gdb at startup, you |
| can use @kbd{gdb --help}. |
| |
| @cindex init file name |
| @cindex @file{.gdbinit} |
| @cindex @file{gdb.ini} |
| The @value{GDBN} init files are normally called @file{.gdbinit}. |
| The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to |
| the limitations of file names imposed by DOS filesystems. The Windows |
| ports of @value{GDBN} use the standard name, but if they find a |
| @file{gdb.ini} file, they warn you about that and suggest to rename |
| the file to the standard name. |
| |
| |
| @node Quitting GDB |
| @section Quitting @value{GDBN} |
| @cindex exiting @value{GDBN} |
| @cindex leaving @value{GDBN} |
| |
| @table @code |
| @kindex quit @r{[}@var{expression}@r{]} |
| @kindex q @r{(@code{quit})} |
| @item quit @r{[}@var{expression}@r{]} |
| @itemx q |
| To exit @value{GDBN}, use the @code{quit} command (abbreviated |
| @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you |
| do not supply @var{expression}, @value{GDBN} will terminate normally; |
| otherwise it will terminate using the result of @var{expression} as the |
| error code. |
| @end table |
| |
| @cindex interrupt |
| An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather |
| terminates the action of any @value{GDBN} command that is in progress and |
| returns to @value{GDBN} command level. It is safe to type the interrupt |
| character at any time because @value{GDBN} does not allow it to take effect |
| until a time when it is safe. |
| |
| If you have been using @value{GDBN} to control an attached process or |
| device, you can release it with the @code{detach} command |
| (@pxref{Attach, ,Debugging an Already-running Process}). |
| |
| @node Shell Commands |
| @section Shell Commands |
| |
| If you need to execute occasional shell commands during your |
| debugging session, there is no need to leave or suspend @value{GDBN}; you can |
| just use the @code{shell} command. |
| |
| @table @code |
| @kindex shell |
| @kindex ! |
| @cindex shell escape |
| @item shell @var{command-string} |
| @itemx !@var{command-string} |
| Invoke a standard shell to execute @var{command-string}. |
| Note that no space is needed between @code{!} and @var{command-string}. |
| If it exists, the environment variable @code{SHELL} determines which |
| shell to run. Otherwise @value{GDBN} uses the default shell |
| (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.). |
| @end table |
| |
| The utility @code{make} is often needed in development environments. |
| You do not have to use the @code{shell} command for this purpose in |
| @value{GDBN}: |
| |
| @table @code |
| @kindex make |
| @cindex calling make |
| @item make @var{make-args} |
| Execute the @code{make} program with the specified |
| arguments. This is equivalent to @samp{shell make @var{make-args}}. |
| @end table |
| |
| @node Logging Output |
| @section Logging Output |
| @cindex logging @value{GDBN} output |
| @cindex save @value{GDBN} output to a file |
| |
| You may want to save the output of @value{GDBN} commands to a file. |
| There are several commands to control @value{GDBN}'s logging. |
| |
| @table @code |
| @kindex set logging |
| @item set logging on |
| Enable logging. |
| @item set logging off |
| Disable logging. |
| @cindex logging file name |
| @item set logging file @var{file} |
| Change the name of the current logfile. The default logfile is @file{gdb.txt}. |
| @item set logging overwrite [on|off] |
| By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if |
| you want @code{set logging on} to overwrite the logfile instead. |
| @item set logging redirect [on|off] |
| By default, @value{GDBN} output will go to both the terminal and the logfile. |
| Set @code{redirect} if you want output to go only to the log file. |
| @kindex show logging |
| @item show logging |
| Show the current values of the logging settings. |
| @end table |
| |
| @node Commands |
| @chapter @value{GDBN} Commands |
| |
| You can abbreviate a @value{GDBN} command to the first few letters of the command |
| name, if that abbreviation is unambiguous; and you can repeat certain |
| @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB} |
| key to get @value{GDBN} to fill out the rest of a word in a command (or to |
| show you the alternatives available, if there is more than one possibility). |
| |
| @menu |
| * Command Syntax:: How to give commands to @value{GDBN} |
| * Completion:: Command completion |
| * Help:: How to ask @value{GDBN} for help |
| @end menu |
| |
| @node Command Syntax |
| @section Command Syntax |
| |
| A @value{GDBN} command is a single line of input. There is no limit on |
| how long it can be. It starts with a command name, which is followed by |
| arguments whose meaning depends on the command name. For example, the |
| command @code{step} accepts an argument which is the number of times to |
| step, as in @samp{step 5}. You can also use the @code{step} command |
| with no arguments. Some commands do not allow any arguments. |
| |
| @cindex abbreviation |
| @value{GDBN} command names may always be truncated if that abbreviation is |
| unambiguous. Other possible command abbreviations are listed in the |
| documentation for individual commands. In some cases, even ambiguous |
| abbreviations are allowed; for example, @code{s} is specially defined as |
| equivalent to @code{step} even though there are other commands whose |
| names start with @code{s}. You can test abbreviations by using them as |
| arguments to the @code{help} command. |
| |
| @cindex repeating commands |
| @kindex RET @r{(repeat last command)} |
| A blank line as input to @value{GDBN} (typing just @key{RET}) means to |
| repeat the previous command. Certain commands (for example, @code{run}) |
| will not repeat this way; these are commands whose unintentional |
| repetition might cause trouble and which you are unlikely to want to |
| repeat. User-defined commands can disable this feature; see |
| @ref{Define, dont-repeat}. |
| |
| The @code{list} and @code{x} commands, when you repeat them with |
| @key{RET}, construct new arguments rather than repeating |
| exactly as typed. This permits easy scanning of source or memory. |
| |
| @value{GDBN} can also use @key{RET} in another way: to partition lengthy |
| output, in a way similar to the common utility @code{more} |
| (@pxref{Screen Size,,Screen Size}). Since it is easy to press one |
| @key{RET} too many in this situation, @value{GDBN} disables command |
| repetition after any command that generates this sort of display. |
| |
| @kindex # @r{(a comment)} |
| @cindex comment |
| Any text from a @kbd{#} to the end of the line is a comment; it does |
| nothing. This is useful mainly in command files (@pxref{Command |
| Files,,Command Files}). |
| |
| @cindex repeating command sequences |
| @kindex Ctrl-o @r{(operate-and-get-next)} |
| The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of |
| commands. This command accepts the current line, like @key{RET}, and |
| then fetches the next line relative to the current line from the history |
| for editing. |
| |
| @node Completion |
| @section Command Completion |
| |
| @cindex completion |
| @cindex word completion |
| @value{GDBN} can fill in the rest of a word in a command for you, if there is |
| only one possibility; it can also show you what the valid possibilities |
| are for the next word in a command, at any time. This works for @value{GDBN} |
| commands, @value{GDBN} subcommands, and the names of symbols in your program. |
| |
| Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest |
| of a word. If there is only one possibility, @value{GDBN} fills in the |
| word, and waits for you to finish the command (or press @key{RET} to |
| enter it). For example, if you type |
| |
| @c FIXME "@key" does not distinguish its argument sufficiently to permit |
| @c complete accuracy in these examples; space introduced for clarity. |
| @c If texinfo enhancements make it unnecessary, it would be nice to |
| @c replace " @key" by "@key" in the following... |
| @smallexample |
| (@value{GDBP}) info bre @key{TAB} |
| @end smallexample |
| |
| @noindent |
| @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is |
| the only @code{info} subcommand beginning with @samp{bre}: |
| |
| @smallexample |
| (@value{GDBP}) info breakpoints |
| @end smallexample |
| |
| @noindent |
| You can either press @key{RET} at this point, to run the @code{info |
| breakpoints} command, or backspace and enter something else, if |
| @samp{breakpoints} does not look like the command you expected. (If you |
| were sure you wanted @code{info breakpoints} in the first place, you |
| might as well just type @key{RET} immediately after @samp{info bre}, |
| to exploit command abbreviations rather than command completion). |
| |
| If there is more than one possibility for the next word when you press |
| @key{TAB}, @value{GDBN} sounds a bell. You can either supply more |
| characters and try again, or just press @key{TAB} a second time; |
| @value{GDBN} displays all the possible completions for that word. For |
| example, you might want to set a breakpoint on a subroutine whose name |
| begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN} |
| just sounds the bell. Typing @key{TAB} again displays all the |
| function names in your program that begin with those characters, for |
| example: |
| |
| @smallexample |
| (@value{GDBP}) b make_ @key{TAB} |
| @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see: |
| make_a_section_from_file make_environ |
| make_abs_section make_function_type |
| make_blockvector make_pointer_type |
| make_cleanup make_reference_type |
| make_command make_symbol_completion_list |
| (@value{GDBP}) b make_ |
| @end smallexample |
| |
| @noindent |
| After displaying the available possibilities, @value{GDBN} copies your |
| partial input (@samp{b make_} in the example) so you can finish the |
| command. |
| |
| If you just want to see the list of alternatives in the first place, you |
| can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?} |
| means @kbd{@key{META} ?}. You can type this either by holding down a |
| key designated as the @key{META} shift on your keyboard (if there is |
| one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}. |
| |
| @cindex quotes in commands |
| @cindex completion of quoted strings |
| Sometimes the string you need, while logically a ``word'', may contain |
| parentheses or other characters that @value{GDBN} normally excludes from |
| its notion of a word. To permit word completion to work in this |
| situation, you may enclose words in @code{'} (single quote marks) in |
| @value{GDBN} commands. |
| |
| The most likely situation where you might need this is in typing the |
| name of a C@t{++} function. This is because C@t{++} allows function |
| overloading (multiple definitions of the same function, distinguished |
| by argument type). For example, when you want to set a breakpoint you |
| may need to distinguish whether you mean the version of @code{name} |
| that takes an @code{int} parameter, @code{name(int)}, or the version |
| that takes a @code{float} parameter, @code{name(float)}. To use the |
| word-completion facilities in this situation, type a single quote |
| @code{'} at the beginning of the function name. This alerts |
| @value{GDBN} that it may need to consider more information than usual |
| when you press @key{TAB} or @kbd{M-?} to request word completion: |
| |
| @smallexample |
| (@value{GDBP}) b 'bubble( @kbd{M-?} |
| bubble(double,double) bubble(int,int) |
| (@value{GDBP}) b 'bubble( |
| @end smallexample |
| |
| In some cases, @value{GDBN} can tell that completing a name requires using |
| quotes. When this happens, @value{GDBN} inserts the quote for you (while |
| completing as much as it can) if you do not type the quote in the first |
| place: |
| |
| @smallexample |
| (@value{GDBP}) b bub @key{TAB} |
| @exdent @value{GDBN} alters your input line to the following, and rings a bell: |
| (@value{GDBP}) b 'bubble( |
| @end smallexample |
| |
| @noindent |
| In general, @value{GDBN} can tell that a quote is needed (and inserts it) if |
| you have not yet started typing the argument list when you ask for |
| completion on an overloaded symbol. |
| |
| For more information about overloaded functions, see @ref{C Plus Plus |
| Expressions, ,C@t{++} Expressions}. You can use the command @code{set |
| overload-resolution off} to disable overload resolution; |
| see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}. |
| |
| @cindex completion of structure field names |
| @cindex structure field name completion |
| @cindex completion of union field names |
| @cindex union field name completion |
| When completing in an expression which looks up a field in a |
| structure, @value{GDBN} also tries@footnote{The completer can be |
| confused by certain kinds of invalid expressions. Also, it only |
| examines the static type of the expression, not the dynamic type.} to |
| limit completions to the field names available in the type of the |
| left-hand-side: |
| |
| @smallexample |
| (@value{GDBP}) p gdb_stdout.@kbd{M-?} |
| magic to_fputs to_rewind |
| to_data to_isatty to_write |
| to_delete to_put to_write_async_safe |
| to_flush to_read |
| @end smallexample |
| |
| @noindent |
| This is because the @code{gdb_stdout} is a variable of the type |
| @code{struct ui_file} that is defined in @value{GDBN} sources as |
| follows: |
| |
| @smallexample |
| struct ui_file |
| @{ |
| int *magic; |
| ui_file_flush_ftype *to_flush; |
| ui_file_write_ftype *to_write; |
| ui_file_write_async_safe_ftype *to_write_async_safe; |
| ui_file_fputs_ftype *to_fputs; |
| ui_file_read_ftype *to_read; |
| ui_file_delete_ftype *to_delete; |
| ui_file_isatty_ftype *to_isatty; |
| ui_file_rewind_ftype *to_rewind; |
| ui_file_put_ftype *to_put; |
| void *to_data; |
| @} |
| @end smallexample |
| |
| |
| @node Help |
| @section Getting Help |
| @cindex online documentation |
| @kindex help |
| |
| You can always ask @value{GDBN} itself for information on its commands, |
| using the command @code{help}. |
| |
| @table @code |
| @kindex h @r{(@code{help})} |
| @item help |
| @itemx h |
| You can use @code{help} (abbreviated @code{h}) with no arguments to |
| display a short list of named classes of commands: |
| |
| @smallexample |
| (@value{GDBP}) help |
| List of classes of commands: |
| |
| aliases -- Aliases of other commands |
| breakpoints -- Making program stop at certain points |
| data -- Examining data |
| files -- Specifying and examining files |
| internals -- Maintenance commands |
| obscure -- Obscure features |
| running -- Running the program |
| stack -- Examining the stack |
| status -- Status inquiries |
| support -- Support facilities |
| tracepoints -- Tracing of program execution without |
| stopping the program |
| user-defined -- User-defined commands |
| |
| Type "help" followed by a class name for a list of |
| commands in that class. |
| Type "help" followed by command name for full |
| documentation. |
| Command name abbreviations are allowed if unambiguous. |
| (@value{GDBP}) |
| @end smallexample |
| @c the above line break eliminates huge line overfull... |
| |
| @item help @var{class} |
| Using one of the general help classes as an argument, you can get a |
| list of the individual commands in that class. For example, here is the |
| help display for the class @code{status}: |
| |
| @smallexample |
| (@value{GDBP}) help status |
| Status inquiries. |
| |
| List of commands: |
| |
| @c Line break in "show" line falsifies real output, but needed |
| @c to fit in smallbook page size. |
| info -- Generic command for showing things |
| about the program being debugged |
| show -- Generic command for showing things |
| about the debugger |
| |
| Type "help" followed by command name for full |
| documentation. |
| Command name abbreviations are allowed if unambiguous. |
| (@value{GDBP}) |
| @end smallexample |
| |
| @item help @var{command} |
| With a command name as @code{help} argument, @value{GDBN} displays a |
| short paragraph on how to use that command. |
| |
| @kindex apropos |
| @item apropos @var{args} |
| The @code{apropos} command searches through all of the @value{GDBN} |
| commands, and their documentation, for the regular expression specified in |
| @var{args}. It prints out all matches found. For example: |
| |
| @smallexample |
| apropos alias |
| @end smallexample |
| |
| @noindent |
| results in: |
| |
| @smallexample |
| @c @group |
| alias -- Define a new command that is an alias of an existing command |
| aliases -- Aliases of other commands |
| d -- Delete some breakpoints or auto-display expressions |
| del -- Delete some breakpoints or auto-display expressions |
| delete -- Delete some breakpoints or auto-display expressions |
| @c @end group |
| @end smallexample |
| |
| @kindex complete |
| @item complete @var{args} |
| The @code{complete @var{args}} command lists all the possible completions |
| for the beginning of a command. Use @var{args} to specify the beginning of the |
| command you want completed. For example: |
| |
| @smallexample |
| complete i |
| @end smallexample |
| |
| @noindent results in: |
| |
| @smallexample |
| @group |
| if |
| ignore |
| info |
| inspect |
| @end group |
| @end smallexample |
| |
| @noindent This is intended for use by @sc{gnu} Emacs. |
| @end table |
| |
| In addition to @code{help}, you can use the @value{GDBN} commands @code{info} |
| and @code{show} to inquire about the state of your program, or the state |
| of @value{GDBN} itself. Each command supports many topics of inquiry; this |
| manual introduces each of them in the appropriate context. The listings |
| under @code{info} and under @code{show} in the Command, Variable, and |
| Function Index point to all the sub-commands. @xref{Command and Variable |
| Index}. |
| |
| @c @group |
| @table @code |
| @kindex info |
| @kindex i @r{(@code{info})} |
| @item info |
| This command (abbreviated @code{i}) is for describing the state of your |
| program. For example, you can show the arguments passed to a function |
| with @code{info args}, list the registers currently in use with @code{info |
| registers}, or list the breakpoints you have set with @code{info breakpoints}. |
| You can get a complete list of the @code{info} sub-commands with |
| @w{@code{help info}}. |
| |
| @kindex set |
| @item set |
| You can assign the result of an expression to an environment variable with |
| @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with |
| @code{set prompt $}. |
| |
| @kindex show |
| @item show |
| In contrast to @code{info}, @code{show} is for describing the state of |
| @value{GDBN} itself. |
| You can change most of the things you can @code{show}, by using the |
| related command @code{set}; for example, you can control what number |
| system is used for displays with @code{set radix}, or simply inquire |
| which is currently in use with @code{show radix}. |
| |
| @kindex info set |
| To display all the settable parameters and their current |
| values, you can use @code{show} with no arguments; you may also use |
| @code{info set}. Both commands produce the same display. |
| @c FIXME: "info set" violates the rule that "info" is for state of |
| @c FIXME...program. Ck w/ GNU: "info set" to be called something else, |
| @c FIXME...or change desc of rule---eg "state of prog and debugging session"? |
| @end table |
| @c @end group |
| |
| Here are three miscellaneous @code{show} subcommands, all of which are |
| exceptional in lacking corresponding @code{set} commands: |
| |
| @table @code |
| @kindex show version |
| @cindex @value{GDBN} version number |
| @item show version |
| Show what version of @value{GDBN} is running. You should include this |
| information in @value{GDBN} bug-reports. If multiple versions of |
| @value{GDBN} are in use at your site, you may need to determine which |
| version of @value{GDBN} you are running; as @value{GDBN} evolves, new |
| commands are introduced, and old ones may wither away. Also, many |
| system vendors ship variant versions of @value{GDBN}, and there are |
| variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well. |
| The version number is the same as the one announced when you start |
| @value{GDBN}. |
| |
| @kindex show copying |
| @kindex info copying |
| @cindex display @value{GDBN} copyright |
| @item show copying |
| @itemx info copying |
| Display information about permission for copying @value{GDBN}. |
| |
| @kindex show warranty |
| @kindex info warranty |
| @item show warranty |
| @itemx info warranty |
| Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty, |
| if your version of @value{GDBN} comes with one. |
| |
| @end table |
| |
| @node Running |
| @chapter Running Programs Under @value{GDBN} |
| |
| When you run a program under @value{GDBN}, you must first generate |
| debugging information when you compile it. |
| |
| You may start @value{GDBN} with its arguments, if any, in an environment |
| of your choice. If you are doing native debugging, you may redirect |
| your program's input and output, debug an already running process, or |
| kill a child process. |
| |
| @menu |
| * Compilation:: Compiling for debugging |
| * Starting:: Starting your program |
| * Arguments:: Your program's arguments |
| * Environment:: Your program's environment |
| |
| * Working Directory:: Your program's working directory |
| * Input/Output:: Your program's input and output |
| * Attach:: Debugging an already-running process |
| * Kill Process:: Killing the child process |
| |
| * Inferiors and Programs:: Debugging multiple inferiors and programs |
| * Threads:: Debugging programs with multiple threads |
| * Forks:: Debugging forks |
| * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later |
| @end menu |
| |
| @node Compilation |
| @section Compiling for Debugging |
| |
| In order to debug a program effectively, you need to generate |
| debugging information when you compile it. This debugging information |
| is stored in the object file; it describes the data type of each |
| variable or function and the correspondence between source line numbers |
| and addresses in the executable code. |
| |
| To request debugging information, specify the @samp{-g} option when you run |
| the compiler. |
| |
| Programs that are to be shipped to your customers are compiled with |
| optimizations, using the @samp{-O} compiler option. However, some |
| compilers are unable to handle the @samp{-g} and @samp{-O} options |
| together. Using those compilers, you cannot generate optimized |
| executables containing debugging information. |
| |
| @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or |
| without @samp{-O}, making it possible to debug optimized code. We |
| recommend that you @emph{always} use @samp{-g} whenever you compile a |
| program. You may think your program is correct, but there is no sense |
| in pushing your luck. For more information, see @ref{Optimized Code}. |
| |
| Older versions of the @sc{gnu} C compiler permitted a variant option |
| @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this |
| format; if your @sc{gnu} C compiler has this option, do not use it. |
| |
| @value{GDBN} knows about preprocessor macros and can show you their |
| expansion (@pxref{Macros}). Most compilers do not include information |
| about preprocessor macros in the debugging information if you specify |
| the @option{-g} flag alone. Version 3.1 and later of @value{NGCC}, |
| the @sc{gnu} C compiler, provides macro information if you are using |
| the DWARF debugging format, and specify the option @option{-g3}. |
| |
| @xref{Debugging Options,,Options for Debugging Your Program or GCC, |
| gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more |
| information on @value{NGCC} options affecting debug information. |
| |
| You will have the best debugging experience if you use the latest |
| version of the DWARF debugging format that your compiler supports. |
| DWARF is currently the most expressive and best supported debugging |
| format in @value{GDBN}. |
| |
| @need 2000 |
| @node Starting |
| @section Starting your Program |
| @cindex starting |
| @cindex running |
| |
| @table @code |
| @kindex run |
| @kindex r @r{(@code{run})} |
| @item run |
| @itemx r |
| Use the @code{run} command to start your program under @value{GDBN}. |
| You must first specify the program name (except on VxWorks) with an |
| argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of |
| @value{GDBN}}), or by using the @code{file} or @code{exec-file} command |
| (@pxref{Files, ,Commands to Specify Files}). |
| |
| @end table |
| |
| If you are running your program in an execution environment that |
| supports processes, @code{run} creates an inferior process and makes |
| that process run your program. In some environments without processes, |
| @code{run} jumps to the start of your program. Other targets, |
| like @samp{remote}, are always running. If you get an error |
| message like this one: |
| |
| @smallexample |
| The "remote" target does not support "run". |
| Try "help target" or "continue". |
| @end smallexample |
| |
| @noindent |
| then use @code{continue} to run your program. You may need @code{load} |
| first (@pxref{load}). |
| |
| The execution of a program is affected by certain information it |
| receives from its superior. @value{GDBN} provides ways to specify this |
| information, which you must do @emph{before} starting your program. (You |
| can change it after starting your program, but such changes only affect |
| your program the next time you start it.) This information may be |
| divided into four categories: |
| |
| @table @asis |
| @item The @emph{arguments.} |
| Specify the arguments to give your program as the arguments of the |
| @code{run} command. If a shell is available on your target, the shell |
| is used to pass the arguments, so that you may use normal conventions |
| (such as wildcard expansion or variable substitution) in describing |
| the arguments. |
| In Unix systems, you can control which shell is used with the |
| @code{SHELL} environment variable. |
| @xref{Arguments, ,Your Program's Arguments}. |
| |
| @item The @emph{environment.} |
| Your program normally inherits its environment from @value{GDBN}, but you can |
| use the @value{GDBN} commands @code{set environment} and @code{unset |
| environment} to change parts of the environment that affect |
| your program. @xref{Environment, ,Your Program's Environment}. |
| |
| @item The @emph{working directory.} |
| Your program inherits its working directory from @value{GDBN}. You can set |
| the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}. |
| @xref{Working Directory, ,Your Program's Working Directory}. |
| |
| @item The @emph{standard input and output.} |
| Your program normally uses the same device for standard input and |
| standard output as @value{GDBN} is using. You can redirect input and output |
| in the @code{run} command line, or you can use the @code{tty} command to |
| set a different device for your program. |
| @xref{Input/Output, ,Your Program's Input and Output}. |
| |
| @cindex pipes |
| @emph{Warning:} While input and output redirection work, you cannot use |
| pipes to pass the output of the program you are debugging to another |
| program; if you attempt this, @value{GDBN} is likely to wind up debugging the |
| wrong program. |
| @end table |
| |
| When you issue the @code{run} command, your program begins to execute |
| immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion |
| of how to arrange for your program to stop. Once your program has |
| stopped, you may call functions in your program, using the @code{print} |
| or @code{call} commands. @xref{Data, ,Examining Data}. |
| |
| If the modification time of your symbol file has changed since the last |
| time @value{GDBN} read its symbols, @value{GDBN} discards its symbol |
| table, and reads it again. When it does this, @value{GDBN} tries to retain |
| your current breakpoints. |
| |
| @table @code |
| @kindex start |
| @item start |
| @cindex run to main procedure |
| The name of the main procedure can vary from language to language. |
| With C or C@t{++}, the main procedure name is always @code{main}, but |
| other languages such as Ada do not require a specific name for their |
| main procedure. The debugger provides a convenient way to start the |
| execution of the program and to stop at the beginning of the main |
| procedure, depending on the language used. |
| |
| The @samp{start} command does the equivalent of setting a temporary |
| breakpoint at the beginning of the main procedure and then invoking |
| the @samp{run} command. |
| |
| @cindex elaboration phase |
| Some programs contain an @dfn{elaboration} phase where some startup code is |
| executed before the main procedure is called. This depends on the |
| languages used to write your program. In C@t{++}, for instance, |
| constructors for static and global objects are executed before |
| @code{main} is called. It is therefore possible that the debugger stops |
| before reaching the main procedure. However, the temporary breakpoint |
| will remain to halt execution. |
| |
| Specify the arguments to give to your program as arguments to the |
| @samp{start} command. These arguments will be given verbatim to the |
| underlying @samp{run} command. Note that the same arguments will be |
| reused if no argument is provided during subsequent calls to |
| @samp{start} or @samp{run}. |
| |
| It is sometimes necessary to debug the program during elaboration. In |
| these cases, using the @code{start} command would stop the execution of |
| your program too late, as the program would have already completed the |
| elaboration phase. Under these circumstances, insert breakpoints in your |
| elaboration code before running your program. |
| |
| @kindex set exec-wrapper |
| @item set exec-wrapper @var{wrapper} |
| @itemx show exec-wrapper |
| @itemx unset exec-wrapper |
| When @samp{exec-wrapper} is set, the specified wrapper is used to |
| launch programs for debugging. @value{GDBN} starts your program |
| with a shell command of the form @kbd{exec @var{wrapper} |
| @var{program}}. Quoting is added to @var{program} and its |
| arguments, but not to @var{wrapper}, so you should add quotes if |
| appropriate for your shell. The wrapper runs until it executes |
| your program, and then @value{GDBN} takes control. |
| |
| You can use any program that eventually calls @code{execve} with |
| its arguments as a wrapper. Several standard Unix utilities do |
| this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending |
| with @code{exec "$@@"} will also work. |
| |
| For example, you can use @code{env} to pass an environment variable to |
| the debugged program, without setting the variable in your shell's |
| environment: |
| |
| @smallexample |
| (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so' |
| (@value{GDBP}) run |
| @end smallexample |
| |
| This command is available when debugging locally on most targets, excluding |
| @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino. |
| |
| @kindex set disable-randomization |
| @item set disable-randomization |
| @itemx set disable-randomization on |
| This option (enabled by default in @value{GDBN}) will turn off the native |
| randomization of the virtual address space of the started program. This option |
| is useful for multiple debugging sessions to make the execution better |
| reproducible and memory addresses reusable across debugging sessions. |
| |
| This feature is implemented only on certain targets, including @sc{gnu}/Linux. |
| On @sc{gnu}/Linux you can get the same behavior using |
| |
| @smallexample |
| (@value{GDBP}) set exec-wrapper setarch `uname -m` -R |
| @end smallexample |
| |
| @item set disable-randomization off |
| Leave the behavior of the started executable unchanged. Some bugs rear their |
| ugly heads only when the program is loaded at certain addresses. If your bug |
| disappears when you run the program under @value{GDBN}, that might be because |
| @value{GDBN} by default disables the address randomization on platforms, such |
| as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set |
| disable-randomization off} to try to reproduce such elusive bugs. |
| |
| On targets where it is available, virtual address space randomization |
| protects the programs against certain kinds of security attacks. In these |
| cases the attacker needs to know the exact location of a concrete executable |
| code. Randomizing its location makes it impossible to inject jumps misusing |
| a code at its expected addresses. |
| |
| Prelinking shared libraries provides a startup performance advantage but it |
| makes addresses in these libraries predictable for privileged processes by |
| having just unprivileged access at the target system. Reading the shared |
| library binary gives enough information for assembling the malicious code |
| misusing it. Still even a prelinked shared library can get loaded at a new |
| random address just requiring the regular relocation process during the |
| startup. Shared libraries not already prelinked are always loaded at |
| a randomly chosen address. |
| |
| Position independent executables (PIE) contain position independent code |
| similar to the shared libraries and therefore such executables get loaded at |
| a randomly chosen address upon startup. PIE executables always load even |
| already prelinked shared libraries at a random address. You can build such |
| executable using @command{gcc -fPIE -pie}. |
| |
| Heap (malloc storage), stack and custom mmap areas are always placed randomly |
| (as long as the randomization is enabled). |
| |
| @item show disable-randomization |
| Show the current setting of the explicit disable of the native randomization of |
| the virtual address space of the started program. |
| |
| @end table |
| |
| @node Arguments |
| @section Your Program's Arguments |
| |
| @cindex arguments (to your program) |
| The arguments to your program can be specified by the arguments of the |
| @code{run} command. |
| They are passed to a shell, which expands wildcard characters and |
| performs redirection of I/O, and thence to your program. Your |
| @code{SHELL} environment variable (if it exists) specifies what shell |
| @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses |
| the default shell (@file{/bin/sh} on Unix). |
| |
| On non-Unix systems, the program is usually invoked directly by |
| @value{GDBN}, which emulates I/O redirection via the appropriate system |
| calls, and the wildcard characters are expanded by the startup code of |
| the program, not by the shell. |
| |
| @code{run} with no arguments uses the same arguments used by the previous |
| @code{run}, or those set by the @code{set args} command. |
| |
| @table @code |
| @kindex set args |
| @item set args |
| Specify the arguments to be used the next time your program is run. If |
| @code{set args} has no arguments, @code{run} executes your program |
| with no arguments. Once you have run your program with arguments, |
| using @code{set args} before the next @code{run} is the only way to run |
| it again without arguments. |
| |
| @kindex show args |
| @item show args |
| Show the arguments to give your program when it is started. |
| @end table |
| |
| @node Environment |
| @section Your Program's Environment |
| |
| @cindex environment (of your program) |
| The @dfn{environment} consists of a set of environment variables and |
| their values. Environment variables conventionally record such things as |
| your user name, your home directory, your terminal type, and your search |
| path for programs to run. Usually you set up environment variables with |
| the shell and they are inherited by all the other programs you run. When |
| debugging, it can be useful to try running your program with a modified |
| environment without having to start @value{GDBN} over again. |
| |
| @table @code |
| @kindex path |
| @item path @var{directory} |
| Add @var{directory} to the front of the @code{PATH} environment variable |
| (the search path for executables) that will be passed to your program. |
| The value of @code{PATH} used by @value{GDBN} does not change. |
| You may specify several directory names, separated by whitespace or by a |
| system-dependent separator character (@samp{:} on Unix, @samp{;} on |
| MS-DOS and MS-Windows). If @var{directory} is already in the path, it |
| is moved to the front, so it is searched sooner. |
| |
| You can use the string @samp{$cwd} to refer to whatever is the current |
| working directory at the time @value{GDBN} searches the path. If you |
| use @samp{.} instead, it refers to the directory where you executed the |
| @code{path} command. @value{GDBN} replaces @samp{.} in the |
| @var{directory} argument (with the current path) before adding |
| @var{directory} to the search path. |
| @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to |
| @c document that, since repeating it would be a no-op. |
| |
| @kindex show paths |
| @item show paths |
| Display the list of search paths for executables (the @code{PATH} |
| environment variable). |
| |
| @kindex show environment |
| @item show environment @r{[}@var{varname}@r{]} |
| Print the value of environment variable @var{varname} to be given to |
| your program when it starts. If you do not supply @var{varname}, |
| print the names and values of all environment variables to be given to |
| your program. You can abbreviate @code{environment} as @code{env}. |
| |
| @kindex set environment |
| @item set environment @var{varname} @r{[}=@var{value}@r{]} |
| Set environment variable @var{varname} to @var{value}. The value |
| changes for your program only, not for @value{GDBN} itself. @var{value} may |
| be any string; the values of environment variables are just strings, and |
| any interpretation is supplied by your program itself. The @var{value} |
| parameter is optional; if it is eliminated, the variable is set to a |
| null value. |
| @c "any string" here does not include leading, trailing |
| @c blanks. Gnu asks: does anyone care? |
| |
| For example, this command: |
| |
| @smallexample |
| set env USER = foo |
| @end smallexample |
| |
| @noindent |
| tells the debugged program, when subsequently run, that its user is named |
| @samp{foo}. (The spaces around @samp{=} are used for clarity here; they |
| are not actually required.) |
| |
| @kindex unset environment |
| @item unset environment @var{varname} |
| Remove variable @var{varname} from the environment to be passed to your |
| program. This is different from @samp{set env @var{varname} =}; |
| @code{unset environment} removes the variable from the environment, |
| rather than assigning it an empty value. |
| @end table |
| |
| @emph{Warning:} On Unix systems, @value{GDBN} runs your program using |
| the shell indicated |
| by your @code{SHELL} environment variable if it exists (or |
| @code{/bin/sh} if not). If your @code{SHELL} variable names a shell |
| that runs an initialization file---such as @file{.cshrc} for C-shell, or |
| @file{.bashrc} for BASH---any variables you set in that file affect |
| your program. You may wish to move setting of environment variables to |
| files that are only run when you sign on, such as @file{.login} or |
| @file{.profile}. |
| |
| @node Working Directory |
| @section Your Program's Working Directory |
| |
| @cindex working directory (of your program) |
| Each time you start your program with @code{run}, it inherits its |
| working directory from the current working directory of @value{GDBN}. |
| The @value{GDBN} working directory is initially whatever it inherited |
| from its parent process (typically the shell), but you can specify a new |
| working directory in @value{GDBN} with the @code{cd} command. |
| |
| The @value{GDBN} working directory also serves as a default for the commands |
| that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to |
| Specify Files}. |
| |
| @table @code |
| @kindex cd |
| @cindex change working directory |
| @item cd @var{directory} |
| Set the @value{GDBN} working directory to @var{directory}. |
| |
| @kindex pwd |
| @item pwd |
| Print the @value{GDBN} working directory. |
| @end table |
| |
| It is generally impossible to find the current working directory of |
| the process being debugged (since a program can change its directory |
| during its run). If you work on a system where @value{GDBN} is |
| configured with the @file{/proc} support, you can use the @code{info |
| proc} command (@pxref{SVR4 Process Information}) to find out the |
| current working directory of the debuggee. |
| |
| @node Input/Output |
| @section Your Program's Input and Output |
| |
| @cindex redirection |
| @cindex i/o |
| @cindex terminal |
| By default, the program you run under @value{GDBN} does input and output to |
| the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal |
| to its own terminal modes to interact with you, but it records the terminal |
| modes your program was using and switches back to them when you continue |
| running your program. |
| |
| @table @code |
| @kindex info terminal |
| @item info terminal |
| Displays information recorded by @value{GDBN} about the terminal modes your |
| program is using. |
| @end table |
| |
| You can redirect your program's input and/or output using shell |
| redirection with the @code{run} command. For example, |
| |
| @smallexample |
| run > outfile |
| @end smallexample |
| |
| @noindent |
| starts your program, diverting its output to the file @file{outfile}. |
| |
| @kindex tty |
| @cindex controlling terminal |
| Another way to specify where your program should do input and output is |
| with the @code{tty} command. This command accepts a file name as |
| argument, and causes this file to be the default for future @code{run} |
| commands. It also resets the controlling terminal for the child |
| process, for future @code{run} commands. For example, |
| |
| @smallexample |
| tty /dev/ttyb |
| @end smallexample |
| |
| @noindent |
| directs that processes started with subsequent @code{run} commands |
| default to do input and output on the terminal @file{/dev/ttyb} and have |
| that as their controlling terminal. |
| |
| An explicit redirection in @code{run} overrides the @code{tty} command's |
| effect on the input/output device, but not its effect on the controlling |
| terminal. |
| |
| When you use the @code{tty} command or redirect input in the @code{run} |
| command, only the input @emph{for your program} is affected. The input |
| for @value{GDBN} still comes from your terminal. @code{tty} is an alias |
| for @code{set inferior-tty}. |
| |
| @cindex inferior tty |
| @cindex set inferior controlling terminal |
| You can use the @code{show inferior-tty} command to tell @value{GDBN} to |
| display the name of the terminal that will be used for future runs of your |
| program. |
| |
| @table @code |
| @item set inferior-tty /dev/ttyb |
| @kindex set inferior-tty |
| Set the tty for the program being debugged to /dev/ttyb. |
| |
| @item show inferior-tty |
| @kindex show inferior-tty |
| Show the current tty for the program being debugged. |
| @end table |
| |
| @node Attach |
| @section Debugging an Already-running Process |
| @kindex attach |
| @cindex attach |
| |
| @table @code |
| @item attach @var{process-id} |
| This command attaches to a running process---one that was started |
| outside @value{GDBN}. (@code{info files} shows your active |
| targets.) The command takes as argument a process ID. The usual way to |
| find out the @var{process-id} of a Unix process is with the @code{ps} utility, |
| or with the @samp{jobs -l} shell command. |
| |
| @code{attach} does not repeat if you press @key{RET} a second time after |
| executing the command. |
| @end table |
| |
| To use @code{attach}, your program must be running in an environment |
| which supports processes; for example, @code{attach} does not work for |
| programs on bare-board targets that lack an operating system. You must |
| also have permission to send the process a signal. |
| |
| When you use @code{attach}, the debugger finds the program running in |
| the process first by looking in the current working directory, then (if |
| the program is not found) by using the source file search path |
| (@pxref{Source Path, ,Specifying Source Directories}). You can also use |
| the @code{file} command to load the program. @xref{Files, ,Commands to |
| Specify Files}. |
| |
| The first thing @value{GDBN} does after arranging to debug the specified |
| process is to stop it. You can examine and modify an attached process |
| with all the @value{GDBN} commands that are ordinarily available when |
| you start processes with @code{run}. You can insert breakpoints; you |
| can step and continue; you can modify storage. If you would rather the |
| process continue running, you may use the @code{continue} command after |
| attaching @value{GDBN} to the process. |
| |
| @table @code |
| @kindex detach |
| @item detach |
| When you have finished debugging the attached process, you can use the |
| @code{detach} command to release it from @value{GDBN} control. Detaching |
| the process continues its execution. After the @code{detach} command, |
| that process and @value{GDBN} become completely independent once more, and you |
| are ready to @code{attach} another process or start one with @code{run}. |
| @code{detach} does not repeat if you press @key{RET} again after |
| executing the command. |
| @end table |
| |
| If you exit @value{GDBN} while you have an attached process, you detach |
| that process. If you use the @code{run} command, you kill that process. |
| By default, @value{GDBN} asks for confirmation if you try to do either of these |
| things; you can control whether or not you need to confirm by using the |
| @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and |
| Messages}). |
| |
| @node Kill Process |
| @section Killing the Child Process |
| |
| @table @code |
| @kindex kill |
| @item kill |
| Kill the child process in which your program is running under @value{GDBN}. |
| @end table |
| |
| This command is useful if you wish to debug a core dump instead of a |
| running process. @value{GDBN} ignores any core dump file while your program |
| is running. |
| |
| On some operating systems, a program cannot be executed outside @value{GDBN} |
| while you have breakpoints set on it inside @value{GDBN}. You can use the |
| @code{kill} command in this situation to permit running your program |
| outside the debugger. |
| |
| The @code{kill} command is also useful if you wish to recompile and |
| relink your program, since on many systems it is impossible to modify an |
| executable file while it is running in a process. In this case, when you |
| next type @code{run}, @value{GDBN} notices that the file has changed, and |
| reads the symbol table again (while trying to preserve your current |
| breakpoint settings). |
| |
| @node Inferiors and Programs |
| @section Debugging Multiple Inferiors and Programs |
| |
| @value{GDBN} lets you run and debug multiple programs in a single |
| session. In addition, @value{GDBN} on some systems may let you run |
| several programs simultaneously (otherwise you have to exit from one |
| before starting another). In the most general case, you can have |
| multiple threads of execution in each of multiple processes, launched |
| from multiple executables. |
| |
| @cindex inferior |
| @value{GDBN} represents the state of each program execution with an |
| object called an @dfn{inferior}. An inferior typically corresponds to |
| a process, but is more general and applies also to targets that do not |
| have processes. Inferiors may be created before a process runs, and |
| may be retained after a process exits. Inferiors have unique |
| identifiers that are different from process ids. Usually each |
| inferior will also have its own distinct address space, although some |
| embedded targets may have several inferiors running in different parts |
| of a single address space. Each inferior may in turn have multiple |
| threads running in it. |
| |
| To find out what inferiors exist at any moment, use @w{@code{info |
| inferiors}}: |
| |
| @table @code |
| @kindex info inferiors |
| @item info inferiors |
| Print a list of all inferiors currently being managed by @value{GDBN}. |
| |
| @value{GDBN} displays for each inferior (in this order): |
| |
| @enumerate |
| @item |
| the inferior number assigned by @value{GDBN} |
| |
| @item |
| the target system's inferior identifier |
| |
| @item |
| the name of the executable the inferior is running. |
| |
| @end enumerate |
| |
| @noindent |
| An asterisk @samp{*} preceding the @value{GDBN} inferior number |
| indicates the current inferior. |
| |
| For example, |
| @end table |
| @c end table here to get a little more width for example |
| |
| @smallexample |
| (@value{GDBP}) info inferiors |
| Num Description Executable |
| 2 process 2307 hello |
| * 1 process 3401 goodbye |
| @end smallexample |
| |
| To switch focus between inferiors, use the @code{inferior} command: |
| |
| @table @code |
| @kindex inferior @var{infno} |
| @item inferior @var{infno} |
| Make inferior number @var{infno} the current inferior. The argument |
| @var{infno} is the inferior number assigned by @value{GDBN}, as shown |
| in the first field of the @samp{info inferiors} display. |
| @end table |
| |
| |
| You can get multiple executables into a debugging session via the |
| @code{add-inferior} and @w{@code{clone-inferior}} commands. On some |
| systems @value{GDBN} can add inferiors to the debug session |
| automatically by following calls to @code{fork} and @code{exec}. To |
| remove inferiors from the debugging session use the |
| @w{@code{remove-inferiors}} command. |
| |
| @table @code |
| @kindex add-inferior |
| @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] |
| Adds @var{n} inferiors to be run using @var{executable} as the |
| executable. @var{n} defaults to 1. If no executable is specified, |
| the inferiors begins empty, with no program. You can still assign or |
| change the program assigned to the inferior at any time by using the |
| @code{file} command with the executable name as its argument. |
| |
| @kindex clone-inferior |
| @item clone-inferior [ -copies @var{n} ] [ @var{infno} ] |
| Adds @var{n} inferiors ready to execute the same program as inferior |
| @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the |
| number of the current inferior. This is a convenient command when you |
| want to run another instance of the inferior you are debugging. |
| |
| @smallexample |
| (@value{GDBP}) info inferiors |
| Num Description Executable |
| * 1 process 29964 helloworld |
| (@value{GDBP}) clone-inferior |
| Added inferior 2. |
| 1 inferiors added. |
| (@value{GDBP}) info inferiors |
| Num Description Executable |
| 2 <null> helloworld |
| * 1 process 29964 helloworld |
| @end smallexample |
| |
| You can now simply switch focus to inferior 2 and run it. |
| |
| @kindex remove-inferiors |
| @item remove-inferiors @var{infno}@dots{} |
| Removes the inferior or inferiors @var{infno}@dots{}. It is not |
| possible to remove an inferior that is running with this command. For |
| those, use the @code{kill} or @code{detach} command first. |
| |
| @end table |
| |
| To quit debugging one of the running inferiors that is not the current |
| inferior, you can either detach from it by using the @w{@code{detach |
| inferior}} command (allowing it to run independently), or kill it |
| using the @w{@code{kill inferiors}} command: |
| |
| @table @code |
| @kindex detach inferiors @var{infno}@dots{} |
| @item detach inferior @var{infno}@dots{} |
| Detach from the inferior or inferiors identified by @value{GDBN} |
| inferior number(s) @var{infno}@dots{}. Note that the inferior's entry |
| still stays on the list of inferiors shown by @code{info inferiors}, |
| but its Description will show @samp{<null>}. |
| |
| @kindex kill inferiors @var{infno}@dots{} |
| @item kill inferiors @var{infno}@dots{} |
| Kill the inferior or inferiors identified by @value{GDBN} inferior |
| number(s) @var{infno}@dots{}. Note that the inferior's entry still |
| stays on the list of inferiors shown by @code{info inferiors}, but its |
| Description will show @samp{<null>}. |
| @end table |
| |
| After the successful completion of a command such as @code{detach}, |
| @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after |
| a normal process exit, the inferior is still valid and listed with |
| @code{info inferiors}, ready to be restarted. |
| |
| |
| To be notified when inferiors are started or exit under @value{GDBN}'s |
| control use @w{@code{set print inferior-events}}: |
| |
| @table @code |
| @kindex set print inferior-events |
| @cindex print messages on inferior start and exit |
| @item set print inferior-events |
| @itemx set print inferior-events on |
| @itemx set print inferior-events off |
| The @code{set print inferior-events} command allows you to enable or |
| disable printing of messages when @value{GDBN} notices that new |
| inferiors have started or that inferiors have exited or have been |
| detached. By default, these messages will not be printed. |
| |
| @kindex show print inferior-events |
| @item show print inferior-events |
| Show whether messages will be printed when @value{GDBN} detects that |
| inferiors have started, exited or have been detached. |
| @end table |
| |
| Many commands will work the same with multiple programs as with a |
| single program: e.g., @code{print myglobal} will simply display the |
| value of @code{myglobal} in the current inferior. |
| |
| |
| Occasionaly, when debugging @value{GDBN} itself, it may be useful to |
| get more info about the relationship of inferiors, programs, address |
| spaces in a debug session. You can do that with the @w{@code{maint |
| info program-spaces}} command. |
| |
| @table @code |
| @kindex maint info program-spaces |
| @item maint info program-spaces |
| Print a list of all program spaces currently being managed by |
| @value{GDBN}. |
| |
| @value{GDBN} displays for each program space (in this order): |
| |
| @enumerate |
| @item |
| the program space number assigned by @value{GDBN} |
| |
| @item |
| the name of the executable loaded into the program space, with e.g., |
| the @code{file} command. |
| |
| @end enumerate |
| |
| @noindent |
| An asterisk @samp{*} preceding the @value{GDBN} program space number |
| indicates the current program space. |
| |
| In addition, below each program space line, @value{GDBN} prints extra |
| information that isn't suitable to display in tabular form. For |
| example, the list of inferiors bound to the program space. |
| |
| @smallexample |
| (@value{GDBP}) maint info program-spaces |
| Id Executable |
| 2 goodbye |
| Bound inferiors: ID 1 (process 21561) |
| * 1 hello |
| @end smallexample |
| |
| Here we can see that no inferior is running the program @code{hello}, |
| while @code{process 21561} is running the program @code{goodbye}. On |
| some targets, it is possible that multiple inferiors are bound to the |
| same program space. The most common example is that of debugging both |
| the parent and child processes of a @code{vfork} call. For example, |
| |
| @smallexample |
| (@value{GDBP}) maint info program-spaces |
| Id Executable |
| * 1 vfork-test |
| Bound inferiors: ID 2 (process 18050), ID 1 (process 18045) |
| @end smallexample |
| |
| Here, both inferior 2 and inferior 1 are running in the same program |
| space as a result of inferior 1 having executed a @code{vfork} call. |
| @end table |
| |
| @node Threads |
| @section Debugging Programs with Multiple Threads |
| |
| @cindex threads of execution |
| @cindex multiple threads |
| @cindex switching threads |
| In some operating systems, such as HP-UX and Solaris, a single program |
| may have more than one @dfn{thread} of execution. The precise semantics |
| of threads differ from one operating system to another, but in general |
| the threads of a single program are akin to multiple processes---except |
| that they share one address space (that is, they can all examine and |
| modify the same variables). On the other hand, each thread has its own |
| registers and execution stack, and perhaps private memory. |
| |
| @value{GDBN} provides these facilities for debugging multi-thread |
| programs: |
| |
| @itemize @bullet |
| @item automatic notification of new threads |
| @item @samp{thread @var{threadno}}, a command to switch among threads |
| @item @samp{info threads}, a command to inquire about existing threads |
| @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}}, |
| a command to apply a command to a list of threads |
| @item thread-specific breakpoints |
| @item @samp{set print thread-events}, which controls printing of |
| messages on thread start and exit. |
| @item @samp{set libthread-db-search-path @var{path}}, which lets |
| the user specify which @code{libthread_db} to use if the default choice |
| isn't compatible with the program. |
| @end itemize |
| |
| @quotation |
| @emph{Warning:} These facilities are not yet available on every |
| @value{GDBN} configuration where the operating system supports threads. |
| If your @value{GDBN} does not support threads, these commands have no |
| effect. For example, a system without thread support shows no output |
| from @samp{info threads}, and always rejects the @code{thread} command, |
| like this: |
| |
| @smallexample |
| (@value{GDBP}) info threads |
| (@value{GDBP}) thread 1 |
| Thread ID 1 not known. Use the "info threads" command to |
| see the IDs of currently known threads. |
| @end smallexample |
| @c FIXME to implementors: how hard would it be to say "sorry, this GDB |
| @c doesn't support threads"? |
| @end quotation |
| |
| @cindex focus of debugging |
| @cindex current thread |
| The @value{GDBN} thread debugging facility allows you to observe all |
| threads while your program runs---but whenever @value{GDBN} takes |
| control, one thread in particular is always the focus of debugging. |
| This thread is called the @dfn{current thread}. Debugging commands show |
| program information from the perspective of the current thread. |
| |
| @cindex @code{New} @var{systag} message |
| @cindex thread identifier (system) |
| @c FIXME-implementors!! It would be more helpful if the [New...] message |
| @c included GDB's numeric thread handle, so you could just go to that |
| @c thread without first checking `info threads'. |
| Whenever @value{GDBN} detects a new thread in your program, it displays |
| the target system's identification for the thread with a message in the |
| form @samp{[New @var{systag}]}. @var{systag} is a thread identifier |
| whose form varies depending on the particular system. For example, on |
| @sc{gnu}/Linux, you might see |
| |
| @smallexample |
| [New Thread 0x41e02940 (LWP 25582)] |
| @end smallexample |
| |
| @noindent |
| when @value{GDBN} notices a new thread. In contrast, on an SGI system, |
| the @var{systag} is simply something like @samp{process 368}, with no |
| further qualifier. |
| |
| @c FIXME!! (1) Does the [New...] message appear even for the very first |
| @c thread of a program, or does it only appear for the |
| @c second---i.e.@: when it becomes obvious we have a multithread |
| @c program? |
| @c (2) *Is* there necessarily a first thread always? Or do some |
| @c multithread systems permit starting a program with multiple |
| @c threads ab initio? |
| |
| @cindex thread number |
| @cindex thread identifier (GDB) |
| For debugging purposes, @value{GDBN} associates its own thread |
| number---always a single integer---with each thread in your program. |
| |
| @table @code |
| @kindex info threads |
| @item info threads @r{[}@var{id}@dots{}@r{]} |
| Display a summary of all threads currently in your program. Optional |
| argument @var{id}@dots{} is one or more thread ids separated by spaces, and |
| means to print information only about the specified thread or threads. |
| @value{GDBN} displays for each thread (in this order): |
| |
| @enumerate |
| @item |
| the thread number assigned by @value{GDBN} |
| |
| @item |
| the target system's thread identifier (@var{systag}) |
| |
| @item |
| the thread's name, if one is known. A thread can either be named by |
| the user (see @code{thread name}, below), or, in some cases, by the |
| program itself. |
| |
| @item |
| the current stack frame summary for that thread |
| @end enumerate |
| |
| @noindent |
| An asterisk @samp{*} to the left of the @value{GDBN} thread number |
| indicates the current thread. |
| |
| For example, |
| @end table |
| @c end table here to get a little more width for example |
| |
| @smallexample |
| (@value{GDBP}) info threads |
| Id Target Id Frame |
| 3 process 35 thread 27 0x34e5 in sigpause () |
| 2 process 35 thread 23 0x34e5 in sigpause () |
| * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8) |
| at threadtest.c:68 |
| @end smallexample |
| |
| On Solaris, you can display more information about user threads with a |
| Solaris-specific command: |
| |
| @table @code |
| @item maint info sol-threads |
| @kindex maint info sol-threads |
| @cindex thread info (Solaris) |
| Display info on Solaris user threads. |
| @end table |
| |
| @table @code |
| @kindex thread @var{threadno} |
| @item thread @var{threadno} |
| Make thread number @var{threadno} the current thread. The command |
| argument @var{threadno} is the internal @value{GDBN} thread number, as |
| shown in the first field of the @samp{info threads} display. |
| @value{GDBN} responds by displaying the system identifier of the thread |
| you selected, and its current stack frame summary: |
| |
| @smallexample |
| (@value{GDBP}) thread 2 |
| [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))] |
| #0 some_function (ignore=0x0) at example.c:8 |
| 8 printf ("hello\n"); |
| @end smallexample |
| |
| @noindent |
| As with the @samp{[New @dots{}]} message, the form of the text after |
| @samp{Switching to} depends on your system's conventions for identifying |
| threads. |
| |
| @vindex $_thread@r{, convenience variable} |
| The debugger convenience variable @samp{$_thread} contains the number |
| of the current thread. You may find this useful in writing breakpoint |
| conditional expressions, command scripts, and so forth. See |
| @xref{Convenience Vars,, Convenience Variables}, for general |
| information on convenience variables. |
| |
| @kindex thread apply |
| @cindex apply command to several threads |
| @item thread apply [@var{threadno} | all] @var{command} |
| The @code{thread apply} command allows you to apply the named |
| @var{command} to one or more threads. Specify the numbers of the |
| threads that you want affected with the command argument |
| @var{threadno}. It can be a single thread number, one of the numbers |
| shown in the first field of the @samp{info threads} display; or it |
| could be a range of thread numbers, as in @code{2-4}. To apply a |
| command to all threads, type @kbd{thread apply all @var{command}}. |
| |
| @kindex thread name |
| @cindex name a thread |
| @item thread name [@var{name}] |
| This command assigns a name to the current thread. If no argument is |
| given, any existing user-specified name is removed. The thread name |
| appears in the @samp{info threads} display. |
| |
| On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to |
| determine the name of the thread as given by the OS. On these |
| systems, a name specified with @samp{thread name} will override the |
| system-give name, and removing the user-specified name will cause |
| @value{GDBN} to once again display the system-specified name. |
| |
| @kindex thread find |
| @cindex search for a thread |
| @item thread find [@var{regexp}] |
| Search for and display thread ids whose name or @var{systag} |
| matches the supplied regular expression. |
| |
| As well as being the complement to the @samp{thread name} command, |
| this command also allows you to identify a thread by its target |
| @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag} |
| is the LWP id. |
| |
| @smallexample |
| (@value{GDBN}) thread find 26688 |
| Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)' |
| (@value{GDBN}) info thread 4 |
| Id Target Id Frame |
| 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select () |
| @end smallexample |
| |
| @kindex set print thread-events |
| @cindex print messages on thread start and exit |
| @item set print thread-events |
| @itemx set print thread-events on |
| @itemx set print thread-events off |
| The @code{set print thread-events} command allows you to enable or |
| disable printing of messages when @value{GDBN} notices that new threads have |
| started or that threads have exited. By default, these messages will |
| be printed if detection of these events is supported by the target. |
| Note that these messages cannot be disabled on all targets. |
| |
| @kindex show print thread-events |
| @item show print thread-events |
| Show whether messages will be printed when @value{GDBN} detects that threads |
| have started and exited. |
| @end table |
| |
| @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for |
| more information about how @value{GDBN} behaves when you stop and start |
| programs with multiple threads. |
| |
| @xref{Set Watchpoints,,Setting Watchpoints}, for information about |
| watchpoints in programs with multiple threads. |
| |
| @anchor{set libthread-db-search-path} |
| @table @code |
| @kindex set libthread-db-search-path |
| @cindex search path for @code{libthread_db} |
| @item set libthread-db-search-path @r{[}@var{path}@r{]} |
| If this variable is set, @var{path} is a colon-separated list of |
| directories @value{GDBN} will use to search for @code{libthread_db}. |
| If you omit @var{path}, @samp{libthread-db-search-path} will be reset to |
| its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems). |
| Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH} |
| macro. |
| |
| On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper'' |
| @code{libthread_db} library to obtain information about threads in the |
| inferior process. @value{GDBN} will use @samp{libthread-db-search-path} |
| to find @code{libthread_db}. @value{GDBN} also consults first if inferior |
| specific thread debugging library loading is enabled |
| by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}). |
| |
| A special entry @samp{$sdir} for @samp{libthread-db-search-path} |
| refers to the default system directories that are |
| normally searched for loading shared libraries. The @samp{$sdir} entry |
| is the only kind not needing to be enabled by @samp{set auto-load libthread-db} |
| (@pxref{libthread_db.so.1 file}). |
| |
| A special entry @samp{$pdir} for @samp{libthread-db-search-path} |
| refers to the directory from which @code{libpthread} |
| was loaded in the inferior process. |
| |
| For any @code{libthread_db} library @value{GDBN} finds in above directories, |
| @value{GDBN} attempts to initialize it with the current inferior process. |
| If this initialization fails (which could happen because of a version |
| mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN} |
| will unload @code{libthread_db}, and continue with the next directory. |
| If none of @code{libthread_db} libraries initialize successfully, |
| @value{GDBN} will issue a warning and thread debugging will be disabled. |
| |
| Setting @code{libthread-db-search-path} is currently implemented |
| only on some platforms. |
| |
| @kindex show libthread-db-search-path |
| @item show libthread-db-search-path |
| Display current libthread_db search path. |
| |
| @kindex set debug libthread-db |
| @kindex show debug libthread-db |
| @cindex debugging @code{libthread_db} |
| @item set debug libthread-db |
| @itemx show debug libthread-db |
| Turns on or off display of @code{libthread_db}-related events. |
| Use @code{1} to enable, @code{0} to disable. |
| @end table |
| |
| @node Forks |
| @section Debugging Forks |
| |
| @cindex fork, debugging programs which call |
| @cindex multiple processes |
| @cindex processes, multiple |
| On most systems, @value{GDBN} has no special support for debugging |
| programs which create additional processes using the @code{fork} |
| function. When a program forks, @value{GDBN} will continue to debug the |
| parent process and the child process will run unimpeded. If you have |
| set a breakpoint in any code which the child then executes, the child |
| will get a @code{SIGTRAP} signal which (unless it catches the signal) |
| will cause it to terminate. |
| |
| However, if you want to debug the child process there is a workaround |
| which isn't too painful. Put a call to @code{sleep} in the code which |
| the child process executes after the fork. It may be useful to sleep |
| only if a certain environment variable is set, or a certain file exists, |
| so that the delay need not occur when you don't want to run @value{GDBN} |
| on the child. While the child is sleeping, use the @code{ps} program to |
| get its process ID. Then tell @value{GDBN} (a new invocation of |
| @value{GDBN} if you are also debugging the parent process) to attach to |
| the child process (@pxref{Attach}). From that point on you can debug |
| the child process just like any other process which you attached to. |
| |
| On some systems, @value{GDBN} provides support for debugging programs that |
| create additional processes using the @code{fork} or @code{vfork} functions. |
| Currently, the only platforms with this feature are HP-UX (11.x and later |
| only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later). |
| |
| By default, when a program forks, @value{GDBN} will continue to debug |
| the parent process and the child process will run unimpeded. |
| |
| If you want to follow the child process instead of the parent process, |
| use the command @w{@code{set follow-fork-mode}}. |
| |
| @table @code |
| @kindex set follow-fork-mode |
| @item set follow-fork-mode @var{mode} |
| Set the debugger response to a program call of @code{fork} or |
| @code{vfork}. A call to @code{fork} or @code{vfork} creates a new |
| process. The @var{mode} argument can be: |
| |
| @table @code |
| @item parent |
| The original process is debugged after a fork. The child process runs |
| unimpeded. This is the default. |
| |
| @item child |
| The new process is debugged after a fork. The parent process runs |
| unimpeded. |
| |
| @end table |
| |
| @kindex show follow-fork-mode |
| @item show follow-fork-mode |
| Display the current debugger response to a @code{fork} or @code{vfork} call. |
| @end table |
| |
| @cindex debugging multiple processes |
| On Linux, if you want to debug both the parent and child processes, use the |
| command @w{@code{set detach-on-fork}}. |
| |
| @table @code |
| @kindex set detach-on-fork |
| @item set detach-on-fork @var{mode} |
| Tells gdb whether to detach one of the processes after a fork, or |
| retain debugger control over them both. |
| |
| @table @code |
| @item on |
| The child process (or parent process, depending on the value of |
| @code{follow-fork-mode}) will be detached and allowed to run |
| independently. This is the default. |
| |
| @item off |
| Both processes will be held under the control of @value{GDBN}. |
| One process (child or parent, depending on the value of |
| @code{follow-fork-mode}) is debugged as usual, while the other |
| is held suspended. |
| |
| @end table |
| |
| @kindex show detach-on-fork |
| @item show detach-on-fork |
| Show whether detach-on-fork mode is on/off. |
| @end table |
| |
| If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN} |
| will retain control of all forked processes (including nested forks). |
| You can list the forked processes under the control of @value{GDBN} by |
| using the @w{@code{info inferiors}} command, and switch from one fork |
| to another by using the @code{inferior} command (@pxref{Inferiors and |
| Programs, ,Debugging Multiple Inferiors and Programs}). |
| |
| To quit debugging one of the forked processes, you can either detach |
| from it by using the @w{@code{detach inferiors}} command (allowing it |
| to run independently), or kill it using the @w{@code{kill inferiors}} |
| command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors |
| and Programs}. |
| |
| If you ask to debug a child process and a @code{vfork} is followed by an |
| @code{exec}, @value{GDBN} executes the new target up to the first |
| breakpoint in the new target. If you have a breakpoint set on |
| @code{main} in your original program, the breakpoint will also be set on |
| the child process's @code{main}. |
| |
| On some systems, when a child process is spawned by @code{vfork}, you |
| cannot debug the child or parent until an @code{exec} call completes. |
| |
| If you issue a @code{run} command to @value{GDBN} after an @code{exec} |
| call executes, the new target restarts. To restart the parent |
| process, use the @code{file} command with the parent executable name |
| as its argument. By default, after an @code{exec} call executes, |
| @value{GDBN} discards the symbols of the previous executable image. |
| You can change this behaviour with the @w{@code{set follow-exec-mode}} |
| command. |
| |
| @table @code |
| @kindex set follow-exec-mode |
| @item set follow-exec-mode @var{mode} |
| |
| Set debugger response to a program call of @code{exec}. An |
| @code{exec} call replaces the program image of a process. |
| |
| @code{follow-exec-mode} can be: |
| |
| @table @code |
| @item new |
| @value{GDBN} creates a new inferior and rebinds the process to this |
| new inferior. The program the process was running before the |
| @code{exec} call can be restarted afterwards by restarting the |
| original inferior. |
| |
| For example: |
| |
| @smallexample |
| (@value{GDBP}) info inferiors |
| (gdb) info inferior |
| Id Description Executable |
| * 1 <null> prog1 |
| (@value{GDBP}) run |
| process 12020 is executing new program: prog2 |
| Program exited normally. |
| (@value{GDBP}) info inferiors |
| Id Description Executable |
| * 2 <null> prog2 |
| 1 <null> prog1 |
| @end smallexample |
| |
| @item same |
| @value{GDBN} keeps the process bound to the same inferior. The new |
| executable image replaces the previous executable loaded in the |
| inferior. Restarting the inferior after the @code{exec} call, with |
| e.g., the @code{run} command, restarts the executable the process was |
| running after the @code{exec} call. This is the default mode. |
| |
| For example: |
| |
| @smallexample |
| (@value{GDBP}) info inferiors |
| Id Description Executable |
| * 1 <null> prog1 |
| (@value{GDBP}) run |
| process 12020 is executing new program: prog2 |
| Program exited normally. |
| (@value{GDBP}) info inferiors |
| Id Description Executable |
| * 1 <null> prog2 |
| @end smallexample |
| |
| @end table |
| @end table |
| |
| You can use the @code{catch} command to make @value{GDBN} stop whenever |
| a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set |
| Catchpoints, ,Setting Catchpoints}. |
| |
| @node Checkpoint/Restart |
| @section Setting a @emph{Bookmark} to Return to Later |
| |
| @cindex checkpoint |
| @cindex restart |
| @cindex bookmark |
| @cindex snapshot of a process |
| @cindex rewind program state |
| |
| On certain operating systems@footnote{Currently, only |
| @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a |
| program's state, called a @dfn{checkpoint}, and come back to it |
| later. |
| |
| Returning to a checkpoint effectively undoes everything that has |
| happened in the program since the @code{checkpoint} was saved. This |
| includes changes in memory, registers, and even (within some limits) |
| system state. Effectively, it is like going back in time to the |
| moment when the checkpoint was saved. |
| |
| Thus, if you're stepping thru a program and you think you're |
| getting close to the point where things go wrong, you can save |
| a checkpoint. Then, if you accidentally go too far and miss |
| the critical statement, instead of having to restart your program |
| from the beginning, you can just go back to the checkpoint and |
| start again from there. |
| |
| This can be especially useful if it takes a lot of time or |
| steps to reach the point where you think the bug occurs. |
| |
| To use the @code{checkpoint}/@code{restart} method of debugging: |
| |
| @table @code |
| @kindex checkpoint |
| @item checkpoint |
| Save a snapshot of the debugged program's current execution state. |
| The @code{checkpoint} command takes no arguments, but each checkpoint |
| is assigned a small integer id, similar to a breakpoint id. |
| |
| @kindex info checkpoints |
| @item info checkpoints |
| List the checkpoints that have been saved in the current debugging |
| session. For each checkpoint, the following information will be |
| listed: |
| |
| @table @code |
| @item Checkpoint ID |
| @item Process ID |
| @item Code Address |
| @item Source line, or label |
| @end table |
| |
| @kindex restart @var{checkpoint-id} |
| @item restart @var{checkpoint-id} |
| Restore the program state that was saved as checkpoint number |
| @var{checkpoint-id}. All program variables, registers, stack frames |
| etc.@: will be returned to the values that they had when the checkpoint |
| was saved. In essence, gdb will ``wind back the clock'' to the point |
| in time when the checkpoint was saved. |
| |
| Note that breakpoints, @value{GDBN} variables, command history etc. |
| are not affected by restoring a checkpoint. In general, a checkpoint |
| only restores things that reside in the program being debugged, not in |
| the debugger. |
| |
| @kindex delete checkpoint @var{checkpoint-id} |
| @item delete checkpoint @var{checkpoint-id} |
| Delete the previously-saved checkpoint identified by @var{checkpoint-id}. |
| |
| @end table |
| |
| Returning to a previously saved checkpoint will restore the user state |
| of the program being debugged, plus a significant subset of the system |
| (OS) state, including file pointers. It won't ``un-write'' data from |
| a file, but it will rewind the file pointer to the previous location, |
| so that the previously written data can be overwritten. For files |
| opened in read mode, the pointer will also be restored so that the |
| previously read data can be read again. |
| |
| Of course, characters that have been sent to a printer (or other |
| external device) cannot be ``snatched back'', and characters received |
| from eg.@: a serial device can be removed from internal program buffers, |
| but they cannot be ``pushed back'' into the serial pipeline, ready to |
| be received again. Similarly, the actual contents of files that have |
| been changed cannot be restored (at this time). |
| |
| However, within those constraints, you actually can ``rewind'' your |
| program to a previously saved point in time, and begin debugging it |
| again --- and you can change the course of events so as to debug a |
| different execution path this time. |
| |
| @cindex checkpoints and process id |
| Finally, there is one bit of internal program state that will be |
| different when you return to a checkpoint --- the program's process |
| id. Each checkpoint will have a unique process id (or @var{pid}), |
| and each will be different from the program's original @var{pid}. |
| If your program has saved a local copy of its process id, this could |
| potentially pose a problem. |
| |
| @subsection A Non-obvious Benefit of Using Checkpoints |
| |
| On some systems such as @sc{gnu}/Linux, address space randomization |
| is performed on new processes for security reasons. This makes it |
| difficult or impossible to set a breakpoint, or watchpoint, on an |
| absolute address if you have to restart the program, since the |
| absolute location of a symbol will change from one execution to the |
| next. |
| |
| A checkpoint, however, is an @emph{identical} copy of a process. |
| Therefore if you create a checkpoint at (eg.@:) the start of main, |
| and simply return to that checkpoint instead of restarting the |
| process, you can avoid the effects of address randomization and |
| your symbols will all stay in the same place. |
| |
| @node Stopping |
| @chapter Stopping and Continuing |
| |
| The principal purposes of using a debugger are so that you can stop your |
| program before it terminates; or so that, if your program runs into |
| trouble, you can investigate and find out why. |
| |
| Inside @value{GDBN}, your program may stop for any of several reasons, |
| such as a signal, a breakpoint, or reaching a new line after a |
| @value{GDBN} command such as @code{step}. You may then examine and |
| change variables, set new breakpoints or remove old ones, and then |
| continue execution. Usually, the messages shown by @value{GDBN} provide |
| ample explanation of the status of your program---but you can also |
| explicitly request this information at any time. |
| |
| @table @code |
| @kindex info program |
| @item info program |
| Display information about the status of your program: whether it is |
| running or not, what process it is, and why it stopped. |
| @end table |
| |
| @menu |
| * Breakpoints:: Breakpoints, watchpoints, and catchpoints |
| * Continuing and Stepping:: Resuming execution |
| * Skipping Over Functions and Files:: |
| Skipping over functions and files |
| * Signals:: Signals |
| * Thread Stops:: Stopping and starting multi-thread programs |
| @end menu |
| |
| @node Breakpoints |
| @section Breakpoints, Watchpoints, and Catchpoints |
| |
| @cindex breakpoints |
| A @dfn{breakpoint} makes your program stop whenever a certain point in |
| the program is reached. For each breakpoint, you can add conditions to |
| control in finer detail whether your program stops. You can set |
| breakpoints with the @code{break} command and its variants (@pxref{Set |
| Breaks, ,Setting Breakpoints}), to specify the place where your program |
| should stop by line number, function name or exact address in the |
| program. |
| |
| On some systems, you can set breakpoints in shared libraries before |
| the executable is run. There is a minor limitation on HP-UX systems: |
| you must wait until the executable is run in order to set breakpoints |
| in shared library routines that are not called directly by the program |
| (for example, routines that are arguments in a @code{pthread_create} |
| call). |
| |
| @cindex watchpoints |
| @cindex data breakpoints |
| @cindex memory tracing |
| @cindex breakpoint on memory address |
| @cindex breakpoint on variable modification |
| A @dfn{watchpoint} is a special breakpoint that stops your program |
| when the value of an expression changes. The expression may be a value |
| of a variable, or it could involve values of one or more variables |
| combined by operators, such as @samp{a + b}. This is sometimes called |
| @dfn{data breakpoints}. You must use a different command to set |
| watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside |
| from that, you can manage a watchpoint like any other breakpoint: you |
| enable, disable, and delete both breakpoints and watchpoints using the |
| same commands. |
| |
| You can arrange to have values from your program displayed automatically |
| whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,, |
| Automatic Display}. |
| |
| @cindex catchpoints |
| @cindex breakpoint on events |
| A @dfn{catchpoint} is another special breakpoint that stops your program |
| when a certain kind of event occurs, such as the throwing of a C@t{++} |
| exception or the loading of a library. As with watchpoints, you use a |
| different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting |
| Catchpoints}), but aside from that, you can manage a catchpoint like any |
| other breakpoint. (To stop when your program receives a signal, use the |
| @code{handle} command; see @ref{Signals, ,Signals}.) |
| |
| @cindex breakpoint numbers |
| @cindex numbers for breakpoints |
| @value{GDBN} assigns a number to each breakpoint, watchpoint, or |
| catchpoint when you create it; these numbers are successive integers |
| starting with one. In many of the commands for controlling various |
| features of breakpoints you use the breakpoint number to say which |
| breakpoint you want to change. Each breakpoint may be @dfn{enabled} or |
| @dfn{disabled}; if disabled, it has no effect on your program until you |
| enable it again. |
| |
| @cindex breakpoint ranges |
| @cindex ranges of breakpoints |
| Some @value{GDBN} commands accept a range of breakpoints on which to |
| operate. A breakpoint range is either a single breakpoint number, like |
| @samp{5}, or two such numbers, in increasing order, separated by a |
| hyphen, like @samp{5-7}. When a breakpoint range is given to a command, |
| all breakpoints in that range are operated on. |
| |
| @menu |
| * Set Breaks:: Setting breakpoints |
| * Set Watchpoints:: Setting watchpoints |
| * Set Catchpoints:: Setting catchpoints |
| * Delete Breaks:: Deleting breakpoints |
| * Disabling:: Disabling breakpoints |
| * Conditions:: Break conditions |
| * Break Commands:: Breakpoint command lists |
| * Dynamic Printf:: Dynamic printf |
| * Save Breakpoints:: How to save breakpoints in a file |
| * Static Probe Points:: Listing static probe points |
| * Error in Breakpoints:: ``Cannot insert breakpoints'' |
| * Breakpoint-related Warnings:: ``Breakpoint address adjusted...'' |
| @end menu |
| |
| @node Set Breaks |
| @subsection Setting Breakpoints |
| |
| @c FIXME LMB what does GDB do if no code on line of breakpt? |
| @c consider in particular declaration with/without initialization. |
| @c |
| @c FIXME 2 is there stuff on this already? break at fun start, already init? |
| |
| @kindex break |
| @kindex b @r{(@code{break})} |
| @vindex $bpnum@r{, convenience variable} |
| @cindex latest breakpoint |
| Breakpoints are set with the @code{break} command (abbreviated |
| @code{b}). The debugger convenience variable @samp{$bpnum} records the |
| number of the breakpoint you've set most recently; see @ref{Convenience |
| Vars,, Convenience Variables}, for a discussion of what you can do with |
| convenience variables. |
| |
| @table @code |
| @item break @var{location} |
| Set a breakpoint at the given @var{location}, which can specify a |
| function name, a line number, or an address of an instruction. |
| (@xref{Specify Location}, for a list of all the possible ways to |
| specify a @var{location}.) The breakpoint will stop your program just |
| before it executes any of the code in the specified @var{location}. |
| |
| When using source languages that permit overloading of symbols, such as |
| C@t{++}, a function name may refer to more than one possible place to break. |
| @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of |
| that situation. |
| |
| It is also possible to insert a breakpoint that will stop the program |
| only if a specific thread (@pxref{Thread-Specific Breakpoints}) |
| or a specific task (@pxref{Ada Tasks}) hits that breakpoint. |
| |
| @item break |
| When called without any arguments, @code{break} sets a breakpoint at |
| the next instruction to be executed in the selected stack frame |
| (@pxref{Stack, ,Examining the Stack}). In any selected frame but the |
| innermost, this makes your program stop as soon as control |
| returns to that frame. This is similar to the effect of a |
| @code{finish} command in the frame inside the selected frame---except |
| that @code{finish} does not leave an active breakpoint. If you use |
| @code{break} without an argument in the innermost frame, @value{GDBN} stops |
| the next time it reaches the current location; this may be useful |
| inside loops. |
| |
| @value{GDBN} normally ignores breakpoints when it resumes execution, until at |
| least one instruction has been executed. If it did not do this, you |
| would be unable to proceed past a breakpoint without first disabling the |
| breakpoint. This rule applies whether or not the breakpoint already |
| existed when your program stopped. |
| |
| @item break @dots{} if @var{cond} |
| Set a breakpoint with condition @var{cond}; evaluate the expression |
| @var{cond} each time the breakpoint is reached, and stop only if the |
| value is nonzero---that is, if @var{cond} evaluates as true. |
| @samp{@dots{}} stands for one of the possible arguments described |
| above (or no argument) specifying where to break. @xref{Conditions, |
| ,Break Conditions}, for more information on breakpoint conditions. |
| |
| @kindex tbreak |
| @item tbreak @var{args} |
| Set a breakpoint enabled only for one stop. @var{args} are the |
| same as for the @code{break} command, and the breakpoint is set in the same |
| way, but the breakpoint is automatically deleted after the first time your |
| program stops there. @xref{Disabling, ,Disabling Breakpoints}. |
| |
| @kindex hbreak |
| @cindex hardware breakpoints |
| @item hbreak @var{args} |
| Set a hardware-assisted breakpoint. @var{args} are the same as for the |
| @code{break} command and the breakpoint is set in the same way, but the |
| breakpoint requires hardware support and some target hardware may not |
| have this support. The main purpose of this is EPROM/ROM code |
| debugging, so you can set a breakpoint at an instruction without |
| changing the instruction. This can be used with the new trap-generation |
| provided by SPARClite DSU and most x86-based targets. These targets |
| will generate traps when a program accesses some data or instruction |
| address that is assigned to the debug registers. However the hardware |
| breakpoint registers can take a limited number of breakpoints. For |
| example, on the DSU, only two data breakpoints can be set at a time, and |
| @value{GDBN} will reject this command if more than two are used. Delete |
| or disable unused hardware breakpoints before setting new ones |
| (@pxref{Disabling, ,Disabling Breakpoints}). |
| @xref{Conditions, ,Break Conditions}. |
| For remote targets, you can restrict the number of hardware |
| breakpoints @value{GDBN} will use, see @ref{set remote |
| hardware-breakpoint-limit}. |
| |
| @kindex thbreak |
| @item thbreak @var{args} |
| Set a hardware-assisted breakpoint enabled only for one stop. @var{args} |
| are the same as for the @code{hbreak} command and the breakpoint is set in |
| the same way. However, like the @code{tbreak} command, |
| the breakpoint is automatically deleted after the |
| first time your program stops there. Also, like the @code{hbreak} |
| command, the breakpoint requires hardware support and some target hardware |
| may not have this support. @xref{Disabling, ,Disabling Breakpoints}. |
| See also @ref{Conditions, ,Break Conditions}. |
| |
| @kindex rbreak |
| @cindex regular expression |
| @cindex breakpoints at functions matching a regexp |
| @cindex set breakpoints in many functions |
| @item rbreak @var{regex} |
| Set breakpoints on all functions matching the regular expression |
| @var{regex}. This command sets an unconditional breakpoint on all |
| matches, printing a list of all breakpoints it set. Once these |
| breakpoints are set, they are treated just like the breakpoints set with |
| the @code{break} command. You can delete them, disable them, or make |
| them conditional the same way as any other breakpoint. |
| |
| The syntax of the regular expression is the standard one used with tools |
| like @file{grep}. Note that this is different from the syntax used by |
| shells, so for instance @code{foo*} matches all functions that include |
| an @code{fo} followed by zero or more @code{o}s. There is an implicit |
| @code{.*} leading and trailing the regular expression you supply, so to |
| match only functions that begin with @code{foo}, use @code{^foo}. |
| |
| @cindex non-member C@t{++} functions, set breakpoint in |
| When debugging C@t{++} programs, @code{rbreak} is useful for setting |
| breakpoints on overloaded functions that are not members of any special |
| classes. |
| |
| @cindex set breakpoints on all functions |
| The @code{rbreak} command can be used to set breakpoints in |
| @strong{all} the functions in a program, like this: |
| |
| @smallexample |
| (@value{GDBP}) rbreak . |
| @end smallexample |
| |
| @item rbreak @var{file}:@var{regex} |
| If @code{rbreak} is called with a filename qualification, it limits |
| the search for functions matching the given regular expression to the |
| specified @var{file}. This can be used, for example, to set breakpoints on |
| every function in a given file: |
| |
| @smallexample |
| (@value{GDBP}) rbreak file.c:. |
| @end smallexample |
| |
| The colon separating the filename qualifier from the regex may |
| optionally be surrounded by spaces. |
| |
| @kindex info breakpoints |
| @cindex @code{$_} and @code{info breakpoints} |
| @item info breakpoints @r{[}@var{n}@dots{}@r{]} |
| @itemx info break @r{[}@var{n}@dots{}@r{]} |
| Print a table of all breakpoints, watchpoints, and catchpoints set and |
| not deleted. Optional argument @var{n} means print information only |
| about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)). |
| For each breakpoint, following columns are printed: |
| |
| @table @emph |
| @item Breakpoint Numbers |
| @item Type |
| Breakpoint, watchpoint, or catchpoint. |
| @item Disposition |
| Whether the breakpoint is marked to be disabled or deleted when hit. |
| @item Enabled or Disabled |
| Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints |
| that are not enabled. |
| @item Address |
| Where the breakpoint is in your program, as a memory address. For a |
| pending breakpoint whose address is not yet known, this field will |
| contain @samp{<PENDING>}. Such breakpoint won't fire until a shared |
| library that has the symbol or line referred by breakpoint is loaded. |
| See below for details. A breakpoint with several locations will |
| have @samp{<MULTIPLE>} in this field---see below for details. |
| @item What |
| Where the breakpoint is in the source for your program, as a file and |
| line number. For a pending breakpoint, the original string passed to |
| the breakpoint command will be listed as it cannot be resolved until |
| the appropriate shared library is loaded in the future. |
| @end table |
| |
| @noindent |
| If a breakpoint is conditional, there are two evaluation modes: ``host'' and |
| ``target''. If mode is ``host'', breakpoint condition evaluation is done by |
| @value{GDBN} on the host's side. If it is ``target'', then the condition |
| is evaluated by the target. The @code{info break} command shows |
| the condition on the line following the affected breakpoint, together with |
| its condition evaluation mode in between parentheses. |
| |
| Breakpoint commands, if any, are listed after that. A pending breakpoint is |
| allowed to have a condition specified for it. The condition is not parsed for |
| validity until a shared library is loaded that allows the pending |
| breakpoint to resolve to a valid location. |
| |
| @noindent |
| @code{info break} with a breakpoint |
| number @var{n} as argument lists only that breakpoint. The |
| convenience variable @code{$_} and the default examining-address for |
| the @code{x} command are set to the address of the last breakpoint |
| listed (@pxref{Memory, ,Examining Memory}). |
| |
| @noindent |
| @code{info break} displays a count of the number of times the breakpoint |
| has been hit. This is especially useful in conjunction with the |
| @code{ignore} command. You can ignore a large number of breakpoint |
| hits, look at the breakpoint info to see how many times the breakpoint |
| was hit, and then run again, ignoring one less than that number. This |
| will get you quickly to the last hit of that breakpoint. |
| |
| @noindent |
| For a breakpoints with an enable count (xref) greater than 1, |
| @code{info break} also displays that count. |
| |
| @end table |
| |
| @value{GDBN} allows you to set any number of breakpoints at the same place in |
| your program. There is nothing silly or meaningless about this. When |
| the breakpoints are conditional, this is even useful |
| (@pxref{Conditions, ,Break Conditions}). |
| |
| @cindex multiple locations, breakpoints |
| @cindex breakpoints, multiple locations |
| It is possible that a breakpoint corresponds to several locations |
| in your program. Examples of this situation are: |
| |
| @itemize @bullet |
| @item |
| Multiple functions in the program may have the same name. |
| |
| @item |
| For a C@t{++} constructor, the @value{NGCC} compiler generates several |
| instances of the function body, used in different cases. |
| |
| @item |
| For a C@t{++} template function, a given line in the function can |
| correspond to any number of instantiations. |
| |
| @item |
| For an inlined function, a given source line can correspond to |
| several places where that function is inlined. |
| @end itemize |
| |
| In all those cases, @value{GDBN} will insert a breakpoint at all |
| the relevant locations. |
| |
| A breakpoint with multiple locations is displayed in the breakpoint |
| table using several rows---one header row, followed by one row for |
| each breakpoint location. The header row has @samp{<MULTIPLE>} in the |
| address column. The rows for individual locations contain the actual |
| addresses for locations, and show the functions to which those |
| locations belong. The number column for a location is of the form |
| @var{breakpoint-number}.@var{location-number}. |
| |
| For example: |
| |
| @smallexample |
| Num Type Disp Enb Address What |
| 1 breakpoint keep y <MULTIPLE> |
| stop only if i==1 |
| breakpoint already hit 1 time |
| 1.1 y 0x080486a2 in void foo<int>() at t.cc:8 |
| 1.2 y 0x080486ca in void foo<double>() at t.cc:8 |
| @end smallexample |
| |
| Each location can be individually enabled or disabled by passing |
| @var{breakpoint-number}.@var{location-number} as argument to the |
| @code{enable} and @code{disable} commands. Note that you cannot |
| delete the individual locations from the list, you can only delete the |
| entire list of locations that belong to their parent breakpoint (with |
| the @kbd{delete @var{num}} command, where @var{num} is the number of |
| the parent breakpoint, 1 in the above example). Disabling or enabling |
| the parent breakpoint (@pxref{Disabling}) affects all of the locations |
| that belong to that breakpoint. |
| |
| @cindex pending breakpoints |
| It's quite common to have a breakpoint inside a shared library. |
| Shared libraries can be loaded and unloaded explicitly, |
| and possibly repeatedly, as the program is executed. To support |
| this use case, @value{GDBN} updates breakpoint locations whenever |
| any shared library is loaded or unloaded. Typically, you would |
| set a breakpoint in a shared library at the beginning of your |
| debugging session, when the library is not loaded, and when the |
| symbols from the library are not available. When you try to set |
| breakpoint, @value{GDBN} will ask you if you want to set |
| a so called @dfn{pending breakpoint}---breakpoint whose address |
| is not yet resolved. |
| |
| After the program is run, whenever a new shared library is loaded, |
| @value{GDBN} reevaluates all the breakpoints. When a newly loaded |
| shared library contains the symbol or line referred to by some |
| pending breakpoint, that breakpoint is resolved and becomes an |
| ordinary breakpoint. When a library is unloaded, all breakpoints |
| that refer to its symbols or source lines become pending again. |
| |
| This logic works for breakpoints with multiple locations, too. For |
| example, if you have a breakpoint in a C@t{++} template function, and |
| a newly loaded shared library has an instantiation of that template, |
| a new location is added to the list of locations for the breakpoint. |
| |
| Except for having unresolved address, pending breakpoints do not |
| differ from regular breakpoints. You can set conditions or commands, |
| enable and disable them and perform other breakpoint operations. |
| |
| @value{GDBN} provides some additional commands for controlling what |
| happens when the @samp{break} command cannot resolve breakpoint |
| address specification to an address: |
| |
| @kindex set breakpoint pending |
| @kindex show breakpoint pending |
| @table @code |
| @item set breakpoint pending auto |
| This is the default behavior. When @value{GDBN} cannot find the breakpoint |
| location, it queries you whether a pending breakpoint should be created. |
| |
| @item set breakpoint pending on |
| This indicates that an unrecognized breakpoint location should automatically |
| result in a pending breakpoint being created. |
| |
| @item set breakpoint pending off |
| This indicates that pending breakpoints are not to be created. Any |
| unrecognized breakpoint location results in an error. This setting does |
| not affect any pending breakpoints previously created. |
| |
| @item show breakpoint pending |
| Show the current behavior setting for creating pending breakpoints. |
| @end table |
| |
| The settings above only affect the @code{break} command and its |
| variants. Once breakpoint is set, it will be automatically updated |
| as shared libraries are loaded and unloaded. |
| |
| @cindex automatic hardware breakpoints |
| For some targets, @value{GDBN} can automatically decide if hardware or |
| software breakpoints should be used, depending on whether the |
| breakpoint address is read-only or read-write. This applies to |
| breakpoints set with the @code{break} command as well as to internal |
| breakpoints set by commands like @code{next} and @code{finish}. For |
| breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware |
| breakpoints. |
| |
| You can control this automatic behaviour with the following commands:: |
| |
| @kindex set breakpoint auto-hw |
| @kindex show breakpoint auto-hw |
| @table @code |
| @item set breakpoint auto-hw on |
| This is the default behavior. When @value{GDBN} sets a breakpoint, it |
| will try to use the target memory map to decide if software or hardware |
| breakpoint must be used. |
| |
| @item set breakpoint auto-hw off |
| This indicates @value{GDBN} should not automatically select breakpoint |
| type. If the target provides a memory map, @value{GDBN} will warn when |
| trying to set software breakpoint at a read-only address. |
| @end table |
| |
| @value{GDBN} normally implements breakpoints by replacing the program code |
| at the breakpoint address with a special instruction, which, when |
| executed, given control to the debugger. By default, the program |
| code is so modified only when the program is resumed. As soon as |
| the program stops, @value{GDBN} restores the original instructions. This |
| behaviour guards against leaving breakpoints inserted in the |
| target should gdb abrubptly disconnect. However, with slow remote |
| targets, inserting and removing breakpoint can reduce the performance. |
| This behavior can be controlled with the following commands:: |
| |
| @kindex set breakpoint always-inserted |
| @kindex show breakpoint always-inserted |
| @table @code |
| @item set breakpoint always-inserted off |
| All breakpoints, including newly added by the user, are inserted in |
| the target only when the target is resumed. All breakpoints are |
| removed from the target when it stops. |
| |
| @item set breakpoint always-inserted on |
| Causes all breakpoints to be inserted in the target at all times. If |
| the user adds a new breakpoint, or changes an existing breakpoint, the |
| breakpoints in the target are updated immediately. A breakpoint is |
| removed from the target only when breakpoint itself is removed. |
| |
| @cindex non-stop mode, and @code{breakpoint always-inserted} |
| @item set breakpoint always-inserted auto |
| This is the default mode. If @value{GDBN} is controlling the inferior |
| in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if |
| @code{breakpoint always-inserted} mode is on. If @value{GDBN} is |
| controlling the inferior in all-stop mode, @value{GDBN} behaves as if |
| @code{breakpoint always-inserted} mode is off. |
| @end table |
| |
| @value{GDBN} handles conditional breakpoints by evaluating these conditions |
| when a breakpoint breaks. If the condition is true, then the process being |
| debugged stops, otherwise the process is resumed. |
| |
| If the target supports evaluating conditions on its end, @value{GDBN} may |
| download the breakpoint, together with its conditions, to it. |
| |
| This feature can be controlled via the following commands: |
| |
| @kindex set breakpoint condition-evaluation |
| @kindex show breakpoint condition-evaluation |
| @table @code |
| @item set breakpoint condition-evaluation host |
| This option commands @value{GDBN} to evaluate the breakpoint |
| conditions on the host's side. Unconditional breakpoints are sent to |
| the target which in turn receives the triggers and reports them back to GDB |
| for condition evaluation. This is the standard evaluation mode. |
| |
| @item set breakpoint condition-evaluation target |
| This option commands @value{GDBN} to download breakpoint conditions |
| to the target at the moment of their insertion. The target |
| is responsible for evaluating the conditional expression and reporting |
| breakpoint stop events back to @value{GDBN} whenever the condition |
| is true. Due to limitations of target-side evaluation, some conditions |
| cannot be evaluated there, e.g., conditions that depend on local data |
| that is only known to the host. Examples include |
| conditional expressions involving convenience variables, complex types |
| that cannot be handled by the agent expression parser and expressions |
| that are too long to be sent over to the target, specially when the |
| target is a remote system. In these cases, the conditions will be |
| evaluated by @value{GDBN}. |
| |
| @item set breakpoint condition-evaluation auto |
| This is the default mode. If the target supports evaluating breakpoint |
| conditions on its end, @value{GDBN} will download breakpoint conditions to |
| the target (limitations mentioned previously apply). If the target does |
| not support breakpoint condition evaluation, then @value{GDBN} will fallback |
| to evaluating all these conditions on the host's side. |
| @end table |
| |
| |
| @cindex negative breakpoint numbers |
| @cindex internal @value{GDBN} breakpoints |
| @value{GDBN} itself sometimes sets breakpoints in your program for |
| special purposes, such as proper handling of @code{longjmp} (in C |
| programs). These internal breakpoints are assigned negative numbers, |
| starting with @code{-1}; @samp{info breakpoints} does not display them. |
| You can see these breakpoints with the @value{GDBN} maintenance command |
| @samp{maint info breakpoints} (@pxref{maint info breakpoints}). |
| |
| |
| @node Set Watchpoints |
| @subsection Setting Watchpoints |
| |
| @cindex setting watchpoints |
| You can use a watchpoint to stop execution whenever the value of an |
| expression changes, without having to predict a particular place where |
| this may happen. (This is sometimes called a @dfn{data breakpoint}.) |
| The expression may be as simple as the value of a single variable, or |
| as complex as many variables combined by operators. Examples include: |
| |
| @itemize @bullet |
| @item |
| A reference to the value of a single variable. |
| |
| @item |
| An address cast to an appropriate data type. For example, |
| @samp{*(int *)0x12345678} will watch a 4-byte region at the specified |
| address (assuming an @code{int} occupies 4 bytes). |
| |
| @item |
| An arbitrarily complex expression, such as @samp{a*b + c/d}. The |
| expression can use any operators valid in the program's native |
| language (@pxref{Languages}). |
| @end itemize |
| |
| You can set a watchpoint on an expression even if the expression can |
| not be evaluated yet. For instance, you can set a watchpoint on |
| @samp{*global_ptr} before @samp{global_ptr} is initialized. |
| @value{GDBN} will stop when your program sets @samp{global_ptr} and |
| the expression produces a valid value. If the expression becomes |
| valid in some other way than changing a variable (e.g.@: if the memory |
| pointed to by @samp{*global_ptr} becomes readable as the result of a |
| @code{malloc} call), @value{GDBN} may not stop until the next time |
| the expression changes. |
| |
| @cindex software watchpoints |
| @cindex hardware watchpoints |
| Depending on your system, watchpoints may be implemented in software or |
| hardware. @value{GDBN} does software watchpointing by single-stepping your |
| program and testing the variable's value each time, which is hundreds of |
| times slower than normal execution. (But this may still be worth it, to |
| catch errors where you have no clue what part of your program is the |
| culprit.) |
| |
| On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other |
| x86-based targets, @value{GDBN} includes support for hardware |
| watchpoints, which do not slow down the running of your program. |
| |
| @table @code |
| @kindex watch |
| @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]} |
| Set a watchpoint for an expression. @value{GDBN} will break when the |
| expression @var{expr} is written into by the program and its value |
| changes. The simplest (and the most popular) use of this command is |
| to watch the value of a single variable: |
| |
| @smallexample |
| (@value{GDBP}) watch foo |
| @end smallexample |
| |
| If the command includes a @code{@r{[}thread @var{threadnum}@r{]}} |
| argument, @value{GDBN} breaks only when the thread identified by |
| @var{threadnum} changes the value of @var{expr}. If any other threads |
| change the value of @var{expr}, @value{GDBN} will not break. Note |
| that watchpoints restricted to a single thread in this way only work |
| with Hardware Watchpoints. |
| |
| Ordinarily a watchpoint respects the scope of variables in @var{expr} |
| (see below). The @code{-location} argument tells @value{GDBN} to |
| instead watch the memory referred to by @var{expr}. In this case, |
| @value{GDBN} will evaluate @var{expr}, take the address of the result, |
| and watch the memory at that address. The type of the result is used |
| to determine the size of the watched memory. If the expression's |
| result does not have an address, then @value{GDBN} will print an |
| error. |
| |
| The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation |
| of masked watchpoints, if the current architecture supports this |
| feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC |
| Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition |
| to an address to watch. The mask specifies that some bits of an address |
| (the bits which are reset in the mask) should be ignored when matching |
| the address accessed by the inferior against the watchpoint address. |
| Thus, a masked watchpoint watches many addresses simultaneously---those |
| addresses whose unmasked bits are identical to the unmasked bits in the |
| watchpoint address. The @code{mask} argument implies @code{-location}. |
| Examples: |
| |
| @smallexample |
| (@value{GDBP}) watch foo mask 0xffff00ff |
| (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00 |
| @end smallexample |
| |
| @kindex rwatch |
| @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]} |
| Set a watchpoint that will break when the value of @var{expr} is read |
| by the program. |
| |
| @kindex awatch |
| @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]} |
| Set a watchpoint that will break when @var{expr} is either read from |
| or written into by the program. |
| |
| @kindex info watchpoints @r{[}@var{n}@dots{}@r{]} |
| @item info watchpoints @r{[}@var{n}@dots{}@r{]} |
| This command prints a list of watchpoints, using the same format as |
| @code{info break} (@pxref{Set Breaks}). |
| @end table |
| |
| If you watch for a change in a numerically entered address you need to |
| dereference it, as the address itself is just a constant number which will |
| never change. @value{GDBN} refuses to create a watchpoint that watches |
| a never-changing value: |
| |
| @smallexample |
| (@value{GDBP}) watch 0x600850 |
| Cannot watch constant value 0x600850. |
| (@value{GDBP}) watch *(int *) 0x600850 |
| Watchpoint 1: *(int *) 6293584 |
| @end smallexample |
| |
| @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware |
| watchpoints execute very quickly, and the debugger reports a change in |
| value at the exact instruction where the change occurs. If @value{GDBN} |
| cannot set a hardware watchpoint, it sets a software watchpoint, which |
| executes more slowly and reports the change in value at the next |
| @emph{statement}, not the instruction, after the change occurs. |
| |
| @cindex use only software watchpoints |
| You can force @value{GDBN} to use only software watchpoints with the |
| @kbd{set can-use-hw-watchpoints 0} command. With this variable set to |
| zero, @value{GDBN} will never try to use hardware watchpoints, even if |
| the underlying system supports them. (Note that hardware-assisted |
| watchpoints that were set @emph{before} setting |
| @code{can-use-hw-watchpoints} to zero will still use the hardware |
| mechanism of watching expression values.) |
| |
| @table @code |
| @item set can-use-hw-watchpoints |
| @kindex set can-use-hw-watchpoints |
| Set whether or not to use hardware watchpoints. |
| |
| @item show can-use-hw-watchpoints |
| @kindex show can-use-hw-watchpoints |
| Show the current mode of using hardware watchpoints. |
| @end table |
| |
| For remote targets, you can restrict the number of hardware |
| watchpoints @value{GDBN} will use, see @ref{set remote |
| hardware-breakpoint-limit}. |
| |
| When you issue the @code{watch} command, @value{GDBN} reports |
| |
| @smallexample |
| Hardware watchpoint @var{num}: @var{expr} |
| @end smallexample |
| |
| @noindent |
| if it was able to set a hardware watchpoint. |
| |
| Currently, the @code{awatch} and @code{rwatch} commands can only set |
| hardware watchpoints, because accesses to data that don't change the |
| value of the watched expression cannot be detected without examining |
| every instruction as it is being executed, and @value{GDBN} does not do |
| that currently. If @value{GDBN} finds that it is unable to set a |
| hardware breakpoint with the @code{awatch} or @code{rwatch} command, it |
| will print a message like this: |
| |
| @smallexample |
| Expression cannot be implemented with read/access watchpoint. |
| @end smallexample |
| |
| Sometimes, @value{GDBN} cannot set a hardware watchpoint because the |
| data type of the watched expression is wider than what a hardware |
| watchpoint on the target machine can handle. For example, some systems |
| can only watch regions that are up to 4 bytes wide; on such systems you |
| cannot set hardware watchpoints for an expression that yields a |
| double-precision floating-point number (which is typically 8 bytes |
| wide). As a work-around, it might be possible to break the large region |
| into a series of smaller ones and watch them with separate watchpoints. |
| |
| If you set too many hardware watchpoints, @value{GDBN} might be unable |
| to insert all of them when you resume the execution of your program. |
| Since the precise number of active watchpoints is unknown until such |
| time as the program is about to be resumed, @value{GDBN} might not be |
| able to warn you about this when you set the watchpoints, and the |
| warning will be printed only when the program is resumed: |
| |
| @smallexample |
| Hardware watchpoint @var{num}: Could not insert watchpoint |
| @end smallexample |
| |
| @noindent |
| If this happens, delete or disable some of the watchpoints. |
| |
| Watching complex expressions that reference many variables can also |
| exhaust the resources available for hardware-assisted watchpoints. |
| That's because @value{GDBN} needs to watch every variable in the |
| expression with separately allocated resources. |
| |
| If you call a function interactively using @code{print} or @code{call}, |
| any watchpoints you have set will be inactive until @value{GDBN} reaches another |
| kind of breakpoint or the call completes. |
| |
| @value{GDBN} automatically deletes watchpoints that watch local |
| (automatic) variables, or expressions that involve such variables, when |
| they go out of scope, that is, when the execution leaves the block in |
| which these variables were defined. In particular, when the program |
| being debugged terminates, @emph{all} local variables go out of scope, |
| and so only watchpoints that watch global variables remain set. If you |
| rerun the program, you will need to set all such watchpoints again. One |
| way of doing that would be to set a code breakpoint at the entry to the |
| @code{main} function and when it breaks, set all the watchpoints. |
| |
| @cindex watchpoints and threads |
| @cindex threads and watchpoints |
| In multi-threaded programs, watchpoints will detect changes to the |
| watched expression from every thread. |
| |
| @quotation |
| @emph{Warning:} In multi-threaded programs, software watchpoints |
| have only limited usefulness. If @value{GDBN} creates a software |
| watchpoint, it can only watch the value of an expression @emph{in a |
| single thread}. If you are confident that the expression can only |
| change due to the current thread's activity (and if you are also |
| confident that no other thread can become current), then you can use |
| software watchpoints as usual. However, @value{GDBN} may not notice |
| when a non-current thread's activity changes the expression. (Hardware |
| watchpoints, in contrast, watch an expression in all threads.) |
| @end quotation |
| |
| @xref{set remote hardware-watchpoint-limit}. |
| |
| @node Set Catchpoints |
| @subsection Setting Catchpoints |
| @cindex catchpoints, setting |
| @cindex exception handlers |
| @cindex event handling |
| |
| You can use @dfn{catchpoints} to cause the debugger to stop for certain |
| kinds of program events, such as C@t{++} exceptions or the loading of a |
| shared library. Use the @code{catch} command to set a catchpoint. |
| |
| @table @code |
| @kindex catch |
| @item catch @var{event} |
| Stop when @var{event} occurs. @var{event} can be any of the following: |
| @table @code |
| @item throw |
| @cindex stop on C@t{++} exceptions |
| The throwing of a C@t{++} exception. |
| |
| @item catch |
| The catching of a C@t{++} exception. |
| |
| @item exception |
| @cindex Ada exception catching |
| @cindex catch Ada exceptions |
| An Ada exception being raised. If an exception name is specified |
| at the end of the command (eg @code{catch exception Program_Error}), |
| the debugger will stop only when this specific exception is raised. |
| Otherwise, the debugger stops execution when any Ada exception is raised. |
| |
| When inserting an exception catchpoint on a user-defined exception whose |
| name is identical to one of the exceptions defined by the language, the |
| fully qualified name must be used as the exception name. Otherwise, |
| @value{GDBN} will assume that it should stop on the pre-defined exception |
| rather than the user-defined one. For instance, assuming an exception |
| called @code{Constraint_Error} is defined in package @code{Pck}, then |
| the command to use to catch such exceptions is @kbd{catch exception |
| Pck.Constraint_Error}. |
| |
| @item exception unhandled |
| An exception that was raised but is not handled by the program. |
| |
| @item assert |
| A failed Ada assertion. |
| |
| @item exec |
| @cindex break on fork/exec |
| A call to @code{exec}. This is currently only available for HP-UX |
| and @sc{gnu}/Linux. |
| |
| @item syscall |
| @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{} |
| @cindex break on a system call. |
| A call to or return from a system call, a.k.a.@: @dfn{syscall}. A |
| syscall is a mechanism for application programs to request a service |
| from the operating system (OS) or one of the OS system services. |
| @value{GDBN} can catch some or all of the syscalls issued by the |
| debuggee, and show the related information for each syscall. If no |
| argument is specified, calls to and returns from all system calls |
| will be caught. |
| |
| @var{name} can be any system call name that is valid for the |
| underlying OS. Just what syscalls are valid depends on the OS. On |
| GNU and Unix systems, you can find the full list of valid syscall |
| names on @file{/usr/include/asm/unistd.h}. |
| |
| @c For MS-Windows, the syscall names and the corresponding numbers |
| @c can be found, e.g., on this URL: |
| @c http://www.metasploit.com/users/opcode/syscalls.html |
| @c but we don't support Windows syscalls yet. |
| |
| Normally, @value{GDBN} knows in advance which syscalls are valid for |
| each OS, so you can use the @value{GDBN} command-line completion |
| facilities (@pxref{Completion,, command completion}) to list the |
| available choices. |
| |
| You may also specify the system call numerically. A syscall's |
| number is the value passed to the OS's syscall dispatcher to |
| identify the requested service. When you specify the syscall by its |
| name, @value{GDBN} uses its database of syscalls to convert the name |
| into the corresponding numeric code, but using the number directly |
| may be useful if @value{GDBN}'s database does not have the complete |
| list of syscalls on your system (e.g., because @value{GDBN} lags |
| behind the OS upgrades). |
| |
| The example below illustrates how this command works if you don't provide |
| arguments to it: |
| |
| @smallexample |
| (@value{GDBP}) catch syscall |
| Catchpoint 1 (syscall) |
| (@value{GDBP}) r |
| Starting program: /tmp/catch-syscall |
| |
| Catchpoint 1 (call to syscall 'close'), \ |
| 0xffffe424 in __kernel_vsyscall () |
| (@value{GDBP}) c |
| Continuing. |
| |
| Catchpoint 1 (returned from syscall 'close'), \ |
| 0xffffe424 in __kernel_vsyscall () |
| (@value{GDBP}) |
| @end smallexample |
| |
| Here is an example of catching a system call by name: |
| |
| @smallexample |
| (@value{GDBP}) catch syscall chroot |
| Catchpoint 1 (syscall 'chroot' [61]) |
| (@value{GDBP}) r |
| Starting program: /tmp/catch-syscall |
| |
| Catchpoint 1 (call to syscall 'chroot'), \ |
| 0xffffe424 in __kernel_vsyscall () |
| (@value{GDBP}) c |
| Continuing. |
| |
| Catchpoint 1 (returned from syscall 'chroot'), \ |
| 0xffffe424 in __kernel_vsyscall () |
| (@value{GDBP}) |
| @end smallexample |
| |
| An example of specifying a system call numerically. In the case |
| below, the syscall number has a corresponding entry in the XML |
| file, so @value{GDBN} finds its name and prints it: |
| |
| @smallexample |
| (@value{GDBP}) catch syscall 252 |
| Catchpoint 1 (syscall(s) 'exit_group') |
| (@value{GDBP}) r |
| Starting program: /tmp/catch-syscall |
| |
| Catchpoint 1 (call to syscall 'exit_group'), \ |
| 0xffffe424 in __kernel_vsyscall () |
| (@value{GDBP}) c |
| Continuing. |
| |
| Program exited normally. |
| (@value{GDBP}) |
| @end smallexample |
| |
| However, there can be situations when there is no corresponding name |
| in XML file for that syscall number. In this case, @value{GDBN} prints |
| a warning message saying that it was not able to find the syscall name, |
| but the catchpoint will be set anyway. See the example below: |
| |
| @smallexample |
| (@value{GDBP}) catch syscall 764 |
| warning: The number '764' does not represent a known syscall. |
| Catchpoint 2 (syscall 764) |
| (@value{GDBP}) |
| @end smallexample |
| |
| If you configure @value{GDBN} using the @samp{--without-expat} option, |
| it will not be able to display syscall names. Also, if your |
| architecture does not have an XML file describing its system calls, |
| you will not be able to see the syscall names. It is important to |
| notice that these two features are used for accessing the syscall |
| name database. In either case, you will see a warning like this: |
| |
| @smallexample |
| (@value{GDBP}) catch syscall |
| warning: Could not open "syscalls/i386-linux.xml" |
| warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'. |
| GDB will not be able to display syscall names. |
| Catchpoint 1 (syscall) |
| (@value{GDBP}) |
| @end smallexample |
| |
| Of course, the file name will change depending on your architecture and system. |
| |
| Still using the example above, you can also try to catch a syscall by its |
| number. In this case, you would see something like: |
| |
| @smallexample |
| (@value{GDBP}) catch syscall 252 |
| Catchpoint 1 (syscall(s) 252) |
| @end smallexample |
| |
| Again, in this case @value{GDBN} would not be able to display syscall's names. |
| |
| @item fork |
| A call to @code{fork}. This is currently only available for HP-UX |
| and @sc{gnu}/Linux. |
| |
| @item vfork |
| A call to @code{vfork}. This is currently only available for HP-UX |
| and @sc{gnu}/Linux. |
| |
| @item load @r{[}regexp@r{]} |
| @itemx unload @r{[}regexp@r{]} |
| The loading or unloading of a shared library. If @var{regexp} is |
| given, then the catchpoint will stop only if the regular expression |
| matches one of the affected libraries. |
| |
| @end table |
| |
| @item tcatch @var{event} |
| Set a catchpoint that is enabled only for one stop. The catchpoint is |
| automatically deleted after the first time the event is caught. |
| |
| @end table |
| |
| Use the @code{info break} command to list the current catchpoints. |
| |
| There are currently some limitations to C@t{++} exception handling |
| (@code{catch throw} and @code{catch catch}) in @value{GDBN}: |
| |
| @itemize @bullet |
| @item |
| If you call a function interactively, @value{GDBN} normally returns |
| control to you when the function has finished executing. If the call |
| raises an exception, however, the call may bypass the mechanism that |
| returns control to you and cause your program either to abort or to |
| simply continue running until it hits a breakpoint, catches a signal |
| that @value{GDBN} is listening for, or exits. This is the case even if |
| you set a catchpoint for the exception; catchpoints on exceptions are |
| disabled within interactive calls. |
| |
| @item |
| You cannot raise an exception interactively. |
| |
| @item |
| You cannot install an exception handler interactively. |
| @end itemize |
| |
| @cindex raise exceptions |
| Sometimes @code{catch} is not the best way to debug exception handling: |
| if you need to know exactly where an exception is raised, it is better to |
| stop @emph{before} the exception handler is called, since that way you |
| can see the stack before any unwinding takes place. If you set a |
| breakpoint in an exception handler instead, it may not be easy to find |
| out where the exception was raised. |
| |
| To stop just before an exception handler is called, you need some |
| knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are |
| raised by calling a library function named @code{__raise_exception} |
| which has the following ANSI C interface: |
| |
| @smallexample |
| /* @var{addr} is where the exception identifier is stored. |
| @var{id} is the exception identifier. */ |
| void __raise_exception (void **addr, void *id); |
| @end smallexample |
| |
| @noindent |
| To make the debugger catch all exceptions before any stack |
| unwinding takes place, set a breakpoint on @code{__raise_exception} |
| (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}). |
| |
| With a conditional breakpoint (@pxref{Conditions, ,Break Conditions}) |
| that depends on the value of @var{id}, you can stop your program when |
| a specific exception is raised. You can use multiple conditional |
| breakpoints to stop your program when any of a number of exceptions are |
| raised. |
| |
| |
| @node Delete Breaks |
| @subsection Deleting Breakpoints |
| |
| @cindex clearing breakpoints, watchpoints, catchpoints |
| @cindex deleting breakpoints, watchpoints, catchpoints |
| It is often necessary to eliminate a breakpoint, watchpoint, or |
| catchpoint once it has done its job and you no longer want your program |
| to stop there. This is called @dfn{deleting} the breakpoint. A |
| breakpoint that has been deleted no longer exists; it is forgotten. |
| |
| With the @code{clear} command you can delete breakpoints according to |
| where they are in your program. With the @code{delete} command you can |
| delete individual breakpoints, watchpoints, or catchpoints by specifying |
| their breakpoint numbers. |
| |
| It is not necessary to delete a breakpoint to proceed past it. @value{GDBN} |
| automatically ignores breakpoints on the first instruction to be executed |
| when you continue execution without changing the execution address. |
| |
| @table @code |
| @kindex clear |
| @item clear |
| Delete any breakpoints at the next instruction to be executed in the |
| selected stack frame (@pxref{Selection, ,Selecting a Frame}). When |
| the innermost frame is selected, this is a good way to delete a |
| breakpoint where your program just stopped. |
| |
| @item clear @var{location} |
| Delete any breakpoints set at the specified @var{location}. |
| @xref{Specify Location}, for the various forms of @var{location}; the |
| most useful ones are listed below: |
| |
| @table @code |
| @item clear @var{function} |
| @itemx clear @var{filename}:@var{function} |
| Delete any breakpoints set at entry to the named @var{function}. |
| |
| @item clear @var{linenum} |
| @itemx clear @var{filename}:@var{linenum} |
| Delete any breakpoints set at or within the code of the specified |
| @var{linenum} of the specified @var{filename}. |
| @end table |
| |
| @cindex delete breakpoints |
| @kindex delete |
| @kindex d @r{(@code{delete})} |
| @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} |
| Delete the breakpoints, watchpoints, or catchpoints of the breakpoint |
| ranges specified as arguments. If no argument is specified, delete all |
| breakpoints (@value{GDBN} asks confirmation, unless you have @code{set |
| confirm off}). You can abbreviate this command as @code{d}. |
| @end table |
| |
| @node Disabling |
| @subsection Disabling Breakpoints |
| |
| @cindex enable/disable a breakpoint |
| Rather than deleting a breakpoint, watchpoint, or catchpoint, you might |
| prefer to @dfn{disable} it. This makes the breakpoint inoperative as if |
| it had been deleted, but remembers the information on the breakpoint so |
| that you can @dfn{enable} it again later. |
| |
| You disable and enable breakpoints, watchpoints, and catchpoints with |
| the @code{enable} and @code{disable} commands, optionally specifying |
| one or more breakpoint numbers as arguments. Use @code{info break} to |
| print a list of all breakpoints, watchpoints, and catchpoints if you |
| do not know which numbers to use. |
| |
| Disabling and enabling a breakpoint that has multiple locations |
| affects all of its locations. |
| |
| A breakpoint, watchpoint, or catchpoint can have any of several |
| different states of enablement: |
| |
| @itemize @bullet |
| @item |
| Enabled. The breakpoint stops your program. A breakpoint set |
| with the @code{break} command starts out in this state. |
| @item |
| Disabled. The breakpoint has no effect on your program. |
| @item |
| Enabled once. The breakpoint stops your program, but then becomes |
| disabled. |
| @item |
| Enabled for a count. The breakpoint stops your program for the next |
| N times, then becomes disabled. |
| @item |
| Enabled for deletion. The breakpoint stops your program, but |
| immediately after it does so it is deleted permanently. A breakpoint |
| set with the @code{tbreak} command starts out in this state. |
| @end itemize |
| |
| You can use the following commands to enable or disable breakpoints, |
| watchpoints, and catchpoints: |
| |
| @table @code |
| @kindex disable |
| @kindex dis @r{(@code{disable})} |
| @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} |
| Disable the specified breakpoints---or all breakpoints, if none are |
| listed. A disabled breakpoint has no effect but is not forgotten. All |
| options such as ignore-counts, conditions and commands are remembered in |
| case the breakpoint is enabled again later. You may abbreviate |
| @code{disable} as @code{dis}. |
| |
| @kindex enable |
| @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]} |
| Enable the specified breakpoints (or all defined breakpoints). They |
| become effective once again in stopping your program. |
| |
| @item enable @r{[}breakpoints@r{]} once @var{range}@dots{} |
| Enable the specified breakpoints temporarily. @value{GDBN} disables any |
| of these breakpoints immediately after stopping your program. |
| |
| @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{} |
| Enable the specified breakpoints temporarily. @value{GDBN} records |
| @var{count} with each of the specified breakpoints, and decrements a |
| breakpoint's count when it is hit. When any count reaches 0, |
| @value{GDBN} disables that breakpoint. If a breakpoint has an ignore |
| count (@pxref{Conditions, ,Break Conditions}), that will be |
| decremented to 0 before @var{count} is affected. |
| |
| @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{} |
| Enable the specified breakpoints to work once, then die. @value{GDBN} |
| deletes any of these breakpoints as soon as your program stops there. |
| Breakpoints set by the @code{tbreak} command start out in this state. |
| @end table |
| |
| @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is |
| @c confusing: tbreak is also initially enabled. |
| Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks, |
| ,Setting Breakpoints}), breakpoints that you set are initially enabled; |
| subsequently, they become disabled or enabled only when you use one of |
| the commands above. (The command @code{until} can set and delete a |
| breakpoint of its own, but it does not change the state of your other |
| breakpoints; see @ref{Continuing and Stepping, ,Continuing and |
| Stepping}.) |
| |
| @node Conditions |
| @subsection Break Conditions |
| @cindex conditional breakpoints |
| @cindex breakpoint conditions |
| |
| @c FIXME what is scope of break condition expr? Context where wanted? |
| @c in particular for a watchpoint? |
| The simplest sort of breakpoint breaks every time your program reaches a |
| specified place. You can also specify a @dfn{condition} for a |
| breakpoint. A condition is just a Boolean expression in your |
| programming language (@pxref{Expressions, ,Expressions}). A breakpoint with |
| a condition evaluates the expression each time your program reaches it, |
| and your program stops only if the condition is @emph{true}. |
| |
| This is the converse of using assertions for program validation; in that |
| situation, you want to stop when the assertion is violated---that is, |
| when the condition is false. In C, if you want to test an assertion expressed |
| by the condition @var{assert}, you should set the condition |
| @samp{! @var{assert}} on the appropriate breakpoint. |
| |
| Conditions are also accepted for watchpoints; you may not need them, |
| since a watchpoint is inspecting the value of an expression anyhow---but |
| it might be simpler, say, to just set a watchpoint on a variable name, |
| and specify a condition that tests whether the new value is an interesting |
| one. |
| |
| Break conditions can have side effects, and may even call functions in |
| your program. This can be useful, for example, to activate functions |
| that log program progress, or to use your own print functions to |
| format special data structures. The effects are completely predictable |
| unless there is another enabled breakpoint at the same address. (In |
| that case, @value{GDBN} might see the other breakpoint first and stop your |
| program without checking the condition of this one.) Note that |
| breakpoint commands are usually more convenient and flexible than break |
| conditions for the |
| purpose of performing side effects when a breakpoint is reached |
| (@pxref{Break Commands, ,Breakpoint Command Lists}). |
| |
| Breakpoint conditions can also be evaluated on the target's side if |
| the target supports it. Instead of evaluating the conditions locally, |
| @value{GDBN} encodes the expression into an agent expression |
| (@pxref{Agent Expressions}) suitable for execution on the target, |
| independently of @value{GDBN}. Global variables become raw memory |
| locations, locals become stack accesses, and so forth. |
| |
| In this case, @value{GDBN} will only be notified of a breakpoint trigger |
| when its condition evaluates to true. This mechanism may provide faster |
| response times depending on the performance characteristics of the target |
| since it does not need to keep @value{GDBN} informed about |
| every breakpoint trigger, even those with false conditions. |
| |
| Break conditions can be specified when a breakpoint is set, by using |
| @samp{if} in the arguments to the @code{break} command. @xref{Set |
| Breaks, ,Setting Breakpoints}. They can also be changed at any time |
| with the @code{condition} command. |
| |
| You can also use the @code{if} keyword with the @code{watch} command. |
| The @code{catch} command does not recognize the @code{if} keyword; |
| @code{condition} is the only way to impose a further condition on a |
| catchpoint. |
| |
| @table @code |
| @kindex condition |
| @item condition @var{bnum} @var{expression} |
| Specify @var{expression} as the break condition for breakpoint, |
| watchpoint, or catchpoint number @var{bnum}. After you set a condition, |
| breakpoint @var{bnum} stops your program only if the value of |
| @var{expression} is true (nonzero, in C). When you use |
| @code{condition}, @value{GDBN} checks @var{expression} immediately for |
| syntactic correctness, and to determine whether symbols in it have |
| referents in the context of your breakpoint. If @var{expression} uses |
| symbols not referenced in the context of the breakpoint, @value{GDBN} |
| prints an error message: |
| |
| @smallexample |
| No symbol "foo" in current context. |
| @end smallexample |
| |
| @noindent |
| @value{GDBN} does |
| not actually evaluate @var{expression} at the time the @code{condition} |
| command (or a command that sets a breakpoint with a condition, like |
| @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}. |
| |
| @item condition @var{bnum} |
| Remove the condition from breakpoint number @var{bnum}. It becomes |
| an ordinary unconditional breakpoint. |
| @end table |
| |
| @cindex ignore count (of breakpoint) |
| A special case of a breakpoint condition is to stop only when the |
| breakpoint has been reached a certain number of times. This is so |
| useful that there is a special way to do it, using the @dfn{ignore |
| count} of the breakpoint. Every breakpoint has an ignore count, which |
| is an integer. Most of the time, the ignore count is zero, and |
| therefore has no effect. But if your program reaches a breakpoint whose |
| ignore count is positive, then instead of stopping, it just decrements |
| the ignore count by one and continues. As a result, if the ignore count |
| value is @var{n}, the breakpoint does not stop the next @var{n} times |
| your program reaches it. |
| |
| @table @code |
| @kindex ignore |
| @item ignore @var{bnum} @var{count} |
| Set the ignore count of breakpoint number @var{bnum} to @var{count}. |
| The next @var{count} times the breakpoint is reached, your program's |
| execution does not stop; other than to decrement the ignore count, @value{GDBN} |
| takes no action. |
| |
| To make the breakpoint stop the next time it is reached, specify |
| a count of zero. |
| |
| When you use @code{continue} to resume execution of your program from a |
| breakpoint, you can specify an ignore count directly as an argument to |
| @code{continue}, rather than using @code{ignore}. @xref{Continuing and |
| Stepping,,Continuing and Stepping}. |
| |
| If a breakpoint has a positive ignore count and a condition, the |
| condition is not checked. Once the ignore count reaches zero, |
| @value{GDBN} resumes checking the condition. |
| |
| You could achieve the effect of the ignore count with a condition such |
| as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that |
| is decremented each time. @xref{Convenience Vars, ,Convenience |
| Variables}. |
| @end table |
| |
| Ignore counts apply to breakpoints, watchpoints, and catchpoints. |
| |
| |
| @node Break Commands |
| @subsection Breakpoint Command Lists |
| |
| @cindex breakpoint commands |
| You can give any breakpoint (or watchpoint or catchpoint) a series of |
| commands to execute when your program stops due to that breakpoint. For |
| example, you might want to print the values of certain expressions, or |
| enable other breakpoints. |
| |
| @table @code |
| @kindex commands |
| @kindex end@r{ (breakpoint commands)} |
| @item commands @r{[}@var{range}@dots{}@r{]} |
| @itemx @dots{} @var{command-list} @dots{} |
| @itemx end |
| Specify a list of commands for the given breakpoints. The commands |
| themselves appear on the following lines. Type a line containing just |
| @code{end} to terminate the commands. |
| |
| To remove all commands from a breakpoint, type @code{commands} and |
| follow it immediately with @code{end}; that is, give no commands. |
| |
| With no argument, @code{commands} refers to the last breakpoint, |
| watchpoint, or catchpoint set (not to the breakpoint most recently |
| encountered). If the most recent breakpoints were set with a single |
| command, then the @code{commands} will apply to all the breakpoints |
| set by that command. This applies to breakpoints set by |
| @code{rbreak}, and also applies when a single @code{break} command |
| creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous |
| Expressions}). |
| @end table |
| |
| Pressing @key{RET} as a means of repeating the last @value{GDBN} command is |
| disabled within a @var{command-list}. |
| |
| You can use breakpoint commands to start your program up again. Simply |
| use the @code{continue} command, or @code{step}, or any other command |
| that resumes execution. |
| |
| Any other commands in the command list, after a command that resumes |
| execution, are ignored. This is because any time you resume execution |
| (even with a simple @code{next} or @code{step}), you may encounter |
| another breakpoint---which could have its own command list, leading to |
| ambiguities about which list to execute. |
| |
| @kindex silent |
| If the first command you specify in a command list is @code{silent}, the |
| usual message about stopping at a breakpoint is not printed. This may |
| be desirable for breakpoints that are to print a specific message and |
| then continue. If none of the remaining commands print anything, you |
| see no sign that the breakpoint was reached. @code{silent} is |
| meaningful only at the beginning of a breakpoint command list. |
| |
| The commands @code{echo}, @code{output}, and @code{printf} allow you to |
| print precisely controlled output, and are often useful in silent |
| breakpoints. @xref{Output, ,Commands for Controlled Output}. |
| |
| For example, here is how you could use breakpoint commands to print the |
| value of @code{x} at entry to @code{foo} whenever @code{x} is positive. |
| |
| @smallexample |
| break foo if x>0 |
| commands |
| silent |
| printf "x is %d\n",x |
| cont |
| end |
| @end smallexample |
| |
| One application for breakpoint commands is to compensate for one bug so |
| you can test for another. Put a breakpoint just after the erroneous line |
| of code, give it a condition to detect the case in which something |
| erroneous has been done, and give it commands to assign correct values |
| to any variables that need them. End with the @code{continue} command |
| so that your program does not stop, and start with the @code{silent} |
| command so that no output is produced. Here is an example: |
| |
| @smallexample |
| break 403 |
| commands |
| silent |
| set x = y + 4 |
| cont |
| end |
| @end smallexample |
| |
| @node Dynamic Printf |
| @subsection Dynamic Printf |
| |
| @cindex dynamic printf |
| @cindex dprintf |
| The dynamic printf command @code{dprintf} combines a breakpoint with |
| formatted printing of your program's data to give you the effect of |
| inserting @code{printf} calls into your program on-the-fly, without |
| having to recompile it. |
| |
| In its most basic form, the output goes to the GDB console. However, |
| you can set the variable @code{dprintf-style} for alternate handling. |
| For instance, you can ask to format the output by calling your |
| program's @code{printf} function. This has the advantage that the |
| characters go to the program's output device, so they can recorded in |
| redirects to files and so forth. |
| |
| If you are doing remote debugging with a stub or agent, you can also |
| ask to have the printf handled by the remote agent. In addition to |
| ensuring that the output goes to the remote program's device along |
| with any other output the program might produce, you can also ask that |
| the dprintf remain active even after disconnecting from the remote |
| target. Using the stub/agent is also more efficient, as it can do |
| everything without needing to communicate with @value{GDBN}. |
| |
| @table @code |
| @kindex dprintf |
| @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}] |
| Whenever execution reaches @var{location}, print the values of one or |
| more @var{expressions} under the control of the string @var{template}. |
| To print several values, separate them with commas. |
| |
| @item set dprintf-style @var{style} |
| Set the dprintf output to be handled in one of several different |
| styles enumerated below. A change of style affects all existing |
| dynamic printfs immediately. (If you need individual control over the |
| print commands, simply define normal breakpoints with |
| explicitly-supplied command lists.) |
| |
| @item gdb |
| @kindex dprintf-style gdb |
| Handle the output using the @value{GDBN} @code{printf} command. |
| |
| @item call |
| @kindex dprintf-style call |
| Handle the output by calling a function in your program (normally |
| @code{printf}). |
| |
| @item agent |
| @kindex dprintf-style agent |
| Have the remote debugging agent (such as @code{gdbserver}) handle |
| the output itself. This style is only available for agents that |
| support running commands on the target. |
| |
| @item set dprintf-function @var{function} |
| Set the function to call if the dprintf style is @code{call}. By |
| default its value is @code{printf}. You may set it to any expression. |
| that @value{GDBN} can evaluate to a function, as per the @code{call} |
| command. |
| |
| @item set dprintf-channel @var{channel} |
| Set a ``channel'' for dprintf. If set to a non-empty value, |
| @value{GDBN} will evaluate it as an expression and pass the result as |
| a first argument to the @code{dprintf-function}, in the manner of |
| @code{fprintf} and similar functions. Otherwise, the dprintf format |
| string will be the first argument, in the manner of @code{printf}. |
| |
| As an example, if you wanted @code{dprintf} output to go to a logfile |
| that is a standard I/O stream assigned to the variable @code{mylog}, |
| you could do the following: |
| |
| @example |
| (gdb) set dprintf-style call |
| (gdb) set dprintf-function fprintf |
| (gdb) set dprintf-channel mylog |
| (gdb) dprintf 25,"at line 25, glob=%d\n",glob |
| Dprintf 1 at 0x123456: file main.c, line 25. |
| (gdb) info break |
| 1 dprintf keep y 0x00123456 in main at main.c:25 |
| call (void) fprintf (mylog,"at line 25, glob=%d\n",glob) |
| continue |
| (gdb) |
| @end example |
| |
| Note that the @code{info break} displays the dynamic printf commands |
| as normal breakpoint commands; you can thus easily see the effect of |
| the variable settings. |
| |
| @item set disconnected-dprintf on |
| @itemx set disconnected-dprintf off |
| @kindex set disconnected-dprintf |
| Choose whether @code{dprintf} commands should continue to run if |
| @value{GDBN} has disconnected from the target. This only applies |
| if the @code{dprintf-style} is @code{agent}. |
| |
| @item show disconnected-dprintf off |
| @kindex show disconnected-dprintf |
| Show the current choice for disconnected @code{dprintf}. |
| |
| @end table |
| |
| @value{GDBN} does not check the validity of function and channel, |
| relying on you to supply values that are meaningful for the contexts |
| in which they are being used. For instance, the function and channel |
| may be the values of local variables, but if that is the case, then |
| all enabled dynamic prints must be at locations within the scope of |
| those locals. If evaluation fails, @value{GDBN} will report an error. |
| |
| @node Save Breakpoints |
| @subsection How to save breakpoints to a file |
| |
| To save breakpoint definitions to a file use the @w{@code{save |
| breakpoints}} command. |
| |
| @table @code |
| @kindex save breakpoints |
| @cindex save breakpoints to a file for future sessions |
| @item save breakpoints [@var{filename}] |
| This command saves all current breakpoint definitions together with |
| their commands and ignore counts, into a file @file{@var{filename}} |
| suitable for use in a later debugging session. This includes all |
| types of breakpoints (breakpoints, watchpoints, catchpoints, |
| tracepoints). To read the saved breakpoint definitions, use the |
| @code{source} command (@pxref{Command Files}). Note that watchpoints |
| with expressions involving local variables may fail to be recreated |
| because it may not be possible to access the context where the |
| watchpoint is valid anymore. Because the saved breakpoint definitions |
| are simply a sequence of @value{GDBN} commands that recreate the |
| breakpoints, you can edit the file in your favorite editing program, |
| and remove the breakpoint definitions you're not interested in, or |
| that can no longer be recreated. |
| @end table |
| |
| @node Static Probe Points |
| @subsection Static Probe Points |
| |
| @cindex static probe point, SystemTap |
| @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands |
| for Statically Defined Tracing, and the probes are designed to have a tiny |
| runtime code and data footprint, and no dynamic relocations. They are |
| usable from assembly, C and C@t{++} languages. See |
| @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation} |
| for a good reference on how the @acronym{SDT} probes are implemented. |
| |
| Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/}) |
| @acronym{SDT} probes are supported on ELF-compatible systems. See |
| @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps} |
| for more information on how to add @code{SystemTap} @acronym{SDT} probes |
| in your applications. |
| |
| @cindex semaphores on static probe points |
| Some probes have an associated semaphore variable; for instance, this |
| happens automatically if you defined your probe using a DTrace-style |
| @file{.d} file. If your probe has a semaphore, @value{GDBN} will |
| automatically enable it when you specify a breakpoint using the |
| @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's |
| location by some other method (e.g., @code{break file:line}), then |
| @value{GDBN} will not automatically set the semaphore. |
| |
| You can examine the available static static probes using @code{info |
| probes}, with optional arguments: |
| |
| @table @code |
| @kindex info probes |
| @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]} |
| If given, @var{provider} is a regular expression used to match against provider |
| names when selecting which probes to list. If omitted, probes by all |
| probes from all providers are listed. |
| |
| If given, @var{name} is a regular expression to match against probe names |
| when selecting which probes to list. If omitted, probe names are not |
| considered when deciding whether to display them. |
| |
| If given, @var{objfile} is a regular expression used to select which |
| object files (executable or shared libraries) to examine. If not |
| given, all object files are considered. |
| |
| @item info probes all |
| List the available static probes, from all types. |
| @end table |
| |
| @vindex $_probe_arg@r{, convenience variable} |
| A probe may specify up to twelve arguments. These are available at the |
| point at which the probe is defined---that is, when the current PC is |
| at the probe's location. The arguments are available using the |
| convenience variables (@pxref{Convenience Vars}) |
| @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is |
| an integer of the appropriate size; types are not preserved. The |
| convenience variable @code{$_probe_argc} holds the number of arguments |
| at the current probe point. |
| |
| These variables are always available, but attempts to access them at |
| any location other than a probe point will cause @value{GDBN} to give |
| an error message. |
| |
| |
| @c @ifclear BARETARGET |
| @node Error in Breakpoints |
| @subsection ``Cannot insert breakpoints'' |
| |
| If you request too many active hardware-assisted breakpoints and |
| watchpoints, you will see this error message: |
| |
| @c FIXME: the precise wording of this message may change; the relevant |
| @c source change is not committed yet (Sep 3, 1999). |
| @smallexample |
| Stopped; cannot insert breakpoints. |
| You may have requested too many hardware breakpoints and watchpoints. |
| @end smallexample |
| |
| @noindent |
| This message is printed when you attempt to resume the program, since |
| only then @value{GDBN} knows exactly how many hardware breakpoints and |
| watchpoints it needs to insert. |
| |
| When this message is printed, you need to disable or remove some of the |
| hardware-assisted breakpoints and watchpoints, and then continue. |
| |
| @node Breakpoint-related Warnings |
| @subsection ``Breakpoint address adjusted...'' |
| @cindex breakpoint address adjusted |
| |
| Some processor architectures place constraints on the addresses at |
| which breakpoints may be placed. For architectures thus constrained, |
| @value{GDBN} will attempt to adjust the breakpoint's address to comply |
| with the constraints dictated by the architecture. |
| |
| One example of such an architecture is the Fujitsu FR-V. The FR-V is |
| a VLIW architecture in which a number of RISC-like instructions may be |
| bundled together for parallel execution. The FR-V architecture |
| constrains the location of a breakpoint instruction within such a |
| bundle to the instruction with the lowest address. @value{GDBN} |
| honors this constraint by adjusting a breakpoint's address to the |
| first in the bundle. |
| |
| It is not uncommon for optimized code to have bundles which contain |
| instructions from different source statements, thus it may happen that |
| a breakpoint's address will be adjusted from one source statement to |
| another. Since this adjustment may significantly alter @value{GDBN}'s |
| breakpoint related behavior from what the user expects, a warning is |
| printed when the breakpoint is first set and also when the breakpoint |
| is hit. |
| |
| A warning like the one below is printed when setting a breakpoint |
| that's been subject to address adjustment: |
| |
| @smallexample |
| warning: Breakpoint address adjusted from 0x00010414 to 0x00010410. |
| @end smallexample |
| |
| Such warnings are printed both for user settable and @value{GDBN}'s |
| internal breakpoints. If you see one of these warnings, you should |
| verify that a breakpoint set at the adjusted address will have the |
| desired affect. If not, the breakpoint in question may be removed and |
| other breakpoints may be set which will have the desired behavior. |
| E.g., it may be sufficient to place the breakpoint at a later |
| instruction. A conditional breakpoint may also be useful in some |
| cases to prevent the breakpoint from triggering too often. |
| |
| @value{GDBN} will also issue a warning when stopping at one of these |
| adjusted breakpoints: |
| |
| @smallexample |
| warning: Breakpoint 1 address previously adjusted from 0x00010414 |
| to 0x00010410. |
| @end smallexample |
| |
| When this warning is encountered, it may be too late to take remedial |
| action except in cases where the breakpoint is hit earlier or more |
| frequently than expected. |
| |
| @node Continuing and Stepping |
| @section Continuing and Stepping |
| |
| @cindex stepping |
| @cindex continuing |
| @cindex resuming execution |
| @dfn{Continuing} means resuming program execution until your program |
| completes normally. In contrast, @dfn{stepping} means executing just |
| one more ``step'' of your program, where ``step'' may mean either one |
| line of source code, or one machine instruction (depending on what |
| particular command you use). Either when continuing or when stepping, |
| your program may stop even sooner, due to a breakpoint or a signal. (If |
| it stops due to a signal, you may want to use @code{handle}, or use |
| @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.) |
| |
| @table @code |
| @kindex continue |
| @kindex c @r{(@code{continue})} |
| @kindex fg @r{(resume foreground execution)} |
| @item continue @r{[}@var{ignore-count}@r{]} |
| @itemx c @r{[}@var{ignore-count}@r{]} |
| @itemx fg @r{[}@var{ignore-count}@r{]} |
| Resume program execution, at the address where your program last stopped; |
| any breakpoints set at that address are bypassed. The optional argument |
| @var{ignore-count} allows you to specify a further number of times to |
| ignore a breakpoint at this location; its effect is like that of |
| @code{ignore} (@pxref{Conditions, ,Break Conditions}). |
| |
| The argument @var{ignore-count} is meaningful only when your program |
| stopped due to a breakpoint. At other times, the argument to |
| @code{continue} is ignored. |
| |
| The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the |
| debugged program is deemed to be the foreground program) are provided |
| purely for convenience, and have exactly the same behavior as |
| @code{continue}. |
| @end table |
| |
| To resume execution at a different place, you can use @code{return} |
| (@pxref{Returning, ,Returning from a Function}) to go back to the |
| calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a |
| Different Address}) to go to an arbitrary location in your program. |
| |
| A typical technique for using stepping is to set a breakpoint |
| (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the |
| beginning of the function or the section of your program where a problem |
| is believed to lie, run your program until it stops at that breakpoint, |
| and then step through the suspect area, examining the variables that are |
| interesting, until you see the problem happen. |
| |
| @table @code |
| @kindex step |
| @kindex s @r{(@code{step})} |
| @item step |
| Continue running your program until control reaches a different source |
| line, then stop it and return control to @value{GDBN}. This command is |
| abbreviated @code{s}. |
| |
| @quotation |
| @c "without debugging information" is imprecise; actually "without line |
| @c numbers in the debugging information". (gcc -g1 has debugging info but |
| @c not line numbers). But it seems complex to try to make that |
| @c distinction here. |
| @emph{Warning:} If you use the @code{step} command while control is |
| within a function that was compiled without debugging information, |
| execution proceeds until control reaches a function that does have |
| debugging information. Likewise, it will not step into a function which |
| is compiled without debugging information. To step through functions |
| without debugging information, use the @code{stepi} command, described |
| below. |
| @end quotation |
| |
| The @code{step} command only stops at the first instruction of a source |
| line. This prevents the multiple stops that could otherwise occur in |
| @code{switch} statements, @code{for} loops, etc. @code{step} continues |
| to stop if a function that has debugging information is called within |
| the line. In other words, @code{step} @emph{steps inside} any functions |
| called within the line. |
| |
| Also, the @code{step} command only enters a function if there is line |
| number information for the function. Otherwise it acts like the |
| @code{next} command. This avoids problems when using @code{cc -gl} |
| on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there |
| was any debugging information about the routine. |
| |
| @item step @var{count} |
| Continue running as in @code{step}, but do so @var{count} times. If a |
| breakpoint is reached, or a signal not related to stepping occurs before |
| @var{count} steps, stepping stops right away. |
| |
| @kindex next |
| @kindex n @r{(@code{next})} |
| @item next @r{[}@var{count}@r{]} |
| Continue to the next source line in the current (innermost) stack frame. |
| This is similar to @code{step}, but function calls that appear within |
| the line of code are executed without stopping. Execution stops when |
| control reaches a different line of code at the original stack level |
| that was executing when you gave the @code{next} command. This command |
| is abbreviated @code{n}. |
| |
| An argument @var{count} is a repeat count, as for @code{step}. |
| |
| |
| @c FIX ME!! Do we delete this, or is there a way it fits in with |
| @c the following paragraph? --- Vctoria |
| @c |
| @c @code{next} within a function that lacks debugging information acts like |
| @c @code{step}, but any function calls appearing within the code of the |
| @c function are executed without stopping. |
| |
| The @code{next} command only stops at the first instruction of a |
| source line. This prevents multiple stops that could otherwise occur in |
| @code{switch} statements, @code{for} loops, etc. |
| |
| @kindex set step-mode |
| @item set step-mode |
| @cindex functions without line info, and stepping |
| @cindex stepping into functions with no line info |
| @itemx set step-mode on |
| The @code{set step-mode on} command causes the @code{step} command to |
| stop at the first instruction of a function which contains no debug line |
| information rather than stepping over it. |
| |
| This is useful in cases where you may be interested in inspecting the |
| machine instructions of a function which has no symbolic info and do not |
| want @value{GDBN} to automatically skip over this function. |
| |
| @item set step-mode off |
| Causes the @code{step} command to step over any functions which contains no |
| debug information. This is the default. |
| |
| @item show step-mode |
| Show whether @value{GDBN} will stop in or step over functions without |
| source line debug information. |
| |
| @kindex finish |
| @kindex fin @r{(@code{finish})} |
| @item finish |
| Continue running until just after function in the selected stack frame |
| returns. Print the returned value (if any). This command can be |
| abbreviated as @code{fin}. |
| |
| Contrast this with the @code{return} command (@pxref{Returning, |
| ,Returning from a Function}). |
| |
| @kindex until |
| @kindex u @r{(@code{until})} |
| @cindex run until specified location |
| @item until |
| @itemx u |
| Continue running until a source line past the current line, in the |
| current stack frame, is reached. This command is used to avoid single |
| stepping through a loop more than once. It is like the @code{next} |
| command, except that when @code{until} encounters a jump, it |
| automatically continues execution until the program counter is greater |
| than the address of the jump. |
| |
| This means that when you reach the end of a loop after single stepping |
| though it, @code{until} makes your program continue execution until it |
| exits the loop. In contrast, a @code{next} command at the end of a loop |
| simply steps back to the beginning of the loop, which forces you to step |
| through the next iteration. |
| |
| @code{until} always stops your program if it attempts to exit the current |
| stack frame. |
| |
| @code{until} may produce somewhat counterintuitive results if the order |
| of machine code does not match the order of the source lines. For |
| example, in the following excerpt from a debugging session, the @code{f} |
| (@code{frame}) command shows that execution is stopped at line |
| @code{206}; yet when we use @code{until}, we get to line @code{195}: |
| |
| @smallexample |
| (@value{GDBP}) f |
| #0 main (argc=4, argv=0xf7fffae8) at m4.c:206 |
| 206 expand_input(); |
| (@value{GDBP}) until |
| 195 for ( ; argc > 0; NEXTARG) @{ |
| @end smallexample |
| |
| This happened because, for execution efficiency, the compiler had |
| generated code for the loop closure test at the end, rather than the |
| start, of the loop---even though the test in a C @code{for}-loop is |
| written before the body of the loop. The @code{until} command appeared |
| to step back to the beginning of the loop when it advanced to this |
| expression; however, it has not really gone to an earlier |
| statement---not in terms of the actual machine code. |
| |
| @code{until} with no argument works by means of single |
| instruction stepping, and hence is slower than @code{until} with an |
| argument. |
| |
| @item until @var{location} |
| @itemx u @var{location} |
| Continue running your program until either the specified location is |
| reached, or the current stack frame returns. @var{location} is any of |
| the forms described in @ref{Specify Location}. |
| This form of the command uses temporary breakpoints, and |
| hence is quicker than @code{until} without an argument. The specified |
| location is actually reached only if it is in the current frame. This |
| implies that @code{until} can be used to skip over recursive function |
| invocations. For instance in the code below, if the current location is |
| line @code{96}, issuing @code{until 99} will execute the program up to |
| line @code{99} in the same invocation of factorial, i.e., after the inner |
| invocations have returned. |
| |
| @smallexample |
| 94 int factorial (int value) |
| 95 @{ |
| 96 if (value > 1) @{ |
| 97 value *= factorial (value - 1); |
| 98 @} |
| 99 return (value); |
| 100 @} |
| @end smallexample |
| |
| |
| @kindex advance @var{location} |
| @item advance @var{location} |
| Continue running the program up to the given @var{location}. An argument is |
| required, which should be of one of the forms described in |
| @ref{Specify Location}. |
| Execution will also stop upon exit from the current stack |
| frame. This command is similar to @code{until}, but @code{advance} will |
| not skip over recursive function calls, and the target location doesn't |
| have to be in the same frame as the current one. |
| |
| |
| @kindex stepi |
| @kindex si @r{(@code{stepi})} |
| @item stepi |
| @itemx stepi @var{arg} |
| @itemx si |
| Execute one machine instruction, then stop and return to the debugger. |
| |
| It is often useful to do @samp{display/i $pc} when stepping by machine |
| instructions. This makes @value{GDBN} automatically display the next |
| instruction to be executed, each time your program stops. @xref{Auto |
| Display,, Automatic Display}. |
| |
| An argument is a repeat count, as in @code{step}. |
| |
| @need 750 |
| @kindex nexti |
| @kindex ni @r{(@code{nexti})} |
| @item nexti |
| @itemx nexti @var{arg} |
| @itemx ni |
| Execute one machine instruction, but if it is a function call, |
| proceed until the function returns. |
| |
| An argument is a repeat count, as in @code{next}. |
| @end table |
| |
| @node Skipping Over Functions and Files |
| @section Skipping Over Functions and Files |
| @cindex skipping over functions and files |
| |
| The program you are debugging may contain some functions which are |
| uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to |
| skip a function or all functions in a file when stepping. |
| |
| For example, consider the following C function: |
| |
| @smallexample |
| 101 int func() |
| 102 @{ |
| 103 foo(boring()); |
| 104 bar(boring()); |
| 105 @} |
| @end smallexample |
| |
| @noindent |
| Suppose you wish to step into the functions @code{foo} and @code{bar}, but you |
| are not interested in stepping through @code{boring}. If you run @code{step} |
| at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll |
| step over both @code{foo} and @code{boring}! |
| |
| One solution is to @code{step} into @code{boring} and use the @code{finish} |
| command to immediately exit it. But this can become tedious if @code{boring} |
| is called from many places. |
| |
| A more flexible solution is to execute @kbd{skip boring}. This instructs |
| @value{GDBN} never to step into @code{boring}. Now when you execute |
| @code{step} at line 103, you'll step over @code{boring} and directly into |
| @code{foo}. |
| |
| You can also instruct @value{GDBN} to skip all functions in a file, with, for |
| example, @code{skip file boring.c}. |
| |
| @table @code |
| @kindex skip function |
| @item skip @r{[}@var{linespec}@r{]} |
| @itemx skip function @r{[}@var{linespec}@r{]} |
| After running this command, the function named by @var{linespec} or the |
| function containing the line named by @var{linespec} will be skipped over when |
| stepping. @xref{Specify Location}. |
| |
| If you do not specify @var{linespec}, the function you're currently debugging |
| will be skipped. |
| |
| (If you have a function called @code{file} that you want to skip, use |
| @kbd{skip function file}.) |
| |
| @kindex skip file |
| @item skip file @r{[}@var{filename}@r{]} |
| After running this command, any function whose source lives in @var{filename} |
| will be skipped over when stepping. |
| |
| If you do not specify @var{filename}, functions whose source lives in the file |
| you're currently debugging will be skipped. |
| @end table |
| |
| Skips can be listed, deleted, disabled, and enabled, much like breakpoints. |
| These are the commands for managing your list of skips: |
| |
| @table @code |
| @kindex info skip |
| @item info skip @r{[}@var{range}@r{]} |
| Print details about the specified skip(s). If @var{range} is not specified, |
| print a table with details about all functions and files marked for skipping. |
| @code{info skip} prints the following information about each skip: |
| |
| @table @emph |
| @item Identifier |
| A number identifying this skip. |
| @item Type |
| The type of this skip, either @samp{function} or @samp{file}. |
| @item Enabled or Disabled |
| Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}. |
| @item Address |
| For function skips, this column indicates the address in memory of the function |
| being skipped. If you've set a function skip on a function which has not yet |
| been loaded, this field will contain @samp{<PENDING>}. Once a shared library |
| which has the function is loaded, @code{info skip} will show the function's |
| address here. |
| @item What |
| For file skips, this field contains the filename being skipped. For functions |
| skips, this field contains the function name and its line number in the file |
| where it is defined. |
| @end table |
| |
| @kindex skip delete |
| @item skip delete @r{[}@var{range}@r{]} |
| Delete the specified skip(s). If @var{range} is not specified, delete all |
| skips. |
| |
| @kindex skip enable |
| @item skip enable @r{[}@var{range}@r{]} |
| Enable the specified skip(s). If @var{range} is not specified, enable all |
| skips. |
| |
| @kindex skip disable |
| @item skip disable @r{[}@var{range}@r{]} |
| Disable the specified skip(s). If @var{range} is not specified, disable all |
| skips. |
| |
| @end table |
| |
| @node Signals |
| @section Signals |
| @cindex signals |
| |
| A signal is an asynchronous event that can happen in a program. The |
| operating system defines the possible kinds of signals, and gives each |
| kind a name and a number. For example, in Unix @code{SIGINT} is the |
| signal a program gets when you type an interrupt character (often @kbd{Ctrl-c}); |
| @code{SIGSEGV} is the signal a program gets from referencing a place in |
| memory far away from all the areas in use; @code{SIGALRM} occurs when |
| the alarm clock timer goes off (which happens only if your program has |
| requested an alarm). |
| |
| @cindex fatal signals |
| Some signals, including @code{SIGALRM}, are a normal part of the |
| functioning of your program. Others, such as @code{SIGSEGV}, indicate |
| errors; these signals are @dfn{fatal} (they kill your program immediately) if the |
| program has not specified in advance some other way to handle the signal. |
| @code{SIGINT} does not indicate an error in your program, but it is normally |
| fatal so it can carry out the purpose of the interrupt: to kill the program. |
| |
| @value{GDBN} has the ability to detect any occurrence of a signal in your |
| program. You can tell @value{GDBN} in advance what to do for each kind of |
| signal. |
| |
| @cindex handling signals |
| Normally, @value{GDBN} is set up to let the non-erroneous signals like |
| @code{SIGALRM} be silently passed to your program |
| (so as not to interfere with their role in the program's functioning) |
| but to stop your program immediately whenever an error signal happens. |
| You can change these settings with the @code{handle} command. |
| |
| @table @code |
| @kindex info signals |
| @kindex info handle |
| @item info signals |
| @itemx info handle |
| Print a table of all the kinds of signals and how @value{GDBN} has been told to |
| handle each one. You can use this to see the signal numbers of all |
| the defined types of signals. |
| |
| @item info signals @var{sig} |
| Similar, but print information only about the specified signal number. |
| |
| @code{info handle} is an alias for @code{info signals}. |
| |
| @kindex handle |
| @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]} |
| Change the way @value{GDBN} handles signal @var{signal}. @var{signal} |
| can be the number of a signal or its name (with or without the |
| @samp{SIG} at the beginning); a list of signal numbers of the form |
| @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the |
| known signals. Optional arguments @var{keywords}, described below, |
| say what change to make. |
| @end table |
| |
| @c @group |
| The keywords allowed by the @code{handle} command can be abbreviated. |
| Their full names are: |
| |
| @table @code |
| @item nostop |
| @value{GDBN} should not stop your program when this signal happens. It may |
| still print a message telling you that the signal has come in. |
| |
| @item stop |
| @value{GDBN} should stop your program when this signal happens. This implies |
| the @code{print} keyword as well. |
| |
| @item print |
| @value{GDBN} should print a message when this signal happens. |
| |
| @item noprint |
| @value{GDBN} should not mention the occurrence of the signal at all. This |
| implies the @code{nostop} keyword as well. |
| |
| @item pass |
| @itemx noignore |
| @value{GDBN} should allow your program to see this signal; your program |
| can handle the signal, or else it may terminate if the signal is fatal |
| and not handled. @code{pass} and @code{noignore} are synonyms. |
| |
| @item nopass |
| @itemx ignore |
| @value{GDBN} should not allow your program to see this signal. |
| @code{nopass} and @code{ignore} are synonyms. |
| @end table |
| @c @end group |
| |
| When a signal stops your program, the signal is not visible to the |
| program until you |
| continue. Your program sees the signal then, if @code{pass} is in |
| effect for the signal in question @emph{at that time}. In other words, |
| after @value{GDBN} reports a signal, you can use the @code{handle} |
| command with @code{pass} or @code{nopass} to control whether your |
| program sees that signal when you continue. |
| |
| The default is set to @code{nostop}, @code{noprint}, @code{pass} for |
| non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and |
| @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the |
| erroneous signals. |
| |
| You can also use the @code{signal} command to prevent your program from |
| seeing a signal, or cause it to see a signal it normally would not see, |
| or to give it any signal at any time. For example, if your program stopped |
| due to some sort of memory reference error, you might store correct |
| values into the erroneous variables and continue, hoping to see more |
| execution; but your program would probably terminate immediately as |
| a result of the fatal signal once it saw the signal. To prevent this, |
| you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your |
| Program a Signal}. |
| |
| @cindex extra signal information |
| @anchor{extra signal information} |
| |
| On some targets, @value{GDBN} can inspect extra signal information |
| associated with the intercepted signal, before it is actually |
| delivered to the program being debugged. This information is exported |
| by the convenience variable @code{$_siginfo}, and consists of data |
| that is passed by the kernel to the signal handler at the time of the |
| receipt of a signal. The data type of the information itself is |
| target dependent. You can see the data type using the @code{ptype |
| $_siginfo} command. On Unix systems, it typically corresponds to the |
| standard @code{siginfo_t} type, as defined in the @file{signal.h} |
| system header. |
| |
| Here's an example, on a @sc{gnu}/Linux system, printing the stray |
| referenced address that raised a segmentation fault. |
| |
| @smallexample |
| @group |
| (@value{GDBP}) continue |
| Program received signal SIGSEGV, Segmentation fault. |
| 0x0000000000400766 in main () |
| 69 *(int *)p = 0; |
| (@value{GDBP}) ptype $_siginfo |
| type = struct @{ |
| int si_signo; |
| int si_errno; |
| int si_code; |
| union @{ |
| int _pad[28]; |
| struct @{...@} _kill; |
| struct @{...@} _timer; |
| struct @{...@} _rt; |
| struct @{...@} _sigchld; |
| struct @{...@} _sigfault; |
| struct @{...@} _sigpoll; |
| @} _sifields; |
| @} |
| (@value{GDBP}) ptype $_siginfo._sifields._sigfault |
| type = struct @{ |
| void *si_addr; |
| @} |
| (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr |
| $1 = (void *) 0x7ffff7ff7000 |
| @end group |
| @end smallexample |
| |
| Depending on target support, @code{$_siginfo} may also be writable. |
| |
| @node Thread Stops |
| @section Stopping and Starting Multi-thread Programs |
| |
| @cindex stopped threads |
| @cindex threads, stopped |
| |
| @cindex continuing threads |
| @cindex threads, continuing |
| |
| @value{GDBN} supports debugging programs with multiple threads |
| (@pxref{Threads,, Debugging Programs with Multiple Threads}). There |
| are two modes of controlling execution of your program within the |
| debugger. In the default mode, referred to as @dfn{all-stop mode}, |
| when any thread in your program stops (for example, at a breakpoint |
| or while being stepped), all other threads in the program are also stopped by |
| @value{GDBN}. On some targets, @value{GDBN} also supports |
| @dfn{non-stop mode}, in which other threads can continue to run freely while |
| you examine the stopped thread in the debugger. |
| |
| @menu |
| * All-Stop Mode:: All threads stop when GDB takes control |
| * Non-Stop Mode:: Other threads continue to execute |
| * Background Execution:: Running your program asynchronously |
| * Thread-Specific Breakpoints:: Controlling breakpoints |
| * Interrupted System Calls:: GDB may interfere with system calls |
| * Observer Mode:: GDB does not alter program behavior |
| @end menu |
| |
| @node All-Stop Mode |
| @subsection All-Stop Mode |
| |
| @cindex all-stop mode |
| |
| In all-stop mode, whenever your program stops under @value{GDBN} for any reason, |
| @emph{all} threads of execution stop, not just the current thread. This |
| allows you to examine the overall state of the program, including |
| switching between threads, without worrying that things may change |
| underfoot. |
| |
| Conversely, whenever you restart the program, @emph{all} threads start |
| executing. @emph{This is true even when single-stepping} with commands |
| like @code{step} or @code{next}. |
| |
| In particular, @value{GDBN} cannot single-step all threads in lockstep. |
| Since thread scheduling is up to your debugging target's operating |
| system (not controlled by @value{GDBN}), other threads may |
| execute more than one statement while the current thread completes a |
| single step. Moreover, in general other threads stop in the middle of a |
| statement, rather than at a clean statement boundary, when the program |
| stops. |
| |
| You might even find your program stopped in another thread after |
| continuing or even single-stepping. This happens whenever some other |
| thread runs into a breakpoint, a signal, or an exception before the |
| first thread completes whatever you requested. |
| |
| @cindex automatic thread selection |
| @cindex switching threads automatically |
| @cindex threads, automatic switching |
| Whenever @value{GDBN} stops your program, due to a breakpoint or a |
| signal, it automatically selects the thread where that breakpoint or |
| signal happened. @value{GDBN} alerts you to the context switch with a |
| message such as @samp{[Switching to Thread @var{n}]} to identify the |
| thread. |
| |
| On some OSes, you can modify @value{GDBN}'s default behavior by |
| locking the OS scheduler to allow only a single thread to run. |
| |
| @table @code |
| @item set scheduler-locking @var{mode} |
| @cindex scheduler locking mode |
| @cindex lock scheduler |
| Set the scheduler locking mode. If it is @code{off}, then there is no |
| locking and any thread may run at any time. If @code{on}, then only the |
| current thread may run when the inferior is resumed. The @code{step} |
| mode optimizes for single-stepping; it prevents other threads |
| from preempting the current thread while you are stepping, so that |
| the focus of debugging does not change unexpectedly. |
| Other threads only rarely (or never) get a chance to run |
| when you step. They are more likely to run when you @samp{next} over a |
| function call, and they are completely free to run when you use commands |
| like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another |
| thread hits a breakpoint during its timeslice, @value{GDBN} does not change |
| the current thread away from the thread that you are debugging. |
| |
| @item show scheduler-locking |
| Display the current scheduler locking mode. |
| @end table |
| |
| @cindex resume threads of multiple processes simultaneously |
| By default, when you issue one of the execution commands such as |
| @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only |
| threads of the current inferior to run. For example, if @value{GDBN} |
| is attached to two inferiors, each with two threads, the |
| @code{continue} command resumes only the two threads of the current |
| inferior. This is useful, for example, when you debug a program that |
| forks and you want to hold the parent stopped (so that, for instance, |
| it doesn't run to exit), while you debug the child. In other |
| situations, you may not be interested in inspecting the current state |
| of any of the processes @value{GDBN} is attached to, and you may want |
| to resume them all until some breakpoint is hit. In the latter case, |
| you can instruct @value{GDBN} to allow all threads of all the |
| inferiors to run with the @w{@code{set schedule-multiple}} command. |
| |
| @table @code |
| @kindex set schedule-multiple |
| @item set schedule-multiple |
| Set the mode for allowing threads of multiple processes to be resumed |
| when an execution command is issued. When @code{on}, all threads of |
| all processes are allowed to run. When @code{off}, only the threads |
| of the current process are resumed. The default is @code{off}. The |
| @code{scheduler-locking} mode takes precedence when set to @code{on}, |
| or while you are stepping and set to @code{step}. |
| |
| @item show schedule-multiple |
| Display the current mode for resuming the execution of threads of |
| multiple processes. |
| @end table |
| |
| @node Non-Stop Mode |
| @subsection Non-Stop Mode |
| |
| @cindex non-stop mode |
| |
| @c This section is really only a place-holder, and needs to be expanded |
| @c with more details. |
| |
| For some multi-threaded targets, @value{GDBN} supports an optional |
| mode of operation in which you can examine stopped program threads in |
| the debugger while other threads continue to execute freely. This |
| minimizes intrusion when debugging live systems, such as programs |
| where some threads have real-time constraints or must continue to |
| respond to external events. This is referred to as @dfn{non-stop} mode. |
| |
| In non-stop mode, when a thread stops to report a debugging event, |
| @emph{only} that thread is stopped; @value{GDBN} does not stop other |
| threads as well, in contrast to the all-stop mode behavior. Additionally, |
| execution commands such as @code{continue} and @code{step} apply by default |
| only to the current thread in non-stop mode, rather than all threads as |
| in all-stop mode. This allows you to control threads explicitly in |
| ways that are not possible in all-stop mode --- for example, stepping |
| one thread while allowing others to run freely, stepping |
| one thread while holding all others stopped, or stepping several threads |
| independently and simultaneously. |
| |
| To enter non-stop mode, use this sequence of commands before you run |
| or attach to your program: |
| |
| @smallexample |
| # Enable the async interface. |
| set target-async 1 |
| |
| # If using the CLI, pagination breaks non-stop. |
| set pagination off |
| |
| # Finally, turn it on! |
| set non-stop on |
| @end smallexample |
| |
| You can use these commands to manipulate the non-stop mode setting: |
| |
| @table @code |
| @kindex set non-stop |
| @item set non-stop on |
| Enable selection of non-stop mode. |
| @item set non-stop off |
| Disable selection of non-stop mode. |
| @kindex show non-stop |
| @item show non-stop |
| Show the current non-stop enablement setting. |
| @end table |
| |
| Note these commands only reflect whether non-stop mode is enabled, |
| not whether the currently-executing program is being run in non-stop mode. |
| In particular, the @code{set non-stop} preference is only consulted when |
| @value{GDBN} starts or connects to the target program, and it is generally |
| not possible to switch modes once debugging has started. Furthermore, |
| since not all targets support non-stop mode, even when you have enabled |
| non-stop mode, @value{GDBN} may still fall back to all-stop operation by |
| default. |
| |
| In non-stop mode, all execution commands apply only to the current thread |
| by default. That is, @code{continue} only continues one thread. |
| To continue all threads, issue @code{continue -a} or @code{c -a}. |
| |
| You can use @value{GDBN}'s background execution commands |
| (@pxref{Background Execution}) to run some threads in the background |
| while you continue to examine or step others from @value{GDBN}. |
| The MI execution commands (@pxref{GDB/MI Program Execution}) are |
| always executed asynchronously in non-stop mode. |
| |
| Suspending execution is done with the @code{interrupt} command when |
| running in the background, or @kbd{Ctrl-c} during foreground execution. |
| In all-stop mode, this stops the whole process; |
| but in non-stop mode the interrupt applies only to the current thread. |
| To stop the whole program, use @code{interrupt -a}. |
| |
| Other execution commands do not currently support the @code{-a} option. |
| |
| In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make |
| that thread current, as it does in all-stop mode. This is because the |
| thread stop notifications are asynchronous with respect to @value{GDBN}'s |
| command interpreter, and it would be confusing if @value{GDBN} unexpectedly |
| changed to a different thread just as you entered a command to operate on the |
| previously current thread. |
| |
| @node Background Execution |
| @subsection Background Execution |
| |
| @cindex foreground execution |
| @cindex background execution |
| @cindex asynchronous execution |
| @cindex execution, foreground, background and asynchronous |
| |
| @value{GDBN}'s execution commands have two variants: the normal |
| foreground (synchronous) behavior, and a background |
| (asynchronous) behavior. In foreground execution, @value{GDBN} waits for |
| the program to report that some thread has stopped before prompting for |
| another command. In background execution, @value{GDBN} immediately gives |
| a command prompt so that you can issue other commands while your program runs. |
| |
| You need to explicitly enable asynchronous mode before you can use |
| background execution commands. You can use these commands to |
| manipulate the asynchronous mode setting: |
| |
| @table @code |
| @kindex set target-async |
| @item set target-async on |
| Enable asynchronous mode. |
| @item set target-async off |
| Disable asynchronous mode. |
| @kindex show target-async |
| @item show target-async |
| Show the current target-async setting. |
| @end table |
| |
| If the target doesn't support async mode, @value{GDBN} issues an error |
| message if you attempt to use the background execution commands. |
| |
| To specify background execution, add a @code{&} to the command. For example, |
| the background form of the @code{continue} command is @code{continue&}, or |
| just @code{c&}. The execution commands that accept background execution |
| are: |
| |
| @table @code |
| @kindex run& |
| @item run |
| @xref{Starting, , Starting your Program}. |
| |
| @item attach |
| @kindex attach& |
| @xref{Attach, , Debugging an Already-running Process}. |
| |
| @item step |
| @kindex step& |
| @xref{Continuing and Stepping, step}. |
| |
| @item stepi |
| @kindex stepi& |
| @xref{Continuing and Stepping, stepi}. |
| |
| @item next |
| @kindex next& |
| @xref{Continuing and Stepping, next}. |
| |
| @item nexti |
| @kindex nexti& |
| @xref{Continuing and Stepping, nexti}. |
| |
| @item continue |
| @kindex continue& |
| @xref{Continuing and Stepping, continue}. |
| |
| @item finish |
| @kindex finish& |
| @xref{Continuing and Stepping, finish}. |
| |
| @item until |
| @kindex until& |
| @xref{Continuing and Stepping, until}. |
| |
| @end table |
| |
| Background execution is especially useful in conjunction with non-stop |
| mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}. |
| However, you can also use these commands in the normal all-stop mode with |
| the restriction that you cannot issue another execution command until the |
| previous one finishes. Examples of commands that are valid in all-stop |
| mode while the program is running include @code{help} and @code{info break}. |
| |
| You can interrupt your program while it is running in the background by |
| using the @code{interrupt} command. |
| |
| @table @code |
| @kindex interrupt |
| @item interrupt |
| @itemx interrupt -a |
| |
| Suspend execution of the running program. In all-stop mode, |
| @code{interrupt} stops the whole process, but in non-stop mode, it stops |
| only the current thread. To stop the whole program in non-stop mode, |
| use @code{interrupt -a}. |
| @end table |
| |
| @node Thread-Specific Breakpoints |
| @subsection Thread-Specific Breakpoints |
| |
| When your program has multiple threads (@pxref{Threads,, Debugging |
| Programs with Multiple Threads}), you can choose whether to set |
| breakpoints on all threads, or on a particular thread. |
| |
| @table @code |
| @cindex breakpoints and threads |
| @cindex thread breakpoints |
| @kindex break @dots{} thread @var{threadno} |
| @item break @var{linespec} thread @var{threadno} |
| @itemx break @var{linespec} thread @var{threadno} if @dots{} |
| @var{linespec} specifies source lines; there are several ways of |
| writing them (@pxref{Specify Location}), but the effect is always to |
| specify some source line. |
| |
| Use the qualifier @samp{thread @var{threadno}} with a breakpoint command |
| to specify that you only want @value{GDBN} to stop the program when a |
| particular thread reaches this breakpoint. @var{threadno} is one of the |
| numeric thread identifiers assigned by @value{GDBN}, shown in the first |
| column of the @samp{info threads} display. |
| |
| If you do not specify @samp{thread @var{threadno}} when you set a |
| breakpoint, the breakpoint applies to @emph{all} threads of your |
| program. |
| |
| You can use the @code{thread} qualifier on conditional breakpoints as |
| well; in this case, place @samp{thread @var{threadno}} before or |
| after the breakpoint condition, like this: |
| |
| @smallexample |
| (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim |
| @end smallexample |
| |
| @end table |
| |
| @node Interrupted System Calls |
| @subsection Interrupted System Calls |
| |
| @cindex thread breakpoints and system calls |
| @cindex system calls and thread breakpoints |
| @cindex premature return from system calls |
| There is an unfortunate side effect when using @value{GDBN} to debug |
| multi-threaded programs. If one thread stops for a |
| breakpoint, or for some other reason, and another thread is blocked in a |
| system call, then the system call may return prematurely. This is a |
| consequence of the interaction between multiple threads and the signals |
| that @value{GDBN} uses to implement breakpoints and other events that |
| stop execution. |
| |
| To handle this problem, your program should check the return value of |
| each system call and react appropriately. This is good programming |
| style anyways. |
| |
| For example, do not write code like this: |
| |
| @smallexample |
| sleep (10); |
| @end smallexample |
| |
| The call to @code{sleep} will return early if a different thread stops |
| at a breakpoint or for some other reason. |
| |
| Instead, write this: |
| |
| @smallexample |
| int unslept = 10; |
| while (unslept > 0) |
| unslept = sleep (unslept); |
| @end smallexample |
| |
| A system call is allowed to return early, so the system is still |
| conforming to its specification. But @value{GDBN} does cause your |
| multi-threaded program to behave differently than it would without |
| @value{GDBN}. |
| |
| Also, @value{GDBN} uses internal breakpoints in the thread library to |
| monitor certain events such as thread creation and thread destruction. |
| When such an event happens, a system call in another thread may return |
| prematurely, even though your program does not appear to stop. |
| |
| @node Observer Mode |
| @subsection Observer Mode |
| |
| If you want to build on non-stop mode and observe program behavior |
| without any chance of disruption by @value{GDBN}, you can set |
| variables to disable all of the debugger's attempts to modify state, |
| whether by writing memory, inserting breakpoints, etc. These operate |
| at a low level, intercepting operations from all commands. |
| |
| When all of these are set to @code{off}, then @value{GDBN} is said to |
| be @dfn{observer mode}. As a convenience, the variable |
| @code{observer} can be set to disable these, plus enable non-stop |
| mode. |
| |
| Note that @value{GDBN} will not prevent you from making nonsensical |
| combinations of these settings. For instance, if you have enabled |
| @code{may-insert-breakpoints} but disabled @code{may-write-memory}, |
| then breakpoints that work by writing trap instructions into the code |
| stream will still not be able to be placed. |
| |
| @table @code |
| |
| @kindex observer |
| @item set observer on |
| @itemx set observer off |
| When set to @code{on}, this disables all the permission variables |
| below (except for @code{insert-fast-tracepoints}), plus enables |
| non-stop debugging. Setting this to @code{off} switches back to |
| normal debugging, though remaining in non-stop mode. |
| |
| @item show observer |
| Show whether observer mode is on or off. |
| |
| @kindex may-write-registers |
| @item set may-write-registers on |
| @itemx set may-write-registers off |
| This controls whether @value{GDBN} will attempt to alter the values of |
| registers, such as with assignment expressions in @code{print}, or the |
| @code{jump} command. It defaults to @code{on}. |
| |
| @item show may-write-registers |
| Show the current permission to write registers. |
| |
| @kindex may-write-memory |
| @item set may-write-memory on |
| @itemx set may-write-memory off |
| This controls whether @value{GDBN} will attempt to alter the contents |
| of memory, such as with assignment expressions in @code{print}. It |
| defaults to @code{on}. |
| |
| @item show may-write-memory |
| Show the current permission to write memory. |
| |
| @kindex may-insert-breakpoints |
| @item set may-insert-breakpoints on |
| @itemx set may-insert-breakpoints off |
| This controls whether @value{GDBN} will attempt to insert breakpoints. |
| This affects all breakpoints, including internal breakpoints defined |
| by @value{GDBN}. It defaults to @code{on}. |
| |
| @item show may-insert-breakpoints |
| Show the current permission to insert breakpoints. |
| |
| @kindex may-insert-tracepoints |
| @item set may-insert-tracepoints on |
| @itemx set may-insert-tracepoints off |
| This controls whether @value{GDBN} will attempt to insert (regular) |
| tracepoints at the beginning of a tracing experiment. It affects only |
| non-fast tracepoints, fast tracepoints being under the control of |
| @code{may-insert-fast-tracepoints}. It defaults to @code{on}. |
| |
| @item show may-insert-tracepoints |
| Show the current permission to insert tracepoints. |
| |
| @kindex may-insert-fast-tracepoints |
| @item set may-insert-fast-tracepoints on |
| @itemx set may-insert-fast-tracepoints off |
| This controls whether @value{GDBN} will attempt to insert fast |
| tracepoints at the beginning of a tracing experiment. It affects only |
| fast tracepoints, regular (non-fast) tracepoints being under the |
| control of @code{may-insert-tracepoints}. It defaults to @code{on}. |
| |
| @item show may-insert-fast-tracepoints |
| Show the current permission to insert fast tracepoints. |
| |
| @kindex may-interrupt |
| @item set may-interrupt on |
| @itemx set may-interrupt off |
| This controls whether @value{GDBN} will attempt to interrupt or stop |
| program execution. When this variable is @code{off}, the |
| @code{interrupt} command will have no effect, nor will |
| @kbd{Ctrl-c}. It defaults to @code{on}. |
| |
| @item show may-interrupt |
| Show the current permission to interrupt or stop the program. |
| |
| @end table |
| |
| @node Reverse Execution |
| @chapter Running programs backward |
| @cindex reverse execution |
| @cindex running programs backward |
| |
| When you are debugging a program, it is not unusual to realize that |
| you have gone too far, and some event of interest has already happened. |
| If the target environment supports it, @value{GDBN} can allow you to |
| ``rewind'' the program by running it backward. |
| |
| A target environment that supports reverse execution should be able |
| to ``undo'' the changes in machine state that have taken place as the |
| program was executing normally. Variables, registers etc.@: should |
| revert to their previous values. Obviously this requires a great |
| deal of sophistication on the part of the target environment; not |
| all target environments can support reverse execution. |
| |
| When a program is executed in reverse, the instructions that |
| have most recently been executed are ``un-executed'', in reverse |
| order. The program counter runs backward, following the previous |
| thread of execution in reverse. As each instruction is ``un-executed'', |
| the values of memory and/or registers that were changed by that |
| instruction are reverted to their previous states. After executing |
| a piece of source code in reverse, all side effects of that code |
| should be ``undone'', and all variables should be returned to their |
| prior values@footnote{ |
| Note that some side effects are easier to undo than others. For instance, |
| memory and registers are relatively easy, but device I/O is hard. Some |
| targets may be able undo things like device I/O, and some may not. |
| |
| The contract between @value{GDBN} and the reverse executing target |
| requires only that the target do something reasonable when |
| @value{GDBN} tells it to execute backwards, and then report the |
| results back to @value{GDBN}. Whatever the target reports back to |
| @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN} |
| assumes that the memory and registers that the target reports are in a |
| consistant state, but @value{GDBN} accepts whatever it is given. |
| }. |
| |
| If you are debugging in a target environment that supports |
| reverse execution, @value{GDBN} provides the following commands. |
| |
| @table @code |
| @kindex reverse-continue |
| @kindex rc @r{(@code{reverse-continue})} |
| @item reverse-continue @r{[}@var{ignore-count}@r{]} |
| @itemx rc @r{[}@var{ignore-count}@r{]} |
| Beginning at the point where your program last stopped, start executing |
| in reverse. Reverse execution will stop for breakpoints and synchronous |
| exceptions (signals), just like normal execution. Behavior of |
| asynchronous signals depends on the target environment. |
| |
| @kindex reverse-step |
| @kindex rs @r{(@code{step})} |
| @item reverse-step @r{[}@var{count}@r{]} |
| Run the program backward until control reaches the start of a |
| different source line; then stop it, and return control to @value{GDBN}. |
| |
| Like the @code{step} command, @code{reverse-step} will only stop |
| at the beginning of a source line. It ``un-executes'' the previously |
| executed source line. If the previous source line included calls to |
| debuggable functions, @code{reverse-step} will step (backward) into |
| the called function, stopping at the beginning of the @emph{last} |
| statement in the called function (typically a return statement). |
| |
| Also, as with the @code{step} command, if non-debuggable functions are |
| called, @code{reverse-step} will run thru them backward without stopping. |
| |
| @kindex reverse-stepi |
| @kindex rsi @r{(@code{reverse-stepi})} |
| @item reverse-stepi @r{[}@var{count}@r{]} |
| Reverse-execute one machine instruction. Note that the instruction |
| to be reverse-executed is @emph{not} the one pointed to by the program |
| counter, but the instruction executed prior to that one. For instance, |
| if the last instruction was a jump, @code{reverse-stepi} will take you |
| back from the destination of the jump to the jump instruction itself. |
| |
| @kindex reverse-next |
| @kindex rn @r{(@code{reverse-next})} |
| @item reverse-next @r{[}@var{count}@r{]} |
| Run backward to the beginning of the previous line executed in |
| the current (innermost) stack frame. If the line contains function |
| calls, they will be ``un-executed'' without stopping. Starting from |
| the first line of a function, @code{reverse-next} will take you back |
| to the caller of that function, @emph{before} the function was called, |
| just as the normal @code{next} command would take you from the last |
| line of a function back to its return to its caller |
| @footnote{Unless the code is too heavily optimized.}. |
| |
| @kindex reverse-nexti |
| @kindex rni @r{(@code{reverse-nexti})} |
| @item reverse-nexti @r{[}@var{count}@r{]} |
| Like @code{nexti}, @code{reverse-nexti} executes a single instruction |
| in reverse, except that called functions are ``un-executed'' atomically. |
| That is, if the previously executed instruction was a return from |
| another function, @code{reverse-nexti} will continue to execute |
| in reverse until the call to that function (from the current stack |
| frame) is reached. |
| |
| @kindex reverse-finish |
| @item reverse-finish |
| Just as the @code{finish} command takes you to the point where the |
| current function returns, @code{reverse-finish} takes you to the point |
| where it was called. Instead of ending up at the end of the current |
| function invocation, you end up at the beginning. |
| |
| @kindex set exec-direction |
| @item set exec-direction |
| Set the direction of target execution. |
| @item set exec-direction reverse |
| @cindex execute forward or backward in time |
| @value{GDBN} will perform all execution commands in reverse, until the |
| exec-direction mode is changed to ``forward''. Affected commands include |
| @code{step, stepi, next, nexti, continue, and finish}. The @code{return} |
| command cannot be used in reverse mode. |
| @item set exec-direction forward |
| @value{GDBN} will perform all execution commands in the normal fashion. |
| This is the default. |
| @end table |
| |
| |
| @node Process Record and Replay |
| @chapter Recording Inferior's Execution and Replaying It |
| @cindex process record and replay |
| @cindex recording inferior's execution and replaying it |
| |
| On some platforms, @value{GDBN} provides a special @dfn{process record |
| and replay} target that can record a log of the process execution, and |
| replay it later with both forward and reverse execution commands. |
| |
| @cindex replay mode |
| When this target is in use, if the execution log includes the record |
| for the next instruction, @value{GDBN} will debug in @dfn{replay |
| mode}. In the replay mode, the inferior does not really execute code |
| instructions. Instead, all the events that normally happen during |
| code execution are taken from the execution log. While code is not |
| really executed in replay mode, the values of registers (including the |
| program counter register) and the memory of the inferior are still |
| changed as they normally would. Their contents are taken from the |
| execution log. |
| |
| @cindex record mode |
| If the record for the next instruction is not in the execution log, |
| @value{GDBN} will debug in @dfn{record mode}. In this mode, the |
| inferior executes normally, and @value{GDBN} records the execution log |
| for future replay. |
| |
| The process record and replay target supports reverse execution |
| (@pxref{Reverse Execution}), even if the platform on which the |
| inferior runs does not. However, the reverse execution is limited in |
| this case by the range of the instructions recorded in the execution |
| log. In other words, reverse execution on platforms that don't |
| support it directly can only be done in the replay mode. |
| |
| When debugging in the reverse direction, @value{GDBN} will work in |
| replay mode as long as the execution log includes the record for the |
| previous instruction; otherwise, it will work in record mode, if the |
| platform supports reverse execution, or stop if not. |
| |
| For architecture environments that support process record and replay, |
| @value{GDBN} provides the following commands: |
| |
| @table @code |
| @kindex target record |
| @kindex record |
| @kindex rec |
| @item target record |
| This command starts the process record and replay target. The process |
| record and replay target can only debug a process that is already |
| running. Therefore, you need first to start the process with the |
| @kbd{run} or @kbd{start} commands, and then start the recording with |
| the @kbd{target record} command. |
| |
| Both @code{record} and @code{rec} are aliases of @code{target record}. |
| |
| @cindex displaced stepping, and process record and replay |
| Displaced stepping (@pxref{Maintenance Commands,, displaced stepping}) |
| will be automatically disabled when process record and replay target |
| is started. That's because the process record and replay target |
| doesn't support displaced stepping. |
| |
| @cindex non-stop mode, and process record and replay |
| @cindex asynchronous execution, and process record and replay |
| If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in |
| the asynchronous execution mode (@pxref{Background Execution}), the |
| process record and replay target cannot be started because it doesn't |
| support these two modes. |
| |
| @kindex record stop |
| @kindex rec s |
| @item record stop |
| Stop the process record and replay target. When process record and |
| replay target stops, the entire execution log will be deleted and the |
| inferior will either be terminated, or will remain in its final state. |
| |
| When you stop the process record and replay target in record mode (at |
| the end of the execution log), the inferior will be stopped at the |
| next instruction that would have been recorded. In other words, if |
| you record for a while and then stop recording, the inferior process |
| will be left in the same state as if the recording never happened. |
| |
| On the other hand, if the process record and replay target is stopped |
| while in replay mode (that is, not at the end of the execution log, |
| but at some earlier point), the inferior process will become ``live'' |
| at that earlier state, and it will then be possible to continue the |
| usual ``live'' debugging of the process from that state. |
| |
| When the inferior process exits, or @value{GDBN} detaches from it, |
| process record and replay target will automatically stop itself. |
| |
| @kindex record save |
| @item record save @var{filename} |
| Save the execution log to a file @file{@var{filename}}. |
| Default filename is @file{gdb_record.@var{process_id}}, where |
| @var{process_id} is the process ID of the inferior. |
| |
| @kindex record restore |
| @item record restore @var{filename} |
| Restore the execution log from a file @file{@var{filename}}. |
| File must have been created with @code{record save}. |
| |
| @kindex set record insn-number-max |
| @item set record insn-number-max @var{limit} |
| Set the limit of instructions to be recorded. Default value is 200000. |
| |
| If @var{limit} is a positive number, then @value{GDBN} will start |
| deleting instructions from the log once the number of the record |
| instructions becomes greater than @var{limit}. For every new recorded |
| instruction, @value{GDBN} will delete the earliest recorded |
| instruction to keep the number of recorded instructions at the limit. |
| (Since deleting recorded instructions loses information, @value{GDBN} |
| lets you control what happens when the limit is reached, by means of |
| the @code{stop-at-limit} option, described below.) |
| |
| If @var{limit} is zero, @value{GDBN} will never delete recorded |
| instructions from the execution log. The number of recorded |
| instructions is unlimited in this case. |
| |
| @kindex show record insn-number-max |
| @item show record insn-number-max |
| Show the limit of instructions to be recorded. |
| |
| @kindex set record stop-at-limit |
| @item set record stop-at-limit |
| Control the behavior when the number of recorded instructions reaches |
| the limit. If ON (the default), @value{GDBN} will stop when the limit |
| is reached for the first time and ask you whether you want to stop the |
| inferior or continue running it and recording the execution log. If |
| you decide to continue recording, each new recorded instruction will |
| cause the oldest one to be deleted. |
| |
| If this option is OFF, @value{GDBN} will automatically delete the |
| oldest record to make room for each new one, without asking. |
| |
| @kindex show record stop-at-limit |
| @item show record stop-at-limit |
| Show the current setting of @code{stop-at-limit}. |
| |
| @kindex set record memory-query |
| @item set record memory-query |
| Control the behavior when @value{GDBN} is unable to record memory |
| changes caused by an instruction. If ON, @value{GDBN} will query |
| whether to stop the inferior in that case. |
| |
| If this option is OFF (the default), @value{GDBN} will automatically |
| ignore the effect of such instructions on memory. Later, when |
| @value{GDBN} replays this execution log, it will mark the log of this |
| instruction as not accessible, and it will not affect the replay |
| results. |
| |
| @kindex show record memory-query |
| @item show record memory-query |
| Show the current setting of @code{memory-query}. |
| |
| @kindex info record |
| @item info record |
| Show various statistics about the state of process record and its |
| in-memory execution log buffer, including: |
| |
| @itemize @bullet |
| @item |
| Whether in record mode or replay mode. |
| @item |
| Lowest recorded instruction number (counting from when the current execution log started recording instructions). |
| @item |
| Highest recorded instruction number. |
| @item |
| Current instruction about to be replayed (if in replay mode). |
| @item |
| Number of instructions contained in the execution log. |
| @item |
| Maximum number of instructions that may be contained in the execution log. |
| @end itemize |
| |
| @kindex record delete |
| @kindex rec del |
| @item record delete |
| When record target runs in replay mode (``in the past''), delete the |
| subsequent execution log and begin to record a new execution log starting |
| from the current address. This means you will abandon the previously |
| recorded ``future'' and begin recording a new ``future''. |
| @end table |
| |
| |
| @node Stack |
| @chapter Examining the Stack |
| |
| When your program has stopped, the first thing you need to know is where it |
| stopped and how it got there. |
| |
| @cindex call stack |
| Each time your program performs a function call, information about the call |
| is generated. |
| That information includes the location of the call in your program, |
| the arguments of the call, |
| and the local variables of the function being called. |
| The information is saved in a block of data called a @dfn{stack frame}. |
| The stack frames are allocated in a region of memory called the @dfn{call |
| stack}. |
| |
| When your program stops, the @value{GDBN} commands for examining the |
| stack allow you to see all of this information. |
| |
| @cindex selected frame |
| One of the stack frames is @dfn{selected} by @value{GDBN} and many |
| @value{GDBN} commands refer implicitly to the selected frame. In |
| particular, whenever you ask @value{GDBN} for the value of a variable in |
| your program, the value is found in the selected frame. There are |
| special @value{GDBN} commands to select whichever frame you are |
| interested in. @xref{Selection, ,Selecting a Frame}. |
| |
| When your program stops, @value{GDBN} automatically selects the |
| currently executing frame and describes it briefly, similar to the |
| @code{frame} command (@pxref{Frame Info, ,Information about a Frame}). |
| |
| @menu |
| * Frames:: Stack frames |
| * Backtrace:: Backtraces |
| * Selection:: Selecting a frame |
| * Frame Info:: Information on a frame |
| |
| @end menu |
| |
| @node Frames |
| @section Stack Frames |
| |
| @cindex frame, definition |
| @cindex stack frame |
| The call stack is divided up into contiguous pieces called @dfn{stack |
| frames}, or @dfn{frames} for short; each frame is the data associated |
| with one call to one function. The frame contains the arguments given |
| to the function, the function's local variables, and the address at |
| which the function is executing. |
| |
| @cindex initial frame |
| @cindex outermost frame |
| @cindex innermost frame |
| When your program is started, the stack has only one frame, that of the |
| function @code{main}. This is called the @dfn{initial} frame or the |
| @dfn{outermost} frame. Each time a function is called, a new frame is |
| made. Each time a function returns, the frame for that function invocation |
| is eliminated. If a function is recursive, there can be many frames for |
| the same function. The frame for the function in which execution is |
| actually occurring is called the @dfn{innermost} frame. This is the most |
| recently created of all the stack frames that still exist. |
| |
| @cindex frame pointer |
| Inside your program, stack frames are identified by their addresses. A |
| stack frame consists of many bytes, each of which has its own address; each |
| kind of computer has a convention for choosing one byte whose |
| address serves as the address of the frame. Usually this address is kept |
| in a register called the @dfn{frame pointer register} |
| (@pxref{Registers, $fp}) while execution is going on in that frame. |
| |
| @cindex frame number |
| @value{GDBN} assigns numbers to all existing stack frames, starting with |
| zero for the innermost frame, one for the frame that called it, |
| and so on upward. These numbers do not really exist in your program; |
| they are assigned by @value{GDBN} to give you a way of designating stack |
| frames in @value{GDBN} commands. |
| |
| @c The -fomit-frame-pointer below perennially causes hbox overflow |
| @c underflow problems. |
| @cindex frameless execution |
| Some compilers provide a way to compile functions so that they operate |
| without stack frames. (For example, the @value{NGCC} option |
| @smallexample |
| @samp{-fomit-frame-pointer} |
| @end smallexample |
| generates functions without a frame.) |
| This is occasionally done with heavily used library functions to save |
| the frame setup time. @value{GDBN} has limited facilities for dealing |
| with these function invocations. If the innermost function invocation |
| has no stack frame, @value{GDBN} nevertheless regards it as though |
| it had a separate frame, which is numbered zero as usual, allowing |
| correct tracing of the function call chain. However, @value{GDBN} has |
| no provision for frameless functions elsewhere in the stack. |
| |
| @table @code |
| @kindex frame@r{, command} |
| @cindex current stack frame |
| @item frame @var{args} |
| The @code{frame} command allows you to move from one stack frame to another, |
| and to print the stack frame you select. @var{args} may be either the |
| address of the frame or the stack frame number. Without an argument, |
| @code{frame} prints the current stack frame. |
| |
| @kindex select-frame |
| @cindex selecting frame silently |
| @item select-frame |
| The @code{select-frame} command allows you to move from one stack frame |
| to another without printing the frame. This is the silent version of |
| @code{frame}. |
| @end table |
| |
| @node Backtrace |
| @section Backtraces |
| |
| @cindex traceback |
| @cindex call stack traces |
| A backtrace is a summary of how your program got where it is. It shows one |
| line per frame, for many frames, starting with the currently executing |
| frame (frame zero), followed by its caller (frame one), and on up the |
| stack. |
| |
| @table @code |
| @kindex backtrace |
| @kindex bt @r{(@code{backtrace})} |
| @item backtrace |
| @itemx bt |
| Print a backtrace of the entire stack: one line per frame for all |
| frames in the stack. |
| |
| You can stop the backtrace at any time by typing the system interrupt |
| character, normally @kbd{Ctrl-c}. |
| |
| @item backtrace @var{n} |
| @itemx bt @var{n} |
| Similar, but print only the innermost @var{n} frames. |
| |
| @item backtrace -@var{n} |
| @itemx bt -@var{n} |
| Similar, but print only the outermost @var{n} frames. |
| |
| @item backtrace full |
| @itemx bt full |
| @itemx bt full @var{n} |
| @itemx bt full -@var{n} |
| Print the values of the local variables also. @var{n} specifies the |
| number of frames to print, as described above. |
| @end table |
| |
| @kindex where |
| @kindex info stack |
| The names @code{where} and @code{info stack} (abbreviated @code{info s}) |
| are additional aliases for @code{backtrace}. |
| |
| @cindex multiple threads, backtrace |
| In a multi-threaded program, @value{GDBN} by default shows the |
| backtrace only for the current thread. To display the backtrace for |
| several or all of the threads, use the command @code{thread apply} |
| (@pxref{Threads, thread apply}). For example, if you type @kbd{thread |
| apply all backtrace}, @value{GDBN} will display the backtrace for all |
| the threads; this is handy when you debug a core dump of a |
| multi-threaded program. |
| |
| Each line in the backtrace shows the frame number and the function name. |
| The program counter value is also shown---unless you use @code{set |
| print address off}. The backtrace also shows the source file name and |
| line number, as well as the arguments to the function. The program |
| counter value is omitted if it is at the beginning of the code for that |
| line number. |
| |
| Here is an example of a backtrace. It was made with the command |
| @samp{bt 3}, so it shows the innermost three frames. |
| |
| @smallexample |
| @group |
| #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) |
| at builtin.c:993 |
| #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242 |
| #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08) |
| at macro.c:71 |
| (More stack frames follow...) |
| @end group |
| @end smallexample |
| |
| @noindent |
| The display for frame zero does not begin with a program counter |
| value, indicating that your program has stopped at the beginning of the |
| code for line @code{993} of @code{builtin.c}. |
| |
| @noindent |
| The value of parameter @code{data} in frame 1 has been replaced by |
| @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter |
| only if it is a scalar (integer, pointer, enumeration, etc). See command |
| @kbd{set print frame-arguments} in @ref{Print Settings} for more details |
| on how to configure the way function parameter values are printed. |
| |
| @cindex optimized out, in backtrace |
| @cindex function call arguments, optimized out |
| If your program was compiled with optimizations, some compilers will |
| optimize away arguments passed to functions if those arguments are |
| never used after the call. Such optimizations generate code that |
| passes arguments through registers, but doesn't store those arguments |
| in the stack frame. @value{GDBN} has no way of displaying such |
| arguments in stack frames other than the innermost one. Here's what |
| such a backtrace might look like: |
| |
| @smallexample |
| @group |
| #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) |
| at builtin.c:993 |
| #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242 |
| #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08) |
| at macro.c:71 |
| (More stack frames follow...) |
| @end group |
| @end smallexample |
| |
| @noindent |
| The values of arguments that were not saved in their stack frames are |
| shown as @samp{<optimized out>}. |
| |
| If you need to display the values of such optimized-out arguments, |
| either deduce that from other variables whose values depend on the one |
| you are interested in, or recompile without optimizations. |
| |
| @cindex backtrace beyond @code{main} function |
| @cindex program entry point |
| @cindex startup code, and backtrace |
| Most programs have a standard user entry point---a place where system |
| libraries and startup code transition into user code. For C this is |
| @code{main}@footnote{ |
| Note that embedded programs (the so-called ``free-standing'' |
| environment) are not required to have a @code{main} function as the |
| entry point. They could even have multiple entry points.}. |
| When @value{GDBN} finds the entry function in a backtrace |
| it will terminate the backtrace, to avoid tracing into highly |
| system-specific (and generally uninteresting) code. |
| |
| If you need to examine the startup code, or limit the number of levels |
| in a backtrace, you can change this behavior: |
| |
| @table @code |
| @item set backtrace past-main |
| @itemx set backtrace past-main on |
| @kindex set backtrace |
| Backtraces will continue past the user entry point. |
| |
| @item set backtrace past-main off |
| Backtraces will stop when they encounter the user entry point. This is the |
| default. |
| |
| @item show backtrace past-main |
| @kindex show backtrace |
| Display the current user entry point backtrace policy. |
| |
| @item set backtrace past-entry |
| @itemx set backtrace past-entry on |
| Backtraces will continue past the internal entry point of an application. |
| This entry point is encoded by the linker when the application is built, |
| and is likely before the user entry point @code{main} (or equivalent) is called. |
| |
| @item set backtrace past-entry off |
| Backtraces will stop when they encounter the internal entry point of an |
| application. This is the default. |
| |
| @item show backtrace past-entry |
| Display the current internal entry point backtrace policy. |
| |
| @item set backtrace limit @var{n} |
| @itemx set backtrace limit 0 |
| @cindex backtrace limit |
| Limit the backtrace to @var{n} levels. A value of zero means |
| unlimited. |
| |
| @item show backtrace limit |
| Display the current limit on backtrace levels. |
| @end table |
| |
| @node Selection |
| @section Selecting a Frame |
| |
| Most commands for examining the stack and other data in your program work on |
| whichever stack frame is selected at the moment. Here are the commands for |
| selecting a stack frame; all of them finish by printing a brief description |
| of the stack frame just selected. |
| |
| @table @code |
| @kindex frame@r{, selecting} |
| @kindex f @r{(@code{frame})} |
| @item frame @var{n} |
| @itemx f @var{n} |
| Select frame number @var{n}. Recall that frame zero is the innermost |
| (currently executing) frame, frame one is the frame that called the |
| innermost one, and so on. The highest-numbered frame is the one for |
| @code{main}. |
| |
| @item frame @var{addr} |
| @itemx f @var{addr} |
| Select the frame at address @var{addr}. This is useful mainly if the |
| chaining of stack frames has been damaged by a bug, making it |
| impossible for @value{GDBN} to assign numbers properly to all frames. In |
| addition, this can be useful when your program has multiple stacks and |
| switches between them. |
| |
| On the SPARC architecture, @code{frame} needs two addresses to |
| select an arbitrary frame: a frame pointer and a stack pointer. |
| |
| On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack |
| pointer and a program counter. |
| |
| On the 29k architecture, it needs three addresses: a register stack |
| pointer, a program counter, and a memory stack pointer. |
| |
| @kindex up |
| @item up @var{n} |
| Move @var{n} frames up the stack. For positive numbers @var{n}, this |
| advances toward the outermost frame, to higher frame numbers, to frames |
| that have existed longer. @var{n} defaults to one. |
| |
| @kindex down |
| @kindex do @r{(@code{down})} |
| @item down @var{n} |
| Move @var{n} frames down the stack. For positive numbers @var{n}, this |
| advances toward the innermost frame, to lower frame numbers, to frames |
| that were created more recently. @var{n} defaults to one. You may |
| abbreviate @code{down} as @code{do}. |
| @end table |
| |
| All of these commands end by printing two lines of output describing the |
| frame. The first line shows the frame number, the function name, the |
| arguments, and the source file and line number of execution in that |
| frame. The second line shows the text of that source line. |
| |
| @need 1000 |
| For example: |
| |
| @smallexample |
| @group |
| (@value{GDBP}) up |
| #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) |
| at env.c:10 |
| 10 read_input_file (argv[i]); |
| @end group |
| @end smallexample |
| |
| After such a printout, the @code{list} command with no arguments |
| prints ten lines centered on the point of execution in the frame. |
| You can also edit the program at the point of execution with your favorite |
| editing program by typing @code{edit}. |
| @xref{List, ,Printing Source Lines}, |
| for details. |
| |
| @table @code |
| @kindex down-silently |
| @kindex up-silently |
| @item up-silently @var{n} |
| @itemx down-silently @var{n} |
| These two commands are variants of @code{up} and @code{down}, |
| respectively; they differ in that they do their work silently, without |
| causing display of the new frame. They are intended primarily for use |
| in @value{GDBN} command scripts, where the output might be unnecessary and |
| distracting. |
| @end table |
| |
| @node Frame Info |
| @section Information About a Frame |
| |
| There are several other commands to print information about the selected |
| stack frame. |
| |
| @table @code |
| @item frame |
| @itemx f |
| When used without any argument, this command does not change which |
| frame is selected, but prints a brief description of the currently |
| selected stack frame. It can be abbreviated @code{f}. With an |
| argument, this command is used to select a stack frame. |
| @xref{Selection, ,Selecting a Frame}. |
| |
| @kindex info frame |
| @kindex info f @r{(@code{info frame})} |
| @item info frame |
| @itemx info f |
| This command prints a verbose description of the selected stack frame, |
| including: |
| |
| @itemize @bullet |
| @item |
| the address of the frame |
| @item |
| the address of the next frame down (called by this frame) |
| @item |
| the address of the next frame up (caller of this frame) |
| @item |
| the language in which the source code corresponding to this frame is written |
| @item |
| the address of the frame's arguments |
| @item |
| the address of the frame's local variables |
| @item |
| the program counter saved in it (the address of execution in the caller frame) |
| @item |
| which registers were saved in the frame |
| @end itemize |
| |
| @noindent The verbose description is useful when |
| something has gone wrong that has made the stack format fail to fit |
| the usual conventions. |
| |
| @item info frame @var{addr} |
| @itemx info f @var{addr} |
| Print a verbose description of the frame at address @var{addr}, without |
| selecting that frame. The selected frame remains unchanged by this |
| command. This requires the same kind of address (more than one for some |
| architectures) that you specify in the @code{frame} command. |
| @xref{Selection, ,Selecting a Frame}. |
| |
| @kindex info args |
| @item info args |
| Print the arguments of the selected frame, each on a separate line. |
| |
| @item info locals |
| @kindex info locals |
| Print the local variables of the selected frame, each on a separate |
| line. These are all variables (declared either static or automatic) |
| accessible at the point of execution of the selected frame. |
| |
| @end table |
| |
| |
| @node Source |
| @chapter Examining Source Files |
| |
| @value{GDBN} can print parts of your program's source, since the debugging |
| information recorded in the program tells @value{GDBN} what source files were |
| used to build it. When your program stops, @value{GDBN} spontaneously prints |
| the line where it stopped. Likewise, when you select a stack frame |
| (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where |
| execution in that frame has stopped. You can print other portions of |
| source files by explicit command. |
| |
| If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may |
| prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using |
| @value{GDBN} under @sc{gnu} Emacs}. |
| |
| @menu |
| * List:: Printing source lines |
| * Specify Location:: How to specify code locations |
| * Edit:: Editing source files |
| * Search:: Searching source files |
| * Source Path:: Specifying source directories |
| * Machine Code:: Source and machine code |
| @end menu |
| |
| @node List |
| @section Printing Source Lines |
| |
| @kindex list |
| @kindex l @r{(@code{list})} |
| To print lines from a source file, use the @code{list} command |
| (abbreviated @code{l}). By default, ten lines are printed. |
| There are several ways to specify what part of the file you want to |
| print; see @ref{Specify Location}, for the full list. |
| |
| Here are the forms of the @code{list} command most commonly used: |
| |
| @table @code |
| @item list @var{linenum} |
| Print lines centered around line number @var{linenum} in the |
| current source file. |
| |
| @item list @var{function} |
| Print lines centered around the beginning of function |
| @var{function}. |
| |
| @item list |
| Print more lines. If the last lines printed were printed with a |
| @code{list} command, this prints lines following the last lines |
| printed; however, if the last line printed was a solitary line printed |
| as part of displaying a stack frame (@pxref{Stack, ,Examining the |
| Stack}), this prints lines centered around that line. |
| |
| @item list - |
| Print lines just before the lines last printed. |
| @end table |
| |
| @cindex @code{list}, how many lines to display |
| By default, @value{GDBN} prints ten source lines with any of these forms of |
| the @code{list} command. You can change this using @code{set listsize}: |
| |
| @table @code |
| @kindex set listsize |
| @item set listsize @var{count} |
| Make the @code{list} command display @var{count} source lines (unless |
| the @code{list} argument explicitly specifies some other number). |
| |
| @kindex show listsize |
| @item show listsize |
| Display the number of lines that @code{list} prints. |
| @end table |
| |
| Repeating a @code{list} command with @key{RET} discards the argument, |
| so it is equivalent to typing just @code{list}. This is more useful |
| than listing the same lines again. An exception is made for an |
| argument of @samp{-}; that argument is preserved in repetition so that |
| each repetition moves up in the source file. |
| |
| In general, the @code{list} command expects you to supply zero, one or two |
| @dfn{linespecs}. Linespecs specify source lines; there are several ways |
| of writing them (@pxref{Specify Location}), but the effect is always |
| to specify some source line. |
| |
| Here is a complete description of the possible arguments for @code{list}: |
| |
| @table @code |
| @item list @var{linespec} |
| Print lines centered around the line specified by @var{linespec}. |
| |
| @item list @var{first},@var{last} |
| Print lines from @var{first} to @var{last}. Both arguments are |
| linespecs. When a @code{list} command has two linespecs, and the |
| source file of the second linespec is omitted, this refers to |
| the same source file as the first linespec. |
| |
| @item list ,@var{last} |
| Print lines ending with @var{last}. |
| |
| @item list @var{first}, |
| Print lines starting with @var{first}. |
| |
| @item list + |
| Print lines just after the lines last printed. |
| |
| @item list - |
| Print lines just before the lines last printed. |
| |
| @item list |
| As described in the preceding table. |
| @end table |
| |
| @node Specify Location |
| @section Specifying a Location |
| @cindex specifying location |
| @cindex linespec |
| |
| Several @value{GDBN} commands accept arguments that specify a location |
| of your program's code. Since @value{GDBN} is a source-level |
| debugger, a location usually specifies some line in the source code; |
| for that reason, locations are also known as @dfn{linespecs}. |
| |
| Here are all the different ways of specifying a code location that |
| @value{GDBN} understands: |
| |
| @table @code |
| @item @var{linenum} |
| Specifies the line number @var{linenum} of the current source file. |
| |
| @item -@var{offset} |
| @itemx +@var{offset} |
| Specifies the line @var{offset} lines before or after the @dfn{current |
| line}. For the @code{list} command, the current line is the last one |
| printed; for the breakpoint commands, this is the line at which |
| execution stopped in the currently selected @dfn{stack frame} |
| (@pxref{Frames, ,Frames}, for a description of stack frames.) When |
| used as the second of the two linespecs in a @code{list} command, |
| this specifies the line @var{offset} lines up or down from the first |
| linespec. |
| |
| @item @var{filename}:@var{linenum} |
| Specifies the line @var{linenum} in the source file @var{filename}. |
| If @var{filename} is a relative file name, then it will match any |
| source file name with the same trailing components. For example, if |
| @var{filename} is @samp{gcc/expr.c}, then it will match source file |
| name of @file{/build/trunk/gcc/expr.c}, but not |
| @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}. |
| |
| @item @var{function} |
| Specifies the line that begins the body of the function @var{function}. |
| For example, in C, this is the line with the open brace. |
| |
| @item @var{function}:@var{label} |
| Specifies the line where @var{label} appears in @var{function}. |
| |
| @item @var{filename}:@var{function} |
| Specifies the line that begins the body of the function @var{function} |
| in the file @var{filename}. You only need the file name with a |
| function name to avoid ambiguity when there are identically named |
| functions in different source files. |
| |
| @item @var{label} |
| Specifies the line at which the label named @var{label} appears. |
| @value{GDBN} searches for the label in the function corresponding to |
| the currently selected stack frame. If there is no current selected |
| stack frame (for instance, if the inferior is not running), then |
| @value{GDBN} will not search for a label. |
| |
| @item *@var{address} |
| Specifies the program address @var{address}. For line-oriented |
| commands, such as @code{list} and @code{edit}, this specifies a source |
| line that contains @var{address}. For @code{break} and other |
| breakpoint oriented commands, this can be used to set breakpoints in |
| parts of your program which do not have debugging information or |
| source files. |
| |
| Here @var{address} may be any expression valid in the current working |
| language (@pxref{Languages, working language}) that specifies a code |
| address. In addition, as a convenience, @value{GDBN} extends the |
| semantics of expressions used in locations to cover the situations |
| that frequently happen during debugging. Here are the various forms |
| of @var{address}: |
| |
| @table @code |
| @item @var{expression} |
| Any expression valid in the current working language. |
| |
| @item @var{funcaddr} |
| An address of a function or procedure derived from its name. In C, |
| C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is |
| simply the function's name @var{function} (and actually a special case |
| of a valid expression). In Pascal and Modula-2, this is |
| @code{&@var{function}}. In Ada, this is @code{@var{function}'Address} |
| (although the Pascal form also works). |
| |
| This form specifies the address of the function's first instruction, |
| before the stack frame and arguments have been set up. |
| |
| @item '@var{filename}'::@var{funcaddr} |
| Like @var{funcaddr} above, but also specifies the name of the source |
| file explicitly. This is useful if the name of the function does not |
| specify the function unambiguously, e.g., if there are several |
| functions with identical names in different source files. |
| @end table |
| |
| @cindex breakpoint at static probe point |
| @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name} |
| The @sc{gnu}/Linux tool @code{SystemTap} provides a way for |
| applications to embed static probes. @xref{Static Probe Points}, for more |
| information on finding and using static probes. This form of linespec |
| specifies the location of such a static probe. |
| |
| If @var{objfile} is given, only probes coming from that shared library |
| or executable matching @var{objfile} as a regular expression are considered. |
| If @var{provider} is given, then only probes from that provider are considered. |
| If several probes match the spec, @value{GDBN} will insert a breakpoint at |
| each one of those probes. |
| |
| @end table |
| |
| |
| @node Edit |
| @section Editing Source Files |
| @cindex editing source files |
| |
| @kindex edit |
| @kindex e @r{(@code{edit})} |
| To edit the lines in a source file, use the @code{edit} command. |
| The editing program of your choice |
| is invoked with the current line set to |
| the active line in the program. |
| Alternatively, there are several ways to specify what part of the file you |
| want to print if you want to see other parts of the program: |
| |
| @table @code |
| @item edit @var{location} |
| Edit the source file specified by @code{location}. Editing starts at |
| that @var{location}, e.g., at the specified source line of the |
| specified file. @xref{Specify Location}, for all the possible forms |
| of the @var{location} argument; here are the forms of the @code{edit} |
| command most commonly used: |
| |
| @table @code |
| @item edit @var{number} |
| Edit the current source file with @var{number} as the active line number. |
| |
| @item edit @var{function} |
| Edit the file containing @var{function} at the beginning of its definition. |
| @end table |
| |
| @end table |
| |
| @subsection Choosing your Editor |
| You can customize @value{GDBN} to use any editor you want |
| @footnote{ |
| The only restriction is that your editor (say @code{ex}), recognizes the |
| following command-line syntax: |
| @smallexample |
| ex +@var{number} file |
| @end smallexample |
| The optional numeric value +@var{number} specifies the number of the line in |
| the file where to start editing.}. |
| By default, it is @file{@value{EDITOR}}, but you can change this |
| by setting the environment variable @code{EDITOR} before using |
| @value{GDBN}. For example, to configure @value{GDBN} to use the |
| @code{vi} editor, you could use these commands with the @code{sh} shell: |
| @smallexample |
| EDITOR=/usr/bin/vi |
| export EDITOR |
| gdb @dots{} |
| @end smallexample |
| or in the @code{csh} shell, |
| @smallexample |
| setenv EDITOR /usr/bin/vi |
| gdb @dots{} |
| @end smallexample |
| |
| @node Search |
| @section Searching Source Files |
| @cindex searching source files |
| |
| There are two commands for searching through the current source file for a |
| regular expression. |
| |
| @table @code |
| @kindex search |
| @kindex forward-search |
| @item forward-search @var{regexp} |
| @itemx search @var{regexp} |
| The command @samp{forward-search @var{regexp}} checks each line, |
| starting with the one following the last line listed, for a match for |
| @var{regexp}. It lists the line that is found. You can use the |
| synonym @samp{search @var{regexp}} or abbreviate the command name as |
| @code{fo}. |
| |
| @kindex reverse-search |
| @item reverse-search @var{regexp} |
| The command @samp{reverse-search @var{regexp}} checks each line, starting |
| with the one before the last line listed and going backward, for a match |
| for @var{regexp}. It lists the line that is found. You can abbreviate |
| this command as @code{rev}. |
| @end table |
| |
| @node Source Path |
| @section Specifying Source Directories |
| |
| @cindex source path |
| @cindex directories for source files |
| Executable programs sometimes do not record the directories of the source |
| files from which they were compiled, just the names. Even when they do, |
| the directories could be moved between the compilation and your debugging |
| session. @value{GDBN} has a list of directories to search for source files; |
| this is called the @dfn{source path}. Each time @value{GDBN} wants a source file, |
| it tries all the directories in the list, in the order they are present |
| in the list, until it finds a file with the desired name. |
| |
| For example, suppose an executable references the file |
| @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is |
| @file{/mnt/cross}. The file is first looked up literally; if this |
| fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this |
| fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error |
| message is printed. @value{GDBN} does not look up the parts of the |
| source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}. |
| Likewise, the subdirectories of the source path are not searched: if |
| the source path is @file{/mnt/cross}, and the binary refers to |
| @file{foo.c}, @value{GDBN} would not find it under |
| @file{/mnt/cross/usr/src/foo-1.0/lib}. |
| |
| Plain file names, relative file names with leading directories, file |
| names containing dots, etc.@: are all treated as described above; for |
| instance, if the source path is @file{/mnt/cross}, and the source file |
| is recorded as @file{../lib/foo.c}, @value{GDBN} would first try |
| @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after |
| that---@file{/mnt/cross/foo.c}. |
| |
| Note that the executable search path is @emph{not} used to locate the |
| source files. |
| |
| Whenever you reset or rearrange the source path, @value{GDBN} clears out |
| any information it has cached about where source files are found and where |
| each line is in the file. |
| |
| @kindex directory |
| @kindex dir |
| When you start @value{GDBN}, its source path includes only @samp{cdir} |
| and @samp{cwd}, in that order. |
| To add other directories, use the @code{directory} command. |
| |
| The search path is used to find both program source files and @value{GDBN} |
| script files (read using the @samp{-command} option and @samp{source} command). |
| |
| In addition to the source path, @value{GDBN} provides a set of commands |
| that manage a list of source path substitution rules. A @dfn{substitution |
| rule} specifies how to rewrite source directories stored in the program's |
| debug information in case the sources were moved to a different |
| directory between compilation and debugging. A rule is made of |
| two strings, the first specifying what needs to be rewritten in |
| the path, and the second specifying how it should be rewritten. |
| In @ref{set substitute-path}, we name these two parts @var{from} and |
| @var{to} respectively. @value{GDBN} does a simple string replacement |
| of @var{from} with @var{to} at the start of the directory part of the |
| source file name, and uses that result instead of the original file |
| name to look up the sources. |
| |
| Using the previous example, suppose the @file{foo-1.0} tree has been |
| moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell |
| @value{GDBN} to replace @file{/usr/src} in all source path names with |
| @file{/mnt/cross}. The first lookup will then be |
| @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location |
| of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path |
| substitution rule, use the @code{set substitute-path} command |
| (@pxref{set substitute-path}). |
| |
| To avoid unexpected substitution results, a rule is applied only if the |
| @var{from} part of the directory name ends at a directory separator. |
| For instance, a rule substituting @file{/usr/source} into |
| @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but |
| not to @file{/usr/sourceware/foo-2.0}. And because the substitution |
| is applied only at the beginning of the directory name, this rule will |
| not be applied to @file{/root/usr/source/baz.c} either. |
| |
| In many cases, you can achieve the same result using the @code{directory} |
| command. However, @code{set substitute-path} can be more efficient in |
| the case where the sources are organized in a complex tree with multiple |
| subdirectories. With the @code{directory} command, you need to add each |
| subdirectory of your project. If you moved the entire tree while |
| preserving its internal organization, then @code{set substitute-path} |
| allows you to direct the debugger to all the sources with one single |
| command. |
| |
| @code{set substitute-path} is also more than just a shortcut command. |
| The source path is only used if the file at the original location no |
| longer exists. On the other hand, @code{set substitute-path} modifies |
| the debugger behavior to look at the rewritten location instead. So, if |
| for any reason a source file that is not relevant to your executable is |
| located at the original location, a substitution rule is the only |
| method available to point @value{GDBN} at the new location. |
| |
| @cindex @samp{--with-relocated-sources} |
| @cindex default source path substitution |
| You can configure a default source path substitution rule by |
| configuring @value{GDBN} with the |
| @samp{--with-relocated-sources=@var{dir}} option. The @var{dir} |
| should be the name of a directory under @value{GDBN}'s configured |
| prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and |
| directory names in debug information under @var{dir} will be adjusted |
| automatically if the installed @value{GDBN} is moved to a new |
| location. This is useful if @value{GDBN}, libraries or executables |
| with debug information and corresponding source code are being moved |
| together. |
| |
| @table @code |
| @item directory @var{dirname} @dots{} |
| @item dir @var{dirname} @dots{} |
| Add directory @var{dirname} to the front of the source path. Several |
| directory names may be given to this command, separated by @samp{:} |
| (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as |
| part of absolute file names) or |
| whitespace. You may specify a directory that is already in the source |
| path; this moves it forward, so @value{GDBN} searches it sooner. |
| |
| @kindex cdir |
| @kindex cwd |
| @vindex $cdir@r{, convenience variable} |
| @vindex $cwd@r{, convenience variable} |
| @cindex compilation directory |
| @cindex current directory |
| @cindex working directory |
| @cindex directory, current |
| @cindex directory, compilation |
| You can use the string @samp{$cdir} to refer to the compilation |
| directory (if one is recorded), and @samp{$cwd} to refer to the current |
| working directory. @samp{$cwd} is not the same as @samp{.}---the former |
| tracks the current working directory as it changes during your @value{GDBN} |
| session, while the latter is immediately expanded to the current |
| directory at the time you add an entry to the source path. |
| |
| @item directory |
| Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation. |
| |
| @c RET-repeat for @code{directory} is explicitly disabled, but since |
| @c repeating it would be a no-op we do not say that. (thanks to RMS) |
| |
| @item set directories @var{path-list} |
| @kindex set directories |
| Set the source path to @var{path-list}. |
| @samp{$cdir:$cwd} are added if missing. |
| |
| @item show directories |
| @kindex show directories |
| Print the source path: show which directories it contains. |
| |
| @anchor{set substitute-path} |
| @item set substitute-path @var{from} @var{to} |
| @kindex set substitute-path |
| Define a source path substitution rule, and add it at the end of the |
| current list of existing substitution rules. If a rule with the same |
| @var{from} was already defined, then the old rule is also deleted. |
| |
| For example, if the file @file{/foo/bar/baz.c} was moved to |
| @file{/mnt/cross/baz.c}, then the command |
| |
| @smallexample |
| (@value{GDBP}) set substitute-path /usr/src /mnt/cross |
| @end smallexample |
| |
| @noindent |
| will tell @value{GDBN} to replace @samp{/usr/src} with |
| @samp{/mnt/cross}, which will allow @value{GDBN} to find the file |
| @file{baz.c} even though it was moved. |
| |
| In the case when more than one substitution rule have been defined, |
| the rules are evaluated one by one in the order where they have been |
| defined. The first one matching, if any, is selected to perform |
| the substitution. |
| |
| For instance, if we had entered the following commands: |
| |
| @smallexample |
| (@value{GDBP}) set substitute-path /usr/src/include /mnt/include |
| (@value{GDBP}) set substitute-path /usr/src /mnt/src |
| @end smallexample |
| |
| @noindent |
| @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into |
| @file{/mnt/include/defs.h} by using the first rule. However, it would |
| use the second rule to rewrite @file{/usr/src/lib/foo.c} into |
| @file{/mnt/src/lib/foo.c}. |
| |
| |
| @item unset substitute-path [path] |
| @kindex unset substitute-path |
| If a path is specified, search the current list of substitution rules |
| for a rule that would rewrite that path. Delete that rule if found. |
| A warning is emitted by the debugger if no rule could be found. |
| |
| If no path is specified, then all substitution rules are deleted. |
| |
| @item show substitute-path [path] |
| @kindex show substitute-path |
| If a path is specified, then print the source path substitution rule |
| which would rewrite that path, if any. |
| |
| If no path is specified, then print all existing source path substitution |
| rules. |
| |
| @end table |
| |
| If your source path is cluttered with directories that are no longer of |
| interest, @value{GDBN} may sometimes cause confusion by finding the wrong |
| versions of source. You can correct the situation as follows: |
| |
| @enumerate |
| @item |
| Use @code{directory} with no argument to reset the source path to its default value. |
| |
| @item |
| Use @code{directory} with suitable arguments to reinstall the |
| directories you want in the source path. You can add all the |
| directories in one command. |
| @end enumerate |
| |
| @node Machine Code |
| @section Source and Machine Code |
| @cindex source line and its code address |
| |
| You can use the command @code{info line} to map source lines to program |
| addresses (and vice versa), and the command @code{disassemble} to display |
| a range of addresses as machine instructions. You can use the command |
| @code{set disassemble-next-line} to set whether to disassemble next |
| source line when execution stops. When run under @sc{gnu} Emacs |
| mode, the @code{info line} command causes the arrow to point to the |
| line specified. Also, @code{info line} prints addresses in symbolic form as |
| well as hex. |
| |
| @table @code |
| @kindex info line |
| @item info line @var{linespec} |
| Print the starting and ending addresses of the compiled code for |
| source line @var{linespec}. You can specify source lines in any of |
| the ways documented in @ref{Specify Location}. |
| @end table |
| |
| For example, we can use @code{info line} to discover the location of |
| the object code for the first line of function |
| @code{m4_changequote}: |
| |
| @c FIXME: I think this example should also show the addresses in |
| @c symbolic form, as they usually would be displayed. |
| @smallexample |
| (@value{GDBP}) info line m4_changequote |
| Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350. |
| @end smallexample |
| |
| @noindent |
| @cindex code address and its source line |
| We can also inquire (using @code{*@var{addr}} as the form for |
| @var{linespec}) what source line covers a particular address: |
| @smallexample |
| (@value{GDBP}) info line *0x63ff |
| Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. |
| @end smallexample |
| |
| @cindex @code{$_} and @code{info line} |
| @cindex @code{x} command, default address |
| @kindex x@r{(examine), and} info line |
| After @code{info line}, the default address for the @code{x} command |
| is changed to the starting address of the line, so that @samp{x/i} is |
| sufficient to begin examining the machine code (@pxref{Memory, |
| ,Examining Memory}). Also, this address is saved as the value of the |
| convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience |
| Variables}). |
| |
| @table @code |
| @kindex disassemble |
| @cindex assembly instructions |
| @cindex instructions, assembly |
| @cindex machine instructions |
| @cindex listing machine instructions |
| @item disassemble |
| @itemx disassemble /m |
| @itemx disassemble /r |
| This specialized command dumps a range of memory as machine |
| instructions. It can also print mixed source+disassembly by specifying |
| the @code{/m} modifier and print the raw instructions in hex as well as |
| in symbolic form by specifying the @code{/r}. |
| The default memory range is the function surrounding the |
| program counter of the selected frame. A single argument to this |
| command is a program counter value; @value{GDBN} dumps the function |
| surrounding this value. When two arguments are given, they should |
| be separated by a comma, possibly surrounded by whitespace. The |
| arguments specify a range of addresses to dump, in one of two forms: |
| |
| @table @code |
| @item @var{start},@var{end} |
| the addresses from @var{start} (inclusive) to @var{end} (exclusive) |
| @item @var{start},+@var{length} |
| the addresses from @var{start} (inclusive) to |
| @code{@var{start}+@var{length}} (exclusive). |
| @end table |
| |
| @noindent |
| When 2 arguments are specified, the name of the function is also |
| printed (since there could be several functions in the given range). |
| |
| The argument(s) can be any expression yielding a numeric value, such as |
| @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}. |
| |
| If the range of memory being disassembled contains current program counter, |
| the instruction at that location is shown with a @code{=>} marker. |
| @end table |
| |
| The following example shows the disassembly of a range of addresses of |
| HP PA-RISC 2.0 code: |
| |
| @smallexample |
| (@value{GDBP}) disas 0x32c4, 0x32e4 |
| Dump of assembler code from 0x32c4 to 0x32e4: |
| 0x32c4 <main+204>: addil 0,dp |
| 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26 |
| 0x32cc <main+212>: ldil 0x3000,r31 |
| 0x32d0 <main+216>: ble 0x3f8(sr4,r31) |
| 0x32d4 <main+220>: ldo 0(r31),rp |
| 0x32d8 <main+224>: addil -0x800,dp |
| 0x32dc <main+228>: ldo 0x588(r1),r26 |
| 0x32e0 <main+232>: ldil 0x3000,r31 |
| End of assembler dump. |
| @end smallexample |
| |
| Here is an example showing mixed source+assembly for Intel x86, when the |
| program is stopped just after function prologue: |
| |
| @smallexample |
| (@value{GDBP}) disas /m main |
| Dump of assembler code for function main: |
| 5 @{ |
| 0x08048330 <+0>: push %ebp |
| 0x08048331 <+1>: mov %esp,%ebp |
| 0x08048333 <+3>: sub $0x8,%esp |
| 0x08048336 <+6>: and $0xfffffff0,%esp |
| 0x08048339 <+9>: sub $0x10,%esp |
| |
| 6 printf ("Hello.\n"); |
| => 0x0804833c <+12>: movl $0x8048440,(%esp) |
| 0x08048343 <+19>: call 0x8048284 <puts@@plt> |
| |
| 7 return 0; |
| 8 @} |
| 0x08048348 <+24>: mov $0x0,%eax |
| 0x0804834d <+29>: leave |
| 0x0804834e <+30>: ret |
| |
| End of assembler dump. |
| @end smallexample |
| |
| Here is another example showing raw instructions in hex for AMD x86-64, |
| |
| @smallexample |
| (gdb) disas /r 0x400281,+10 |
| Dump of assembler code from 0x400281 to 0x40028b: |
| 0x0000000000400281: 38 36 cmp %dh,(%rsi) |
| 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax |
| 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx) |
| 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al |
| End of assembler dump. |
| @end smallexample |
| |
| Some architectures have more than one commonly-used set of instruction |
| mnemonics or other syntax. |
| |
| For programs that were dynamically linked and use shared libraries, |
| instructions that call functions or branch to locations in the shared |
| libraries might show a seemingly bogus location---it's actually a |
| location of the relocation table. On some architectures, @value{GDBN} |
| might be able to resolve these to actual function names. |
| |
| @table @code |
| @kindex set disassembly-flavor |
| @cindex Intel disassembly flavor |
| @cindex AT&T disassembly flavor |
| @item set disassembly-flavor @var{instruction-set} |
| Select the instruction set to use when disassembling the |
| program via the @code{disassemble} or @code{x/i} commands. |
| |
| Currently this command is only defined for the Intel x86 family. You |
| can set @var{instruction-set} to either @code{intel} or @code{att}. |
| The default is @code{att}, the AT&T flavor used by default by Unix |
| assemblers for x86-based targets. |
| |
| @kindex show disassembly-flavor |
| @item show disassembly-flavor |
| Show the current setting of the disassembly flavor. |
| @end table |
| |
| @table @code |
| @kindex set disassemble-next-line |
| @kindex show disassemble-next-line |
| @item set disassemble-next-line |
| @itemx show disassemble-next-line |
| Control whether or not @value{GDBN} will disassemble the next source |
| line or instruction when execution stops. If ON, @value{GDBN} will |
| display disassembly of the next source line when execution of the |
| program being debugged stops. This is @emph{in addition} to |
| displaying the source line itself, which @value{GDBN} always does if |
| possible. If the next source line cannot be displayed for some reason |
| (e.g., if @value{GDBN} cannot find the source file, or there's no line |
| info in the debug info), @value{GDBN} will display disassembly of the |
| next @emph{instruction} instead of showing the next source line. If |
| AUTO, @value{GDBN} will display disassembly of next instruction only |
| if the source line cannot be displayed. This setting causes |
| @value{GDBN} to display some feedback when you step through a function |
| with no line info or whose source file is unavailable. The default is |
| OFF, which means never display the disassembly of the next line or |
| instruction. |
| @end table |
| |
| |
| @node Data |
| @chapter Examining Data |
| |
| @cindex printing data |
| @cindex examining data |
| @kindex print |
| @kindex inspect |
| @c "inspect" is not quite a synonym if you are using Epoch, which we do not |
| @c document because it is nonstandard... Under Epoch it displays in a |
| @c different window or something like that. |
| The usual way to examine data in your program is with the @code{print} |
| command (abbreviated @code{p}), or its synonym @code{inspect}. It |
| evaluates and prints the value of an expression of the language your |
| program is written in (@pxref{Languages, ,Using @value{GDBN} with |
| Different Languages}). It may also print the expression using a |
| Python-based pretty-printer (@pxref{Pretty Printing}). |
| |
| @table @code |
| @item print @var{expr} |
| @itemx print /@var{f} @var{expr} |
| @var{expr} is an expression (in the source language). By default the |
| value of @var{expr} is printed in a format appropriate to its data type; |
| you can choose a different format by specifying @samp{/@var{f}}, where |
| @var{f} is a letter specifying the format; see @ref{Output Formats,,Output |
| Formats}. |
| |
| @item print |
| @itemx print /@var{f} |
| @cindex reprint the last value |
| If you omit @var{expr}, @value{GDBN} displays the last value again (from the |
| @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to |
| conveniently inspect the same value in an alternative format. |
| @end table |
| |
| A more low-level way of examining data is with the @code{x} command. |
| It examines data in memory at a specified address and prints it in a |
| specified format. @xref{Memory, ,Examining Memory}. |
| |
| If you are interested in information about types, or about how the |
| fields of a struct or a class are declared, use the @code{ptype @var{exp}} |
| command rather than @code{print}. @xref{Symbols, ,Examining the Symbol |
| Table}. |
| |
| @cindex exploring hierarchical data structures |
| @kindex explore |
| Another way of examining values of expressions and type information is |
| through the Python extension command @code{explore} (available only if |
| the @value{GDBN} build is configured with @code{--with-python}). It |
| offers an interactive way to start at the highest level (or, the most |
| abstract level) of the data type of an expression (or, the data type |
| itself) and explore all the way down to leaf scalar values/fields |
| embedded in the higher level data types. |
| |
| @table @code |
| @item explore @var{arg} |
| @var{arg} is either an expression (in the source language), or a type |
| visible in the current context of the program being debugged. |
| @end table |
| |
| The working of the @code{explore} command can be illustrated with an |
| example. If a data type @code{struct ComplexStruct} is defined in your |
| C program as |
| |
| @smallexample |
| struct SimpleStruct |
| @{ |
| int i; |
| double d; |
| @}; |
| |
| struct ComplexStruct |
| @{ |
| struct SimpleStruct *ss_p; |
| int arr[10]; |
| @}; |
| @end smallexample |
| |
| @noindent |
| followed by variable declarations as |
| |
| @smallexample |
| struct SimpleStruct ss = @{ 10, 1.11 @}; |
| struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @}; |
| @end smallexample |
| |
| @noindent |
| then, the value of the variable @code{cs} can be explored using the |
| @code{explore} command as follows. |
| |
| @smallexample |
| (gdb) explore cs |
| The value of `cs' is a struct/class of type `struct ComplexStruct' with |
| the following fields: |
| |
| ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'> |
| arr = <Enter 1 to explore this field of type `int [10]'> |
| |
| Enter the field number of choice: |
| @end smallexample |
| |
| @noindent |
| Since the fields of @code{cs} are not scalar values, you are being |
| prompted to chose the field you want to explore. Let's say you choose |
| the field @code{ss_p} by entering @code{0}. Then, since this field is a |
| pointer, you will be asked if it is pointing to a single value. From |
| the declaration of @code{cs} above, it is indeed pointing to a single |
| value, hence you enter @code{y}. If you enter @code{n}, then you will |
| be asked if it were pointing to an array of values, in which case this |
| field will be explored as if it were an array. |
| |
| @smallexample |
| `cs.ss_p' is a pointer to a value of type `struct SimpleStruct' |
| Continue exploring it as a pointer to a single value [y/n]: y |
| The value of `*(cs.ss_p)' is a struct/class of type `struct |
| SimpleStruct' with the following fields: |
| |
| i = 10 .. (Value of type `int') |
| d = 1.1100000000000001 .. (Value of type `double') |
| |
| Press enter to return to parent value: |
| @end smallexample |
| |
| @noindent |
| If the field @code{arr} of @code{cs} was chosen for exploration by |
| entering @code{1} earlier, then since it is as array, you will be |
| prompted to enter the index of the element in the array that you want |
| to explore. |
| |
| @smallexample |
| `cs.arr' is an array of `int'. |
| Enter the index of the element you want to explore in `cs.arr': 5 |
| |
| `(cs.arr)[5]' is a scalar value of type `int'. |
| |
| (cs.arr)[5] = 4 |
| |
| Press enter to return to parent value: |
| @end smallexample |
| |
| In general, at any stage of exploration, you can go deeper towards the |
| leaf values by responding to the prompts appropriately, or hit the |
| return key to return to the enclosing data structure (the @i{higher} |
| level data structure). |
| |
| Similar to exploring values, you can use the @code{explore} command to |
| explore types. Instead of specifying a value (which is typically a |
| variable name or an expression valid in the current context of the |
| program being debugged), you specify a type name. If you consider the |
| same example as above, your can explore the type |
| @code{struct ComplexStruct} by passing the argument |
| @code{struct ComplexStruct} to the @code{explore} command. |
| |
| @smallexample |
| (gdb) explore struct ComplexStruct |
| @end smallexample |
| |
| @noindent |
| By responding to the prompts appropriately in the subsequent interactive |
| session, you can explore the type @code{struct ComplexStruct} in a |
| manner similar to how the value @code{cs} was explored in the above |
| example. |
| |
| The @code{explore} command also has two sub-commands, |
| @code{explore value} and @code{explore type}. The former sub-command is |
| a way to explicitly specify that value exploration of the argument is |
| being invoked, while the latter is a way to explicitly specify that type |
| exploration of the argument is being invoked. |
| |
| @table @code |
| @item explore value @var{expr} |
| @cindex explore value |
| This sub-command of @code{explore} explores the value of the |
| expression @var{expr} (if @var{expr} is an expression valid in the |
| current context of the program being debugged). The behavior of this |
| command is identical to that of the behavior of the @code{explore} |
| command being passed the argument @var{expr}. |
| |
| @item explore type @var{arg} |
| @cindex explore type |
| This sub-command of @code{explore} explores the type of @var{arg} (if |
| @var{arg} is a type visible in the current context of program being |
| debugged), or the type of the value/expression @var{arg} (if @var{arg} |
| is an expression valid in the current context of the program being |
| debugged). If @var{arg} is a type, then the behavior of this command is |
| identical to that of the @code{explore} command being passed the |
| argument @var{arg}. If @var{arg} is an expression, then the behavior of |
| this command will be identical to that of the @code{explore} command |
| being passed the type of @var{arg} as the argument. |
| @end table |
| |
| @menu |
| * Expressions:: Expressions |
| * Ambiguous Expressions:: Ambiguous Expressions |
| * Variables:: Program variables |
| * Arrays:: Artificial arrays |
| * Output Formats:: Output formats |
| * Memory:: Examining memory |
| * Auto Display:: Automatic display |
| * Print Settings:: Print settings |
| * Pretty Printing:: Python pretty printing |
| * Value History:: Value history |
| * Convenience Vars:: Convenience variables |
| * Registers:: Registers |
| * Floating Point Hardware:: Floating point hardware |
| * Vector Unit:: Vector Unit |
| * OS Information:: Auxiliary data provided by operating system |
| * Memory Region Attributes:: Memory region attributes |
| * Dump/Restore Files:: Copy between memory and a file |
| * Core File Generation:: Cause a program dump its core |
| * Character Sets:: Debugging programs that use a different |
| character set than GDB does |
| * Caching Remote Data:: Data caching for remote targets |
| * Searching Memory:: Searching memory for a sequence of bytes |
| @end menu |
| |
| @node Expressions |
| @section Expressions |
| |
| @cindex expressions |
| @code{print} and many other @value{GDBN} commands accept an expression and |
| compute its value. Any kind of constant, variable or operator defined |
| by the programming language you are using is valid in an expression in |
| @value{GDBN}. This includes conditional expressions, function calls, |
| casts, and string constants. It also includes preprocessor macros, if |
| you compiled your program to include this information; see |
| @ref{Compilation}. |
| |
| @cindex arrays in expressions |
| @value{GDBN} supports array constants in expressions input by |
| the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example, |
| you can use the command @code{print @{1, 2, 3@}} to create an array |
| of three integers. If you pass an array to a function or assign it |
| to a program variable, @value{GDBN} copies the array to memory that |
| is @code{malloc}ed in the target program. |
| |
| Because C is so widespread, most of the expressions shown in examples in |
| this manual are in C. @xref{Languages, , Using @value{GDBN} with Different |
| Languages}, for information on how to use expressions in other |
| languages. |
| |
| In this section, we discuss operators that you can use in @value{GDBN} |
| expressions regardless of your programming language. |
| |
| @cindex casts, in expressions |
| Casts are supported in all languages, not just in C, because it is so |
| useful to cast a number into a pointer in order to examine a structure |
| at that address in memory. |
| @c FIXME: casts supported---Mod2 true? |
| |
| @value{GDBN} supports these operators, in addition to those common |
| to programming languages: |
| |
| @table @code |
| @item @@ |
| @samp{@@} is a binary operator for treating parts of memory as arrays. |
| @xref{Arrays, ,Artificial Arrays}, for more information. |
| |
| @item :: |
| @samp{::} allows you to specify a variable in terms of the file or |
| function where it is defined. @xref{Variables, ,Program Variables}. |
| |
| @cindex @{@var{type}@} |
| @cindex type casting memory |
| @cindex memory, viewing as typed object |
| @cindex casts, to view memory |
| @item @{@var{type}@} @var{addr} |
| Refers to an object of type @var{type} stored at address @var{addr} in |
| memory. @var{addr} may be any expression whose value is an integer or |
| pointer (but parentheses are required around binary operators, just as in |
| a cast). This construct is allowed regardless of what kind of data is |
| normally supposed to reside at @var{addr}. |
| @end table |
| |
| @node Ambiguous Expressions |
| @section Ambiguous Expressions |
| @cindex ambiguous expressions |
| |
| Expressions can sometimes contain some ambiguous elements. For instance, |
| some programming languages (notably Ada, C@t{++} and Objective-C) permit |
| a single function name to be defined several times, for application in |
| different contexts. This is called @dfn{overloading}. Another example |
| involving Ada is generics. A @dfn{generic package} is similar to C@t{++} |
| templates and is typically instantiated several times, resulting in |
| the same function name being defined in different contexts. |
| |
| In some cases and depending on the language, it is possible to adjust |
| the expression to remove the ambiguity. For instance in C@t{++}, you |
| can specify the signature of the function you want to break on, as in |
| @kbd{break @var{function}(@var{types})}. In Ada, using the fully |
| qualified name of your function often makes the expression unambiguous |
| as well. |
| |
| When an ambiguity that needs to be resolved is detected, the debugger |
| has the capability to display a menu of numbered choices for each |
| possibility, and then waits for the selection with the prompt @samp{>}. |
| The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}} |
| aborts the current command. If the command in which the expression was |
| used allows more than one choice to be selected, the next option in the |
| menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible |
| choices. |
| |
| For example, the following session excerpt shows an attempt to set a |
| breakpoint at the overloaded symbol @code{String::after}. |
| We choose three particular definitions of that function name: |
| |
| @c FIXME! This is likely to change to show arg type lists, at least |
| @smallexample |
| @group |
| (@value{GDBP}) b String::after |
| [0] cancel |
| [1] all |
| [2] file:String.cc; line number:867 |
| [3] file:String.cc; line number:860 |
| [4] file:String.cc; line number:875 |
| [5] file:String.cc; line number:853 |
| [6] file:String.cc; line number:846 |
| [7] file:String.cc; line number:735 |
| > 2 4 6 |
| Breakpoint 1 at 0xb26c: file String.cc, line 867. |
| Breakpoint 2 at 0xb344: file String.cc, line 875. |
| Breakpoint 3 at 0xafcc: file String.cc, line 846. |
| Multiple breakpoints were set. |
| Use the "delete" command to delete unwanted |
| breakpoints. |
| (@value{GDBP}) |
| @end group |
| @end smallexample |
| |
| @table @code |
| @kindex set multiple-symbols |
| @item set multiple-symbols @var{mode} |
| @cindex multiple-symbols menu |
| |
| This option allows you to adjust the debugger behavior when an expression |
| is ambiguous. |
| |
| By default, @var{mode} is set to @code{all}. If the command with which |
| the expression is used allows more than one choice, then @value{GDBN} |
| automatically selects all possible choices. For instance, inserting |
| a breakpoint on a function using an ambiguous name results in a breakpoint |
| inserted on each possible match. However, if a unique choice must be made, |
| then @value{GDBN} uses the menu to help you disambiguate the expression. |
| For instance, printing the address of an overloaded function will result |
| in the use of the menu. |
| |
| When @var{mode} is set to @code{ask}, the debugger always uses the menu |
| when an ambiguity is detected. |
| |
| Finally, when @var{mode} is set to @code{cancel}, the debugger reports |
| an error due to the ambiguity and the command is aborted. |
| |
| @kindex show multiple-symbols |
| @item show multiple-symbols |
| Show the current value of the @code{multiple-symbols} setting. |
| @end table |
| |
| @node Variables |
| @section Program Variables |
| |
| The most common kind of expression to use is the name of a variable |
| in your program. |
| |
| Variables in expressions are understood in the selected stack frame |
| (@pxref{Selection, ,Selecting a Frame}); they must be either: |
| |
| @itemize @bullet |
| @item |
| global (or file-static) |
| @end itemize |
| |
| @noindent or |
| |
| @itemize @bullet |
| @item |
| visible according to the scope rules of the |
| programming language from the point of execution in that frame |
| @end itemize |
| |
| @noindent This means that in the function |
| |
| @smallexample |
| foo (a) |
| int a; |
| @{ |
| bar (a); |
| @{ |
| int b = test (); |
| bar (b); |
| @} |
| @} |
| @end smallexample |
| |
| @noindent |
| you can examine and use the variable @code{a} whenever your program is |
| executing within the function @code{foo}, but you can only use or |
| examine the variable @code{b} while your program is executing inside |
| the block where @code{b} is declared. |
| |
| @cindex variable name conflict |
| There is an exception: you can refer to a variable or function whose |
| scope is a single source file even if the current execution point is not |
| in this file. But it is possible to have more than one such variable or |
| function with the same name (in different source files). If that |
| happens, referring to that name has unpredictable effects. If you wish, |
| you can specify a static variable in a particular function or file by |
| using the colon-colon (@code{::}) notation: |
| |
| @cindex colon-colon, context for variables/functions |
| @ifnotinfo |
| @c info cannot cope with a :: index entry, but why deprive hard copy readers? |
| @cindex @code{::}, context for variables/functions |
| @end ifnotinfo |
| @smallexample |
| @var{file}::@var{variable} |
| @var{function}::@var{variable} |
| @end smallexample |
| |
| @noindent |
| Here @var{file} or @var{function} is the name of the context for the |
| static @var{variable}. In the case of file names, you can use quotes to |
| make sure @value{GDBN} parses the file name as a single word---for example, |
| to print a global value of @code{x} defined in @file{f2.c}: |
| |
| @smallexample |
| (@value{GDBP}) p 'f2.c'::x |
| @end smallexample |
| |
| The @code{::} notation is normally used for referring to |
| static variables, since you typically disambiguate uses of local variables |
| in functions by selecting the appropriate frame and using the |
| simple name of the variable. However, you may also use this notation |
| to refer to local variables in frames enclosing the selected frame: |
| |
| @smallexample |
| void |
| foo (int a) |
| @{ |
| if (a < 10) |
| bar (a); |
| else |
| process (a); /* Stop here */ |
| @} |
| |
| int |
| bar (int a) |
| @{ |
| foo (a + 5); |
| @} |
| @end smallexample |
| |
| @noindent |
| For example, if there is a breakpoint at the commented line, |
| here is what you might see |
| when the program stops after executing the call @code{bar(0)}: |
| |
| @smallexample |
| (@value{GDBP}) p a |
| $1 = 10 |
| (@value{GDBP}) p bar::a |
| $2 = 5 |
| (@value{GDBP}) up 2 |
| #2 0x080483d0 in foo (a=5) at foobar.c:12 |
| (@value{GDBP}) p a |
| $3 = 5 |
| (@value{GDBP}) p bar::a |
| $4 = 0 |
| @end smallexample |
| |
| @cindex C@t{++} scope resolution |
| These uses of @samp{::} are very rarely in conflict with the very similar |
| use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++} |
| scope resolution operator in @value{GDBN} expressions. |
| @c FIXME: Um, so what happens in one of those rare cases where it's in |
| @c conflict?? --mew |
| |
| @cindex wrong values |
| @cindex variable values, wrong |
| @cindex function entry/exit, wrong values of variables |
| @cindex optimized code, wrong values of variables |
| @quotation |
| @emph{Warning:} Occasionally, a local variable may appear to have the |
| wrong value at certain points in a function---just after entry to a new |
| scope, and just before exit. |
| @end quotation |
| You may see this problem when you are stepping by machine instructions. |
| This is because, on most machines, it takes more than one instruction to |
| set up a stack frame (including local variable definitions); if you are |
| stepping by machine instructions, variables may appear to have the wrong |
| values until the stack frame is completely built. On exit, it usually |
| also takes more than one machine instruction to destroy a stack frame; |
| after you begin stepping through that group of instructions, local |
| variable definitions may be gone. |
| |
| This may also happen when the compiler does significant optimizations. |
| To be sure of always seeing accurate values, turn off all optimization |
| when compiling. |
| |
| @cindex ``No symbol "foo" in current context'' |
| Another possible effect of compiler optimizations is to optimize |
| unused variables out of existence, or assign variables to registers (as |
| opposed to memory addresses). Depending on the support for such cases |
| offered by the debug info format used by the compiler, @value{GDBN} |
| might not be able to display values for such local variables. If that |
| happens, @value{GDBN} will print a message like this: |
| |
| @smallexample |
| No symbol "foo" in current context. |
| @end smallexample |
| |
| To solve such problems, either recompile without optimizations, or use a |
| different debug info format, if the compiler supports several such |
| formats. @xref{Compilation}, for more information on choosing compiler |
| options. @xref{C, ,C and C@t{++}}, for more information about debug |
| info formats that are best suited to C@t{++} programs. |
| |
| If you ask to print an object whose contents are unknown to |
| @value{GDBN}, e.g., because its data type is not completely specified |
| by the debug information, @value{GDBN} will say @samp{<incomplete |
| type>}. @xref{Symbols, incomplete type}, for more about this. |
| |
| If you append @kbd{@@entry} string to a function parameter name you get its |
| value at the time the function got called. If the value is not available an |
| error message is printed. Entry values are available only with some compilers. |
| Entry values are normally also printed at the function parameter list according |
| to @ref{set print entry-values}. |
| |
| @smallexample |
| Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29 |
| 29 i++; |
| (gdb) next |
| 30 e (i); |
| (gdb) print i |
| $1 = 31 |
| (gdb) print i@@entry |
| $2 = 30 |
| @end smallexample |
| |
| Strings are identified as arrays of @code{char} values without specified |
| signedness. Arrays of either @code{signed char} or @code{unsigned char} get |
| printed as arrays of 1 byte sized integers. @code{-fsigned-char} or |
| @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN} |
| defines literal string type @code{"char"} as @code{char} without a sign. |
| For program code |
| |
| @smallexample |
| char var0[] = "A"; |
| signed char var1[] = "A"; |
| @end smallexample |
| |
| You get during debugging |
| @smallexample |
| (gdb) print var0 |
| $1 = "A" |
| (gdb) print var1 |
| $2 = @{65 'A', 0 '\0'@} |
| @end smallexample |
| |
| @node Arrays |
| @section Artificial Arrays |
| |
| @cindex artificial array |
| @cindex arrays |
| @kindex @@@r{, referencing memory as an array} |
| It is often useful to print out several successive objects of the |
| same type in memory; a section of an array, or an array of |
| dynamically determined size for which only a pointer exists in the |
| program. |
| |
| You can do this by referring to a contiguous span of memory as an |
| @dfn{artificial array}, using the binary operator @samp{@@}. The left |
| operand of @samp{@@} should be the first element of the desired array |
| and be an individual object. The right operand should be the desired length |
| of the array. The result is an array value whose elements are all of |
| the type of the left argument. The first element is actually the left |
| argument; the second element comes from bytes of memory immediately |
| following those that hold the first element, and so on. Here is an |
| example. If a program says |
| |
| @smallexample |
| int *array = (int *) malloc (len * sizeof (int)); |
| @end smallexample |
| |
| @noindent |
| you can print the contents of @code{array} with |
| |
| @smallexample |
| p *array@@len |
| @end smallexample |
| |
| The left operand of @samp{@@} must reside in memory. Array values made |
| with @samp{@@} in this way behave just like other arrays in terms of |
| subscripting, and are coerced to pointers when used in expressions. |
| Artificial arrays most often appear in expressions via the value history |
| (@pxref{Value History, ,Value History}), after printing one out. |
| |
| Another way to create an artificial array is to use a cast. |
| This re-interprets a value as if it were an array. |
| The value need not be in memory: |
| @smallexample |
| (@value{GDBP}) p/x (short[2])0x12345678 |
| $1 = @{0x1234, 0x5678@} |
| @end smallexample |
| |
| As a convenience, if you leave the array length out (as in |
| @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill |
| the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}: |
| @smallexample |
| (@value{GDBP}) p/x (short[])0x12345678 |
| $2 = @{0x1234, 0x5678@} |
| @end smallexample |
| |
| Sometimes the artificial array mechanism is not quite enough; in |
| moderately complex data structures, the elements of interest may not |
| actually be adjacent---for example, if you are interested in the values |
| of pointers in an array. One useful work-around in this situation is |
| to use a convenience variable (@pxref{Convenience Vars, ,Convenience |
| Variables}) as a counter in an expression that prints the first |
| interesting value, and then repeat that expression via @key{RET}. For |
| instance, suppose you have an array @code{dtab} of pointers to |
| structures, and you are interested in the values of a field @code{fv} |
| in each structure. Here is an example of what you might type: |
| |
| @smallexample |
| set $i = 0 |
| p dtab[$i++]->fv |
| @key{RET} |
| @key{RET} |
| @dots{} |
| @end smallexample |
| |
| @node Output Formats |
| @section Output Formats |
| |
| @cindex formatted output |
| @cindex output formats |
| By default, @value{GDBN} prints a value according to its data type. Sometimes |
| this is not what you want. For example, you might want to print a number |
| in hex, or a pointer in decimal. Or you might want to view data in memory |
| at a certain address as a character string or as an instruction. To do |
| these things, specify an @dfn{output format} when you print a value. |
| |
| The simplest use of output formats is to say how to print a value |
| already computed. This is done by starting the arguments of the |
| @code{print} command with a slash and a format letter. The format |
| letters supported are: |
| |
| @table @code |
| @item x |
| Regard the bits of the value as an integer, and print the integer in |
| hexadecimal. |
| |
| @item d |
| Print as integer in signed decimal. |
| |
| @item u |
| Print as integer in unsigned decimal. |
| |
| @item o |
| Print as integer in octal. |
| |
| @item t |
| Print as integer in binary. The letter @samp{t} stands for ``two''. |
| @footnote{@samp{b} cannot be used because these format letters are also |
| used with the @code{x} command, where @samp{b} stands for ``byte''; |
| see @ref{Memory,,Examining Memory}.} |
| |
| @item a |
| @cindex unknown address, locating |
| @cindex locate address |
| Print as an address, both absolute in hexadecimal and as an offset from |
| the nearest preceding symbol. You can use this format used to discover |
| where (in what function) an unknown address is located: |
| |
| @smallexample |
| (@value{GDBP}) p/a 0x54320 |
| $3 = 0x54320 <_initialize_vx+396> |
| @end smallexample |
| |
| @noindent |
| The command @code{info symbol 0x54320} yields similar results. |
| @xref{Symbols, info symbol}. |
| |
| @item c |
| Regard as an integer and print it as a character constant. This |
| prints both the numerical value and its character representation. The |
| character representation is replaced with the octal escape @samp{\nnn} |
| for characters outside the 7-bit @sc{ascii} range. |
| |
| Without this format, @value{GDBN} displays @code{char}, |
| @w{@code{unsigned char}}, and @w{@code{signed char}} data as character |
| constants. Single-byte members of vectors are displayed as integer |
| data. |
| |
| @item f |
| Regard the bits of the value as a floating point number and print |
| using typical floating point syntax. |
| |
| @item s |
| @cindex printing strings |
| @cindex printing byte arrays |
| Regard as a string, if possible. With this format, pointers to single-byte |
| data are displayed as null-terminated strings and arrays of single-byte data |
| are displayed as fixed-length strings. Other values are displayed in their |
| natural types. |
| |
| Without this format, @value{GDBN} displays pointers to and arrays of |
| @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as |
| strings. Single-byte members of a vector are displayed as an integer |
| array. |
| |
| @item r |
| @cindex raw printing |
| Print using the @samp{raw} formatting. By default, @value{GDBN} will |
| use a Python-based pretty-printer, if one is available (@pxref{Pretty |
| Printing}). This typically results in a higher-level display of the |
| value's contents. The @samp{r} format bypasses any Python |
| pretty-printer which might exist. |
| @end table |
| |
| For example, to print the program counter in hex (@pxref{Registers}), type |
| |
| @smallexample |
| p/x $pc |
| @end smallexample |
| |
| @noindent |
| Note that no space is required before the slash; this is because command |
| names in @value{GDBN} cannot contain a slash. |
| |
| To reprint the last value in the value history with a different format, |
| you can use the @code{print} command with just a format and no |
| expression. For example, @samp{p/x} reprints the last value in hex. |
| |
| @node Memory |
| @section Examining Memory |
| |
| You can use the command @code{x} (for ``examine'') to examine memory in |
| any of several formats, independently of your program's data types. |
| |
| @cindex examining memory |
| @table @code |
| @kindex x @r{(examine memory)} |
| @item x/@var{nfu} @var{addr} |
| @itemx x @var{addr} |
| @itemx x |
| Use the @code{x} command to examine memory. |
| @end table |
| |
| @var{n}, @var{f}, and @var{u} are all optional parameters that specify how |
| much memory to display and how to format it; @var{addr} is an |
| expression giving the address where you want to start displaying memory. |
| If you use defaults for @var{nfu}, you need not type the slash @samp{/}. |
| Several commands set convenient defaults for @var{addr}. |
| |
| @table @r |
| @item @var{n}, the repeat count |
| The repeat count is a decimal integer; the default is 1. It specifies |
| how much memory (counting by units @var{u}) to display. |
| @c This really is **decimal**; unaffected by 'set radix' as of GDB |
| @c 4.1.2. |
| |
| @item @var{f}, the display format |
| The display format is one of the formats used by @code{print} |
| (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c}, |
| @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions). |
| The default is @samp{x} (hexadecimal) initially. The default changes |
| each time you use either @code{x} or @code{print}. |
| |
| @item @var{u}, the unit size |
| The unit size is any of |
| |
| @table @code |
| @item b |
| Bytes. |
| @item h |
| Halfwords (two bytes). |
| @item w |
| Words (four bytes). This is the initial default. |
| @item g |
| Giant words (eight bytes). |
| @end table |
| |
| Each time you specify a unit size with @code{x}, that size becomes the |
| default unit the next time you use @code{x}. For the @samp{i} format, |
| the unit size is ignored and is normally not written. For the @samp{s} format, |
| the unit size defaults to @samp{b}, unless it is explicitly given. |
| Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display |
| 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings. |
| Note that the results depend on the programming language of the |
| current compilation unit. If the language is C, the @samp{s} |
| modifier will use the UTF-16 encoding while @samp{w} will use |
| UTF-32. The encoding is set by the programming language and cannot |
| be altered. |
| |
| @item @var{addr}, starting display address |
| @var{addr} is the address where you want @value{GDBN} to begin displaying |
| memory. The expression need not have a pointer value (though it may); |
| it is always interpreted as an integer address of a byte of memory. |
| @xref{Expressions, ,Expressions}, for more information on expressions. The default for |
| @var{addr} is usually just after the last address examined---but several |
| other commands also set the default address: @code{info breakpoints} (to |
| the address of the last breakpoint listed), @code{info line} (to the |
| starting address of a line), and @code{print} (if you use it to display |
| a value from memory). |
| @end table |
| |
| For example, @samp{x/3uh 0x54320} is a request to display three halfwords |
| (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}), |
| starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four |
| words (@samp{w}) of memory above the stack pointer (here, @samp{$sp}; |
| @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}). |
| |
| Since the letters indicating unit sizes are all distinct from the |
| letters specifying output formats, you do not have to remember whether |
| unit size or format comes first; either order works. The output |
| specifications @samp{4xw} and @samp{4wx} mean exactly the same thing. |
| (However, the count @var{n} must come first; @samp{wx4} does not work.) |
| |
| Even though the unit size @var{u} is ignored for the formats @samp{s} |
| and @samp{i}, you might still want to use a count @var{n}; for example, |
| @samp{3i} specifies that you want to see three machine instructions, |
| including any operands. For convenience, especially when used with |
| the @code{display} command, the @samp{i} format also prints branch delay |
| slot instructions, if any, beyond the count specified, which immediately |
| follow the last instruction that is within the count. The command |
| @code{disassemble} gives an alternative way of inspecting machine |
| instructions; see @ref{Machine Code,,Source and Machine Code}. |
| |
| All the defaults for the arguments to @code{x} are designed to make it |
| easy to continue scanning memory with minimal specifications each time |
| you use @code{x}. For example, after you have inspected three machine |
| instructions with @samp{x/3i @var{addr}}, you can inspect the next seven |
| with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command, |
| the repeat count @var{n} is used again; the other arguments default as |
| for successive uses of @code{x}. |
| |
| When examining machine instructions, the instruction at current program |
| counter is shown with a @code{=>} marker. For example: |
| |
| @smallexample |
| (@value{GDBP}) x/5i $pc-6 |
| 0x804837f <main+11>: mov %esp,%ebp |
| 0x8048381 <main+13>: push %ecx |
| 0x8048382 <main+14>: sub $0x4,%esp |
| => 0x8048385 <main+17>: movl $0x8048460,(%esp) |
| 0x804838c <main+24>: call 0x80482d4 <puts@@plt> |
| @end smallexample |
| |
| @cindex @code{$_}, @code{$__}, and value history |
| The addresses and contents printed by the @code{x} command are not saved |
| in the value history because there is often too much of them and they |
| would get in the way. Instead, @value{GDBN} makes these values available for |
| subsequent use in expressions as values of the convenience variables |
| @code{$_} and @code{$__}. After an @code{x} command, the last address |
| examined is available for use in expressions in the convenience variable |
| @code{$_}. The contents of that address, as examined, are available in |
| the convenience variable @code{$__}. |
| |
| If the @code{x} command has a repeat count, the address and contents saved |
| are from the last memory unit printed; this is not the same as the last |
| address printed if several units were printed on the last line of output. |
| |
| @cindex remote memory comparison |
| @cindex verify remote memory image |
| When you are debugging a program running on a remote target machine |
| (@pxref{Remote Debugging}), you may wish to verify the program's image in the |
| remote machine's memory against the executable file you downloaded to |
| the target. The @code{compare-sections} command is provided for such |
| situations. |
| |
| @table @code |
| @kindex compare-sections |
| @item compare-sections @r{[}@var{section-name}@r{]} |
| Compare the data of a loadable section @var{section-name} in the |
| executable file of the program being debugged with the same section in |
| the remote machine's memory, and report any mismatches. With no |
| arguments, compares all loadable sections. This command's |
| availability depends on the target's support for the @code{"qCRC"} |
| remote request. |
| @end table |
| |
| @node Auto Display |
| @section Automatic Display |
| @cindex automatic display |
| @cindex display of expressions |
| |
| If you find that you want to print the value of an expression frequently |
| (to see how it changes), you might want to add it to the @dfn{automatic |
| display list} so that @value{GDBN} prints its value each time your program stops. |
| Each expression added to the list is given a number to identify it; |
| to remove an expression from the list, you specify that number. |
| The automatic display looks like this: |
| |
| @smallexample |
| 2: foo = 38 |
| 3: bar[5] = (struct hack *) 0x3804 |
| @end smallexample |
| |
| @noindent |
| This display shows item numbers, expressions and their current values. As with |
| displays you request manually using @code{x} or @code{print}, you can |
| specify the output format you prefer; in fact, @code{display} decides |
| whether to use @code{print} or @code{x} depending your format |
| specification---it uses @code{x} if you specify either the @samp{i} |
| or @samp{s} format, or a unit size; otherwise it uses @code{print}. |
| |
| @table @code |
| @kindex display |
| @item display @var{expr} |
| Add the expression @var{expr} to the list of expressions to display |
| each time your program stops. @xref{Expressions, ,Expressions}. |
| |
| @code{display} does not repeat if you press @key{RET} again after using it. |
| |
| @item display/@var{fmt} @var{expr} |
| For @var{fmt} specifying only a display format and not a size or |
| count, add the expression @var{expr} to the auto-display list but |
| arrange to display it each time in the specified format @var{fmt}. |
| @xref{Output Formats,,Output Formats}. |
| |
| @item display/@var{fmt} @var{addr} |
| For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a |
| number of units, add the expression @var{addr} as a memory address to |
| be examined each time your program stops. Examining means in effect |
| doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}. |
| @end table |
| |
| For example, @samp{display/i $pc} can be helpful, to see the machine |
| instruction about to be executed each time execution stops (@samp{$pc} |
| is a common name for the program counter; @pxref{Registers, ,Registers}). |
| |
| @table @code |
| @kindex delete display |
| @kindex undisplay |
| @item undisplay @var{dnums}@dots{} |
| @itemx delete display @var{dnums}@dots{} |
| Remove items from the list of expressions to display. Specify the |
| numbers of the displays that you want affected with the command |
| argument @var{dnums}. It can be a single display number, one of the |
| numbers shown in the first field of the @samp{info display} display; |
| or it could be a range of display numbers, as in @code{2-4}. |
| |
| @code{undisplay} does not repeat if you press @key{RET} after using it. |
| (Otherwise you would just get the error @samp{No display number @dots{}}.) |
| |
| @kindex disable display |
| @item disable display @var{dnums}@dots{} |
| Disable the display of item numbers @var{dnums}. A disabled display |
| item is not printed automatically, but is not forgotten. It may be |
| enabled again later. Specify the numbers of the displays that you |
| want affected with the command argument @var{dnums}. It can be a |
| single display number, one of the numbers shown in the first field of |
| the @samp{info display} display; or it could be a range of display |
| numbers, as in @code{2-4}. |
| |
| @kindex enable display |
| @item enable display @var{dnums}@dots{} |
| Enable display of item numbers @var{dnums}. It becomes effective once |
| again in auto display of its expression, until you specify otherwise. |
| Specify the numbers of the displays that you want affected with the |
| command argument @var{dnums}. It can be a single display number, one |
| of the numbers shown in the first field of the @samp{info display} |
| display; or it could be a range of display numbers, as in @code{2-4}. |
| |
| @item display |
| Display the current values of the expressions on the list, just as is |
| done when your program stops. |
| |
| @kindex info display |
| @item info display |
| Print the list of expressions previously set up to display |
| automatically, each one with its item number, but without showing the |
| values. This includes disabled expressions, which are marked as such. |
| It also includes expressions which would not be displayed right now |
| because they refer to automatic variables not currently available. |
| @end table |
| |
| @cindex display disabled out of scope |
| If a display expression refers to local variables, then it does not make |
| sense outside the lexical context for which it was set up. Such an |
| expression is disabled when execution enters a context where one of its |
| variables is not defined. For example, if you give the command |
| @code{display last_char} while inside a function with an argument |
| @code{last_char}, @value{GDBN} displays this argument while your program |
| continues to stop inside that function. When it stops elsewhere---where |
| there is no variable @code{last_char}---the display is disabled |
| automatically. The next time your program stops where @code{last_char} |
| is meaningful, you can enable the display expression once again. |
| |
| @node Print Settings |
| @section Print Settings |
| |
| @cindex format options |
| @cindex print settings |
| @value{GDBN} provides the following ways to control how arrays, structures, |
| and symbols are printed. |
| |
| @noindent |
| These settings are useful for debugging programs in any language: |
| |
| @table @code |
| @kindex set print |
| @item set print address |
| @itemx set print address on |
| @cindex print/don't print memory addresses |
| @value{GDBN} prints memory addresses showing the location of stack |
| traces, structure values, pointer values, breakpoints, and so forth, |
| even when it also displays the contents of those addresses. The default |
| is @code{on}. For example, this is what a stack frame display looks like with |
| @code{set print address on}: |
| |
| @smallexample |
| @group |
| (@value{GDBP}) f |
| #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") |
| at input.c:530 |
| 530 if (lquote != def_lquote) |
| @end group |
| @end smallexample |
| |
| @item set print address off |
| Do not print addresses when displaying their contents. For example, |
| this is the same stack frame displayed with @code{set print address off}: |
| |
| @smallexample |
| @group |
| (@value{GDBP}) set print addr off |
| (@value{GDBP}) f |
| #0 set_quotes (lq="<<", rq=">>") at input.c:530 |
| 530 if (lquote != def_lquote) |
| @end group |
| @end smallexample |
| |
| You can use @samp{set print address off} to eliminate all machine |
| dependent displays from the @value{GDBN} interface. For example, with |
| @code{print address off}, you should get the same text for backtraces on |
| all machines---whether or not they involve pointer arguments. |
| |
| @kindex show print |
| @item show print address |
| Show whether or not addresses are to be printed. |
| @end table |
| |
| When @value{GDBN} prints a symbolic address, it normally prints the |
| closest earlier symbol plus an offset. If that symbol does not uniquely |
| identify the address (for example, it is a name whose scope is a single |
| source file), you may need to clarify. One way to do this is with |
| @code{info line}, for example @samp{info line *0x4537}. Alternately, |
| you can set @value{GDBN} to print the source file and line number when |
| it prints a symbolic address: |
| |
| @table @code |
| @item set print symbol-filename on |
| @cindex source file and line of a symbol |
| @cindex symbol, source file and line |
| Tell @value{GDBN} to print the source file name and line number of a |
| symbol in the symbolic form of an address. |
| |
| @item set print symbol-filename off |
| Do not print source file name and line number of a symbol. This is the |
| default. |
| |
| @item show print symbol-filename |
| Show whether or not @value{GDBN} will print the source file name and |
| line number of a symbol in the symbolic form of an address. |
| @end table |
| |
| Another situation where it is helpful to show symbol filenames and line |
| numbers is when disassembling code; @value{GDBN} shows you the line |
| number and source file that corresponds to each instruction. |
| |
| Also, you may wish to see the symbolic form only if the address being |
| printed is reasonably close to the closest earlier symbol: |
| |
| @table @code |
| @item set print max-symbolic-offset @var{max-offset} |
| @cindex maximum value for offset of closest symbol |
| Tell @value{GDBN} to only display the symbolic form of an address if the |
| offset between the closest earlier symbol and the address is less than |
| @var{max-offset}. The default is 0, which tells @value{GDBN} |
| to always print the symbolic form of an address if any symbol precedes it. |
| |
| @item show print max-symbolic-offset |
| Ask how large the maximum offset is that @value{GDBN} prints in a |
| symbolic address. |
| @end table |
| |
| @cindex wild pointer, interpreting |
| @cindex pointer, finding referent |
| If you have a pointer and you are not sure where it points, try |
| @samp{set print symbol-filename on}. Then you can determine the name |
| and source file location of the variable where it points, using |
| @samp{p/a @var{pointer}}. This interprets the address in symbolic form. |
| For example, here @value{GDBN} shows that a variable @code{ptt} points |
| at another variable @code{t}, defined in @file{hi2.c}: |
| |
| @smallexample |
| (@value{GDBP}) set print symbol-filename on |
| (@value{GDBP}) p/a ptt |
| $4 = 0xe008 <t in hi2.c> |
| @end smallexample |
| |
| @quotation |
| @emph{Warning:} For pointers that point to a local variable, @samp{p/a} |
| does not show the symbol name and filename of the referent, even with |
| the appropriate @code{set print} options turned on. |
| @end quotation |
| |
| You can also enable @samp{/a}-like formatting all the time using |
| @samp{set print symbol on}: |
| |
| @table @code |
| @item set print symbol on |
| Tell @value{GDBN} to print the symbol corresponding to an address, if |
| one exists. |
| |
| @item set print symbol off |
| Tell @value{GDBN} not to print the symbol corresponding to an |
| address. In this mode, @value{GDBN} will still print the symbol |
| corresponding to pointers to functions. This is the default. |
| |
| @item show print symbol |
| Show whether @value{GDBN} will display the symbol corresponding to an |
| address. |
| @end table |
| |
| Other settings control how different kinds of objects are printed: |
| |
| @table @code |
| @item set print array |
| @itemx set print array on |
| @cindex pretty print arrays |
| Pretty print arrays. This format is more convenient to read, |
| but uses more space. The default is off. |
| |
| @item set print array off |
| Return to compressed format for arrays. |
| |
| @item show print array |
| Show whether compressed or pretty format is selected for displaying |
| arrays. |
| |
| @cindex print array indexes |
| @item set print array-indexes |
| @itemx set print array-indexes on |
| Print the index of each element when displaying arrays. May be more |
| convenient to locate a given element in the array or quickly find the |
| index of a given element in that printed array. The default is off. |
| |
| @item set print array-indexes off |
| Stop printing element indexes when displaying arrays. |
| |
| @item show print array-indexes |
| Show whether the index of each element is printed when displaying |
| arrays. |
| |
| @item set print elements @var{number-of-elements} |
| @cindex number of array elements to print |
| @cindex limit on number of printed array elements |
| Set a limit on how many elements of an array @value{GDBN} will print. |
| If @value{GDBN} is printing a large array, it stops printing after it has |
| printed the number of elements set by the @code{set print elements} command. |
| This limit also applies to the display of strings. |
| When @value{GDBN} starts, this limit is set to 200. |
| Setting @var{number-of-elements} to zero means that the printing is unlimited. |
| |
| @item show print elements |
| Display the number of elements of a large array that @value{GDBN} will print. |
| If the number is 0, then the printing is unlimited. |
| |
| @item set print frame-arguments @var{value} |
| @kindex set print frame-arguments |
| @cindex printing frame argument values |
| @cindex print all frame argument values |
| @cindex print frame argument values for scalars only |
| @cindex do not print frame argument values |
| This command allows to control how the values of arguments are printed |
| when the debugger prints a frame (@pxref{Frames}). The possible |
| values are: |
| |
| @table @code |
| @item all |
| The values of all arguments are printed. |
| |
| @item scalars |
| Print the value of an argument only if it is a scalar. The value of more |
| complex arguments such as arrays, structures, unions, etc, is replaced |
| by @code{@dots{}}. This is the default. Here is an example where |
| only scalar arguments are shown: |
| |
| @smallexample |
| #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green) |
| at frame-args.c:23 |
| @end smallexample |
| |
| @item none |
| None of the argument values are printed. Instead, the value of each argument |
| is replaced by @code{@dots{}}. In this case, the example above now becomes: |
| |
| @smallexample |
| #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{}) |
| at frame-args.c:23 |
| @end smallexample |
| @end table |
| |
| By default, only scalar arguments are printed. This command can be used |
| to configure the debugger to print the value of all arguments, regardless |
| of their type. However, it is often advantageous to not print the value |
| of more complex parameters. For instance, it reduces the amount of |
| information printed in each frame, making the backtrace more readable. |
| Also, it improves performance when displaying Ada frames, because |
| the computation of large arguments can sometimes be CPU-intensive, |
| especially in large applications. Setting @code{print frame-arguments} |
| to @code{scalars} (the default) or @code{none} avoids this computation, |
| thus speeding up the display of each Ada frame. |
| |
| @item show print frame-arguments |
| Show how the value of arguments should be displayed when printing a frame. |
| |
| @anchor{set print entry-values} |
| @item set print entry-values @var{value} |
| @kindex set print entry-values |
| Set printing of frame argument values at function entry. In some cases |
| @value{GDBN} can determine the value of function argument which was passed by |
| the function caller, even if the value was modified inside the called function |
| and therefore is different. With optimized code, the current value could be |
| unavailable, but the entry value may still be known. |
| |
| The default value is @code{default} (see below for its description). Older |
| @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting |
| this feature will behave in the @code{default} setting the same way as with the |
| @code{no} setting. |
| |
| This functionality is currently supported only by DWARF 2 debugging format and |
| the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With |
| @value{NGCC}, you need to specify @option{-O -g} during compilation, to get |
| this information. |
| |
| The @var{value} parameter can be one of the following: |
| |
| @table @code |
| @item no |
| Print only actual parameter values, never print values from function entry |
| point. |
| @smallexample |
| #0 equal (val=5) |
| #0 different (val=6) |
| #0 lost (val=<optimized out>) |
| #0 born (val=10) |
| #0 invalid (val=<optimized out>) |
| @end smallexample |
| |
| @item only |
| Print only parameter values from function entry point. The actual parameter |
| values are never printed. |
| @smallexample |
| #0 equal (val@@entry=5) |
| #0 different (val@@entry=5) |
| #0 lost (val@@entry=5) |
| #0 born (val@@entry=<optimized out>) |
| #0 invalid (val@@entry=<optimized out>) |
| @end smallexample |
| |
| @item preferred |
| Print only parameter values from function entry point. If value from function |
| entry point is not known while the actual value is known, print the actual |
| value for such parameter. |
| @smallexample |
| #0 equal (val@@entry=5) |
| #0 different (val@@entry=5) |
| #0 lost (val@@entry=5) |
| #0 born (val=10) |
| #0 invalid (val@@entry=<optimized out>) |
| @end smallexample |
| |
| @item if-needed |
| Print actual parameter values. If actual parameter value is not known while |
| value from function entry point is known, print the entry point value for such |
| parameter. |
| @smallexample |
| #0 equal (val=5) |
| #0 different (val=6) |
| #0 lost (val@@entry=5) |
| #0 born (val=10) |
| #0 invalid (val=<optimized out>) |
| @end smallexample |
| |
| @item both |
| Always print both the actual parameter value and its value from function entry |
| point, even if values of one or both are not available due to compiler |
| optimizations. |
| @smallexample |
| #0 equal (val=5, val@@entry=5) |
| #0 different (val=6, val@@entry=5) |
| #0 lost (val=<optimized out>, val@@entry=5) |
| #0 born (val=10, val@@entry=<optimized out>) |
| #0 invalid (val=<optimized out>, val@@entry=<optimized out>) |
| @end smallexample |
| |
| @item compact |
| Print the actual parameter value if it is known and also its value from |
| function entry point if it is known. If neither is known, print for the actual |
| value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both |
| values are known and identical, print the shortened |
| @code{param=param@@entry=VALUE} notation. |
| @smallexample |
| #0 equal (val=val@@entry=5) |
| #0 different (val=6, val@@entry=5) |
| #0 lost (val@@entry=5) |
| #0 born (val=10) |
| #0 invalid (val=<optimized out>) |
| @end smallexample |
| |
| @item default |
| Always print the actual parameter value. Print also its value from function |
| entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and |
| if both values are known and identical, print the shortened |
| @code{param=param@@entry=VALUE} notation. |
| @smallexample |
| #0 equal (val=val@@entry=5) |
| #0 different (val=6, val@@entry=5) |
| #0 lost (val=<optimized out>, val@@entry=5) |
| #0 born (val=10) |
| #0 invalid (val=<optimized out>) |
| @end smallexample |
| @end table |
| |
| For analysis messages on possible failures of frame argument values at function |
| entry resolution see @ref{set debug entry-values}. |
| |
| @item show print entry-values |
| Show the method being used for printing of frame argument values at function |
| entry. |
| |
| @item set print repeats |
| @cindex repeated array elements |
| Set the threshold for suppressing display of repeated array |
| elements. When the number of consecutive identical elements of an |
| array exceeds the threshold, @value{GDBN} prints the string |
| @code{"<repeats @var{n} times>"}, where @var{n} is the number of |
| identical repetitions, instead of displaying the identical elements |
| themselves. Setting the threshold to zero will cause all elements to |
| be individually printed. The default threshold is 10. |
| |
| @item show print repeats |
| Display the current threshold for printing repeated identical |
| elements. |
| |
| @item set print null-stop |
| @cindex @sc{null} elements in arrays |
| Cause @value{GDBN} to stop printing the characters of an array when the first |
| @sc{null} is encountered. This is useful when large arrays actually |
| contain only short strings. |
| The default is off. |
| |
| @item show print null-stop |
| Show whether @value{GDBN} stops printing an array on the first |
| @sc{null} character. |
| |
| @item set print pretty on |
| @cindex print structures in indented form |
| @cindex indentation in structure display |
| Cause @value{GDBN} to print structures in an indented format with one member |
| per line, like this: |
| |
| @smallexample |
| @group |
| $1 = @{ |
| next = 0x0, |
| flags = @{ |
| sweet = 1, |
| sour = 1 |
| @}, |
| meat = 0x54 "Pork" |
| @} |
| @end group |
| @end smallexample |
| |
| @item set print pretty off |
| Cause @value{GDBN} to print structures in a compact format, like this: |
| |
| @smallexample |
| @group |
| $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \ |
| meat = 0x54 "Pork"@} |
| @end group |
| @end smallexample |
| |
| @noindent |
| This is the default format. |
| |
| @item show print pretty |
| Show which format @value{GDBN} is using to print structures. |
| |
| @item set print sevenbit-strings on |
| @cindex eight-bit characters in strings |
| @cindex octal escapes in strings |
| Print using only seven-bit characters; if this option is set, |
| @value{GDBN} displays any eight-bit characters (in strings or |
| character values) using the notation @code{\}@var{nnn}. This setting is |
| best if you are working in English (@sc{ascii}) and you use the |
| high-order bit of characters as a marker or ``meta'' bit. |
| |
| @item set print sevenbit-strings off |
| Print full eight-bit characters. This allows the use of more |
| international character sets, and is the default. |
| |
| @item show print sevenbit-strings |
| Show whether or not @value{GDBN} is printing only seven-bit characters. |
| |
| @item set print union on |
| @cindex unions in structures, printing |
| Tell @value{GDBN} to print unions which are contained in structures |
| and other unions. This is the default setting. |
| |
| @item set print union off |
| Tell @value{GDBN} not to print unions which are contained in |
| structures and other unions. @value{GDBN} will print @code{"@{...@}"} |
| instead. |
| |
| @item show print union |
| Ask @value{GDBN} whether or not it will print unions which are contained in |
| structures and other unions. |
| |
| For example, given the declarations |
| |
| @smallexample |
| typedef enum @{Tree, Bug@} Species; |
| typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms; |
| typedef enum @{Caterpillar, Cocoon, Butterfly@} |
| Bug_forms; |
| |
| struct thing @{ |
| Species it; |
| union @{ |
| Tree_forms tree; |
| Bug_forms bug; |
| @} form; |
| @}; |
| |
| struct thing foo = @{Tree, @{Acorn@}@}; |
| @end smallexample |
| |
| @noindent |
| with @code{set print union on} in effect @samp{p foo} would print |
| |
| @smallexample |
| $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@} |
| @end smallexample |
| |
| @noindent |
| and with @code{set print union off} in effect it would print |
| |
| @smallexample |
| $1 = @{it = Tree, form = @{...@}@} |
| @end smallexample |
| |
| @noindent |
| @code{set print union} affects programs written in C-like languages |
| and in Pascal. |
| @end table |
| |
| @need 1000 |
| @noindent |
| These settings are of interest when debugging C@t{++} programs: |
| |
| @table @code |
| @cindex demangling C@t{++} names |
| @item set print demangle |
| @itemx set print demangle on |
| Print C@t{++} names in their source form rather than in the encoded |
| (``mangled'') form passed to the assembler and linker for type-safe |
| linkage. The default is on. |
| |
| @item show print demangle |
| Show whether C@t{++} names are printed in mangled or demangled form. |
| |
| @item set print asm-demangle |
| @itemx set print asm-demangle on |
| Print C@t{++} names in their source form rather than their mangled form, even |
| in assembler code printouts such as instruction disassemblies. |
| The default is off. |
| |
| @item show print asm-demangle |
| Show whether C@t{++} names in assembly listings are printed in mangled |
| or demangled form. |
| |
| @cindex C@t{++} symbol decoding style |
| @cindex symbol decoding style, C@t{++} |
| @kindex set demangle-style |
| @item set demangle-style @var{style} |
| Choose among several encoding schemes used by different compilers to |
| represent C@t{++} names. The choices for @var{style} are currently: |
| |
| @table @code |
| @item auto |
| Allow @value{GDBN} to choose a decoding style by inspecting your program. |
| |
| @item gnu |
| Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm. |
| This is the default. |
| |
| @item hp |
| Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm. |
| |
| @item lucid |
| Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm. |
| |
| @item arm |
| Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}. |
| @strong{Warning:} this setting alone is not sufficient to allow |
| debugging @code{cfront}-generated executables. @value{GDBN} would |
| require further enhancement to permit that. |
| |
| @end table |
| If you omit @var{style}, you will see a list of possible formats. |
| |
| @item show demangle-style |
| Display the encoding style currently in use for decoding C@t{++} symbols. |
| |
| @item set print object |
| @itemx set print object on |
| @cindex derived type of an object, printing |
| @cindex display derived types |
| When displaying a pointer to an object, identify the @emph{actual} |
| (derived) type of the object rather than the @emph{declared} type, using |
| the virtual function table. Note that the virtual function table is |
| required---this feature can only work for objects that have run-time |
| type identification; a single virtual method in the object's declared |
| type is sufficient. Note that this setting is also taken into account when |
| working with variable objects via MI (@pxref{GDB/MI}). |
| |
| @item set print object off |
| Display only the declared type of objects, without reference to the |
| virtual function table. This is the default setting. |
| |
| @item show print object |
| Show whether actual, or declared, object types are displayed. |
| |
| @item set print static-members |
| @itemx set print static-members on |
| @cindex static members of C@t{++} objects |
| Print static members when displaying a C@t{++} object. The default is on. |
| |
| @item set print static-members off |
| Do not print static members when displaying a C@t{++} object. |
| |
| @item show print static-members |
| Show whether C@t{++} static members are printed or not. |
| |
| @item set print pascal_static-members |
| @itemx set print pascal_static-members on |
| @cindex static members of Pascal objects |
| @cindex Pascal objects, static members display |
| Print static members when displaying a Pascal object. The default is on. |
| |
| @item set print pascal_static-members off |
| Do not print static members when displaying a Pascal object. |
| |
| @item show print pascal_static-members |
| Show whether Pascal static members are printed or not. |
| |
| @c These don't work with HP ANSI C++ yet. |
| @item set print vtbl |
| @itemx set print vtbl on |
| @cindex pretty print C@t{++} virtual function tables |
| @cindex virtual functions (C@t{++}) display |
| @cindex VTBL display |
| Pretty print C@t{++} virtual function tables. The default is off. |
| (The @code{vtbl} commands do not work on programs compiled with the HP |
| ANSI C@t{++} compiler (@code{aCC}).) |
| |
| @item set print vtbl off |
| Do not pretty print C@t{++} virtual function tables. |
| |
| @item show print vtbl |
| Show whether C@t{++} virtual function tables are pretty printed, or not. |
| @end table |
| |
| @node Pretty Printing |
| @section Pretty Printing |
| |
| @value{GDBN} provides a mechanism to allow pretty-printing of values using |
| Python code. It greatly simplifies the display of complex objects. This |
| mechanism works for both MI and the CLI. |
| |
| @menu |
| * Pretty-Printer Introduction:: Introduction to pretty-printers |
| * Pretty-Printer Example:: An example pretty-printer |
| * Pretty-Printer Commands:: Pretty-printer commands |
| @end menu |
| |
| @node Pretty-Printer Introduction |
| @subsection Pretty-Printer Introduction |
| |
| When @value{GDBN} prints a value, it first sees if there is a pretty-printer |
| registered for the value. If there is then @value{GDBN} invokes the |
| pretty-printer to print the value. Otherwise the value is printed normally. |
| |
| Pretty-printers are normally named. This makes them easy to manage. |
| The @samp{info pretty-printer} command will list all the installed |
| pretty-printers with their names. |
| If a pretty-printer can handle multiple data types, then its |
| @dfn{subprinters} are the printers for the individual data types. |
| Each such subprinter has its own name. |
| The format of the name is @var{printer-name};@var{subprinter-name}. |
| |
| Pretty-printers are installed by @dfn{registering} them with @value{GDBN}. |
| Typically they are automatically loaded and registered when the corresponding |
| debug information is loaded, thus making them available without having to |
| do anything special. |
| |
| There are three places where a pretty-printer can be registered. |
| |
| @itemize @bullet |
| @item |
| Pretty-printers registered globally are available when debugging |
| all inferiors. |
| |
| @item |
| Pretty-printers registered with a program space are available only |
| when debugging that program. |
| @xref{Progspaces In Python}, for more details on program spaces in Python. |
| |
| @item |
| Pretty-printers registered with an objfile are loaded and unloaded |
| with the corresponding objfile (e.g., shared library). |
| @xref{Objfiles In Python}, for more details on objfiles in Python. |
| @end itemize |
| |
| @xref{Selecting Pretty-Printers}, for further information on how |
| pretty-printers are selected, |
| |
| @xref{Writing a Pretty-Printer}, for implementing pretty printers |
| for new types. |
| |
| @node Pretty-Printer Example |
| @subsection Pretty-Printer Example |
| |
| Here is how a C@t{++} @code{std::string} looks without a pretty-printer: |
| |
| @smallexample |
| (@value{GDBP}) print s |
| $1 = @{ |
| static npos = 4294967295, |
| _M_dataplus = @{ |
| <std::allocator<char>> = @{ |
| <__gnu_cxx::new_allocator<char>> = @{ |
| <No data fields>@}, <No data fields> |
| @}, |
| members of std::basic_string<char, std::char_traits<char>, |
| std::allocator<char> >::_Alloc_hider: |
| _M_p = 0x804a014 "abcd" |
| @} |
| @} |
| @end smallexample |
| |
| With a pretty-printer for @code{std::string} only the contents are printed: |
| |
| @smallexample |
| (@value{GDBP}) print s |
| $2 = "abcd" |
| @end smallexample |
| |
| @node Pretty-Printer Commands |
| @subsection Pretty-Printer Commands |
| @cindex pretty-printer commands |
| |
| @table @code |
| @kindex info pretty-printer |
| @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]] |
| Print the list of installed pretty-printers. |
| This includes disabled pretty-printers, which are marked as such. |
| |
| @var{object-regexp} is a regular expression matching the objects |
| whose pretty-printers to list. |
| Objects can be @code{global}, the program space's file |
| (@pxref{Progspaces In Python}), |
| and the object files within that program space (@pxref{Objfiles In Python}). |
| @xref{Selecting Pretty-Printers}, for details on how @value{GDBN} |
| looks up a printer from these three objects. |
| |
| @var{name-regexp} is a regular expression matching the name of the printers |
| to list. |
| |
| @kindex disable pretty-printer |
| @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]] |
| Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}. |
| A disabled pretty-printer is not forgotten, it may be enabled again later. |
| |
| @kindex enable pretty-printer |
| @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]] |
| Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}. |
| @end table |
| |
| Example: |
| |
| Suppose we have three pretty-printers installed: one from library1.so |
| named @code{foo} that prints objects of type @code{foo}, and |
| another from library2.so named @code{bar} that prints two types of objects, |
| @code{bar1} and @code{bar2}. |
| |
| @smallexample |
| (gdb) info pretty-printer |
| library1.so: |
| foo |
| library2.so: |
| bar |
| bar1 |
| bar2 |
| (gdb) info pretty-printer library2 |
| library2.so: |
| bar |
| bar1 |
| bar2 |
| (gdb) disable pretty-printer library1 |
| 1 printer disabled |
| 2 of 3 printers enabled |
| (gdb) info pretty-printer |
| library1.so: |
| foo [disabled] |
| library2.so: |
| bar |
| bar1 |
| bar2 |
| (gdb) disable pretty-printer library2 bar:bar1 |
| 1 printer disabled |
| 1 of 3 printers enabled |
| (gdb) info pretty-printer library2 |
| library1.so: |
| foo [disabled] |
| library2.so: |
| bar |
| bar1 [disabled] |
| bar2 |
| (gdb) disable pretty-printer library2 bar |
| 1 printer disabled |
| 0 of 3 printers enabled |
| (gdb) info pretty-printer library2 |
| library1.so: |
| foo [disabled] |
| library2.so: |
| bar [disabled] |
| bar1 [disabled] |
| bar2 |
| @end smallexample |
| |
| Note that for @code{bar} the entire printer can be disabled, |
| as can each individual subprinter. |
| |
| @node Value History |
| @section Value History |
| |
| @cindex value history |
| @cindex history of values printed by @value{GDBN} |
| Values printed by the @code{print} command are saved in the @value{GDBN} |
| @dfn{value history}. This allows you to refer to them in other expressions. |
| Values are kept until the symbol table is re-read or discarded |
| (for example with the @code{file} or @code{symbol-file} commands). |
| When the symbol table changes, the value history is discarded, |
| since the values may contain pointers back to the types defined in the |
| symbol table. |
| |
| @cindex @code{$} |
| @cindex @code{$$} |
| @cindex history number |
| The values printed are given @dfn{history numbers} by which you can |
| refer to them. These are successive integers starting with one. |
| @code{print} shows you the history number assigned to a value by |
| printing @samp{$@var{num} = } before the value; here @var{num} is the |
| history number. |
| |
| To refer to any previous value, use @samp{$} followed by the value's |
| history number. The way @code{print} labels its output is designed to |
| remind you of this. Just @code{$} refers to the most recent value in |
| the history, and @code{$$} refers to the value before that. |
| @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2} |
| is the value just prior to @code{$$}, @code{$$1} is equivalent to |
| @code{$$}, and @code{$$0} is equivalent to @code{$}. |
| |
| For example, suppose you have just printed a pointer to a structure and |
| want to see the contents of the structure. It suffices to type |
| |
| @smallexample |
| p *$ |
| @end smallexample |
| |
| If you have a chain of structures where the component @code{next} points |
| to the next one, you can print the contents of the next one with this: |
| |
| @smallexample |
| p *$.next |
| @end smallexample |
| |
| @noindent |
| You can print successive links in the chain by repeating this |
| command---which you can do by just typing @key{RET}. |
| |
| Note that the history records values, not expressions. If the value of |
| @code{x} is 4 and you type these commands: |
| |
| @smallexample |
| print x |
| set x=5 |
| @end smallexample |
| |
| @noindent |
| then the value recorded in the value history by the @code{print} command |
| remains 4 even though the value of @code{x} has changed. |
| |
| @table @code |
| @kindex show values |
| @item show values |
| Print the last ten values in the value history, with their item numbers. |
| This is like @samp{p@ $$9} repeated ten times, except that @code{show |
| values} does not change the history. |
| |
| @item show values @var{n} |
| Print ten history values centered on history item number @var{n}. |
| |
| @item show values + |
| Print ten history values just after the values last printed. If no more |
| values are available, @code{show values +} produces no display. |
| @end table |
| |
| Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the |
| same effect as @samp{show values +}. |
| |
| @node Convenience Vars |
| @section Convenience Variables |
| |
| @cindex convenience variables |
| @cindex user-defined variables |
| @value{GDBN} provides @dfn{convenience variables} that you can use within |
| @value{GDBN} to hold on to a value and refer to it later. These variables |
| exist entirely within @value{GDBN}; they are not part of your program, and |
| setting a convenience variable has no direct effect on further execution |
| of your program. That is why you can use them freely. |
| |
| Convenience variables are prefixed with @samp{$}. Any name preceded by |
| @samp{$} can be used for a convenience variable, unless it is one of |
| the predefined machine-specific register names (@pxref{Registers, ,Registers}). |
| (Value history references, in contrast, are @emph{numbers} preceded |
| by @samp{$}. @xref{Value History, ,Value History}.) |
| |
| You can save a value in a convenience variable with an assignment |
| expression, just as you would set a variable in your program. |
| For example: |
| |
| @smallexample |
| set $foo = *object_ptr |
| @end smallexample |
| |
| @noindent |
| would save in @code{$foo} the value contained in the object pointed to by |
| @code{object_ptr}. |
| |
| Using a convenience variable for the first time creates it, but its |
| value is @code{void} until you assign a new value. You can alter the |
| value with another assignment at any time. |
| |
| Convenience variables have no fixed types. You can assign a convenience |
| variable any type of value, including structures and arrays, even if |
| that variable already has a value of a different type. The convenience |
| variable, when used as an expression, has the type of its current value. |
| |
| @table @code |
| @kindex show convenience |
| @cindex show all user variables |
| @item show convenience |
| Print a list of convenience variables used so far, and their values. |
| Abbreviated @code{show conv}. |
| |
| @kindex init-if-undefined |
| @cindex convenience variables, initializing |
| @item init-if-undefined $@var{variable} = @var{expression} |
| Set a convenience variable if it has not already been set. This is useful |
| for user-defined commands that keep some state. It is similar, in concept, |
| to using local static variables with initializers in C (except that |
| convenience variables are global). It can also be used to allow users to |
| override default values used in a command script. |
| |
| If the variable is already defined then the expression is not evaluated so |
| any side-effects do not occur. |
| @end table |
| |
| One of the ways to use a convenience variable is as a counter to be |
| incremented or a pointer to be advanced. For example, to print |
| a field from successive elements of an array of structures: |
| |
| @smallexample |
| set $i = 0 |
| print bar[$i++]->contents |
| @end smallexample |
| |
| @noindent |
| Repeat that command by typing @key{RET}. |
| |
| Some convenience variables are created automatically by @value{GDBN} and given |
| values likely to be useful. |
| |
| @table @code |
| @vindex $_@r{, convenience variable} |
| @item $_ |
| The variable @code{$_} is automatically set by the @code{x} command to |
| the last address examined (@pxref{Memory, ,Examining Memory}). Other |
| commands which provide a default address for @code{x} to examine also |
| set @code{$_} to that address; these commands include @code{info line} |
| and @code{info breakpoint}. The type of @code{$_} is @code{void *} |
| except when set by the @code{x} command, in which case it is a pointer |
| to the type of @code{$__}. |
| |
| @vindex $__@r{, convenience variable} |
| @item $__ |
| The variable @code{$__} is automatically set by the @code{x} command |
| to the value found in the last address examined. Its type is chosen |
| to match the format in which the data was printed. |
| |
| @item $_exitcode |
| @vindex $_exitcode@r{, convenience variable} |
| The variable @code{$_exitcode} is automatically set to the exit code when |
| the program being debugged terminates. |
| |
| @item $_probe_argc |
| @itemx $_probe_arg0@dots{}$_probe_arg11 |
| Arguments to a static probe. @xref{Static Probe Points}. |
| |
| @item $_sdata |
| @vindex $_sdata@r{, inspect, convenience variable} |
| The variable @code{$_sdata} contains extra collected static tracepoint |
| data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that |
| @code{$_sdata} could be empty, if not inspecting a trace buffer, or |
| if extra static tracepoint data has not been collected. |
| |
| @item $_siginfo |
| @vindex $_siginfo@r{, convenience variable} |
| The variable @code{$_siginfo} contains extra signal information |
| (@pxref{extra signal information}). Note that @code{$_siginfo} |
| could be empty, if the application has not yet received any signals. |
| For example, it will be empty before you execute the @code{run} command. |
| |
| @item $_tlb |
| @vindex $_tlb@r{, convenience variable} |
| The variable @code{$_tlb} is automatically set when debugging |
| applications running on MS-Windows in native mode or connected to |
| gdbserver that supports the @code{qGetTIBAddr} request. |
| @xref{General Query Packets}. |
| This variable contains the address of the thread information block. |
| |
| @end table |
| |
| On HP-UX systems, if you refer to a function or variable name that |
| begins with a dollar sign, @value{GDBN} searches for a user or system |
| name first, before it searches for a convenience variable. |
| |
| @cindex convenience functions |
| @value{GDBN} also supplies some @dfn{convenience functions}. These |
| have a syntax similar to convenience variables. A convenience |
| function can be used in an expression just like an ordinary function; |
| however, a convenience function is implemented internally to |
| @value{GDBN}. |
| |
| @table @code |
| @item help function |
| @kindex help function |
| @cindex show all convenience functions |
| Print a list of all convenience functions. |
| @end table |
| |
| @node Registers |
| @section Registers |
| |
| @cindex registers |
| You can refer to machine register contents, in expressions, as variables |
| with names starting with @samp{$}. The names of registers are different |
| for each machine; use @code{info registers} to see the names used on |
| your machine. |
| |
| @table @code |
| @kindex info registers |
| @item info registers |
| Print the names and values of all registers except floating-point |
| and vector registers (in the selected stack frame). |
| |
| @kindex info all-registers |
| @cindex floating point registers |
| @item info all-registers |
| Print the names and values of all registers, including floating-point |
| and vector registers (in the selected stack frame). |
| |
| @item info registers @var{regname} @dots{} |
| Print the @dfn{relativized} value of each specified register @var{regname}. |
| As discussed in detail below, register values are normally relative to |
| the selected stack frame. @var{regname} may be any register name valid on |
| the machine you are using, with or without the initial @samp{$}. |
| @end table |
| |
| @cindex stack pointer register |
| @cindex program counter register |
| @cindex process status register |
| @cindex frame pointer register |
| @cindex standard registers |
| @value{GDBN} has four ``standard'' register names that are available (in |
| expressions) on most machines---whenever they do not conflict with an |
| architecture's canonical mnemonics for registers. The register names |
| @code{$pc} and @code{$sp} are used for the program counter register and |
| the stack pointer. @code{$fp} is used for a register that contains a |
| pointer to the current stack frame, and @code{$ps} is used for a |
| register that contains the processor status. For example, |
| you could print the program counter in hex with |
| |
| @smallexample |
| p/x $pc |
| @end smallexample |
| |
| @noindent |
| or print the instruction to be executed next with |
| |
| @smallexample |
| x/i $pc |
| @end smallexample |
| |
| @noindent |
| or add four to the stack pointer@footnote{This is a way of removing |
| one word from the stack, on machines where stacks grow downward in |
| memory (most machines, nowadays). This assumes that the innermost |
| stack frame is selected; setting @code{$sp} is not allowed when other |
| stack frames are selected. To pop entire frames off the stack, |
| regardless of machine architecture, use @code{return}; |
| see @ref{Returning, ,Returning from a Function}.} with |
| |
| @smallexample |
| set $sp += 4 |
| @end smallexample |
| |
| Whenever possible, these four standard register names are available on |
| your machine even though the machine has different canonical mnemonics, |
| so long as there is no conflict. The @code{info registers} command |
| shows the canonical names. For example, on the SPARC, @code{info |
| registers} displays the processor status register as @code{$psr} but you |
| can also refer to it as @code{$ps}; and on x86-based machines @code{$ps} |
| is an alias for the @sc{eflags} register. |
| |
| @value{GDBN} always considers the contents of an ordinary register as an |
| integer when the register is examined in this way. Some machines have |
| special registers which can hold nothing but floating point; these |
| registers are considered to have floating point values. There is no way |
| to refer to the contents of an ordinary register as floating point value |
| (although you can @emph{print} it as a floating point value with |
| @samp{print/f $@var{regname}}). |
| |
| Some registers have distinct ``raw'' and ``virtual'' data formats. This |
| means that the data format in which the register contents are saved by |
| the operating system is not the same one that your program normally |
| sees. For example, the registers of the 68881 floating point |
| coprocessor are always saved in ``extended'' (raw) format, but all C |
| programs expect to work with ``double'' (virtual) format. In such |
| cases, @value{GDBN} normally works with the virtual format only (the format |
| that makes sense for your program), but the @code{info registers} command |
| prints the data in both formats. |
| |
| @cindex SSE registers (x86) |
| @cindex MMX registers (x86) |
| Some machines have special registers whose contents can be interpreted |
| in several different ways. For example, modern x86-based machines |
| have SSE and MMX registers that can hold several values packed |
| together in several different formats. @value{GDBN} refers to such |
| registers in @code{struct} notation: |
| |
| @smallexample |
| (@value{GDBP}) print $xmm1 |
| $1 = @{ |
| v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@}, |
| v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@}, |
| v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000", |
| v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@}, |
| v4_int32 = @{0, 20657912, 11, 13@}, |
| v2_int64 = @{88725056443645952, 55834574859@}, |
| uint128 = 0x0000000d0000000b013b36f800000000 |
| @} |
| @end smallexample |
| |
| @noindent |
| To set values of such registers, you need to tell @value{GDBN} which |
| view of the register you wish to change, as if you were assigning |
| value to a @code{struct} member: |
| |
| @smallexample |
| (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF |
| @end smallexample |
| |
| Normally, register values are relative to the selected stack frame |
| (@pxref{Selection, ,Selecting a Frame}). This means that you get the |
| value that the register would contain if all stack frames farther in |
| were exited and their saved registers restored. In order to see the |
| true contents of hardware registers, you must select the innermost |
| frame (with @samp{frame 0}). |
| |
| However, @value{GDBN} must deduce where registers are saved, from the machine |
| code generated by your compiler. If some registers are not saved, or if |
| @value{GDBN} is unable to locate the saved registers, the selected stack |
| frame makes no difference. |
| |
| @node Floating Point Hardware |
| @section Floating Point Hardware |
| @cindex floating point |
| |
| Depending on the configuration, @value{GDBN} may be able to give |
| you more information about the status of the floating point hardware. |
| |
| @table @code |
| @kindex info float |
| @item info float |
| Display hardware-dependent information about the floating |
| point unit. The exact contents and layout vary depending on the |
| floating point chip. Currently, @samp{info float} is supported on |
| the ARM and x86 machines. |
| @end table |
| |
| @node Vector Unit |
| @section Vector Unit |
| @cindex vector unit |
| |
| Depending on the configuration, @value{GDBN} may be able to give you |
| more information about the status of the vector unit. |
| |
| @table @code |
| @kindex info vector |
| @item info vector |
| Display information about the vector unit. The exact contents and |
| layout vary depending on the hardware. |
| @end table |
| |
| @node OS Information |
| @section Operating System Auxiliary Information |
| @cindex OS information |
| |
| @value{GDBN} provides interfaces to useful OS facilities that can help |
| you debug your program. |
| |
| @cindex @code{ptrace} system call |
| @cindex @code{struct user} contents |
| When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix |
| machines), it interfaces with the inferior via the @code{ptrace} |
| system call. The operating system creates a special sata structure, |
| called @code{struct user}, for this interface. You can use the |
| command @code{info udot} to display the contents of this data |
| structure. |
| |
| @table @code |
| @item info udot |
| @kindex info udot |
| Display the contents of the @code{struct user} maintained by the OS |
| kernel for the program being debugged. @value{GDBN} displays the |
| contents of @code{struct user} as a list of hex numbers, similar to |
| the @code{examine} command. |
| @end table |
| |
| @cindex auxiliary vector |
| @cindex vector, auxiliary |
| Some operating systems supply an @dfn{auxiliary vector} to programs at |
| startup. This is akin to the arguments and environment that you |
| specify for a program, but contains a system-dependent variety of |
| binary values that tell system libraries important details about the |
| hardware, operating system, and process. Each value's purpose is |
| identified by an integer tag; the meanings are well-known but system-specific. |
| Depending on the configuration and operating system facilities, |
| @value{GDBN} may be able to show you this information. For remote |
| targets, this functionality may further depend on the remote stub's |
| support of the @samp{qXfer:auxv:read} packet, see |
| @ref{qXfer auxiliary vector read}. |
| |
| @table @code |
| @kindex info auxv |
| @item info auxv |
| Display the auxiliary vector of the inferior, which can be either a |
| live process or a core dump file. @value{GDBN} prints each tag value |
| numerically, and also shows names and text descriptions for recognized |
| tags. Some values in the vector are numbers, some bit masks, and some |
| pointers to strings or other data. @value{GDBN} displays each value in the |
| most appropriate form for a recognized tag, and in hexadecimal for |
| an unrecognized tag. |
| @end table |
| |
| On some targets, @value{GDBN} can access operating system-specific |
| information and show it to you. The types of information available |
| will differ depending on the type of operating system running on the |
| target. The mechanism used to fetch the data is described in |
| @ref{Operating System Information}. For remote targets, this |
| functionality depends on the remote stub's support of the |
| @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}. |
| |
| @table @code |
| @kindex info os |
| @item info os @var{infotype} |
| |
| Display OS information of the requested type. |
| |
| On @sc{gnu}/Linux, the following values of @var{infotype} are valid: |
| |
| @anchor{linux info os infotypes} |
| @table @code |
| @kindex info os processes |
| @item processes |
| Display the list of processes on the target. For each process, |
| @value{GDBN} prints the process identifier, the name of the user, the |
| command corresponding to the process, and the list of processor cores |
| that the process is currently running on. (To understand what these |
| properties mean, for this and the following info types, please consult |
| the general @sc{gnu}/Linux documentation.) |
| |
| @kindex info os procgroups |
| @item procgroups |
| Display the list of process groups on the target. For each process, |
| @value{GDBN} prints the identifier of the process group that it belongs |
| to, the command corresponding to the process group leader, the process |
| identifier, and the command line of the process. The list is sorted |
| first by the process group identifier, then by the process identifier, |
| so that processes belonging to the same process group are grouped together |
| and the process group leader is listed first. |
| |
| @kindex info os threads |
| @item threads |
| Display the list of threads running on the target. For each thread, |
| @value{GDBN} prints the identifier of the process that the thread |
| belongs to, the command of the process, the thread identifier, and the |
| processor core that it is currently running on. The main thread of a |
| process is not listed. |
| |
| @kindex info os files |
| @item files |
| Display the list of open file descriptors on the target. For each |
| file descriptor, @value{GDBN} prints the identifier of the process |
| owning the descriptor, the command of the owning process, the value |
| of the descriptor, and the target of the descriptor. |
| |
| @kindex info os sockets |
| @item sockets |
| Display the list of Internet-domain sockets on the target. For each |
| socket, @value{GDBN} prints the address and port of the local and |
| remote endpoints, the current state of the connection, the creator of |
| the socket, the IP address family of the socket, and the type of the |
| connection. |
| |
| @kindex info os shm |
| @item shm |
| Display the list of all System V shared-memory regions on the target. |
| For each shared-memory region, @value{GDBN} prints the region key, |
| the shared-memory identifier, the access permissions, the size of the |
| region, the process that created the region, the process that last |
| attached to or detached from the region, the current number of live |
| attaches to the region, and the times at which the region was last |
| attached to, detach from, and changed. |
| |
| @kindex info os semaphores |
| @item semaphores |
| Display the list of all System V semaphore sets on the target. For each |
| semaphore set, @value{GDBN} prints the semaphore set key, the semaphore |
| set identifier, the access permissions, the number of semaphores in the |
| set, the user and group of the owner and creator of the semaphore set, |
| and the times at which the semaphore set was operated upon and changed. |
| |
| @kindex info os msg |
| @item msg |
| Display the list of all System V message queues on the target. For each |
| message queue, @value{GDBN} prints the message queue key, the message |
| queue identifier, the access permissions, the current number of bytes |
| on the queue, the current number of messages on the queue, the processes |
| that last sent and received a message on the queue, the user and group |
| of the owner and creator of the message queue, the times at which a |
| message was last sent and received on the queue, and the time at which |
| the message queue was last changed. |
| |
| @kindex info os modules |
| @item modules |
| Display the list of all loaded kernel modules on the target. For each |
| module, @value{GDBN} prints the module name, the size of the module in |
| bytes, the number of times the module is used, the dependencies of the |
| module, the status of the module, and the address of the loaded module |
| in memory. |
| @end table |
| |
| @item info os |
| If @var{infotype} is omitted, then list the possible values for |
| @var{infotype} and the kind of OS information available for each |
| @var{infotype}. If the target does not return a list of possible |
| types, this command will report an error. |
| @end table |
| |
| @node Memory Region Attributes |
| @section Memory Region Attributes |
| @cindex memory region attributes |
| |
| @dfn{Memory region attributes} allow you to describe special handling |
| required by regions of your target's memory. @value{GDBN} uses |
| attributes to determine whether to allow certain types of memory |
| accesses; whether to use specific width accesses; and whether to cache |
| target memory. By default the description of memory regions is |
| fetched from the target (if the current target supports this), but the |
| user can override the fetched regions. |
| |
| Defined memory regions can be individually enabled and disabled. When a |
| memory region is disabled, @value{GDBN} uses the default attributes when |
| accessing memory in that region. Similarly, if no memory regions have |
| been defined, @value{GDBN} uses the default attributes when accessing |
| all memory. |
| |
| When a memory region is defined, it is given a number to identify it; |
| to enable, disable, or remove a memory region, you specify that number. |
| |
| @table @code |
| @kindex mem |
| @item mem @var{lower} @var{upper} @var{attributes}@dots{} |
| Define a memory region bounded by @var{lower} and @var{upper} with |
| attributes @var{attributes}@dots{}, and add it to the list of regions |
| monitored by @value{GDBN}. Note that @var{upper} == 0 is a special |
| case: it is treated as the target's maximum memory address. |
| (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.) |
| |
| @item mem auto |
| Discard any user changes to the memory regions and use target-supplied |
| regions, if available, or no regions if the target does not support. |
| |
| @kindex delete mem |
| @item delete mem @var{nums}@dots{} |
| Remove memory regions @var{nums}@dots{} from the list of regions |
| monitored by @value{GDBN}. |
| |
| @kindex disable mem |
| @item disable mem @var{nums}@dots{} |
| Disable monitoring of memory regions @var{nums}@dots{}. |
| A disabled memory region is not forgotten. |
| It may be enabled again later. |
| |
| @kindex enable mem |
| @item enable mem @var{nums}@dots{} |
| Enable monitoring of memory regions @var{nums}@dots{}. |
| |
| @kindex info mem |
| @item info mem |
| Print a table of all defined memory regions, with the following columns |
| for each region: |
| |
| @table @emph |
| @item Memory Region Number |
| @item Enabled or Disabled. |
| Enabled memory regions are marked with @samp{y}. |
| Disabled memory regions are marked with @samp{n}. |
| |
| @item Lo Address |
| The address defining the inclusive lower bound of the memory region. |
| |
| @item Hi Address |
| The address defining the exclusive upper bound of the memory region. |
| |
| @item Attributes |
| The list of attributes set for this memory region. |
| @end table |
| @end table |
| |
| |
| @subsection Attributes |
| |
| @subsubsection Memory Access Mode |
| The access mode attributes set whether @value{GDBN} may make read or |
| write accesses to a memory region. |
| |
| While these attributes prevent @value{GDBN} from performing invalid |
| memory accesses, they do nothing to prevent the target system, I/O DMA, |
| etc.@: from accessing memory. |
| |
| @table @code |
| @item ro |
| Memory is read only. |
| @item wo |
| Memory is write only. |
| @item rw |
| Memory is read/write. This is the default. |
| @end table |
| |
| @subsubsection Memory Access Size |
| The access size attribute tells @value{GDBN} to use specific sized |
| accesses in the memory region. Often memory mapped device registers |
| require specific sized accesses. If no access size attribute is |
| specified, @value{GDBN} may use accesses of any size. |
| |
| @table @code |
| @item 8 |
| Use 8 bit memory accesses. |
| @item 16 |
| Use 16 bit memory accesses. |
| @item 32 |
| Use 32 bit memory accesses. |
| @item 64 |
| Use 64 bit memory accesses. |
| @end table |
| |
| @c @subsubsection Hardware/Software Breakpoints |
| @c The hardware/software breakpoint attributes set whether @value{GDBN} |
| @c will use hardware or software breakpoints for the internal breakpoints |
| @c used by the step, next, finish, until, etc. commands. |
| @c |
| @c @table @code |
| @c @item hwbreak |
| @c Always use hardware breakpoints |
| @c @item swbreak (default) |
| @c @end table |
| |
| @subsubsection Data Cache |
| The data cache attributes set whether @value{GDBN} will cache target |
| memory. While this generally improves performance by reducing debug |
| protocol overhead, it can lead to incorrect results because @value{GDBN} |
| does not know about volatile variables or memory mapped device |
| registers. |
| |
| @table @code |
| @item cache |
| Enable @value{GDBN} to cache target memory. |
| @item nocache |
| Disable @value{GDBN} from caching target memory. This is the default. |
| @end table |
| |
| @subsection Memory Access Checking |
| @value{GDBN} can be instructed to refuse accesses to memory that is |
| not explicitly described. This can be useful if accessing such |
| regions has undesired effects for a specific target, or to provide |
| better error checking. The following commands control this behaviour. |
| |
| @table @code |
| @kindex set mem inaccessible-by-default |
| @item set mem inaccessible-by-default [on|off] |
| If @code{on} is specified, make @value{GDBN} treat memory not |
| explicitly described by the memory ranges as non-existent and refuse accesses |
| to such memory. The checks are only performed if there's at least one |
| memory range defined. If @code{off} is specified, make @value{GDBN} |
| treat the memory not explicitly described by the memory ranges as RAM. |
| The default value is @code{on}. |
| @kindex show mem inaccessible-by-default |
| @item show mem inaccessible-by-default |
| Show the current handling of accesses to unknown memory. |
| @end table |
| |
| |
| @c @subsubsection Memory Write Verification |
| @c The memory write verification attributes set whether @value{GDBN} |
| @c will re-reads data after each write to verify the write was successful. |
| @c |
| @c @table @code |
| @c @item verify |
| @c @item noverify (default) |
| @c @end table |
| |
| @node Dump/Restore Files |
| @section Copy Between Memory and a File |
| @cindex dump/restore files |
| @cindex append data to a file |
| @cindex dump data to a file |
| @cindex restore data from a file |
| |
| You can use the commands @code{dump}, @code{append}, and |
| @code{restore} to copy data between target memory and a file. The |
| @code{dump} and @code{append} commands write data to a file, and the |
| @code{restore} command reads data from a file back into the inferior's |
| memory. Files may be in binary, Motorola S-record, Intel hex, or |
| Tektronix Hex format; however, @value{GDBN} can only append to binary |
| files. |
| |
| @table @code |
| |
| @kindex dump |
| @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr} |
| @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr} |
| Dump the contents of memory from @var{start_addr} to @var{end_addr}, |
| or the value of @var{expr}, to @var{filename} in the given format. |
| |
| The @var{format} parameter may be any one of: |
| @table @code |
| @item binary |
| Raw binary form. |
| @item ihex |
| Intel hex format. |
| @item srec |
| Motorola S-record format. |
| @item tekhex |
| Tektronix Hex format. |
| @end table |
| |
| @value{GDBN} uses the same definitions of these formats as the |
| @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If |
| @var{format} is omitted, @value{GDBN} dumps the data in raw binary |
| form. |
| |
| @kindex append |
| @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr} |
| @itemx append @r{[}binary@r{]} value @var{filename} @var{expr} |
| Append the contents of memory from @var{start_addr} to @var{end_addr}, |
| or the value of @var{expr}, to the file @var{filename}, in raw binary form. |
| (@value{GDBN} can only append data to files in raw binary form.) |
| |
| @kindex restore |
| @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end} |
| Restore the contents of file @var{filename} into memory. The |
| @code{restore} command can automatically recognize any known @sc{bfd} |
| file format, except for raw binary. To restore a raw binary file you |
| must specify the optional keyword @code{binary} after the filename. |
| |
| If @var{bias} is non-zero, its value will be added to the addresses |
| contained in the file. Binary files always start at address zero, so |
| they will be restored at address @var{bias}. Other bfd files have |
| a built-in location; they will be restored at offset @var{bias} |
| from that location. |
| |
| If @var{start} and/or @var{end} are non-zero, then only data between |
| file offset @var{start} and file offset @var{end} will be restored. |
| These offsets are relative to the addresses in the file, before |
| the @var{bias} argument is applied. |
| |
| @end table |
| |
| @node Core File Generation |
| @section How to Produce a Core File from Your Program |
| @cindex dump core from inferior |
| |
| A @dfn{core file} or @dfn{core dump} is a file that records the memory |
| image of a running process and its process status (register values |
| etc.). Its primary use is post-mortem debugging of a program that |
| crashed while it ran outside a debugger. A program that crashes |
| automatically produces a core file, unless this feature is disabled by |
| the user. @xref{Files}, for information on invoking @value{GDBN} in |
| the post-mortem debugging mode. |
| |
| Occasionally, you may wish to produce a core file of the program you |
| are debugging in order to preserve a snapshot of its state. |
| @value{GDBN} has a special command for that. |
| |
| @table @code |
| @kindex gcore |
| @kindex generate-core-file |
| @item generate-core-file [@var{file}] |
| @itemx gcore [@var{file}] |
| Produce a core dump of the inferior process. The optional argument |
| @var{file} specifies the file name where to put the core dump. If not |
| specified, the file name defaults to @file{core.@var{pid}}, where |
| @var{pid} is the inferior process ID. |
| |
| Note that this command is implemented only for some systems (as of |
| this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390). |
| @end table |
| |
| @node Character Sets |
| @section Character Sets |
| @cindex character sets |
| @cindex charset |
| @cindex translating between character sets |
| @cindex host character set |
| @cindex target character set |
| |
| If the program you are debugging uses a different character set to |
| represent characters and strings than the one @value{GDBN} uses itself, |
| @value{GDBN} can automatically translate between the character sets for |
| you. The character set @value{GDBN} uses we call the @dfn{host |
| character set}; the one the inferior program uses we call the |
| @dfn{target character set}. |
| |
| For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which |
| uses the ISO Latin 1 character set, but you are using @value{GDBN}'s |
| remote protocol (@pxref{Remote Debugging}) to debug a program |
| running on an IBM mainframe, which uses the @sc{ebcdic} character set, |
| then the host character set is Latin-1, and the target character set is |
| @sc{ebcdic}. If you give @value{GDBN} the command @code{set |
| target-charset EBCDIC-US}, then @value{GDBN} translates between |
| @sc{ebcdic} and Latin 1 as you print character or string values, or use |
| character and string literals in expressions. |
| |
| @value{GDBN} has no way to automatically recognize which character set |
| the inferior program uses; you must tell it, using the @code{set |
| target-charset} command, described below. |
| |
| Here are the commands for controlling @value{GDBN}'s character set |
| support: |
| |
| @table @code |
| @item set target-charset @var{charset} |
| @kindex set target-charset |
| Set the current target character set to @var{charset}. To display the |
| list of supported target character sets, type |
| @kbd{@w{set target-charset @key{TAB}@key{TAB}}}. |
| |
| @item set host-charset @var{charset} |
| @kindex set host-charset |
| Set the current host character set to @var{charset}. |
| |
| By default, @value{GDBN} uses a host character set appropriate to the |
| system it is running on; you can override that default using the |
| @code{set host-charset} command. On some systems, @value{GDBN} cannot |
| automatically determine the appropriate host character set. In this |
| case, @value{GDBN} uses @samp{UTF-8}. |
| |
| @value{GDBN} can only use certain character sets as its host character |
| set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}}, |
| @value{GDBN} will list the host character sets it supports. |
| |
| @item set charset @var{charset} |
| @kindex set charset |
| Set the current host and target character sets to @var{charset}. As |
| above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}}, |
| @value{GDBN} will list the names of the character sets that can be used |
| for both host and target. |
| |
| @item show charset |
| @kindex show charset |
| Show the names of the current host and target character sets. |
| |
| @item show host-charset |
| @kindex show host-charset |
| Show the name of the current host character set. |
| |
| @item show target-charset |
| @kindex show target-charset |
| Show the name of the current target character set. |
| |
| @item set target-wide-charset @var{charset} |
| @kindex set target-wide-charset |
| Set the current target's wide character set to @var{charset}. This is |
| the character set used by the target's @code{wchar_t} type. To |
| display the list of supported wide character sets, type |
| @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}. |
| |
| @item show target-wide-charset |
| @kindex show target-wide-charset |
| Show the name of the current target's wide character set. |
| @end table |
| |
| Here is an example of @value{GDBN}'s character set support in action. |
| Assume that the following source code has been placed in the file |
| @file{charset-test.c}: |
| |
| @smallexample |
| #include <stdio.h> |
| |
| char ascii_hello[] |
| = @{72, 101, 108, 108, 111, 44, 32, 119, |
| 111, 114, 108, 100, 33, 10, 0@}; |
| char ibm1047_hello[] |
| = @{200, 133, 147, 147, 150, 107, 64, 166, |
| 150, 153, 147, 132, 90, 37, 0@}; |
| |
| main () |
| @{ |
| printf ("Hello, world!\n"); |
| @} |
| @end smallexample |
| |
| In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays |
| containing the string @samp{Hello, world!} followed by a newline, |
| encoded in the @sc{ascii} and @sc{ibm1047} character sets. |
| |
| We compile the program, and invoke the debugger on it: |
| |
| @smallexample |
| $ gcc -g charset-test.c -o charset-test |
| $ gdb -nw charset-test |
| GNU gdb 2001-12-19-cvs |
| Copyright 2001 Free Software Foundation, Inc. |
| @dots{} |
| (@value{GDBP}) |
| @end smallexample |
| |
| We can use the @code{show charset} command to see what character sets |
| @value{GDBN} is currently using to interpret and display characters and |
| strings: |
| |
| @smallexample |
| (@value{GDBP}) show charset |
| The current host and target character set is `ISO-8859-1'. |
| (@value{GDBP}) |
| @end smallexample |
| |
| For the sake of printing this manual, let's use @sc{ascii} as our |
| initial character set: |
| @smallexample |
| (@value{GDBP}) set charset ASCII |
| (@value{GDBP}) show charset |
| The current host and target character set is `ASCII'. |
| (@value{GDBP}) |
| @end smallexample |
| |
| Let's assume that @sc{ascii} is indeed the correct character set for our |
| host system --- in other words, let's assume that if @value{GDBN} prints |
| characters using the @sc{ascii} character set, our terminal will display |
| them properly. Since our current target character set is also |
| @sc{ascii}, the contents of @code{ascii_hello} print legibly: |
| |
| @smallexample |
| (@value{GDBP}) print ascii_hello |
| $1 = 0x401698 "Hello, world!\n" |
| (@value{GDBP}) print ascii_hello[0] |
| $2 = 72 'H' |
| (@value{GDBP}) |
| @end smallexample |
| |
| @value{GDBN} uses the target character set for character and string |
| literals you use in expressions: |
| |
| @smallexample |
| (@value{GDBP}) print '+' |
| $3 = 43 '+' |
| (@value{GDBP}) |
| @end smallexample |
| |
| The @sc{ascii} character set uses the number 43 to encode the @samp{+} |
| character. |
| |
| @value{GDBN} relies on the user to tell it which character set the |
| target program uses. If we print @code{ibm1047_hello} while our target |
| character set is still @sc{ascii}, we get jibberish: |
| |
| @smallexample |
| (@value{GDBP}) print ibm1047_hello |
| $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%" |
| (@value{GDBP}) print ibm1047_hello[0] |
| $5 = 200 '\310' |
| (@value{GDBP}) |
| @end smallexample |
| |
| If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB}, |
| @value{GDBN} tells us the character sets it supports: |
| |
| @smallexample |
| (@value{GDBP}) set target-charset |
| ASCII EBCDIC-US IBM1047 ISO-8859-1 |
| (@value{GDBP}) set target-charset |
| @end smallexample |
| |
| We can select @sc{ibm1047} as our target character set, and examine the |
| program's strings again. Now the @sc{ascii} string is wrong, but |
| @value{GDBN} translates the contents of @code{ibm1047_hello} from the |
| target character set, @sc{ibm1047}, to the host character set, |
| @sc{ascii}, and they display correctly: |
| |
| @smallexample |
| (@value{GDBP}) set target-charset IBM1047 |
| (@value{GDBP}) show charset |
| The current host character set is `ASCII'. |
| The current target character set is `IBM1047'. |
| (@value{GDBP}) print ascii_hello |
| $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012" |
| (@value{GDBP}) print ascii_hello[0] |
| $7 = 72 '\110' |
| (@value{GDBP}) print ibm1047_hello |
| $8 = 0x4016a8 "Hello, world!\n" |
| (@value{GDBP}) print ibm1047_hello[0] |
| $9 = 200 'H' |
| (@value{GDBP}) |
| @end smallexample |
| |
| As above, @value{GDBN} uses the target character set for character and |
| string literals you use in expressions: |
| |
| @smallexample |
| (@value{GDBP}) print '+' |
| $10 = 78 '+' |
| (@value{GDBP}) |
| @end smallexample |
| |
| The @sc{ibm1047} character set uses the number 78 to encode the @samp{+} |
| character. |
| |
| @node Caching Remote Data |
| @section Caching Data of Remote Targets |
| @cindex caching data of remote targets |
| |
| @value{GDBN} caches data exchanged between the debugger and a |
| remote target (@pxref{Remote Debugging}). Such caching generally improves |
| performance, because it reduces the overhead of the remote protocol by |
| bundling memory reads and writes into large chunks. Unfortunately, simply |
| caching everything would lead to incorrect results, since @value{GDBN} |
| does not necessarily know anything about volatile values, memory-mapped I/O |
| addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode}) |
| memory can be changed @emph{while} a gdb command is executing. |
| Therefore, by default, @value{GDBN} only caches data |
| known to be on the stack@footnote{In non-stop mode, it is moderately |
| rare for a running thread to modify the stack of a stopped thread |
| in a way that would interfere with a backtrace, and caching of |
| stack reads provides a significant speed up of remote backtraces.}. |
| Other regions of memory can be explicitly marked as |
| cacheable; see @pxref{Memory Region Attributes}. |
| |
| @table @code |
| @kindex set remotecache |
| @item set remotecache on |
| @itemx set remotecache off |
| This option no longer does anything; it exists for compatibility |
| with old scripts. |
| |
| @kindex show remotecache |
| @item show remotecache |
| Show the current state of the obsolete remotecache flag. |
| |
| @kindex set stack-cache |
| @item set stack-cache on |
| @itemx set stack-cache off |
| Enable or disable caching of stack accesses. When @code{ON}, use |
| caching. By default, this option is @code{ON}. |
| |
| @kindex show stack-cache |
| @item show stack-cache |
| Show the current state of data caching for memory accesses. |
| |
| @kindex info dcache |
| @item info dcache @r{[}line@r{]} |
| Print the information about the data cache performance. The |
| information displayed includes the dcache width and depth, and for |
| each cache line, its number, address, and how many times it was |
| referenced. This command is useful for debugging the data cache |
| operation. |
| |
| If a line number is specified, the contents of that line will be |
| printed in hex. |
| |
| @item set dcache size @var{size} |
| @cindex dcache size |
| @kindex set dcache size |
| Set maximum number of entries in dcache (dcache depth above). |
| |
| @item set dcache line-size @var{line-size} |
| @cindex dcache line-size |
| @kindex set dcache line-size |
| Set number of bytes each dcache entry caches (dcache width above). |
| Must be a power of 2. |
| |
| @item show dcache size |
| @kindex show dcache size |
| Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}. |
| |
| @item show dcache line-size |
| @kindex show dcache line-size |
| Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}. |
| |
| @end table |
| |
| @node Searching Memory |
| @section Search Memory |
| @cindex searching memory |
| |
| Memory can be searched for a particular sequence of bytes with the |
| @code{find} command. |
| |
| @table @code |
| @kindex find |
| @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]} |
| @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]} |
| Search memory for the sequence of bytes specified by @var{val1}, @var{val2}, |
| etc. The search begins at address @var{start_addr} and continues for either |
| @var{len} bytes or through to @var{end_addr} inclusive. |
| @end table |
| |
| @var{s} and @var{n} are optional parameters. |
| They may be specified in either order, apart or together. |
| |
| @table @r |
| @item @var{s}, search query size |
| The size of each search query value. |
| |
| @table @code |
| @item b |
| bytes |
| @item h |
| halfwords (two bytes) |
| @item w |
| words (four bytes) |
| @item g |
| giant words (eight bytes) |
| @end table |
| |
| All values are interpreted in the current language. |
| This means, for example, that if the current source language is C/C@t{++} |
| then searching for the string ``hello'' includes the trailing '\0'. |
| |
| If the value size is not specified, it is taken from the |
| value's type in the current language. |
| This is useful when one wants to specify the search |
| pattern as a mixture of types. |
| Note that this means, for example, that in the case of C-like languages |
| a search for an untyped 0x42 will search for @samp{(int) 0x42} |
| which is typically four bytes. |
| |
| @item @var{n}, maximum number of finds |
| The maximum number of matches to print. The default is to print all finds. |
| @end table |
| |
| You can use strings as search values. Quote them with double-quotes |
| (@code{"}). |
| The string value is copied into the search pattern byte by byte, |
| regardless of the endianness of the target and the size specification. |
| |
| The address of each match found is printed as well as a count of the |
| number of matches found. |
| |
| The address of the last value found is stored in convenience variable |
| @samp{$_}. |
| A count of the number of matches is stored in @samp{$numfound}. |
| |
| For example, if stopped at the @code{printf} in this function: |
| |
| @smallexample |
| void |
| hello () |
| @{ |
| static char hello[] = "hello-hello"; |
| static struct @{ char c; short s; int i; @} |
| __attribute__ ((packed)) mixed |
| = @{ 'c', 0x1234, 0x87654321 @}; |
| printf ("%s\n", hello); |
| @} |
| @end smallexample |
| |
| @noindent |
| you get during debugging: |
| |
| @smallexample |
| (gdb) find &hello[0], +sizeof(hello), "hello" |
| 0x804956d <hello.1620+6> |
| 1 pattern found |
| (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o' |
| 0x8049567 <hello.1620> |
| 0x804956d <hello.1620+6> |
| 2 patterns found |
| (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l' |
| 0x8049567 <hello.1620> |
| 1 pattern found |
| (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321 |
| 0x8049560 <mixed.1625> |
| 1 pattern found |
| (gdb) print $numfound |
| $1 = 1 |
| (gdb) print $_ |
| $2 = (void *) 0x8049560 |
| @end smallexample |
| |
| @node Optimized Code |
| @chapter Debugging Optimized Code |
| @cindex optimized code, debugging |
| @cindex debugging optimized code |
| |
| Almost all compilers support optimization. With optimization |
| disabled, the compiler generates assembly code that corresponds |
| directly to your source code, in a simplistic way. As the compiler |
| applies more powerful optimizations, the generated assembly code |
| diverges from your original source code. With help from debugging |
| information generated by the compiler, @value{GDBN} can map from |
| the running program back to constructs from your original source. |
| |
| @value{GDBN} is more accurate with optimization disabled. If you |
| can recompile without optimization, it is easier to follow the |
| progress of your program during debugging. But, there are many cases |
| where you may need to debug an optimized version. |
| |
| When you debug a program compiled with @samp{-g -O}, remember that the |
| optimizer has rearranged your code; the debugger shows you what is |
| really there. Do not be too surprised when the execution path does not |
| exactly match your source file! An extreme example: if you define a |
| variable, but never use it, @value{GDBN} never sees that |
| variable---because the compiler optimizes it out of existence. |
| |
| Some things do not work as well with @samp{-g -O} as with just |
| @samp{-g}, particularly on machines with instruction scheduling. If in |
| doubt, recompile with @samp{-g} alone, and if this fixes the problem, |
| please report it to us as a bug (including a test case!). |
| @xref{Variables}, for more information about debugging optimized code. |
| |
| @menu |
| * Inline Functions:: How @value{GDBN} presents inlining |
| * Tail Call Frames:: @value{GDBN} analysis of jumps to functions |
| @end menu |
| |
| @node Inline Functions |
| @section Inline Functions |
| @cindex inline functions, debugging |
| |
| @dfn{Inlining} is an optimization that inserts a copy of the function |
| body directly at each call site, instead of jumping to a shared |
| routine. @value{GDBN} displays inlined functions just like |
| non-inlined functions. They appear in backtraces. You can view their |
| arguments and local variables, step into them with @code{step}, skip |
| them with @code{next}, and escape from them with @code{finish}. |
| You can check whether a function was inlined by using the |
| @code{info frame} command. |
| |
| For @value{GDBN} to support inlined functions, the compiler must |
| record information about inlining in the debug information --- |
| @value{NGCC} using the @sc{dwarf 2} format does this, and several |
| other compilers do also. @value{GDBN} only supports inlined functions |
| when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1 |
| do not emit two required attributes (@samp{DW_AT_call_file} and |
| @samp{DW_AT_call_line}); @value{GDBN} does not display inlined |
| function calls with earlier versions of @value{NGCC}. It instead |
| displays the arguments and local variables of inlined functions as |
| local variables in the caller. |
| |
| The body of an inlined function is directly included at its call site; |
| unlike a non-inlined function, there are no instructions devoted to |
| the call. @value{GDBN} still pretends that the call site and the |
| start of the inlined function are different instructions. Stepping to |
| the call site shows the call site, and then stepping again shows |
| the first line of the inlined function, even though no additional |
| instructions are executed. |
| |
| This makes source-level debugging much clearer; you can see both the |
| context of the call and then the effect of the call. Only stepping by |
| a single instruction using @code{stepi} or @code{nexti} does not do |
| this; single instruction steps always show the inlined body. |
| |
| There are some ways that @value{GDBN} does not pretend that inlined |
| function calls are the same as normal calls: |
| |
| @itemize @bullet |
| @item |
| Setting breakpoints at the call site of an inlined function may not |
| work, because the call site does not contain any code. @value{GDBN} |
| may incorrectly move the breakpoint to the next line of the enclosing |
| function, after the call. This limitation will be removed in a future |
| version of @value{GDBN}; until then, set a breakpoint on an earlier line |
| or inside the inlined function instead. |
| |
| @item |
| @value{GDBN} cannot locate the return value of inlined calls after |
| using the @code{finish} command. This is a limitation of compiler-generated |
| debugging information; after @code{finish}, you can step to the next line |
| and print a variable where your program stored the return value. |
| |
| @end itemize |
| |
| @node Tail Call Frames |
| @section Tail Call Frames |
| @cindex tail call frames, debugging |
| |
| Function @code{B} can call function @code{C} in its very last statement. In |
| unoptimized compilation the call of @code{C} is immediately followed by return |
| instruction at the end of @code{B} code. Optimizing compiler may replace the |
| call and return in function @code{B} into one jump to function @code{C} |
| instead. Such use of a jump instruction is called @dfn{tail call}. |
| |
| During execution of function @code{C}, there will be no indication in the |
| function call stack frames that it was tail-called from @code{B}. If function |
| @code{A} regularly calls function @code{B} which tail-calls function @code{C}, |
| then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in |
| some cases @value{GDBN} can determine that @code{C} was tail-called from |
| @code{B}, and it will then create fictitious call frame for that, with the |
| return address set up as if @code{B} called @code{C} normally. |
| |
| This functionality is currently supported only by DWARF 2 debugging format and |
| the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With |
| @value{NGCC}, you need to specify @option{-O -g} during compilation, to get |
| this information. |
| |
| @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame |
| kind by text @code{tail call frame} such as in this sample @value{GDBN} output: |
| |
| @smallexample |
| (gdb) x/i $pc - 2 |
| 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)> |
| (gdb) info frame |
| Stack level 1, frame at 0x7fffffffda30: |
| rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5 |
| tail call frame, caller of frame at 0x7fffffffda30 |
| source language c++. |
| Arglist at unknown address. |
| Locals at unknown address, Previous frame's sp is 0x7fffffffda30 |
| @end smallexample |
| |
| The detection of all the possible code path executions can find them ambiguous. |
| There is no execution history stored (possible @ref{Reverse Execution} is never |
| used for this purpose) and the last known caller could have reached the known |
| callee by multiple different jump sequences. In such case @value{GDBN} still |
| tries to show at least all the unambiguous top tail callers and all the |
| unambiguous bottom tail calees, if any. |
| |
| @table @code |
| @anchor{set debug entry-values} |
| @item set debug entry-values |
| @kindex set debug entry-values |
| When set to on, enables printing of analysis messages for both frame argument |
| values at function entry and tail calls. It will show all the possible valid |
| tail calls code paths it has considered. It will also print the intersection |
| of them with the final unambiguous (possibly partial or even empty) code path |
| result. |
| |
| @item show debug entry-values |
| @kindex show debug entry-values |
| Show the current state of analysis messages printing for both frame argument |
| values at function entry and tail calls. |
| @end table |
| |
| The analysis messages for tail calls can for example show why the virtual tail |
| call frame for function @code{c} has not been recognized (due to the indirect |
| reference by variable @code{x}): |
| |
| @smallexample |
| static void __attribute__((noinline, noclone)) c (void); |
| void (*x) (void) = c; |
| static void __attribute__((noinline, noclone)) a (void) @{ x++; @} |
| static void __attribute__((noinline, noclone)) c (void) @{ a (); @} |
| int main (void) @{ x (); return 0; @} |
| |
| Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find |
| DW_TAG_GNU_call_site 0x40039a in main |
| a () at t.c:3 |
| 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @} |
| (gdb) bt |
| #0 a () at t.c:3 |
| #1 0x000000000040039a in main () at t.c:5 |
| @end smallexample |
| |
| Another possibility is an ambiguous virtual tail call frames resolution: |
| |
| @smallexample |
| int i; |
| static void __attribute__((noinline, noclone)) f (void) @{ i++; @} |
| static void __attribute__((noinline, noclone)) e (void) @{ f (); @} |
| static void __attribute__((noinline, noclone)) d (void) @{ f (); @} |
| static void __attribute__((noinline, noclone)) c (void) @{ d (); @} |
| static void __attribute__((noinline, noclone)) b (void) |
| @{ if (i) c (); else e (); @} |
| static void __attribute__((noinline, noclone)) a (void) @{ b (); @} |
| int main (void) @{ a (); return 0; @} |
| |
| tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d) |
| tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e) |
| tailcall: reduced: 0x4004d2(a) | |
| (gdb) bt |
| #0 f () at t.c:2 |
| #1 0x00000000004004d2 in a () at t.c:8 |
| #2 0x0000000000400395 in main () at t.c:9 |
| @end smallexample |
| |
| @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f} |
| @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f} |
| |
| @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK. |
| @ifset HAVE_MAKEINFO_CLICK |
| @set ARROW @click{} |
| @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}} |
| @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}} |
| @end ifset |
| @ifclear HAVE_MAKEINFO_CLICK |
| @set ARROW -> |
| @set CALLSEQ1B @value{CALLSEQ1A} |
| @set CALLSEQ2B @value{CALLSEQ2A} |
| @end ifclear |
| |
| Frames #0 and #2 are real, #1 is a virtual tail call frame. |
| The code can have possible execution paths @value{CALLSEQ1B} or |
| @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state. |
| |
| @code{initial:} state shows some random possible calling sequence @value{GDBN} |
| has found. It then finds another possible calling sequcen - that one is |
| prefixed by @code{compare:}. The non-ambiguous intersection of these two is |
| printed as the @code{reduced:} calling sequence. That one could have many |
| futher @code{compare:} and @code{reduced:} statements as long as there remain |
| any non-ambiguous sequence entries. |
| |
| For the frame of function @code{b} in both cases there are different possible |
| @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is |
| also ambigous. The only non-ambiguous frame is the one for function @code{a}, |
| therefore this one is displayed to the user while the ambiguous frames are |
| omitted. |
| |
| There can be also reasons why printing of frame argument values at function |
| entry may fail: |
| |
| @smallexample |
| int v; |
| static void __attribute__((noinline, noclone)) c (int i) @{ v++; @} |
| static void __attribute__((noinline, noclone)) a (int i); |
| static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @} |
| static void __attribute__((noinline, noclone)) a (int i) |
| @{ if (i) b (i - 1); else c (0); @} |
| int main (void) @{ a (5); return 0; @} |
| |
| (gdb) bt |
| #0 c (i=i@@entry=0) at t.c:2 |
| #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found |
| function "a" at 0x400420 can call itself via tail calls |
| i=<optimized out>) at t.c:6 |
| #2 0x000000000040036e in main () at t.c:7 |
| @end smallexample |
| |
| @value{GDBN} cannot find out from the inferior state if and how many times did |
| function @code{a} call itself (via function @code{b}) as these calls would be |
| tail calls. Such tail calls would modify thue @code{i} variable, therefore |
| @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN} |
| prints @code{<optimized out>} instead. |
| |
| @node Macros |
| @chapter C Preprocessor Macros |
| |
| Some languages, such as C and C@t{++}, provide a way to define and invoke |
| ``preprocessor macros'' which expand into strings of tokens. |
| @value{GDBN} can evaluate expressions containing macro invocations, show |
| the result of macro expansion, and show a macro's definition, including |
| where it was defined. |
| |
| You may need to compile your program specially to provide @value{GDBN} |
| with information about preprocessor macros. Most compilers do not |
| include macros in their debugging information, even when you compile |
| with the @option{-g} flag. @xref{Compilation}. |
| |
| A program may define a macro at one point, remove that definition later, |
| and then provide a different definition after that. Thus, at different |
| points in the program, a macro may have different definitions, or have |
| no definition at all. If there is a current stack frame, @value{GDBN} |
| uses the macros in scope at that frame's source code line. Otherwise, |
| @value{GDBN} uses the macros in scope at the current listing location; |
| see @ref{List}. |
| |
| Whenever @value{GDBN} evaluates an expression, it always expands any |
| macro invocations present in the expression. @value{GDBN} also provides |
| the following commands for working with macros explicitly. |
| |
| @table @code |
| |
| @kindex macro expand |
| @cindex macro expansion, showing the results of preprocessor |
| @cindex preprocessor macro expansion, showing the results of |
| @cindex expanding preprocessor macros |
| @item macro expand @var{expression} |
| @itemx macro exp @var{expression} |
| Show the results of expanding all preprocessor macro invocations in |
| @var{expression}. Since @value{GDBN} simply expands macros, but does |
| not parse the result, @var{expression} need not be a valid expression; |
| it can be any string of tokens. |
| |
| @kindex macro exp1 |
| @item macro expand-once @var{expression} |
| @itemx macro exp1 @var{expression} |
| @cindex expand macro once |
| @i{(This command is not yet implemented.)} Show the results of |
| expanding those preprocessor macro invocations that appear explicitly in |
| @var{expression}. Macro invocations appearing in that expansion are |
| left unchanged. This command allows you to see the effect of a |
| particular macro more clearly, without being confused by further |
| expansions. Since @value{GDBN} simply expands macros, but does not |
| parse the result, @var{expression} need not be a valid expression; it |
| can be any string of tokens. |
| |
| @kindex info macro |
| @cindex macro definition, showing |
| @cindex definition of a macro, showing |
| @cindex macros, from debug info |
| @item info macro [-a|-all] [--] @var{macro} |
| Show the current definition or all definitions of the named @var{macro}, |
| and describe the source location or compiler command-line where that |
| definition was established. The optional double dash is to signify the end of |
| argument processing and the beginning of @var{macro} for non C-like macros where |
| the macro may begin with a hyphen. |
| |
| @kindex info macros |
| @item info macros @var{linespec} |
| Show all macro definitions that are in effect at the location specified |
| by @var{linespec}, and describe the source location or compiler |
| command-line where those definitions were established. |
| |
| @kindex macro define |
| @cindex user-defined macros |
| @cindex defining macros interactively |
| @cindex macros, user-defined |
| @item macro define @var{macro} @var{replacement-list} |
| @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list} |
| Introduce a definition for a preprocessor macro named @var{macro}, |
| invocations of which are replaced by the tokens given in |
| @var{replacement-list}. The first form of this command defines an |
| ``object-like'' macro, which takes no arguments; the second form |
| defines a ``function-like'' macro, which takes the arguments given in |
| @var{arglist}. |
| |
| A definition introduced by this command is in scope in every |
| expression evaluated in @value{GDBN}, until it is removed with the |
| @code{macro undef} command, described below. The definition overrides |
| all definitions for @var{macro} present in the program being debugged, |
| as well as any previous user-supplied definition. |
| |
| @kindex macro undef |
| @item macro undef @var{macro} |
| Remove any user-supplied definition for the macro named @var{macro}. |
| This command only affects definitions provided with the @code{macro |
| define} command, described above; it cannot remove definitions present |
| in the program being debugged. |
| |
| @kindex macro list |
| @item macro list |
| List all the macros defined using the @code{macro define} command. |
| @end table |
| |
| @cindex macros, example of debugging with |
| Here is a transcript showing the above commands in action. First, we |
| show our source files: |
| |
| @smallexample |
| $ cat sample.c |
| #include <stdio.h> |
| #include "sample.h" |
| |
| #define M 42 |
| #define ADD(x) (M + x) |
| |
| main () |
| @{ |
| #define N 28 |
| printf ("Hello, world!\n"); |
| #undef N |
| printf ("We're so creative.\n"); |
| #define N 1729 |
| printf ("Goodbye, world!\n"); |
| @} |
| $ cat sample.h |
| #define Q < |
| $ |
| @end smallexample |
| |
| Now, we compile the program using the @sc{gnu} C compiler, |
| @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the |
| minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3} |
| and @option{-gdwarf-4}; we recommend always choosing the most recent |
| version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler |
| includes information about preprocessor macros in the debugging |
| information. |
| |
| @smallexample |
| $ gcc -gdwarf-2 -g3 sample.c -o sample |
| $ |
| @end smallexample |
| |
| Now, we start @value{GDBN} on our sample program: |
| |
| @smallexample |
| $ gdb -nw sample |
| GNU gdb 2002-05-06-cvs |
| Copyright 2002 Free Software Foundation, Inc. |
| GDB is free software, @dots{} |
| (@value{GDBP}) |
| @end smallexample |
| |
| We can expand macros and examine their definitions, even when the |
| program is not running. @value{GDBN} uses the current listing position |
| to decide which macro definitions are in scope: |
| |
| @smallexample |
| (@value{GDBP}) list main |
| 3 |
| 4 #define M 42 |
| 5 #define ADD(x) (M + x) |
| 6 |
| 7 main () |
| 8 @{ |
| 9 #define N 28 |
| 10 printf ("Hello, world!\n"); |
| 11 #undef N |
| 12 printf ("We're so creative.\n"); |
| (@value{GDBP}) info macro ADD |
| Defined at /home/jimb/gdb/macros/play/sample.c:5 |
| #define ADD(x) (M + x) |
| (@value{GDBP}) info macro Q |
| Defined at /home/jimb/gdb/macros/play/sample.h:1 |
| included at /home/jimb/gdb/macros/play/sample.c:2 |
| #define Q < |
| (@value{GDBP}) macro expand ADD(1) |
| expands to: (42 + 1) |
| (@value{GDBP}) macro expand-once ADD(1) |
| expands to: once (M + 1) |
| (@value{GDBP}) |
| @end smallexample |
| |
| In the example above, note that @code{macro expand-once} expands only |
| the macro invocation explicit in the original text --- the invocation of |
| @code{ADD} --- but does not expand the invocation of the macro @code{M}, |
| which was introduced by @code{ADD}. |
| |
| Once the program is running, @value{GDBN} uses the macro definitions in |
| force at the source line of the current stack frame: |
| |
| @smallexample |
| (@value{GDBP}) break main |
| Breakpoint 1 at 0x8048370: file sample.c, line 10. |
| (@value{GDBP}) run |
| Starting program: /home/jimb/gdb/macros/play/sample |
| |
| Breakpoint 1, main () at sample.c:10 |
| 10 printf ("Hello, world!\n"); |
| (@value{GDBP}) |
| @end smallexample |
| |
| At line 10, the definition of the macro @code{N} at line 9 is in force: |
| |
| @smallexample |
| (@value{GDBP}) info macro N |
| Defined at /home/jimb/gdb/macros/play/sample.c:9 |
| #define N 28 |
| (@value{GDBP}) macro expand N Q M |
| expands to: 28 < 42 |
| (@value{GDBP}) print N Q M |
| $1 = 1 |
| (@value{GDBP}) |
| @end smallexample |
| |
| As we step over directives that remove @code{N}'s definition, and then |
| give it a new definition, @value{GDBN} finds the definition (or lack |
| thereof) in force at each point: |
| |
| @smallexample |
| (@value{GDBP}) next |
| Hello, world! |
| 12 printf ("We're so creative.\n"); |
| (@value{GDBP}) info macro N |
| The symbol `N' has no definition as a C/C++ preprocessor macro |
| at /home/jimb/gdb/macros/play/sample.c:12 |
| (@value{GDBP}) next |
| We're so creative. |
| 14 printf ("Goodbye, world!\n"); |
| (@value{GDBP}) info macro N |
| Defined at /home/jimb/gdb/macros/play/sample.c:13 |
| #define N 1729 |
| (@value{GDBP}) macro expand N Q M |
| expands to: 1729 < 42 |
| (@value{GDBP}) print N Q M |
| $2 = 0 |
| (@value{GDBP}) |
| @end smallexample |
| |
| In addition to source files, macros can be defined on the compilation command |
| line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in |
| such a way, @value{GDBN} displays the location of their definition as line zero |
| of the source file submitted to the compiler. |
| |
| @smallexample |
| (@value{GDBP}) info macro __STDC__ |
| Defined at /home/jimb/gdb/macros/play/sample.c:0 |
| -D__STDC__=1 |
| (@value{GDBP}) |
| @end smallexample |
| |
| |
| @node Tracepoints |
| @chapter Tracepoints |
| @c This chapter is based on the documentation written by Michael |
| @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni. |
| |
| @cindex tracepoints |
| In some applications, it is not feasible for the debugger to interrupt |
| the program's execution long enough for the developer to learn |
| anything helpful about its behavior. If the program's correctness |
| depends on its real-time behavior, delays introduced by a debugger |
| might cause the program to change its behavior drastically, or perhaps |
| fail, even when the code itself is correct. It is useful to be able |
| to observe the program's behavior without interrupting it. |
| |
| Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can |
| specify locations in the program, called @dfn{tracepoints}, and |
| arbitrary expressions to evaluate when those tracepoints are reached. |
| Later, using the @code{tfind} command, you can examine the values |
| those expressions had when the program hit the tracepoints. The |
| expressions may also denote objects in memory---structures or arrays, |
| for example---whose values @value{GDBN} should record; while visiting |
| a particular tracepoint, you may inspect those objects as if they were |
| in memory at that moment. However, because @value{GDBN} records these |
| values without interacting with you, it can do so quickly and |
| unobtrusively, hopefully not disturbing the program's behavior. |
| |
| The tracepoint facility is currently available only for remote |
| targets. @xref{Targets}. In addition, your remote target must know |
| how to collect trace data. This functionality is implemented in the |
| remote stub; however, none of the stubs distributed with @value{GDBN} |
| support tracepoints as of this writing. The format of the remote |
| packets used to implement tracepoints are described in @ref{Tracepoint |
| Packets}. |
| |
| It is also possible to get trace data from a file, in a manner reminiscent |
| of corefiles; you specify the filename, and use @code{tfind} to search |
| through the file. @xref{Trace Files}, for more details. |
| |
| This chapter describes the tracepoint commands and features. |
| |
| @menu |
| * Set Tracepoints:: |
| * Analyze Collected Data:: |
| * Tracepoint Variables:: |
| * Trace Files:: |
| @end menu |
| |
| @node Set Tracepoints |
| @section Commands to Set Tracepoints |
| |
| Before running such a @dfn{trace experiment}, an arbitrary number of |
| tracepoints can be set. A tracepoint is actually a special type of |
| breakpoint (@pxref{Set Breaks}), so you can manipulate it using |
| standard breakpoint commands. For instance, as with breakpoints, |
| tracepoint numbers are successive integers starting from one, and many |
| of the commands associated with tracepoints take the tracepoint number |
| as their argument, to identify which tracepoint to work on. |
| |
| For each tracepoint, you can specify, in advance, some arbitrary set |
| of data that you want the target to collect in the trace buffer when |
| it hits that tracepoint. The collected data can include registers, |
| local variables, or global data. Later, you can use @value{GDBN} |
| commands to examine the values these data had at the time the |
| tracepoint was hit. |
| |
| Tracepoints do not support every breakpoint feature. Ignore counts on |
| tracepoints have no effect, and tracepoints cannot run @value{GDBN} |
| commands when they are hit. Tracepoints may not be thread-specific |
| either. |
| |
| @cindex fast tracepoints |
| Some targets may support @dfn{fast tracepoints}, which are inserted in |
| a different way (such as with a jump instead of a trap), that is |
| faster but possibly restricted in where they may be installed. |
| |
| @cindex static tracepoints |
| @cindex markers, static tracepoints |
| @cindex probing markers, static tracepoints |
| Regular and fast tracepoints are dynamic tracing facilities, meaning |
| that they can be used to insert tracepoints at (almost) any location |
| in the target. Some targets may also support controlling @dfn{static |
| tracepoints} from @value{GDBN}. With static tracing, a set of |
| instrumentation points, also known as @dfn{markers}, are embedded in |
| the target program, and can be activated or deactivated by name or |
| address. These are usually placed at locations which facilitate |
| investigating what the target is actually doing. @value{GDBN}'s |
| support for static tracing includes being able to list instrumentation |
| points, and attach them with @value{GDBN} defined high level |
| tracepoints that expose the whole range of convenience of |
| @value{GDBN}'s tracepoints support. Namely, support for collecting |
| registers values and values of global or local (to the instrumentation |
| point) variables; tracepoint conditions and trace state variables. |
| The act of installing a @value{GDBN} static tracepoint on an |
| instrumentation point, or marker, is referred to as @dfn{probing} a |
| static tracepoint marker. |
| |
| @code{gdbserver} supports tracepoints on some target systems. |
| @xref{Server,,Tracepoints support in @code{gdbserver}}. |
| |
| This section describes commands to set tracepoints and associated |
| conditions and actions. |
| |
| @menu |
| * Create and Delete Tracepoints:: |
| * Enable and Disable Tracepoints:: |
| * Tracepoint Passcounts:: |
| * Tracepoint Conditions:: |
| * Trace State Variables:: |
| * Tracepoint Actions:: |
| * Listing Tracepoints:: |
| * Listing Static Tracepoint Markers:: |
| * Starting and Stopping Trace Experiments:: |
| * Tracepoint Restrictions:: |
| @end menu |
| |
| @node Create and Delete Tracepoints |
| @subsection Create and Delete Tracepoints |
| |
| @table @code |
| @cindex set tracepoint |
| @kindex trace |
| @item trace @var{location} |
| The @code{trace} command is very similar to the @code{break} command. |
| Its argument @var{location} can be a source line, a function name, or |
| an address in the target program. @xref{Specify Location}. The |
| @code{trace} command defines a tracepoint, which is a point in the |
| target program where the debugger will briefly stop, collect some |
| data, and then allow the program to continue. Setting a tracepoint or |
| changing its actions takes effect immediately if the remote stub |
| supports the @samp{InstallInTrace} feature (@pxref{install tracepoint |
| in tracing}). |
| If remote stub doesn't support the @samp{InstallInTrace} feature, all |
| these changes don't take effect until the next @code{tstart} |
| command, and once a trace experiment is running, further changes will |
| not have any effect until the next trace experiment starts. In addition, |
| @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose |
| address is not yet resolved. (This is similar to pending breakpoints.) |
| Pending tracepoints are not downloaded to the target and not installed |
| until they are resolved. The resolution of pending tracepoints requires |
| @value{GDBN} support---when debugging with the remote target, and |
| @value{GDBN} disconnects from the remote stub (@pxref{disconnected |
| tracing}), pending tracepoints can not be resolved (and downloaded to |
| the remote stub) while @value{GDBN} is disconnected. |
| |
| Here are some examples of using the @code{trace} command: |
| |
| @smallexample |
| (@value{GDBP}) @b{trace foo.c:121} // a source file and line number |
| |
| (@value{GDBP}) @b{trace +2} // 2 lines forward |
| |
| (@value{GDBP}) @b{trace my_function} // first source line of function |
| |
| (@value{GDBP}) @b{trace *my_function} // EXACT start address of function |
| |
| (@value{GDBP}) @b{trace *0x2117c4} // an address |
| @end smallexample |
| |
| @noindent |
| You can abbreviate @code{trace} as @code{tr}. |
| |
| @item trace @var{location} if @var{cond} |
| Set a tracepoint with condition @var{cond}; evaluate the expression |
| @var{cond} each time the tracepoint is reached, and collect data only |
| if the value is nonzero---that is, if @var{cond} evaluates as true. |
| @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more |
| information on tracepoint conditions. |
| |
| @item ftrace @var{location} [ if @var{cond} ] |
| @cindex set fast tracepoint |
| @cindex fast tracepoints, setting |
| @kindex ftrace |
| The @code{ftrace} command sets a fast tracepoint. For targets that |
| support them, fast tracepoints will use a more efficient but possibly |
| less general technique to trigger data collection, such as a jump |
| instruction instead of a trap, or some sort of hardware support. It |
| may not be possible to create a fast tracepoint at the desired |
| location, in which case the command will exit with an explanatory |
| message. |
| |
| @value{GDBN} handles arguments to @code{ftrace} exactly as for |
| @code{trace}. |
| |
| On 32-bit x86-architecture systems, fast tracepoints normally need to |
| be placed at an instruction that is 5 bytes or longer, but can be |
| placed at 4-byte instructions if the low 64K of memory of the target |
| program is available to install trampolines. Some Unix-type systems, |
| such as @sc{gnu}/Linux, exclude low addresses from the program's |
| address space; but for instance with the Linux kernel it is possible |
| to let @value{GDBN} use this area by doing a @command{sysctl} command |
| to set the @code{mmap_min_addr} kernel parameter, as in |
| |
| @example |
| sudo sysctl -w vm.mmap_min_addr=32768 |
| @end example |
| |
| @noindent |
| which sets the low address to 32K, which leaves plenty of room for |
| trampolines. The minimum address should be set to a page boundary. |
| |
| @item strace @var{location} [ if @var{cond} ] |
| @cindex set static tracepoint |
| @cindex static tracepoints, setting |
| @cindex probe static tracepoint marker |
| @kindex strace |
| The @code{strace} command sets a static tracepoint. For targets that |
| support it, setting a static tracepoint probes a static |
| instrumentation point, or marker, found at @var{location}. It may not |
| be possible to set a static tracepoint at the desired location, in |
| which case the command will exit with an explanatory message. |
| |
| @value{GDBN} handles arguments to @code{strace} exactly as for |
| @code{trace}, with the addition that the user can also specify |
| @code{-m @var{marker}} as @var{location}. This probes the marker |
| identified by the @var{marker} string identifier. This identifier |
| depends on the static tracepoint backend library your program is |
| using. You can find all the marker identifiers in the @samp{ID} field |
| of the @code{info static-tracepoint-markers} command output. |
| @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint |
| Markers}. For example, in the following small program using the UST |
| tracing engine: |
| |
| @smallexample |
| main () |
| @{ |
| trace_mark(ust, bar33, "str %s", "FOOBAZ"); |
| @} |
| @end smallexample |
| |
| @noindent |
| the marker id is composed of joining the first two arguments to the |
| @code{trace_mark} call with a slash, which translates to: |
| |
| @smallexample |
| (@value{GDBP}) info static-tracepoint-markers |
| Cnt Enb ID Address What |
| 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22 |
| Data: "str %s" |
| [etc...] |
| @end smallexample |
| |
| @noindent |
| so you may probe the marker above with: |
| |
| @smallexample |
| (@value{GDBP}) strace -m ust/bar33 |
| @end smallexample |
| |
| Static tracepoints accept an extra collect action --- @code{collect |
| $_sdata}. This collects arbitrary user data passed in the probe point |
| call to the tracing library. In the UST example above, you'll see |
| that the third argument to @code{trace_mark} is a printf-like format |
| string. The user data is then the result of running that formating |
| string against the following arguments. Note that @code{info |
| static-tracepoint-markers} command output lists that format string in |
| the @samp{Data:} field. |
| |
| You can inspect this data when analyzing the trace buffer, by printing |
| the $_sdata variable like any other variable available to |
| @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}. |
| |
| @vindex $tpnum |
| @cindex last tracepoint number |
| @cindex recent tracepoint number |
| @cindex tracepoint number |
| The convenience variable @code{$tpnum} records the tracepoint number |
| of the most recently set tracepoint. |
| |
| @kindex delete tracepoint |
| @cindex tracepoint deletion |
| @item delete tracepoint @r{[}@var{num}@r{]} |
| Permanently delete one or more tracepoints. With no argument, the |
| default is to delete all tracepoints. Note that the regular |
| @code{delete} command can remove tracepoints also. |
| |
| Examples: |
| |
| @smallexample |
| (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints |
| |
| (@value{GDBP}) @b{delete trace} // remove all tracepoints |
| @end smallexample |
| |
| @noindent |
| You can abbreviate this command as @code{del tr}. |
| @end table |
| |
| @node Enable and Disable Tracepoints |
| @subsection Enable and Disable Tracepoints |
| |
| These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}. |
| |
| @table @code |
| @kindex disable tracepoint |
| @item disable tracepoint @r{[}@var{num}@r{]} |
| Disable tracepoint @var{num}, or all tracepoints if no argument |
| @var{num} is given. A disabled tracepoint will have no effect during |
| a trace experiment, but it is not forgotten. You can re-enable |
| a disabled tracepoint using the @code{enable tracepoint} command. |
| If the command is issued during a trace experiment and the debug target |
| has support for disabling tracepoints during a trace experiment, then the |
| change will be effective immediately. Otherwise, it will be applied to the |
| next trace experiment. |
| |
| @kindex enable tracepoint |
| @item enable tracepoint @r{[}@var{num}@r{]} |
| Enable tracepoint @var{num}, or all tracepoints. If this command is |
| issued during a trace experiment and the debug target supports enabling |
| tracepoints during a trace experiment, then the enabled tracepoints will |
| become effective immediately. Otherwise, they will become effective the |
| next time a trace experiment is run. |
| @end table |
| |
| @node Tracepoint Passcounts |
| @subsection Tracepoint Passcounts |
| |
| @table @code |
| @kindex passcount |
| @cindex tracepoint pass count |
| @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]} |
| Set the @dfn{passcount} of a tracepoint. The passcount is a way to |
| automatically stop a trace experiment. If a tracepoint's passcount is |
| @var{n}, then the trace experiment will be automatically stopped on |
| the @var{n}'th time that tracepoint is hit. If the tracepoint number |
| @var{num} is not specified, the @code{passcount} command sets the |
| passcount of the most recently defined tracepoint. If no passcount is |
| given, the trace experiment will run until stopped explicitly by the |
| user. |
| |
| Examples: |
| |
| @smallexample |
| (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of |
| @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2} |
| |
| (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the |
| @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.} |
| (@value{GDBP}) @b{trace foo} |
| (@value{GDBP}) @b{pass 3} |
| (@value{GDBP}) @b{trace bar} |
| (@value{GDBP}) @b{pass 2} |
| (@value{GDBP}) @b{trace baz} |
| (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been |
| @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has} |
| @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times} |
| @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.} |
| @end smallexample |
| @end table |
| |
| @node Tracepoint Conditions |
| @subsection Tracepoint Conditions |
| @cindex conditional tracepoints |
| @cindex tracepoint conditions |
| |
| The simplest sort of tracepoint collects data every time your program |
| reaches a specified place. You can also specify a @dfn{condition} for |
| a tracepoint. A condition is just a Boolean expression in your |
| programming language (@pxref{Expressions, ,Expressions}). A |
| tracepoint with a condition evaluates the expression each time your |
| program reaches it, and data collection happens only if the condition |
| is true. |
| |
| Tracepoint conditions can be specified when a tracepoint is set, by |
| using @samp{if} in the arguments to the @code{trace} command. |
| @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can |
| also be set or changed at any time with the @code{condition} command, |
| just as with breakpoints. |
| |
| Unlike breakpoint conditions, @value{GDBN} does not actually evaluate |
| the conditional expression itself. Instead, @value{GDBN} encodes the |
| expression into an agent expression (@pxref{Agent Expressions}) |
| suitable for execution on the target, independently of @value{GDBN}. |
| Global variables become raw memory locations, locals become stack |
| accesses, and so forth. |
| |
| For instance, suppose you have a function that is usually called |
| frequently, but should not be called after an error has occurred. You |
| could use the following tracepoint command to collect data about calls |
| of that function that happen while the error code is propagating |
| through the program; an unconditional tracepoint could end up |
| collecting thousands of useless trace frames that you would have to |
| search through. |
| |
| @smallexample |
| (@value{GDBP}) @kbd{trace normal_operation if errcode > 0} |
| @end smallexample |
| |
| @node Trace State Variables |
| @subsection Trace State Variables |
| @cindex trace state variables |
| |
| A @dfn{trace state variable} is a special type of variable that is |
| created and managed by target-side code. The syntax is the same as |
| that for GDB's convenience variables (a string prefixed with ``$''), |
| but they are stored on the target. They must be created explicitly, |
| using a @code{tvariable} command. They are always 64-bit signed |
| integers. |
| |
| Trace state variables are remembered by @value{GDBN}, and downloaded |
| to the target along with tracepoint information when the trace |
| experiment starts. There are no intrinsic limits on the number of |
| trace state variables, beyond memory limitations of the target. |
| |
| @cindex convenience variables, and trace state variables |
| Although trace state variables are managed by the target, you can use |
| them in print commands and expressions as if they were convenience |
| variables; @value{GDBN} will get the current value from the target |
| while the trace experiment is running. Trace state variables share |
| the same namespace as other ``$'' variables, which means that you |
| cannot have trace state variables with names like @code{$23} or |
| @code{$pc}, nor can you have a trace state variable and a convenience |
| variable with the same name. |
| |
| @table @code |
| |
| @item tvariable $@var{name} [ = @var{expression} ] |
| @kindex tvariable |
| The @code{tvariable} command creates a new trace state variable named |
| @code{$@var{name}}, and optionally gives it an initial value of |
| @var{expression}. @var{expression} is evaluated when this command is |
| entered; the result will be converted to an integer if possible, |
| otherwise @value{GDBN} will report an error. A subsequent |
| @code{tvariable} command specifying the same name does not create a |
| variable, but instead assigns the supplied initial value to the |
| existing variable of that name, overwriting any previous initial |
| value. The default initial value is 0. |
| |
| @item info tvariables |
| @kindex info tvariables |
| List all the trace state variables along with their initial values. |
| Their current values may also be displayed, if the trace experiment is |
| currently running. |
| |
| @item delete tvariable @r{[} $@var{name} @dots{} @r{]} |
| @kindex delete tvariable |
| Delete the given trace state variables, or all of them if no arguments |
| are specified. |
| |
| @end table |
| |
| @node Tracepoint Actions |
| @subsection Tracepoint Action Lists |
| |
| @table @code |
| @kindex actions |
| @cindex tracepoint actions |
| @item actions @r{[}@var{num}@r{]} |
| This command will prompt for a list of actions to be taken when the |
| tracepoint is hit. If the tracepoint number @var{num} is not |
| specified, this command sets the actions for the one that was most |
| recently defined (so that you can define a tracepoint and then say |
| @code{actions} without bothering about its number). You specify the |
| actions themselves on the following lines, one action at a time, and |
| terminate the actions list with a line containing just @code{end}. So |
| far, the only defined actions are @code{collect}, @code{teval}, and |
| @code{while-stepping}. |
| |
| @code{actions} is actually equivalent to @code{commands} (@pxref{Break |
| Commands, ,Breakpoint Command Lists}), except that only the defined |
| actions are allowed; any other @value{GDBN} command is rejected. |
| |
| @cindex remove actions from a tracepoint |
| To remove all actions from a tracepoint, type @samp{actions @var{num}} |
| and follow it immediately with @samp{end}. |
| |
| @smallexample |
| (@value{GDBP}) @b{collect @var{data}} // collect some data |
| |
| (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data |
| |
| (@value{GDBP}) @b{end} // signals the end of actions. |
| @end smallexample |
| |
| In the following example, the action list begins with @code{collect} |
| commands indicating the things to be collected when the tracepoint is |
| hit. Then, in order to single-step and collect additional data |
| following the tracepoint, a @code{while-stepping} command is used, |
| followed by the list of things to be collected after each step in a |
| sequence of single steps. The @code{while-stepping} command is |
| terminated by its own separate @code{end} command. Lastly, the action |
| list is terminated by an @code{end} command. |
| |
| @smallexample |
| (@value{GDBP}) @b{trace foo} |
| (@value{GDBP}) @b{actions} |
| Enter actions for tracepoint 1, one per line: |
| > collect bar,baz |
| > collect $regs |
| > while-stepping 12 |
| > collect $pc, arr[i] |
| > end |
| end |
| @end smallexample |
| |
| @kindex collect @r{(tracepoints)} |
| @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{} |
| Collect values of the given expressions when the tracepoint is hit. |
| This command accepts a comma-separated list of any valid expressions. |
| In addition to global, static, or local variables, the following |
| special arguments are supported: |
| |
| @table @code |
| @item $regs |
| Collect all registers. |
| |
| @item $args |
| Collect all function arguments. |
| |
| @item $locals |
| Collect all local variables. |
| |
| @item $_ret |
| Collect the return address. This is helpful if you want to see more |
| of a backtrace. |
| |
| @item $_probe_argc |
| Collects the number of arguments from the static probe at which the |
| tracepoint is located. |
| @xref{Static Probe Points}. |
| |
| @item $_probe_arg@var{n} |
| @var{n} is an integer between 0 and 11. Collects the @var{n}th argument |
| from the static probe at which the tracepoint is located. |
| @xref{Static Probe Points}. |
| |
| @item $_sdata |
| @vindex $_sdata@r{, collect} |
| Collect static tracepoint marker specific data. Only available for |
| static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action |
| Lists}. On the UST static tracepoints library backend, an |
| instrumentation point resembles a @code{printf} function call. The |
| tracing library is able to collect user specified data formatted to a |
| character string using the format provided by the programmer that |
| instrumented the program. Other backends have similar mechanisms. |
| Here's an example of a UST marker call: |
| |
| @smallexample |
| const char master_name[] = "$your_name"; |
| trace_mark(channel1, marker1, "hello %s", master_name) |
| @end smallexample |
| |
| In this case, collecting @code{$_sdata} collects the string |
| @samp{hello $yourname}. When analyzing the trace buffer, you can |
| inspect @samp{$_sdata} like any other variable available to |
| @value{GDBN}. |
| @end table |
| |
| You can give several consecutive @code{collect} commands, each one |
| with a single argument, or one @code{collect} command with several |
| arguments separated by commas; the effect is the same. |
| |
| The optional @var{mods} changes the usual handling of the arguments. |
| @code{s} requests that pointers to chars be handled as strings, in |
| particular collecting the contents of the memory being pointed at, up |
| to the first zero. The upper bound is by default the value of the |
| @code{print elements} variable; if @code{s} is followed by a decimal |
| number, that is the upper bound instead. So for instance |
| @samp{collect/s25 mystr} collects as many as 25 characters at |
| @samp{mystr}. |
| |
| The command @code{info scope} (@pxref{Symbols, info scope}) is |
| particularly useful for figuring out what data to collect. |
| |
| @kindex teval @r{(tracepoints)} |
| @item teval @var{expr1}, @var{expr2}, @dots{} |
| Evaluate the given expressions when the tracepoint is hit. This |
| command accepts a comma-separated list of expressions. The results |
| are discarded, so this is mainly useful for assigning values to trace |
| state variables (@pxref{Trace State Variables}) without adding those |
| values to the trace buffer, as would be the case if the @code{collect} |
| action were used. |
| |
| @kindex while-stepping @r{(tracepoints)} |
| @item while-stepping @var{n} |
| Perform @var{n} single-step instruction traces after the tracepoint, |
| collecting new data after each step. The @code{while-stepping} |
| command is followed by the list of what to collect while stepping |
| (followed by its own @code{end} command): |
| |
| @smallexample |
| > while-stepping 12 |
| > collect $regs, myglobal |
| > end |
| > |
| @end smallexample |
| |
| @noindent |
| Note that @code{$pc} is not automatically collected by |
| @code{while-stepping}; you need to explicitly collect that register if |
| you need it. You may abbreviate @code{while-stepping} as @code{ws} or |
| @code{stepping}. |
| |
| @item set default-collect @var{expr1}, @var{expr2}, @dots{} |
| @kindex set default-collect |
| @cindex default collection action |
| This variable is a list of expressions to collect at each tracepoint |
| hit. It is effectively an additional @code{collect} action prepended |
| to every tracepoint action list. The expressions are parsed |
| individually for each tracepoint, so for instance a variable named |
| @code{xyz} may be interpreted as a global for one tracepoint, and a |
| local for another, as appropriate to the tracepoint's location. |
| |
| @item show default-collect |
| @kindex show default-collect |
| Show the list of expressions that are collected by default at each |
| tracepoint hit. |
| |
| @end table |
| |
| @node Listing Tracepoints |
| @subsection Listing Tracepoints |
| |
| @table @code |
| @kindex info tracepoints @r{[}@var{n}@dots{}@r{]} |
| @kindex info tp @r{[}@var{n}@dots{}@r{]} |
| @cindex information about tracepoints |
| @item info tracepoints @r{[}@var{num}@dots{}@r{]} |
| Display information about the tracepoint @var{num}. If you don't |
| specify a tracepoint number, displays information about all the |
| tracepoints defined so far. The format is similar to that used for |
| @code{info breakpoints}; in fact, @code{info tracepoints} is the same |
| command, simply restricting itself to tracepoints. |
| |
| A tracepoint's listing may include additional information specific to |
| tracing: |
| |
| @itemize @bullet |
| @item |
| its passcount as given by the @code{passcount @var{n}} command |
| @end itemize |
| |
| @smallexample |
| (@value{GDBP}) @b{info trace} |
| Num Type Disp Enb Address What |
| 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7 |
| while-stepping 20 |
| collect globfoo, $regs |
| end |
| collect globfoo2 |
| end |
| pass count 1200 |
| (@value{GDBP}) |
| @end smallexample |
| |
| @noindent |
| This command can be abbreviated @code{info tp}. |
| @end table |
| |
| @node Listing Static Tracepoint Markers |
| @subsection Listing Static Tracepoint Markers |
| |
| @table @code |
| @kindex info static-tracepoint-markers |
| @cindex information about static tracepoint markers |
| @item info static-tracepoint-markers |
| Display information about all static tracepoint markers defined in the |
| program. |
| |
| For each marker, the following columns are printed: |
| |
| @table @emph |
| @item Count |
| An incrementing counter, output to help readability. This is not a |
| stable identifier. |
| @item ID |
| The marker ID, as reported by the target. |
| @item Enabled or Disabled |
| Probed markers are tagged with @samp{y}. @samp{n} identifies marks |
| that are not enabled. |
| @item Address |
| Where the marker is in your program, as a memory address. |
| @item What |
| Where the marker is in the source for your program, as a file and line |
| number. If the debug information included in the program does not |
| allow @value{GDBN} to locate the source of the marker, this column |
| will be left blank. |
| @end table |
| |
| @noindent |
| In addition, the following information may be printed for each marker: |
| |
| @table @emph |
| @item Data |
| User data passed to the tracing library by the marker call. In the |
| UST backend, this is the format string passed as argument to the |
| marker call. |
| @item Static tracepoints probing the marker |
| The list of static tracepoints attached to the marker. |
| @end table |
| |
| @smallexample |
| (@value{GDBP}) info static-tracepoint-markers |
| Cnt ID Enb Address What |
| 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25 |
| Data: number1 %d number2 %d |
| Probed by static tracepoints: #2 |
| 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24 |
| Data: str %s |
| (@value{GDBP}) |
| @end smallexample |
| @end table |
| |
| @node Starting and Stopping Trace Experiments |
| @subsection Starting and Stopping Trace Experiments |
| |
| @table @code |
| @kindex tstart [ @var{notes} ] |
| @cindex start a new trace experiment |
| @cindex collected data discarded |
| @item tstart |
| This command starts the trace experiment, and begins collecting data. |
| It has the side effect of discarding all the data collected in the |
| trace buffer during the previous trace experiment. If any arguments |
| are supplied, they are taken as a note and stored with the trace |
| experiment's state. The notes may be arbitrary text, and are |
| especially useful with disconnected tracing in a multi-user context; |
| the notes can explain what the trace is doing, supply user contact |
| information, and so forth. |
| |
| @kindex tstop [ @var{notes} ] |
| @cindex stop a running trace experiment |
| @item tstop |
| This command stops the trace experiment. If any arguments are |
| supplied, they are recorded with the experiment as a note. This is |
| useful if you are stopping a trace started by someone else, for |
| instance if the trace is interfering with the system's behavior and |
| needs to be stopped quickly. |
| |
| @strong{Note}: a trace experiment and data collection may stop |
| automatically if any tracepoint's passcount is reached |
| (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full. |
| |
| @kindex tstatus |
| @cindex status of trace data collection |
| @cindex trace experiment, status of |
| @item tstatus |
| This command displays the status of the current trace data |
| collection. |
| @end table |
| |
| Here is an example of the commands we described so far: |
| |
| @smallexample |
| (@value{GDBP}) @b{trace gdb_c_test} |
| (@value{GDBP}) @b{actions} |
| Enter actions for tracepoint #1, one per line. |
| > collect $regs,$locals,$args |
| > while-stepping 11 |
| > collect $regs |
| > end |
| > end |
| (@value{GDBP}) @b{tstart} |
| [time passes @dots{}] |
| (@value{GDBP}) @b{tstop} |
| @end smallexample |
| |
| @anchor{disconnected tracing} |
| @cindex disconnected tracing |
| You can choose to continue running the trace experiment even if |
| @value{GDBN} disconnects from the target, voluntarily or |
| involuntarily. For commands such as @code{detach}, the debugger will |
| ask what you want to do with the trace. But for unexpected |
| terminations (@value{GDBN} crash, network outage), it would be |
| unfortunate to lose hard-won trace data, so the variable |
| @code{disconnected-tracing} lets you decide whether the trace should |
| continue running without @value{GDBN}. |
| |
| @table @code |
| @item set disconnected-tracing on |
| @itemx set disconnected-tracing off |
| @kindex set disconnected-tracing |
| Choose whether a tracing run should continue to run if @value{GDBN} |
| has disconnected from the target. Note that @code{detach} or |
| @code{quit} will ask you directly what to do about a running trace no |
| matter what this variable's setting, so the variable is mainly useful |
| for handling unexpected situations, such as loss of the network. |
| |
| @item show disconnected-tracing |
| @kindex show disconnected-tracing |
| Show the current choice for disconnected tracing. |
| |
| @end table |
| |
| When you reconnect to the target, the trace experiment may or may not |
| still be running; it might have filled the trace buffer in the |
| meantime, or stopped for one of the other reasons. If it is running, |
| it will continue after reconnection. |
| |
| Upon reconnection, the target will upload information about the |
| tracepoints in effect. @value{GDBN} will then compare that |
| information to the set of tracepoints currently defined, and attempt |
| to match them up, allowing for the possibility that the numbers may |
| have changed due to creation and deletion in the meantime. If one of |
| the target's tracepoints does not match any in @value{GDBN}, the |
| debugger will create a new tracepoint, so that you have a number with |
| which to specify that tracepoint. This matching-up process is |
| necessarily heuristic, and it may result in useless tracepoints being |
| created; you may simply delete them if they are of no use. |
| |
| @cindex circular trace buffer |
| If your target agent supports a @dfn{circular trace buffer}, then you |
| can run a trace experiment indefinitely without filling the trace |
| buffer; when space runs out, the agent deletes already-collected trace |
| frames, oldest first, until there is enough room to continue |
| collecting. This is especially useful if your tracepoints are being |
| hit too often, and your trace gets terminated prematurely because the |
| buffer is full. To ask for a circular trace buffer, simply set |
| @samp{circular-trace-buffer} to on. You can set this at any time, |
| including during tracing; if the agent can do it, it will change |
| buffer handling on the fly, otherwise it will not take effect until |
| the next run. |
| |
| @table @code |
| @item set circular-trace-buffer on |
| @itemx set circular-trace-buffer off |
| @kindex set circular-trace-buffer |
| Choose whether a tracing run should use a linear or circular buffer |
| for trace data. A linear buffer will not lose any trace data, but may |
| fill up prematurely, while a circular buffer will discard old trace |
| data, but it will have always room for the latest tracepoint hits. |
| |
| @item show circular-trace-buffer |
| @kindex show circular-trace-buffer |
| Show the current choice for the trace buffer. Note that this may not |
| match the agent's current buffer handling, nor is it guaranteed to |
| match the setting that might have been in effect during a past run, |
| for instance if you are looking at frames from a trace file. |
| |
| @end table |
| |
| @table @code |
| @item set trace-user @var{text} |
| @kindex set trace-user |
| |
| @item show trace-user |
| @kindex show trace-user |
| |
| @item set trace-notes @var{text} |
| @kindex set trace-notes |
| Set the trace run's notes. |
| |
| @item show trace-notes |
| @kindex show trace-notes |
| Show the trace run's notes. |
| |
| @item set trace-stop-notes @var{text} |
| @kindex set trace-stop-notes |
| Set the trace run's stop notes. The handling of the note is as for |
| @code{tstop} arguments; the set command is convenient way to fix a |
| stop note that is mistaken or incomplete. |
| |
| @item show trace-stop-notes |
| @kindex show trace-stop-notes |
| Show the trace run's stop notes. |
| |
| @end table |
| |
| @node Tracepoint Restrictions |
| @subsection Tracepoint Restrictions |
| |
| @cindex tracepoint restrictions |
| There are a number of restrictions on the use of tracepoints. As |
| described above, tracepoint data gathering occurs on the target |
| without interaction from @value{GDBN}. Thus the full capabilities of |
| the debugger are not available during data gathering, and then at data |
| examination time, you will be limited by only having what was |
| collected. The following items describe some common problems, but it |
| is not exhaustive, and you may run into additional difficulties not |
| mentioned here. |
| |
| @itemize @bullet |
| |
| @item |
| Tracepoint expressions are intended to gather objects (lvalues). Thus |
| the full flexibility of GDB's expression evaluator is not available. |
| You cannot call functions, cast objects to aggregate types, access |
| convenience variables or modify values (except by assignment to trace |
| state variables). Some language features may implicitly call |
| functions (for instance Objective-C fields with accessors), and therefore |
| cannot be collected either. |
| |
| @item |
| Collection of local variables, either individually or in bulk with |
| @code{$locals} or @code{$args}, during @code{while-stepping} may |
| behave erratically. The stepping action may enter a new scope (for |
| instance by stepping into a function), or the location of the variable |
| may change (for instance it is loaded into a register). The |
| tracepoint data recorded uses the location information for the |
| variables that is correct for the tracepoint location. When the |
| tracepoint is created, it is not possible, in general, to determine |
| where the steps of a @code{while-stepping} sequence will advance the |
| program---particularly if a conditional branch is stepped. |
| |
| @item |
| Collection of an incompletely-initialized or partially-destroyed object |
| may result in something that @value{GDBN} cannot display, or displays |
| in a misleading way. |
| |
| @item |
| When @value{GDBN} displays a pointer to character it automatically |
| dereferences the pointer to also display characters of the string |
| being pointed to. However, collecting the pointer during tracing does |
| not automatically collect the string. You need to explicitly |
| dereference the pointer and provide size information if you want to |
| collect not only the pointer, but the memory pointed to. For example, |
| @code{*ptr@@50} can be used to collect the 50 element array pointed to |
| by @code{ptr}. |
| |
| @item |
| It is not possible to collect a complete stack backtrace at a |
| tracepoint. Instead, you may collect the registers and a few hundred |
| bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300} |
| (adjust to use the name of the actual stack pointer register on your |
| target architecture, and the amount of stack you wish to capture). |
| Then the @code{backtrace} command will show a partial backtrace when |
| using a trace frame. The number of stack frames that can be examined |
| depends on the sizes of the frames in the collected stack. Note that |
| if you ask for a block so large that it goes past the bottom of the |
| stack, the target agent may report an error trying to read from an |
| invalid address. |
| |
| @item |
| If you do not collect registers at a tracepoint, @value{GDBN} can |
| infer that the value of @code{$pc} must be the same as the address of |
| the tracepoint and use that when you are looking at a trace frame |
| for that tracepoint. However, this cannot work if the tracepoint has |
| multiple locations (for instance if it was set in a function that was |
| inlined), or if it has a @code{while-stepping} loop. In those cases |
| @value{GDBN} will warn you that it can't infer @code{$pc}, and default |
| it to zero. |
| |
| @end itemize |
| |
| @node Analyze Collected Data |
| @section Using the Collected Data |
| |
| After the tracepoint experiment ends, you use @value{GDBN} commands |
| for examining the trace data. The basic idea is that each tracepoint |
| collects a trace @dfn{snapshot} every time it is hit and another |
| snapshot every time it single-steps. All these snapshots are |
| consecutively numbered from zero and go into a buffer, and you can |
| examine them later. The way you examine them is to @dfn{focus} on a |
| specific trace snapshot. When the remote stub is focused on a trace |
| snapshot, it will respond to all @value{GDBN} requests for memory and |
| registers by reading from the buffer which belongs to that snapshot, |
| rather than from @emph{real} memory or registers of the program being |
| debugged. This means that @strong{all} @value{GDBN} commands |
| (@code{print}, @code{info registers}, @code{backtrace}, etc.) will |
| behave as if we were currently debugging the program state as it was |
| when the tracepoint occurred. Any requests for data that are not in |
| the buffer will fail. |
| |
| @menu |
| * tfind:: How to select a trace snapshot |
| * tdump:: How to display all data for a snapshot |
| * save tracepoints:: How to save tracepoints for a future run |
| @end menu |
| |
| @node tfind |
| @subsection @code{tfind @var{n}} |
| |
| @kindex tfind |
| @cindex select trace snapshot |
| @cindex find trace snapshot |
| The basic command for selecting a trace snapshot from the buffer is |
| @code{tfind @var{n}}, which finds trace snapshot number @var{n}, |
| counting from zero. If no argument @var{n} is given, the next |
| snapshot is selected. |
| |
| Here are the various forms of using the @code{tfind} command. |
| |
| @table @code |
| @item tfind start |
| Find the first snapshot in the buffer. This is a synonym for |
| @code{tfind 0} (since 0 is the number of the first snapshot). |
| |
| @item tfind none |
| Stop debugging trace snapshots, resume @emph{live} debugging. |
| |
| @item tfind end |
| Same as @samp{tfind none}. |
| |
| @item tfind |
| No argument means find the next trace snapshot. |
| |
| @item tfind - |
| Find the previous trace snapshot before the current one. This permits |
| retracing earlier steps. |
| |
| @item tfind tracepoint @var{num} |
| Find the next snapshot associated with tracepoint @var{num}. Search |
| proceeds forward from the last examined trace snapshot. If no |
| argument @var{num} is given, it means find the next snapshot collected |
| for the same tracepoint as the current snapshot. |
| |
| @item tfind pc @var{addr} |
| Find the next snapshot associated with the value @var{addr} of the |
| program counter. Search proceeds forward from the last examined trace |
| snapshot. If no argument @var{addr} is given, it means find the next |
| snapshot with the same value of PC as the current snapshot. |
| |
| @item tfind outside @var{addr1}, @var{addr2} |
| Find the next snapshot whose PC is outside the given range of |
| addresses (exclusive). |
| |
| @item tfind range @var{addr1}, @var{addr2} |
| Find the next snapshot whose PC is between @var{addr1} and |
| @var{addr2} (inclusive). |
| |
| @item tfind line @r{[}@var{file}:@r{]}@var{n} |
| Find the next snapshot associated with the source line @var{n}. If |
| the optional argument @var{file} is given, refer to line @var{n} in |
| that source file. Search proceeds forward from the last examined |
| trace snapshot. If no argument @var{n} is given, it means find the |
| next line other than the one currently being examined; thus saying |
| @code{tfind line} repeatedly can appear to have the same effect as |
| stepping from line to line in a @emph{live} debugging session. |
| @end table |
| |
| The default arguments for the @code{tfind} commands are specifically |
| designed to make it easy to scan through the trace buffer. For |
| instance, @code{tfind} with no argument selects the next trace |
| snapshot, and @code{tfind -} with no argument selects the previous |
| trace snapshot. So, by giving one @code{tfind} command, and then |
| simply hitting @key{RET} repeatedly you can examine all the trace |
| snapshots in order. Or, by saying @code{tfind -} and then hitting |
| @key{RET} repeatedly you can examine the snapshots in reverse order. |
| The @code{tfind line} command with no argument selects the snapshot |
| for the next source line executed. The @code{tfind pc} command with |
| no argument selects the next snapshot with the same program counter |
| (PC) as the current frame. The @code{tfind tracepoint} command with |
| no argument selects the next trace snapshot collected by the same |
| tracepoint as the current one. |
| |
| In addition to letting you scan through the trace buffer manually, |
| these commands make it easy to construct @value{GDBN} scripts that |
| scan through the trace buffer and print out whatever collected data |
| you are interested in. Thus, if we want to examine the PC, FP, and SP |
| registers from each trace frame in the buffer, we can say this: |
| |
| @smallexample |
| (@value{GDBP}) @b{tfind start} |
| (@value{GDBP}) @b{while ($trace_frame != -1)} |
| > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \ |
| $trace_frame, $pc, $sp, $fp |
| > tfind |
| > end |
| |
| Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44 |
| Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44 |
| Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44 |
| Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44 |
| Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44 |
| Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44 |
| Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44 |
| Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44 |
| Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44 |
| Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44 |
| Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14 |
| @end smallexample |
| |
| Or, if we want to examine the variable @code{X} at each source line in |
| the buffer: |
| |
| @smallexample |
| (@value{GDBP}) @b{tfind start} |
| (@value{GDBP}) @b{while ($trace_frame != -1)} |
| > printf "Frame %d, X == %d\n", $trace_frame, X |
| > tfind line |
| > end |
| |
| Frame 0, X = 1 |
| Frame 7, X = 2 |
| Frame 13, X = 255 |
| @end smallexample |
| |
| @node tdump |
| @subsection @code{tdump} |
| @kindex tdump |
| @cindex dump all data collected at tracepoint |
| @cindex tracepoint data, display |
| |
| This command takes no arguments. It prints all the data collected at |
| the current trace snapshot. |
| |
| @smallexample |
| (@value{GDBP}) @b{trace 444} |
| (@value{GDBP}) @b{actions} |
| Enter actions for tracepoint #2, one per line: |
| > collect $regs, $locals, $args, gdb_long_test |
| > end |
| |
| (@value{GDBP}) @b{tstart} |
| |
| (@value{GDBP}) @b{tfind line 444} |
| #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66) |
| at gdb_test.c:444 |
| 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", ) |
| |
| (@value{GDBP}) @b{tdump} |
| Data collected at tracepoint 2, trace frame 1: |
| d0 0xc4aa0085 -995491707 |
| d1 0x18 24 |
| d2 0x80 128 |
| d3 0x33 51 |
| d4 0x71aea3d 119204413 |
| d5 0x22 34 |
| d6 0xe0 224 |
| d7 0x380035 3670069 |
| a0 0x19e24a 1696330 |
| a1 0x3000668 50333288 |
| a2 0x100 256 |
| a3 0x322000 3284992 |
| a4 0x3000698 50333336 |
| a5 0x1ad3cc 1758156 |
| fp 0x30bf3c 0x30bf3c |
| sp 0x30bf34 0x30bf34 |
| ps 0x0 0 |
| pc 0x20b2c8 0x20b2c8 |
| fpcontrol 0x0 0 |
| fpstatus 0x0 0 |
| fpiaddr 0x0 0 |
| p = 0x20e5b4 "gdb-test" |
| p1 = (void *) 0x11 |
| p2 = (void *) 0x22 |
| p3 = (void *) 0x33 |
| p4 = (void *) 0x44 |
| p5 = (void *) 0x55 |
| p6 = (void *) 0x66 |
| gdb_long_test = 17 '\021' |
| |
| (@value{GDBP}) |
| @end smallexample |
| |
| @code{tdump} works by scanning the tracepoint's current collection |
| actions and printing the value of each expression listed. So |
| @code{tdump} can fail, if after a run, you change the tracepoint's |
| actions to mention variables that were not collected during the run. |
| |
| Also, for tracepoints with @code{while-stepping} loops, @code{tdump} |
| uses the collected value of @code{$pc} to distinguish between trace |
| frames that were collected at the tracepoint hit, and frames that were |
| collected while stepping. This allows it to correctly choose whether |
| to display the basic list of collections, or the collections from the |
| body of the while-stepping loop. However, if @code{$pc} was not collected, |
| then @code{tdump} will always attempt to dump using the basic collection |
| list, and may fail if a while-stepping frame does not include all the |
| same data that is collected at the tracepoint hit. |
| @c This is getting pretty arcane, example would be good. |
| |
| @node save tracepoints |
| @subsection @code{save tracepoints @var{filename}} |
| @kindex save tracepoints |
| @kindex save-tracepoints |
| @cindex save tracepoints for future sessions |
| |
| This command saves all current tracepoint definitions together with |
| their actions and passcounts, into a file @file{@var{filename}} |
| suitable for use in a later debugging session. To read the saved |
| tracepoint definitions, use the @code{source} command (@pxref{Command |
| Files}). The @w{@code{save-tracepoints}} command is a deprecated |
| alias for @w{@code{save tracepoints}} |
| |
| @node Tracepoint Variables |
| @section Convenience Variables for Tracepoints |
| @cindex tracepoint variables |
| @cindex convenience variables for tracepoints |
| |
| @table @code |
| @vindex $trace_frame |
| @item (int) $trace_frame |
| The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no |
| snapshot is selected. |
| |
| @vindex $tracepoint |
| @item (int) $tracepoint |
| The tracepoint for the current trace snapshot. |
| |
| @vindex $trace_line |
| @item (int) $trace_line |
| The line number for the current trace snapshot. |
| |
| @vindex $trace_file |
| @item (char []) $trace_file |
| The source file for the current trace snapshot. |
| |
| @vindex $trace_func |
| @item (char []) $trace_func |
| The name of the function containing @code{$tracepoint}. |
| @end table |
| |
| Note: @code{$trace_file} is not suitable for use in @code{printf}, |
| use @code{output} instead. |
| |
| Here's a simple example of using these convenience variables for |
| stepping through all the trace snapshots and printing some of their |
| data. Note that these are not the same as trace state variables, |
| which are managed by the target. |
| |
| @smallexample |
| (@value{GDBP}) @b{tfind start} |
| |
| (@value{GDBP}) @b{while $trace_frame != -1} |
| > output $trace_file |
| > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint |
| > tfind |
| > end |
| @end smallexample |
| |
| @node Trace Files |
| @section Using Trace Files |
| @cindex trace files |
| |
| In some situations, the target running a trace experiment may no |
| longer be available; perhaps it crashed, or the hardware was needed |
| for a different activity. To handle these cases, you can arrange to |
| dump the trace data into a file, and later use that file as a source |
| of trace data, via the @code{target tfile} command. |
| |
| @table @code |
| |
| @kindex tsave |
| @item tsave [ -r ] @var{filename} |
| Save the trace data to @var{filename}. By default, this command |
| assumes that @var{filename} refers to the host filesystem, so if |
| necessary @value{GDBN} will copy raw trace data up from the target and |
| then save it. If the target supports it, you can also supply the |
| optional argument @code{-r} (``remote'') to direct the target to save |
| the data directly into @var{filename} in its own filesystem, which may be |
| more efficient if the trace buffer is very large. (Note, however, that |
| @code{target tfile} can only read from files accessible to the host.) |
| |
| @kindex target tfile |
| @kindex tfile |
| @item target tfile @var{filename} |
| Use the file named @var{filename} as a source of trace data. Commands |
| that examine data work as they do with a live target, but it is not |
| possible to run any new trace experiments. @code{tstatus} will report |
| the state of the trace run at the moment the data was saved, as well |
| as the current trace frame you are examining. @var{filename} must be |
| on a filesystem accessible to the host. |
| |
| @end table |
| |
| @node Overlays |
| @chapter Debugging Programs That Use Overlays |
| @cindex overlays |
| |
| If your program is too large to fit completely in your target system's |
| memory, you can sometimes use @dfn{overlays} to work around this |
| problem. @value{GDBN} provides some support for debugging programs that |
| use overlays. |
| |
| @menu |
| * How Overlays Work:: A general explanation of overlays. |
| * Overlay Commands:: Managing overlays in @value{GDBN}. |
| * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are |
| mapped by asking the inferior. |
| * Overlay Sample Program:: A sample program using overlays. |
| @end menu |
| |
| @node How Overlays Work |
| @section How Overlays Work |
| @cindex mapped overlays |
| @cindex unmapped overlays |
| @cindex load address, overlay's |
| @cindex mapped address |
| @cindex overlay area |
| |
| Suppose you have a computer whose instruction address space is only 64 |
| kilobytes long, but which has much more memory which can be accessed by |
| other means: special instructions, segment registers, or memory |
| management hardware, for example. Suppose further that you want to |
| adapt a program which is larger than 64 kilobytes to run on this system. |
| |
| One solution is to identify modules of your program which are relatively |
| independent, and need not call each other directly; call these modules |
| @dfn{overlays}. Separate the overlays from the main program, and place |
| their machine code in the larger memory. Place your main program in |
| instruction memory, but leave at least enough space there to hold the |
| largest overlay as well. |
| |
| Now, to call a function located in an overlay, you must first copy that |
| overlay's machine code from the large memory into the space set aside |
| for it in the instruction memory, and then jump to its entry point |
| there. |
| |
| @c NB: In the below the mapped area's size is greater or equal to the |
| @c size of all overlays. This is intentional to remind the developer |
| @c that overlays don't necessarily need to be the same size. |
| |
| @smallexample |
| @group |
| Data Instruction Larger |
| Address Space Address Space Address Space |
| +-----------+ +-----------+ +-----------+ |
| | | | | | | |
| +-----------+ +-----------+ +-----------+<-- overlay 1 |
| | program | | main | .----| overlay 1 | load address |
| | variables | | program | | +-----------+ |
| | and heap | | | | | | |
| +-----------+ | | | +-----------+<-- overlay 2 |
| | | +-----------+ | | | load address |
| +-----------+ | | | .-| overlay 2 | |
| | | | | | | |
| mapped --->+-----------+ | | +-----------+ |
| address | | | | | | |
| | overlay | <-' | | | |
| | area | <---' +-----------+<-- overlay 3 |
| | | <---. | | load address |
| +-----------+ `--| overlay 3 | |
| | | | | |
| +-----------+ | | |
| +-----------+ |
| | | |
| +-----------+ |
| |
| @anchor{A code overlay}A code overlay |
| @end group |
| @end smallexample |
| |
| The diagram (@pxref{A code overlay}) shows a system with separate data |
| and instruction address spaces. To map an overlay, the program copies |
| its code from the larger address space to the instruction address space. |
| Since the overlays shown here all use the same mapped address, only one |
| may be mapped at a time. For a system with a single address space for |
| data and instructions, the diagram would be similar, except that the |
| program variables and heap would share an address space with the main |
| program and the overlay area. |
| |
| An overlay loaded into instruction memory and ready for use is called a |
| @dfn{mapped} overlay; its @dfn{mapped address} is its address in the |
| instruction memory. An overlay not present (or only partially present) |
| in instruction memory is called @dfn{unmapped}; its @dfn{load address} |
| is its address in the larger memory. The mapped address is also called |
| the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also |
| called the @dfn{load memory address}, or @dfn{LMA}. |
| |
| Unfortunately, overlays are not a completely transparent way to adapt a |
| program to limited instruction memory. They introduce a new set of |
| global constraints you must keep in mind as you design your program: |
| |
| @itemize @bullet |
| |
| @item |
| Before calling or returning to a function in an overlay, your program |
| must make sure that overlay is actually mapped. Otherwise, the call or |
| return will transfer control to the right address, but in the wrong |
| overlay, and your program will probably crash. |
| |
| @item |
| If the process of mapping an overlay is expensive on your system, you |
| will need to choose your overlays carefully to minimize their effect on |
| your program's performance. |
| |
| @item |
| The executable file you load onto your system must contain each |
| overlay's instructions, appearing at the overlay's load address, not its |
| mapped address. However, each overlay's instructions must be relocated |
| and its symbols defined as if the overlay were at its mapped address. |
| You can use GNU linker scripts to specify different load and relocation |
| addresses for pieces of your program; see @ref{Overlay Description,,, |
| ld.info, Using ld: the GNU linker}. |
| |
| @item |
| The procedure for loading executable files onto your system must be able |
| to load their contents into the larger address space as well as the |
| instruction and data spaces. |
| |
| @end itemize |
| |
| The overlay system described above is rather simple, and could be |
| improved in many ways: |
| |
| @itemize @bullet |
| |
| @item |
| If your system has suitable bank switch registers or memory management |
| hardware, you could use those facilities to make an overlay's load area |
| contents simply appear at their mapped address in instruction space. |
| This would probably be faster than copying the overlay to its mapped |
| area in the usual way. |
| |
| @item |
| If your overlays are small enough, you could set aside more than one |
| overlay area, and have more than one overlay mapped at a time. |
| |
| @item |
| You can use overlays to manage data, as well as instructions. In |
| general, data overlays are even less transparent to your design than |
| code overlays: whereas code overlays only require care when you call or |
| return to functions, data overlays require care every time you access |
| the data. Also, if you change the contents of a data overlay, you |
| must copy its contents back out to its load address before you can copy a |
| different data overlay into the same mapped area. |
| |
| @end itemize |
| |
| |
| @node Overlay Commands |
| @section Overlay Commands |
| |
| To use @value{GDBN}'s overlay support, each overlay in your program must |
| correspond to a separate section of the executable file. The section's |
| virtual memory address and load memory address must be the overlay's |
| mapped and load addresses. Identifying overlays with sections allows |
| @value{GDBN} to determine the appropriate address of a function or |
| variable, depending on whether the overlay is mapped or not. |
| |
| @value{GDBN}'s overlay commands all start with the word @code{overlay}; |
| you can abbreviate this as @code{ov} or @code{ovly}. The commands are: |
| |
| @table @code |
| @item overlay off |
| @kindex overlay |
| Disable @value{GDBN}'s overlay support. When overlay support is |
| disabled, @value{GDBN} assumes that all functions and variables are |
| always present at their mapped addresses. By default, @value{GDBN}'s |
| overlay support is disabled. |
| |
| @item overlay manual |
| @cindex manual overlay debugging |
| Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN} |
| relies on you to tell it which overlays are mapped, and which are not, |
| using the @code{overlay map-overlay} and @code{overlay unmap-overlay} |
| commands described below. |
| |
| @item overlay map-overlay @var{overlay} |
| @itemx overlay map @var{overlay} |
| @cindex map an overlay |
| Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must |
| be the name of the object file section containing the overlay. When an |
| overlay is mapped, @value{GDBN} assumes it can find the overlay's |
| functions and variables at their mapped addresses. @value{GDBN} assumes |
| that any other overlays whose mapped ranges overlap that of |
| @var{overlay} are now unmapped. |
| |
| @item overlay unmap-overlay @var{overlay} |
| @itemx overlay unmap @var{overlay} |
| @cindex unmap an overlay |
| Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay} |
| must be the name of the object file section containing the overlay. |
| When an overlay is unmapped, @value{GDBN} assumes it can find the |
| overlay's functions and variables at their load addresses. |
| |
| @item overlay auto |
| Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN} |
| consults a data structure the overlay manager maintains in the inferior |
| to see which overlays are mapped. For details, see @ref{Automatic |
| Overlay Debugging}. |
| |
| @item overlay load-target |
| @itemx overlay load |
| @cindex reloading the overlay table |
| Re-read the overlay table from the inferior. Normally, @value{GDBN} |
| re-reads the table @value{GDBN} automatically each time the inferior |
| stops, so this command should only be necessary if you have changed the |
| overlay mapping yourself using @value{GDBN}. This command is only |
| useful when using automatic overlay debugging. |
| |
| @item overlay list-overlays |
| @itemx overlay list |
| @cindex listing mapped overlays |
| Display a list of the overlays currently mapped, along with their mapped |
| addresses, load addresses, and sizes. |
| |
| @end table |
| |
| Normally, when @value{GDBN} prints a code address, it includes the name |
| of the function the address falls in: |
| |
| @smallexample |
| (@value{GDBP}) print main |
| $3 = @{int ()@} 0x11a0 <main> |
| @end smallexample |
| @noindent |
| When overlay debugging is enabled, @value{GDBN} recognizes code in |
| unmapped overlays, and prints the names of unmapped functions with |
| asterisks around them. For example, if @code{foo} is a function in an |
| unmapped overlay, @value{GDBN} prints it this way: |
| |
| @smallexample |
| (@value{GDBP}) overlay list |
| No sections are mapped. |
| (@value{GDBP}) print foo |
| $5 = @{int (int)@} 0x100000 <*foo*> |
| @end smallexample |
| @noindent |
| When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's |
| name normally: |
| |
| @smallexample |
| (@value{GDBP}) overlay list |
| Section .ov.foo.text, loaded at 0x100000 - 0x100034, |
| mapped at 0x1016 - 0x104a |
| (@value{GDBP}) print foo |
| $6 = @{int (int)@} 0x1016 <foo> |
| @end smallexample |
| |
| When overlay debugging is enabled, @value{GDBN} can find the correct |
| address for functions and variables in an overlay, whether or not the |
| overlay is mapped. This allows most @value{GDBN} commands, like |
| @code{break} and @code{disassemble}, to work normally, even on unmapped |
| code. However, @value{GDBN}'s breakpoint support has some limitations: |
| |
| @itemize @bullet |
| @item |
| @cindex breakpoints in overlays |
| @cindex overlays, setting breakpoints in |
| You can set breakpoints in functions in unmapped overlays, as long as |
| @value{GDBN} can write to the overlay at its load address. |
| @item |
| @value{GDBN} can not set hardware or simulator-based breakpoints in |
| unmapped overlays. However, if you set a breakpoint at the end of your |
| overlay manager (and tell @value{GDBN} which overlays are now mapped, if |
| you are using manual overlay management), @value{GDBN} will re-set its |
| breakpoints properly. |
| @end itemize |
| |
| |
| @node Automatic Overlay Debugging |
| @section Automatic Overlay Debugging |
| @cindex automatic overlay debugging |
| |
| @value{GDBN} can automatically track which overlays are mapped and which |
| are not, given some simple co-operation from the overlay manager in the |
| inferior. If you enable automatic overlay debugging with the |
| @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN} |
| looks in the inferior's memory for certain variables describing the |
| current state of the overlays. |
| |
| Here are the variables your overlay manager must define to support |
| @value{GDBN}'s automatic overlay debugging: |
| |
| @table @asis |
| |
| @item @code{_ovly_table}: |
| This variable must be an array of the following structures: |
| |
| @smallexample |
| struct |
| @{ |
| /* The overlay's mapped address. */ |
| unsigned long vma; |
| |
| /* The size of the overlay, in bytes. */ |
| unsigned long size; |
| |
| /* The overlay's load address. */ |
| unsigned long lma; |
| |
| /* Non-zero if the overlay is currently mapped; |
| zero otherwise. */ |
| unsigned long mapped; |
| @} |
| @end smallexample |
| |
| @item @code{_novlys}: |
| This variable must be a four-byte signed integer, holding the total |
| number of elements in @code{_ovly_table}. |
| |
| @end table |
| |
| To decide whether a particular overlay is mapped or not, @value{GDBN} |
| looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and |
| @code{lma} members equal the VMA and LMA of the overlay's section in the |
| executable file. When @value{GDBN} finds a matching entry, it consults |
| the entry's @code{mapped} member to determine whether the overlay is |
| currently mapped. |
| |
| In addition, your overlay manager may define a function called |
| @code{_ovly_debug_event}. If this function is defined, @value{GDBN} |
| will silently set a breakpoint there. If the overlay manager then |
| calls this function whenever it has changed the overlay table, this |
| will enable @value{GDBN} to accurately keep track of which overlays |
| are in program memory, and update any breakpoints that may be set |
| in overlays. This will allow breakpoints to work even if the |
| overlays are kept in ROM or other non-writable memory while they |
| are not being executed. |
| |
| @node Overlay Sample Program |
| @section Overlay Sample Program |
| @cindex overlay example program |
| |
| When linking a program which uses overlays, you must place the overlays |
| at their load addresses, while relocating them to run at their mapped |
| addresses. To do this, you must write a linker script (@pxref{Overlay |
| Description,,, ld.info, Using ld: the GNU linker}). Unfortunately, |
| since linker scripts are specific to a particular host system, target |
| architecture, and target memory layout, this manual cannot provide |
| portable sample code demonstrating @value{GDBN}'s overlay support. |
| |
| However, the @value{GDBN} source distribution does contain an overlaid |
| program, with linker scripts for a few systems, as part of its test |
| suite. The program consists of the following files from |
| @file{gdb/testsuite/gdb.base}: |
| |
| @table @file |
| @item overlays.c |
| The main program file. |
| @item ovlymgr.c |
| A simple overlay manager, used by @file{overlays.c}. |
| @item foo.c |
| @itemx bar.c |
| @itemx baz.c |
| @itemx grbx.c |
| Overlay modules, loaded and used by @file{overlays.c}. |
| @item d10v.ld |
| @itemx m32r.ld |
| Linker scripts for linking the test program on the @code{d10v-elf} |
| and @code{m32r-elf} targets. |
| @end table |
| |
| You can build the test program using the @code{d10v-elf} GCC |
| cross-compiler like this: |
| |
| @smallexample |
| $ d10v-elf-gcc -g -c overlays.c |
| $ d10v-elf-gcc -g -c ovlymgr.c |
| $ d10v-elf-gcc -g -c foo.c |
| $ d10v-elf-gcc -g -c bar.c |
| $ d10v-elf-gcc -g -c baz.c |
| $ d10v-elf-gcc -g -c grbx.c |
| $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \ |
| baz.o grbx.o -Wl,-Td10v.ld -o overlays |
| @end smallexample |
| |
| The build process is identical for any other architecture, except that |
| you must substitute the appropriate compiler and linker script for the |
| target system for @code{d10v-elf-gcc} and @code{d10v.ld}. |
| |
| |
| @node Languages |
| @chapter Using @value{GDBN} with Different Languages |
| @cindex languages |
| |
| Although programming languages generally have common aspects, they are |
| rarely expressed in the same manner. For instance, in ANSI C, |
| dereferencing a pointer @code{p} is accomplished by @code{*p}, but in |
| Modula-2, it is accomplished by @code{p^}. Values can also be |
| represented (and displayed) differently. Hex numbers in C appear as |
| @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}. |
| |
| @cindex working language |
| Language-specific information is built into @value{GDBN} for some languages, |
| allowing you to express operations like the above in your program's |
| native language, and allowing @value{GDBN} to output values in a manner |
| consistent with the syntax of your program's native language. The |
| language you use to build expressions is called the @dfn{working |
| language}. |
| |
| @menu |
| * Setting:: Switching between source languages |
| * Show:: Displaying the language |
| * Checks:: Type and range checks |
| * Supported Languages:: Supported languages |
| * Unsupported Languages:: Unsupported languages |
| @end menu |
| |
| @node Setting |
| @section Switching Between Source Languages |
| |
| There are two ways to control the working language---either have @value{GDBN} |
| set it automatically, or select it manually yourself. You can use the |
| @code{set language} command for either purpose. On startup, @value{GDBN} |
| defaults to setting the language automatically. The working language is |
| used to determine how expressions you type are interpreted, how values |
| are printed, etc. |
| |
| In addition to the working language, every source file that |
| @value{GDBN} knows about has its own working language. For some object |
| file formats, the compiler might indicate which language a particular |
| source file is in. However, most of the time @value{GDBN} infers the |
| language from the name of the file. The language of a source file |
| controls whether C@t{++} names are demangled---this way @code{backtrace} can |
| show each frame appropriately for its own language. There is no way to |
| set the language of a source file from within @value{GDBN}, but you can |
| set the language associated with a filename extension. @xref{Show, , |
| Displaying the Language}. |
| |
| This is most commonly a problem when you use a program, such |
| as @code{cfront} or @code{f2c}, that generates C but is written in |
| another language. In that case, make the |
| program use @code{#line} directives in its C output; that way |
| @value{GDBN} will know the correct language of the source code of the original |
| program, and will display that source code, not the generated C code. |
| |
| @menu |
| * Filenames:: Filename extensions and languages. |
| * Manually:: Setting the working language manually |
| * Automatically:: Having @value{GDBN} infer the source language |
| @end menu |
| |
| @node Filenames |
| @subsection List of Filename Extensions and Languages |
| |
| If a source file name ends in one of the following extensions, then |
| @value{GDBN} infers that its language is the one indicated. |
| |
| @table @file |
| @item .ada |
| @itemx .ads |
| @itemx .adb |
| @itemx .a |
| Ada source file. |
| |
| @item .c |
| C source file |
| |
| @item .C |
| @itemx .cc |
| @itemx .cp |
| @itemx .cpp |
| @itemx .cxx |
| @itemx .c++ |
| C@t{++} source file |
| |
| @item .d |
| D source file |
| |
| @item .m |
| Objective-C source file |
| |
| @item .f |
| @itemx .F |
| Fortran source file |
| |
| @item .mod |
| Modula-2 source file |
| |
| @item .s |
| @itemx .S |
| Assembler source file. This actually behaves almost like C, but |
| @value{GDBN} does not skip over function prologues when stepping. |
| @end table |
| |
| In addition, you may set the language associated with a filename |
| extension. @xref{Show, , Displaying the Language}. |
| |
| @node Manually |
| @subsection Setting the Working Language |
| |
| If you allow @value{GDBN} to set the language automatically, |
| expressions are interpreted the same way in your debugging session and |
| your program. |
| |
| @kindex set language |
| If you wish, you may set the language manually. To do this, issue the |
| command @samp{set language @var{lang}}, where @var{lang} is the name of |
| a language, such as |
| @code{c} or @code{modula-2}. |
| For a list of the supported languages, type @samp{set language}. |
| |
| Setting the language manually prevents @value{GDBN} from updating the working |
| language automatically. This can lead to confusion if you try |
| to debug a program when the working language is not the same as the |
| source language, when an expression is acceptable to both |
| languages---but means different things. For instance, if the current |
| source file were written in C, and @value{GDBN} was parsing Modula-2, a |
| command such as: |
| |
| @smallexample |
| print a = b + c |
| @end smallexample |
| |
| @noindent |
| might not have the effect you intended. In C, this means to add |
| @code{b} and @code{c} and place the result in @code{a}. The result |
| printed would be the value of @code{a}. In Modula-2, this means to compare |
| @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value. |
| |
| @node Automatically |
| @subsection Having @value{GDBN} Infer the Source Language |
| |
| To have @value{GDBN} set the working language automatically, use |
| @samp{set language local} or @samp{set language auto}. @value{GDBN} |
| then infers the working language. That is, when your program stops in a |
| frame (usually by encountering a breakpoint), @value{GDBN} sets the |
| working language to the language recorded for the function in that |
| frame. If the language for a frame is unknown (that is, if the function |
| or block corresponding to the frame was defined in a source file that |
| does not have a recognized extension), the current working language is |
| not changed, and @value{GDBN} issues a warning. |
| |
| This may not seem necessary for most programs, which are written |
| entirely in one source language. However, program modules and libraries |
| written in one source language can be used by a main program written in |
| a different source language. Using @samp{set language auto} in this |
| case frees you from having to set the working language manually. |
| |
| @node Show |
| @section Displaying the Language |
| |
| The following commands help you find out which language is the |
| working language, and also what language source files were written in. |
| |
| @table @code |
| @item show language |
| @kindex show language |
| Display the current working language. This is the |
| language you can use with commands such as @code{print} to |
| build and compute expressions that may involve variables in your program. |
| |
| @item info frame |
| @kindex info frame@r{, show the source language} |
| Display the source language for this frame. This language becomes the |
| working language if you use an identifier from this frame. |
| @xref{Frame Info, ,Information about a Frame}, to identify the other |
| information listed here. |
| |
| @item info source |
| @kindex info source@r{, show the source language} |
| Display the source language of this source file. |
| @xref{Symbols, ,Examining the Symbol Table}, to identify the other |
| information listed here. |
| @end table |
| |
| In unusual circumstances, you may have source files with extensions |
| not in the standard list. You can then set the extension associated |
| with a language explicitly: |
| |
| @table @code |
| @item set extension-language @var{ext} @var{language} |
| @kindex set extension-language |
| Tell @value{GDBN} that source files with extension @var{ext} are to be |
| assumed as written in the source language @var{language}. |
| |
| @item info extensions |
| @kindex info extensions |
| List all the filename extensions and the associated languages. |
| @end table |
| |
| @node Checks |
| @section Type and Range Checking |
| |
| @quotation |
| @emph{Warning:} In this release, the @value{GDBN} commands for type and range |
| checking are included, but they do not yet have any effect. This |
| section documents the intended facilities. |
| @end quotation |
| @c FIXME remove warning when type/range code added |
| |
| Some languages are designed to guard you against making seemingly common |
| errors through a series of compile- and run-time checks. These include |
| checking the type of arguments to functions and operators, and making |
| sure mathematical overflows are caught at run time. Checks such as |
| these help to ensure a program's correctness once it has been compiled |
| by eliminating type mismatches, and providing active checks for range |
| errors when your program is running. |
| |
| @value{GDBN} can check for conditions like the above if you wish. |
| Although @value{GDBN} does not check the statements in your program, |
| it can check expressions entered directly into @value{GDBN} for |
| evaluation via the @code{print} command, for example. As with the |
| working language, @value{GDBN} can also decide whether or not to check |
| automatically based on your program's source language. |
| @xref{Supported Languages, ,Supported Languages}, for the default |
| settings of supported languages. |
| |
| @menu |
| * Type Checking:: An overview of type checking |
| * Range Checking:: An overview of range checking |
| @end menu |
| |
| @cindex type checking |
| @cindex checks, type |
| @node Type Checking |
| @subsection An Overview of Type Checking |
| |
| Some languages, such as Modula-2, are strongly typed, meaning that the |
| arguments to operators and functions have to be of the correct type, |
| otherwise an error occurs. These checks prevent type mismatch |
| errors from ever causing any run-time problems. For example, |
| |
| @smallexample |
| 1 + 2 @result{} 3 |
| @exdent but |
| @error{} 1 + 2.3 |
| @end smallexample |
| |
| The second example fails because the @code{CARDINAL} 1 is not |
| type-compatible with the @code{REAL} 2.3. |
| |
| For the expressions you use in @value{GDBN} commands, you can tell the |
| @value{GDBN} type checker to skip checking; |
| to treat any mismatches as errors and abandon the expression; |
| or to only issue warnings when type mismatches occur, |
| but evaluate the expression anyway. When you choose the last of |
| these, @value{GDBN} evaluates expressions like the second example above, but |
| also issues a warning. |
| |
| Even if you turn type checking off, there may be other reasons |
| related to type that prevent @value{GDBN} from evaluating an expression. |
| For instance, @value{GDBN} does not know how to add an @code{int} and |
| a @code{struct foo}. These particular type errors have nothing to do |
| with the language in use, and usually arise from expressions, such as |
| the one described above, which make little sense to evaluate anyway. |
| |
| Each language defines to what degree it is strict about type. For |
| instance, both Modula-2 and C require the arguments to arithmetical |
| operators to be numbers. In C, enumerated types and pointers can be |
| represented as numbers, so that they are valid arguments to mathematical |
| operators. @xref{Supported Languages, ,Supported Languages}, for further |
| details on specific languages. |
| |
| @value{GDBN} provides some additional commands for controlling the type checker: |
| |
| @kindex set check type |
| @kindex show check type |
| @table @code |
| @item set check type auto |
| Set type checking on or off based on the current working language. |
| @xref{Supported Languages, ,Supported Languages}, for the default settings for |
| each language. |
| |
| @item set check type on |
| @itemx set check type off |
| Set type checking on or off, overriding the default setting for the |
| current working language. Issue a warning if the setting does not |
| match the language default. If any type mismatches occur in |
| evaluating an expression while type checking is on, @value{GDBN} prints a |
| message and aborts evaluation of the expression. |
| |
| @item set check type warn |
| Cause the type checker to issue warnings, but to always attempt to |
| evaluate the expression. Evaluating the expression may still |
| be impossible for other reasons. For example, @value{GDBN} cannot add |
| numbers and structures. |
| |
| @item show type |
| Show the current setting of the type checker, and whether or not @value{GDBN} |
| is setting it automatically. |
| @end table |
| |
| @cindex range checking |
| @cindex checks, range |
| @node Range Checking |
| @subsection An Overview of Range Checking |
| |
| In some languages (such as Modula-2), it is an error to exceed the |
| bounds of a type; this is enforced with run-time checks. Such range |
| checking is meant to ensure program correctness by making sure |
| computations do not overflow, or indices on an array element access do |
| not exceed the bounds of the array. |
| |
| For expressions you use in @value{GDBN} commands, you can tell |
| @value{GDBN} to treat range errors in one of three ways: ignore them, |
| always treat them as errors and abandon the expression, or issue |
| warnings but evaluate the expression anyway. |
| |
| A range error can result from numerical overflow, from exceeding an |
| array index bound, or when you type a constant that is not a member |
| of any type. Some languages, however, do not treat overflows as an |
| error. In many implementations of C, mathematical overflow causes the |
| result to ``wrap around'' to lower values---for example, if @var{m} is |
| the largest integer value, and @var{s} is the smallest, then |
| |
| @smallexample |
| @var{m} + 1 @result{} @var{s} |
| @end smallexample |
| |
| This, too, is specific to individual languages, and in some cases |
| specific to individual compilers or machines. @xref{Supported Languages, , |
| Supported Languages}, for further details on specific languages. |
| |
| @value{GDBN} provides some additional commands for controlling the range checker: |
| |
| @kindex set check range |
| @kindex show check range |
| @table @code |
| @item set check range auto |
| Set range checking on or off based on the current working language. |
| @xref{Supported Languages, ,Supported Languages}, for the default settings for |
| each language. |
| |
| @item set check range on |
| @itemx set check range off |
| Set range checking on or off, overriding the default setting for the |
| current working language. A warning is issued if the setting does not |
| match the language default. If a range error occurs and range checking is on, |
| then a message is printed and evaluation of the expression is aborted. |
| |
| @item set check range warn |
| Output messages when the @value{GDBN} range checker detects a range error, |
| but attempt to evaluate the expression anyway. Evaluating the |
| expression may still be impossible for other reasons, such as accessing |
| memory that the process does not own (a typical example from many Unix |
| systems). |
| |
| @item show range |
| Show the current setting of the range checker, and whether or not it is |
| being set automatically by @value{GDBN}. |
| @end table |
| |
| @node Supported Languages |
| @section Supported Languages |
| |
| @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java, |
| OpenCL C, Pascal, assembly, Modula-2, and Ada. |
| @c This is false ... |
| Some @value{GDBN} features may be used in expressions regardless of the |
| language you use: the @value{GDBN} @code{@@} and @code{::} operators, |
| and the @samp{@{type@}addr} construct (@pxref{Expressions, |
| ,Expressions}) can be used with the constructs of any supported |
| language. |
| |
| The following sections detail to what degree each source language is |
| supported by @value{GDBN}. These sections are not meant to be language |
| tutorials or references, but serve only as a reference guide to what the |
| @value{GDBN} expression parser accepts, and what input and output |
| formats should look like for different languages. There are many good |
| books written on each of these languages; please look to these for a |
| language reference or tutorial. |
| |
| @menu |
| * C:: C and C@t{++} |
| * D:: D |
| * Go:: Go |
| * Objective-C:: Objective-C |
| * OpenCL C:: OpenCL C |
| * Fortran:: Fortran |
| * Pascal:: Pascal |
| * Modula-2:: Modula-2 |
| * Ada:: Ada |
| @end menu |
| |
| @node C |
| @subsection C and C@t{++} |
| |
| @cindex C and C@t{++} |
| @cindex expressions in C or C@t{++} |
| |
| Since C and C@t{++} are so closely related, many features of @value{GDBN} apply |
| to both languages. Whenever this is the case, we discuss those languages |
| together. |
| |
| @cindex C@t{++} |
| @cindex @code{g++}, @sc{gnu} C@t{++} compiler |
| @cindex @sc{gnu} C@t{++} |
| The C@t{++} debugging facilities are jointly implemented by the C@t{++} |
| compiler and @value{GDBN}. Therefore, to debug your C@t{++} code |
| effectively, you must compile your C@t{++} programs with a supported |
| C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++} |
| compiler (@code{aCC}). |
| |
| @menu |
| * C Operators:: C and C@t{++} operators |
| * C Constants:: C and C@t{++} constants |
| * C Plus Plus Expressions:: C@t{++} expressions |
| * C Defaults:: Default settings for C and C@t{++} |
| * C Checks:: C and C@t{++} type and range checks |
| * Debugging C:: @value{GDBN} and C |
| * Debugging C Plus Plus:: @value{GDBN} features for C@t{++} |
| * Decimal Floating Point:: Numbers in Decimal Floating Point format |
| @end menu |
| |
| @node C Operators |
| @subsubsection C and C@t{++} Operators |
| |
| @cindex C and C@t{++} operators |
| |
| Operators must be defined on values of specific types. For instance, |
| @code{+} is defined on numbers, but not on structures. Operators are |
| often defined on groups of types. |
| |
| For the purposes of C and C@t{++}, the following definitions hold: |
| |
| @itemize @bullet |
| |
| @item |
| @emph{Integral types} include @code{int} with any of its storage-class |
| specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}. |
| |
| @item |
| @emph{Floating-point types} include @code{float}, @code{double}, and |
| @code{long double} (if supported by the target platform). |
| |
| @item |
| @emph{Pointer types} include all types defined as @code{(@var{type} *)}. |
| |
| @item |
| @emph{Scalar types} include all of the above. |
| |
| @end itemize |
| |
| @noindent |
| The following operators are supported. They are listed here |
| in order of increasing precedence: |
| |
| @table @code |
| @item , |
| The comma or sequencing operator. Expressions in a comma-separated list |
| are evaluated from left to right, with the result of the entire |
| expression being the last expression evaluated. |
| |
| @item = |
| Assignment. The value of an assignment expression is the value |
| assigned. Defined on scalar types. |
| |
| @item @var{op}= |
| Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}}, |
| and translated to @w{@code{@var{a} = @var{a op b}}}. |
| @w{@code{@var{op}=}} and @code{=} have the same precedence. |
| @var{op} is any one of the operators @code{|}, @code{^}, @code{&}, |
| @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}. |
| |
| @item ?: |
| The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought |
| of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an |
| integral type. |
| |
| @item || |
| Logical @sc{or}. Defined on integral types. |
| |
| @item && |
| Logical @sc{and}. Defined on integral types. |
| |
| @item | |
| Bitwise @sc{or}. Defined on integral types. |
| |
| @item ^ |
| Bitwise exclusive-@sc{or}. Defined on integral types. |
| |
| @item & |
| Bitwise @sc{and}. Defined on integral types. |
| |
| @item ==@r{, }!= |
| Equality and inequality. Defined on scalar types. The value of these |
| expressions is 0 for false and non-zero for true. |
| |
| @item <@r{, }>@r{, }<=@r{, }>= |
| Less than, greater than, less than or equal, greater than or equal. |
| Defined on scalar types. The value of these expressions is 0 for false |
| and non-zero for true. |
| |
| @item <<@r{, }>> |
| left shift, and right shift. Defined on integral types. |
| |
| @item @@ |
| The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). |
| |
| @item +@r{, }- |
| Addition and subtraction. Defined on integral types, floating-point types and |
| pointer types. |
| |
| @item *@r{, }/@r{, }% |
| Multiplication, division, and modulus. Multiplication and division are |
| defined on integral and floating-point types. Modulus is defined on |
| integral types. |
| |
| @item ++@r{, }-- |
| Increment and decrement. When appearing before a variable, the |
| operation is performed before the variable is used in an expression; |
| when appearing after it, the variable's value is used before the |
| operation takes place. |
| |
| @item * |
| Pointer dereferencing. Defined on pointer types. Same precedence as |
| @code{++}. |
| |
| @item & |
| Address operator. Defined on variables. Same precedence as @code{++}. |
| |
| For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is |
| allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})} |
| to examine the address |
| where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is |
| stored. |
| |
| @item - |
| Negative. Defined on integral and floating-point types. Same |
| precedence as @code{++}. |
| |
| @item ! |
| Logical negation. Defined on integral types. Same precedence as |
| @code{++}. |
| |
| @item ~ |
| Bitwise complement operator. Defined on integral types. Same precedence as |
| @code{++}. |
| |
| |
| @item .@r{, }-> |
| Structure member, and pointer-to-structure member. For convenience, |
| @value{GDBN} regards the two as equivalent, choosing whether to dereference a |
| pointer based on the stored type information. |
| Defined on @code{struct} and @code{union} data. |
| |
| @item .*@r{, }->* |
| Dereferences of pointers to members. |
| |
| @item [] |
| Array indexing. @code{@var{a}[@var{i}]} is defined as |
| @code{*(@var{a}+@var{i})}. Same precedence as @code{->}. |
| |
| @item () |
| Function parameter list. Same precedence as @code{->}. |
| |
| @item :: |
| C@t{++} scope resolution operator. Defined on @code{struct}, @code{union}, |
| and @code{class} types. |
| |
| @item :: |
| Doubled colons also represent the @value{GDBN} scope operator |
| (@pxref{Expressions, ,Expressions}). Same precedence as @code{::}, |
| above. |
| @end table |
| |
| If an operator is redefined in the user code, @value{GDBN} usually |
| attempts to invoke the redefined version instead of using the operator's |
| predefined meaning. |
| |
| @node C Constants |
| @subsubsection C and C@t{++} Constants |
| |
| @cindex C and C@t{++} constants |
| |
| @value{GDBN} allows you to express the constants of C and C@t{++} in the |
| following ways: |
| |
| @itemize @bullet |
| @item |
| Integer constants are a sequence of digits. Octal constants are |
| specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants |
| by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter |
| @samp{l}, specifying that the constant should be treated as a |
| @code{long} value. |
| |
| @item |
| Floating point constants are a sequence of digits, followed by a decimal |
| point, followed by a sequence of digits, and optionally followed by an |
| exponent. An exponent is of the form: |
| @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another |
| sequence of digits. The @samp{+} is optional for positive exponents. |
| A floating-point constant may also end with a letter @samp{f} or |
| @samp{F}, specifying that the constant should be treated as being of |
| the @code{float} (as opposed to the default @code{double}) type; or with |
| a letter @samp{l} or @samp{L}, which specifies a @code{long double} |
| constant. |
| |
| @item |
| Enumerated constants consist of enumerated identifiers, or their |
| integral equivalents. |
| |
| @item |
| Character constants are a single character surrounded by single quotes |
| (@code{'}), or a number---the ordinal value of the corresponding character |
| (usually its @sc{ascii} value). Within quotes, the single character may |
| be represented by a letter or by @dfn{escape sequences}, which are of |
| the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation |
| of the character's ordinal value; or of the form @samp{\@var{x}}, where |
| @samp{@var{x}} is a predefined special character---for example, |
| @samp{\n} for newline. |
| |
| Wide character constants can be written by prefixing a character |
| constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide |
| form of @samp{x}. The target wide character set is used when |
| computing the value of this constant (@pxref{Character Sets}). |
| |
| @item |
| String constants are a sequence of character constants surrounded by |
| double quotes (@code{"}). Any valid character constant (as described |
| above) may appear. Double quotes within the string must be preceded by |
| a backslash, so for instance @samp{"a\"b'c"} is a string of five |
| characters. |
| |
| Wide string constants can be written by prefixing a string constant |
| with @samp{L}, as in C. The target wide character set is used when |
| computing the value of this constant (@pxref{Character Sets}). |
| |
| @item |
| Pointer constants are an integral value. You can also write pointers |
| to constants using the C operator @samp{&}. |
| |
| @item |
| Array constants are comma-separated lists surrounded by braces @samp{@{} |
| and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of |
| integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array, |
| and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers. |
| @end itemize |
| |
| @node C Plus Plus Expressions |
| @subsubsection C@t{++} Expressions |
| |
| @cindex expressions in C@t{++} |
| @value{GDBN} expression handling can interpret most C@t{++} expressions. |
| |
| @cindex debugging C@t{++} programs |
| @cindex C@t{++} compilers |
| @cindex debug formats and C@t{++} |
| @cindex @value{NGCC} and C@t{++} |
| @quotation |
| @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use |
| the proper compiler and the proper debug format. Currently, |
| @value{GDBN} works best when debugging C@t{++} code that is compiled |
| with the most recent version of @value{NGCC} possible. The DWARF |
| debugging format is preferred; @value{NGCC} defaults to this on most |
| popular platforms. Other compilers and/or debug formats are likely to |
| work badly or not at all when using @value{GDBN} to debug C@t{++} |
| code. @xref{Compilation}. |
| @end quotation |
| |
| @enumerate |
| |
| @cindex member functions |
| @item |
| Member function calls are allowed; you can use expressions like |
| |
| @smallexample |
| count = aml->GetOriginal(x, y) |
| @end smallexample |
| |
| @vindex this@r{, inside C@t{++} member functions} |
| @cindex namespace in C@t{++} |
| @item |
| While a member function is active (in the selected stack frame), your |
| expressions have the same namespace available as the member function; |
| that is, @value{GDBN} allows implicit references to the class instance |
| pointer @code{this} following the same rules as C@t{++}. @code{using} |
| declarations in the current scope are also respected by @value{GDBN}. |
| |
| @cindex call overloaded functions |
| @cindex overloaded functions, calling |
| @cindex type conversions in C@t{++} |
| @item |
| You can call overloaded functions; @value{GDBN} resolves the function |
| call to the right definition, with some restrictions. @value{GDBN} does not |
| perform overload resolution involving user-defined type conversions, |
| calls to constructors, or instantiations of templates that do not exist |
| in the program. It also cannot handle ellipsis argument lists or |
| default arguments. |
| |
| It does perform integral conversions and promotions, floating-point |
| promotions, arithmetic conversions, pointer conversions, conversions of |
| class objects to base classes, and standard conversions such as those of |
| functions or arrays to pointers; it requires an exact match on the |
| number of function arguments. |
| |
| Overload resolution is always performed, unless you have specified |
| @code{set overload-resolution off}. @xref{Debugging C Plus Plus, |
| ,@value{GDBN} Features for C@t{++}}. |
| |
| You must specify @code{set overload-resolution off} in order to use an |
| explicit function signature to call an overloaded function, as in |
| @smallexample |
| p 'foo(char,int)'('x', 13) |
| @end smallexample |
| |
| The @value{GDBN} command-completion facility can simplify this; |
| see @ref{Completion, ,Command Completion}. |
| |
| @cindex reference declarations |
| @item |
| @value{GDBN} understands variables declared as C@t{++} references; you can use |
| them in expressions just as you do in C@t{++} source---they are automatically |
| dereferenced. |
| |
| In the parameter list shown when @value{GDBN} displays a frame, the values of |
| reference variables are not displayed (unlike other variables); this |
| avoids clutter, since references are often used for large structures. |
| The @emph{address} of a reference variable is always shown, unless |
| you have specified @samp{set print address off}. |
| |
| @item |
| @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your |
| expressions can use it just as expressions in your program do. Since |
| one scope may be defined in another, you can use @code{::} repeatedly if |
| necessary, for example in an expression like |
| @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows |
| resolving name scope by reference to source files, in both C and C@t{++} |
| debugging (@pxref{Variables, ,Program Variables}). |
| |
| @item |
| @value{GDBN} performs argument-dependent lookup, following the C@t{++} |
| specification. |
| @end enumerate |
| |
| @node C Defaults |
| @subsubsection C and C@t{++} Defaults |
| |
| @cindex C and C@t{++} defaults |
| |
| If you allow @value{GDBN} to set type and range checking automatically, they |
| both default to @code{off} whenever the working language changes to |
| C or C@t{++}. This happens regardless of whether you or @value{GDBN} |
| selects the working language. |
| |
| If you allow @value{GDBN} to set the language automatically, it |
| recognizes source files whose names end with @file{.c}, @file{.C}, or |
| @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of |
| these files, it sets the working language to C or C@t{++}. |
| @xref{Automatically, ,Having @value{GDBN} Infer the Source Language}, |
| for further details. |
| |
| @c Type checking is (a) primarily motivated by Modula-2, and (b) |
| @c unimplemented. If (b) changes, it might make sense to let this node |
| @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93. |
| |
| @node C Checks |
| @subsubsection C and C@t{++} Type and Range Checks |
| |
| @cindex C and C@t{++} checks |
| |
| By default, when @value{GDBN} parses C or C@t{++} expressions, type checking |
| is not used. However, if you turn type checking on, @value{GDBN} |
| considers two variables type equivalent if: |
| |
| @itemize @bullet |
| @item |
| The two variables are structured and have the same structure, union, or |
| enumerated tag. |
| |
| @item |
| The two variables have the same type name, or types that have been |
| declared equivalent through @code{typedef}. |
| |
| @ignore |
| @c leaving this out because neither J Gilmore nor R Pesch understand it. |
| @c FIXME--beers? |
| @item |
| The two @code{struct}, @code{union}, or @code{enum} variables are |
| declared in the same declaration. (Note: this may not be true for all C |
| compilers.) |
| @end ignore |
| @end itemize |
| |
| Range checking, if turned on, is done on mathematical operations. Array |
| indices are not checked, since they are often used to index a pointer |
| that is not itself an array. |
| |
| @node Debugging C |
| @subsubsection @value{GDBN} and C |
| |
| The @code{set print union} and @code{show print union} commands apply to |
| the @code{union} type. When set to @samp{on}, any @code{union} that is |
| inside a @code{struct} or @code{class} is also printed. Otherwise, it |
| appears as @samp{@{...@}}. |
| |
| The @code{@@} operator aids in the debugging of dynamic arrays, formed |
| with pointers and a memory allocation function. @xref{Expressions, |
| ,Expressions}. |
| |
| @node Debugging C Plus Plus |
| @subsubsection @value{GDBN} Features for C@t{++} |
| |
| @cindex commands for C@t{++} |
| |
| Some @value{GDBN} commands are particularly useful with C@t{++}, and some are |
| designed specifically for use with C@t{++}. Here is a summary: |
| |
| @table @code |
| @cindex break in overloaded functions |
| @item @r{breakpoint menus} |
| When you want a breakpoint in a function whose name is overloaded, |
| @value{GDBN} has the capability to display a menu of possible breakpoint |
| locations to help you specify which function definition you want. |
| @xref{Ambiguous Expressions,,Ambiguous Expressions}. |
| |
| @cindex overloading in C@t{++} |
| @item rbreak @var{regex} |
| Setting breakpoints using regular expressions is helpful for setting |
| breakpoints on overloaded functions that are not members of any special |
| classes. |
| @xref{Set Breaks, ,Setting Breakpoints}. |
| |
| @cindex C@t{++} exception handling |
| @item catch throw |
| @itemx catch catch |
| Debug C@t{++} exception handling using these commands. @xref{Set |
| Catchpoints, , Setting Catchpoints}. |
| |
| @cindex inheritance |
| @item ptype @var{typename} |
| Print inheritance relationships as well as other information for type |
| @var{typename}. |
| @xref{Symbols, ,Examining the Symbol Table}. |
| |
| @item info vtbl @var{expression}. |
| The @code{info vtbl} command can be used to display the virtual |
| method tables of the object computed by @var{expression}. This shows |
| one entry per virtual table; there may be multiple virtual tables when |
| multiple inheritance is in use. |
| |
| @cindex C@t{++} symbol display |
| @item set print demangle |
| @itemx show print demangle |
| @itemx set print asm-demangle |
| @itemx show print asm-demangle |
| Control whether C@t{++} symbols display in their source form, both when |
| displaying code as C@t{++} source and when displaying disassemblies. |
| @xref{Print Settings, ,Print Settings}. |
| |
| @item set print object |
| @itemx show print object |
| Choose whether to print derived (actual) or declared types of objects. |
| @xref{Print Settings, ,Print Settings}. |
| |
| @item set print vtbl |
| @itemx show print vtbl |
| Control the format for printing virtual function tables. |
| @xref{Print Settings, ,Print Settings}. |
| (The @code{vtbl} commands do not work on programs compiled with the HP |
| ANSI C@t{++} compiler (@code{aCC}).) |
| |
| @kindex set overload-resolution |
| @cindex overloaded functions, overload resolution |
| @item set overload-resolution on |
| Enable overload resolution for C@t{++} expression evaluation. The default |
| is on. For overloaded functions, @value{GDBN} evaluates the arguments |
| and searches for a function whose signature matches the argument types, |
| using the standard C@t{++} conversion rules (see @ref{C Plus Plus |
| Expressions, ,C@t{++} Expressions}, for details). |
| If it cannot find a match, it emits a message. |
| |
| @item set overload-resolution off |
| Disable overload resolution for C@t{++} expression evaluation. For |
| overloaded functions that are not class member functions, @value{GDBN} |
| chooses the first function of the specified name that it finds in the |
| symbol table, whether or not its arguments are of the correct type. For |
| overloaded functions that are class member functions, @value{GDBN} |
| searches for a function whose signature @emph{exactly} matches the |
| argument types. |
| |
| @kindex show overload-resolution |
| @item show overload-resolution |
| Show the current setting of overload resolution. |
| |
| @item @r{Overloaded symbol names} |
| You can specify a particular definition of an overloaded symbol, using |
| the same notation that is used to declare such symbols in C@t{++}: type |
| @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can |
| also use the @value{GDBN} command-line word completion facilities to list the |
| available choices, or to finish the type list for you. |
| @xref{Completion,, Command Completion}, for details on how to do this. |
| @end table |
| |
| @node Decimal Floating Point |
| @subsubsection Decimal Floating Point format |
| @cindex decimal floating point format |
| |
| @value{GDBN} can examine, set and perform computations with numbers in |
| decimal floating point format, which in the C language correspond to the |
| @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as |
| specified by the extension to support decimal floating-point arithmetic. |
| |
| There are two encodings in use, depending on the architecture: BID (Binary |
| Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for |
| PowerPC. @value{GDBN} will use the appropriate encoding for the configured |
| target. |
| |
| Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN} |
| to manipulate decimal floating point numbers, it is not possible to convert |
| (using a cast, for example) integers wider than 32-bit to decimal float. |
| |
| In addition, in order to imitate @value{GDBN}'s behaviour with binary floating |
| point computations, error checking in decimal float operations ignores |
| underflow, overflow and divide by zero exceptions. |
| |
| In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers |
| to inspect @code{_Decimal128} values stored in floating point registers. |
| See @ref{PowerPC,,PowerPC} for more details. |
| |
| @node D |
| @subsection D |
| |
| @cindex D |
| @value{GDBN} can be used to debug programs written in D and compiled with |
| GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D |
| specific feature --- dynamic arrays. |
| |
| @node Go |
| @subsection Go |
| |
| @cindex Go (programming language) |
| @value{GDBN} can be used to debug programs written in Go and compiled with |
| @file{gccgo} or @file{6g} compilers. |
| |
| Here is a summary of the Go-specific features and restrictions: |
| |
| @table @code |
| @cindex current Go package |
| @item The current Go package |
| The name of the current package does not need to be specified when |
| specifying global variables and functions. |
| |
| For example, given the program: |
| |
| @example |
| package main |
| var myglob = "Shall we?" |
| func main () @{ |
| // ... |
| @} |
| @end example |
| |
| When stopped inside @code{main} either of these work: |
| |
| @example |
| (gdb) p myglob |
| (gdb) p main.myglob |
| @end example |
| |
| @cindex builtin Go types |
| @item Builtin Go types |
| The @code{string} type is recognized by @value{GDBN} and is printed |
| as a string. |
| |
| @cindex builtin Go functions |
| @item Builtin Go functions |
| The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof} |
| function and handles it internally. |
| |
| @cindex restrictions on Go expressions |
| @item Restrictions on Go expressions |
| All Go operators are supported except @code{&^}. |
| The Go @code{_} ``blank identifier'' is not supported. |
| Automatic dereferencing of pointers is not supported. |
| @end table |
| |
| @node Objective-C |
| @subsection Objective-C |
| |
| @cindex Objective-C |
| This section provides information about some commands and command |
| options that are useful for debugging Objective-C code. See also |
| @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a |
| few more commands specific to Objective-C support. |
| |
| @menu |
| * Method Names in Commands:: |
| * The Print Command with Objective-C:: |
| @end menu |
| |
| @node Method Names in Commands |
| @subsubsection Method Names in Commands |
| |
| The following commands have been extended to accept Objective-C method |
| names as line specifications: |
| |
| @kindex clear@r{, and Objective-C} |
| @kindex break@r{, and Objective-C} |
| @kindex info line@r{, and Objective-C} |
| @kindex jump@r{, and Objective-C} |
| @kindex list@r{, and Objective-C} |
| @itemize |
| @item @code{clear} |
| @item @code{break} |
| @item @code{info line} |
| @item @code{jump} |
| @item @code{list} |
| @end itemize |
| |
| A fully qualified Objective-C method name is specified as |
| |
| @smallexample |
| -[@var{Class} @var{methodName}] |
| @end smallexample |
| |
| where the minus sign is used to indicate an instance method and a |
| plus sign (not shown) is used to indicate a class method. The class |
| name @var{Class} and method name @var{methodName} are enclosed in |
| brackets, similar to the way messages are specified in Objective-C |
| source code. For example, to set a breakpoint at the @code{create} |
| instance method of class @code{Fruit} in the program currently being |
| debugged, enter: |
| |
| @smallexample |
| break -[Fruit create] |
| @end smallexample |
| |
| To list ten program lines around the @code{initialize} class method, |
| enter: |
| |
| @smallexample |
| list +[NSText initialize] |
| @end smallexample |
| |
| In the current version of @value{GDBN}, the plus or minus sign is |
| required. In future versions of @value{GDBN}, the plus or minus |
| sign will be optional, but you can use it to narrow the search. It |
| is also possible to specify just a method name: |
| |
| @smallexample |
| break create |
| @end smallexample |
| |
| You must specify the complete method name, including any colons. If |
| your program's source files contain more than one @code{create} method, |
| you'll be presented with a numbered list of classes that implement that |
| method. Indicate your choice by number, or type @samp{0} to exit if |
| none apply. |
| |
| As another example, to clear a breakpoint established at the |
| @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter: |
| |
| @smallexample |
| clear -[NSWindow makeKeyAndOrderFront:] |
| @end smallexample |
| |
| @node The Print Command with Objective-C |
| @subsubsection The Print Command With Objective-C |
| @cindex Objective-C, print objects |
| @kindex print-object |
| @kindex po @r{(@code{print-object})} |
| |
| The print command has also been extended to accept methods. For example: |
| |
| @smallexample |
| print -[@var{object} hash] |
| @end smallexample |
| |
| @cindex print an Objective-C object description |
| @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects |
| @noindent |
| will tell @value{GDBN} to send the @code{hash} message to @var{object} |
| and print the result. Also, an additional command has been added, |
| @code{print-object} or @code{po} for short, which is meant to print |
| the description of an object. However, this command may only work |
| with certain Objective-C libraries that have a particular hook |
| function, @code{_NSPrintForDebugger}, defined. |
| |
| @node OpenCL C |
| @subsection OpenCL C |
| |
| @cindex OpenCL C |
| This section provides information about @value{GDBN}s OpenCL C support. |
| |
| @menu |
| * OpenCL C Datatypes:: |
| * OpenCL C Expressions:: |
| * OpenCL C Operators:: |
| @end menu |
| |
| @node OpenCL C Datatypes |
| @subsubsection OpenCL C Datatypes |
| |
| @cindex OpenCL C Datatypes |
| @value{GDBN} supports the builtin scalar and vector datatypes specified |
| by OpenCL 1.1. In addition the half- and double-precision floating point |
| data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL |
| extensions are also known to @value{GDBN}. |
| |
| @node OpenCL C Expressions |
| @subsubsection OpenCL C Expressions |
| |
| @cindex OpenCL C Expressions |
| @value{GDBN} supports accesses to vector components including the access as |
| lvalue where possible. Since OpenCL C is based on C99 most C expressions |
| supported by @value{GDBN} can be used as well. |
| |
| @node OpenCL C Operators |
| @subsubsection OpenCL C Operators |
| |
| @cindex OpenCL C Operators |
| @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and |
| vector data types. |
| |
| @node Fortran |
| @subsection Fortran |
| @cindex Fortran-specific support in @value{GDBN} |
| |
| @value{GDBN} can be used to debug programs written in Fortran, but it |
| currently supports only the features of Fortran 77 language. |
| |
| @cindex trailing underscore, in Fortran symbols |
| Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers |
| among them) append an underscore to the names of variables and |
| functions. When you debug programs compiled by those compilers, you |
| will need to refer to variables and functions with a trailing |
| underscore. |
| |
| @menu |
| * Fortran Operators:: Fortran operators and expressions |
| * Fortran Defaults:: Default settings for Fortran |
| * Special Fortran Commands:: Special @value{GDBN} commands for Fortran |
| @end menu |
| |
| @node Fortran Operators |
| @subsubsection Fortran Operators and Expressions |
| |
| @cindex Fortran operators and expressions |
| |
| Operators must be defined on values of specific types. For instance, |
| @code{+} is defined on numbers, but not on characters or other non- |
| arithmetic types. Operators are often defined on groups of types. |
| |
| @table @code |
| @item ** |
| The exponentiation operator. It raises the first operand to the power |
| of the second one. |
| |
| @item : |
| The range operator. Normally used in the form of array(low:high) to |
| represent a section of array. |
| |
| @item % |
| The access component operator. Normally used to access elements in derived |
| types. Also suitable for unions. As unions aren't part of regular Fortran, |
| this can only happen when accessing a register that uses a gdbarch-defined |
| union type. |
| @end table |
| |
| @node Fortran Defaults |
| @subsubsection Fortran Defaults |
| |
| @cindex Fortran Defaults |
| |
| Fortran symbols are usually case-insensitive, so @value{GDBN} by |
| default uses case-insensitive matches for Fortran symbols. You can |
| change that with the @samp{set case-insensitive} command, see |
| @ref{Symbols}, for the details. |
| |
| @node Special Fortran Commands |
| @subsubsection Special Fortran Commands |
| |
| @cindex Special Fortran commands |
| |
| @value{GDBN} has some commands to support Fortran-specific features, |
| such as displaying common blocks. |
| |
| @table @code |
| @cindex @code{COMMON} blocks, Fortran |
| @kindex info common |
| @item info common @r{[}@var{common-name}@r{]} |
| This command prints the values contained in the Fortran @code{COMMON} |
| block whose name is @var{common-name}. With no argument, the names of |
| all @code{COMMON} blocks visible at the current program location are |
| printed. |
| @end table |
| |
| @node Pascal |
| @subsection Pascal |
| |
| @cindex Pascal support in @value{GDBN}, limitations |
| Debugging Pascal programs which use sets, subranges, file variables, or |
| nested functions does not currently work. @value{GDBN} does not support |
| entering expressions, printing values, or similar features using Pascal |
| syntax. |
| |
| The Pascal-specific command @code{set print pascal_static-members} |
| controls whether static members of Pascal objects are displayed. |
| @xref{Print Settings, pascal_static-members}. |
| |
| @node Modula-2 |
| @subsection Modula-2 |
| |
| @cindex Modula-2, @value{GDBN} support |
| |
| The extensions made to @value{GDBN} to support Modula-2 only support |
| output from the @sc{gnu} Modula-2 compiler (which is currently being |
| developed). Other Modula-2 compilers are not currently supported, and |
| attempting to debug executables produced by them is most likely |
| to give an error as @value{GDBN} reads in the executable's symbol |
| table. |
| |
| @cindex expressions in Modula-2 |
| @menu |
| * M2 Operators:: Built-in operators |
| * Built-In Func/Proc:: Built-in functions and procedures |
| * M2 Constants:: Modula-2 constants |
| * M2 Types:: Modula-2 types |
| * M2 Defaults:: Default settings for Modula-2 |
| * Deviations:: Deviations from standard Modula-2 |
| * M2 Checks:: Modula-2 type and range checks |
| * M2 Scope:: The scope operators @code{::} and @code{.} |
| * GDB/M2:: @value{GDBN} and Modula-2 |
| @end menu |
| |
| @node M2 Operators |
| @subsubsection Operators |
| @cindex Modula-2 operators |
| |
| Operators must be defined on values of specific types. For instance, |
| @code{+} is defined on numbers, but not on structures. Operators are |
| often defined on groups of types. For the purposes of Modula-2, the |
| following definitions hold: |
| |
| @itemize @bullet |
| |
| @item |
| @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and |
| their subranges. |
| |
| @item |
| @emph{Character types} consist of @code{CHAR} and its subranges. |
| |
| @item |
| @emph{Floating-point types} consist of @code{REAL}. |
| |
| @item |
| @emph{Pointer types} consist of anything declared as @code{POINTER TO |
| @var{type}}. |
| |
| @item |
| @emph{Scalar types} consist of all of the above. |
| |
| @item |
| @emph{Set types} consist of @code{SET} and @code{BITSET} types. |
| |
| @item |
| @emph{Boolean types} consist of @code{BOOLEAN}. |
| @end itemize |
| |
| @noindent |
| The following operators are supported, and appear in order of |
| increasing precedence: |
| |
| @table @code |
| @item , |
| Function argument or array index separator. |
| |
| @item := |
| Assignment. The value of @var{var} @code{:=} @var{value} is |
| @var{value}. |
| |
| @item <@r{, }> |
| Less than, greater than on integral, floating-point, or enumerated |
| types. |
| |
| @item <=@r{, }>= |
| Less than or equal to, greater than or equal to |
| on integral, floating-point and enumerated types, or set inclusion on |
| set types. Same precedence as @code{<}. |
| |
| @item =@r{, }<>@r{, }# |
| Equality and two ways of expressing inequality, valid on scalar types. |
| Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is |
| available for inequality, since @code{#} conflicts with the script |
| comment character. |
| |
| @item IN |
| Set membership. Defined on set types and the types of their members. |
| Same precedence as @code{<}. |
| |
| @item OR |
| Boolean disjunction. Defined on boolean types. |
| |
| @item AND@r{, }& |
| Boolean conjunction. Defined on boolean types. |
| |
| @item @@ |
| The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}). |
| |
| @item +@r{, }- |
| Addition and subtraction on integral and floating-point types, or union |
| and difference on set types. |
| |
| @item * |
| Multiplication on integral and floating-point types, or set intersection |
| on set types. |
| |
| @item / |
| Division on floating-point types, or symmetric set difference on set |
| types. Same precedence as @code{*}. |
| |
| @item DIV@r{, }MOD |
| Integer division and remainder. Defined on integral types. Same |
| precedence as @code{*}. |
| |
| @item - |
| Negative. Defined on @code{INTEGER} and @code{REAL} data. |
| |
| @item ^ |
| Pointer dereferencing. Defined on pointer types. |
| |
| @item NOT |
| Boolean negation. Defined on boolean types. Same precedence as |
| @code{^}. |
| |
| @item . |
| @code{RECORD} field selector. Defined on @code{RECORD} data. Same |
| precedence as @code{^}. |
| |
| @item [] |
| Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}. |
| |
| @item () |
| Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence |
| as @code{^}. |
| |
| @item ::@r{, }. |
| @value{GDBN} and Modula-2 scope operators. |
| @end table |
| |
| @quotation |
| @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN} |
| treats the use of the operator @code{IN}, or the use of operators |
| @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#}, |
| @code{<=}, and @code{>=} on sets as an error. |
| @end quotation |
| |
| |
| @node Built-In Func/Proc |
| @subsubsection Built-in Functions and Procedures |
| @cindex Modula-2 built-ins |
| |
| Modula-2 also makes available several built-in procedures and functions. |
| In describing these, the following metavariables are used: |
| |
| @table @var |
| |
| @item a |
| represents an @code{ARRAY} variable. |
| |
| @item c |
| represents a @code{CHAR} constant or variable. |
| |
| @item i |
| represents a variable or constant of integral type. |
| |
| @item m |
| represents an identifier that belongs to a set. Generally used in the |
| same function with the metavariable @var{s}. The type of @var{s} should |
| be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}). |
| |
| @item n |
| represents a variable or constant of integral or floating-point type. |
| |
| @item r |
| represents a variable or constant of floating-point type. |
| |
| @item t |
| represents a type. |
| |
| @item v |
| represents a variable. |
| |
| @item x |
| represents a variable or constant of one of many types. See the |
| explanation of the function for details. |
| @end table |
| |
| All Modula-2 built-in procedures also return a result, described below. |
| |
| @table @code |
| @item ABS(@var{n}) |
| Returns the absolute value of @var{n}. |
| |
| @item CAP(@var{c}) |
| If @var{c} is a lower case letter, it returns its upper case |
| equivalent, otherwise it returns its argument. |
| |
| @item CHR(@var{i}) |
| Returns the character whose ordinal value is @var{i}. |
| |
| @item DEC(@var{v}) |
| Decrements the value in the variable @var{v} by one. Returns the new value. |
| |
| @item DEC(@var{v},@var{i}) |
| Decrements the value in the variable @var{v} by @var{i}. Returns the |
| new value. |
| |
| @item EXCL(@var{m},@var{s}) |
| Removes the element @var{m} from the set @var{s}. Returns the new |
| set. |
| |
| @item FLOAT(@var{i}) |
| Returns the floating point equivalent of the integer @var{i}. |
| |
| @item HIGH(@var{a}) |
| Returns the index of the last member of @var{a}. |
| |
| @item INC(@var{v}) |
| Increments the value in the variable @var{v} by one. Returns the new value. |
| |
| @item INC(@var{v},@var{i}) |
| Increments the value in the variable @var{v} by @var{i}. Returns the |
| new value. |
| |
| @item INCL(@var{m},@var{s}) |
| Adds the element @var{m} to the set @var{s} if it is not already |
| there. Returns the new set. |
| |
| @item MAX(@var{t}) |
| Returns the maximum value of the type @var{t}. |
| |
| @item MIN(@var{t}) |
| Returns the minimum value of the type @var{t}. |
| |
| @item ODD(@var{i}) |
| Returns boolean TRUE if @var{i} is an odd number. |
| |
| @item ORD(@var{x}) |
| Returns the ordinal value of its argument. For example, the ordinal |
| value of a character is its @sc{ascii} value (on machines supporting the |
| @sc{ascii} character set). @var{x} must be of an ordered type, which include |
| integral, character and enumerated types. |
| |
| @item SIZE(@var{x}) |
| Returns the size of its argument. @var{x} can be a variable or a type. |
| |
| @item TRUNC(@var{r}) |
| Returns the integral part of @var{r}. |
| |
| @item TSIZE(@var{x}) |
| Returns the size of its argument. @var{x} can be a variable or a type. |
| |
| @item VAL(@var{t},@var{i}) |
| Returns the member of the type @var{t} whose ordinal value is @var{i}. |
| @end table |
| |
| @quotation |
| @emph{Warning:} Sets and their operations are not yet supported, so |
| @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as |
| an error. |
| @end quotation |
| |
| @cindex Modula-2 constants |
| @node M2 Constants |
| @subsubsection Constants |
| |
| @value{GDBN} allows you to express the constants of Modula-2 in the following |
| ways: |
| |
| @itemize @bullet |
| |
| @item |
| Integer constants are simply a sequence of digits. When used in an |
| expression, a constant is interpreted to be type-compatible with the |
| rest of the expression. Hexadecimal integers are specified by a |
| trailing @samp{H}, and octal integers by a trailing @samp{B}. |
| |
| @item |
| Floating point constants appear as a sequence of digits, followed by a |
| decimal point and another sequence of digits. An optional exponent can |
| then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where |
| @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the |
| digits of the floating point constant must be valid decimal (base 10) |
| digits. |
| |
| @item |
| Character constants consist of a single character enclosed by a pair of |
| like quotes, either single (@code{'}) or double (@code{"}). They may |
| also be expressed by their ordinal value (their @sc{ascii} value, usually) |
| followed by a @samp{C}. |
| |
| @item |
| String constants consist of a sequence of characters enclosed by a |
| pair of like quotes, either single (@code{'}) or double (@code{"}). |
| Escape sequences in the style of C are also allowed. @xref{C |
| Constants, ,C and C@t{++} Constants}, for a brief explanation of escape |
| sequences. |
| |
| @item |
| Enumerated constants consist of an enumerated identifier. |
| |
| @item |
| Boolean constants consist of the identifiers @code{TRUE} and |
| @code{FALSE}. |
| |
| @item |
| Pointer constants consist of integral values only. |
| |
| @item |
| Set constants are not yet supported. |
| @end itemize |
| |
| @node M2 Types |
| @subsubsection Modula-2 Types |
| @cindex Modula-2 types |
| |
| Currently @value{GDBN} can print the following data types in Modula-2 |
| syntax: array types, record types, set types, pointer types, procedure |
| types, enumerated types, subrange types and base types. You can also |
| print the contents of variables declared using these type. |
| This section gives a number of simple source code examples together with |
| sample @value{GDBN} sessions. |
| |
| The first example contains the following section of code: |
| |
| @smallexample |
| VAR |
| s: SET OF CHAR ; |
| r: [20..40] ; |
| @end smallexample |
| |
| @noindent |
| and you can request @value{GDBN} to interrogate the type and value of |
| @code{r} and @code{s}. |
| |
| @smallexample |
| (@value{GDBP}) print s |
| @{'A'..'C', 'Z'@} |
| (@value{GDBP}) ptype s |
| SET OF CHAR |
| (@value{GDBP}) print r |
| 21 |
| (@value{GDBP}) ptype r |
| [20..40] |
| @end smallexample |
| |
| @noindent |
| Likewise if your source code declares @code{s} as: |
| |
| @smallexample |
| VAR |
| s: SET ['A'..'Z'] ; |
| @end smallexample |
| |
| @noindent |
| then you may query the type of @code{s} by: |
| |
| @smallexample |
| (@value{GDBP}) ptype s |
| type = SET ['A'..'Z'] |
| @end smallexample |
| |
| @noindent |
| Note that at present you cannot interactively manipulate set |
| expressions using the debugger. |
| |
| The following example shows how you might declare an array in Modula-2 |
| and how you can interact with @value{GDBN} to print its type and contents: |
| |
| @smallexample |
| VAR |
| s: ARRAY [-10..10] OF CHAR ; |
| @end smallexample |
| |
| @smallexample |
| (@value{GDBP}) ptype s |
| ARRAY [-10..10] OF CHAR |
| @end smallexample |
| |
| Note that the array handling is not yet complete and although the type |
| is printed correctly, expression handling still assumes that all |
| arrays have a lower bound of zero and not @code{-10} as in the example |
| above. |
| |
| Here are some more type related Modula-2 examples: |
| |
| @smallexample |
| TYPE |
| colour = (blue, red, yellow, green) ; |
| t = [blue..yellow] ; |
| VAR |
| s: t ; |
| BEGIN |
| s := blue ; |
| @end smallexample |
| |
| @noindent |
| The @value{GDBN} interaction shows how you can query the data type |
| and value of a variable. |
| |
| @smallexample |
| (@value{GDBP}) print s |
| $1 = blue |
| (@value{GDBP}) ptype t |
| type = [blue..yellow] |
| @end smallexample |
| |
| @noindent |
| In this example a Modula-2 array is declared and its contents |
| displayed. Observe that the contents are written in the same way as |
| their @code{C} counterparts. |
| |
| @smallexample |
| VAR |
| s: ARRAY [1..5] OF CARDINAL ; |
| BEGIN |
| s[1] := 1 ; |
| @end smallexample |
| |
| @smallexample |
| (@value{GDBP}) print s |
| $1 = @{1, 0, 0, 0, 0@} |
| (@value{GDBP}) ptype s |
| type = ARRAY [1..5] OF CARDINAL |
| @end smallexample |
| |
| The Modula-2 language interface to @value{GDBN} also understands |
| pointer types as shown in this example: |
| |
| @smallexample |
| VAR |
| s: POINTER TO ARRAY [1..5] OF CARDINAL ; |
| BEGIN |
| NEW(s) ; |
| s^[1] := 1 ; |
| @end smallexample |
| |
| @noindent |
| and you can request that @value{GDBN} describes the type of @code{s}. |
| |
| @smallexample |
| (@value{GDBP}) ptype s |
| type = POINTER TO ARRAY [1..5] OF CARDINAL |
| @end smallexample |
| |
| @value{GDBN} handles compound types as we can see in this example. |
| Here we combine array types, record types, pointer types and subrange |
| types: |
| |
| @smallexample |
| TYPE |
| foo = RECORD |
| f1: CARDINAL ; |
| f2: CHAR ; |
| f3: myarray ; |
| END ; |
| |
| myarray = ARRAY myrange OF CARDINAL ; |
| myrange = [-2..2] ; |
| VAR |
| s: POINTER TO ARRAY myrange OF foo ; |
| @end smallexample |
| |
| @noindent |
| and you can ask @value{GDBN} to describe the type of @code{s} as shown |
| below. |
| |
| @smallexample |
| (@value{GDBP}) ptype s |
| type = POINTER TO ARRAY [-2..2] OF foo = RECORD |
| f1 : CARDINAL; |
| f2 : CHAR; |
| f3 : ARRAY [-2..2] OF CARDINAL; |
| END |
| @end smallexample |
| |
| @node M2 Defaults |
| @subsubsection Modula-2 Defaults |
| @cindex Modula-2 defaults |
| |
| If type and range checking are set automatically by @value{GDBN}, they |
| both default to @code{on} whenever the working language changes to |
| Modula-2. This happens regardless of whether you or @value{GDBN} |
| selected the working language. |
| |
| If you allow @value{GDBN} to set the language automatically, then entering |
| code compiled from a file whose name ends with @file{.mod} sets the |
| working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} |
| Infer the Source Language}, for further details. |
| |
| @node Deviations |
| @subsubsection Deviations from Standard Modula-2 |
| @cindex Modula-2, deviations from |
| |
| A few changes have been made to make Modula-2 programs easier to debug. |
| This is done primarily via loosening its type strictness: |
| |
| @itemize @bullet |
| @item |
| Unlike in standard Modula-2, pointer constants can be formed by |
| integers. This allows you to modify pointer variables during |
| debugging. (In standard Modula-2, the actual address contained in a |
| pointer variable is hidden from you; it can only be modified |
| through direct assignment to another pointer variable or expression that |
| returned a pointer.) |
| |
| @item |
| C escape sequences can be used in strings and characters to represent |
| non-printable characters. @value{GDBN} prints out strings with these |
| escape sequences embedded. Single non-printable characters are |
| printed using the @samp{CHR(@var{nnn})} format. |
| |
| @item |
| The assignment operator (@code{:=}) returns the value of its right-hand |
| argument. |
| |
| @item |
| All built-in procedures both modify @emph{and} return their argument. |
| @end itemize |
| |
| @node M2 Checks |
| @subsubsection Modula-2 Type and Range Checks |
| @cindex Modula-2 checks |
| |
| @quotation |
| @emph{Warning:} in this release, @value{GDBN} does not yet perform type or |
| range checking. |
| @end quotation |
| @c FIXME remove warning when type/range checks added |
| |
| @value{GDBN} considers two Modula-2 variables type equivalent if: |
| |
| @itemize @bullet |
| @item |
| They are of types that have been declared equivalent via a @code{TYPE |
| @var{t1} = @var{t2}} statement |
| |
| @item |
| They have been declared on the same line. (Note: This is true of the |
| @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.) |
| @end itemize |
| |
| As long as type checking is enabled, any attempt to combine variables |
| whose types are not equivalent is an error. |
| |
| Range checking is done on all mathematical operations, assignment, array |
| index bounds, and all built-in functions and procedures. |
| |
| @node M2 Scope |
| @subsubsection The Scope Operators @code{::} and @code{.} |
| @cindex scope |
| @cindex @code{.}, Modula-2 scope operator |
| @cindex colon, doubled as scope operator |
| @ifinfo |
| @vindex colon-colon@r{, in Modula-2} |
| @c Info cannot handle :: but TeX can. |
| @end ifinfo |
| @ifnotinfo |
| @vindex ::@r{, in Modula-2} |
| @end ifnotinfo |
| |
| There are a few subtle differences between the Modula-2 scope operator |
| (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have |
| similar syntax: |
| |
| @smallexample |
| |
| @var{module} . @var{id} |
| @var{scope} :: @var{id} |
| @end smallexample |
| |
| @noindent |
| where @var{scope} is the name of a module or a procedure, |
| @var{module} the name of a module, and @var{id} is any declared |
| identifier within your program, except another module. |
| |
| Using the @code{::} operator makes @value{GDBN} search the scope |
| specified by @var{scope} for the identifier @var{id}. If it is not |
| found in the specified scope, then @value{GDBN} searches all scopes |
| enclosing the one specified by @var{scope}. |
| |
| Using the @code{.} operator makes @value{GDBN} search the current scope for |
| the identifier specified by @var{id} that was imported from the |
| definition module specified by @var{module}. With this operator, it is |
| an error if the identifier @var{id} was not imported from definition |
| module @var{module}, or if @var{id} is not an identifier in |
| @var{module}. |
| |
| @node GDB/M2 |
| @subsubsection @value{GDBN} and Modula-2 |
| |
| Some @value{GDBN} commands have little use when debugging Modula-2 programs. |
| Five subcommands of @code{set print} and @code{show print} apply |
| specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle}, |
| @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four |
| apply to C@t{++}, and the last to the C @code{union} type, which has no direct |
| analogue in Modula-2. |
| |
| The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available |
| with any language, is not useful with Modula-2. Its |
| intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be |
| created in Modula-2 as they can in C or C@t{++}. However, because an |
| address can be specified by an integral constant, the construct |
| @samp{@{@var{type}@}@var{adrexp}} is still useful. |
| |
| @cindex @code{#} in Modula-2 |
| In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is |
| interpreted as the beginning of a comment. Use @code{<>} instead. |
| |
| @node Ada |
| @subsection Ada |
| @cindex Ada |
| |
| The extensions made to @value{GDBN} for Ada only support |
| output from the @sc{gnu} Ada (GNAT) compiler. |
| Other Ada compilers are not currently supported, and |
| attempting to debug executables produced by them is most likely |
| to be difficult. |
| |
| |
| @cindex expressions in Ada |
| @menu |
| * Ada Mode Intro:: General remarks on the Ada syntax |
| and semantics supported by Ada mode |
| in @value{GDBN}. |
| * Omissions from Ada:: Restrictions on the Ada expression syntax. |
| * Additions to Ada:: Extensions of the Ada expression syntax. |
| * Stopping Before Main Program:: Debugging the program during elaboration. |
| * Ada Tasks:: Listing and setting breakpoints in tasks. |
| * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files |
| * Ravenscar Profile:: Tasking Support when using the Ravenscar |
| Profile |
| * Ada Glitches:: Known peculiarities of Ada mode. |
| @end menu |
| |
| @node Ada Mode Intro |
| @subsubsection Introduction |
| @cindex Ada mode, general |
| |
| The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression |
| syntax, with some extensions. |
| The philosophy behind the design of this subset is |
| |
| @itemize @bullet |
| @item |
| That @value{GDBN} should provide basic literals and access to operations for |
| arithmetic, dereferencing, field selection, indexing, and subprogram calls, |
| leaving more sophisticated computations to subprograms written into the |
| program (which therefore may be called from @value{GDBN}). |
| |
| @item |
| That type safety and strict adherence to Ada language restrictions |
| are not particularly important to the @value{GDBN} user. |
| |
| @item |
| That brevity is important to the @value{GDBN} user. |
| @end itemize |
| |
| Thus, for brevity, the debugger acts as if all names declared in |
| user-written packages are directly visible, even if they are not visible |
| according to Ada rules, thus making it unnecessary to fully qualify most |
| names with their packages, regardless of context. Where this causes |
| ambiguity, @value{GDBN} asks the user's intent. |
| |
| The debugger will start in Ada mode if it detects an Ada main program. |
| As for other languages, it will enter Ada mode when stopped in a program that |
| was translated from an Ada source file. |
| |
| While in Ada mode, you may use `@t{--}' for comments. This is useful |
| mostly for documenting command files. The standard @value{GDBN} comment |
| (@samp{#}) still works at the beginning of a line in Ada mode, but not in the |
| middle (to allow based literals). |
| |
| The debugger supports limited overloading. Given a subprogram call in which |
| the function symbol has multiple definitions, it will use the number of |
| actual parameters and some information about their types to attempt to narrow |
| the set of definitions. It also makes very limited use of context, preferring |
| procedures to functions in the context of the @code{call} command, and |
| functions to procedures elsewhere. |
| |
| @node Omissions from Ada |
| @subsubsection Omissions from Ada |
| @cindex Ada, omissions from |
| |
| Here are the notable omissions from the subset: |
| |
| @itemize @bullet |
| @item |
| Only a subset of the attributes are supported: |
| |
| @itemize @minus |
| @item |
| @t{'First}, @t{'Last}, and @t{'Length} |
| on array objects (not on types and subtypes). |
| |
| @item |
| @t{'Min} and @t{'Max}. |
| |
| @item |
| @t{'Pos} and @t{'Val}. |
| |
| @item |
| @t{'Tag}. |
| |
| @item |
| @t{'Range} on array objects (not subtypes), but only as the right |
| operand of the membership (@code{in}) operator. |
| |
| @item |
| @t{'Access}, @t{'Unchecked_Access}, and |
| @t{'Unrestricted_Access} (a GNAT extension). |
| |
| @item |
| @t{'Address}. |
| @end itemize |
| |
| @item |
| The names in |
| @code{Characters.Latin_1} are not available and |
| concatenation is not implemented. Thus, escape characters in strings are |
| not currently available. |
| |
| @item |
| Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise |
| equality of representations. They will generally work correctly |
| for strings and arrays whose elements have integer or enumeration types. |
| They may not work correctly for arrays whose element |
| types have user-defined equality, for arrays of real values |
| (in particular, IEEE-conformant floating point, because of negative |
| zeroes and NaNs), and for arrays whose elements contain unused bits with |
| indeterminate values. |
| |
| @item |
| The other component-by-component array operations (@code{and}, @code{or}, |
| @code{xor}, @code{not}, and relational tests other than equality) |
| are not implemented. |
| |
| @item |
| @cindex array aggregates (Ada) |
| @cindex record aggregates (Ada) |
| @cindex aggregates (Ada) |
| There is limited support for array and record aggregates. They are |
| permitted only on the right sides of assignments, as in these examples: |
| |
| @smallexample |
| (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6) |
| (@value{GDBP}) set An_Array := (1, others => 0) |
| (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6) |
| (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9)) |
| (@value{GDBP}) set A_Record := (1, "Peter", True); |
| (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True) |
| @end smallexample |
| |
| Changing a |
| discriminant's value by assigning an aggregate has an |
| undefined effect if that discriminant is used within the record. |
| However, you can first modify discriminants by directly assigning to |
| them (which normally would not be allowed in Ada), and then performing an |
| aggregate assignment. For example, given a variable @code{A_Rec} |
| declared to have a type such as: |
| |
| @smallexample |
| type Rec (Len : Small_Integer := 0) is record |
| Id : Integer; |
| Vals : IntArray (1 .. Len); |
| end record; |
| @end smallexample |
| |
| you can assign a value with a different size of @code{Vals} with two |
| assignments: |
| |
| @smallexample |
| (@value{GDBP}) set A_Rec.Len := 4 |
| (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4)) |
| @end smallexample |
| |
| As this example also illustrates, @value{GDBN} is very loose about the usual |
| rules concerning aggregates. You may leave out some of the |
| components of an array or record aggregate (such as the @code{Len} |
| component in the assignment to @code{A_Rec} above); they will retain their |
| original values upon assignment. You may freely use dynamic values as |
| indices in component associations. You may even use overlapping or |
| redundant component associations, although which component values are |
| assigned in such cases is not defined. |
| |
| @item |
| Calls to dispatching subprograms are not implemented. |
| |
| @item |
| The overloading algorithm is much more limited (i.e., less selective) |
| than that of real Ada. It makes only limited use of the context in |
| which a subexpression appears to resolve its meaning, and it is much |
| looser in its rules for allowing type matches. As a result, some |
| function calls will be ambiguous, and the user will be asked to choose |
| the proper resolution. |
| |
| @item |
| The @code{new} operator is not implemented. |
| |
| @item |
| Entry calls are not implemented. |
| |
| @item |
| Aside from printing, arithmetic operations on the native VAX floating-point |
| formats are not supported. |
| |
| @item |
| It is not possible to slice a packed array. |
| |
| @item |
| The names @code{True} and @code{False}, when not part of a qualified name, |
| are interpreted as if implicitly prefixed by @code{Standard}, regardless of |
| context. |
| Should your program |
| redefine these names in a package or procedure (at best a dubious practice), |
| you will have to use fully qualified names to access their new definitions. |
| @end itemize |
| |
| @node Additions to Ada |
| @subsubsection Additions to Ada |
| @cindex Ada, deviations from |
| |
| As it does for other languages, @value{GDBN} makes certain generic |
| extensions to Ada (@pxref{Expressions}): |
| |
| @itemize @bullet |
| @item |
| If the expression @var{E} is a variable residing in memory (typically |
| a local variable or array element) and @var{N} is a positive integer, |
| then @code{@var{E}@@@var{N}} displays the values of @var{E} and the |
| @var{N}-1 adjacent variables following it in memory as an array. In |
| Ada, this operator is generally not necessary, since its prime use is |
| in displaying parts of an array, and slicing will usually do this in |
| Ada. However, there are occasional uses when debugging programs in |
| which certain debugging information has been optimized away. |
| |
| @item |
| @code{@var{B}::@var{var}} means ``the variable named @var{var} that |
| appears in function or file @var{B}.'' When @var{B} is a file name, |
| you must typically surround it in single quotes. |
| |
| @item |
| The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type |
| @var{type} that appears at address @var{addr}.'' |
| |
| @item |
| A name starting with @samp{$} is a convenience variable |
| (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}). |
| @end itemize |
| |
| In addition, @value{GDBN} provides a few other shortcuts and outright |
| additions specific to Ada: |
| |
| @itemize @bullet |
| @item |
| The assignment statement is allowed as an expression, returning |
| its right-hand operand as its value. Thus, you may enter |
| |
| @smallexample |
| (@value{GDBP}) set x := y + 3 |
| (@value{GDBP}) print A(tmp := y + 1) |
| @end smallexample |
| |
| @item |
| The semicolon is allowed as an ``operator,'' returning as its value |
| the value of its right-hand operand. |
| This allows, for example, |
| complex conditional breaks: |
| |
| @smallexample |
| (@value{GDBP}) break f |
| (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100) |
| @end smallexample |
| |
| @item |
| Rather than use catenation and symbolic character names to introduce special |
| characters into strings, one may instead use a special bracket notation, |
| which is also used to print strings. A sequence of characters of the form |
| @samp{["@var{XX}"]} within a string or character literal denotes the |
| (single) character whose numeric encoding is @var{XX} in hexadecimal. The |
| sequence of characters @samp{["""]} also denotes a single quotation mark |
| in strings. For example, |
| @smallexample |
| "One line.["0a"]Next line.["0a"]" |
| @end smallexample |
| @noindent |
| contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) |
| after each period. |
| |
| @item |
| The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and |
| @t{'Max} is optional (and is ignored in any case). For example, it is valid |
| to write |
| |
| @smallexample |
| (@value{GDBP}) print 'max(x, y) |
| @end smallexample |
| |
| @item |
| When printing arrays, @value{GDBN} uses positional notation when the |
| array has a lower bound of 1, and uses a modified named notation otherwise. |
| For example, a one-dimensional array of three integers with a lower bound |
| of 3 might print as |
| |
| @smallexample |
| (3 => 10, 17, 1) |
| @end smallexample |
| |
| @noindent |
| That is, in contrast to valid Ada, only the first component has a @code{=>} |
| clause. |
| |
| @item |
| You may abbreviate attributes in expressions with any unique, |
| multi-character subsequence of |
| their names (an exact match gets preference). |
| For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh} |
| in place of @t{a'length}. |
| |
| @item |
| @cindex quoting Ada internal identifiers |
| Since Ada is case-insensitive, the debugger normally maps identifiers you type |
| to lower case. The GNAT compiler uses upper-case characters for |
| some of its internal identifiers, which are normally of no interest to users. |
| For the rare occasions when you actually have to look at them, |
| enclose them in angle brackets to avoid the lower-case mapping. |
| For example, |
| @smallexample |
| (@value{GDBP}) print <JMPBUF_SAVE>[0] |
| @end smallexample |
| |
| @item |
| Printing an object of class-wide type or dereferencing an |
| access-to-class-wide value will display all the components of the object's |
| specific type (as indicated by its run-time tag). Likewise, component |
| selection on such a value will operate on the specific type of the |
| object. |
| |
| @end itemize |
| |
| @node Stopping Before Main Program |
| @subsubsection Stopping at the Very Beginning |
| |
| @cindex breakpointing Ada elaboration code |
| It is sometimes necessary to debug the program during elaboration, and |
| before reaching the main procedure. |
| As defined in the Ada Reference |
| Manual, the elaboration code is invoked from a procedure called |
| @code{adainit}. To run your program up to the beginning of |
| elaboration, simply use the following two commands: |
| @code{tbreak adainit} and @code{run}. |
| |
| @node Ada Tasks |
| @subsubsection Extensions for Ada Tasks |
| @cindex Ada, tasking |
| |
| Support for Ada tasks is analogous to that for threads (@pxref{Threads}). |
| @value{GDBN} provides the following task-related commands: |
| |
| @table @code |
| @kindex info tasks |
| @item info tasks |
| This command shows a list of current Ada tasks, as in the following example: |
| |
| |
| @smallexample |
| @iftex |
| @leftskip=0.5cm |
| @end iftex |
| (@value{GDBP}) info tasks |
| ID TID P-ID Pri State Name |
| 1 8088000 0 15 Child Activation Wait main_task |
| 2 80a4000 1 15 Accept Statement b |
| 3 809a800 1 15 Child Activation Wait a |
| * 4 80ae800 3 15 Runnable c |
| |
| @end smallexample |
| |
| @noindent |
| In this listing, the asterisk before the last task indicates it to be the |
| task currently being inspected. |
| |
| @table @asis |
| @item ID |
| Represents @value{GDBN}'s internal task number. |
| |
| @item TID |
| The Ada task ID. |
| |
| @item P-ID |
| The parent's task ID (@value{GDBN}'s internal task number). |
| |
| @item Pri |
| The base priority of the task. |
| |
| @item State |
| Current state of the task. |
| |
| @table @code |
| @item Unactivated |
| The task has been created but has not been activated. It cannot be |
| executing. |
| |
| @item Runnable |
| The task is not blocked for any reason known to Ada. (It may be waiting |
| for a mutex, though.) It is conceptually "executing" in normal mode. |
| |
| @item Terminated |
| The task is terminated, in the sense of ARM 9.3 (5). Any dependents |
| that were waiting on terminate alternatives have been awakened and have |
| terminated themselves. |
| |
| @item Child Activation Wait |
| The task is waiting for created tasks to complete activation. |
| |
| @item Accept Statement |
| The task is waiting on an accept or selective wait statement. |
| |
| @item Waiting on entry call |
| The task is waiting on an entry call. |
| |
| @item Async Select Wait |
| The task is waiting to start the abortable part of an asynchronous |
| select statement. |
| |
| @item Delay Sleep |
| The task is waiting on a select statement with only a delay |
| alternative open. |
| |
| @item Child Termination Wait |
| The task is sleeping having completed a master within itself, and is |
| waiting for the tasks dependent on that master to become terminated or |
| waiting on a terminate Phase. |
| |
| @item Wait Child in Term Alt |
| The task is sleeping waiting for tasks on terminate alternatives to |
| finish terminating. |
| |
| @item Accepting RV with @var{taskno} |
| The task is accepting a rendez-vous with the task @var{taskno}. |
| @end table |
| |
| @item Name |
| Name of the task in the program. |
| |
| @end table |
| |
| @kindex info task @var{taskno} |
| @item info task @var{taskno} |
| This command shows detailled informations on the specified task, as in |
| the following example: |
| @smallexample |
| @iftex |
| @leftskip=0.5cm |
| @end iftex |
| (@value{GDBP}) info tasks |
| ID TID P-ID Pri State Name |
| 1 8077880 0 15 Child Activation Wait main_task |
| * 2 807c468 1 15 Runnable task_1 |
| (@value{GDBP}) info task 2 |
| Ada Task: 0x807c468 |
| Name: task_1 |
| Thread: 0x807f378 |
| Parent: 1 (main_task) |
| Base Priority: 15 |
| State: Runnable |
| @end smallexample |
| |
| @item task |
| @kindex task@r{ (Ada)} |
| @cindex current Ada task ID |
| This command prints the ID of the current task. |
| |
| @smallexample |
| @iftex |
| @leftskip=0.5cm |
| @end iftex |
| (@value{GDBP}) info tasks |
| ID TID P-ID Pri State Name |
| 1 8077870 0 15 Child Activation Wait main_task |
| * 2 807c458 1 15 Runnable t |
| (@value{GDBP}) task |
| [Current task is 2] |
| @end smallexample |
| |
| @item task @var{taskno} |
| @cindex Ada task switching |
| This command is like the @code{thread @var{threadno}} |
| command (@pxref{Threads}). It switches the context of debugging |
| from the current task to the given task. |
| |
| @smallexample |
| @iftex |
| @leftskip=0.5cm |
| @end iftex |
| (@value{GDBP}) info tasks |
| ID TID P-ID Pri State Name |
| 1 8077870 0 15 Child Activation Wait main_task |
| * 2 807c458 1 15 Runnable t |
| (@value{GDBP}) task 1 |
| [Switching to task 1] |
| #0 0x8067726 in pthread_cond_wait () |
| (@value{GDBP}) bt |
| #0 0x8067726 in pthread_cond_wait () |
| #1 0x8056714 in system.os_interface.pthread_cond_wait () |
| #2 0x805cb63 in system.task_primitives.operations.sleep () |
| #3 0x806153e in system.tasking.stages.activate_tasks () |
| #4 0x804aacc in un () at un.adb:5 |
| @end smallexample |
| |
| @item break @var{linespec} task @var{taskno} |
| @itemx break @var{linespec} task @var{taskno} if @dots{} |
| @cindex breakpoints and tasks, in Ada |
| @cindex task breakpoints, in Ada |
| @kindex break @dots{} task @var{taskno}@r{ (Ada)} |
| These commands are like the @code{break @dots{} thread @dots{}} |
| command (@pxref{Thread Stops}). |
| @var{linespec} specifies source lines, as described |
| in @ref{Specify Location}. |
| |
| Use the qualifier @samp{task @var{taskno}} with a breakpoint command |
| to specify that you only want @value{GDBN} to stop the program when a |
| particular Ada task reaches this breakpoint. @var{taskno} is one of the |
| numeric task identifiers assigned by @value{GDBN}, shown in the first |
| column of the @samp{info tasks} display. |
| |
| If you do not specify @samp{task @var{taskno}} when you set a |
| breakpoint, the breakpoint applies to @emph{all} tasks of your |
| program. |
| |
| You can use the @code{task} qualifier on conditional breakpoints as |
| well; in this case, place @samp{task @var{taskno}} before the |
| breakpoint condition (before the @code{if}). |
| |
| For example, |
| |
| @smallexample |
| @iftex |
| @leftskip=0.5cm |
| @end iftex |
| (@value{GDBP}) info tasks |
| ID TID P-ID Pri State Name |
| 1 140022020 0 15 Child Activation Wait main_task |
| 2 140045060 1 15 Accept/Select Wait t2 |
| 3 140044840 1 15 Runnable t1 |
| * 4 140056040 1 15 Runnable t3 |
| (@value{GDBP}) b 15 task 2 |
| Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15. |
| (@value{GDBP}) cont |
| Continuing. |
| task # 1 running |
| task # 2 running |
| |
| Breakpoint 5, test_task_debug () at test_task_debug.adb:15 |
| 15 flush; |
| (@value{GDBP}) info tasks |
| ID TID P-ID Pri State Name |
| 1 140022020 0 15 Child Activation Wait main_task |
| * 2 140045060 1 15 Runnable t2 |
| 3 140044840 1 15 Runnable t1 |
| 4 140056040 1 15 Delay Sleep t3 |
| @end smallexample |
| @end table |
| |
| @node Ada Tasks and Core Files |
| @subsubsection Tasking Support when Debugging Core Files |
| @cindex Ada tasking and core file debugging |
| |
| When inspecting a core file, as opposed to debugging a live program, |
| tasking support may be limited or even unavailable, depending on |
| the platform being used. |
| For instance, on x86-linux, the list of tasks is available, but task |
| switching is not supported. On Tru64, however, task switching will work |
| as usual. |
| |
| On certain platforms, including Tru64, the debugger needs to perform some |
| memory writes in order to provide Ada tasking support. When inspecting |
| a core file, this means that the core file must be opened with read-write |
| privileges, using the command @samp{"set write on"} (@pxref{Patching}). |
| Under these circumstances, you should make a backup copy of the core |
| file before inspecting it with @value{GDBN}. |
| |
| @node Ravenscar Profile |
| @subsubsection Tasking Support when using the Ravenscar Profile |
| @cindex Ravenscar Profile |
| |
| The @dfn{Ravenscar Profile} is a subset of the Ada tasking features, |
| specifically designed for systems with safety-critical real-time |
| requirements. |
| |
| @table @code |
| @kindex set ravenscar task-switching on |
| @cindex task switching with program using Ravenscar Profile |
| @item set ravenscar task-switching on |
| Allows task switching when debugging a program that uses the Ravenscar |
| Profile. This is the default. |
| |
| @kindex set ravenscar task-switching off |
| @item set ravenscar task-switching off |
| Turn off task switching when debugging a program that uses the Ravenscar |
| Profile. This is mostly intended to disable the code that adds support |
| for the Ravenscar Profile, in case a bug in either @value{GDBN} or in |
| the Ravenscar runtime is preventing @value{GDBN} from working properly. |
| To be effective, this command should be run before the program is started. |
| |
| @kindex show ravenscar task-switching |
| @item show ravenscar task-switching |
| Show whether it is possible to switch from task to task in a program |
| using the Ravenscar Profile. |
| |
| @end table |
| |
| @node Ada Glitches |
| @subsubsection Known Peculiarities of Ada Mode |
| @cindex Ada, problems |
| |
| Besides the omissions listed previously (@pxref{Omissions from Ada}), |
| we know of several problems with and limitations of Ada mode in |
| @value{GDBN}, |
| some of which will be fixed with planned future releases of the debugger |
| and the GNU Ada compiler. |
| |
| @itemize @bullet |
| @item |
| Static constants that the compiler chooses not to materialize as objects in |
| storage are invisible to the debugger. |
| |
| @item |
| Named parameter associations in function argument lists are ignored (the |
| argument lists are treated as positional). |
| |
| @item |
| Many useful library packages are currently invisible to the debugger. |
| |
| @item |
| Fixed-point arithmetic, conversions, input, and output is carried out using |
| floating-point arithmetic, and may give results that only approximate those on |
| the host machine. |
| |
| @item |
| The GNAT compiler never generates the prefix @code{Standard} for any of |
| the standard symbols defined by the Ada language. @value{GDBN} knows about |
| this: it will strip the prefix from names when you use it, and will never |
| look for a name you have so qualified among local symbols, nor match against |
| symbols in other packages or subprograms. If you have |
| defined entities anywhere in your program other than parameters and |
| local variables whose simple names match names in @code{Standard}, |
| GNAT's lack of qualification here can cause confusion. When this happens, |
| you can usually resolve the confusion |
| by qualifying the problematic names with package |
| @code{Standard} explicitly. |
| @end itemize |
| |
| Older versions of the compiler sometimes generate erroneous debugging |
| information, resulting in the debugger incorrectly printing the value |
| of affected entities. In some cases, the debugger is able to work |
| around an issue automatically. In other cases, the debugger is able |
| to work around the issue, but the work-around has to be specifically |
| enabled. |
| |
| @kindex set ada trust-PAD-over-XVS |
| @kindex show ada trust-PAD-over-XVS |
| @table @code |
| |
| @item set ada trust-PAD-over-XVS on |
| Configure GDB to strictly follow the GNAT encoding when computing the |
| value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS} |
| types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for |
| a complete description of the encoding used by the GNAT compiler). |
| This is the default. |
| |
| @item set ada trust-PAD-over-XVS off |
| This is related to the encoding using by the GNAT compiler. If @value{GDBN} |
| sometimes prints the wrong value for certain entities, changing @code{ada |
| trust-PAD-over-XVS} to @code{off} activates a work-around which may fix |
| the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to |
| @code{off}, but this incurs a slight performance penalty, so it is |
| recommended to leave this setting to @code{on} unless necessary. |
| |
| @end table |
| |
| @node Unsupported Languages |
| @section Unsupported Languages |
| |
| @cindex unsupported languages |
| @cindex minimal language |
| In addition to the other fully-supported programming languages, |
| @value{GDBN} also provides a pseudo-language, called @code{minimal}. |
| It does not represent a real programming language, but provides a set |
| of capabilities close to what the C or assembly languages provide. |
| This should allow most simple operations to be performed while debugging |
| an application that uses a language currently not supported by @value{GDBN}. |
| |
| If the language is set to @code{auto}, @value{GDBN} will automatically |
| select this language if the current frame corresponds to an unsupported |
| language. |
| |
| @node Symbols |
| @chapter Examining the Symbol Table |
| |
| The commands described in this chapter allow you to inquire about the |
| symbols (names of variables, functions and types) defined in your |
| program. This information is inherent in the text of your program and |
| does not change as your program executes. @value{GDBN} finds it in your |
| program's symbol table, in the file indicated when you started @value{GDBN} |
| (@pxref{File Options, ,Choosing Files}), or by one of the |
| file-management commands (@pxref{Files, ,Commands to Specify Files}). |
| |
| @cindex symbol names |
| @cindex names of symbols |
| @cindex quoting names |
| Occasionally, you may need to refer to symbols that contain unusual |
| characters, which @value{GDBN} ordinarily treats as word delimiters. The |
| most frequent case is in referring to static variables in other |
| source files (@pxref{Variables,,Program Variables}). File names |
| are recorded in object files as debugging symbols, but @value{GDBN} would |
| ordinarily parse a typical file name, like @file{foo.c}, as the three words |
| @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize |
| @samp{foo.c} as a single symbol, enclose it in single quotes; for example, |
| |
| @smallexample |
| p 'foo.c'::x |
| @end smallexample |
| |
| @noindent |
| looks up the value of @code{x} in the scope of the file @file{foo.c}. |
| |
| @table @code |
| @cindex case-insensitive symbol names |
| @cindex case sensitivity in symbol names |
| @kindex set case-sensitive |
| @item set case-sensitive on |
| @itemx set case-sensitive off |
| @itemx set case-sensitive auto |
| Normally, when @value{GDBN} looks up symbols, it matches their names |
| with case sensitivity determined by the current source language. |
| Occasionally, you may wish to control that. The command @code{set |
| case-sensitive} lets you do that by specifying @code{on} for |
| case-sensitive matches or @code{off} for case-insensitive ones. If |
| you specify @code{auto}, case sensitivity is reset to the default |
| suitable for the source language. The default is case-sensitive |
| matches for all languages except for Fortran, for which the default is |
| case-insensitive matches. |
| |
| @kindex show case-sensitive |
| @item show case-sensitive |
| This command shows the current setting of case sensitivity for symbols |
| lookups. |
| |
| @kindex info address |
| @cindex address of a symbol |
| @item info address @var{symbol} |
| Describe where the data for @var{symbol} is stored. For a register |
| variable, this says which register it is kept in. For a non-register |
| local variable, this prints the stack-frame offset at which the variable |
| is always stored. |
| |
| Note the contrast with @samp{print &@var{symbol}}, which does not work |
| at all for a register variable, and for a stack local variable prints |
| the exact address of the current instantiation of the variable. |
| |
| @kindex info symbol |
| @cindex symbol from address |
| @cindex closest symbol and offset for an address |
| @item info symbol @var{addr} |
| Print the name of a symbol which is stored at the address @var{addr}. |
| If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the |
| nearest symbol and an offset from it: |
| |
| @smallexample |
| (@value{GDBP}) info symbol 0x54320 |
| _initialize_vx + 396 in section .text |
| @end smallexample |
| |
| @noindent |
| This is the opposite of the @code{info address} command. You can use |
| it to find out the name of a variable or a function given its address. |
| |
| For dynamically linked executables, the name of executable or shared |
| library containing the symbol is also printed: |
| |
| @smallexample |
| (@value{GDBP}) info symbol 0x400225 |
| _start + 5 in section .text of /tmp/a.out |
| (@value{GDBP}) info symbol 0x2aaaac2811cf |
| __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6 |
| @end smallexample |
| |
| @kindex whatis |
| @item whatis [@var{arg}] |
| Print the data type of @var{arg}, which can be either an expression |
| or a name of a data type. With no argument, print the data type of |
| @code{$}, the last value in the value history. |
| |
| If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it |
| is not actually evaluated, and any side-effecting operations (such as |
| assignments or function calls) inside it do not take place. |
| |
| If @var{arg} is a variable or an expression, @code{whatis} prints its |
| literal type as it is used in the source code. If the type was |
| defined using a @code{typedef}, @code{whatis} will @emph{not} print |
| the data type underlying the @code{typedef}. If the type of the |
| variable or the expression is a compound data type, such as |
| @code{struct} or @code{class}, @code{whatis} never prints their |
| fields or methods. It just prints the @code{struct}/@code{class} |
| name (a.k.a.@: its @dfn{tag}). If you want to see the members of |
| such a compound data type, use @code{ptype}. |
| |
| If @var{arg} is a type name that was defined using @code{typedef}, |
| @code{whatis} @dfn{unrolls} only one level of that @code{typedef}. |
| Unrolling means that @code{whatis} will show the underlying type used |
| in the @code{typedef} declaration of @var{arg}. However, if that |
| underlying type is also a @code{typedef}, @code{whatis} will not |
| unroll it. |
| |
| For C code, the type names may also have the form @samp{class |
| @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union |
| @var{union-tag}} or @samp{enum @var{enum-tag}}. |
| |
| @kindex ptype |
| @item ptype [@var{arg}] |
| @code{ptype} accepts the same arguments as @code{whatis}, but prints a |
| detailed description of the type, instead of just the name of the type. |
| @xref{Expressions, ,Expressions}. |
| |
| Contrary to @code{whatis}, @code{ptype} always unrolls any |
| @code{typedef}s in its argument declaration, whether the argument is |
| a variable, expression, or a data type. This means that @code{ptype} |
| of a variable or an expression will not print literally its type as |
| present in the source code---use @code{whatis} for that. @code{typedef}s at |
| the pointer or reference targets are also unrolled. Only @code{typedef}s of |
| fields, methods and inner @code{class typedef}s of @code{struct}s, |
| @code{class}es and @code{union}s are not unrolled even with @code{ptype}. |
| |
| For example, for this variable declaration: |
| |
| @smallexample |
| typedef double real_t; |
| struct complex @{ real_t real; double imag; @}; |
| typedef struct complex complex_t; |
| complex_t var; |
| real_t *real_pointer_var; |
| @end smallexample |
| |
| @noindent |
| the two commands give this output: |
| |
| @smallexample |
| @group |
| (@value{GDBP}) whatis var |
| type = complex_t |
| (@value{GDBP}) ptype var |
| type = struct complex @{ |
| real_t real; |
| double imag; |
| @} |
| (@value{GDBP}) whatis complex_t |
| type = struct complex |
| (@value{GDBP}) whatis struct complex |
| type = struct complex |
| (@value{GDBP}) ptype struct complex |
| type = struct complex @{ |
| real_t real; |
| double imag; |
| @} |
| (@value{GDBP}) whatis real_pointer_var |
| type = real_t * |
| (@value{GDBP}) ptype real_pointer_var |
| type = double * |
| @end group |
| @end smallexample |
| |
| @noindent |
| As with @code{whatis}, using @code{ptype} without an argument refers to |
| the type of @code{$}, the last value in the value history. |
| |
| @cindex incomplete type |
| Sometimes, programs use opaque data types or incomplete specifications |
| of complex data structure. If the debug information included in the |
| program does not allow @value{GDBN} to display a full declaration of |
| the data type, it will say @samp{<incomplete type>}. For example, |
| given these declarations: |
| |
| @smallexample |
| struct foo; |
| struct foo *fooptr; |
| @end smallexample |
| |
| @noindent |
| but no definition for @code{struct foo} itself, @value{GDBN} will say: |
| |
| @smallexample |
| (@value{GDBP}) ptype foo |
| $1 = <incomplete type> |
| @end smallexample |
| |
| @noindent |
| ``Incomplete type'' is C terminology for data types that are not |
| completely specified. |
| |
| @kindex info types |
| @item info types @var{regexp} |
| @itemx info types |
| Print a brief description of all types whose names match the regular |
| expression @var{regexp} (or all types in your program, if you supply |
| no argument). Each complete typename is matched as though it were a |
| complete line; thus, @samp{i type value} gives information on all |
| types in your program whose names include the string @code{value}, but |
| @samp{i type ^value$} gives information only on types whose complete |
| name is @code{value}. |
| |
| This command differs from @code{ptype} in two ways: first, like |
| @code{whatis}, it does not print a detailed description; second, it |
| lists all source files where a type is defined. |
| |
| @kindex info scope |
| @cindex local variables |
| @item info scope @var{location} |
| List all the variables local to a particular scope. This command |
| accepts a @var{location} argument---a function name, a source line, or |
| an address preceded by a @samp{*}, and prints all the variables local |
| to the scope defined by that location. (@xref{Specify Location}, for |
| details about supported forms of @var{location}.) For example: |
| |
| @smallexample |
| (@value{GDBP}) @b{info scope command_line_handler} |
| Scope for command_line_handler: |
| Symbol rl is an argument at stack/frame offset 8, length 4. |
| Symbol linebuffer is in static storage at address 0x150a18, length 4. |
| Symbol linelength is in static storage at address 0x150a1c, length 4. |
| Symbol p is a local variable in register $esi, length 4. |
| Symbol p1 is a local variable in register $ebx, length 4. |
| Symbol nline is a local variable in register $edx, length 4. |
| Symbol repeat is a local variable at frame offset -8, length 4. |
| @end smallexample |
| |
| @noindent |
| This command is especially useful for determining what data to collect |
| during a @dfn{trace experiment}, see @ref{Tracepoint Actions, |
| collect}. |
| |
| @kindex info source |
| @item info source |
| Show information about the current source file---that is, the source file for |
| the function containing the current point of execution: |
| @itemize @bullet |
| @item |
| the name of the source file, and the directory containing it, |
| @item |
| the directory it was compiled in, |
| @item |
| its length, in lines, |
| @item |
| which programming language it is written in, |
| @item |
| whether the executable includes debugging information for that file, and |
| if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and |
| @item |
| whether the debugging information includes information about |
| preprocessor macros. |
| @end itemize |
| |
| |
| @kindex info sources |
| @item info sources |
| Print the names of all source files in your program for which there is |
| debugging information, organized into two lists: files whose symbols |
| have already been read, and files whose symbols will be read when needed. |
| |
| @kindex info functions |
| @item info functions |
| Print the names and data types of all defined functions. |
| |
| @item info functions @var{regexp} |
| Print the names and data types of all defined functions |
| whose names contain a match for regular expression @var{regexp}. |
| Thus, @samp{info fun step} finds all functions whose names |
| include @code{step}; @samp{info fun ^step} finds those whose names |
| start with @code{step}. If a function name contains characters |
| that conflict with the regular expression language (e.g.@: |
| @samp{operator*()}), they may be quoted with a backslash. |
| |
| @kindex info variables |
| @item info variables |
| Print the names and data types of all variables that are defined |
| outside of functions (i.e.@: excluding local variables). |
| |
| @item info variables @var{regexp} |
| Print the names and data types of all variables (except for local |
| variables) whose names contain a match for regular expression |
| @var{regexp}. |
| |
| @kindex info classes |
| @cindex Objective-C, classes and selectors |
| @item info classes |
| @itemx info classes @var{regexp} |
| Display all Objective-C classes in your program, or |
| (with the @var{regexp} argument) all those matching a particular regular |
| expression. |
| |
| @kindex info selectors |
| @item info selectors |
| @itemx info selectors @var{regexp} |
| Display all Objective-C selectors in your program, or |
| (with the @var{regexp} argument) all those matching a particular regular |
| expression. |
| |
| @ignore |
| This was never implemented. |
| @kindex info methods |
| @item info methods |
| @itemx info methods @var{regexp} |
| The @code{info methods} command permits the user to examine all defined |
| methods within C@t{++} program, or (with the @var{regexp} argument) a |
| specific set of methods found in the various C@t{++} classes. Many |
| C@t{++} classes provide a large number of methods. Thus, the output |
| from the @code{ptype} command can be overwhelming and hard to use. The |
| @code{info-methods} command filters the methods, printing only those |
| which match the regular-expression @var{regexp}. |
| @end ignore |
| |
| @cindex opaque data types |
| @kindex set opaque-type-resolution |
| @item set opaque-type-resolution on |
| Tell @value{GDBN} to resolve opaque types. An opaque type is a type |
| declared as a pointer to a @code{struct}, @code{class}, or |
| @code{union}---for example, @code{struct MyType *}---that is used in one |
| source file although the full declaration of @code{struct MyType} is in |
| another source file. The default is on. |
| |
| A change in the setting of this subcommand will not take effect until |
| the next time symbols for a file are loaded. |
| |
| @item set opaque-type-resolution off |
| Tell @value{GDBN} not to resolve opaque types. In this case, the type |
| is printed as follows: |
| @smallexample |
| @{<no data fields>@} |
| @end smallexample |
| |
| @kindex show opaque-type-resolution |
| @item show opaque-type-resolution |
| Show whether opaque types are resolved or not. |
| |
| @kindex maint print symbols |
| @cindex symbol dump |
| @kindex maint print psymbols |
| @cindex partial symbol dump |
| @item maint print symbols @var{filename} |
| @itemx maint print psymbols @var{filename} |
| @itemx maint print msymbols @var{filename} |
| Write a dump of debugging symbol data into the file @var{filename}. |
| These commands are used to debug the @value{GDBN} symbol-reading code. Only |
| symbols with debugging data are included. If you use @samp{maint print |
| symbols}, @value{GDBN} includes all the symbols for which it has already |
| collected full details: that is, @var{filename} reflects symbols for |
| only those files whose symbols @value{GDBN} has read. You can use the |
| command @code{info sources} to find out which files these are. If you |
| use @samp{maint print psymbols} instead, the dump shows information about |
| symbols that @value{GDBN} only knows partially---that is, symbols defined in |
| files that @value{GDBN} has skimmed, but not yet read completely. Finally, |
| @samp{maint print msymbols} dumps just the minimal symbol information |
| required for each object file from which @value{GDBN} has read some symbols. |
| @xref{Files, ,Commands to Specify Files}, for a discussion of how |
| @value{GDBN} reads symbols (in the description of @code{symbol-file}). |
| |
| @kindex maint info symtabs |
| @kindex maint info psymtabs |
| @cindex listing @value{GDBN}'s internal symbol tables |
| @cindex symbol tables, listing @value{GDBN}'s internal |
| @cindex full symbol tables, listing @value{GDBN}'s internal |
| @cindex partial symbol tables, listing @value{GDBN}'s internal |
| @item maint info symtabs @r{[} @var{regexp} @r{]} |
| @itemx maint info psymtabs @r{[} @var{regexp} @r{]} |
| |
| List the @code{struct symtab} or @code{struct partial_symtab} |
| structures whose names match @var{regexp}. If @var{regexp} is not |
| given, list them all. The output includes expressions which you can |
| copy into a @value{GDBN} debugging this one to examine a particular |
| structure in more detail. For example: |
| |
| @smallexample |
| (@value{GDBP}) maint info psymtabs dwarf2read |
| @{ objfile /home/gnu/build/gdb/gdb |
| ((struct objfile *) 0x82e69d0) |
| @{ psymtab /home/gnu/src/gdb/dwarf2read.c |
| ((struct partial_symtab *) 0x8474b10) |
| readin no |
| fullname (null) |
| text addresses 0x814d3c8 -- 0x8158074 |
| globals (* (struct partial_symbol **) 0x8507a08 @@ 9) |
| statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882) |
| dependencies (none) |
| @} |
| @} |
| (@value{GDBP}) maint info symtabs |
| (@value{GDBP}) |
| @end smallexample |
| @noindent |
| We see that there is one partial symbol table whose filename contains |
| the string @samp{dwarf2read}, belonging to the @samp{gdb} executable; |
| and we see that @value{GDBN} has not read in any symtabs yet at all. |
| If we set a breakpoint on a function, that will cause @value{GDBN} to |
| read the symtab for the compilation unit containing that function: |
| |
| @smallexample |
| (@value{GDBP}) break dwarf2_psymtab_to_symtab |
| Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c, |
| line 1574. |
| (@value{GDBP}) maint info symtabs |
| @{ objfile /home/gnu/build/gdb/gdb |
| ((struct objfile *) 0x82e69d0) |
| @{ symtab /home/gnu/src/gdb/dwarf2read.c |
| ((struct symtab *) 0x86c1f38) |
| dirname (null) |
| fullname (null) |
| blockvector ((struct blockvector *) 0x86c1bd0) (primary) |
| linetable ((struct linetable *) 0x8370fa0) |
| debugformat DWARF 2 |
| @} |
| @} |
| (@value{GDBP}) |
| @end smallexample |
| @end table |
| |
| |
| @node Altering |
| @chapter Altering Execution |
| |
| Once you think you have found an error in your program, you might want to |
| find out for certain whether correcting the apparent error would lead to |
| correct results in the rest of the run. You can find the answer by |
| experiment, using the @value{GDBN} features for altering execution of the |
| program. |
| |
| For example, you can store new values into variables or memory |
| locations, give your program a signal, restart it at a different |
| address, or even return prematurely from a function. |
| |
| @menu |
| * Assignment:: Assignment to variables |
| * Jumping:: Continuing at a different address |
| * Signaling:: Giving your program a signal |
| * Returning:: Returning from a function |
| * Calling:: Calling your program's functions |
| * Patching:: Patching your program |
| @end menu |
| |
| @node Assignment |
| @section Assignment to Variables |
| |
| @cindex assignment |
| @cindex setting variables |
| To alter the value of a variable, evaluate an assignment expression. |
| @xref{Expressions, ,Expressions}. For example, |
| |
| @smallexample |
| print x=4 |
| @end smallexample |
| |
| @noindent |
| stores the value 4 into the variable @code{x}, and then prints the |
| value of the assignment expression (which is 4). |
| @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more |
| information on operators in supported languages. |
| |
| @kindex set variable |
| @cindex variables, setting |
| If you are not interested in seeing the value of the assignment, use the |
| @code{set} command instead of the @code{print} command. @code{set} is |
| really the same as @code{print} except that the expression's value is |
| not printed and is not put in the value history (@pxref{Value History, |
| ,Value History}). The expression is evaluated only for its effects. |
| |
| If the beginning of the argument string of the @code{set} command |
| appears identical to a @code{set} subcommand, use the @code{set |
| variable} command instead of just @code{set}. This command is identical |
| to @code{set} except for its lack of subcommands. For example, if your |
| program has a variable @code{width}, you get an error if you try to set |
| a new value with just @samp{set width=13}, because @value{GDBN} has the |
| command @code{set width}: |
| |
| @smallexample |
| (@value{GDBP}) whatis width |
| type = double |
| (@value{GDBP}) p width |
| $4 = 13 |
| (@value{GDBP}) set width=47 |
| Invalid syntax in expression. |
| @end smallexample |
| |
| @noindent |
| The invalid expression, of course, is @samp{=47}. In |
| order to actually set the program's variable @code{width}, use |
| |
| @smallexample |
| (@value{GDBP}) set var width=47 |
| @end smallexample |
| |
| Because the @code{set} command has many subcommands that can conflict |
| with the names of program variables, it is a good idea to use the |
| @code{set variable} command instead of just @code{set}. For example, if |
| your program has a variable @code{g}, you run into problems if you try |
| to set a new value with just @samp{set g=4}, because @value{GDBN} has |
| the command @code{set gnutarget}, abbreviated @code{set g}: |
| |
| @smallexample |
| @group |
| (@value{GDBP}) whatis g |
| type = double |
| (@value{GDBP}) p g |
| $1 = 1 |
| (@value{GDBP}) set g=4 |
| (@value{GDBP}) p g |
| $2 = 1 |
| (@value{GDBP}) r |
| The program being debugged has been started already. |
| Start it from the beginning? (y or n) y |
| Starting program: /home/smith/cc_progs/a.out |
| "/home/smith/cc_progs/a.out": can't open to read symbols: |
| Invalid bfd target. |
| (@value{GDBP}) show g |
| The current BFD target is "=4". |
| @end group |
| @end smallexample |
| |
| @noindent |
| The program variable @code{g} did not change, and you silently set the |
| @code{gnutarget} to an invalid value. In order to set the variable |
| @code{g}, use |
| |
| @smallexample |
| (@value{GDBP}) set var g=4 |
| @end smallexample |
| |
| @value{GDBN} allows more implicit conversions in assignments than C; you can |
| freely store an integer value into a pointer variable or vice versa, |
| and you can convert any structure to any other structure that is the |
| same length or shorter. |
| @comment FIXME: how do structs align/pad in these conversions? |
| @comment /doc@cygnus.com 18dec1990 |
| |
| To store values into arbitrary places in memory, use the @samp{@{@dots{}@}} |
| construct to generate a value of specified type at a specified address |
| (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers |
| to memory location @code{0x83040} as an integer (which implies a certain size |
| and representation in memory), and |
| |
| @smallexample |
| set @{int@}0x83040 = 4 |
| @end smallexample |
| |
| @noindent |
| stores the value 4 into that memory location. |
| |
| @node Jumping |
| @section Continuing at a Different Address |
| |
| Ordinarily, when you continue your program, you do so at the place where |
| it stopped, with the @code{continue} command. You can instead continue at |
| an address of your own choosing, with the following commands: |
| |
| @table @code |
| @kindex jump |
| @item jump @var{linespec} |
| @itemx jump @var{location} |
| Resume execution at line @var{linespec} or at address given by |
| @var{location}. Execution stops again immediately if there is a |
| breakpoint there. @xref{Specify Location}, for a description of the |
| different forms of @var{linespec} and @var{location}. It is common |
| practice to use the @code{tbreak} command in conjunction with |
| @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}. |
| |
| The @code{jump} command does not change the current stack frame, or |
| the stack pointer, or the contents of any memory location or any |
| register other than the program counter. If line @var{linespec} is in |
| a different function from the one currently executing, the results may |
| be bizarre if the two functions expect different patterns of arguments or |
| of local variables. For this reason, the @code{jump} command requests |
| confirmation if the specified line is not in the function currently |
| executing. However, even bizarre results are predictable if you are |
| well acquainted with the machine-language code of your program. |
| @end table |
| |
| @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt. |
| On many systems, you can get much the same effect as the @code{jump} |
| command by storing a new value into the register @code{$pc}. The |
| difference is that this does not start your program running; it only |
| changes the address of where it @emph{will} run when you continue. For |
| example, |
| |
| @smallexample |
| set $pc = 0x485 |
| @end smallexample |
| |
| @noindent |
| makes the next @code{continue} command or stepping command execute at |
| address @code{0x485}, rather than at the address where your program stopped. |
| @xref{Continuing and Stepping, ,Continuing and Stepping}. |
| |
| The most common occasion to use the @code{jump} command is to back |
| up---perhaps with more breakpoints set---over a portion of a program |
| that has already executed, in order to examine its execution in more |
| detail. |
| |
| @c @group |
| @node Signaling |
| @section Giving your Program a Signal |
| @cindex deliver a signal to a program |
| |
| @table @code |
| @kindex signal |
| @item signal @var{signal} |
| Resume execution where your program stopped, but immediately give it the |
| signal @var{signal}. @var{signal} can be the name or the number of a |
| signal. For example, on many systems @code{signal 2} and @code{signal |
| SIGINT} are both ways of sending an interrupt signal. |
| |
| Alternatively, if @var{signal} is zero, continue execution without |
| giving a signal. This is useful when your program stopped on account of |
| a signal and would ordinary see the signal when resumed with the |
| @code{continue} command; @samp{signal 0} causes it to resume without a |
| signal. |
| |
| @code{signal} does not repeat when you press @key{RET} a second time |
| after executing the command. |
| @end table |
| @c @end group |
| |
| Invoking the @code{signal} command is not the same as invoking the |
| @code{kill} utility from the shell. Sending a signal with @code{kill} |
| causes @value{GDBN} to decide what to do with the signal depending on |
| the signal handling tables (@pxref{Signals}). The @code{signal} command |
| passes the signal directly to your program. |
| |
| |
| @node Returning |
| @section Returning from a Function |
| |
| @table @code |
| @cindex returning from a function |
| @kindex return |
| @item return |
| @itemx return @var{expression} |
| You can cancel execution of a function call with the @code{return} |
| command. If you give an |
| @var{expression} argument, its value is used as the function's return |
| value. |
| @end table |
| |
| When you use @code{return}, @value{GDBN} discards the selected stack frame |
| (and all frames within it). You can think of this as making the |
| discarded frame return prematurely. If you wish to specify a value to |
| be returned, give that value as the argument to @code{return}. |
| |
| This pops the selected stack frame (@pxref{Selection, ,Selecting a |
| Frame}), and any other frames inside of it, leaving its caller as the |
| innermost remaining frame. That frame becomes selected. The |
| specified value is stored in the registers used for returning values |
| of functions. |
| |
| The @code{return} command does not resume execution; it leaves the |
| program stopped in the state that would exist if the function had just |
| returned. In contrast, the @code{finish} command (@pxref{Continuing |
| and Stepping, ,Continuing and Stepping}) resumes execution until the |
| selected stack frame returns naturally. |
| |
| @value{GDBN} needs to know how the @var{expression} argument should be set for |
| the inferior. The concrete registers assignment depends on the OS ABI and the |
| type being returned by the selected stack frame. For example it is common for |
| OS ABI to return floating point values in FPU registers while integer values in |
| CPU registers. Still some ABIs return even floating point values in CPU |
| registers. Larger integer widths (such as @code{long long int}) also have |
| specific placement rules. @value{GDBN} already knows the OS ABI from its |
| current target so it needs to find out also the type being returned to make the |
| assignment into the right register(s). |
| |
| Normally, the selected stack frame has debug info. @value{GDBN} will always |
| use the debug info instead of the implicit type of @var{expression} when the |
| debug info is available. For example, if you type @kbd{return -1}, and the |
| function in the current stack frame is declared to return a @code{long long |
| int}, @value{GDBN} transparently converts the implicit @code{int} value of -1 |
| into a @code{long long int}: |
| |
| @smallexample |
| Breakpoint 1, func () at gdb.base/return-nodebug.c:29 |
| 29 return 31; |
| (@value{GDBP}) return -1 |
| Make func return now? (y or n) y |
| #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43 |
| 43 printf ("result=%lld\n", func ()); |
| (@value{GDBP}) |
| @end smallexample |
| |
| However, if the selected stack frame does not have a debug info, e.g., if the |
| function was compiled without debug info, @value{GDBN} has to find out the type |
| to return from user. Specifying a different type by mistake may set the value |
| in different inferior registers than the caller code expects. For example, |
| typing @kbd{return -1} with its implicit type @code{int} would set only a part |
| of a @code{long long int} result for a debug info less function (on 32-bit |
| architectures). Therefore the user is required to specify the return type by |
| an appropriate cast explicitly: |
| |
| @smallexample |
| Breakpoint 2, 0x0040050b in func () |
| (@value{GDBP}) return -1 |
| Return value type not available for selected stack frame. |
| Please use an explicit cast of the value to return. |
| (@value{GDBP}) return (long long int) -1 |
| Make selected stack frame return now? (y or n) y |
| #0 0x00400526 in main () |
| (@value{GDBP}) |
| @end smallexample |
| |
| @node Calling |
| @section Calling Program Functions |
| |
| @table @code |
| @cindex calling functions |
| @cindex inferior functions, calling |
| @item print @var{expr} |
| Evaluate the expression @var{expr} and display the resulting value. |
| @var{expr} may include calls to functions in the program being |
| debugged. |
| |
| @kindex call |
| @item call @var{expr} |
| Evaluate the expression @var{expr} without displaying @code{void} |
| returned values. |
| |
| You can use this variant of the @code{print} command if you want to |
| execute a function from your program that does not return anything |
| (a.k.a.@: @dfn{a void function}), but without cluttering the output |
| with @code{void} returned values that @value{GDBN} will otherwise |
| print. If the result is not void, it is printed and saved in the |
| value history. |
| @end table |
| |
| It is possible for the function you call via the @code{print} or |
| @code{call} command to generate a signal (e.g., if there's a bug in |
| the function, or if you passed it incorrect arguments). What happens |
| in that case is controlled by the @code{set unwindonsignal} command. |
| |
| Similarly, with a C@t{++} program it is possible for the function you |
| call via the @code{print} or @code{call} command to generate an |
| exception that is not handled due to the constraints of the dummy |
| frame. In this case, any exception that is raised in the frame, but has |
| an out-of-frame exception handler will not be found. GDB builds a |
| dummy-frame for the inferior function call, and the unwinder cannot |
| seek for exception handlers outside of this dummy-frame. What happens |
| in that case is controlled by the |
| @code{set unwind-on-terminating-exception} command. |
| |
| @table @code |
| @item set unwindonsignal |
| @kindex set unwindonsignal |
| @cindex unwind stack in called functions |
| @cindex call dummy stack unwinding |
| Set unwinding of the stack if a signal is received while in a function |
| that @value{GDBN} called in the program being debugged. If set to on, |
| @value{GDBN} unwinds the stack it created for the call and restores |
| the context to what it was before the call. If set to off (the |
| default), @value{GDBN} stops in the frame where the signal was |
| received. |
| |
| @item show unwindonsignal |
| @kindex show unwindonsignal |
| Show the current setting of stack unwinding in the functions called by |
| @value{GDBN}. |
| |
| @item set unwind-on-terminating-exception |
| @kindex set unwind-on-terminating-exception |
| @cindex unwind stack in called functions with unhandled exceptions |
| @cindex call dummy stack unwinding on unhandled exception. |
| Set unwinding of the stack if a C@t{++} exception is raised, but left |
| unhandled while in a function that @value{GDBN} called in the program being |
| debugged. If set to on (the default), @value{GDBN} unwinds the stack |
| it created for the call and restores the context to what it was before |
| the call. If set to off, @value{GDBN} the exception is delivered to |
| the default C@t{++} exception handler and the inferior terminated. |
| |
| @item show unwind-on-terminating-exception |
| @kindex show unwind-on-terminating-exception |
| Show the current setting of stack unwinding in the functions called by |
| @value{GDBN}. |
| |
| @end table |
| |
| @cindex weak alias functions |
| Sometimes, a function you wish to call is actually a @dfn{weak alias} |
| for another function. In such case, @value{GDBN} might not pick up |
| the type information, including the types of the function arguments, |
| which causes @value{GDBN} to call the inferior function incorrectly. |
| As a result, the called function will function erroneously and may |
| even crash. A solution to that is to use the name of the aliased |
| function instead. |
| |
| @node Patching |
| @section Patching Programs |
| |
| @cindex patching binaries |
| @cindex writing into executables |
| @cindex writing into corefiles |
| |
| By default, @value{GDBN} opens the file containing your program's |
| executable code (or the corefile) read-only. This prevents accidental |
| alterations to machine code; but it also prevents you from intentionally |
| patching your program's binary. |
| |
| If you'd like to be able to patch the binary, you can specify that |
| explicitly with the @code{set write} command. For example, you might |
| want to turn on internal debugging flags, or even to make emergency |
| repairs. |
| |
| @table @code |
| @kindex set write |
| @item set write on |
| @itemx set write off |
| If you specify @samp{set write on}, @value{GDBN} opens executable and |
| core files for both reading and writing; if you specify @kbd{set write |
| off} (the default), @value{GDBN} opens them read-only. |
| |
| If you have already loaded a file, you must load it again (using the |
| @code{exec-file} or @code{core-file} command) after changing @code{set |
| write}, for your new setting to take effect. |
| |
| @item show write |
| @kindex show write |
| Display whether executable files and core files are opened for writing |
| as well as reading. |
| @end table |
| |
| @node GDB Files |
| @chapter @value{GDBN} Files |
| |
| @value{GDBN} needs to know the file name of the program to be debugged, |
| both in order to read its symbol table and in order to start your |
| program. To debug a core dump of a previous run, you must also tell |
| @value{GDBN} the name of the core dump file. |
| |
| @menu |
| * Files:: Commands to specify files |
| * Separate Debug Files:: Debugging information in separate files |
| * Index Files:: Index files speed up GDB |
| * Symbol Errors:: Errors reading symbol files |
| * Data Files:: GDB data files |
| @end menu |
| |
| @node Files |
| @section Commands to Specify Files |
| |
| @cindex symbol table |
| @cindex core dump file |
| |
| You may want to specify executable and core dump file names. The usual |
| way to do this is at start-up time, using the arguments to |
| @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and |
| Out of @value{GDBN}}). |
| |
| Occasionally it is necessary to change to a different file during a |
| @value{GDBN} session. Or you may run @value{GDBN} and forget to |
| specify a file you want to use. Or you are debugging a remote target |
| via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver} |
| Program}). In these situations the @value{GDBN} commands to specify |
| new files are useful. |
| |
| @table @code |
| @cindex executable file |
| @kindex file |
| @item file @var{filename} |
| Use @var{filename} as the program to be debugged. It is read for its |
| symbols and for the contents of pure memory. It is also the program |
| executed when you use the @code{run} command. If you do not specify a |
| directory and the file is not found in the @value{GDBN} working directory, |
| @value{GDBN} uses the environment variable @code{PATH} as a list of |
| directories to search, just as the shell does when looking for a program |
| to run. You can change the value of this variable, for both @value{GDBN} |
| and your program, using the @code{path} command. |
| |
| @cindex unlinked object files |
| @cindex patching object files |
| You can load unlinked object @file{.o} files into @value{GDBN} using |
| the @code{file} command. You will not be able to ``run'' an object |
| file, but you can disassemble functions and inspect variables. Also, |
| if the underlying BFD functionality supports it, you could use |
| @kbd{gdb -write} to patch object files using this technique. Note |
| that @value{GDBN} can neither interpret nor modify relocations in this |
| case, so branches and some initialized variables will appear to go to |
| the wrong place. But this feature is still handy from time to time. |
| |
| @item file |
| @code{file} with no argument makes @value{GDBN} discard any information it |
| has on both executable file and the symbol table. |
| |
| @kindex exec-file |
| @item exec-file @r{[} @var{filename} @r{]} |
| Specify that the program to be run (but not the symbol table) is found |
| in @var{filename}. @value{GDBN} searches the environment variable @code{PATH} |
| if necessary to locate your program. Omitting @var{filename} means to |
| discard information on the executable file. |
| |
| @kindex symbol-file |
| @item symbol-file @r{[} @var{filename} @r{]} |
| Read symbol table information from file @var{filename}. @code{PATH} is |
| searched when necessary. Use the @code{file} command to get both symbol |
| table and program to run from the same file. |
| |
| @code{symbol-file} with no argument clears out @value{GDBN} information on your |
| program's symbol table. |
| |
| The @code{symbol-file} command causes @value{GDBN} to forget the contents of |
| some breakpoints and auto-display expressions. This is because they may |
| contain pointers to the internal data recording symbols and data types, |
| which are part of the old symbol table data being discarded inside |
| @value{GDBN}. |
| |
| @code{symbol-file} does not repeat if you press @key{RET} again after |
| executing it once. |
| |
| When @value{GDBN} is configured for a particular environment, it |
| understands debugging information in whatever format is the standard |
| generated for that environment; you may use either a @sc{gnu} compiler, or |
| other compilers that adhere to the local conventions. |
| Best results are usually obtained from @sc{gnu} compilers; for example, |
| using @code{@value{NGCC}} you can generate debugging information for |
| optimized code. |
| |
| For most kinds of object files, with the exception of old SVR3 systems |
| using COFF, the @code{symbol-file} command does not normally read the |
| symbol table in full right away. Instead, it scans the symbol table |
| quickly to find which source files and which symbols are present. The |
| details are read later, one source file at a time, as they are needed. |
| |
| The purpose of this two-stage reading strategy is to make @value{GDBN} |
| start up faster. For the most part, it is invisible except for |
| occasional pauses while the symbol table details for a particular source |
| file are being read. (The @code{set verbose} command can turn these |
| pauses into messages if desired. @xref{Messages/Warnings, ,Optional |
| Warnings and Messages}.) |
| |
| We have not implemented the two-stage strategy for COFF yet. When the |
| symbol table is stored in COFF format, @code{symbol-file} reads the |
| symbol table data in full right away. Note that ``stabs-in-COFF'' |
| still does the two-stage strategy, since the debug info is actually |
| in stabs format. |
| |
| @kindex readnow |
| @cindex reading symbols immediately |
| @cindex symbols, reading immediately |
| @item symbol-file @r{[} -readnow @r{]} @var{filename} |
| @itemx file @r{[} -readnow @r{]} @var{filename} |
| You can override the @value{GDBN} two-stage strategy for reading symbol |
| tables by using the @samp{-readnow} option with any of the commands that |
| load symbol table information, if you want to be sure @value{GDBN} has the |
| entire symbol table available. |
| |
| @c FIXME: for now no mention of directories, since this seems to be in |
| @c flux. 13mar1992 status is that in theory GDB would look either in |
| @c current dir or in same dir as myprog; but issues like competing |
| @c GDB's, or clutter in system dirs, mean that in practice right now |
| @c only current dir is used. FFish says maybe a special GDB hierarchy |
| @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol |
| @c files. |
| |
| @kindex core-file |
| @item core-file @r{[}@var{filename}@r{]} |
| @itemx core |
| Specify the whereabouts of a core dump file to be used as the ``contents |
| of memory''. Traditionally, core files contain only some parts of the |
| address space of the process that generated them; @value{GDBN} can access the |
| executable file itself for other parts. |
| |
| @code{core-file} with no argument specifies that no core file is |
| to be used. |
| |
| Note that the core file is ignored when your program is actually running |
| under @value{GDBN}. So, if you have been running your program and you |
| wish to debug a core file instead, you must kill the subprocess in which |
| the program is running. To do this, use the @code{kill} command |
| (@pxref{Kill Process, ,Killing the Child Process}). |
| |
| @kindex add-symbol-file |
| @cindex dynamic linking |
| @item add-symbol-file @var{filename} @var{address} |
| @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} |
| @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{} |
| The @code{add-symbol-file} command reads additional symbol table |
| information from the file @var{filename}. You would use this command |
| when @var{filename} has been dynamically loaded (by some other means) |
| into the program that is running. @var{address} should be the memory |
| address at which the file has been loaded; @value{GDBN} cannot figure |
| this out for itself. You can additionally specify an arbitrary number |
| of @samp{-s @var{section} @var{address}} pairs, to give an explicit |
| section name and base address for that section. You can specify any |
| @var{address} as an expression. |
| |
| The symbol table of the file @var{filename} is added to the symbol table |
| originally read with the @code{symbol-file} command. You can use the |
| @code{add-symbol-file} command any number of times; the new symbol data |
| thus read keeps adding to the old. To discard all old symbol data |
| instead, use the @code{symbol-file} command without any arguments. |
| |
| @cindex relocatable object files, reading symbols from |
| @cindex object files, relocatable, reading symbols from |
| @cindex reading symbols from relocatable object files |
| @cindex symbols, reading from relocatable object files |
| @cindex @file{.o} files, reading symbols from |
| Although @var{filename} is typically a shared library file, an |
| executable file, or some other object file which has been fully |
| relocated for loading into a process, you can also load symbolic |
| information from relocatable @file{.o} files, as long as: |
| |
| @itemize @bullet |
| @item |
| the file's symbolic information refers only to linker symbols defined in |
| that file, not to symbols defined by other object files, |
| @item |
| every section the file's symbolic information refers to has actually |
| been loaded into the inferior, as it appears in the file, and |
| @item |
| you can determine the address at which every section was loaded, and |
| provide these to the @code{add-symbol-file} command. |
| @end itemize |
| |
| @noindent |
| Some embedded operating systems, like Sun Chorus and VxWorks, can load |
| relocatable files into an already running program; such systems |
| typically make the requirements above easy to meet. However, it's |
| important to recognize that many native systems use complex link |
| procedures (@code{.linkonce} section factoring and C@t{++} constructor table |
| assembly, for example) that make the requirements difficult to meet. In |
| general, one cannot assume that using @code{add-symbol-file} to read a |
| relocatable object file's symbolic information will have the same effect |
| as linking the relocatable object file into the program in the normal |
| way. |
| |
| @code{add-symbol-file} does not repeat if you press @key{RET} after using it. |
| |
| @kindex add-symbol-file-from-memory |
| @cindex @code{syscall DSO} |
| @cindex load symbols from memory |
| @item add-symbol-file-from-memory @var{address} |
| Load symbols from the given @var{address} in a dynamically loaded |
| object file whose image is mapped directly into the inferior's memory. |
| For example, the Linux kernel maps a @code{syscall DSO} into each |
| process's address space; this DSO provides kernel-specific code for |
| some system calls. The argument can be any expression whose |
| evaluation yields the address of the file's shared object file header. |
| For this command to work, you must have used @code{symbol-file} or |
| @code{exec-file} commands in advance. |
| |
| @kindex add-shared-symbol-files |
| @kindex assf |
| @item add-shared-symbol-files @var{library-file} |
| @itemx assf @var{library-file} |
| The @code{add-shared-symbol-files} command can currently be used only |
| in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an |
| alias for the @code{dll-symbols} command (@pxref{Cygwin Native}). |
| @value{GDBN} automatically looks for shared libraries, however if |
| @value{GDBN} does not find yours, you can invoke |
| @code{add-shared-symbol-files}. It takes one argument: the shared |
| library's file name. @code{assf} is a shorthand alias for |
| @code{add-shared-symbol-files}. |
| |
| @kindex section |
| @item section @var{section} @var{addr} |
| The @code{section} command changes the base address of the named |
| @var{section} of the exec file to @var{addr}. This can be used if the |
| exec file does not contain section addresses, (such as in the |
| @code{a.out} format), or when the addresses specified in the file |
| itself are wrong. Each section must be changed separately. The |
| @code{info files} command, described below, lists all the sections and |
| their addresses. |
| |
| @kindex info files |
| @kindex info target |
| @item info files |
| @itemx info target |
| @code{info files} and @code{info target} are synonymous; both print the |
| current target (@pxref{Targets, ,Specifying a Debugging Target}), |
| including the names of the executable and core dump files currently in |
| use by @value{GDBN}, and the files from which symbols were loaded. The |
| command @code{help target} lists all possible targets rather than |
| current ones. |
| |
| @kindex maint info sections |
| @item maint info sections |
| Another command that can give you extra information about program sections |
| is @code{maint info sections}. In addition to the section information |
| displayed by @code{info files}, this command displays the flags and file |
| offset of each section in the executable and core dump files. In addition, |
| @code{maint info sections} provides the following command options (which |
| may be arbitrarily combined): |
| |
| @table @code |
| @item ALLOBJ |
| Display sections for all loaded object files, including shared libraries. |
| @item @var{sections} |
| Display info only for named @var{sections}. |
| @item @var{section-flags} |
| Display info only for sections for which @var{section-flags} are true. |
| The section flags that @value{GDBN} currently knows about are: |
| @table @code |
| @item ALLOC |
| Section will have space allocated in the process when loaded. |
| Set for all sections except those containing debug information. |
| @item LOAD |
| Section will be loaded from the file into the child process memory. |
| Set for pre-initialized code and data, clear for @code{.bss} sections. |
| @item RELOC |
| Section needs to be relocated before loading. |
| @item READONLY |
| Section cannot be modified by the child process. |
| @item CODE |
| Section contains executable code only. |
| @item DATA |
| Section contains data only (no executable code). |
| @item ROM |
| Section will reside in ROM. |
| @item CONSTRUCTOR |
| Section contains data for constructor/destructor lists. |
| @item HAS_CONTENTS |
| Section is not empty. |
| @item NEVER_LOAD |
| An instruction to the linker to not output the section. |
| @item COFF_SHARED_LIBRARY |
| A notification to the linker that the section contains |
| COFF shared library information. |
| @item IS_COMMON |
| Section contains common symbols. |
| @end table |
| @end table |
| @kindex set trust-readonly-sections |
| @cindex read-only sections |
| @item set trust-readonly-sections on |
| Tell @value{GDBN} that readonly sections in your object file |
| really are read-only (i.e.@: that their contents will not change). |
| In that case, @value{GDBN} can fetch values from these sections |
| out of the object file, rather than from the target program. |
| For some targets (notably embedded ones), this can be a significant |
| enhancement to debugging performance. |
| |
| The default is off. |
| |
| @item set trust-readonly-sections off |
| Tell @value{GDBN} not to trust readonly sections. This means that |
| the contents of the section might change while the program is running, |
| and must therefore be fetched from the target when needed. |
| |
| @item show trust-readonly-sections |
| Show the current setting of trusting readonly sections. |
| @end table |
| |
| All file-specifying commands allow both absolute and relative file names |
| as arguments. @value{GDBN} always converts the file name to an absolute file |
| name and remembers it that way. |
| |
| @cindex shared libraries |
| @anchor{Shared Libraries} |
| @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix, |
| and IBM RS/6000 AIX shared libraries. |
| |
| On MS-Windows @value{GDBN} must be linked with the Expat library to support |
| shared libraries. @xref{Expat}. |
| |
| @value{GDBN} automatically loads symbol definitions from shared libraries |
| when you use the @code{run} command, or when you examine a core file. |
| (Before you issue the @code{run} command, @value{GDBN} does not understand |
| references to a function in a shared library, however---unless you are |
| debugging a core file). |
| |
| On HP-UX, if the program loads a library explicitly, @value{GDBN} |
| automatically loads the symbols at the time of the @code{shl_load} call. |
| |
| @c FIXME: some @value{GDBN} release may permit some refs to undef |
| @c FIXME...symbols---eg in a break cmd---assuming they are from a shared |
| @c FIXME...lib; check this from time to time when updating manual |
| |
| There are times, however, when you may wish to not automatically load |
| symbol definitions from shared libraries, such as when they are |
| particularly large or there are many of them. |
| |
| To control the automatic loading of shared library symbols, use the |
| commands: |
| |
| @table @code |
| @kindex set auto-solib-add |
| @item set auto-solib-add @var{mode} |
| If @var{mode} is @code{on}, symbols from all shared object libraries |
| will be loaded automatically when the inferior begins execution, you |
| attach to an independently started inferior, or when the dynamic linker |
| informs @value{GDBN} that a new library has been loaded. If @var{mode} |
| is @code{off}, symbols must be loaded manually, using the |
| @code{sharedlibrary} command. The default value is @code{on}. |
| |
| @cindex memory used for symbol tables |
| If your program uses lots of shared libraries with debug info that |
| takes large amounts of memory, you can decrease the @value{GDBN} |
| memory footprint by preventing it from automatically loading the |
| symbols from shared libraries. To that end, type @kbd{set |
| auto-solib-add off} before running the inferior, then load each |
| library whose debug symbols you do need with @kbd{sharedlibrary |
| @var{regexp}}, where @var{regexp} is a regular expression that matches |
| the libraries whose symbols you want to be loaded. |
| |
| @kindex show auto-solib-add |
| @item show auto-solib-add |
| Display the current autoloading mode. |
| @end table |
| |
| @cindex load shared library |
| To explicitly load shared library symbols, use the @code{sharedlibrary} |
| command: |
| |
| @table @code |
| @kindex info sharedlibrary |
| @kindex info share |
| @item info share @var{regex} |
| @itemx info sharedlibrary @var{regex} |
| Print the names of the shared libraries which are currently loaded |
| that match @var{regex}. If @var{regex} is omitted then print |
| all shared libraries that are loaded. |
| |
| @kindex sharedlibrary |
| @kindex share |
| @item sharedlibrary @var{regex} |
| @itemx share @var{regex} |
| Load shared object library symbols for files matching a |
| Unix regular expression. |
| As with files loaded automatically, it only loads shared libraries |
| required by your program for a core file or after typing @code{run}. If |
| @var{regex} is omitted all shared libraries required by your program are |
| loaded. |
| |
| @item nosharedlibrary |
| @kindex nosharedlibrary |
| @cindex unload symbols from shared libraries |
| Unload all shared object library symbols. This discards all symbols |
| that have been loaded from all shared libraries. Symbols from shared |
| libraries that were loaded by explicit user requests are not |
| discarded. |
| @end table |
| |
| Sometimes you may wish that @value{GDBN} stops and gives you control |
| when any of shared library events happen. The best way to do this is |
| to use @code{catch load} and @code{catch unload} (@pxref{Set |
| Catchpoints}). |
| |
| @value{GDBN} also supports the the @code{set stop-on-solib-events} |
| command for this. This command exists for historical reasons. It is |
| less useful than setting a catchpoint, because it does not allow for |
| conditions or commands as a catchpoint does. |
| |
| @table @code |
| @item set stop-on-solib-events |
| @kindex set stop-on-solib-events |
| This command controls whether @value{GDBN} should give you control |
| when the dynamic linker notifies it about some shared library event. |
| The most common event of interest is loading or unloading of a new |
| shared library. |
| |
| @item show stop-on-solib-events |
| @kindex show stop-on-solib-events |
| Show whether @value{GDBN} stops and gives you control when shared |
| library events happen. |
| @end table |
| |
| Shared libraries are also supported in many cross or remote debugging |
| configurations. @value{GDBN} needs to have access to the target's libraries; |
| this can be accomplished either by providing copies of the libraries |
| on the host system, or by asking @value{GDBN} to automatically retrieve the |
| libraries from the target. If copies of the target libraries are |
| provided, they need to be the same as the target libraries, although the |
| copies on the target can be stripped as long as the copies on the host are |
| not. |
| |
| @cindex where to look for shared libraries |
| For remote debugging, you need to tell @value{GDBN} where the target |
| libraries are, so that it can load the correct copies---otherwise, it |
| may try to load the host's libraries. @value{GDBN} has two variables |
| to specify the search directories for target libraries. |
| |
| @table @code |
| @cindex prefix for shared library file names |
| @cindex system root, alternate |
| @kindex set solib-absolute-prefix |
| @kindex set sysroot |
| @item set sysroot @var{path} |
| Use @var{path} as the system root for the program being debugged. Any |
| absolute shared library paths will be prefixed with @var{path}; many |
| runtime loaders store the absolute paths to the shared library in the |
| target program's memory. If you use @code{set sysroot} to find shared |
| libraries, they need to be laid out in the same way that they are on |
| the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy |
| under @var{path}. |
| |
| If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will |
| retrieve the target libraries from the remote system. This is only |
| supported when using a remote target that supports the @code{remote get} |
| command (@pxref{File Transfer,,Sending files to a remote system}). |
| The part of @var{path} following the initial @file{remote:} |
| (if present) is used as system root prefix on the remote file system. |
| @footnote{If you want to specify a local system root using a directory |
| that happens to be named @file{remote:}, you need to use some equivalent |
| variant of the name like @file{./remote:}.} |
| |
| For targets with an MS-DOS based filesystem, such as MS-Windows and |
| SymbianOS, @value{GDBN} tries prefixing a few variants of the target |
| absolute file name with @var{path}. But first, on Unix hosts, |
| @value{GDBN} converts all backslash directory separators into forward |
| slashes, because the backslash is not a directory separator on Unix: |
| |
| @smallexample |
| c:\foo\bar.dll @result{} c:/foo/bar.dll |
| @end smallexample |
| |
| Then, @value{GDBN} attempts prefixing the target file name with |
| @var{path}, and looks for the resulting file name in the host file |
| system: |
| |
| @smallexample |
| c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll |
| @end smallexample |
| |
| If that does not find the shared library, @value{GDBN} tries removing |
| the @samp{:} character from the drive spec, both for convenience, and, |
| for the case of the host file system not supporting file names with |
| colons: |
| |
| @smallexample |
| c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll |
| @end smallexample |
| |
| This makes it possible to have a system root that mirrors a target |
| with more than one drive. E.g., you may want to setup your local |
| copies of the target system shared libraries like so (note @samp{c} vs |
| @samp{z}): |
| |
| @smallexample |
| @file{/path/to/sysroot/c/sys/bin/foo.dll} |
| @file{/path/to/sysroot/c/sys/bin/bar.dll} |
| @file{/path/to/sysroot/z/sys/bin/bar.dll} |
| @end smallexample |
| |
| @noindent |
| and point the system root at @file{/path/to/sysroot}, so that |
| @value{GDBN} can find the correct copies of both |
| @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}. |
| |
| If that still does not find the shared library, @value{GDBN} tries |
| removing the whole drive spec from the target file name: |
| |
| @smallexample |
| c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll |
| @end smallexample |
| |
| This last lookup makes it possible to not care about the drive name, |
| if you don't want or need to. |
| |
| The @code{set solib-absolute-prefix} command is an alias for @code{set |
| sysroot}. |
| |
| @cindex default system root |
| @cindex @samp{--with-sysroot} |
| You can set the default system root by using the configure-time |
| @samp{--with-sysroot} option. If the system root is inside |
| @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or |
| @samp{--exec-prefix}), then the default system root will be updated |
| automatically if the installed @value{GDBN} is moved to a new |
| location. |
| |
| @kindex show sysroot |
| @item show sysroot |
| Display the current shared library prefix. |
| |
| @kindex set solib-search-path |
| @item set solib-search-path @var{path} |
| If this variable is set, @var{path} is a colon-separated list of |
| directories to search for shared libraries. @samp{solib-search-path} |
| is used after @samp{sysroot} fails to locate the library, or if the |
| path to the library is relative instead of absolute. If you want to |
| use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set |
| @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from |
| finding your host's libraries. @samp{sysroot} is preferred; setting |
| it to a nonexistent directory may interfere with automatic loading |
| of shared library symbols. |
| |
| @kindex show solib-search-path |
| @item show solib-search-path |
| Display the current shared library search path. |
| |
| @cindex DOS file-name semantics of file names. |
| @kindex set target-file-system-kind (unix|dos-based|auto) |
| @kindex show target-file-system-kind |
| @item set target-file-system-kind @var{kind} |
| Set assumed file system kind for target reported file names. |
| |
| Shared library file names as reported by the target system may not |
| make sense as is on the system @value{GDBN} is running on. For |
| example, when remote debugging a target that has MS-DOS based file |
| system semantics, from a Unix host, the target may be reporting to |
| @value{GDBN} a list of loaded shared libraries with file names such as |
| @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of |
| drive letters, so the @samp{c:\} prefix is not normally understood as |
| indicating an absolute file name, and neither is the backslash |
| normally considered a directory separator character. In that case, |
| the native file system would interpret this whole absolute file name |
| as a relative file name with no directory components. This would make |
| it impossible to point @value{GDBN} at a copy of the remote target's |
| shared libraries on the host using @code{set sysroot}, and impractical |
| with @code{set solib-search-path}. Setting |
| @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN} |
| to interpret such file names similarly to how the target would, and to |
| map them to file names valid on @value{GDBN}'s native file system |
| semantics. The value of @var{kind} can be @code{"auto"}, in addition |
| to one of the supported file system kinds. In that case, @value{GDBN} |
| tries to determine the appropriate file system variant based on the |
| current target's operating system (@pxref{ABI, ,Configuring the |
| Current ABI}). The supported file system settings are: |
| |
| @table @code |
| @item unix |
| Instruct @value{GDBN} to assume the target file system is of Unix |
| kind. Only file names starting the forward slash (@samp{/}) character |
| are considered absolute, and the directory separator character is also |
| the forward slash. |
| |
| @item dos-based |
| Instruct @value{GDBN} to assume the target file system is DOS based. |
| File names starting with either a forward slash, or a drive letter |
| followed by a colon (e.g., @samp{c:}), are considered absolute, and |
| both the slash (@samp{/}) and the backslash (@samp{\\}) characters are |
| considered directory separators. |
| |
| @item auto |
| Instruct @value{GDBN} to use the file system kind associated with the |
| target operating system (@pxref{ABI, ,Configuring the Current ABI}). |
| This is the default. |
| @end table |
| @end table |
| |
| @cindex file name canonicalization |
| @cindex base name differences |
| When processing file names provided by the user, @value{GDBN} |
| frequently needs to compare them to the file names recorded in the |
| program's debug info. Normally, @value{GDBN} compares just the |
| @dfn{base names} of the files as strings, which is reasonably fast |
| even for very large programs. (The base name of a file is the last |
| portion of its name, after stripping all the leading directories.) |
| This shortcut in comparison is based upon the assumption that files |
| cannot have more than one base name. This is usually true, but |
| references to files that use symlinks or similar filesystem |
| facilities violate that assumption. If your program records files |
| using such facilities, or if you provide file names to @value{GDBN} |
| using symlinks etc., you can set @code{basenames-may-differ} to |
| @code{true} to instruct @value{GDBN} to completely canonicalize each |
| pair of file names it needs to compare. This will make file-name |
| comparisons accurate, but at a price of a significant slowdown. |
| |
| @table @code |
| @item set basenames-may-differ |
| @kindex set basenames-may-differ |
| Set whether a source file may have multiple base names. |
| |
| @item show basenames-may-differ |
| @kindex show basenames-may-differ |
| Show whether a source file may have multiple base names. |
| @end table |
| |
| @node Separate Debug Files |
| @section Debugging Information in Separate Files |
| @cindex separate debugging information files |
| @cindex debugging information in separate files |
| @cindex @file{.debug} subdirectories |
| @cindex debugging information directory, global |
| @cindex global debugging information directories |
| @cindex build ID, and separate debugging files |
| @cindex @file{.build-id} directory |
| |
| @value{GDBN} allows you to put a program's debugging information in a |
| file separate from the executable itself, in a way that allows |
| @value{GDBN} to find and load the debugging information automatically. |
| Since debugging information can be very large---sometimes larger |
| than the executable code itself---some systems distribute debugging |
| information for their executables in separate files, which users can |
| install only when they need to debug a problem. |
| |
| @value{GDBN} supports two ways of specifying the separate debug info |
| file: |
| |
| @itemize @bullet |
| @item |
| The executable contains a @dfn{debug link} that specifies the name of |
| the separate debug info file. The separate debug file's name is |
| usually @file{@var{executable}.debug}, where @var{executable} is the |
| name of the corresponding executable file without leading directories |
| (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the |
| debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC) |
| checksum for the debug file, which @value{GDBN} uses to validate that |
| the executable and the debug file came from the same build. |
| |
| @item |
| The executable contains a @dfn{build ID}, a unique bit string that is |
| also present in the corresponding debug info file. (This is supported |
| only on some operating systems, notably those which use the ELF format |
| for binary files and the @sc{gnu} Binutils.) For more details about |
| this feature, see the description of the @option{--build-id} |
| command-line option in @ref{Options, , Command Line Options, ld.info, |
| The GNU Linker}. The debug info file's name is not specified |
| explicitly by the build ID, but can be computed from the build ID, see |
| below. |
| @end itemize |
| |
| Depending on the way the debug info file is specified, @value{GDBN} |
| uses two different methods of looking for the debug file: |
| |
| @itemize @bullet |
| @item |
| For the ``debug link'' method, @value{GDBN} looks up the named file in |
| the directory of the executable file, then in a subdirectory of that |
| directory named @file{.debug}, and finally under each one of the global debug |
| directories, in a subdirectory whose name is identical to the leading |
| directories of the executable's absolute file name. |
| |
| @item |
| For the ``build ID'' method, @value{GDBN} looks in the |
| @file{.build-id} subdirectory of each one of the global debug directories for |
| a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the |
| first 2 hex characters of the build ID bit string, and @var{nnnnnnnn} |
| are the rest of the bit string. (Real build ID strings are 32 or more |
| hex characters, not 10.) |
| @end itemize |
| |
| So, for example, suppose you ask @value{GDBN} to debug |
| @file{/usr/bin/ls}, which has a debug link that specifies the |
| file @file{ls.debug}, and a build ID whose value in hex is |
| @code{abcdef1234}. If the list of the global debug directories includes |
| @file{/usr/lib/debug}, then @value{GDBN} will look for the following |
| debug information files, in the indicated order: |
| |
| @itemize @minus |
| @item |
| @file{/usr/lib/debug/.build-id/ab/cdef1234.debug} |
| @item |
| @file{/usr/bin/ls.debug} |
| @item |
| @file{/usr/bin/.debug/ls.debug} |
| @item |
| @file{/usr/lib/debug/usr/bin/ls.debug}. |
| @end itemize |
| |
| @anchor{debug-file-directory} |
| Global debugging info directories default to what is set by @value{GDBN} |
| configure option @option{--with-separate-debug-dir}. During @value{GDBN} run |
| you can also set the global debugging info directories, and view the list |
| @value{GDBN} is currently using. |
| |
| @table @code |
| |
| @kindex set debug-file-directory |
| @item set debug-file-directory @var{directories} |
| Set the directories which @value{GDBN} searches for separate debugging |
| information files to @var{directory}. Multiple path components can be set |
| concatenating them by a path separator. |
| |
| @kindex show debug-file-directory |
| @item show debug-file-directory |
| Show the directories @value{GDBN} searches for separate debugging |
| information files. |
| |
| @end table |
| |
| @cindex @code{.gnu_debuglink} sections |
| @cindex debug link sections |
| A debug link is a special section of the executable file named |
| @code{.gnu_debuglink}. The section must contain: |
| |
| @itemize |
| @item |
| A filename, with any leading directory components removed, followed by |
| a zero byte, |
| @item |
| zero to three bytes of padding, as needed to reach the next four-byte |
| boundary within the section, and |
| @item |
| a four-byte CRC checksum, stored in the same endianness used for the |
| executable file itself. The checksum is computed on the debugging |
| information file's full contents by the function given below, passing |
| zero as the @var{crc} argument. |
| @end itemize |
| |
| Any executable file format can carry a debug link, as long as it can |
| contain a section named @code{.gnu_debuglink} with the contents |
| described above. |
| |
| @cindex @code{.note.gnu.build-id} sections |
| @cindex build ID sections |
| The build ID is a special section in the executable file (and in other |
| ELF binary files that @value{GDBN} may consider). This section is |
| often named @code{.note.gnu.build-id}, but that name is not mandatory. |
| It contains unique identification for the built files---the ID remains |
| the same across multiple builds of the same build tree. The default |
| algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the |
| content for the build ID string. The same section with an identical |
| value is present in the original built binary with symbols, in its |
| stripped variant, and in the separate debugging information file. |
| |
| The debugging information file itself should be an ordinary |
| executable, containing a full set of linker symbols, sections, and |
| debugging information. The sections of the debugging information file |
| should have the same names, addresses, and sizes as the original file, |
| but they need not contain any data---much like a @code{.bss} section |
| in an ordinary executable. |
| |
| The @sc{gnu} binary utilities (Binutils) package includes the |
| @samp{objcopy} utility that can produce |
| the separated executable / debugging information file pairs using the |
| following commands: |
| |
| @smallexample |
| @kbd{objcopy --only-keep-debug foo foo.debug} |
| @kbd{strip -g foo} |
| @end smallexample |
| |
| @noindent |
| These commands remove the debugging |
| information from the executable file @file{foo} and place it in the file |
| @file{foo.debug}. You can use the first, second or both methods to link the |
| two files: |
| |
| @itemize @bullet |
| @item |
| The debug link method needs the following additional command to also leave |
| behind a debug link in @file{foo}: |
| |
| @smallexample |
| @kbd{objcopy --add-gnu-debuglink=foo.debug foo} |
| @end smallexample |
| |
| Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains |
| a version of the @code{strip} command such that the command @kbd{strip foo -f |
| foo.debug} has the same functionality as the two @code{objcopy} commands and |
| the @code{ln -s} command above, together. |
| |
| @item |
| Build ID gets embedded into the main executable using @code{ld --build-id} or |
| the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus |
| compatibility fixes for debug files separation are present in @sc{gnu} binary |
| utilities (Binutils) package since version 2.18. |
| @end itemize |
| |
| @noindent |
| |
| @cindex CRC algorithm definition |
| The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in |
| IEEE 802.3 using the polynomial: |
| |
| @c TexInfo requires naked braces for multi-digit exponents for Tex |
| @c output, but this causes HTML output to barf. HTML has to be set using |
| @c raw commands. So we end up having to specify this equation in 2 |
| @c different ways! |
| @ifhtml |
| @display |
| @html |
| <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup> |
| + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1 |
| @end html |
| @end display |
| @end ifhtml |
| @ifnothtml |
| @display |
| @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}} |
| @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1} |
| @end display |
| @end ifnothtml |
| |
| The function is computed byte at a time, taking the least |
| significant bit of each byte first. The initial pattern |
| @code{0xffffffff} is used, to ensure leading zeros affect the CRC and |
| the final result is inverted to ensure trailing zeros also affect the |
| CRC. |
| |
| @emph{Note:} This is the same CRC polynomial as used in handling the |
| @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol, |
| , @value{GDBN} Remote Serial Protocol}). However in the |
| case of the Remote Serial Protocol, the CRC is computed @emph{most} |
| significant bit first, and the result is not inverted, so trailing |
| zeros have no effect on the CRC value. |
| |
| To complete the description, we show below the code of the function |
| which produces the CRC used in @code{.gnu_debuglink}. Inverting the |
| initially supplied @code{crc} argument means that an initial call to |
| this function passing in zero will start computing the CRC using |
| @code{0xffffffff}. |
| |
| @kindex gnu_debuglink_crc32 |
| @smallexample |
| unsigned long |
| gnu_debuglink_crc32 (unsigned long crc, |
| unsigned char *buf, size_t len) |
| @{ |
| static const unsigned long crc32_table[256] = |
| @{ |
| 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, |
| 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, |
| 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, |
| 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, |
| 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, |
| 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, |
| 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, |
| 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, |
| 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, |
| 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a, |
| 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, |
| 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, |
| 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, |
| 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, |
| 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e, |
| 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, |
| 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, |
| 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, |
| 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, |
| 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, |
| 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, |
| 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, |
| 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010, |
| 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, |
| 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, |
| 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, |
| 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, |
| 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, |
| 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344, |
| 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, |
| 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, |
| 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, |
| 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, |
| 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c, |
| 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, |
| 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, |
| 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, |
| 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, |
| 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, |
| 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, |
| 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, |
| 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242, |
| 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, |
| 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, |
| 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278, |
| 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, |
| 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, |
| 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, |
| 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, |
| 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, |
| 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, |
| 0x2d02ef8d |
| @}; |
| unsigned char *end; |
| |
| crc = ~crc & 0xffffffff; |
| for (end = buf + len; buf < end; ++buf) |
| crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8); |
| return ~crc & 0xffffffff; |
| @} |
| @end smallexample |
| |
| @noindent |
| This computation does not apply to the ``build ID'' method. |
| |
| |
| @node Index Files |
| @section Index Files Speed Up @value{GDBN} |
| @cindex index files |
| @cindex @samp{.gdb_index} section |
| |
| When @value{GDBN} finds a symbol file, it scans the symbols in the |
| file in order to construct an internal symbol table. This lets most |
| @value{GDBN} operations work quickly---at the cost of a delay early |
| on. For large programs, this delay can be quite lengthy, so |
| @value{GDBN} provides a way to build an index, which speeds up |
| startup. |
| |
| The index is stored as a section in the symbol file. @value{GDBN} can |
| write the index to a file, then you can put it into the symbol file |
| using @command{objcopy}. |
| |
| To create an index file, use the @code{save gdb-index} command: |
| |
| @table @code |
| @item save gdb-index @var{directory} |
| @kindex save gdb-index |
| Create an index file for each symbol file currently known by |
| @value{GDBN}. Each file is named after its corresponding symbol file, |
| with @samp{.gdb-index} appended, and is written into the given |
| @var{directory}. |
| @end table |
| |
| Once you have created an index file you can merge it into your symbol |
| file, here named @file{symfile}, using @command{objcopy}: |
| |
| @smallexample |
| $ objcopy --add-section .gdb_index=symfile.gdb-index \ |
| --set-section-flags .gdb_index=readonly symfile symfile |
| @end smallexample |
| |
| @value{GDBN} will normally ignore older versions of @file{.gdb_index} |
| sections that have been deprecated. Usually they are deprecated because |
| they are missing a new feature or have performance issues. |
| To tell @value{GDBN} to use a deprecated index section anyway |
| specify @code{set use-deprecated-index-sections on}. |
| The default is @code{off}. |
| This can speed up startup, but may result in some functionality being lost. |
| @xref{Index Section Format}. |
| |
| @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on} |
| must be done before gdb reads the file. The following will not work: |
| |
| @smallexample |
| $ gdb -ex "set use-deprecated-index-sections on" <program> |
| @end smallexample |
| |
| Instead you must do, for example, |
| |
| @smallexample |
| $ gdb -iex "set use-deprecated-index-sections on" <program> |
| @end smallexample |
| |
| There are currently some limitation on indices. They only work when |
| for DWARF debugging information, not stabs. And, they do not |
| currently work for programs using Ada. |
| |
| @node Symbol Errors |
| @section Errors Reading Symbol Files |
| |
| While reading a symbol file, @value{GDBN} occasionally encounters problems, |
| such as symbol types it does not recognize, or known bugs in compiler |
| output. By default, @value{GDBN} does not notify you of such problems, since |
| they are relatively common and primarily of interest to people |
| debugging compilers. If you are interested in seeing information |
| about ill-constructed symbol tables, you can either ask @value{GDBN} to print |
| only one message about each such type of problem, no matter how many |
| times the problem occurs; or you can ask @value{GDBN} to print more messages, |
| to see how many times the problems occur, with the @code{set |
| complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and |
| Messages}). |
| |
| The messages currently printed, and their meanings, include: |
| |
| @table @code |
| @item inner block not inside outer block in @var{symbol} |
| |
| The symbol information shows where symbol scopes begin and end |
| (such as at the start of a function or a block of statements). This |
| error indicates that an inner scope block is not fully contained |
| in its outer scope blocks. |
| |
| @value{GDBN} circumvents the problem by treating the inner block as if it had |
| the same scope as the outer block. In the error message, @var{symbol} |
| may be shown as ``@code{(don't know)}'' if the outer block is not a |
| function. |
| |
| @item block at @var{address} out of order |
| |
| The symbol information for symbol scope blocks should occur in |
| order of increasing addresses. This error indicates that it does not |
| do so. |
| |
| @value{GDBN} does not circumvent this problem, and has trouble |
| locating symbols in the source file whose symbols it is reading. (You |
| can often determine what source file is affected by specifying |
| @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and |
| Messages}.) |
| |
| @item bad block start address patched |
| |
| The symbol information for a symbol scope block has a start address |
| smaller than the address of the preceding source line. This is known |
| to occur in the SunOS 4.1.1 (and earlier) C compiler. |
| |
| @value{GDBN} circumvents the problem by treating the symbol scope block as |
| starting on the previous source line. |
| |
| @item bad string table offset in symbol @var{n} |
| |
| @cindex foo |
| Symbol number @var{n} contains a pointer into the string table which is |
| larger than the size of the string table. |
| |
| @value{GDBN} circumvents the problem by considering the symbol to have the |
| name @code{foo}, which may cause other problems if many symbols end up |
| with this name. |
| |
| @item unknown symbol type @code{0x@var{nn}} |
| |
| The symbol information contains new data types that @value{GDBN} does |
| not yet know how to read. @code{0x@var{nn}} is the symbol type of the |
| uncomprehended information, in hexadecimal. |
| |
| @value{GDBN} circumvents the error by ignoring this symbol information. |
| This usually allows you to debug your program, though certain symbols |
| are not accessible. If you encounter such a problem and feel like |
| debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint |
| on @code{complain}, then go up to the function @code{read_dbx_symtab} |
| and examine @code{*bufp} to see the symbol. |
| |
| @item stub type has NULL name |
| |
| @value{GDBN} could not find the full definition for a struct or class. |
| |
| @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{} |
| The symbol information for a C@t{++} member function is missing some |
| information that recent versions of the compiler should have output for |
| it. |
| |
| @item info mismatch between compiler and debugger |
| |
| @value{GDBN} could not parse a type specification output by the compiler. |
| |
| @end table |
| |
| @node Data Files |
| @section GDB Data Files |
| |
| @cindex prefix for data files |
| @value{GDBN} will sometimes read an auxiliary data file. These files |
| are kept in a directory known as the @dfn{data directory}. |
| |
| You can set the data directory's name, and view the name @value{GDBN} |
| is currently using. |
| |
| @table @code |
| @kindex set data-directory |
| @item set data-directory @var{directory} |
| Set the directory which @value{GDBN} searches for auxiliary data files |
| to @var{directory}. |
| |
| @kindex show data-directory |
| @item show data-directory |
| Show the directory @value{GDBN} searches for auxiliary data files. |
| @end table |
| |
| @cindex default data directory |
| @cindex @samp{--with-gdb-datadir} |
| You can set the default data directory by using the configure-time |
| @samp{--with-gdb-datadir} option. If the data directory is inside |
| @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or |
| @samp{--exec-prefix}), then the default data directory will be updated |
| automatically if the installed @value{GDBN} is moved to a new |
| location. |
| |
| The data directory may also be specified with the |
| @code{--data-directory} command line option. |
| @xref{Mode Options}. |
| |
| @node Targets |
| @chapter Specifying a Debugging Target |
| |
| @cindex debugging target |
| A @dfn{target} is the execution environment occupied by your program. |
| |
| Often, @value{GDBN} runs in the same host environment as your program; |
| in that case, the debugging target is specified as a side effect when |
| you use the @code{file} or @code{core} commands. When you need more |
| flexibility---for example, running @value{GDBN} on a physically separate |
| host, or controlling a standalone system over a serial port or a |
| realtime system over a TCP/IP connection---you can use the @code{target} |
| command to specify one of the target types configured for @value{GDBN} |
| (@pxref{Target Commands, ,Commands for Managing Targets}). |
| |
| @cindex target architecture |
| It is possible to build @value{GDBN} for several different @dfn{target |
| architectures}. When @value{GDBN} is built like that, you can choose |
| one of the available architectures with the @kbd{set architecture} |
| command. |
| |
| @table @code |
| @kindex set architecture |
| @kindex show architecture |
| @item set architecture @var{arch} |
| This command sets the current target architecture to @var{arch}. The |
| value of @var{arch} can be @code{"auto"}, in addition to one of the |
| supported architectures. |
| |
| @item show architecture |
| Show the current target architecture. |
| |
| @item set processor |
| @itemx processor |
| @kindex set processor |
| @kindex show processor |
| These are alias commands for, respectively, @code{set architecture} |
| and @code{show architecture}. |
| @end table |
| |
| @menu |
| * Active Targets:: Active targets |
| * Target Commands:: Commands for managing targets |
| * Byte Order:: Choosing target byte order |
| @end menu |
| |
| @node Active Targets |
| @section Active Targets |
| |
| @cindex stacking targets |
| @cindex active targets |
| @cindex multiple targets |
| |
| There are multiple classes of targets such as: processes, executable files or |
| recording sessions. Core files belong to the process class, making core file |
| and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently |
| on multiple active targets, one in each class. This allows you to (for |
| example) start a process and inspect its activity, while still having access to |
| the executable file after the process finishes. Or if you start process |
| recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are |
| presented a virtual layer of the recording target, while the process target |
| remains stopped at the chronologically last point of the process execution. |
| |
| Use the @code{core-file} and @code{exec-file} commands to select a new core |
| file or executable target (@pxref{Files, ,Commands to Specify Files}). To |
| specify as a target a process that is already running, use the @code{attach} |
| command (@pxref{Attach, ,Debugging an Already-running Process}). |
| |
| @node Target Commands |
| @section Commands for Managing Targets |
| |
| @table @code |
| @item target @var{type} @var{parameters} |
| Connects the @value{GDBN} host environment to a target machine or |
| process. A target is typically a protocol for talking to debugging |
| facilities. You use the argument @var{type} to specify the type or |
| protocol of the target machine. |
| |
| Further @var{parameters} are interpreted by the target protocol, but |
| typically include things like device names or host names to connect |
| with, process numbers, and baud rates. |
| |
| The @code{target} command does not repeat if you press @key{RET} again |
| after executing the command. |
| |
| @kindex help target |
| @item help target |
| Displays the names of all targets available. To display targets |
| currently selected, use either @code{info target} or @code{info files} |
| (@pxref{Files, ,Commands to Specify Files}). |
| |
| @item help target @var{name} |
| Describe a particular target, including any parameters necessary to |
| select it. |
| |
| @kindex set gnutarget |
| @item set gnutarget @var{args} |
| @value{GDBN} uses its own library BFD to read your files. @value{GDBN} |
| knows whether it is reading an @dfn{executable}, |
| a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format |
| with the @code{set gnutarget} command. Unlike most @code{target} commands, |
| with @code{gnutarget} the @code{target} refers to a program, not a machine. |
| |
| @quotation |
| @emph{Warning:} To specify a file format with @code{set gnutarget}, |
| you must know the actual BFD name. |
| @end quotation |
| |
| @noindent |
| @xref{Files, , Commands to Specify Files}. |
| |
| @kindex show gnutarget |
| @item show gnutarget |
| Use the @code{show gnutarget} command to display what file format |
| @code{gnutarget} is set to read. If you have not set @code{gnutarget}, |
| @value{GDBN} will determine the file format for each file automatically, |
| and @code{show gnutarget} displays @samp{The current BDF target is "auto"}. |
| @end table |
| |
| @cindex common targets |
| Here are some common targets (available, or not, depending on the GDB |
| configuration): |
| |
| @table @code |
| @kindex target |
| @item target exec @var{program} |
| @cindex executable file target |
| An executable file. @samp{target exec @var{program}} is the same as |
| @samp{exec-file @var{program}}. |
| |
| @item target core @var{filename} |
| @cindex core dump file target |
| A core dump file. @samp{target core @var{filename}} is the same as |
| @samp{core-file @var{filename}}. |
| |
| @item target remote @var{medium} |
| @cindex remote target |
| A remote system connected to @value{GDBN} via a serial line or network |
| connection. This command tells @value{GDBN} to use its own remote |
| protocol over @var{medium} for debugging. @xref{Remote Debugging}. |
| |
| For example, if you have a board connected to @file{/dev/ttya} on the |
| machine running @value{GDBN}, you could say: |
| |
| @smallexample |
| target remote /dev/ttya |
| @end smallexample |
| |
| @code{target remote} supports the @code{load} command. This is only |
| useful if you have some other way of getting the stub to the target |
| system, and you can put it somewhere in memory where it won't get |
| clobbered by the download. |
| |
| @item target sim @r{[}@var{simargs}@r{]} @dots{} |
| @cindex built-in simulator target |
| Builtin CPU simulator. @value{GDBN} includes simulators for most architectures. |
| In general, |
| @smallexample |
| target sim |
| load |
| run |
| @end smallexample |
| @noindent |
| works; however, you cannot assume that a specific memory map, device |
| drivers, or even basic I/O is available, although some simulators do |
| provide these. For info about any processor-specific simulator details, |
| see the appropriate section in @ref{Embedded Processors, ,Embedded |
| Processors}. |
| |
| @end table |
| |
| Some configurations may include these targets as well: |
| |
| @table @code |
| |
| @item target nrom @var{dev} |
| @cindex NetROM ROM emulator target |
| NetROM ROM emulator. This target only supports downloading. |
| |
| @end table |
| |
| Different targets are available on different configurations of @value{GDBN}; |
| your configuration may have more or fewer targets. |
| |
| Many remote targets require you to download the executable's code once |
| you've successfully established a connection. You may wish to control |
| various aspects of this process. |
| |
| @table @code |
| |
| @item set hash |
| @kindex set hash@r{, for remote monitors} |
| @cindex hash mark while downloading |
| This command controls whether a hash mark @samp{#} is displayed while |
| downloading a file to the remote monitor. If on, a hash mark is |
| displayed after each S-record is successfully downloaded to the |
| monitor. |
| |
| @item show hash |
| @kindex show hash@r{, for remote monitors} |
| Show the current status of displaying the hash mark. |
| |
| @item set debug monitor |
| @kindex set debug monitor |
| @cindex display remote monitor communications |
| Enable or disable display of communications messages between |
| @value{GDBN} and the remote monitor. |
| |
| @item show debug monitor |
| @kindex show debug monitor |
| Show the current status of displaying communications between |
| @value{GDBN} and the remote monitor. |
| @end table |
| |
| @table @code |
| |
| @kindex load @var{filename} |
| @item load @var{filename} |
| @anchor{load} |
| Depending on what remote debugging facilities are configured into |
| @value{GDBN}, the @code{load} command may be available. Where it exists, it |
| is meant to make @var{filename} (an executable) available for debugging |
| on the remote system---by downloading, or dynamic linking, for example. |
| @code{load} also records the @var{filename} symbol table in @value{GDBN}, like |
| the @code{add-symbol-file} command. |
| |
| If your @value{GDBN} does not have a @code{load} command, attempting to |
| execute it gets the error message ``@code{You can't do that when your |
| target is @dots{}}'' |
| |
| The file is loaded at whatever address is specified in the executable. |
| For some object file formats, you can specify the load address when you |
| link the program; for other formats, like a.out, the object file format |
| specifies a fixed address. |
| @c FIXME! This would be a good place for an xref to the GNU linker doc. |
| |
| Depending on the remote side capabilities, @value{GDBN} may be able to |
| load programs into flash memory. |
| |
| @code{load} does not repeat if you press @key{RET} again after using it. |
| @end table |
| |
| @node Byte Order |
| @section Choosing Target Byte Order |
| |
| @cindex choosing target byte order |
| @cindex target byte order |
| |
| Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH, |
| offer the ability to run either big-endian or little-endian byte |
| orders. Usually the executable or symbol will include a bit to |
| designate the endian-ness, and you will not need to worry about |
| which to use. However, you may still find it useful to adjust |
| @value{GDBN}'s idea of processor endian-ness manually. |
| |
| @table @code |
| @kindex set endian |
| @item set endian big |
| Instruct @value{GDBN} to assume the target is big-endian. |
| |
| @item set endian little |
| Instruct @value{GDBN} to assume the target is little-endian. |
| |
| @item set endian auto |
| Instruct @value{GDBN} to use the byte order associated with the |
| executable. |
| |
| @item show endian |
| Display @value{GDBN}'s current idea of the target byte order. |
| |
| @end table |
| |
| Note that these commands merely adjust interpretation of symbolic |
| data on the host, and that they have absolutely no effect on the |
| target system. |
| |
| |
| @node Remote Debugging |
| @chapter Debugging Remote Programs |
| @cindex remote debugging |
| |
| If you are trying to debug a program running on a machine that cannot run |
| @value{GDBN} in the usual way, it is often useful to use remote debugging. |
| For example, you might use remote debugging on an operating system kernel, |
| or on a small system which does not have a general purpose operating system |
| powerful enough to run a full-featured debugger. |
| |
| Some configurations of @value{GDBN} have special serial or TCP/IP interfaces |
| to make this work with particular debugging targets. In addition, |
| @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN}, |
| but not specific to any particular target system) which you can use if you |
| write the remote stubs---the code that runs on the remote system to |
| communicate with @value{GDBN}. |
| |
| Other remote targets may be available in your |
| configuration of @value{GDBN}; use @code{help target} to list them. |
| |
| @menu |
| * Connecting:: Connecting to a remote target |
| * File Transfer:: Sending files to a remote system |
| * Server:: Using the gdbserver program |
| * Remote Configuration:: Remote configuration |
| * Remote Stub:: Implementing a remote stub |
| @end menu |
| |
| @node Connecting |
| @section Connecting to a Remote Target |
| |
| On the @value{GDBN} host machine, you will need an unstripped copy of |
| your program, since @value{GDBN} needs symbol and debugging information. |
| Start up @value{GDBN} as usual, using the name of the local copy of your |
| program as the first argument. |
| |
| @cindex @code{target remote} |
| @value{GDBN} can communicate with the target over a serial line, or |
| over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In |
| each case, @value{GDBN} uses the same protocol for debugging your |
| program; only the medium carrying the debugging packets varies. The |
| @code{target remote} command establishes a connection to the target. |
| Its arguments indicate which medium to use: |
| |
| @table @code |
| |
| @item target remote @var{serial-device} |
| @cindex serial line, @code{target remote} |
| Use @var{serial-device} to communicate with the target. For example, |
| to use a serial line connected to the device named @file{/dev/ttyb}: |
| |
| @smallexample |
| target remote /dev/ttyb |
| @end smallexample |
| |
| If you're using a serial line, you may want to give @value{GDBN} the |
| @w{@samp{--baud}} option, or use the @code{set remotebaud} command |
| (@pxref{Remote Configuration, set remotebaud}) before the |
| @code{target} command. |
| |
| @item target remote @code{@var{host}:@var{port}} |
| @itemx target remote @code{tcp:@var{host}:@var{port}} |
| @cindex @acronym{TCP} port, @code{target remote} |
| Debug using a @acronym{TCP} connection to @var{port} on @var{host}. |
| The @var{host} may be either a host name or a numeric @acronym{IP} |
| address; @var{port} must be a decimal number. The @var{host} could be |
| the target machine itself, if it is directly connected to the net, or |
| it might be a terminal server which in turn has a serial line to the |
| target. |
| |
| For example, to connect to port 2828 on a terminal server named |
| @code{manyfarms}: |
| |
| @smallexample |
| target remote manyfarms:2828 |
| @end smallexample |
| |
| If your remote target is actually running on the same machine as your |
| debugger session (e.g.@: a simulator for your target running on the |
| same host), you can omit the hostname. For example, to connect to |
| port 1234 on your local machine: |
| |
| @smallexample |
| target remote :1234 |
| @end smallexample |
| @noindent |
| |
| Note that the colon is still required here. |
| |
| @item target remote @code{udp:@var{host}:@var{port}} |
| @cindex @acronym{UDP} port, @code{target remote} |
| Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to |
| connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}: |
| |
| @smallexample |
| target remote udp:manyfarms:2828 |
| @end smallexample |
| |
| When using a @acronym{UDP} connection for remote debugging, you should |
| keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP} |
| can silently drop packets on busy or unreliable networks, which will |
| cause havoc with your debugging session. |
| |
| @item target remote | @var{command} |
| @cindex pipe, @code{target remote} to |
| Run @var{command} in the background and communicate with it using a |
| pipe. The @var{command} is a shell command, to be parsed and expanded |
| by the system's command shell, @code{/bin/sh}; it should expect remote |
| protocol packets on its standard input, and send replies on its |
| standard output. You could use this to run a stand-alone simulator |
| that speaks the remote debugging protocol, to make net connections |
| using programs like @code{ssh}, or for other similar tricks. |
| |
| If @var{command} closes its standard output (perhaps by exiting), |
| @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the |
| program has already exited, this will have no effect.) |
| |
| @end table |
| |
| Once the connection has been established, you can use all the usual |
| commands to examine and change data. The remote program is already |
| running; you can use @kbd{step} and @kbd{continue}, and you do not |
| need to use @kbd{run}. |
| |
| @cindex interrupting remote programs |
| @cindex remote programs, interrupting |
| Whenever @value{GDBN} is waiting for the remote program, if you type the |
| interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the |
| program. This may or may not succeed, depending in part on the hardware |
| and the serial drivers the remote system uses. If you type the |
| interrupt character once again, @value{GDBN} displays this prompt: |
| |
| @smallexample |
| Interrupted while waiting for the program. |
| Give up (and stop debugging it)? (y or n) |
| @end smallexample |
| |
| If you type @kbd{y}, @value{GDBN} abandons the remote debugging session. |
| (If you decide you want to try again later, you can use @samp{target |
| remote} again to connect once more.) If you type @kbd{n}, @value{GDBN} |
| goes back to waiting. |
| |
| @table @code |
| @kindex detach (remote) |
| @item detach |
| When you have finished debugging the remote program, you can use the |
| @code{detach} command to release it from @value{GDBN} control. |
| Detaching from the target normally resumes its execution, but the results |
| will depend on your particular remote stub. After the @code{detach} |
| command, @value{GDBN} is free to connect to another target. |
| |
| @kindex disconnect |
| @item disconnect |
| The @code{disconnect} command behaves like @code{detach}, except that |
| the target is generally not resumed. It will wait for @value{GDBN} |
| (this instance or another one) to connect and continue debugging. After |
| the @code{disconnect} command, @value{GDBN} is again free to connect to |
| another target. |
| |
| @cindex send command to remote monitor |
| @cindex extend @value{GDBN} for remote targets |
| @cindex add new commands for external monitor |
| @kindex monitor |
| @item monitor @var{cmd} |
| This command allows you to send arbitrary commands directly to the |
| remote monitor. Since @value{GDBN} doesn't care about the commands it |
| sends like this, this command is the way to extend @value{GDBN}---you |
| can add new commands that only the external monitor will understand |
| and implement. |
| @end table |
| |
| @node File Transfer |
| @section Sending files to a remote system |
| @cindex remote target, file transfer |
| @cindex file transfer |
| @cindex sending files to remote systems |
| |
| Some remote targets offer the ability to transfer files over the same |
| connection used to communicate with @value{GDBN}. This is convenient |
| for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems |
| running @code{gdbserver} over a network interface. For other targets, |
| e.g.@: embedded devices with only a single serial port, this may be |
| the only way to upload or download files. |
| |
| Not all remote targets support these commands. |
| |
| @table @code |
| @kindex remote put |
| @item remote put @var{hostfile} @var{targetfile} |
| Copy file @var{hostfile} from the host system (the machine running |
| @value{GDBN}) to @var{targetfile} on the target system. |
| |
| @kindex remote get |
| @item remote get @var{targetfile} @var{hostfile} |
| Copy file @var{targetfile} from the target system to @var{hostfile} |
| on the host system. |
| |
| @kindex remote delete |
| @item remote delete @var{targetfile} |
| Delete @var{targetfile} from the target system. |
| |
| @end table |
| |
| @node Server |
| @section Using the @code{gdbserver} Program |
| |
| @kindex gdbserver |
| @cindex remote connection without stubs |
| @code{gdbserver} is a control program for Unix-like systems, which |
| allows you to connect your program with a remote @value{GDBN} via |
| @code{target remote}---but without linking in the usual debugging stub. |
| |
| @code{gdbserver} is not a complete replacement for the debugging stubs, |
| because it requires essentially the same operating-system facilities |
| that @value{GDBN} itself does. In fact, a system that can run |
| @code{gdbserver} to connect to a remote @value{GDBN} could also run |
| @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless, |
| because it is a much smaller program than @value{GDBN} itself. It is |
| also easier to port than all of @value{GDBN}, so you may be able to get |
| started more quickly on a new system by using @code{gdbserver}. |
| Finally, if you develop code for real-time systems, you may find that |
| the tradeoffs involved in real-time operation make it more convenient to |
| do as much development work as possible on another system, for example |
| by cross-compiling. You can use @code{gdbserver} to make a similar |
| choice for debugging. |
| |
| @value{GDBN} and @code{gdbserver} communicate via either a serial line |
| or a TCP connection, using the standard @value{GDBN} remote serial |
| protocol. |
| |
| @quotation |
| @emph{Warning:} @code{gdbserver} does not have any built-in security. |
| Do not run @code{gdbserver} connected to any public network; a |
| @value{GDBN} connection to @code{gdbserver} provides access to the |
| target system with the same privileges as the user running |
| @code{gdbserver}. |
| @end quotation |
| |
| @subsection Running @code{gdbserver} |
| @cindex arguments, to @code{gdbserver} |
| @cindex @code{gdbserver}, command-line arguments |
| |
| Run @code{gdbserver} on the target system. You need a copy of the |
| program you want to debug, including any libraries it requires. |
| @code{gdbserver} does not need your program's symbol table, so you can |
| strip the program if necessary to save space. @value{GDBN} on the host |
| system does all the symbol handling. |
| |
| To use the server, you must tell it how to communicate with @value{GDBN}; |
| the name of your program; and the arguments for your program. The usual |
| syntax is: |
| |
| @smallexample |
| target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ] |
| @end smallexample |
| |
| @var{comm} is either a device name (to use a serial line), or a TCP |
| hostname and portnumber, or @code{-} or @code{stdio} to use |
| stdin/stdout of @code{gdbserver}. |
| For example, to debug Emacs with the argument |
| @samp{foo.txt} and communicate with @value{GDBN} over the serial port |
| @file{/dev/com1}: |
| |
| @smallexample |
| target> gdbserver /dev/com1 emacs foo.txt |
| @end smallexample |
| |
| @code{gdbserver} waits passively for the host @value{GDBN} to communicate |
| with it. |
| |
| To use a TCP connection instead of a serial line: |
| |
| @smallexample |
| target> gdbserver host:2345 emacs foo.txt |
| @end smallexample |
| |
| The only difference from the previous example is the first argument, |
| specifying that you are communicating with the host @value{GDBN} via |
| TCP. The @samp{host:2345} argument means that @code{gdbserver} is to |
| expect a TCP connection from machine @samp{host} to local TCP port 2345. |
| (Currently, the @samp{host} part is ignored.) You can choose any number |
| you want for the port number as long as it does not conflict with any |
| TCP ports already in use on the target system (for example, @code{23} is |
| reserved for @code{telnet}).@footnote{If you choose a port number that |
| conflicts with another service, @code{gdbserver} prints an error message |
| and exits.} You must use the same port number with the host @value{GDBN} |
| @code{target remote} command. |
| |
| The @code{stdio} connection is useful when starting @code{gdbserver} |
| with ssh: |
| |
| @smallexample |
| (gdb) target remote | ssh -T hostname gdbserver - hello |
| @end smallexample |
| |
| The @samp{-T} option to ssh is provided because we don't need a remote pty, |
| and we don't want escape-character handling. Ssh does this by default when |
| a command is provided, the flag is provided to make it explicit. |
| You could elide it if you want to. |
| |
| Programs started with stdio-connected gdbserver have @file{/dev/null} for |
| @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for |
| display through a pipe connected to gdbserver. |
| Both @code{stdout} and @code{stderr} use the same pipe. |
| |
| @subsubsection Attaching to a Running Program |
| @cindex attach to a program, @code{gdbserver} |
| @cindex @option{--attach}, @code{gdbserver} option |
| |
| On some targets, @code{gdbserver} can also attach to running programs. |
| This is accomplished via the @code{--attach} argument. The syntax is: |
| |
| @smallexample |
| target> gdbserver --attach @var{comm} @var{pid} |
| @end smallexample |
| |
| @var{pid} is the process ID of a currently running process. It isn't necessary |
| to point @code{gdbserver} at a binary for the running process. |
| |
| @pindex pidof |
| You can debug processes by name instead of process ID if your target has the |
| @code{pidof} utility: |
| |
| @smallexample |
| target> gdbserver --attach @var{comm} `pidof @var{program}` |
| @end smallexample |
| |
| In case more than one copy of @var{program} is running, or @var{program} |
| has multiple threads, most versions of @code{pidof} support the |
| @code{-s} option to only return the first process ID. |
| |
| @subsubsection Multi-Process Mode for @code{gdbserver} |
| @cindex @code{gdbserver}, multiple processes |
| @cindex multiple processes with @code{gdbserver} |
| |
| When you connect to @code{gdbserver} using @code{target remote}, |
| @code{gdbserver} debugs the specified program only once. When the |
| program exits, or you detach from it, @value{GDBN} closes the connection |
| and @code{gdbserver} exits. |
| |
| If you connect using @kbd{target extended-remote}, @code{gdbserver} |
| enters multi-process mode. When the debugged program exits, or you |
| detach from it, @value{GDBN} stays connected to @code{gdbserver} even |
| though no program is running. The @code{run} and @code{attach} |
| commands instruct @code{gdbserver} to run or attach to a new program. |
| The @code{run} command uses @code{set remote exec-file} (@pxref{set |
| remote exec-file}) to select the program to run. Command line |
| arguments are supported, except for wildcard expansion and I/O |
| redirection (@pxref{Arguments}). |
| |
| @cindex @option{--multi}, @code{gdbserver} option |
| To start @code{gdbserver} without supplying an initial command to run |
| or process ID to attach, use the @option{--multi} command line option. |
| Then you can connect using @kbd{target extended-remote} and start |
| the program you want to debug. |
| |
| In multi-process mode @code{gdbserver} does not automatically exit unless you |
| use the option @option{--once}. You can terminate it by using |
| @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the |
| conditions under which @code{gdbserver} terminates depend on how @value{GDBN} |
| connects to it (@kbd{target remote} or @kbd{target extended-remote}). The |
| @option{--multi} option to @code{gdbserver} has no influence on that. |
| |
| @subsubsection TCP port allocation lifecycle of @code{gdbserver} |
| |
| This section applies only when @code{gdbserver} is run to listen on a TCP port. |
| |
| @code{gdbserver} normally terminates after all of its debugged processes have |
| terminated in @kbd{target remote} mode. On the other hand, for @kbd{target |
| extended-remote}, @code{gdbserver} stays running even with no processes left. |
| @value{GDBN} normally terminates the spawned debugged process on its exit, |
| which normally also terminates @code{gdbserver} in the @kbd{target remote} |
| mode. Therefore, when the connection drops unexpectedly, and @value{GDBN} |
| cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver} |
| stays running even in the @kbd{target remote} mode. |
| |
| When @code{gdbserver} stays running, @value{GDBN} can connect to it again later. |
| Such reconnecting is useful for features like @ref{disconnected tracing}. For |
| completeness, at most one @value{GDBN} can be connected at a time. |
| |
| @cindex @option{--once}, @code{gdbserver} option |
| By default, @code{gdbserver} keeps the listening TCP port open, so that |
| additional connections are possible. However, if you start @code{gdbserver} |
| with the @option{--once} option, it will stop listening for any further |
| connection attempts after connecting to the first @value{GDBN} session. This |
| means no further connections to @code{gdbserver} will be possible after the |
| first one. It also means @code{gdbserver} will terminate after the first |
| connection with remote @value{GDBN} has closed, even for unexpectedly closed |
| connections and even in the @kbd{target extended-remote} mode. The |
| @option{--once} option allows reusing the same port number for connecting to |
| multiple instances of @code{gdbserver} running on the same host, since each |
| instance closes its port after the first connection. |
| |
| @subsubsection Other Command-Line Arguments for @code{gdbserver} |
| |
| @cindex @option{--debug}, @code{gdbserver} option |
| The @option{--debug} option tells @code{gdbserver} to display extra |
| status information about the debugging process. |
| @cindex @option{--remote-debug}, @code{gdbserver} option |
| The @option{--remote-debug} option tells @code{gdbserver} to display |
| remote protocol debug output. These options are intended for |
| @code{gdbserver} development and for bug reports to the developers. |
| |
| @cindex @option{--wrapper}, @code{gdbserver} option |
| The @option{--wrapper} option specifies a wrapper to launch programs |
| for debugging. The option should be followed by the name of the |
| wrapper, then any command-line arguments to pass to the wrapper, then |
| @kbd{--} indicating the end of the wrapper arguments. |
| |
| @code{gdbserver} runs the specified wrapper program with a combined |
| command line including the wrapper arguments, then the name of the |
| program to debug, then any arguments to the program. The wrapper |
| runs until it executes your program, and then @value{GDBN} gains control. |
| |
| You can use any program that eventually calls @code{execve} with |
| its arguments as a wrapper. Several standard Unix utilities do |
| this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending |
| with @code{exec "$@@"} will also work. |
| |
| For example, you can use @code{env} to pass an environment variable to |
| the debugged program, without setting the variable in @code{gdbserver}'s |
| environment: |
| |
| @smallexample |
| $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog |
| @end smallexample |
| |
| @subsection Connecting to @code{gdbserver} |
| |
| Run @value{GDBN} on the host system. |
| |
| First make sure you have the necessary symbol files. Load symbols for |
| your application using the @code{file} command before you connect. Use |
| @code{set sysroot} to locate target libraries (unless your @value{GDBN} |
| was compiled with the correct sysroot using @code{--with-sysroot}). |
| |
| The symbol file and target libraries must exactly match the executable |
| and libraries on the target, with one exception: the files on the host |
| system should not be stripped, even if the files on the target system |
| are. Mismatched or missing files will lead to confusing results |
| during debugging. On @sc{gnu}/Linux targets, mismatched or missing |
| files may also prevent @code{gdbserver} from debugging multi-threaded |
| programs. |
| |
| Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}). |
| For TCP connections, you must start up @code{gdbserver} prior to using |
| the @code{target remote} command. Otherwise you may get an error whose |
| text depends on the host system, but which usually looks something like |
| @samp{Connection refused}. Don't use the @code{load} |
| command in @value{GDBN} when using @code{gdbserver}, since the program is |
| already on the target. |
| |
| @subsection Monitor Commands for @code{gdbserver} |
| @cindex monitor commands, for @code{gdbserver} |
| @anchor{Monitor Commands for gdbserver} |
| |
| During a @value{GDBN} session using @code{gdbserver}, you can use the |
| @code{monitor} command to send special requests to @code{gdbserver}. |
| Here are the available commands. |
| |
| @table @code |
| @item monitor help |
| List the available monitor commands. |
| |
| @item monitor set debug 0 |
| @itemx monitor set debug 1 |
| Disable or enable general debugging messages. |
| |
| @item monitor set remote-debug 0 |
| @itemx monitor set remote-debug 1 |
| Disable or enable specific debugging messages associated with the remote |
| protocol (@pxref{Remote Protocol}). |
| |
| @item monitor set libthread-db-search-path [PATH] |
| @cindex gdbserver, search path for @code{libthread_db} |
| When this command is issued, @var{path} is a colon-separated list of |
| directories to search for @code{libthread_db} (@pxref{Threads,,set |
| libthread-db-search-path}). If you omit @var{path}, |
| @samp{libthread-db-search-path} will be reset to its default value. |
| |
| The special entry @samp{$pdir} for @samp{libthread-db-search-path} is |
| not supported in @code{gdbserver}. |
| |
| @item monitor exit |
| Tell gdbserver to exit immediately. This command should be followed by |
| @code{disconnect} to close the debugging session. @code{gdbserver} will |
| detach from any attached processes and kill any processes it created. |
| Use @code{monitor exit} to terminate @code{gdbserver} at the end |
| of a multi-process mode debug session. |
| |
| @end table |
| |
| @subsection Tracepoints support in @code{gdbserver} |
| @cindex tracepoints support in @code{gdbserver} |
| |
| On some targets, @code{gdbserver} supports tracepoints, fast |
| tracepoints and static tracepoints. |
| |
| For fast or static tracepoints to work, a special library called the |
| @dfn{in-process agent} (IPA), must be loaded in the inferior process. |
| This library is built and distributed as an integral part of |
| @code{gdbserver}. In addition, support for static tracepoints |
| requires building the in-process agent library with static tracepoints |
| support. At present, the UST (LTTng Userspace Tracer, |
| @url{http://lttng.org/ust}) tracing engine is supported. This support |
| is automatically available if UST development headers are found in the |
| standard include path when @code{gdbserver} is built, or if |
| @code{gdbserver} was explicitly configured using @option{--with-ust} |
| to point at such headers. You can explicitly disable the support |
| using @option{--with-ust=no}. |
| |
| There are several ways to load the in-process agent in your program: |
| |
| @table @code |
| @item Specifying it as dependency at link time |
| |
| You can link your program dynamically with the in-process agent |
| library. On most systems, this is accomplished by adding |
| @code{-linproctrace} to the link command. |
| |
| @item Using the system's preloading mechanisms |
| |
| You can force loading the in-process agent at startup time by using |
| your system's support for preloading shared libraries. Many Unixes |
| support the concept of preloading user defined libraries. In most |
| cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so} |
| in the environment. See also the description of @code{gdbserver}'s |
| @option{--wrapper} command line option. |
| |
| @item Using @value{GDBN} to force loading the agent at run time |
| |
| On some systems, you can force the inferior to load a shared library, |
| by calling a dynamic loader function in the inferior that takes care |
| of dynamically looking up and loading a shared library. On most Unix |
| systems, the function is @code{dlopen}. You'll use the @code{call} |
| command for that. For example: |
| |
| @smallexample |
| (@value{GDBP}) call dlopen ("libinproctrace.so", ...) |
| @end smallexample |
| |
| Note that on most Unix systems, for the @code{dlopen} function to be |
| available, the program needs to be linked with @code{-ldl}. |
| @end table |
| |
| On systems that have a userspace dynamic loader, like most Unix |
| systems, when you connect to @code{gdbserver} using @code{target |
| remote}, you'll find that the program is stopped at the dynamic |
| loader's entry point, and no shared library has been loaded in the |
| program's address space yet, including the in-process agent. In that |
| case, before being able to use any of the fast or static tracepoints |
| features, you need to let the loader run and load the shared |
| libraries. The simplest way to do that is to run the program to the |
| main procedure. E.g., if debugging a C or C@t{++} program, start |
| @code{gdbserver} like so: |
| |
| @smallexample |
| $ gdbserver :9999 myprogram |
| @end smallexample |
| |
| Start GDB and connect to @code{gdbserver} like so, and run to main: |
| |
| @smallexample |
| $ gdb myprogram |
| (@value{GDBP}) target remote myhost:9999 |
| 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2 |
| (@value{GDBP}) b main |
| (@value{GDBP}) continue |
| @end smallexample |
| |
| The in-process tracing agent library should now be loaded into the |
| process; you can confirm it with the @code{info sharedlibrary} |
| command, which will list @file{libinproctrace.so} as loaded in the |
| process. You are now ready to install fast tracepoints, list static |
| tracepoint markers, probe static tracepoints markers, and start |
| tracing. |
| |
| @node Remote Configuration |
| @section Remote Configuration |
| |
| @kindex set remote |
| @kindex show remote |
| This section documents the configuration options available when |
| debugging remote programs. For the options related to the File I/O |
| extensions of the remote protocol, see @ref{system, |
| system-call-allowed}. |
| |
| @table @code |
| @item set remoteaddresssize @var{bits} |
| @cindex address size for remote targets |
| @cindex bits in remote address |
| Set the maximum size of address in a memory packet to the specified |
| number of bits. @value{GDBN} will mask off the address bits above |
| that number, when it passes addresses to the remote target. The |
| default value is the number of bits in the target's address. |
| |
| @item show remoteaddresssize |
| Show the current value of remote address size in bits. |
| |
| @item set remotebaud @var{n} |
| @cindex baud rate for remote targets |
| Set the baud rate for the remote serial I/O to @var{n} baud. The |
| value is used to set the speed of the serial port used for debugging |
| remote targets. |
| |
| @item show remotebaud |
| Show the current speed of the remote connection. |
| |
| @item set remotebreak |
| @cindex interrupt remote programs |
| @cindex BREAK signal instead of Ctrl-C |
| @anchor{set remotebreak} |
| If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote |
| when you type @kbd{Ctrl-c} to interrupt the program running |
| on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C} |
| character instead. The default is off, since most remote systems |
| expect to see @samp{Ctrl-C} as the interrupt signal. |
| |
| @item show remotebreak |
| Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to |
| interrupt the remote program. |
| |
| @item set remoteflow on |
| @itemx set remoteflow off |
| @kindex set remoteflow |
| Enable or disable hardware flow control (@code{RTS}/@code{CTS}) |
| on the serial port used to communicate to the remote target. |
| |
| @item show remoteflow |
| @kindex show remoteflow |
| Show the current setting of hardware flow control. |
| |
| @item set remotelogbase @var{base} |
| Set the base (a.k.a.@: radix) of logging serial protocol |
| communications to @var{base}. Supported values of @var{base} are: |
| @code{ascii}, @code{octal}, and @code{hex}. The default is |
| @code{ascii}. |
| |
| @item show remotelogbase |
| Show the current setting of the radix for logging remote serial |
| protocol. |
| |
| @item set remotelogfile @var{file} |
| @cindex record serial communications on file |
| Record remote serial communications on the named @var{file}. The |
| default is not to record at all. |
| |
| @item show remotelogfile. |
| Show the current setting of the file name on which to record the |
| serial communications. |
| |
| @item set remotetimeout @var{num} |
| @cindex timeout for serial communications |
| @cindex remote timeout |
| Set the timeout limit to wait for the remote target to respond to |
| @var{num} seconds. The default is 2 seconds. |
| |
| @item show remotetimeout |
| Show the current number of seconds to wait for the remote target |
| responses. |
| |
| @cindex limit hardware breakpoints and watchpoints |
| @cindex remote target, limit break- and watchpoints |
| @anchor{set remote hardware-watchpoint-limit} |
| @anchor{set remote hardware-breakpoint-limit} |
| @item set remote hardware-watchpoint-limit @var{limit} |
| @itemx set remote hardware-breakpoint-limit @var{limit} |
| Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or |
| watchpoints. A limit of -1, the default, is treated as unlimited. |
| |
| @cindex limit hardware watchpoints length |
| @cindex remote target, limit watchpoints length |
| @anchor{set remote hardware-watchpoint-length-limit} |
| @item set remote hardware-watchpoint-length-limit @var{limit} |
| Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of |
| a remote hardware watchpoint. A limit of -1, the default, is treated |
| as unlimited. |
| |
| @item show remote hardware-watchpoint-length-limit |
| Show the current limit (in bytes) of the maximum length of |
| a remote hardware watchpoint. |
| |
| @item set remote exec-file @var{filename} |
| @itemx show remote exec-file |
| @anchor{set remote exec-file} |
| @cindex executable file, for remote target |
| Select the file used for @code{run} with @code{target |
| extended-remote}. This should be set to a filename valid on the |
| target system. If it is not set, the target will use a default |
| filename (e.g.@: the last program run). |
| |
| @item set remote interrupt-sequence |
| @cindex interrupt remote programs |
| @cindex select Ctrl-C, BREAK or BREAK-g |
| Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or |
| @samp{BREAK-g} as the |
| sequence to the remote target in order to interrupt the execution. |
| @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which |
| is high level of serial line for some certain time. |
| Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g. |
| It is @code{BREAK} signal followed by character @code{g}. |
| |
| @item show interrupt-sequence |
| Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g} |
| is sent by @value{GDBN} to interrupt the remote program. |
| @code{BREAK-g} is BREAK signal followed by @code{g} and |
| also known as Magic SysRq g. |
| |
| @item set remote interrupt-on-connect |
| @cindex send interrupt-sequence on start |
| Specify whether interrupt-sequence is sent to remote target when |
| @value{GDBN} connects to it. This is mostly needed when you debug |
| Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g} |
| which is known as Magic SysRq g in order to connect @value{GDBN}. |
| |
| @item show interrupt-on-connect |
| Show whether interrupt-sequence is sent |
| to remote target when @value{GDBN} connects to it. |
| |
| @kindex set tcp |
| @kindex show tcp |
| @item set tcp auto-retry on |
| @cindex auto-retry, for remote TCP target |
| Enable auto-retry for remote TCP connections. This is useful if the remote |
| debugging agent is launched in parallel with @value{GDBN}; there is a race |
| condition because the agent may not become ready to accept the connection |
| before @value{GDBN} attempts to connect. When auto-retry is |
| enabled, if the initial attempt to connect fails, @value{GDBN} reattempts |
| to establish the connection using the timeout specified by |
| @code{set tcp connect-timeout}. |
| |
| @item set tcp auto-retry off |
| Do not auto-retry failed TCP connections. |
| |
| @item show tcp auto-retry |
| Show the current auto-retry setting. |
| |
| @item set tcp connect-timeout @var{seconds} |
| @cindex connection timeout, for remote TCP target |
| @cindex timeout, for remote target connection |
| Set the timeout for establishing a TCP connection to the remote target to |
| @var{seconds}. The timeout affects both polling to retry failed connections |
| (enabled by @code{set tcp auto-retry on}) and waiting for connections |
| that are merely slow to complete, and represents an approximate cumulative |
| value. |
| |
| @item show tcp connect-timeout |
| Show the current connection timeout setting. |
| @end table |
| |
| @cindex remote packets, enabling and disabling |
| The @value{GDBN} remote protocol autodetects the packets supported by |
| your debugging stub. If you need to override the autodetection, you |
| can use these commands to enable or disable individual packets. Each |
| packet can be set to @samp{on} (the remote target supports this |
| packet), @samp{off} (the remote target does not support this packet), |
| or @samp{auto} (detect remote target support for this packet). They |
| all default to @samp{auto}. For more information about each packet, |
| see @ref{Remote Protocol}. |
| |
| During normal use, you should not have to use any of these commands. |
| If you do, that may be a bug in your remote debugging stub, or a bug |
| in @value{GDBN}. You may want to report the problem to the |
| @value{GDBN} developers. |
| |
| For each packet @var{name}, the command to enable or disable the |
| packet is @code{set remote @var{name}-packet}. The available settings |
| are: |
| |
| @multitable @columnfractions 0.28 0.32 0.25 |
| @item Command Name |
| @tab Remote Packet |
| @tab Related Features |
| |
| @item @code{fetch-register} |
| @tab @code{p} |
| @tab @code{info registers} |
| |
| @item @code{set-register} |
| @tab @code{P} |
| @tab @code{set} |
| |
| @item @code{binary-download} |
| @tab @code{X} |
| @tab @code{load}, @code{set} |
| |
| @item @code{read-aux-vector} |
| @tab @code{qXfer:auxv:read} |
| @tab @code{info auxv} |
| |
| @item @code{symbol-lookup} |
| @tab @code{qSymbol} |
| @tab Detecting multiple threads |
| |
| @item @code{attach} |
| @tab @code{vAttach} |
| @tab @code{attach} |
| |
| @item @code{verbose-resume} |
| @tab @code{vCont} |
| @tab Stepping or resuming multiple threads |
| |
| @item @code{run} |
| @tab @code{vRun} |
| @tab @code{run} |
| |
| @item @code{software-breakpoint} |
| @tab @code{Z0} |
| @tab @code{break} |
| |
| @item @code{hardware-breakpoint} |
| @tab @code{Z1} |
| @tab @code{hbreak} |
| |
| @item @code{write-watchpoint} |
| @tab @code{Z2} |
| @tab @code{watch} |
| |
| @item @code{read-watchpoint} |
| @tab @code{Z3} |
| @tab @code{rwatch} |
| |
| @item @code{access-watchpoint} |
| @tab @code{Z4} |
| @tab @code{awatch} |
| |
| @item @code{target-features} |
| @tab @code{qXfer:features:read} |
| @tab @code{set architecture} |
| |
| @item @code{library-info} |
| @tab @code{qXfer:libraries:read} |
| @tab @code{info sharedlibrary} |
| |
| @item @code{memory-map} |
| @tab @code{qXfer:memory-map:read} |
| @tab @code{info mem} |
| |
| @item @code{read-sdata-object} |
| @tab @code{qXfer:sdata:read} |
| @tab @code{print $_sdata} |
| |
| @item @code{read-spu-object} |
| @tab @code{qXfer:spu:read} |
| @tab @code{info spu} |
| |
| @item @code{write-spu-object} |
| @tab @code{qXfer:spu:write} |
| @tab @code{info spu} |
| |
| @item @code{read-siginfo-object} |
| @tab @code{qXfer:siginfo:read} |
| @tab @code{print $_siginfo} |
| |
| @item @code{write-siginfo-object} |
| @tab @code{qXfer:siginfo:write} |
| @tab @code{set $_siginfo} |
| |
| @item @code{threads} |
| @tab @code{qXfer:threads:read} |
| @tab @code{info threads} |
| |
| @item @code{get-thread-local-@*storage-address} |
| @tab @code{qGetTLSAddr} |
| @tab Displaying @code{__thread} variables |
| |
| @item @code{get-thread-information-block-address} |
| @tab @code{qGetTIBAddr} |
| @tab Display MS-Windows Thread Information Block. |
| |
| @item @code{search-memory} |
| @tab @code{qSearch:memory} |
| @tab @code{find} |
| |
| @item @code{supported-packets} |
| @tab @code{qSupported} |
| @tab Remote communications parameters |
| |
| @item @code{pass-signals} |
| @tab @code{QPassSignals} |
| @tab @code{handle @var{signal}} |
| |
| @item @code{program-signals} |
| @tab @code{QProgramSignals} |
| @tab @code{handle @var{signal}} |
| |
| @item @code{hostio-close-packet} |
| @tab @code{vFile:close} |
| @tab @code{remote get}, @code{remote put} |
| |
| @item @code{hostio-open-packet} |
| @tab @code{vFile:open} |
| @tab @code{remote get}, @code{remote put} |
| |
| @item @code{hostio-pread-packet} |
| @tab @code{vFile:pread} |
| @tab @code{remote get}, @code{remote put} |
| |
| @item @code{hostio-pwrite-packet} |
| @tab @code{vFile:pwrite} |
| @tab @code{remote get}, @code{remote put} |
| |
| @item @code{hostio-unlink-packet} |
| @tab @code{vFile:unlink} |
| @tab @code{remote delete} |
| |
| @item @code{hostio-readlink-packet} |
| @tab @code{vFile:readlink} |
| @tab Host I/O |
| |
| @item @code{noack-packet} |
| @tab @code{QStartNoAckMode} |
| @tab Packet acknowledgment |
| |
| @item @code{osdata} |
| @tab @code{qXfer:osdata:read} |
| @tab @code{info os} |
| |
| @item @code{query-attached} |
| @tab @code{qAttached} |
| @tab Querying remote process attach state. |
| |
| @item @code{traceframe-info} |
| @tab @code{qXfer:traceframe-info:read} |
| @tab Traceframe info |
| |
| @item @code{install-in-trace} |
| @tab @code{InstallInTrace} |
| @tab Install tracepoint in tracing |
| |
| @item @code{disable-randomization} |
| @tab @code{QDisableRandomization} |
| @tab @code{set disable-randomization} |
| |
| @item @code{conditional-breakpoints-packet} |
| @tab @code{Z0 and Z1} |
| @tab @code{Support for target-side breakpoint condition evaluation} |
| @end multitable |
| |
| @node Remote Stub |
| @section Implementing a Remote Stub |
| |
| @cindex debugging stub, example |
| @cindex remote stub, example |
| @cindex stub example, remote debugging |
| The stub files provided with @value{GDBN} implement the target side of the |
| communication protocol, and the @value{GDBN} side is implemented in the |
| @value{GDBN} source file @file{remote.c}. Normally, you can simply allow |
| these subroutines to communicate, and ignore the details. (If you're |
| implementing your own stub file, you can still ignore the details: start |
| with one of the existing stub files. @file{sparc-stub.c} is the best |
| organized, and therefore the easiest to read.) |
| |
| @cindex remote serial debugging, overview |
| To debug a program running on another machine (the debugging |
| @dfn{target} machine), you must first arrange for all the usual |
| prerequisites for the program to run by itself. For example, for a C |
| program, you need: |
| |
| @enumerate |
| @item |
| A startup routine to set up the C runtime environment; these usually |
| have a name like @file{crt0}. The startup routine may be supplied by |
| your hardware supplier, or you may have to write your own. |
| |
| @item |
| A C subroutine library to support your program's |
| subroutine calls, notably managing input and output. |
| |
| @item |
| A way of getting your program to the other machine---for example, a |
| download program. These are often supplied by the hardware |
| manufacturer, but you may have to write your own from hardware |
| documentation. |
| @end enumerate |
| |
| The next step is to arrange for your program to use a serial port to |
| communicate with the machine where @value{GDBN} is running (the @dfn{host} |
| machine). In general terms, the scheme looks like this: |
| |
| @table @emph |
| @item On the host, |
| @value{GDBN} already understands how to use this protocol; when everything |
| else is set up, you can simply use the @samp{target remote} command |
| (@pxref{Targets,,Specifying a Debugging Target}). |
| |
| @item On the target, |
| you must link with your program a few special-purpose subroutines that |
| implement the @value{GDBN} remote serial protocol. The file containing these |
| subroutines is called a @dfn{debugging stub}. |
| |
| On certain remote targets, you can use an auxiliary program |
| @code{gdbserver} instead of linking a stub into your program. |
| @xref{Server,,Using the @code{gdbserver} Program}, for details. |
| @end table |
| |
| The debugging stub is specific to the architecture of the remote |
| machine; for example, use @file{sparc-stub.c} to debug programs on |
| @sc{sparc} boards. |
| |
| @cindex remote serial stub list |
| These working remote stubs are distributed with @value{GDBN}: |
| |
| @table @code |
| |
| @item i386-stub.c |
| @cindex @file{i386-stub.c} |
| @cindex Intel |
| @cindex i386 |
| For Intel 386 and compatible architectures. |
| |
| @item m68k-stub.c |
| @cindex @file{m68k-stub.c} |
| @cindex Motorola 680x0 |
| @cindex m680x0 |
| For Motorola 680x0 architectures. |
| |
| @item sh-stub.c |
| @cindex @file{sh-stub.c} |
| @cindex Renesas |
| @cindex SH |
| For Renesas SH architectures. |
| |
| @item sparc-stub.c |
| @cindex @file{sparc-stub.c} |
| @cindex Sparc |
| For @sc{sparc} architectures. |
| |
| @item sparcl-stub.c |
| @cindex @file{sparcl-stub.c} |
| @cindex Fujitsu |
| @cindex SparcLite |
| For Fujitsu @sc{sparclite} architectures. |
| |
| @end table |
| |
| The @file{README} file in the @value{GDBN} distribution may list other |
| recently added stubs. |
| |
| @menu |
| * Stub Contents:: What the stub can do for you |
| * Bootstrapping:: What you must do for the stub |
| * Debug Session:: Putting it all together |
| @end menu |
| |
| @node Stub Contents |
| @subsection What the Stub Can Do for You |
| |
| @cindex remote serial stub |
| The debugging stub for your architecture supplies these three |
| subroutines: |
| |
| @table @code |
| @item set_debug_traps |
| @findex set_debug_traps |
| @cindex remote serial stub, initialization |
| This routine arranges for @code{handle_exception} to run when your |
| program stops. You must call this subroutine explicitly in your |
| program's startup code. |
| |
| @item handle_exception |
| @findex handle_exception |
| @cindex remote serial stub, main routine |
| This is the central workhorse, but your program never calls it |
| explicitly---the setup code arranges for @code{handle_exception} to |
| run when a trap is triggered. |
| |
| @code{handle_exception} takes control when your program stops during |
| execution (for example, on a breakpoint), and mediates communications |
| with @value{GDBN} on the host machine. This is where the communications |
| protocol is implemented; @code{handle_exception} acts as the @value{GDBN} |
| representative on the target machine. It begins by sending summary |
| information on the state of your program, then continues to execute, |
| retrieving and transmitting any information @value{GDBN} needs, until you |
| execute a @value{GDBN} command that makes your program resume; at that point, |
| @code{handle_exception} returns control to your own code on the target |
| machine. |
| |
| @item breakpoint |
| @cindex @code{breakpoint} subroutine, remote |
| Use this auxiliary subroutine to make your program contain a |
| breakpoint. Depending on the particular situation, this may be the only |
| way for @value{GDBN} to get control. For instance, if your target |
| machine has some sort of interrupt button, you won't need to call this; |
| pressing the interrupt button transfers control to |
| @code{handle_exception}---in effect, to @value{GDBN}. On some machines, |
| simply receiving characters on the serial port may also trigger a trap; |
| again, in that situation, you don't need to call @code{breakpoint} from |
| your own program---simply running @samp{target remote} from the host |
| @value{GDBN} session gets control. |
| |
| Call @code{breakpoint} if none of these is true, or if you simply want |
| to make certain your program stops at a predetermined point for the |
| start of your debugging session. |
| @end table |
| |
| @node Bootstrapping |
| @subsection What You Must Do for the Stub |
| |
| @cindex remote stub, support routines |
| The debugging stubs that come with @value{GDBN} are set up for a particular |
| chip architecture, but they have no information about the rest of your |
| debugging target machine. |
| |
| First of all you need to tell the stub how to communicate with the |
| serial port. |
| |
| @table @code |
| @item int getDebugChar() |
| @findex getDebugChar |
| Write this subroutine to read a single character from the serial port. |
| It may be identical to @code{getchar} for your target system; a |
| different name is used to allow you to distinguish the two if you wish. |
| |
| @item void putDebugChar(int) |
| @findex putDebugChar |
| Write this subroutine to write a single character to the serial port. |
| It may be identical to @code{putchar} for your target system; a |
| different name is used to allow you to distinguish the two if you wish. |
| @end table |
| |
| @cindex control C, and remote debugging |
| @cindex interrupting remote targets |
| If you want @value{GDBN} to be able to stop your program while it is |
| running, you need to use an interrupt-driven serial driver, and arrange |
| for it to stop when it receives a @code{^C} (@samp{\003}, the control-C |
| character). That is the character which @value{GDBN} uses to tell the |
| remote system to stop. |
| |
| Getting the debugging target to return the proper status to @value{GDBN} |
| probably requires changes to the standard stub; one quick and dirty way |
| is to just execute a breakpoint instruction (the ``dirty'' part is that |
| @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}). |
| |
| Other routines you need to supply are: |
| |
| @table @code |
| @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address}) |
| @findex exceptionHandler |
| Write this function to install @var{exception_address} in the exception |
| handling tables. You need to do this because the stub does not have any |
| way of knowing what the exception handling tables on your target system |
| are like (for example, the processor's table might be in @sc{rom}, |
| containing entries which point to a table in @sc{ram}). |
| @var{exception_number} is the exception number which should be changed; |
| its meaning is architecture-dependent (for example, different numbers |
| might represent divide by zero, misaligned access, etc). When this |
| exception occurs, control should be transferred directly to |
| @var{exception_address}, and the processor state (stack, registers, |
| and so on) should be just as it is when a processor exception occurs. So if |
| you want to use a jump instruction to reach @var{exception_address}, it |
| should be a simple jump, not a jump to subroutine. |
| |
| For the 386, @var{exception_address} should be installed as an interrupt |
| gate so that interrupts are masked while the handler runs. The gate |
| should be at privilege level 0 (the most privileged level). The |
| @sc{sparc} and 68k stubs are able to mask interrupts themselves without |
| help from @code{exceptionHandler}. |
| |
| @item void flush_i_cache() |
| @findex flush_i_cache |
| On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the |
| instruction cache, if any, on your target machine. If there is no |
| instruction cache, this subroutine may be a no-op. |
| |
| On target machines that have instruction caches, @value{GDBN} requires this |
| function to make certain that the state of your program is stable. |
| @end table |
| |
| @noindent |
| You must also make sure this library routine is available: |
| |
| @table @code |
| @item void *memset(void *, int, int) |
| @findex memset |
| This is the standard library function @code{memset} that sets an area of |
| memory to a known value. If you have one of the free versions of |
| @code{libc.a}, @code{memset} can be found there; otherwise, you must |
| either obtain it from your hardware manufacturer, or write your own. |
| @end table |
| |
| If you do not use the GNU C compiler, you may need other standard |
| library subroutines as well; this varies from one stub to another, |
| but in general the stubs are likely to use any of the common library |
| subroutines which @code{@value{NGCC}} generates as inline code. |
| |
| |
| @node Debug Session |
| @subsection Putting it All Together |
| |
| @cindex remote serial debugging summary |
| In summary, when your program is ready to debug, you must follow these |
| steps. |
| |
| @enumerate |
| @item |
| Make sure you have defined the supporting low-level routines |
| (@pxref{Bootstrapping,,What You Must Do for the Stub}): |
| @display |
| @code{getDebugChar}, @code{putDebugChar}, |
| @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}. |
| @end display |
| |
| @item |
| Insert these lines in your program's startup code, before the main |
| procedure is called: |
| |
| @smallexample |
| set_debug_traps(); |
| breakpoint(); |
| @end smallexample |
| |
| On some machines, when a breakpoint trap is raised, the hardware |
| automatically makes the PC point to the instruction after the |
| breakpoint. If your machine doesn't do that, you may need to adjust |
| @code{handle_exception} to arrange for it to return to the instruction |
| after the breakpoint on this first invocation, so that your program |
| doesn't keep hitting the initial breakpoint instead of making |
| progress. |
| |
| @item |
| For the 680x0 stub only, you need to provide a variable called |
| @code{exceptionHook}. Normally you just use: |
| |
| @smallexample |
| void (*exceptionHook)() = 0; |
| @end smallexample |
| |
| @noindent |
| but if before calling @code{set_debug_traps}, you set it to point to a |
| function in your program, that function is called when |
| @code{@value{GDBN}} continues after stopping on a trap (for example, bus |
| error). The function indicated by @code{exceptionHook} is called with |
| one parameter: an @code{int} which is the exception number. |
| |
| @item |
| Compile and link together: your program, the @value{GDBN} debugging stub for |
| your target architecture, and the supporting subroutines. |
| |
| @item |
| Make sure you have a serial connection between your target machine and |
| the @value{GDBN} host, and identify the serial port on the host. |
| |
| @item |
| @c The "remote" target now provides a `load' command, so we should |
| @c document that. FIXME. |
| Download your program to your target machine (or get it there by |
| whatever means the manufacturer provides), and start it. |
| |
| @item |
| Start @value{GDBN} on the host, and connect to the target |
| (@pxref{Connecting,,Connecting to a Remote Target}). |
| |
| @end enumerate |
| |
| @node Configurations |
| @chapter Configuration-Specific Information |
| |
| While nearly all @value{GDBN} commands are available for all native and |
| cross versions of the debugger, there are some exceptions. This chapter |
| describes things that are only available in certain configurations. |
| |
| There are three major categories of configurations: native |
| configurations, where the host and target are the same, embedded |
| operating system configurations, which are usually the same for several |
| different processor architectures, and bare embedded processors, which |
| are quite different from each other. |
| |
| @menu |
| * Native:: |
| * Embedded OS:: |
| * Embedded Processors:: |
| * Architectures:: |
| @end menu |
| |
| @node Native |
| @section Native |
| |
| This section describes details specific to particular native |
| configurations. |
| |
| @menu |
| * HP-UX:: HP-UX |
| * BSD libkvm Interface:: Debugging BSD kernel memory images |
| * SVR4 Process Information:: SVR4 process information |
| * DJGPP Native:: Features specific to the DJGPP port |
| * Cygwin Native:: Features specific to the Cygwin port |
| * Hurd Native:: Features specific to @sc{gnu} Hurd |
| * Neutrino:: Features specific to QNX Neutrino |
| * Darwin:: Features specific to Darwin |
| @end menu |
| |
| @node HP-UX |
| @subsection HP-UX |
| |
| On HP-UX systems, if you refer to a function or variable name that |
| begins with a dollar sign, @value{GDBN} searches for a user or system |
| name first, before it searches for a convenience variable. |
| |
| |
| @node BSD libkvm Interface |
| @subsection BSD libkvm Interface |
| |
| @cindex libkvm |
| @cindex kernel memory image |
| @cindex kernel crash dump |
| |
| BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory |
| interface that provides a uniform interface for accessing kernel virtual |
| memory images, including live systems and crash dumps. @value{GDBN} |
| uses this interface to allow you to debug live kernels and kernel crash |
| dumps on many native BSD configurations. This is implemented as a |
| special @code{kvm} debugging target. For debugging a live system, load |
| the currently running kernel into @value{GDBN} and connect to the |
| @code{kvm} target: |
| |
| @smallexample |
| (@value{GDBP}) @b{target kvm} |
| @end smallexample |
| |
| For debugging crash dumps, provide the file name of the crash dump as an |
| argument: |
| |
| @smallexample |
| (@value{GDBP}) @b{target kvm /var/crash/bsd.0} |
| @end smallexample |
| |
| Once connected to the @code{kvm} target, the following commands are |
| available: |
| |
| @table @code |
| @kindex kvm |
| @item kvm pcb |
| Set current context from the @dfn{Process Control Block} (PCB) address. |
| |
| @item kvm proc |
| Set current context from proc address. This command isn't available on |
| modern FreeBSD systems. |
| @end table |
| |
| @node SVR4 Process Information |
| @subsection SVR4 Process Information |
| @cindex /proc |
| @cindex examine process image |
| @cindex process info via @file{/proc} |
| |
| Many versions of SVR4 and compatible systems provide a facility called |
| @samp{/proc} that can be used to examine the image of a running |
| process using file-system subroutines. If @value{GDBN} is configured |
| for an operating system with this facility, the command @code{info |
| proc} is available to report information about the process running |
| your program, or about any process running on your system. @code{info |
| proc} works only on SVR4 systems that include the @code{procfs} code. |
| This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital |
| Unix), Solaris, Irix, and Unixware, but not HP-UX, for example. |
| |
| @table @code |
| @kindex info proc |
| @cindex process ID |
| @item info proc |
| @itemx info proc @var{process-id} |
| Summarize available information about any running process. If a |
| process ID is specified by @var{process-id}, display information about |
| that process; otherwise display information about the program being |
| debugged. The summary includes the debugged process ID, the command |
| line used to invoke it, its current working directory, and its |
| executable file's absolute file name. |
| |
| On some systems, @var{process-id} can be of the form |
| @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID |
| within a process. If the optional @var{pid} part is missing, it means |
| a thread from the process being debugged (the leading @samp{/} still |
| needs to be present, or else @value{GDBN} will interpret the number as |
| a process ID rather than a thread ID). |
| |
| @item info proc mappings |
| @cindex memory address space mappings |
| Report the memory address space ranges accessible in the program, with |
| information on whether the process has read, write, or execute access |
| rights to each range. On @sc{gnu}/Linux systems, each memory range |
| includes the object file which is mapped to that range, instead of the |
| memory access rights to that range. |
| |
| @item info proc stat |
| @itemx info proc status |
| @cindex process detailed status information |
| These subcommands are specific to @sc{gnu}/Linux systems. They show |
| the process-related information, including the user ID and group ID; |
| how many threads are there in the process; its virtual memory usage; |
| the signals that are pending, blocked, and ignored; its TTY; its |
| consumption of system and user time; its stack size; its @samp{nice} |
| value; etc. For more information, see the @samp{proc} man page |
| (type @kbd{man 5 proc} from your shell prompt). |
| |
| @item info proc all |
| Show all the information about the process described under all of the |
| above @code{info proc} subcommands. |
| |
| @ignore |
| @comment These sub-options of 'info proc' were not included when |
| @comment procfs.c was re-written. Keep their descriptions around |
| @comment against the day when someone finds the time to put them back in. |
| @kindex info proc times |
| @item info proc times |
| Starting time, user CPU time, and system CPU time for your program and |
| its children. |
| |
| @kindex info proc id |
| @item info proc id |
| Report on the process IDs related to your program: its own process ID, |
| the ID of its parent, the process group ID, and the session ID. |
| @end ignore |
| |
| @item set procfs-trace |
| @kindex set procfs-trace |
| @cindex @code{procfs} API calls |
| This command enables and disables tracing of @code{procfs} API calls. |
| |
| @item show procfs-trace |
| @kindex show procfs-trace |
| Show the current state of @code{procfs} API call tracing. |
| |
| @item set procfs-file @var{file} |
| @kindex set procfs-file |
| Tell @value{GDBN} to write @code{procfs} API trace to the named |
| @var{file}. @value{GDBN} appends the trace info to the previous |
| contents of the file. The default is to display the trace on the |
| standard output. |
| |
| @item show procfs-file |
| @kindex show procfs-file |
| Show the file to which @code{procfs} API trace is written. |
| |
| @item proc-trace-entry |
| @itemx proc-trace-exit |
| @itemx proc-untrace-entry |
| @itemx proc-untrace-exit |
| @kindex proc-trace-entry |
| @kindex proc-trace-exit |
| @kindex proc-untrace-entry |
| @kindex proc-untrace-exit |
| These commands enable and disable tracing of entries into and exits |
| from the @code{syscall} interface. |
| |
| @item info pidlist |
| @kindex info pidlist |
| @cindex process list, QNX Neutrino |
| For QNX Neutrino only, this command displays the list of all the |
| processes and all the threads within each process. |
| |
| @item info meminfo |
| @kindex info meminfo |
| @cindex mapinfo list, QNX Neutrino |
| For QNX Neutrino only, this command displays the list of all mapinfos. |
| @end table |
| |
| @node DJGPP Native |
| @subsection Features for Debugging @sc{djgpp} Programs |
| @cindex @sc{djgpp} debugging |
| @cindex native @sc{djgpp} debugging |
| @cindex MS-DOS-specific commands |
| |
| @cindex DPMI |
| @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and |
| MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs |
| that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on |
| top of real-mode DOS systems and their emulations. |
| |
| @value{GDBN} supports native debugging of @sc{djgpp} programs, and |
| defines a few commands specific to the @sc{djgpp} port. This |
| subsection describes those commands. |
| |
| @table @code |
| @kindex info dos |
| @item info dos |
| This is a prefix of @sc{djgpp}-specific commands which print |
| information about the target system and important OS structures. |
| |
| @kindex sysinfo |
| @cindex MS-DOS system info |
| @cindex free memory information (MS-DOS) |
| @item info dos sysinfo |
| This command displays assorted information about the underlying |
| platform: the CPU type and features, the OS version and flavor, the |
| DPMI version, and the available conventional and DPMI memory. |
| |
| @cindex GDT |
| @cindex LDT |
| @cindex IDT |
| @cindex segment descriptor tables |
| @cindex descriptor tables display |
| @item info dos gdt |
| @itemx info dos ldt |
| @itemx info dos idt |
| These 3 commands display entries from, respectively, Global, Local, |
| and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor |
| tables are data structures which store a descriptor for each segment |
| that is currently in use. The segment's selector is an index into a |
| descriptor table; the table entry for that index holds the |
| descriptor's base address and limit, and its attributes and access |
| rights. |
| |
| A typical @sc{djgpp} program uses 3 segments: a code segment, a data |
| segment (used for both data and the stack), and a DOS segment (which |
| allows access to DOS/BIOS data structures and absolute addresses in |
| conventional memory). However, the DPMI host will usually define |
| additional segments in order to support the DPMI environment. |
| |
| @cindex garbled pointers |
| These commands allow to display entries from the descriptor tables. |
| Without an argument, all entries from the specified table are |
| displayed. An argument, which should be an integer expression, means |
| display a single entry whose index is given by the argument. For |
| example, here's a convenient way to display information about the |
| debugged program's data segment: |
| |
| @smallexample |
| @exdent @code{(@value{GDBP}) info dos ldt $ds} |
| @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)} |
| @end smallexample |
| |
| @noindent |
| This comes in handy when you want to see whether a pointer is outside |
| the data segment's limit (i.e.@: @dfn{garbled}). |
| |
| @cindex page tables display (MS-DOS) |
| @item info dos pde |
| @itemx info dos pte |
| These two commands display entries from, respectively, the Page |
| Directory and the Page Tables. Page Directories and Page Tables are |
| data structures which control how virtual memory addresses are mapped |
| into physical addresses. A Page Table includes an entry for every |
| page of memory that is mapped into the program's address space; there |
| may be several Page Tables, each one holding up to 4096 entries. A |
| Page Directory has up to 4096 entries, one each for every Page Table |
| that is currently in use. |
| |
| Without an argument, @kbd{info dos pde} displays the entire Page |
| Directory, and @kbd{info dos pte} displays all the entries in all of |
| the Page Tables. An argument, an integer expression, given to the |
| @kbd{info dos pde} command means display only that entry from the Page |
| Directory table. An argument given to the @kbd{info dos pte} command |
| means display entries from a single Page Table, the one pointed to by |
| the specified entry in the Page Directory. |
| |
| @cindex direct memory access (DMA) on MS-DOS |
| These commands are useful when your program uses @dfn{DMA} (Direct |
| Memory Access), which needs physical addresses to program the DMA |
| controller. |
| |
| These commands are supported only with some DPMI servers. |
| |
| @cindex physical address from linear address |
| @item info dos address-pte @var{addr} |
| This command displays the Page Table entry for a specified linear |
| address. The argument @var{addr} is a linear address which should |
| already have the appropriate segment's base address added to it, |
| because this command accepts addresses which may belong to @emph{any} |
| segment. For example, here's how to display the Page Table entry for |
| the page where a variable @code{i} is stored: |
| |
| @smallexample |
| @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i} |
| @exdent @code{Page Table entry for address 0x11a00d30:} |
| @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30} |
| @end smallexample |
| |
| @noindent |
| This says that @code{i} is stored at offset @code{0xd30} from the page |
| whose physical base address is @code{0x02698000}, and shows all the |
| attributes of that page. |
| |
| Note that you must cast the addresses of variables to a @code{char *}, |
| since otherwise the value of @code{__djgpp_base_address}, the base |
| address of all variables and functions in a @sc{djgpp} program, will |
| be added using the rules of C pointer arithmetics: if @code{i} is |
| declared an @code{int}, @value{GDBN} will add 4 times the value of |
| @code{__djgpp_base_address} to the address of @code{i}. |
| |
| Here's another example, it displays the Page Table entry for the |
| transfer buffer: |
| |
| @smallexample |
| @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)} |
| @exdent @code{Page Table entry for address 0x29110:} |
| @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110} |
| @end smallexample |
| |
| @noindent |
| (The @code{+ 3} offset is because the transfer buffer's address is the |
| 3rd member of the @code{_go32_info_block} structure.) The output |
| clearly shows that this DPMI server maps the addresses in conventional |
| memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and |
| linear (@code{0x29110}) addresses are identical. |
| |
| This command is supported only with some DPMI servers. |
| @end table |
| |
| @cindex DOS serial data link, remote debugging |
| In addition to native debugging, the DJGPP port supports remote |
| debugging via a serial data link. The following commands are specific |
| to remote serial debugging in the DJGPP port of @value{GDBN}. |
| |
| @table @code |
| @kindex set com1base |
| @kindex set com1irq |
| @kindex set com2base |
| @kindex set com2irq |
| @kindex set com3base |
| @kindex set com3irq |
| @kindex set com4base |
| @kindex set com4irq |
| @item set com1base @var{addr} |
| This command sets the base I/O port address of the @file{COM1} serial |
| port. |
| |
| @item set com1irq @var{irq} |
| This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use |
| for the @file{COM1} serial port. |
| |
| There are similar commands @samp{set com2base}, @samp{set com3irq}, |
| etc.@: for setting the port address and the @code{IRQ} lines for the |
| other 3 COM ports. |
| |
| @kindex show com1base |
| @kindex show com1irq |
| @kindex show com2base |
| @kindex show com2irq |
| @kindex show com3base |
| @kindex show com3irq |
| @kindex show com4base |
| @kindex show com4irq |
| The related commands @samp{show com1base}, @samp{show com1irq} etc.@: |
| display the current settings of the base address and the @code{IRQ} |
| lines used by the COM ports. |
| |
| @item info serial |
| @kindex info serial |
| @cindex DOS serial port status |
| This command prints the status of the 4 DOS serial ports. For each |
| port, it prints whether it's active or not, its I/O base address and |
| IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the |
| counts of various errors encountered so far. |
| @end table |
| |
| |
| @node Cygwin Native |
| @subsection Features for Debugging MS Windows PE Executables |
| @cindex MS Windows debugging |
| @cindex native Cygwin debugging |
| @cindex Cygwin-specific commands |
| |
| @value{GDBN} supports native debugging of MS Windows programs, including |
| DLLs with and without symbolic debugging information. |
| |
| @cindex Ctrl-BREAK, MS-Windows |
| @cindex interrupt debuggee on MS-Windows |
| MS-Windows programs that call @code{SetConsoleMode} to switch off the |
| special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted |
| by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows |
| supports @kbd{C-@key{BREAK}} as an alternative interrupt key |
| sequence, which can be used to interrupt the debuggee even if it |
| ignores @kbd{C-c}. |
| |
| There are various additional Cygwin-specific commands, described in |
| this section. Working with DLLs that have no debugging symbols is |
| described in @ref{Non-debug DLL Symbols}. |
| |
| @table @code |
| @kindex info w32 |
| @item info w32 |
| This is a prefix of MS Windows-specific commands which print |
| information about the target system and important OS structures. |
| |
| @item info w32 selector |
| This command displays information returned by |
| the Win32 API @code{GetThreadSelectorEntry} function. |
| It takes an optional argument that is evaluated to |
| a long value to give the information about this given selector. |
| Without argument, this command displays information |
| about the six segment registers. |
| |
| @item info w32 thread-information-block |
| This command displays thread specific information stored in the |
| Thread Information Block (readable on the X86 CPU family using @code{$fs} |
| selector for 32-bit programs and @code{$gs} for 64-bit programs). |
| |
| @kindex info dll |
| @item info dll |
| This is a Cygwin-specific alias of @code{info shared}. |
| |
| @kindex dll-symbols |
| @item dll-symbols |
| This command loads symbols from a dll similarly to |
| add-sym command but without the need to specify a base address. |
| |
| @kindex set cygwin-exceptions |
| @cindex debugging the Cygwin DLL |
| @cindex Cygwin DLL, debugging |
| @item set cygwin-exceptions @var{mode} |
| If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that |
| happen inside the Cygwin DLL. If @var{mode} is @code{off}, |
| @value{GDBN} will delay recognition of exceptions, and may ignore some |
| exceptions which seem to be caused by internal Cygwin DLL |
| ``bookkeeping''. This option is meant primarily for debugging the |
| Cygwin DLL itself; the default value is @code{off} to avoid annoying |
| @value{GDBN} users with false @code{SIGSEGV} signals. |
| |
| @kindex show cygwin-exceptions |
| @item show cygwin-exceptions |
| Displays whether @value{GDBN} will break on exceptions that happen |
| inside the Cygwin DLL itself. |
| |
| @kindex set new-console |
| @item set new-console @var{mode} |
| If @var{mode} is @code{on} the debuggee will |
| be started in a new console on next start. |
| If @var{mode} is @code{off}, the debuggee will |
| be started in the same console as the debugger. |
| |
| @kindex show new-console |
| @item show new-console |
| Displays whether a new console is used |
| when the debuggee is started. |
| |
| @kindex set new-group |
| @item set new-group @var{mode} |
| This boolean value controls whether the debuggee should |
| start a new group or stay in the same group as the debugger. |
| This affects the way the Windows OS handles |
| @samp{Ctrl-C}. |
| |
| @kindex show new-group |
| @item show new-group |
| Displays current value of new-group boolean. |
| |
| @kindex set debugevents |
| @item set debugevents |
| This boolean value adds debug output concerning kernel events related |
| to the debuggee seen by the debugger. This includes events that |
| signal thread and process creation and exit, DLL loading and |
| unloading, console interrupts, and debugging messages produced by the |
| Windows @code{OutputDebugString} API call. |
| |
| @kindex set debugexec |
| @item set debugexec |
| This boolean value adds debug output concerning execute events |
| (such as resume thread) seen by the debugger. |
| |
| @kindex set debugexceptions |
| @item set debugexceptions |
| This boolean value adds debug output concerning exceptions in the |
| debuggee seen by the debugger. |
| |
| @kindex set debugmemory |
| @item set debugmemory |
| This boolean value adds debug output concerning debuggee memory reads |
| and writes by the debugger. |
| |
| @kindex set shell |
| @item set shell |
| This boolean values specifies whether the debuggee is called |
| via a shell or directly (default value is on). |
| |
| @kindex show shell |
| @item show shell |
| Displays if the debuggee will be started with a shell. |
| |
| @end table |
| |
| @menu |
| * Non-debug DLL Symbols:: Support for DLLs without debugging symbols |
| @end menu |
| |
| @node Non-debug DLL Symbols |
| @subsubsection Support for DLLs without Debugging Symbols |
| @cindex DLLs with no debugging symbols |
| @cindex Minimal symbols and DLLs |
| |
| Very often on windows, some of the DLLs that your program relies on do |
| not include symbolic debugging information (for example, |
| @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging |
| symbols in a DLL, it relies on the minimal amount of symbolic |
| information contained in the DLL's export table. This section |
| describes working with such symbols, known internally to @value{GDBN} as |
| ``minimal symbols''. |
| |
| Note that before the debugged program has started execution, no DLLs |
| will have been loaded. The easiest way around this problem is simply to |
| start the program --- either by setting a breakpoint or letting the |
| program run once to completion. It is also possible to force |
| @value{GDBN} to load a particular DLL before starting the executable --- |
| see the shared library information in @ref{Files}, or the |
| @code{dll-symbols} command in @ref{Cygwin Native}. Currently, |
| explicitly loading symbols from a DLL with no debugging information will |
| cause the symbol names to be duplicated in @value{GDBN}'s lookup table, |
| which may adversely affect symbol lookup performance. |
| |
| @subsubsection DLL Name Prefixes |
| |
| In keeping with the naming conventions used by the Microsoft debugging |
| tools, DLL export symbols are made available with a prefix based on the |
| DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is |
| also entered into the symbol table, so @code{CreateFileA} is often |
| sufficient. In some cases there will be name clashes within a program |
| (particularly if the executable itself includes full debugging symbols) |
| necessitating the use of the fully qualified name when referring to the |
| contents of the DLL. Use single-quotes around the name to avoid the |
| exclamation mark (``!'') being interpreted as a language operator. |
| |
| Note that the internal name of the DLL may be all upper-case, even |
| though the file name of the DLL is lower-case, or vice-versa. Since |
| symbols within @value{GDBN} are @emph{case-sensitive} this may cause |
| some confusion. If in doubt, try the @code{info functions} and |
| @code{info variables} commands or even @code{maint print msymbols} |
| (@pxref{Symbols}). Here's an example: |
| |
| @smallexample |
| (@value{GDBP}) info function CreateFileA |
| All functions matching regular expression "CreateFileA": |
| |
| Non-debugging symbols: |
| 0x77e885f4 CreateFileA |
| 0x77e885f4 KERNEL32!CreateFileA |
| @end smallexample |
| |
| @smallexample |
| (@value{GDBP}) info function ! |
| All functions matching regular expression "!": |
| |
| Non-debugging symbols: |
| 0x6100114c cygwin1!__assert |
| 0x61004034 cygwin1!_dll_crt0@@0 |
| 0x61004240 cygwin1!dll_crt0(per_process *) |
| [etc...] |
| @end smallexample |
| |
| @subsubsection Working with Minimal Symbols |
| |
| Symbols extracted from a DLL's export table do not contain very much |
| type information. All that @value{GDBN} can do is guess whether a symbol |
| refers to a function or variable depending on the linker section that |
| contains the symbol. Also note that the actual contents of the memory |
| contained in a DLL are not available unless the program is running. This |
| means that you cannot examine the contents of a variable or disassemble |
| a function within a DLL without a running program. |
| |
| Variables are generally treated as pointers and dereferenced |
| automatically. For this reason, it is often necessary to prefix a |
| variable name with the address-of operator (``&'') and provide explicit |
| type information in the command. Here's an example of the type of |
| problem: |
| |
| @smallexample |
| (@value{GDBP}) print 'cygwin1!__argv' |
| $1 = 268572168 |
| @end smallexample |
| |
| @smallexample |
| (@value{GDBP}) x 'cygwin1!__argv' |
| 0x10021610: "\230y\"" |
| @end smallexample |
| |
| And two possible solutions: |
| |
| @smallexample |
| (@value{GDBP}) print ((char **)'cygwin1!__argv')[0] |
| $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram" |
| @end smallexample |
| |
| @smallexample |
| (@value{GDBP}) x/2x &'cygwin1!__argv' |
| 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000 |
| (@value{GDBP}) x/x 0x10021608 |
| 0x10021608: 0x0022fd98 |
| (@value{GDBP}) x/s 0x0022fd98 |
| 0x22fd98: "/cygdrive/c/mydirectory/myprogram" |
| @end smallexample |
| |
| Setting a break point within a DLL is possible even before the program |
| starts execution. However, under these circumstances, @value{GDBN} can't |
| examine the initial instructions of the function in order to skip the |
| function's frame set-up code. You can work around this by using ``*&'' |
| to set the breakpoint at a raw memory address: |
| |
| @smallexample |
| (@value{GDBP}) break *&'python22!PyOS_Readline' |
| Breakpoint 1 at 0x1e04eff0 |
| @end smallexample |
| |
| The author of these extensions is not entirely convinced that setting a |
| break point within a shared DLL like @file{kernel32.dll} is completely |
| safe. |
| |
| @node Hurd Native |
| @subsection Commands Specific to @sc{gnu} Hurd Systems |
| @cindex @sc{gnu} Hurd debugging |
| |
| This subsection describes @value{GDBN} commands specific to the |
| @sc{gnu} Hurd native debugging. |
| |
| @table @code |
| @item set signals |
| @itemx set sigs |
| @kindex set signals@r{, Hurd command} |
| @kindex set sigs@r{, Hurd command} |
| This command toggles the state of inferior signal interception by |
| @value{GDBN}. Mach exceptions, such as breakpoint traps, are not |
| affected by this command. @code{sigs} is a shorthand alias for |
| @code{signals}. |
| |
| @item show signals |
| @itemx show sigs |
| @kindex show signals@r{, Hurd command} |
| @kindex show sigs@r{, Hurd command} |
| Show the current state of intercepting inferior's signals. |
| |
| @item set signal-thread |
| @itemx set sigthread |
| @kindex set signal-thread |
| @kindex set sigthread |
| This command tells @value{GDBN} which thread is the @code{libc} signal |
| thread. That thread is run when a signal is delivered to a running |
| process. @code{set sigthread} is the shorthand alias of @code{set |
| signal-thread}. |
| |
| @item show signal-thread |
| @itemx show sigthread |
| @kindex show signal-thread |
| @kindex show sigthread |
| These two commands show which thread will run when the inferior is |
| delivered a signal. |
| |
| @item set stopped |
| @kindex set stopped@r{, Hurd command} |
| This commands tells @value{GDBN} that the inferior process is stopped, |
| as with the @code{SIGSTOP} signal. The stopped process can be |
| continued by delivering a signal to it. |
| |
| @item show stopped |
| @kindex show stopped@r{, Hurd command} |
| This command shows whether @value{GDBN} thinks the debuggee is |
| stopped. |
| |
| @item set exceptions |
| @kindex set exceptions@r{, Hurd command} |
| Use this command to turn off trapping of exceptions in the inferior. |
| When exception trapping is off, neither breakpoints nor |
| single-stepping will work. To restore the default, set exception |
| trapping on. |
| |
| @item show exceptions |
| @kindex show exceptions@r{, Hurd command} |
| Show the current state of trapping exceptions in the inferior. |
| |
| @item set task pause |
| @kindex set task@r{, Hurd commands} |
| @cindex task attributes (@sc{gnu} Hurd) |
| @cindex pause current task (@sc{gnu} Hurd) |
| This command toggles task suspension when @value{GDBN} has control. |
| Setting it to on takes effect immediately, and the task is suspended |
| whenever @value{GDBN} gets control. Setting it to off will take |
| effect the next time the inferior is continued. If this option is set |
| to off, you can use @code{set thread default pause on} or @code{set |
| thread pause on} (see below) to pause individual threads. |
| |
| @item show task pause |
| @kindex show task@r{, Hurd commands} |
| Show the current state of task suspension. |
| |
| @item set task detach-suspend-count |
| @cindex task suspend count |
| @cindex detach from task, @sc{gnu} Hurd |
| This command sets the suspend count the task will be left with when |
| @value{GDBN} detaches from it. |
| |
| @item show task detach-suspend-count |
| Show the suspend count the task will be left with when detaching. |
| |
| @item set task exception-port |
| @itemx set task excp |
| @cindex task exception port, @sc{gnu} Hurd |
| This command sets the task exception port to which @value{GDBN} will |
| forward exceptions. The argument should be the value of the @dfn{send |
| rights} of the task. @code{set task excp} is a shorthand alias. |
| |
| @item set noninvasive |
| @cindex noninvasive task options |
| This command switches @value{GDBN} to a mode that is the least |
| invasive as far as interfering with the inferior is concerned. This |
| is the same as using @code{set task pause}, @code{set exceptions}, and |
| @code{set signals} to values opposite to the defaults. |
| |
| @item info send-rights |
| @itemx info receive-rights |
| @itemx info port-rights |
| @itemx info port-sets |
| @itemx info dead-names |
| @itemx info ports |
| @itemx info psets |
| @cindex send rights, @sc{gnu} Hurd |
| @cindex receive rights, @sc{gnu} Hurd |
| @cindex port rights, @sc{gnu} Hurd |
| @cindex port sets, @sc{gnu} Hurd |
| @cindex dead names, @sc{gnu} Hurd |
| These commands display information about, respectively, send rights, |
| receive rights, port rights, port sets, and dead names of a task. |
| There are also shorthand aliases: @code{info ports} for @code{info |
| port-rights} and @code{info psets} for @code{info port-sets}. |
| |
| @item set thread pause |
| @kindex set thread@r{, Hurd command} |
| @cindex thread properties, @sc{gnu} Hurd |
| @cindex pause current thread (@sc{gnu} Hurd) |
| This command toggles current thread suspension when @value{GDBN} has |
| control. Setting it to on takes effect immediately, and the current |
| thread is suspended whenever @value{GDBN} gets control. Setting it to |
| off will take effect the next time the inferior is continued. |
| Normally, this command has no effect, since when @value{GDBN} has |
| control, the whole task is suspended. However, if you used @code{set |
| task pause off} (see above), this command comes in handy to suspend |
| only the current thread. |
| |
| @item show thread pause |
| @kindex show thread@r{, Hurd command} |
| This command shows the state of current thread suspension. |
| |
| @item set thread run |
| This command sets whether the current thread is allowed to run. |
| |
| @item show thread run |
| Show whether the current thread is allowed to run. |
| |
| @item set thread detach-suspend-count |
| @cindex thread suspend count, @sc{gnu} Hurd |
| @cindex detach from thread, @sc{gnu} Hurd |
| This command sets the suspend count @value{GDBN} will leave on a |
| thread when detaching. This number is relative to the suspend count |
| found by @value{GDBN} when it notices the thread; use @code{set thread |
| takeover-suspend-count} to force it to an absolute value. |
| |
| @item show thread detach-suspend-count |
| Show the suspend count @value{GDBN} will leave on the thread when |
| detaching. |
| |
| @item set thread exception-port |
| @itemx set thread excp |
| Set the thread exception port to which to forward exceptions. This |
| overrides the port set by @code{set task exception-port} (see above). |
| @code{set thread excp} is the shorthand alias. |
| |
| @item set thread takeover-suspend-count |
| Normally, @value{GDBN}'s thread suspend counts are relative to the |
| value @value{GDBN} finds when it notices each thread. This command |
| changes the suspend counts to be absolute instead. |
| |
| @item set thread default |
| @itemx show thread default |
| @cindex thread default settings, @sc{gnu} Hurd |
| Each of the above @code{set thread} commands has a @code{set thread |
| default} counterpart (e.g., @code{set thread default pause}, @code{set |
| thread default exception-port}, etc.). The @code{thread default} |
| variety of commands sets the default thread properties for all |
| threads; you can then change the properties of individual threads with |
| the non-default commands. |
| @end table |
| |
| |
| @node Neutrino |
| @subsection QNX Neutrino |
| @cindex QNX Neutrino |
| |
| @value{GDBN} provides the following commands specific to the QNX |
| Neutrino target: |
| |
| @table @code |
| @item set debug nto-debug |
| @kindex set debug nto-debug |
| When set to on, enables debugging messages specific to the QNX |
| Neutrino support. |
| |
| @item show debug nto-debug |
| @kindex show debug nto-debug |
| Show the current state of QNX Neutrino messages. |
| @end table |
| |
| @node Darwin |
| @subsection Darwin |
| @cindex Darwin |
| |
| @value{GDBN} provides the following commands specific to the Darwin target: |
| |
| @table @code |
| @item set debug darwin @var{num} |
| @kindex set debug darwin |
| When set to a non zero value, enables debugging messages specific to |
| the Darwin support. Higher values produce more verbose output. |
| |
| @item show debug darwin |
| @kindex show debug darwin |
| Show the current state of Darwin messages. |
| |
| @item set debug mach-o @var{num} |
| @kindex set debug mach-o |
| When set to a non zero value, enables debugging messages while |
| @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the |
| file format used on Darwin for object and executable files.) Higher |
| values produce more verbose output. This is a command to diagnose |
| problems internal to @value{GDBN} and should not be needed in normal |
| usage. |
| |
| @item show debug mach-o |
| @kindex show debug mach-o |
| Show the current state of Mach-O file messages. |
| |
| @item set mach-exceptions on |
| @itemx set mach-exceptions off |
| @kindex set mach-exceptions |
| On Darwin, faults are first reported as a Mach exception and are then |
| mapped to a Posix signal. Use this command to turn on trapping of |
| Mach exceptions in the inferior. This might be sometimes useful to |
| better understand the cause of a fault. The default is off. |
| |
| @item show mach-exceptions |
| @kindex show mach-exceptions |
| Show the current state of exceptions trapping. |
| @end table |
| |
| |
| @node Embedded OS |
| @section Embedded Operating Systems |
| |
| This section describes configurations involving the debugging of |
| embedded operating systems that are available for several different |
| architectures. |
| |
| @menu |
| * VxWorks:: Using @value{GDBN} with VxWorks |
| @end menu |
| |
| @value{GDBN} includes the ability to debug programs running on |
| various real-time operating systems. |
| |
| @node VxWorks |
| @subsection Using @value{GDBN} with VxWorks |
| |
| @cindex VxWorks |
| |
| @table @code |
| |
| @kindex target vxworks |
| @item target vxworks @var{machinename} |
| A VxWorks system, attached via TCP/IP. The argument @var{machinename} |
| is the target system's machine name or IP address. |
| |
| @end table |
| |
| On VxWorks, @code{load} links @var{filename} dynamically on the |
| current target system as well as adding its symbols in @value{GDBN}. |
| |
| @value{GDBN} enables developers to spawn and debug tasks running on networked |
| VxWorks targets from a Unix host. Already-running tasks spawned from |
| the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on |
| both the Unix host and on the VxWorks target. The program |
| @code{@value{GDBP}} is installed and executed on the Unix host. (It may be |
| installed with the name @code{vxgdb}, to distinguish it from a |
| @value{GDBN} for debugging programs on the host itself.) |
| |
| @table @code |
| @item VxWorks-timeout @var{args} |
| @kindex vxworks-timeout |
| All VxWorks-based targets now support the option @code{vxworks-timeout}. |
| This option is set by the user, and @var{args} represents the number of |
| seconds @value{GDBN} waits for responses to rpc's. You might use this if |
| your VxWorks target is a slow software simulator or is on the far side |
| of a thin network line. |
| @end table |
| |
| The following information on connecting to VxWorks was current when |
| this manual was produced; newer releases of VxWorks may use revised |
| procedures. |
| |
| @findex INCLUDE_RDB |
| To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel |
| to include the remote debugging interface routines in the VxWorks |
| library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the |
| VxWorks configuration file @file{configAll.h} and rebuild your VxWorks |
| kernel. The resulting kernel contains @file{rdb.a}, and spawns the |
| source debugging task @code{tRdbTask} when VxWorks is booted. For more |
| information on configuring and remaking VxWorks, see the manufacturer's |
| manual. |
| @c VxWorks, see the @cite{VxWorks Programmer's Guide}. |
| |
| Once you have included @file{rdb.a} in your VxWorks system image and set |
| your Unix execution search path to find @value{GDBN}, you are ready to |
| run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or |
| @code{vxgdb}, depending on your installation). |
| |
| @value{GDBN} comes up showing the prompt: |
| |
| @smallexample |
| (vxgdb) |
| @end smallexample |
| |
| @menu |
| * VxWorks Connection:: Connecting to VxWorks |
| * VxWorks Download:: VxWorks download |
| * VxWorks Attach:: Running tasks |
| @end menu |
| |
| @node VxWorks Connection |
| @subsubsection Connecting to VxWorks |
| |
| The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the |
| network. To connect to a target whose host name is ``@code{tt}'', type: |
| |
| @smallexample |
| (vxgdb) target vxworks tt |
| @end smallexample |
| |
| @need 750 |
| @value{GDBN} displays messages like these: |
| |
| @smallexample |
| Attaching remote machine across net... |
| Connected to tt. |
| @end smallexample |
| |
| @need 1000 |
| @value{GDBN} then attempts to read the symbol tables of any object modules |
| loaded into the VxWorks target since it was last booted. @value{GDBN} locates |
| these files by searching the directories listed in the command search |
| path (@pxref{Environment, ,Your Program's Environment}); if it fails |
| to find an object file, it displays a message such as: |
| |
| @smallexample |
| prog.o: No such file or directory. |
| @end smallexample |
| |
| When this happens, add the appropriate directory to the search path with |
| the @value{GDBN} command @code{path}, and execute the @code{target} |
| command again. |
| |
| @node VxWorks Download |
| @subsubsection VxWorks Download |
| |
| @cindex download to VxWorks |
| If you have connected to the VxWorks target and you want to debug an |
| object that has not yet been loaded, you can use the @value{GDBN} |
| @code{load} command to download a file from Unix to VxWorks |
| incrementally. The object file given as an argument to the @code{load} |
| command is actually opened twice: first by the VxWorks target in order |
| to download the code, then by @value{GDBN} in order to read the symbol |
| table. This can lead to problems if the current working directories on |
| the two systems differ. If both systems have NFS mounted the same |
| filesystems, you can avoid these problems by using absolute paths. |
| Otherwise, it is simplest to set the working directory on both systems |
| to the directory in which the object file resides, and then to reference |
| the file by its name, without any path. For instance, a program |
| @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks |
| and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this |
| program, type this on VxWorks: |
| |
| @smallexample |
| -> cd "@var{vxpath}/vw/demo/rdb" |
| @end smallexample |
| |
| @noindent |
| Then, in @value{GDBN}, type: |
| |
| @smallexample |
| (vxgdb) cd @var{hostpath}/vw/demo/rdb |
| (vxgdb) load prog.o |
| @end smallexample |
| |
| @value{GDBN} displays a response similar to this: |
| |
| @smallexample |
| Reading symbol data from wherever/vw/demo/rdb/prog.o... done. |
| @end smallexample |
| |
| You can also use the @code{load} command to reload an object module |
| after editing and recompiling the corresponding source file. Note that |
| this makes @value{GDBN} delete all currently-defined breakpoints, |
| auto-displays, and convenience variables, and to clear the value |
| history. (This is necessary in order to preserve the integrity of |
| debugger's data structures that reference the target system's symbol |
| table.) |
| |
| @node VxWorks Attach |
| @subsubsection Running Tasks |
| |
| @cindex running VxWorks tasks |
| You can also attach to an existing task using the @code{attach} command as |
| follows: |
| |
| @smallexample |
| (vxgdb) attach @var{task} |
| @end smallexample |
| |
| @noindent |
| where @var{task} is the VxWorks hexadecimal task ID. The task can be running |
| or suspended when you attach to it. Running tasks are suspended at |
| the time of attachment. |
| |
| @node Embedded Processors |
| @section Embedded Processors |
| |
| This section goes into details specific to particular embedded |
| configurations. |
| |
| @cindex send command to simulator |
| Whenever a specific embedded processor has a simulator, @value{GDBN} |
| allows to send an arbitrary command to the simulator. |
| |
| @table @code |
| @item sim @var{command} |
| @kindex sim@r{, a command} |
| Send an arbitrary @var{command} string to the simulator. Consult the |
| documentation for the specific simulator in use for information about |
| acceptable commands. |
| @end table |
| |
| |
| @menu |
| * ARM:: ARM RDI |
| * M32R/D:: Renesas M32R/D |
| * M68K:: Motorola M68K |
| * MicroBlaze:: Xilinx MicroBlaze |
| * MIPS Embedded:: MIPS Embedded |
| * OpenRISC 1000:: OpenRisc 1000 |
| * PowerPC Embedded:: PowerPC Embedded |
| * PA:: HP PA Embedded |
| * Sparclet:: Tsqware Sparclet |
| * Sparclite:: Fujitsu Sparclite |
| * Z8000:: Zilog Z8000 |
| * AVR:: Atmel AVR |
| * CRIS:: CRIS |
| * Super-H:: Renesas Super-H |
| @end menu |
| |
| @node ARM |
| @subsection ARM |
| @cindex ARM RDI |
| |
| @table @code |
| @kindex target rdi |
| @item target rdi @var{dev} |
| ARM Angel monitor, via RDI library interface to ADP protocol. You may |
| use this target to communicate with both boards running the Angel |
| monitor, or with the EmbeddedICE JTAG debug device. |
| |
| @kindex target rdp |
| @item target rdp @var{dev} |
| ARM Demon monitor. |
| |
| @end table |
| |
| @value{GDBN} provides the following ARM-specific commands: |
| |
| @table @code |
| @item set arm disassembler |
| @kindex set arm |
| This commands selects from a list of disassembly styles. The |
| @code{"std"} style is the standard style. |
| |
| @item show arm disassembler |
| @kindex show arm |
| Show the current disassembly style. |
| |
| @item set arm apcs32 |
| @cindex ARM 32-bit mode |
| This command toggles ARM operation mode between 32-bit and 26-bit. |
| |
| @item show arm apcs32 |
| Display the current usage of the ARM 32-bit mode. |
| |
| @item set arm fpu @var{fputype} |
| This command sets the ARM floating-point unit (FPU) type. The |
| argument @var{fputype} can be one of these: |
| |
| @table @code |
| @item auto |
| Determine the FPU type by querying the OS ABI. |
| @item softfpa |
| Software FPU, with mixed-endian doubles on little-endian ARM |
| processors. |
| @item fpa |
| GCC-compiled FPA co-processor. |
| @item softvfp |
| Software FPU with pure-endian doubles. |
| @item vfp |
| VFP co-processor. |
| @end table |
| |
| @item show arm fpu |
| Show the current type of the FPU. |
| |
| @item set arm abi |
| This command forces @value{GDBN} to use the specified ABI. |
| |
| @item show arm abi |
| Show the currently used ABI. |
| |
| @item set arm fallback-mode (arm|thumb|auto) |
| @value{GDBN} uses the symbol table, when available, to determine |
| whether instructions are ARM or Thumb. This command controls |
| @value{GDBN}'s default behavior when the symbol table is not |
| available. The default is @samp{auto}, which causes @value{GDBN} to |
| use the current execution mode (from the @code{T} bit in the @code{CPSR} |
| register). |
| |
| @item show arm fallback-mode |
| Show the current fallback instruction mode. |
| |
| @item set arm force-mode (arm|thumb|auto) |
| This command overrides use of the symbol table to determine whether |
| instructions are ARM or Thumb. The default is @samp{auto}, which |
| causes @value{GDBN} to use the symbol table and then the setting |
| of @samp{set arm fallback-mode}. |
| |
| @item show arm force-mode |
| Show the current forced instruction mode. |
| |
| @item set debug arm |
| Toggle whether to display ARM-specific debugging messages from the ARM |
| target support subsystem. |
| |
| @item show debug arm |
| Show whether ARM-specific debugging messages are enabled. |
| @end table |
| |
| The following commands are available when an ARM target is debugged |
| using the RDI interface: |
| |
| @table @code |
| @item rdilogfile @r{[}@var{file}@r{]} |
| @kindex rdilogfile |
| @cindex ADP (Angel Debugger Protocol) logging |
| Set the filename for the ADP (Angel Debugger Protocol) packet log. |
| With an argument, sets the log file to the specified @var{file}. With |
| no argument, show the current log file name. The default log file is |
| @file{rdi.log}. |
| |
| @item rdilogenable @r{[}@var{arg}@r{]} |
| @kindex rdilogenable |
| Control logging of ADP packets. With an argument of 1 or @code{"yes"} |
| enables logging, with an argument 0 or @code{"no"} disables it. With |
| no arguments displays the current setting. When logging is enabled, |
| ADP packets exchanged between @value{GDBN} and the RDI target device |
| are logged to a file. |
| |
| @item set rdiromatzero |
| @kindex set rdiromatzero |
| @cindex ROM at zero address, RDI |
| Tell @value{GDBN} whether the target has ROM at address 0. If on, |
| vector catching is disabled, so that zero address can be used. If off |
| (the default), vector catching is enabled. For this command to take |
| effect, it needs to be invoked prior to the @code{target rdi} command. |
| |
| @item show rdiromatzero |
| @kindex show rdiromatzero |
| Show the current setting of ROM at zero address. |
| |
| @item set rdiheartbeat |
| @kindex set rdiheartbeat |
| @cindex RDI heartbeat |
| Enable or disable RDI heartbeat packets. It is not recommended to |
| turn on this option, since it confuses ARM and EPI JTAG interface, as |
| well as the Angel monitor. |
| |
| @item show rdiheartbeat |
| @kindex show rdiheartbeat |
| Show the setting of RDI heartbeat packets. |
| @end table |
| |
| @table @code |
| @item target sim @r{[}@var{simargs}@r{]} @dots{} |
| The @value{GDBN} ARM simulator accepts the following optional arguments. |
| |
| @table @code |
| @item --swi-support=@var{type} |
| Tell the simulator which SWI interfaces to support. |
| @var{type} may be a comma separated list of the following values. |
| The default value is @code{all}. |
| |
| @table @code |
| @item none |
| @item demon |
| @item angel |
| @item redboot |
| @item all |
| @end table |
| @end table |
| @end table |
| |
| @node M32R/D |
| @subsection Renesas M32R/D and M32R/SDI |
| |
| @table @code |
| @kindex target m32r |
| @item target m32r @var{dev} |
| Renesas M32R/D ROM monitor. |
| |
| @kindex target m32rsdi |
| @item target m32rsdi @var{dev} |
| Renesas M32R SDI server, connected via parallel port to the board. |
| @end table |
| |
| The following @value{GDBN} commands are specific to the M32R monitor: |
| |
| @table @code |
| @item set download-path @var{path} |
| @kindex set download-path |
| @cindex find downloadable @sc{srec} files (M32R) |
| Set the default path for finding downloadable @sc{srec} files. |
| |
| @item show download-path |
| @kindex show download-path |
| Show the default path for downloadable @sc{srec} files. |
| |
| @item set board-address @var{addr} |
| @kindex set board-address |
| @cindex M32-EVA target board address |
| Set the IP address for the M32R-EVA target board. |
| |
| @item show board-address |
| @kindex show board-address |
| Show the current IP address of the target board. |
| |
| @item set server-address @var{addr} |
| @kindex set server-address |
| @cindex download server address (M32R) |
| Set the IP address for the download server, which is the @value{GDBN}'s |
| host machine. |
| |
| @item show server-address |
| @kindex show server-address |
| Display the IP address of the download server. |
| |
| @item upload @r{[}@var{file}@r{]} |
| @kindex upload@r{, M32R} |
| Upload the specified @sc{srec} @var{file} via the monitor's Ethernet |
| upload capability. If no @var{file} argument is given, the current |
| executable file is uploaded. |
| |
| @item tload @r{[}@var{file}@r{]} |
| @kindex tload@r{, M32R} |
| Test the @code{upload} command. |
| @end table |
| |
| The following commands are available for M32R/SDI: |
| |
| @table @code |
| @item sdireset |
| @kindex sdireset |
| @cindex reset SDI connection, M32R |
| This command resets the SDI connection. |
| |
| @item sdistatus |
| @kindex sdistatus |
| This command shows the SDI connection status. |
| |
| @item debug_chaos |
| @kindex debug_chaos |
| @cindex M32R/Chaos debugging |
| Instructs the remote that M32R/Chaos debugging is to be used. |
| |
| @item use_debug_dma |
| @kindex use_debug_dma |
| Instructs the remote to use the DEBUG_DMA method of accessing memory. |
| |
| @item use_mon_code |
| @kindex use_mon_code |
| Instructs the remote to use the MON_CODE method of accessing memory. |
| |
| @item use_ib_break |
| @kindex use_ib_break |
| Instructs the remote to set breakpoints by IB break. |
| |
| @item use_dbt_break |
| @kindex use_dbt_break |
| Instructs the remote to set breakpoints by DBT. |
| @end table |
| |
| @node M68K |
| @subsection M68k |
| |
| The Motorola m68k configuration includes ColdFire support, and a |
| target command for the following ROM monitor. |
| |
| @table @code |
| |
| @kindex target dbug |
| @item target dbug @var{dev} |
| dBUG ROM monitor for Motorola ColdFire. |
| |
| @end table |
| |
| @node MicroBlaze |
| @subsection MicroBlaze |
| @cindex Xilinx MicroBlaze |
| @cindex XMD, Xilinx Microprocessor Debugger |
| |
| The MicroBlaze is a soft-core processor supported on various Xilinx |
| FPGAs, such as Spartan or Virtex series. Boards with these processors |
| usually have JTAG ports which connect to a host system running the Xilinx |
| Embedded Development Kit (EDK) or Software Development Kit (SDK). |
| This host system is used to download the configuration bitstream to |
| the target FPGA. The Xilinx Microprocessor Debugger (XMD) program |
| communicates with the target board using the JTAG interface and |
| presents a @code{gdbserver} interface to the board. By default |
| @code{xmd} uses port @code{1234}. (While it is possible to change |
| this default port, it requires the use of undocumented @code{xmd} |
| commands. Contact Xilinx support if you need to do this.) |
| |
| Use these GDB commands to connect to the MicroBlaze target processor. |
| |
| @table @code |
| @item target remote :1234 |
| Use this command to connect to the target if you are running @value{GDBN} |
| on the same system as @code{xmd}. |
| |
| @item target remote @var{xmd-host}:1234 |
| Use this command to connect to the target if it is connected to @code{xmd} |
| running on a different system named @var{xmd-host}. |
| |
| @item load |
| Use this command to download a program to the MicroBlaze target. |
| |
| @item set debug microblaze @var{n} |
| Enable MicroBlaze-specific debugging messages if non-zero. |
| |
| @item show debug microblaze @var{n} |
| Show MicroBlaze-specific debugging level. |
| @end table |
| |
| @node MIPS Embedded |
| @subsection @acronym{MIPS} Embedded |
| |
| @cindex @acronym{MIPS} boards |
| @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a |
| @acronym{MIPS} board attached to a serial line. This is available when |
| you configure @value{GDBN} with @samp{--target=mips-elf}. |
| |
| @need 1000 |
| Use these @value{GDBN} commands to specify the connection to your target board: |
| |
| @table @code |
| @item target mips @var{port} |
| @kindex target mips @var{port} |
| To run a program on the board, start up @code{@value{GDBP}} with the |
| name of your program as the argument. To connect to the board, use the |
| command @samp{target mips @var{port}}, where @var{port} is the name of |
| the serial port connected to the board. If the program has not already |
| been downloaded to the board, you may use the @code{load} command to |
| download it. You can then use all the usual @value{GDBN} commands. |
| |
| For example, this sequence connects to the target board through a serial |
| port, and loads and runs a program called @var{prog} through the |
| debugger: |
| |
| @smallexample |
| host$ @value{GDBP} @var{prog} |
| @value{GDBN} is free software and @dots{} |
| (@value{GDBP}) target mips /dev/ttyb |
| (@value{GDBP}) load @var{prog} |
| (@value{GDBP}) run |
| @end smallexample |
| |
| @item target mips @var{hostname}:@var{portnumber} |
| On some @value{GDBN} host configurations, you can specify a TCP |
| connection (for instance, to a serial line managed by a terminal |
| concentrator) instead of a serial port, using the syntax |
| @samp{@var{hostname}:@var{portnumber}}. |
| |
| @item target pmon @var{port} |
| @kindex target pmon @var{port} |
| PMON ROM monitor. |
| |
| @item target ddb @var{port} |
| @kindex target ddb @var{port} |
| NEC's DDB variant of PMON for Vr4300. |
| |
| @item target lsi @var{port} |
| @kindex target lsi @var{port} |
| LSI variant of PMON. |
| |
| @kindex target r3900 |
| @item target r3900 @var{dev} |
| Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips. |
| |
| @kindex target array |
| @item target array @var{dev} |
| Array Tech LSI33K RAID controller board. |
| |
| @end table |
| |
| |
| @noindent |
| @value{GDBN} also supports these special commands for @acronym{MIPS} targets: |
| |
| @table @code |
| @item set mipsfpu double |
| @itemx set mipsfpu single |
| @itemx set mipsfpu none |
| @itemx set mipsfpu auto |
| @itemx show mipsfpu |
| @kindex set mipsfpu |
| @kindex show mipsfpu |
| @cindex @acronym{MIPS} remote floating point |
| @cindex floating point, @acronym{MIPS} remote |
| If your target board does not support the @acronym{MIPS} floating point |
| coprocessor, you should use the command @samp{set mipsfpu none} (if you |
| need this, you may wish to put the command in your @value{GDBN} init |
| file). This tells @value{GDBN} how to find the return value of |
| functions which return floating point values. It also allows |
| @value{GDBN} to avoid saving the floating point registers when calling |
| functions on the board. If you are using a floating point coprocessor |
| with only single precision floating point support, as on the @sc{r4650} |
| processor, use the command @samp{set mipsfpu single}. The default |
| double precision floating point coprocessor may be selected using |
| @samp{set mipsfpu double}. |
| |
| In previous versions the only choices were double precision or no |
| floating point, so @samp{set mipsfpu on} will select double precision |
| and @samp{set mipsfpu off} will select no floating point. |
| |
| As usual, you can inquire about the @code{mipsfpu} variable with |
| @samp{show mipsfpu}. |
| |
| @item set timeout @var{seconds} |
| @itemx set retransmit-timeout @var{seconds} |
| @itemx show timeout |
| @itemx show retransmit-timeout |
| @cindex @code{timeout}, @acronym{MIPS} protocol |
| @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol |
| @kindex set timeout |
| @kindex show timeout |
| @kindex set retransmit-timeout |
| @kindex show retransmit-timeout |
| You can control the timeout used while waiting for a packet, in the @acronym{MIPS} |
| remote protocol, with the @code{set timeout @var{seconds}} command. The |
| default is 5 seconds. Similarly, you can control the timeout used while |
| waiting for an acknowledgment of a packet with the @code{set |
| retransmit-timeout @var{seconds}} command. The default is 3 seconds. |
| You can inspect both values with @code{show timeout} and @code{show |
| retransmit-timeout}. (These commands are @emph{only} available when |
| @value{GDBN} is configured for @samp{--target=mips-elf}.) |
| |
| The timeout set by @code{set timeout} does not apply when @value{GDBN} |
| is waiting for your program to stop. In that case, @value{GDBN} waits |
| forever because it has no way of knowing how long the program is going |
| to run before stopping. |
| |
| @item set syn-garbage-limit @var{num} |
| @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote} |
| @cindex synchronize with remote @acronym{MIPS} target |
| Limit the maximum number of characters @value{GDBN} should ignore when |
| it tries to synchronize with the remote target. The default is 10 |
| characters. Setting the limit to -1 means there's no limit. |
| |
| @item show syn-garbage-limit |
| @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote} |
| Show the current limit on the number of characters to ignore when |
| trying to synchronize with the remote system. |
| |
| @item set monitor-prompt @var{prompt} |
| @kindex set monitor-prompt@r{, @acronym{MIPS} remote} |
| @cindex remote monitor prompt |
| Tell @value{GDBN} to expect the specified @var{prompt} string from the |
| remote monitor. The default depends on the target: |
| @table @asis |
| @item pmon target |
| @samp{PMON} |
| @item ddb target |
| @samp{NEC010} |
| @item lsi target |
| @samp{PMON>} |
| @end table |
| |
| @item show monitor-prompt |
| @kindex show monitor-prompt@r{, @acronym{MIPS} remote} |
| Show the current strings @value{GDBN} expects as the prompt from the |
| remote monitor. |
| |
| @item set monitor-warnings |
| @kindex set monitor-warnings@r{, @acronym{MIPS} remote} |
| Enable or disable monitor warnings about hardware breakpoints. This |
| has effect only for the @code{lsi} target. When on, @value{GDBN} will |
| display warning messages whose codes are returned by the @code{lsi} |
| PMON monitor for breakpoint commands. |
| |
| @item show monitor-warnings |
| @kindex show monitor-warnings@r{, @acronym{MIPS} remote} |
| Show the current setting of printing monitor warnings. |
| |
| @item pmon @var{command} |
| @kindex pmon@r{, @acronym{MIPS} remote} |
| @cindex send PMON command |
| This command allows sending an arbitrary @var{command} string to the |
| monitor. The monitor must be in debug mode for this to work. |
| @end table |
| |
| @node OpenRISC 1000 |
| @subsection OpenRISC 1000 |
| @cindex OpenRISC 1000 |
| |
| @cindex or1k boards |
| See OR1k Architecture document (@uref{www.opencores.org}) for more information |
| about platform and commands. |
| |
| @table @code |
| |
| @kindex target jtag |
| @item target jtag jtag://@var{host}:@var{port} |
| |
| Connects to remote JTAG server. |
| JTAG remote server can be either an or1ksim or JTAG server, |
| connected via parallel port to the board. |
| |
| Example: @code{target jtag jtag://localhost:9999} |
| |
| @kindex or1ksim |
| @item or1ksim @var{command} |
| If connected to @code{or1ksim} OpenRISC 1000 Architectural |
| Simulator, proprietary commands can be executed. |
| |
| @kindex info or1k spr |
| @item info or1k spr |
| Displays spr groups. |
| |
| @item info or1k spr @var{group} |
| @itemx info or1k spr @var{groupno} |
| Displays register names in selected group. |
| |
| @item info or1k spr @var{group} @var{register} |
| @itemx info or1k spr @var{register} |
| @itemx info or1k spr @var{groupno} @var{registerno} |
| @itemx info or1k spr @var{registerno} |
| Shows information about specified spr register. |
| |
| @kindex spr |
| @item spr @var{group} @var{register} @var{value} |
| @itemx spr @var{register @var{value}} |
| @itemx spr @var{groupno} @var{registerno @var{value}} |
| @itemx spr @var{registerno @var{value}} |
| Writes @var{value} to specified spr register. |
| @end table |
| |
| Some implementations of OpenRISC 1000 Architecture also have hardware trace. |
| It is very similar to @value{GDBN} trace, except it does not interfere with normal |
| program execution and is thus much faster. Hardware breakpoints/watchpoint |
| triggers can be set using: |
| @table @code |
| @item $LEA/$LDATA |
| Load effective address/data |
| @item $SEA/$SDATA |
| Store effective address/data |
| @item $AEA/$ADATA |
| Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA) |
| @item $FETCH |
| Fetch data |
| @end table |
| |
| When triggered, it can capture low level data, like: @code{PC}, @code{LSEA}, |
| @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}. |
| |
| @code{htrace} commands: |
| @cindex OpenRISC 1000 htrace |
| @table @code |
| @kindex hwatch |
| @item hwatch @var{conditional} |
| Set hardware watchpoint on combination of Load/Store Effective Address(es) |
| or Data. For example: |
| |
| @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)} |
| |
| @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)} |
| |
| @kindex htrace |
| @item htrace info |
| Display information about current HW trace configuration. |
| |
| @item htrace trigger @var{conditional} |
| Set starting criteria for HW trace. |
| |
| @item htrace qualifier @var{conditional} |
| Set acquisition qualifier for HW trace. |
| |
| @item htrace stop @var{conditional} |
| Set HW trace stopping criteria. |
| |
| @item htrace record [@var{data}]* |
| Selects the data to be recorded, when qualifier is met and HW trace was |
| triggered. |
| |
| @item htrace enable |
| @itemx htrace disable |
| Enables/disables the HW trace. |
| |
| @item htrace rewind [@var{filename}] |
| Clears currently recorded trace data. |
| |
| If filename is specified, new trace file is made and any newly collected data |
| will be written there. |
| |
| @item htrace print [@var{start} [@var{len}]] |
| Prints trace buffer, using current record configuration. |
| |
| @item htrace mode continuous |
| Set continuous trace mode. |
| |
| @item htrace mode suspend |
| Set suspend trace mode. |
| |
| @end table |
| |
| @node PowerPC Embedded |
| @subsection PowerPC Embedded |
| |
| @cindex DVC register |
| @value{GDBN} supports using the DVC (Data Value Compare) register to |
| implement in hardware simple hardware watchpoint conditions of the form: |
| |
| @smallexample |
| (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \ |
| if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION} |
| @end smallexample |
| |
| The DVC register will be automatically used when @value{GDBN} detects |
| such pattern in a condition expression, and the created watchpoint uses one |
| debug register (either the @code{exact-watchpoints} option is on and the |
| variable is scalar, or the variable has a length of one byte). This feature |
| is available in native @value{GDBN} running on a Linux kernel version 2.6.34 |
| or newer. |
| |
| When running on PowerPC embedded processors, @value{GDBN} automatically uses |
| ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on, |
| in which case watchpoints using only one debug register are created when |
| watching variables of scalar types. |
| |
| You can create an artificial array to watch an arbitrary memory |
| region using one of the following commands (@pxref{Expressions}): |
| |
| @smallexample |
| (@value{GDBP}) watch *((char *) @var{address})@@@var{length} |
| (@value{GDBP}) watch @{char[@var{length}]@} @var{address} |
| @end smallexample |
| |
| PowerPC embedded processors support masked watchpoints. See the discussion |
| about the @code{mask} argument in @ref{Set Watchpoints}. |
| |
| @cindex ranged breakpoint |
| PowerPC embedded processors support hardware accelerated |
| @dfn{ranged breakpoints}. A ranged breakpoint stops execution of |
| the inferior whenever it executes an instruction at any address within |
| the range it specifies. To set a ranged breakpoint in @value{GDBN}, |
| use the @code{break-range} command. |
| |
| @value{GDBN} provides the following PowerPC-specific commands: |
| |
| @table @code |
| @kindex break-range |
| @item break-range @var{start-location}, @var{end-location} |
| Set a breakpoint for an address range. |
| @var{start-location} and @var{end-location} can specify a function name, |
| a line number, an offset of lines from the current line or from the start |
| location, or an address of an instruction (see @ref{Specify Location}, |
| for a list of all the possible ways to specify a @var{location}.) |
| The breakpoint will stop execution of the inferior whenever it |
| executes an instruction at any address within the specified range, |
| (including @var{start-location} and @var{end-location}.) |
| |
| @kindex set powerpc |
| @item set powerpc soft-float |
| @itemx show powerpc soft-float |
| Force @value{GDBN} to use (or not use) a software floating point calling |
| convention. By default, @value{GDBN} selects the calling convention based |
| on the selected architecture and the provided executable file. |
| |
| @item set powerpc vector-abi |
| @itemx show powerpc vector-abi |
| Force @value{GDBN} to use the specified calling convention for vector |
| arguments and return values. The valid options are @samp{auto}; |
| @samp{generic}, to avoid vector registers even if they are present; |
| @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE |
| registers. By default, @value{GDBN} selects the calling convention |
| based on the selected architecture and the provided executable file. |
| |
| @item set powerpc exact-watchpoints |
| @itemx show powerpc exact-watchpoints |
| Allow @value{GDBN} to use only one debug register when watching a variable |
| of scalar type, thus assuming that the variable is accessed through the |
| address of its first byte. |
| |
| @kindex target dink32 |
| @item target dink32 @var{dev} |
| DINK32 ROM monitor. |
| |
| @kindex target ppcbug |
| @item target ppcbug @var{dev} |
| @kindex target ppcbug1 |
| @item target ppcbug1 @var{dev} |
| PPCBUG ROM monitor for PowerPC. |
| |
| @kindex target sds |
| @item target sds @var{dev} |
| SDS monitor, running on a PowerPC board (such as Motorola's ADS). |
| @end table |
| |
| @cindex SDS protocol |
| The following commands specific to the SDS protocol are supported |
| by @value{GDBN}: |
| |
| @table @code |
| @item set sdstimeout @var{nsec} |
| @kindex set sdstimeout |
| Set the timeout for SDS protocol reads to be @var{nsec} seconds. The |
| default is 2 seconds. |
| |
| @item show sdstimeout |
| @kindex show sdstimeout |
| Show the current value of the SDS timeout. |
| |
| @item sds @var{command} |
| @kindex sds@r{, a command} |
| Send the specified @var{command} string to the SDS monitor. |
| @end table |
| |
| |
| @node PA |
| @subsection HP PA Embedded |
| |
| @table @code |
| |
| @kindex target op50n |
| @item target op50n @var{dev} |
| OP50N monitor, running on an OKI HPPA board. |
| |
| @kindex target w89k |
| @item target w89k @var{dev} |
| W89K monitor, running on a Winbond HPPA board. |
| |
| @end table |
| |
| @node Sparclet |
| @subsection Tsqware Sparclet |
| |
| @cindex Sparclet |
| |
| @value{GDBN} enables developers to debug tasks running on |
| Sparclet targets from a Unix host. |
| @value{GDBN} uses code that runs on |
| both the Unix host and on the Sparclet target. The program |
| @code{@value{GDBP}} is installed and executed on the Unix host. |
| |
| @table @code |
| @item remotetimeout @var{args} |
| @kindex remotetimeout |
| @value{GDBN} supports the option @code{remotetimeout}. |
| This option is set by the user, and @var{args} represents the number of |
| seconds @value{GDBN} waits for responses. |
| @end table |
| |
| @cindex compiling, on Sparclet |
| When compiling for debugging, include the options @samp{-g} to get debug |
| information and @samp{-Ttext} to relocate the program to where you wish to |
| load it on the target. You may also want to add the options @samp{-n} or |
| @samp{-N} in order to reduce the size of the sections. Example: |
| |
| @smallexample |
| sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N |
| @end smallexample |
| |
| You can use @code{objdump} to verify that the addresses are what you intended: |
| |
| @smallexample |
| sparclet-aout-objdump --headers --syms prog |
| @end smallexample |
| |
| @cindex running, on Sparclet |
| Once you have set |
| your Unix execution search path to find @value{GDBN}, you are ready to |
| run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} |
| (or @code{sparclet-aout-gdb}, depending on your installation). |
| |
| @value{GDBN} comes up showing the prompt: |
| |
| @smallexample |
| (gdbslet) |
| @end smallexample |
| |
| @menu |
| * Sparclet File:: Setting the file to debug |
| * Sparclet Connection:: Connecting to Sparclet |
| * Sparclet Download:: Sparclet download |
| * Sparclet Execution:: Running and debugging |
| @end menu |
| |
| @node Sparclet File |
| @subsubsection Setting File to Debug |
| |
| The @value{GDBN} command @code{file} lets you choose with program to debug. |
| |
| @smallexample |
| (gdbslet) file prog |
| @end smallexample |
| |
| @need 1000 |
| @value{GDBN} then attempts to read the symbol table of @file{prog}. |
| @value{GDBN} locates |
| the file by searching the directories listed in the command search |
| path. |
| If the file was compiled with debug information (option @samp{-g}), source |
| files will be searched as well. |
| @value{GDBN} locates |
| the source files by searching the directories listed in the directory search |
| path (@pxref{Environment, ,Your Program's Environment}). |
| If it fails |
| to find a file, it displays a message such as: |
| |
| @smallexample |
| prog: No such file or directory. |
| @end smallexample |
| |
| When this happens, add the appropriate directories to the search paths with |
| the @value{GDBN} commands @code{path} and @code{dir}, and execute the |
| @code{target} command again. |
| |
| @node Sparclet Connection |
| @subsubsection Connecting to Sparclet |
| |
| The @value{GDBN} command @code{target} lets you connect to a Sparclet target. |
| To connect to a target on serial port ``@code{ttya}'', type: |
| |
| @smallexample |
| (gdbslet) target sparclet /dev/ttya |
| Remote target sparclet connected to /dev/ttya |
| main () at ../prog.c:3 |
| @end smallexample |
| |
| @need 750 |
| @value{GDBN} displays messages like these: |
| |
| @smallexample |
| Connected to ttya. |
| @end smallexample |
| |
| @node Sparclet Download |
| @subsubsection Sparclet Download |
| |
| @cindex download to Sparclet |
| Once connected to the Sparclet target, |
| you can use the @value{GDBN} |
| @code{load} command to download the file from the host to the target. |
| The file name and load offset should be given as arguments to the @code{load} |
| command. |
| Since the file format is aout, the program must be loaded to the starting |
| address. You can use @code{objdump} to find out what this value is. The load |
| offset is an offset which is added to the VMA (virtual memory address) |
| of each of the file's sections. |
| For instance, if the program |
| @file{prog} was linked to text address 0x1201000, with data at 0x12010160 |
| and bss at 0x12010170, in @value{GDBN}, type: |
| |
| @smallexample |
| (gdbslet) load prog 0x12010000 |
| Loading section .text, size 0xdb0 vma 0x12010000 |
| @end smallexample |
| |
| If the code is loaded at a different address then what the program was linked |
| to, you may need to use the @code{section} and @code{add-symbol-file} commands |
| to tell @value{GDBN} where to map the symbol table. |
| |
| @node Sparclet Execution |
| @subsubsection Running and Debugging |
| |
| @cindex running and debugging Sparclet programs |
| You can now begin debugging the task using @value{GDBN}'s execution control |
| commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN} |
| manual for the list of commands. |
| |
| @smallexample |
| (gdbslet) b main |
| Breakpoint 1 at 0x12010000: file prog.c, line 3. |
| (gdbslet) run |
| Starting program: prog |
| Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3 |
| 3 char *symarg = 0; |
| (gdbslet) step |
| 4 char *execarg = "hello!"; |
| (gdbslet) |
| @end smallexample |
| |
| @node Sparclite |
| @subsection Fujitsu Sparclite |
| |
| @table @code |
| |
| @kindex target sparclite |
| @item target sparclite @var{dev} |
| Fujitsu sparclite boards, used only for the purpose of loading. |
| You must use an additional command to debug the program. |
| For example: target remote @var{dev} using @value{GDBN} standard |
| remote protocol. |
| |
| @end table |
| |
| @node Z8000 |
| @subsection Zilog Z8000 |
| |
| @cindex Z8000 |
| @cindex simulator, Z8000 |
| @cindex Zilog Z8000 simulator |
| |
| When configured for debugging Zilog Z8000 targets, @value{GDBN} includes |
| a Z8000 simulator. |
| |
| For the Z8000 family, @samp{target sim} simulates either the Z8002 (the |
| unsegmented variant of the Z8000 architecture) or the Z8001 (the |
| segmented variant). The simulator recognizes which architecture is |
| appropriate by inspecting the object code. |
| |
| @table @code |
| @item target sim @var{args} |
| @kindex sim |
| @kindex target sim@r{, with Z8000} |
| Debug programs on a simulated CPU. If the simulator supports setup |
| options, specify them via @var{args}. |
| @end table |
| |
| @noindent |
| After specifying this target, you can debug programs for the simulated |
| CPU in the same style as programs for your host computer; use the |
| @code{file} command to load a new program image, the @code{run} command |
| to run your program, and so on. |
| |
| As well as making available all the usual machine registers |
| (@pxref{Registers, ,Registers}), the Z8000 simulator provides three |
| additional items of information as specially named registers: |
| |
| @table @code |
| |
| @item cycles |
| Counts clock-ticks in the simulator. |
| |
| @item insts |
| Counts instructions run in the simulator. |
| |
| @item time |
| Execution time in 60ths of a second. |
| |
| @end table |
| |
| You can refer to these values in @value{GDBN} expressions with the usual |
| conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a |
| conditional breakpoint that suspends only after at least 5000 |
| simulated clock ticks. |
| |
| @node AVR |
| @subsection Atmel AVR |
| @cindex AVR |
| |
| When configured for debugging the Atmel AVR, @value{GDBN} supports the |
| following AVR-specific commands: |
| |
| @table @code |
| @item info io_registers |
| @kindex info io_registers@r{, AVR} |
| @cindex I/O registers (Atmel AVR) |
| This command displays information about the AVR I/O registers. For |
| each register, @value{GDBN} prints its number and value. |
| @end table |
| |
| @node CRIS |
| @subsection CRIS |
| @cindex CRIS |
| |
| When configured for debugging CRIS, @value{GDBN} provides the |
| following CRIS-specific commands: |
| |
| @table @code |
| @item set cris-version @var{ver} |
| @cindex CRIS version |
| Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}. |
| The CRIS version affects register names and sizes. This command is useful in |
| case autodetection of the CRIS version fails. |
| |
| @item show cris-version |
| Show the current CRIS version. |
| |
| @item set cris-dwarf2-cfi |
| @cindex DWARF-2 CFI and CRIS |
| Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}. |
| Change to @samp{off} when using @code{gcc-cris} whose version is below |
| @code{R59}. |
| |
| @item show cris-dwarf2-cfi |
| Show the current state of using DWARF-2 CFI. |
| |
| @item set cris-mode @var{mode} |
| @cindex CRIS mode |
| Set the current CRIS mode to @var{mode}. It should only be changed when |
| debugging in guru mode, in which case it should be set to |
| @samp{guru} (the default is @samp{normal}). |
| |
| @item show cris-mode |
| Show the current CRIS mode. |
| @end table |
| |
| @node Super-H |
| @subsection Renesas Super-H |
| @cindex Super-H |
| |
| For the Renesas Super-H processor, @value{GDBN} provides these |
| commands: |
| |
| @table @code |
| @item regs |
| @kindex regs@r{, Super-H} |
| This command is deprecated, and @code{info all-registers} should be |
| used instead. |
| |
| Show the values of all Super-H registers. |
| |
| @item set sh calling-convention @var{convention} |
| @kindex set sh calling-convention |
| Set the calling-convention used when calling functions from @value{GDBN}. |
| Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}. |
| With the @samp{gcc} setting, functions are called using the @value{NGCC} calling |
| convention. If the DWARF-2 information of the called function specifies |
| that the function follows the Renesas calling convention, the function |
| is called using the Renesas calling convention. If the calling convention |
| is set to @samp{renesas}, the Renesas calling convention is always used, |
| regardless of the DWARF-2 information. This can be used to override the |
| default of @samp{gcc} if debug information is missing, or the compiler |
| does not emit the DWARF-2 calling convention entry for a function. |
| |
| @item show sh calling-convention |
| @kindex show sh calling-convention |
| Show the current calling convention setting. |
| |
| @end table |
| |
| |
| @node Architectures |
| @section Architectures |
| |
| This section describes characteristics of architectures that affect |
| all uses of @value{GDBN} with the architecture, both native and cross. |
| |
| @menu |
| * i386:: |
| * Alpha:: |
| * MIPS:: |
| * HPPA:: HP PA architecture |
| * SPU:: Cell Broadband Engine SPU architecture |
| * PowerPC:: |
| @end menu |
| |
| @node i386 |
| @subsection x86 Architecture-specific Issues |
| |
| @table @code |
| @item set struct-convention @var{mode} |
| @kindex set struct-convention |
| @cindex struct return convention |
| @cindex struct/union returned in registers |
| Set the convention used by the inferior to return @code{struct}s and |
| @code{union}s from functions to @var{mode}. Possible values of |
| @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the |
| default). @code{"default"} or @code{"pcc"} means that @code{struct}s |
| are returned on the stack, while @code{"reg"} means that a |
| @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will |
| be returned in a register. |
| |
| @item show struct-convention |
| @kindex show struct-convention |
| Show the current setting of the convention to return @code{struct}s |
| from functions. |
| @end table |
| |
| @node Alpha |
| @subsection Alpha |
| |
| See the following section. |
| |
| @node MIPS |
| @subsection @acronym{MIPS} |
| |
| @cindex stack on Alpha |
| @cindex stack on @acronym{MIPS} |
| @cindex Alpha stack |
| @cindex @acronym{MIPS} stack |
| Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which |
| sometimes requires @value{GDBN} to search backward in the object code to |
| find the beginning of a function. |
| |
| @cindex response time, @acronym{MIPS} debugging |
| To improve response time (especially for embedded applications, where |
| @value{GDBN} may be restricted to a slow serial line for this search) |
| you may want to limit the size of this search, using one of these |
| commands: |
| |
| @table @code |
| @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS}) |
| @item set heuristic-fence-post @var{limit} |
| Restrict @value{GDBN} to examining at most @var{limit} bytes in its |
| search for the beginning of a function. A value of @var{0} (the |
| default) means there is no limit. However, except for @var{0}, the |
| larger the limit the more bytes @code{heuristic-fence-post} must search |
| and therefore the longer it takes to run. You should only need to use |
| this command when debugging a stripped executable. |
| |
| @item show heuristic-fence-post |
| Display the current limit. |
| @end table |
| |
| @noindent |
| These commands are available @emph{only} when @value{GDBN} is configured |
| for debugging programs on Alpha or @acronym{MIPS} processors. |
| |
| Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS} |
| programs: |
| |
| @table @code |
| @item set mips abi @var{arg} |
| @kindex set mips abi |
| @cindex set ABI for @acronym{MIPS} |
| Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible |
| values of @var{arg} are: |
| |
| @table @samp |
| @item auto |
| The default ABI associated with the current binary (this is the |
| default). |
| @item o32 |
| @item o64 |
| @item n32 |
| @item n64 |
| @item eabi32 |
| @item eabi64 |
| @end table |
| |
| @item show mips abi |
| @kindex show mips abi |
| Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior. |
| |
| @item set mips compression @var{arg} |
| @kindex set mips compression |
| @cindex code compression, @acronym{MIPS} |
| Tell @value{GDBN} which @acronym{MIPS} compressed |
| @acronym{ISA, Instruction Set Architecture} encoding is used by the |
| inferior. @value{GDBN} uses this for code disassembly and other |
| internal interpretation purposes. This setting is only referred to |
| when no executable has been associated with the debugging session or |
| the executable does not provide information about the encoding it uses. |
| Otherwise this setting is automatically updated from information |
| provided by the executable. |
| |
| Possible values of @var{arg} are @samp{mips16} and @samp{micromips}. |
| The default compressed @acronym{ISA} encoding is @samp{mips16}, as |
| executables containing @acronym{MIPS16} code frequently are not |
| identified as such. |
| |
| This setting is ``sticky''; that is, it retains its value across |
| debugging sessions until reset either explicitly with this command or |
| implicitly from an executable. |
| |
| The compiler and/or assembler typically add symbol table annotations to |
| identify functions compiled for the @acronym{MIPS16} or |
| @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations |
| are present, @value{GDBN} uses them in preference to the global |
| compressed @acronym{ISA} encoding setting. |
| |
| @item show mips compression |
| @kindex show mips compression |
| Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by |
| @value{GDBN} to debug the inferior. |
| |
| @item set mipsfpu |
| @itemx show mipsfpu |
| @xref{MIPS Embedded, set mipsfpu}. |
| |
| @item set mips mask-address @var{arg} |
| @kindex set mips mask-address |
| @cindex @acronym{MIPS} addresses, masking |
| This command determines whether the most-significant 32 bits of 64-bit |
| @acronym{MIPS} addresses are masked off. The argument @var{arg} can be |
| @samp{on}, @samp{off}, or @samp{auto}. The latter is the default |
| setting, which lets @value{GDBN} determine the correct value. |
| |
| @item show mips mask-address |
| @kindex show mips mask-address |
| Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or |
| not. |
| |
| @item set remote-mips64-transfers-32bit-regs |
| @kindex set remote-mips64-transfers-32bit-regs |
| This command controls compatibility with 64-bit @acronym{MIPS} targets that |
| transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target |
| that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr}, |
| and 64 bits for other registers, set this option to @samp{on}. |
| |
| @item show remote-mips64-transfers-32bit-regs |
| @kindex show remote-mips64-transfers-32bit-regs |
| Show the current setting of compatibility with older @acronym{MIPS} 64 targets. |
| |
| @item set debug mips |
| @kindex set debug mips |
| This command turns on and off debugging messages for the @acronym{MIPS}-specific |
| target code in @value{GDBN}. |
| |
| @item show debug mips |
| @kindex show debug mips |
| Show the current setting of @acronym{MIPS} debugging messages. |
| @end table |
| |
| |
| @node HPPA |
| @subsection HPPA |
| @cindex HPPA support |
| |
| When @value{GDBN} is debugging the HP PA architecture, it provides the |
| following special commands: |
| |
| @table @code |
| @item set debug hppa |
| @kindex set debug hppa |
| This command determines whether HPPA architecture-specific debugging |
| messages are to be displayed. |
| |
| @item show debug hppa |
| Show whether HPPA debugging messages are displayed. |
| |
| @item maint print unwind @var{address} |
| @kindex maint print unwind@r{, HPPA} |
| This command displays the contents of the unwind table entry at the |
| given @var{address}. |
| |
| @end table |
| |
| |
| @node SPU |
| @subsection Cell Broadband Engine SPU architecture |
| @cindex Cell Broadband Engine |
| @cindex SPU |
| |
| When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture, |
| it provides the following special commands: |
| |
| @table @code |
| @item info spu event |
| @kindex info spu |
| Display SPU event facility status. Shows current event mask |
| and pending event status. |
| |
| @item info spu signal |
| Display SPU signal notification facility status. Shows pending |
| signal-control word and signal notification mode of both signal |
| notification channels. |
| |
| @item info spu mailbox |
| Display SPU mailbox facility status. Shows all pending entries, |
| in order of processing, in each of the SPU Write Outbound, |
| SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes. |
| |
| @item info spu dma |
| Display MFC DMA status. Shows all pending commands in the MFC |
| DMA queue. For each entry, opcode, tag, class IDs, effective |
| and local store addresses and transfer size are shown. |
| |
| @item info spu proxydma |
| Display MFC Proxy-DMA status. Shows all pending commands in the MFC |
| Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective |
| and local store addresses and transfer size are shown. |
| |
| @end table |
| |
| When @value{GDBN} is debugging a combined PowerPC/SPU application |
| on the Cell Broadband Engine, it provides in addition the following |
| special commands: |
| |
| @table @code |
| @item set spu stop-on-load @var{arg} |
| @kindex set spu |
| Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN} |
| will give control to the user when a new SPE thread enters its @code{main} |
| function. The default is @code{off}. |
| |
| @item show spu stop-on-load |
| @kindex show spu |
| Show whether to stop for new SPE threads. |
| |
| @item set spu auto-flush-cache @var{arg} |
| Set whether to automatically flush the software-managed cache. When set to |
| @code{on}, @value{GDBN} will automatically cause the SPE software-managed |
| cache to be flushed whenever SPE execution stops. This provides a consistent |
| view of PowerPC memory that is accessed via the cache. If an application |
| does not use the software-managed cache, this option has no effect. |
| |
| @item show spu auto-flush-cache |
| Show whether to automatically flush the software-managed cache. |
| |
| @end table |
| |
| @node PowerPC |
| @subsection PowerPC |
| @cindex PowerPC architecture |
| |
| When @value{GDBN} is debugging the PowerPC architecture, it provides a set of |
| pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point |
| numbers stored in the floating point registers. These values must be stored |
| in two consecutive registers, always starting at an even register like |
| @code{f0} or @code{f2}. |
| |
| The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed |
| by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0}, |
| @code{f2} and @code{f3} for @code{$dl1} and so on. |
| |
| For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit |
| wide Extended Floating Point Registers (@samp{f32} through @samp{f63}). |
| |
| |
| @node Controlling GDB |
| @chapter Controlling @value{GDBN} |
| |
| You can alter the way @value{GDBN} interacts with you by using the |
| @code{set} command. For commands controlling how @value{GDBN} displays |
| data, see @ref{Print Settings, ,Print Settings}. Other settings are |
| described here. |
| |
| @menu |
| * Prompt:: Prompt |
| * Editing:: Command editing |
| * Command History:: Command history |
| * Screen Size:: Screen size |
| * Numbers:: Numbers |
| * ABI:: Configuring the current ABI |
| * Auto-loading:: Automatically loading associated files |
| * Messages/Warnings:: Optional warnings and messages |
| * Debugging Output:: Optional messages about internal happenings |
| * Other Misc Settings:: Other Miscellaneous Settings |
| @end menu |
| |
| @node Prompt |
| @section Prompt |
| |
| @cindex prompt |
| |
| @value{GDBN} indicates its readiness to read a command by printing a string |
| called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You |
| can change the prompt string with the @code{set prompt} command. For |
| instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change |
| the prompt in one of the @value{GDBN} sessions so that you can always tell |
| which one you are talking to. |
| |
| @emph{Note:} @code{set prompt} does not add a space for you after the |
| prompt you set. This allows you to set a prompt which ends in a space |
| or a prompt that does not. |
| |
| @table @code |
| @kindex set prompt |
| @item set prompt @var{newprompt} |
| Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth. |
| |
| @kindex show prompt |
| @item show prompt |
| Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}} |
| @end table |
| |
| Versions of @value{GDBN} that ship with Python scripting enabled have |
| prompt extensions. The commands for interacting with these extensions |
| are: |
| |
| @table @code |
| @kindex set extended-prompt |
| @item set extended-prompt @var{prompt} |
| Set an extended prompt that allows for substitutions. |
| @xref{gdb.prompt}, for a list of escape sequences that can be used for |
| substitution. Any escape sequences specified as part of the prompt |
| string are replaced with the corresponding strings each time the prompt |
| is displayed. |
| |
| For example: |
| |
| @smallexample |
| set extended-prompt Current working directory: \w (gdb) |
| @end smallexample |
| |
| Note that when an extended-prompt is set, it takes control of the |
| @var{prompt_hook} hook. @xref{prompt_hook}, for further information. |
| |
| @kindex show extended-prompt |
| @item show extended-prompt |
| Prints the extended prompt. Any escape sequences specified as part of |
| the prompt string with @code{set extended-prompt}, are replaced with the |
| corresponding strings each time the prompt is displayed. |
| @end table |
| |
| @node Editing |
| @section Command Editing |
| @cindex readline |
| @cindex command line editing |
| |
| @value{GDBN} reads its input commands via the @dfn{Readline} interface. This |
| @sc{gnu} library provides consistent behavior for programs which provide a |
| command line interface to the user. Advantages are @sc{gnu} Emacs-style |
| or @dfn{vi}-style inline editing of commands, @code{csh}-like history |
| substitution, and a storage and recall of command history across |
| debugging sessions. |
| |
| You may control the behavior of command line editing in @value{GDBN} with the |
| command @code{set}. |
| |
| @table @code |
| @kindex set editing |
| @cindex editing |
| @item set editing |
| @itemx set editing on |
| Enable command line editing (enabled by default). |
| |
| @item set editing off |
| Disable command line editing. |
| |
| @kindex show editing |
| @item show editing |
| Show whether command line editing is enabled. |
| @end table |
| |
| @ifset SYSTEM_READLINE |
| @xref{Command Line Editing, , , rluserman, GNU Readline Library}, |
| @end ifset |
| @ifclear SYSTEM_READLINE |
| @xref{Command Line Editing}, |
| @end ifclear |
| for more details about the Readline |
| interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are |
| encouraged to read that chapter. |
| |
| @node Command History |
| @section Command History |
| @cindex command history |
| |
| @value{GDBN} can keep track of the commands you type during your |
| debugging sessions, so that you can be certain of precisely what |
| happened. Use these commands to manage the @value{GDBN} command |
| history facility. |
| |
| @value{GDBN} uses the @sc{gnu} History library, a part of the Readline |
| package, to provide the history facility. |
| @ifset SYSTEM_READLINE |
| @xref{Using History Interactively, , , history, GNU History Library}, |
| @end ifset |
| @ifclear SYSTEM_READLINE |
| @xref{Using History Interactively}, |
| @end ifclear |
| for the detailed description of the History library. |
| |
| To issue a command to @value{GDBN} without affecting certain aspects of |
| the state which is seen by users, prefix it with @samp{server } |
| (@pxref{Server Prefix}). This |
| means that this command will not affect the command history, nor will it |
| affect @value{GDBN}'s notion of which command to repeat if @key{RET} is |
| pressed on a line by itself. |
| |
| @cindex @code{server}, command prefix |
| The server prefix does not affect the recording of values into the value |
| history; to print a value without recording it into the value history, |
| use the @code{output} command instead of the @code{print} command. |
| |
| Here is the description of @value{GDBN} commands related to command |
| history. |
| |
| @table @code |
| @cindex history substitution |
| @cindex history file |
| @kindex set history filename |
| @cindex @env{GDBHISTFILE}, environment variable |
| @item set history filename @var{fname} |
| Set the name of the @value{GDBN} command history file to @var{fname}. |
| This is the file where @value{GDBN} reads an initial command history |
| list, and where it writes the command history from this session when it |
| exits. You can access this list through history expansion or through |
| the history command editing characters listed below. This file defaults |
| to the value of the environment variable @code{GDBHISTFILE}, or to |
| @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable |
| is not set. |
| |
| @cindex save command history |
| @kindex set history save |
| @item set history save |
| @itemx set history save on |
| Record command history in a file, whose name may be specified with the |
| @code{set history filename} command. By default, this option is disabled. |
| |
| @item set history save off |
| Stop recording command history in a file. |
| |
| @cindex history size |
| @kindex set history size |
| @cindex @env{HISTSIZE}, environment variable |
| @item set history size @var{size} |
| Set the number of commands which @value{GDBN} keeps in its history list. |
| This defaults to the value of the environment variable |
| @code{HISTSIZE}, or to 256 if this variable is not set. |
| @end table |
| |
| History expansion assigns special meaning to the character @kbd{!}. |
| @ifset SYSTEM_READLINE |
| @xref{Event Designators, , , history, GNU History Library}, |
| @end ifset |
| @ifclear SYSTEM_READLINE |
| @xref{Event Designators}, |
| @end ifclear |
| for more details. |
| |
| @cindex history expansion, turn on/off |
| Since @kbd{!} is also the logical not operator in C, history expansion |
| is off by default. If you decide to enable history expansion with the |
| @code{set history expansion on} command, you may sometimes need to |
| follow @kbd{!} (when it is used as logical not, in an expression) with |
| a space or a tab to prevent it from being expanded. The readline |
| history facilities do not attempt substitution on the strings |
| @kbd{!=} and @kbd{!(}, even when history expansion is enabled. |
| |
| The commands to control history expansion are: |
| |
| @table @code |
| @item set history expansion on |
| @itemx set history expansion |
| @kindex set history expansion |
| Enable history expansion. History expansion is off by default. |
| |
| @item set history expansion off |
| Disable history expansion. |
| |
| @c @group |
| @kindex show history |
| @item show history |
| @itemx show history filename |
| @itemx show history save |
| @itemx show history size |
| @itemx show history expansion |
| These commands display the state of the @value{GDBN} history parameters. |
| @code{show history} by itself displays all four states. |
| @c @end group |
| @end table |
| |
| @table @code |
| @kindex show commands |
| @cindex show last commands |
| @cindex display command history |
| @item show commands |
| Display the last ten commands in the command history. |
| |
| @item show commands @var{n} |
| Print ten commands centered on command number @var{n}. |
| |
| @item show commands + |
| Print ten commands just after the commands last printed. |
| @end table |
| |
| @node Screen Size |
| @section Screen Size |
| @cindex size of screen |
| @cindex pauses in output |
| |
| Certain commands to @value{GDBN} may produce large amounts of |
| information output to the screen. To help you read all of it, |
| @value{GDBN} pauses and asks you for input at the end of each page of |
| output. Type @key{RET} when you want to continue the output, or @kbd{q} |
| to discard the remaining output. Also, the screen width setting |
| determines when to wrap lines of output. Depending on what is being |
| printed, @value{GDBN} tries to break the line at a readable place, |
| rather than simply letting it overflow onto the following line. |
| |
| Normally @value{GDBN} knows the size of the screen from the terminal |
| driver software. For example, on Unix @value{GDBN} uses the termcap data base |
| together with the value of the @code{TERM} environment variable and the |
| @code{stty rows} and @code{stty cols} settings. If this is not correct, |
| you can override it with the @code{set height} and @code{set |
| width} commands: |
| |
| @table @code |
| @kindex set height |
| @kindex set width |
| @kindex show width |
| @kindex show height |
| @item set height @var{lpp} |
| @itemx show height |
| @itemx set width @var{cpl} |
| @itemx show width |
| These @code{set} commands specify a screen height of @var{lpp} lines and |
| a screen width of @var{cpl} characters. The associated @code{show} |
| commands display the current settings. |
| |
| If you specify a height of zero lines, @value{GDBN} does not pause during |
| output no matter how long the output is. This is useful if output is to a |
| file or to an editor buffer. |
| |
| Likewise, you can specify @samp{set width 0} to prevent @value{GDBN} |
| from wrapping its output. |
| |
| @item set pagination on |
| @itemx set pagination off |
| @kindex set pagination |
| Turn the output pagination on or off; the default is on. Turning |
| pagination off is the alternative to @code{set height 0}. Note that |
| running @value{GDBN} with the @option{--batch} option (@pxref{Mode |
| Options, -batch}) also automatically disables pagination. |
| |
| @item show pagination |
| @kindex show pagination |
| Show the current pagination mode. |
| @end table |
| |
| @node Numbers |
| @section Numbers |
| @cindex number representation |
| @cindex entering numbers |
| |
| You can always enter numbers in octal, decimal, or hexadecimal in |
| @value{GDBN} by the usual conventions: octal numbers begin with |
| @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers |
| begin with @samp{0x}. Numbers that neither begin with @samp{0} or |
| @samp{0x}, nor end with a @samp{.} are, by default, entered in base |
| 10; likewise, the default display for numbers---when no particular |
| format is specified---is base 10. You can change the default base for |
| both input and output with the commands described below. |
| |
| @table @code |
| @kindex set input-radix |
| @item set input-radix @var{base} |
| Set the default base for numeric input. Supported choices |
| for @var{base} are decimal 8, 10, or 16. @var{base} must itself be |
| specified either unambiguously or using the current input radix; for |
| example, any of |
| |
| @smallexample |
| set input-radix 012 |
| set input-radix 10. |
| set input-radix 0xa |
| @end smallexample |
| |
| @noindent |
| sets the input base to decimal. On the other hand, @samp{set input-radix 10} |
| leaves the input radix unchanged, no matter what it was, since |
| @samp{10}, being without any leading or trailing signs of its base, is |
| interpreted in the current radix. Thus, if the current radix is 16, |
| @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't |
| change the radix. |
| |
| @kindex set output-radix |
| @item set output-radix @var{base} |
| Set the default base for numeric display. Supported choices |
| for @var{base} are decimal 8, 10, or 16. @var{base} must itself be |
| specified either unambiguously or using the current input radix. |
| |
| @kindex show input-radix |
| @item show input-radix |
| Display the current default base for numeric input. |
| |
| @kindex show output-radix |
| @item show output-radix |
| Display the current default base for numeric display. |
| |
| @item set radix @r{[}@var{base}@r{]} |
| @itemx show radix |
| @kindex set radix |
| @kindex show radix |
| These commands set and show the default base for both input and output |
| of numbers. @code{set radix} sets the radix of input and output to |
| the same base; without an argument, it resets the radix back to its |
| default value of 10. |
| |
| @end table |
| |
| @node ABI |
| @section Configuring the Current ABI |
| |
| @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your |
| application automatically. However, sometimes you need to override its |
| conclusions. Use these commands to manage @value{GDBN}'s view of the |
| current ABI. |
| |
| @cindex OS ABI |
| @kindex set osabi |
| @kindex show osabi |
| |
| One @value{GDBN} configuration can debug binaries for multiple operating |
| system targets, either via remote debugging or native emulation. |
| @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use, |
| but you can override its conclusion using the @code{set osabi} command. |
| One example where this is useful is in debugging of binaries which use |
| an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does |
| not have the same identifying marks that the standard C library for your |
| platform provides. |
| |
| @table @code |
| @item show osabi |
| Show the OS ABI currently in use. |
| |
| @item set osabi |
| With no argument, show the list of registered available OS ABI's. |
| |
| @item set osabi @var{abi} |
| Set the current OS ABI to @var{abi}. |
| @end table |
| |
| @cindex float promotion |
| |
| Generally, the way that an argument of type @code{float} is passed to a |
| function depends on whether the function is prototyped. For a prototyped |
| (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged, |
| according to the architecture's convention for @code{float}. For unprototyped |
| (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type |
| @code{double} and then passed. |
| |
| Unfortunately, some forms of debug information do not reliably indicate whether |
| a function is prototyped. If @value{GDBN} calls a function that is not marked |
| as prototyped, it consults @kbd{set coerce-float-to-double}. |
| |
| @table @code |
| @kindex set coerce-float-to-double |
| @item set coerce-float-to-double |
| @itemx set coerce-float-to-double on |
| Arguments of type @code{float} will be promoted to @code{double} when passed |
| to an unprototyped function. This is the default setting. |
| |
| @item set coerce-float-to-double off |
| Arguments of type @code{float} will be passed directly to unprototyped |
| functions. |
| |
| @kindex show coerce-float-to-double |
| @item show coerce-float-to-double |
| Show the current setting of promoting @code{float} to @code{double}. |
| @end table |
| |
| @kindex set cp-abi |
| @kindex show cp-abi |
| @value{GDBN} needs to know the ABI used for your program's C@t{++} |
| objects. The correct C@t{++} ABI depends on which C@t{++} compiler was |
| used to build your application. @value{GDBN} only fully supports |
| programs with a single C@t{++} ABI; if your program contains code using |
| multiple C@t{++} ABI's or if @value{GDBN} can not identify your |
| program's ABI correctly, you can tell @value{GDBN} which ABI to use. |
| Currently supported ABI's include ``gnu-v2'', for @code{g++} versions |
| before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and |
| ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may |
| use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is |
| ``auto''. |
| |
| @table @code |
| @item show cp-abi |
| Show the C@t{++} ABI currently in use. |
| |
| @item set cp-abi |
| With no argument, show the list of supported C@t{++} ABI's. |
| |
| @item set cp-abi @var{abi} |
| @itemx set cp-abi auto |
| Set the current C@t{++} ABI to @var{abi}, or return to automatic detection. |
| @end table |
| |
| @node Auto-loading |
| @section Automatically loading associated files |
| @cindex auto-loading |
| |
| @value{GDBN} sometimes reads files with commands and settings automatically, |
| without being explicitly told so by the user. We call this feature |
| @dfn{auto-loading}. While auto-loading is useful for automatically adapting |
| @value{GDBN} to the needs of your project, it can sometimes produce unexpected |
| results or introduce security risks (e.g., if the file comes from untrusted |
| sources). |
| |
| Note that loading of these associated files (including the local @file{.gdbinit} |
| file) requires accordingly configured @code{auto-load safe-path} |
| (@pxref{Auto-loading safe path}). |
| |
| For these reasons, @value{GDBN} includes commands and options to let you |
| control when to auto-load files and which files should be auto-loaded. |
| |
| @table @code |
| @anchor{set auto-load off} |
| @kindex set auto-load off |
| @item set auto-load off |
| Globally disable loading of all auto-loaded files. |
| You may want to use this command with the @samp{-iex} option |
| (@pxref{Option -init-eval-command}) such as: |
| @smallexample |
| $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile} |
| @end smallexample |
| |
| Be aware that system init file (@pxref{System-wide configuration}) |
| and init files from your home directory (@pxref{Home Directory Init File}) |
| still get read (as they come from generally trusted directories). |
| To prevent @value{GDBN} from auto-loading even those init files, use the |
| @option{-nx} option (@pxref{Mode Options}), in addition to |
| @code{set auto-load no}. |
| |
| @anchor{show auto-load} |
| @kindex show auto-load |
| @item show auto-load |
| Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled |
| or disabled. |
| |
| @smallexample |
| (gdb) show auto-load |
| gdb-scripts: Auto-loading of canned sequences of commands scripts is on. |
| libthread-db: Auto-loading of inferior specific libthread_db is on. |
| local-gdbinit: Auto-loading of .gdbinit script from current directory |
| is on. |
| python-scripts: Auto-loading of Python scripts is on. |
| safe-path: List of directories from which it is safe to auto-load files |
| is $debugdir:$datadir/auto-load. |
| scripts-directory: List of directories from which to load auto-loaded scripts |
| is $debugdir:$datadir/auto-load. |
| @end smallexample |
| |
| @anchor{info auto-load} |
| @kindex info auto-load |
| @item info auto-load |
| Print whether each specific @samp{auto-load} file(s) have been auto-loaded or |
| not. |
| |
| @smallexample |
| (gdb) info auto-load |
| gdb-scripts: |
| Loaded Script |
| Yes /home/user/gdb/gdb-gdb.gdb |
| libthread-db: No auto-loaded libthread-db. |
| local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been |
| loaded. |
| python-scripts: |
| Loaded Script |
| Yes /home/user/gdb/gdb-gdb.py |
| @end smallexample |
| @end table |
| |
| These are various kinds of files @value{GDBN} can automatically load: |
| |
| @itemize @bullet |
| @item |
| @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}. |
| @item |
| @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}. |
| @item |
| @xref{dotdebug_gdb_scripts section}, |
| controlled by @ref{set auto-load python-scripts}. |
| @item |
| @xref{Init File in the Current Directory}, |
| controlled by @ref{set auto-load local-gdbinit}. |
| @item |
| @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}. |
| @end itemize |
| |
| These are @value{GDBN} control commands for the auto-loading: |
| |
| @multitable @columnfractions .5 .5 |
| @item @xref{set auto-load off}. |
| @tab Disable auto-loading globally. |
| @item @xref{show auto-load}. |
| @tab Show setting of all kinds of files. |
| @item @xref{info auto-load}. |
| @tab Show state of all kinds of files. |
| @item @xref{set auto-load gdb-scripts}. |
| @tab Control for @value{GDBN} command scripts. |
| @item @xref{show auto-load gdb-scripts}. |
| @tab Show setting of @value{GDBN} command scripts. |
| @item @xref{info auto-load gdb-scripts}. |
| @tab Show state of @value{GDBN} command scripts. |
| @item @xref{set auto-load python-scripts}. |
| @tab Control for @value{GDBN} Python scripts. |
| @item @xref{show auto-load python-scripts}. |
| @tab Show setting of @value{GDBN} Python scripts. |
| @item @xref{info auto-load python-scripts}. |
| @tab Show state of @value{GDBN} Python scripts. |
| @item @xref{set auto-load scripts-directory}. |
| @tab Control for @value{GDBN} auto-loaded scripts location. |
| @item @xref{show auto-load scripts-directory}. |
| @tab Show @value{GDBN} auto-loaded scripts location. |
| @item @xref{set auto-load local-gdbinit}. |
| @tab Control for init file in the current directory. |
| @item @xref{show auto-load local-gdbinit}. |
| @tab Show setting of init file in the current directory. |
| @item @xref{info auto-load local-gdbinit}. |
| @tab Show state of init file in the current directory. |
| @item @xref{set auto-load libthread-db}. |
| @tab Control for thread debugging library. |
| @item @xref{show auto-load libthread-db}. |
| @tab Show setting of thread debugging library. |
| @item @xref{info auto-load libthread-db}. |
| @tab Show state of thread debugging library. |
| @item @xref{set auto-load safe-path}. |
| @tab Control directories trusted for automatic loading. |
| @item @xref{show auto-load safe-path}. |
| @tab Show directories trusted for automatic loading. |
| @item @xref{add-auto-load-safe-path}. |
| @tab Add directory trusted for automatic loading. |
| @end multitable |
| |
| @menu |
| * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit} |
| * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db} |
| * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script} |
| * Auto-loading safe path:: @samp{set/show/info auto-load safe-path} |
| * Auto-loading verbose mode:: @samp{set/show debug auto-load} |
| @xref{Python Auto-loading}. |
| @end menu |
| |
| @node Init File in the Current Directory |
| @subsection Automatically loading init file in the current directory |
| @cindex auto-loading init file in the current directory |
| |
| By default, @value{GDBN} reads and executes the canned sequences of commands |
| from init file (if any) in the current working directory, |
| see @ref{Init File in the Current Directory during Startup}. |
| |
| Note that loading of this local @file{.gdbinit} file also requires accordingly |
| configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}). |
| |
| @table @code |
| @anchor{set auto-load local-gdbinit} |
| @kindex set auto-load local-gdbinit |
| @item set auto-load local-gdbinit [on|off] |
| Enable or disable the auto-loading of canned sequences of commands |
| (@pxref{Sequences}) found in init file in the current directory. |
| |
| @anchor{show auto-load local-gdbinit} |
| @kindex show auto-load local-gdbinit |
| @item show auto-load local-gdbinit |
| Show whether auto-loading of canned sequences of commands from init file in the |
| current directory is enabled or disabled. |
| |
| @anchor{info auto-load local-gdbinit} |
| @kindex info auto-load local-gdbinit |
| @item info auto-load local-gdbinit |
| Print whether canned sequences of commands from init file in the |
| current directory have been auto-loaded. |
| @end table |
| |
| @node libthread_db.so.1 file |
| @subsection Automatically loading thread debugging library |
| @cindex auto-loading libthread_db.so.1 |
| |
| This feature is currently present only on @sc{gnu}/Linux native hosts. |
| |
| @value{GDBN} reads in some cases thread debugging library from places specific |
| to the inferior (@pxref{set libthread-db-search-path}). |
| |
| The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed |
| without checking this @samp{set auto-load libthread-db} switch as system |
| libraries have to be trusted in general. In all other cases of |
| @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set |
| auto-load libthread-db} is enabled before trying to open such thread debugging |
| library. |
| |
| Note that loading of this debugging library also requires accordingly configured |
| @code{auto-load safe-path} (@pxref{Auto-loading safe path}). |
| |
| @table @code |
| @anchor{set auto-load libthread-db} |
| @kindex set auto-load libthread-db |
| @item set auto-load libthread-db [on|off] |
| Enable or disable the auto-loading of inferior specific thread debugging library. |
| |
| @anchor{show auto-load libthread-db} |
| @kindex show auto-load libthread-db |
| @item show auto-load libthread-db |
| Show whether auto-loading of inferior specific thread debugging library is |
| enabled or disabled. |
| |
| @anchor{info auto-load libthread-db} |
| @kindex info auto-load libthread-db |
| @item info auto-load libthread-db |
| Print the list of all loaded inferior specific thread debugging libraries and |
| for each such library print list of inferior @var{pid}s using it. |
| @end table |
| |
| @node objfile-gdb.gdb file |
| @subsection The @file{@var{objfile}-gdb.gdb} file |
| @cindex auto-loading @file{@var{objfile}-gdb.gdb} |
| |
| @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing |
| canned sequences of commands (@pxref{Sequences}), as long as @samp{set |
| auto-load gdb-scripts} is set to @samp{on}. |
| |
| Note that loading of this script file also requires accordingly configured |
| @code{auto-load safe-path} (@pxref{Auto-loading safe path}). |
| |
| For more background refer to the similar Python scripts auto-loading |
| description (@pxref{objfile-gdb.py file}). |
| |
| @table @code |
| @anchor{set auto-load gdb-scripts} |
| @kindex set auto-load gdb-scripts |
| @item set auto-load gdb-scripts [on|off] |
| Enable or disable the auto-loading of canned sequences of commands scripts. |
| |
| @anchor{show auto-load gdb-scripts} |
| @kindex show auto-load gdb-scripts |
| @item show auto-load gdb-scripts |
| Show whether auto-loading of canned sequences of commands scripts is enabled or |
| disabled. |
| |
| @anchor{info auto-load gdb-scripts} |
| @kindex info auto-load gdb-scripts |
| @cindex print list of auto-loaded canned sequences of commands scripts |
| @item info auto-load gdb-scripts [@var{regexp}] |
| Print the list of all canned sequences of commands scripts that @value{GDBN} |
| auto-loaded. |
| @end table |
| |
| If @var{regexp} is supplied only canned sequences of commands scripts with |
| matching names are printed. |
| |
| @node Auto-loading safe path |
| @subsection Security restriction for auto-loading |
| @cindex auto-loading safe-path |
| |
| As the files of inferior can come from untrusted source (such as submitted by |
| an application user) @value{GDBN} does not always load any files automatically. |
| @value{GDBN} provides the @samp{set auto-load safe-path} setting to list |
| directories trusted for loading files not explicitly requested by user. |
| Each directory can also be a shell wildcard pattern. |
| |
| If the path is not set properly you will see a warning and the file will not |
| get loaded: |
| |
| @smallexample |
| $ ./gdb -q ./gdb |
| Reading symbols from /home/user/gdb/gdb...done. |
| warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been |
| declined by your `auto-load safe-path' set |
| to "$debugdir:$datadir/auto-load". |
| warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been |
| declined by your `auto-load safe-path' set |
| to "$debugdir:$datadir/auto-load". |
| @end smallexample |
| |
| The list of trusted directories is controlled by the following commands: |
| |
| @table @code |
| @anchor{set auto-load safe-path} |
| @kindex set auto-load safe-path |
| @item set auto-load safe-path @r{[}@var{directories}@r{]} |
| Set the list of directories (and their subdirectories) trusted for automatic |
| loading and execution of scripts. You can also enter a specific trusted file. |
| Each directory can also be a shell wildcard pattern; wildcards do not match |
| directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch} |
| (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}). |
| If you omit @var{directories}, @samp{auto-load safe-path} will be reset to |
| its default value as specified during @value{GDBN} compilation. |
| |
| The list of directories uses path separator (@samp{:} on GNU and Unix |
| systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly |
| to the @env{PATH} environment variable. |
| |
| @anchor{show auto-load safe-path} |
| @kindex show auto-load safe-path |
| @item show auto-load safe-path |
| Show the list of directories trusted for automatic loading and execution of |
| scripts. |
| |
| @anchor{add-auto-load-safe-path} |
| @kindex add-auto-load-safe-path |
| @item add-auto-load-safe-path |
| Add an entry (or list of entries) the list of directories trusted for automatic |
| loading and execution of scripts. Multiple entries may be delimited by the |
| host platform path separator in use. |
| @end table |
| |
| This variable defaults to what @code{--with-auto-load-dir} has been configured |
| to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir} |
| substitution applies the same as for @ref{set auto-load scripts-directory}. |
| The default @code{set auto-load safe-path} value can be also overriden by |
| @value{GDBN} configuration option @option{--with-auto-load-safe-path}. |
| |
| Setting this variable to @file{/} disables this security protection, |
| corresponding @value{GDBN} configuration option is |
| @option{--without-auto-load-safe-path}. |
| This variable is supposed to be set to the system directories writable by the |
| system superuser only. Users can add their source directories in init files in |
| their home directories (@pxref{Home Directory Init File}). See also deprecated |
| init file in the current directory |
| (@pxref{Init File in the Current Directory during Startup}). |
| |
| To force @value{GDBN} to load the files it declined to load in the previous |
| example, you could use one of the following ways: |
| |
| @table @asis |
| @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb} |
| Specify this trusted directory (or a file) as additional component of the list. |
| You have to specify also any existing directories displayed by |
| by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example). |
| |
| @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}} |
| Specify this directory as in the previous case but just for a single |
| @value{GDBN} session. |
| |
| @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}} |
| Disable auto-loading safety for a single @value{GDBN} session. |
| This assumes all the files you debug during this @value{GDBN} session will come |
| from trusted sources. |
| |
| @item @kbd{./configure --without-auto-load-safe-path} |
| During compilation of @value{GDBN} you may disable any auto-loading safety. |
| This assumes all the files you will ever debug with this @value{GDBN} come from |
| trusted sources. |
| @end table |
| |
| On the other hand you can also explicitly forbid automatic files loading which |
| also suppresses any such warning messages: |
| |
| @table @asis |
| @item @kbd{gdb -iex "set auto-load no" @dots{}} |
| You can use @value{GDBN} command-line option for a single @value{GDBN} session. |
| |
| @item @file{~/.gdbinit}: @samp{set auto-load no} |
| Disable auto-loading globally for the user |
| (@pxref{Home Directory Init File}). While it is improbable, you could also |
| use system init file instead (@pxref{System-wide configuration}). |
| @end table |
| |
| This setting applies to the file names as entered by user. If no entry matches |
| @value{GDBN} tries as a last resort to also resolve all the file names into |
| their canonical form (typically resolving symbolic links) and compare the |
| entries again. @value{GDBN} already canonicalizes most of the filenames on its |
| own before starting the comparison so a canonical form of directories is |
| recommended to be entered. |
| |
| @node Auto-loading verbose mode |
| @subsection Displaying files tried for auto-load |
| @cindex auto-loading verbose mode |
| |
| For better visibility of all the file locations where you can place scripts to |
| be auto-loaded with inferior --- or to protect yourself against accidental |
| execution of untrusted scripts --- @value{GDBN} provides a feature for printing |
| all the files attempted to be loaded. Both existing and non-existing files may |
| be printed. |
| |
| For example the list of directories from which it is safe to auto-load files |
| (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which |
| may not be too obvious while setting it up. |
| |
| @smallexample |
| (gdb) set debug auto-load on |
| (gdb) file ~/src/t/true |
| auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb" |
| for objfile "/tmp/true". |
| auto-load: Updating directories of "/usr:/opt". |
| auto-load: Using directory "/usr". |
| auto-load: Using directory "/opt". |
| warning: File "/tmp/true-gdb.gdb" auto-loading has been declined |
| by your `auto-load safe-path' set to "/usr:/opt". |
| @end smallexample |
| |
| @table @code |
| @anchor{set debug auto-load} |
| @kindex set debug auto-load |
| @item set debug auto-load [on|off] |
| Set whether to print the filenames attempted to be auto-loaded. |
| |
| @anchor{show debug auto-load} |
| @kindex show debug auto-load |
| @item show debug auto-load |
| Show whether printing of the filenames attempted to be auto-loaded is turned |
| on or off. |
| @end table |
| |
| @node Messages/Warnings |
| @section Optional Warnings and Messages |
| |
| @cindex verbose operation |
| @cindex optional warnings |
| By default, @value{GDBN} is silent about its inner workings. If you are |
| running on a slow machine, you may want to use the @code{set verbose} |
| command. This makes @value{GDBN} tell you when it does a lengthy |
| internal operation, so you will not think it has crashed. |
| |
| Currently, the messages controlled by @code{set verbose} are those |
| which announce that the symbol table for a source file is being read; |
| see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}. |
| |
| @table @code |
| @kindex set verbose |
| @item set verbose on |
| Enables @value{GDBN} output of certain informational messages. |
| |
| @item set verbose off |
| Disables @value{GDBN} output of certain informational messages. |
| |
| @kindex show verbose |
| @item show verbose |
| Displays whether @code{set verbose} is on or off. |
| @end table |
| |
| By default, if @value{GDBN} encounters bugs in the symbol table of an |
| object file, it is silent; but if you are debugging a compiler, you may |
| find this information useful (@pxref{Symbol Errors, ,Errors Reading |
| Symbol Files}). |
| |
| @table @code |
| |
| @kindex set complaints |
| @item set complaints @var{limit} |
| Permits @value{GDBN} to output @var{limit} complaints about each type of |
| unusual symbols before becoming silent about the problem. Set |
| @var{limit} to zero to suppress all complaints; set it to a large number |
| to prevent complaints from being suppressed. |
| |
| @kindex show complaints |
| @item show complaints |
| Displays how many symbol complaints @value{GDBN} is permitted to produce. |
| |
| @end table |
| |
| @anchor{confirmation requests} |
| By default, @value{GDBN} is cautious, and asks what sometimes seems to be a |
| lot of stupid questions to confirm certain commands. For example, if |
| you try to run a program which is already running: |
| |
| @smallexample |
| (@value{GDBP}) run |
| The program being debugged has been started already. |
| Start it from the beginning? (y or n) |
| @end smallexample |
| |
| If you are willing to unflinchingly face the consequences of your own |
| commands, you can disable this ``feature'': |
| |
| @table @code |
| |
| @kindex set confirm |
| @cindex flinching |
| @cindex confirmation |
| @cindex stupid questions |
| @item set confirm off |
| Disables confirmation requests. Note that running @value{GDBN} with |
| the @option{--batch} option (@pxref{Mode Options, -batch}) also |
| automatically disables confirmation requests. |
| |
| @item set confirm on |
| Enables confirmation requests (the default). |
| |
| @kindex show confirm |
| @item show confirm |
| Displays state of confirmation requests. |
| |
| @end table |
| |
| @cindex command tracing |
| If you need to debug user-defined commands or sourced files you may find it |
| useful to enable @dfn{command tracing}. In this mode each command will be |
| printed as it is executed, prefixed with one or more @samp{+} symbols, the |
| quantity denoting the call depth of each command. |
| |
| @table @code |
| @kindex set trace-commands |
| @cindex command scripts, debugging |
| @item set trace-commands on |
| Enable command tracing. |
| @item set trace-commands off |
| Disable command tracing. |
| @item show trace-commands |
| Display the current state of command tracing. |
| @end table |
| |
| @node Debugging Output |
| @section Optional Messages about Internal Happenings |
| @cindex optional debugging messages |
| |
| @value{GDBN} has commands that enable optional debugging messages from |
| various @value{GDBN} subsystems; normally these commands are of |
| interest to @value{GDBN} maintainers, or when reporting a bug. This |
| section documents those commands. |
| |
| @table @code |
| @kindex set exec-done-display |
| @item set exec-done-display |
| Turns on or off the notification of asynchronous commands' |
| completion. When on, @value{GDBN} will print a message when an |
| asynchronous command finishes its execution. The default is off. |
| @kindex show exec-done-display |
| @item show exec-done-display |
| Displays the current setting of asynchronous command completion |
| notification. |
| @kindex set debug |
| @cindex gdbarch debugging info |
| @cindex architecture debugging info |
| @item set debug arch |
| Turns on or off display of gdbarch debugging info. The default is off |
| @kindex show debug |
| @item show debug arch |
| Displays the current state of displaying gdbarch debugging info. |
| @item set debug aix-thread |
| @cindex AIX threads |
| Display debugging messages about inner workings of the AIX thread |
| module. |
| @item show debug aix-thread |
| Show the current state of AIX thread debugging info display. |
| @item set debug check-physname |
| @cindex physname |
| Check the results of the ``physname'' computation. When reading DWARF |
| debugging information for C@t{++}, @value{GDBN} attempts to compute |
| each entity's name. @value{GDBN} can do this computation in two |
| different ways, depending on exactly what information is present. |
| When enabled, this setting causes @value{GDBN} to compute the names |
| both ways and display any discrepancies. |
| @item show debug check-physname |
| Show the current state of ``physname'' checking. |
| @item set debug dwarf2-die |
| @cindex DWARF2 DIEs |
| Dump DWARF2 DIEs after they are read in. |
| The value is the number of nesting levels to print. |
| A value of zero turns off the display. |
| @item show debug dwarf2-die |
| Show the current state of DWARF2 DIE debugging. |
| @item set debug dwarf2-read |
| @cindex DWARF2 Reading |
| Turns on or off display of debugging messages related to reading |
| DWARF debug info. The default is off. |
| @item show debug dwarf2-read |
| Show the current state of DWARF2 reader debugging. |
| @item set debug displaced |
| @cindex displaced stepping debugging info |
| Turns on or off display of @value{GDBN} debugging info for the |
| displaced stepping support. The default is off. |
| @item show debug displaced |
| Displays the current state of displaying @value{GDBN} debugging info |
| related to displaced stepping. |
| @item set debug event |
| @cindex event debugging info |
| Turns on or off display of @value{GDBN} event debugging info. The |
| default is off. |
| @item show debug event |
| Displays the current state of displaying @value{GDBN} event debugging |
| info. |
| @item set debug expression |
| @cindex expression debugging info |
| Turns on or off display of debugging info about @value{GDBN} |
| expression parsing. The default is off. |
| @item show debug expression |
| Displays the current state of displaying debugging info about |
| @value{GDBN} expression parsing. |
| @item set debug frame |
| @cindex frame debugging info |
| Turns on or off display of @value{GDBN} frame debugging info. The |
| default is off. |
| @item show debug frame |
| Displays the current state of displaying @value{GDBN} frame debugging |
| info. |
| @item set debug gnu-nat |
| @cindex @sc{gnu}/Hurd debug messages |
| Turns on or off debugging messages from the @sc{gnu}/Hurd debug support. |
| @item show debug gnu-nat |
| Show the current state of @sc{gnu}/Hurd debugging messages. |
| @item set debug infrun |
| @cindex inferior debugging info |
| Turns on or off display of @value{GDBN} debugging info for running the inferior. |
| The default is off. @file{infrun.c} contains GDB's runtime state machine used |
| for implementing operations such as single-stepping the inferior. |
| @item show debug infrun |
| Displays the current state of @value{GDBN} inferior debugging. |
| @item set debug jit |
| @cindex just-in-time compilation, debugging messages |
| Turns on or off debugging messages from JIT debug support. |
| @item show debug jit |
| Displays the current state of @value{GDBN} JIT debugging. |
| @item set debug lin-lwp |
| @cindex @sc{gnu}/Linux LWP debug messages |
| @cindex Linux lightweight processes |
| Turns on or off debugging messages from the Linux LWP debug support. |
| @item show debug lin-lwp |
| Show the current state of Linux LWP debugging messages. |
| @item set debug observer |
| @cindex observer debugging info |
| Turns on or off display of @value{GDBN} observer debugging. This |
| includes info such as the notification of observable events. |
| @item show debug observer |
| Displays the current state of observer debugging. |
| @item set debug overload |
| @cindex C@t{++} overload debugging info |
| Turns on or off display of @value{GDBN} C@t{++} overload debugging |
| info. This includes info such as ranking of functions, etc. The default |
| is off. |
| @item show debug overload |
| Displays the current state of displaying @value{GDBN} C@t{++} overload |
| debugging info. |
| @cindex expression parser, debugging info |
| @cindex debug expression parser |
| @item set debug parser |
| Turns on or off the display of expression parser debugging output. |
| Internally, this sets the @code{yydebug} variable in the expression |
| parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for |
| details. The default is off. |
| @item show debug parser |
| Show the current state of expression parser debugging. |
| @cindex packets, reporting on stdout |
| @cindex serial connections, debugging |
| @cindex debug remote protocol |
| @cindex remote protocol debugging |
| @cindex display remote packets |
| @item set debug remote |
| Turns on or off display of reports on all packets sent back and forth across |
| the serial line to the remote machine. The info is printed on the |
| @value{GDBN} standard output stream. The default is off. |
| @item show debug remote |
| Displays the state of display of remote packets. |
| @item set debug serial |
| Turns on or off display of @value{GDBN} serial debugging info. The |
| default is off. |
| @item show debug serial |
| Displays the current state of displaying @value{GDBN} serial debugging |
| info. |
| @item set debug solib-frv |
| @cindex FR-V shared-library debugging |
| Turns on or off debugging messages for FR-V shared-library code. |
| @item show debug solib-frv |
| Display the current state of FR-V shared-library code debugging |
| messages. |
| @item set debug symtab-create |
| @cindex symbol table creation |
| Turns on or off display of debugging messages related to symbol table creation. |
| The default is off. |
| @item show debug symtab-create |
| Show the current state of symbol table creation debugging. |
| @item set debug target |
| @cindex target debugging info |
| Turns on or off display of @value{GDBN} target debugging info. This info |
| includes what is going on at the target level of GDB, as it happens. The |
| default is 0. Set it to 1 to track events, and to 2 to also track the |
| value of large memory transfers. Changes to this flag do not take effect |
| until the next time you connect to a target or use the @code{run} command. |
| @item show debug target |
| Displays the current state of displaying @value{GDBN} target debugging |
| info. |
| @item set debug timestamp |
| @cindex timestampping debugging info |
| Turns on or off display of timestamps with @value{GDBN} debugging info. |
| When enabled, seconds and microseconds are displayed before each debugging |
| message. |
| @item show debug timestamp |
| Displays the current state of displaying timestamps with @value{GDBN} |
| debugging info. |
| @item set debugvarobj |
| @cindex variable object debugging info |
| Turns on or off display of @value{GDBN} variable object debugging |
| info. The default is off. |
| @item show debugvarobj |
| Displays the current state of displaying @value{GDBN} variable object |
| debugging info. |
| @item set debug xml |
| @cindex XML parser debugging |
| Turns on or off debugging messages for built-in XML parsers. |
| @item show debug xml |
| Displays the current state of XML debugging messages. |
| @end table |
| |
| @node Other Misc Settings |
| @section Other Miscellaneous Settings |
| @cindex miscellaneous settings |
| |
| @table @code |
| @kindex set interactive-mode |
| @item set interactive-mode |
| If @code{on}, forces @value{GDBN} to assume that GDB was started |
| in a terminal. In practice, this means that @value{GDBN} should wait |
| for the user to answer queries generated by commands entered at |
| the command prompt. If @code{off}, forces @value{GDBN} to operate |
| in the opposite mode, and it uses the default answers to all queries. |
| If @code{auto} (the default), @value{GDBN} tries to determine whether |
| its standard input is a terminal, and works in interactive-mode if it |
| is, non-interactively otherwise. |
| |
| In the vast majority of cases, the debugger should be able to guess |
| correctly which mode should be used. But this setting can be useful |
| in certain specific cases, such as running a MinGW @value{GDBN} |
| inside a cygwin window. |
| |
| @kindex show interactive-mode |
| @item show interactive-mode |
| Displays whether the debugger is operating in interactive mode or not. |
| @end table |
| |
| @node Extending GDB |
| @chapter Extending @value{GDBN} |
| @cindex extending GDB |
| |
| @value{GDBN} provides three mechanisms for extension. The first is based |
| on composition of @value{GDBN} commands, the second is based on the |
| Python scripting language, and the third is for defining new aliases of |
| existing commands. |
| |
| To facilitate the use of the first two extensions, @value{GDBN} is capable |
| of evaluating the contents of a file. When doing so, @value{GDBN} |
| can recognize which scripting language is being used by looking at |
| the filename extension. Files with an unrecognized filename extension |
| are always treated as a @value{GDBN} Command Files. |
| @xref{Command Files,, Command files}. |
| |
| You can control how @value{GDBN} evaluates these files with the following |
| setting: |
| |
| @table @code |
| @kindex set script-extension |
| @kindex show script-extension |
| @item set script-extension off |
| All scripts are always evaluated as @value{GDBN} Command Files. |
| |
| @item set script-extension soft |
| The debugger determines the scripting language based on filename |
| extension. If this scripting language is supported, @value{GDBN} |
| evaluates the script using that language. Otherwise, it evaluates |
| the file as a @value{GDBN} Command File. |
| |
| @item set script-extension strict |
| The debugger determines the scripting language based on filename |
| extension, and evaluates the script using that language. If the |
| language is not supported, then the evaluation fails. |
| |
| @item show script-extension |
| Display the current value of the @code{script-extension} option. |
| |
| @end table |
| |
| @menu |
| * Sequences:: Canned Sequences of Commands |
| * Python:: Scripting @value{GDBN} using Python |
| * Aliases:: Creating new spellings of existing commands |
| @end menu |
| |
| @node Sequences |
| @section Canned Sequences of Commands |
| |
| Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint |
| Command Lists}), @value{GDBN} provides two ways to store sequences of |
| commands for execution as a unit: user-defined commands and command |
| files. |
| |
| @menu |
| * Define:: How to define your own commands |
| * Hooks:: Hooks for user-defined commands |
| * Command Files:: How to write scripts of commands to be stored in a file |
| * Output:: Commands for controlled output |
| @end menu |
| |
| @node Define |
| @subsection User-defined Commands |
| |
| @cindex user-defined command |
| @cindex arguments, to user-defined commands |
| A @dfn{user-defined command} is a sequence of @value{GDBN} commands to |
| which you assign a new name as a command. This is done with the |
| @code{define} command. User commands may accept up to 10 arguments |
| separated by whitespace. Arguments are accessed within the user command |
| via @code{$arg0@dots{}$arg9}. A trivial example: |
| |
| @smallexample |
| define adder |
| print $arg0 + $arg1 + $arg2 |
| end |
| @end smallexample |
| |
| @noindent |
| To execute the command use: |
| |
| @smallexample |
| adder 1 2 3 |
| @end smallexample |
| |
| @noindent |
| This defines the command @code{adder}, which prints the sum of |
| its three arguments. Note the arguments are text substitutions, so they may |
| reference variables, use complex expressions, or even perform inferior |
| functions calls. |
| |
| @cindex argument count in user-defined commands |
| @cindex how many arguments (user-defined commands) |
| In addition, @code{$argc} may be used to find out how many arguments have |
| been passed. This expands to a number in the range 0@dots{}10. |
| |
| @smallexample |
| define adder |
| if $argc == 2 |
| print $arg0 + $arg1 |
| end |
| if $argc == 3 |
| print $arg0 + $arg1 + $arg2 |
| end |
| end |
| @end smallexample |
| |
| @table @code |
| |
| @kindex define |
| @item define @var{commandname} |
| Define a command named @var{commandname}. If there is already a command |
| by that name, you are asked to confirm that you want to redefine it. |
| @var{commandname} may be a bare command name consisting of letters, |
| numbers, dashes, and underscores. It may also start with any predefined |
| prefix command. For example, @samp{define target my-target} creates |
| a user-defined @samp{target my-target} command. |
| |
| The definition of the command is made up of other @value{GDBN} command lines, |
| which are given following the @code{define} command. The end of these |
| commands is marked by a line containing @code{end}. |
| |
| @kindex document |
| @kindex end@r{ (user-defined commands)} |
| @item document @var{commandname} |
| Document the user-defined command @var{commandname}, so that it can be |
| accessed by @code{help}. The command @var{commandname} must already be |
| defined. This command reads lines of documentation just as @code{define} |
| reads the lines of the command definition, ending with @code{end}. |
| After the @code{document} command is finished, @code{help} on command |
| @var{commandname} displays the documentation you have written. |
| |
| You may use the @code{document} command again to change the |
| documentation of a command. Redefining the command with @code{define} |
| does not change the documentation. |
| |
| @kindex dont-repeat |
| @cindex don't repeat command |
| @item dont-repeat |
| Used inside a user-defined command, this tells @value{GDBN} that this |
| command should not be repeated when the user hits @key{RET} |
| (@pxref{Command Syntax, repeat last command}). |
| |
| @kindex help user-defined |
| @item help user-defined |
| List all user-defined commands and all python commands defined in class |
| COMAND_USER. The first line of the documentation or docstring is |
| included (if any). |
| |
| @kindex show user |
| @item show user |
| @itemx show user @var{commandname} |
| Display the @value{GDBN} commands used to define @var{commandname} (but |
| not its documentation). If no @var{commandname} is given, display the |
| definitions for all user-defined commands. |
| This does not work for user-defined python commands. |
| |
| @cindex infinite recursion in user-defined commands |
| @kindex show max-user-call-depth |
| @kindex set max-user-call-depth |
| @item show max-user-call-depth |
| @itemx set max-user-call-depth |
| The value of @code{max-user-call-depth} controls how many recursion |
| levels are allowed in user-defined commands before @value{GDBN} suspects an |
| infinite recursion and aborts the command. |
| This does not apply to user-defined python commands. |
| @end table |
| |
| In addition to the above commands, user-defined commands frequently |
| use control flow commands, described in @ref{Command Files}. |
| |
| When user-defined commands are executed, the |
| commands of the definition are not printed. An error in any command |
| stops execution of the user-defined command. |
| |
| If used interactively, commands that would ask for confirmation proceed |
| without asking when used inside a user-defined command. Many @value{GDBN} |
| commands that normally print messages to say what they are doing omit the |
| messages when used in a user-defined command. |
| |
| @node Hooks |
| @subsection User-defined Command Hooks |
| @cindex command hooks |
| @cindex hooks, for commands |
| @cindex hooks, pre-command |
| |
| @kindex hook |
| You may define @dfn{hooks}, which are a special kind of user-defined |
| command. Whenever you run the command @samp{foo}, if the user-defined |
| command @samp{hook-foo} exists, it is executed (with no arguments) |
| before that command. |
| |
| @cindex hooks, post-command |
| @kindex hookpost |
| A hook may also be defined which is run after the command you executed. |
| Whenever you run the command @samp{foo}, if the user-defined command |
| @samp{hookpost-foo} exists, it is executed (with no arguments) after |
| that command. Post-execution hooks may exist simultaneously with |
| pre-execution hooks, for the same command. |
| |
| It is valid for a hook to call the command which it hooks. If this |
| occurs, the hook is not re-executed, thereby avoiding infinite recursion. |
| |
| @c It would be nice if hookpost could be passed a parameter indicating |
| @c if the command it hooks executed properly or not. FIXME! |
| |
| @kindex stop@r{, a pseudo-command} |
| In addition, a pseudo-command, @samp{stop} exists. Defining |
| (@samp{hook-stop}) makes the associated commands execute every time |
| execution stops in your program: before breakpoint commands are run, |
| displays are printed, or the stack frame is printed. |
| |
| For example, to ignore @code{SIGALRM} signals while |
| single-stepping, but treat them normally during normal execution, |
| you could define: |
| |
| @smallexample |
| define hook-stop |
| handle SIGALRM nopass |
| end |
| |
| define hook-run |
| handle SIGALRM pass |
| end |
| |
| define hook-continue |
| handle SIGALRM pass |
| end |
| @end smallexample |
| |
| As a further example, to hook at the beginning and end of the @code{echo} |
| command, and to add extra text to the beginning and end of the message, |
| you could define: |
| |
| @smallexample |
| define hook-echo |
| echo <<<--- |
| end |
| |
| define hookpost-echo |
| echo --->>>\n |
| end |
| |
| (@value{GDBP}) echo Hello World |
| <<<---Hello World--->>> |
| (@value{GDBP}) |
| |
| @end smallexample |
| |
| You can define a hook for any single-word command in @value{GDBN}, but |
| not for command aliases; you should define a hook for the basic command |
| name, e.g.@: @code{backtrace} rather than @code{bt}. |
| @c FIXME! So how does Joe User discover whether a command is an alias |
| @c or not? |
| You can hook a multi-word command by adding @code{hook-} or |
| @code{hookpost-} to the last word of the command, e.g.@: |
| @samp{define target hook-remote} to add a hook to @samp{target remote}. |
| |
| If an error occurs during the execution of your hook, execution of |
| @value{GDBN} commands stops and @value{GDBN} issues a prompt |
| (before the command that you actually typed had a chance to run). |
| |
| If you try to define a hook which does not match any known command, you |
| get a warning from the @code{define} command. |
| |
| @node Command Files |
| @subsection Command Files |
| |
| @cindex command files |
| @cindex scripting commands |
| A command file for @value{GDBN} is a text file made of lines that are |
| @value{GDBN} commands. Comments (lines starting with @kbd{#}) may |
| also be included. An empty line in a command file does nothing; it |
| does not mean to repeat the last command, as it would from the |
| terminal. |
| |
| You can request the execution of a command file with the @code{source} |
| command. Note that the @code{source} command is also used to evaluate |
| scripts that are not Command Files. The exact behavior can be configured |
| using the @code{script-extension} setting. |
| @xref{Extending GDB,, Extending GDB}. |
| |
| @table @code |
| @kindex source |
| @cindex execute commands from a file |
| @item source [-s] [-v] @var{filename} |
| Execute the command file @var{filename}. |
| @end table |
| |
| The lines in a command file are generally executed sequentially, |
| unless the order of execution is changed by one of the |
| @emph{flow-control commands} described below. The commands are not |
| printed as they are executed. An error in any command terminates |
| execution of the command file and control is returned to the console. |
| |
| @value{GDBN} first searches for @var{filename} in the current directory. |
| If the file is not found there, and @var{filename} does not specify a |
| directory, then @value{GDBN} also looks for the file on the source search path |
| (specified with the @samp{directory} command); |
| except that @file{$cdir} is not searched because the compilation directory |
| is not relevant to scripts. |
| |
| If @code{-s} is specified, then @value{GDBN} searches for @var{filename} |
| on the search path even if @var{filename} specifies a directory. |
| The search is done by appending @var{filename} to each element of the |
| search path. So, for example, if @var{filename} is @file{mylib/myscript} |
| and the search path contains @file{/home/user} then @value{GDBN} will |
| look for the script @file{/home/user/mylib/myscript}. |
| The search is also done if @var{filename} is an absolute path. |
| For example, if @var{filename} is @file{/tmp/myscript} and |
| the search path contains @file{/home/user} then @value{GDBN} will |
| look for the script @file{/home/user/tmp/myscript}. |
| For DOS-like systems, if @var{filename} contains a drive specification, |
| it is stripped before concatenation. For example, if @var{filename} is |
| @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN} |
| will look for the script @file{c:/tmp/myscript}. |
| |
| If @code{-v}, for verbose mode, is given then @value{GDBN} displays |
| each command as it is executed. The option must be given before |
| @var{filename}, and is interpreted as part of the filename anywhere else. |
| |
| Commands that would ask for confirmation if used interactively proceed |
| without asking when used in a command file. Many @value{GDBN} commands that |
| normally print messages to say what they are doing omit the messages |
| when called from command files. |
| |
| @value{GDBN} also accepts command input from standard input. In this |
| mode, normal output goes to standard output and error output goes to |
| standard error. Errors in a command file supplied on standard input do |
| not terminate execution of the command file---execution continues with |
| the next command. |
| |
| @smallexample |
| gdb < cmds > log 2>&1 |
| @end smallexample |
| |
| (The syntax above will vary depending on the shell used.) This example |
| will execute commands from the file @file{cmds}. All output and errors |
| would be directed to @file{log}. |
| |
| Since commands stored on command files tend to be more general than |
| commands typed interactively, they frequently need to deal with |
| complicated situations, such as different or unexpected values of |
| variables and symbols, changes in how the program being debugged is |
| built, etc. @value{GDBN} provides a set of flow-control commands to |
| deal with these complexities. Using these commands, you can write |
| complex scripts that loop over data structures, execute commands |
| conditionally, etc. |
| |
| @table @code |
| @kindex if |
| @kindex else |
| @item if |
| @itemx else |
| This command allows to include in your script conditionally executed |
| commands. The @code{if} command takes a single argument, which is an |
| expression to evaluate. It is followed by a series of commands that |
| are executed only if the expression is true (its value is nonzero). |
| There can then optionally be an @code{else} line, followed by a series |
| of commands that are only executed if the expression was false. The |
| end of the list is marked by a line containing @code{end}. |
| |
| @kindex while |
| @item while |
| This command allows to write loops. Its syntax is similar to |
| @code{if}: the command takes a single argument, which is an expression |
| to evaluate, and must be followed by the commands to execute, one per |
| line, terminated by an @code{end}. These commands are called the |
| @dfn{body} of the loop. The commands in the body of @code{while} are |
| executed repeatedly as long as the expression evaluates to true. |
| |
| @kindex loop_break |
| @item loop_break |
| This command exits the @code{while} loop in whose body it is included. |
| Execution of the script continues after that @code{while}s @code{end} |
| line. |
| |
| @kindex loop_continue |
| @item loop_continue |
| This command skips the execution of the rest of the body of commands |
| in the @code{while} loop in whose body it is included. Execution |
| branches to the beginning of the @code{while} loop, where it evaluates |
| the controlling expression. |
| |
| @kindex end@r{ (if/else/while commands)} |
| @item end |
| Terminate the block of commands that are the body of @code{if}, |
| @code{else}, or @code{while} flow-control commands. |
| @end table |
| |
| |
| @node Output |
| @subsection Commands for Controlled Output |
| |
| During the execution of a command file or a user-defined command, normal |
| @value{GDBN} output is suppressed; the only output that appears is what is |
| explicitly printed by the commands in the definition. This section |
| describes three commands useful for generating exactly the output you |
| want. |
| |
| @table @code |
| @kindex echo |
| @item echo @var{text} |
| @c I do not consider backslash-space a standard C escape sequence |
| @c because it is not in ANSI. |
| Print @var{text}. Nonprinting characters can be included in |
| @var{text} using C escape sequences, such as @samp{\n} to print a |
| newline. @strong{No newline is printed unless you specify one.} |
| In addition to the standard C escape sequences, a backslash followed |
| by a space stands for a space. This is useful for displaying a |
| string with spaces at the beginning or the end, since leading and |
| trailing spaces are otherwise trimmed from all arguments. |
| To print @samp{@w{ }and foo =@w{ }}, use the command |
| @samp{echo \@w{ }and foo = \@w{ }}. |
| |
| A backslash at the end of @var{text} can be used, as in C, to continue |
| the command onto subsequent lines. For example, |
| |
| @smallexample |
| echo This is some text\n\ |
| which is continued\n\ |
| onto several lines.\n |
| @end smallexample |
| |
| produces the same output as |
| |
| @smallexample |
| echo This is some text\n |
| echo which is continued\n |
| echo onto several lines.\n |
| @end smallexample |
| |
| @kindex output |
| @item output @var{expression} |
| Print the value of @var{expression} and nothing but that value: no |
| newlines, no @samp{$@var{nn} = }. The value is not entered in the |
| value history either. @xref{Expressions, ,Expressions}, for more information |
| on expressions. |
| |
| @item output/@var{fmt} @var{expression} |
| Print the value of @var{expression} in format @var{fmt}. You can use |
| the same formats as for @code{print}. @xref{Output Formats,,Output |
| Formats}, for more information. |
| |
| @kindex printf |
| @item printf @var{template}, @var{expressions}@dots{} |
| Print the values of one or more @var{expressions} under the control of |
| the string @var{template}. To print several values, make |
| @var{expressions} be a comma-separated list of individual expressions, |
| which may be either numbers or pointers. Their values are printed as |
| specified by @var{template}, exactly as a C program would do by |
| executing the code below: |
| |
| @smallexample |
| printf (@var{template}, @var{expressions}@dots{}); |
| @end smallexample |
| |
| As in @code{C} @code{printf}, ordinary characters in @var{template} |
| are printed verbatim, while @dfn{conversion specification} introduced |
| by the @samp{%} character cause subsequent @var{expressions} to be |
| evaluated, their values converted and formatted according to type and |
| style information encoded in the conversion specifications, and then |
| printed. |
| |
| For example, you can print two values in hex like this: |
| |
| @smallexample |
| printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo |
| @end smallexample |
| |
| @code{printf} supports all the standard @code{C} conversion |
| specifications, including the flags and modifiers between the @samp{%} |
| character and the conversion letter, with the following exceptions: |
| |
| @itemize @bullet |
| @item |
| The argument-ordering modifiers, such as @samp{2$}, are not supported. |
| |
| @item |
| The modifier @samp{*} is not supported for specifying precision or |
| width. |
| |
| @item |
| The @samp{'} flag (for separation of digits into groups according to |
| @code{LC_NUMERIC'}) is not supported. |
| |
| @item |
| The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not |
| supported. |
| |
| @item |
| The conversion letter @samp{n} (as in @samp{%n}) is not supported. |
| |
| @item |
| The conversion letters @samp{a} and @samp{A} are not supported. |
| @end itemize |
| |
| @noindent |
| Note that the @samp{ll} type modifier is supported only if the |
| underlying @code{C} implementation used to build @value{GDBN} supports |
| the @code{long long int} type, and the @samp{L} type modifier is |
| supported only if @code{long double} type is available. |
| |
| As in @code{C}, @code{printf} supports simple backslash-escape |
| sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"}, |
| @samp{\a}, and @samp{\f}, that consist of backslash followed by a |
| single character. Octal and hexadecimal escape sequences are not |
| supported. |
| |
| Additionally, @code{printf} supports conversion specifications for DFP |
| (@dfn{Decimal Floating Point}) types using the following length modifiers |
| together with a floating point specifier. |
| letters: |
| |
| @itemize @bullet |
| @item |
| @samp{H} for printing @code{Decimal32} types. |
| |
| @item |
| @samp{D} for printing @code{Decimal64} types. |
| |
| @item |
| @samp{DD} for printing @code{Decimal128} types. |
| @end itemize |
| |
| If the underlying @code{C} implementation used to build @value{GDBN} has |
| support for the three length modifiers for DFP types, other modifiers |
| such as width and precision will also be available for @value{GDBN} to use. |
| |
| In case there is no such @code{C} support, no additional modifiers will be |
| available and the value will be printed in the standard way. |
| |
| Here's an example of printing DFP types using the above conversion letters: |
| @smallexample |
| printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl |
| @end smallexample |
| |
| @kindex eval |
| @item eval @var{template}, @var{expressions}@dots{} |
| Convert the values of one or more @var{expressions} under the control of |
| the string @var{template} to a command line, and call it. |
| |
| @end table |
| |
| @node Python |
| @section Scripting @value{GDBN} using Python |
| @cindex python scripting |
| @cindex scripting with python |
| |
| You can script @value{GDBN} using the @uref{http://www.python.org/, |
| Python programming language}. This feature is available only if |
| @value{GDBN} was configured using @option{--with-python}. |
| |
| @cindex python directory |
| Python scripts used by @value{GDBN} should be installed in |
| @file{@var{data-directory}/python}, where @var{data-directory} is |
| the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). |
| This directory, known as the @dfn{python directory}, |
| is automatically added to the Python Search Path in order to allow |
| the Python interpreter to locate all scripts installed at this location. |
| |
| Additionally, @value{GDBN} commands and convenience functions which |
| are written in Python and are located in the |
| @file{@var{data-directory}/python/gdb/command} or |
| @file{@var{data-directory}/python/gdb/function} directories are |
| automatically imported when @value{GDBN} starts. |
| |
| @menu |
| * Python Commands:: Accessing Python from @value{GDBN}. |
| * Python API:: Accessing @value{GDBN} from Python. |
| * Python Auto-loading:: Automatically loading Python code. |
| * Python modules:: Python modules provided by @value{GDBN}. |
| @end menu |
| |
| @node Python Commands |
| @subsection Python Commands |
| @cindex python commands |
| @cindex commands to access python |
| |
| @value{GDBN} provides one command for accessing the Python interpreter, |
| and one related setting: |
| |
| @table @code |
| @kindex python |
| @item python @r{[}@var{code}@r{]} |
| The @code{python} command can be used to evaluate Python code. |
| |
| If given an argument, the @code{python} command will evaluate the |
| argument as a Python command. For example: |
| |
| @smallexample |
| (@value{GDBP}) python print 23 |
| 23 |
| @end smallexample |
| |
| If you do not provide an argument to @code{python}, it will act as a |
| multi-line command, like @code{define}. In this case, the Python |
| script is made up of subsequent command lines, given after the |
| @code{python} command. This command list is terminated using a line |
| containing @code{end}. For example: |
| |
| @smallexample |
| (@value{GDBP}) python |
| Type python script |
| End with a line saying just "end". |
| >print 23 |
| >end |
| 23 |
| @end smallexample |
| |
| @kindex set python print-stack |
| @item set python print-stack |
| By default, @value{GDBN} will print only the message component of a |
| Python exception when an error occurs in a Python script. This can be |
| controlled using @code{set python print-stack}: if @code{full}, then |
| full Python stack printing is enabled; if @code{none}, then Python stack |
| and message printing is disabled; if @code{message}, the default, only |
| the message component of the error is printed. |
| @end table |
| |
| It is also possible to execute a Python script from the @value{GDBN} |
| interpreter: |
| |
| @table @code |
| @item source @file{script-name} |
| The script name must end with @samp{.py} and @value{GDBN} must be configured |
| to recognize the script language based on filename extension using |
| the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}. |
| |
| @item python execfile ("script-name") |
| This method is based on the @code{execfile} Python built-in function, |
| and thus is always available. |
| @end table |
| |
| @node Python API |
| @subsection Python API |
| @cindex python api |
| @cindex programming in python |
| |
| @cindex python stdout |
| @cindex python pagination |
| At startup, @value{GDBN} overrides Python's @code{sys.stdout} and |
| @code{sys.stderr} to print using @value{GDBN}'s output-paging streams. |
| A Python program which outputs to one of these streams may have its |
| output interrupted by the user (@pxref{Screen Size}). In this |
| situation, a Python @code{KeyboardInterrupt} exception is thrown. |
| |
| @menu |
| * Basic Python:: Basic Python Functions. |
| * Exception Handling:: How Python exceptions are translated. |
| * Values From Inferior:: Python representation of values. |
| * Types In Python:: Python representation of types. |
| * Pretty Printing API:: Pretty-printing values. |
| * Selecting Pretty-Printers:: How GDB chooses a pretty-printer. |
| * Writing a Pretty-Printer:: Writing a Pretty-Printer. |
| * Inferiors In Python:: Python representation of inferiors (processes) |
| * Events In Python:: Listening for events from @value{GDBN}. |
| * Threads In Python:: Accessing inferior threads from Python. |
| * Commands In Python:: Implementing new commands in Python. |
| * Parameters In Python:: Adding new @value{GDBN} parameters. |
| * Functions In Python:: Writing new convenience functions. |
| * Progspaces In Python:: Program spaces. |
| * Objfiles In Python:: Object files. |
| * Frames In Python:: Accessing inferior stack frames from Python. |
| * Blocks In Python:: Accessing frame blocks from Python. |
| * Symbols In Python:: Python representation of symbols. |
| * Symbol Tables In Python:: Python representation of symbol tables. |
| * Breakpoints In Python:: Manipulating breakpoints using Python. |
| * Finish Breakpoints in Python:: Setting Breakpoints on function return |
| using Python. |
| * Lazy Strings In Python:: Python representation of lazy strings. |
| @end menu |
| |
| @node Basic Python |
| @subsubsection Basic Python |
| |
| @cindex python functions |
| @cindex python module |
| @cindex gdb module |
| @value{GDBN} introduces a new Python module, named @code{gdb}. All |
| methods and classes added by @value{GDBN} are placed in this module. |
| @value{GDBN} automatically @code{import}s the @code{gdb} module for |
| use in all scripts evaluated by the @code{python} command. |
| |
| @findex gdb.PYTHONDIR |
| @defvar gdb.PYTHONDIR |
| A string containing the python directory (@pxref{Python}). |
| @end defvar |
| |
| @findex gdb.execute |
| @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]}) |
| Evaluate @var{command}, a string, as a @value{GDBN} CLI command. |
| If a GDB exception happens while @var{command} runs, it is |
| translated as described in @ref{Exception Handling,,Exception Handling}. |
| |
| @var{from_tty} specifies whether @value{GDBN} ought to consider this |
| command as having originated from the user invoking it interactively. |
| It must be a boolean value. If omitted, it defaults to @code{False}. |
| |
| By default, any output produced by @var{command} is sent to |
| @value{GDBN}'s standard output. If the @var{to_string} parameter is |
| @code{True}, then output will be collected by @code{gdb.execute} and |
| returned as a string. The default is @code{False}, in which case the |
| return value is @code{None}. If @var{to_string} is @code{True}, the |
| @value{GDBN} virtual terminal will be temporarily set to unlimited width |
| and height, and its pagination will be disabled; @pxref{Screen Size}. |
| @end defun |
| |
| @findex gdb.breakpoints |
| @defun gdb.breakpoints () |
| Return a sequence holding all of @value{GDBN}'s breakpoints. |
| @xref{Breakpoints In Python}, for more information. |
| @end defun |
| |
| @findex gdb.parameter |
| @defun gdb.parameter (parameter) |
| Return the value of a @value{GDBN} parameter. @var{parameter} is a |
| string naming the parameter to look up; @var{parameter} may contain |
| spaces if the parameter has a multi-part name. For example, |
| @samp{print object} is a valid parameter name. |
| |
| If the named parameter does not exist, this function throws a |
| @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the |
| parameter's value is converted to a Python value of the appropriate |
| type, and returned. |
| @end defun |
| |
| @findex gdb.history |
| @defun gdb.history (number) |
| Return a value from @value{GDBN}'s value history (@pxref{Value |
| History}). @var{number} indicates which history element to return. |
| If @var{number} is negative, then @value{GDBN} will take its absolute value |
| and count backward from the last element (i.e., the most recent element) to |
| find the value to return. If @var{number} is zero, then @value{GDBN} will |
| return the most recent element. If the element specified by @var{number} |
| doesn't exist in the value history, a @code{gdb.error} exception will be |
| raised. |
| |
| If no exception is raised, the return value is always an instance of |
| @code{gdb.Value} (@pxref{Values From Inferior}). |
| @end defun |
| |
| @findex gdb.parse_and_eval |
| @defun gdb.parse_and_eval (expression) |
| Parse @var{expression} as an expression in the current language, |
| evaluate it, and return the result as a @code{gdb.Value}. |
| @var{expression} must be a string. |
| |
| This function can be useful when implementing a new command |
| (@pxref{Commands In Python}), as it provides a way to parse the |
| command's argument as an expression. It is also useful simply to |
| compute values, for example, it is the only way to get the value of a |
| convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}. |
| @end defun |
| |
| @findex gdb.find_pc_line |
| @defun gdb.find_pc_line (pc) |
| Return the @code{gdb.Symtab_and_line} object corresponding to the |
| @var{pc} value. @xref{Symbol Tables In Python}. If an invalid |
| value of @var{pc} is passed as an argument, then the @code{symtab} and |
| @code{line} attributes of the returned @code{gdb.Symtab_and_line} object |
| will be @code{None} and 0 respectively. |
| @end defun |
| |
| @findex gdb.post_event |
| @defun gdb.post_event (event) |
| Put @var{event}, a callable object taking no arguments, into |
| @value{GDBN}'s internal event queue. This callable will be invoked at |
| some later point, during @value{GDBN}'s event processing. Events |
| posted using @code{post_event} will be run in the order in which they |
| were posted; however, there is no way to know when they will be |
| processed relative to other events inside @value{GDBN}. |
| |
| @value{GDBN} is not thread-safe. If your Python program uses multiple |
| threads, you must be careful to only call @value{GDBN}-specific |
| functions in the main @value{GDBN} thread. @code{post_event} ensures |
| this. For example: |
| |
| @smallexample |
| (@value{GDBP}) python |
| >import threading |
| > |
| >class Writer(): |
| > def __init__(self, message): |
| > self.message = message; |
| > def __call__(self): |
| > gdb.write(self.message) |
| > |
| >class MyThread1 (threading.Thread): |
| > def run (self): |
| > gdb.post_event(Writer("Hello ")) |
| > |
| >class MyThread2 (threading.Thread): |
| > def run (self): |
| > gdb.post_event(Writer("World\n")) |
| > |
| >MyThread1().start() |
| >MyThread2().start() |
| >end |
| (@value{GDBP}) Hello World |
| @end smallexample |
| @end defun |
| |
| @findex gdb.write |
| @defun gdb.write (string @r{[}, stream{]}) |
| Print a string to @value{GDBN}'s paginated output stream. The |
| optional @var{stream} determines the stream to print to. The default |
| stream is @value{GDBN}'s standard output stream. Possible stream |
| values are: |
| |
| @table @code |
| @findex STDOUT |
| @findex gdb.STDOUT |
| @item gdb.STDOUT |
| @value{GDBN}'s standard output stream. |
| |
| @findex STDERR |
| @findex gdb.STDERR |
| @item gdb.STDERR |
| @value{GDBN}'s standard error stream. |
| |
| @findex STDLOG |
| @findex gdb.STDLOG |
| @item gdb.STDLOG |
| @value{GDBN}'s log stream (@pxref{Logging Output}). |
| @end table |
| |
| Writing to @code{sys.stdout} or @code{sys.stderr} will automatically |
| call this function and will automatically direct the output to the |
| relevant stream. |
| @end defun |
| |
| @findex gdb.flush |
| @defun gdb.flush () |
| Flush the buffer of a @value{GDBN} paginated stream so that the |
| contents are displayed immediately. @value{GDBN} will flush the |
| contents of a stream automatically when it encounters a newline in the |
| buffer. The optional @var{stream} determines the stream to flush. The |
| default stream is @value{GDBN}'s standard output stream. Possible |
| stream values are: |
| |
| @table @code |
| @findex STDOUT |
| @findex gdb.STDOUT |
| @item gdb.STDOUT |
| @value{GDBN}'s standard output stream. |
| |
| @findex STDERR |
| @findex gdb.STDERR |
| @item gdb.STDERR |
| @value{GDBN}'s standard error stream. |
| |
| @findex STDLOG |
| @findex gdb.STDLOG |
| @item gdb.STDLOG |
| @value{GDBN}'s log stream (@pxref{Logging Output}). |
| |
| @end table |
| |
| Flushing @code{sys.stdout} or @code{sys.stderr} will automatically |
| call this function for the relevant stream. |
| @end defun |
| |
| @findex gdb.target_charset |
| @defun gdb.target_charset () |
| Return the name of the current target character set (@pxref{Character |
| Sets}). This differs from @code{gdb.parameter('target-charset')} in |
| that @samp{auto} is never returned. |
| @end defun |
| |
| @findex gdb.target_wide_charset |
| @defun gdb.target_wide_charset () |
| Return the name of the current target wide character set |
| (@pxref{Character Sets}). This differs from |
| @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is |
| never returned. |
| @end defun |
| |
| @findex gdb.solib_name |
| @defun gdb.solib_name (address) |
| Return the name of the shared library holding the given @var{address} |
| as a string, or @code{None}. |
| @end defun |
| |
| @findex gdb.decode_line |
| @defun gdb.decode_line @r{[}expression@r{]} |
| Return locations of the line specified by @var{expression}, or of the |
| current line if no argument was given. This function returns a Python |
| tuple containing two elements. The first element contains a string |
| holding any unparsed section of @var{expression} (or @code{None} if |
| the expression has been fully parsed). The second element contains |
| either @code{None} or another tuple that contains all the locations |
| that match the expression represented as @code{gdb.Symtab_and_line} |
| objects (@pxref{Symbol Tables In Python}). If @var{expression} is |
| provided, it is decoded the way that @value{GDBN}'s inbuilt |
| @code{break} or @code{edit} commands do (@pxref{Specify Location}). |
| @end defun |
| |
| @defun gdb.prompt_hook (current_prompt) |
| @anchor{prompt_hook} |
| |
| If @var{prompt_hook} is callable, @value{GDBN} will call the method |
| assigned to this operation before a prompt is displayed by |
| @value{GDBN}. |
| |
| The parameter @code{current_prompt} contains the current @value{GDBN} |
| prompt. This method must return a Python string, or @code{None}. If |
| a string is returned, the @value{GDBN} prompt will be set to that |
| string. If @code{None} is returned, @value{GDBN} will continue to use |
| the current prompt. |
| |
| Some prompts cannot be substituted in @value{GDBN}. Secondary prompts |
| such as those used by readline for command input, and annotation |
| related prompts are prohibited from being changed. |
| @end defun |
| |
| @node Exception Handling |
| @subsubsection Exception Handling |
| @cindex python exceptions |
| @cindex exceptions, python |
| |
| When executing the @code{python} command, Python exceptions |
| uncaught within the Python code are translated to calls to |
| @value{GDBN} error-reporting mechanism. If the command that called |
| @code{python} does not handle the error, @value{GDBN} will |
| terminate it and print an error message containing the Python |
| exception name, the associated value, and the Python call stack |
| backtrace at the point where the exception was raised. Example: |
| |
| @smallexample |
| (@value{GDBP}) python print foo |
| Traceback (most recent call last): |
| File "<string>", line 1, in <module> |
| NameError: name 'foo' is not defined |
| @end smallexample |
| |
| @value{GDBN} errors that happen in @value{GDBN} commands invoked by |
| Python code are converted to Python exceptions. The type of the |
| Python exception depends on the error. |
| |
| @ftable @code |
| @item gdb.error |
| This is the base class for most exceptions generated by @value{GDBN}. |
| It is derived from @code{RuntimeError}, for compatibility with earlier |
| versions of @value{GDBN}. |
| |
| If an error occurring in @value{GDBN} does not fit into some more |
| specific category, then the generated exception will have this type. |
| |
| @item gdb.MemoryError |
| This is a subclass of @code{gdb.error} which is thrown when an |
| operation tried to access invalid memory in the inferior. |
| |
| @item KeyboardInterrupt |
| User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination |
| prompt) is translated to a Python @code{KeyboardInterrupt} exception. |
| @end ftable |
| |
| In all cases, your exception handler will see the @value{GDBN} error |
| message as its value and the Python call stack backtrace at the Python |
| statement closest to where the @value{GDBN} error occured as the |
| traceback. |
| |
| @findex gdb.GdbError |
| When implementing @value{GDBN} commands in Python via @code{gdb.Command}, |
| it is useful to be able to throw an exception that doesn't cause a |
| traceback to be printed. For example, the user may have invoked the |
| command incorrectly. Use the @code{gdb.GdbError} exception |
| to handle this case. Example: |
| |
| @smallexample |
| (gdb) python |
| >class HelloWorld (gdb.Command): |
| > """Greet the whole world.""" |
| > def __init__ (self): |
| > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) |
| > def invoke (self, args, from_tty): |
| > argv = gdb.string_to_argv (args) |
| > if len (argv) != 0: |
| > raise gdb.GdbError ("hello-world takes no arguments") |
| > print "Hello, World!" |
| >HelloWorld () |
| >end |
| (gdb) hello-world 42 |
| hello-world takes no arguments |
| @end smallexample |
| |
| @node Values From Inferior |
| @subsubsection Values From Inferior |
| @cindex values from inferior, with Python |
| @cindex python, working with values from inferior |
| |
| @cindex @code{gdb.Value} |
| @value{GDBN} provides values it obtains from the inferior program in |
| an object of type @code{gdb.Value}. @value{GDBN} uses this object |
| for its internal bookkeeping of the inferior's values, and for |
| fetching values when necessary. |
| |
| Inferior values that are simple scalars can be used directly in |
| Python expressions that are valid for the value's data type. Here's |
| an example for an integer or floating-point value @code{some_val}: |
| |
| @smallexample |
| bar = some_val + 2 |
| @end smallexample |
| |
| @noindent |
| As result of this, @code{bar} will also be a @code{gdb.Value} object |
| whose values are of the same type as those of @code{some_val}. |
| |
| Inferior values that are structures or instances of some class can |
| be accessed using the Python @dfn{dictionary syntax}. For example, if |
| @code{some_val} is a @code{gdb.Value} instance holding a structure, you |
| can access its @code{foo} element with: |
| |
| @smallexample |
| bar = some_val['foo'] |
| @end smallexample |
| |
| Again, @code{bar} will also be a @code{gdb.Value} object. |
| |
| A @code{gdb.Value} that represents a function can be executed via |
| inferior function call. Any arguments provided to the call must match |
| the function's prototype, and must be provided in the order specified |
| by that prototype. |
| |
| For example, @code{some_val} is a @code{gdb.Value} instance |
| representing a function that takes two integers as arguments. To |
| execute this function, call it like so: |
| |
| @smallexample |
| result = some_val (10,20) |
| @end smallexample |
| |
| Any values returned from a function call will be stored as a |
| @code{gdb.Value}. |
| |
| The following attributes are provided: |
| |
| @table @code |
| @defvar Value.address |
| If this object is addressable, this read-only attribute holds a |
| @code{gdb.Value} object representing the address. Otherwise, |
| this attribute holds @code{None}. |
| @end defvar |
| |
| @cindex optimized out value in Python |
| @defvar Value.is_optimized_out |
| This read-only boolean attribute is true if the compiler optimized out |
| this value, thus it is not available for fetching from the inferior. |
| @end defvar |
| |
| @defvar Value.type |
| The type of this @code{gdb.Value}. The value of this attribute is a |
| @code{gdb.Type} object (@pxref{Types In Python}). |
| @end defvar |
| |
| @defvar Value.dynamic_type |
| The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time |
| type information (@acronym{RTTI}) to determine the dynamic type of the |
| value. If this value is of class type, it will return the class in |
| which the value is embedded, if any. If this value is of pointer or |
| reference to a class type, it will compute the dynamic type of the |
| referenced object, and return a pointer or reference to that type, |
| respectively. In all other cases, it will return the value's static |
| type. |
| |
| Note that this feature will only work when debugging a C@t{++} program |
| that includes @acronym{RTTI} for the object in question. Otherwise, |
| it will just return the static type of the value as in @kbd{ptype foo} |
| (@pxref{Symbols, ptype}). |
| @end defvar |
| |
| @defvar Value.is_lazy |
| The value of this read-only boolean attribute is @code{True} if this |
| @code{gdb.Value} has not yet been fetched from the inferior. |
| @value{GDBN} does not fetch values until necessary, for efficiency. |
| For example: |
| |
| @smallexample |
| myval = gdb.parse_and_eval ('somevar') |
| @end smallexample |
| |
| The value of @code{somevar} is not fetched at this time. It will be |
| fetched when the value is needed, or when the @code{fetch_lazy} |
| method is invoked. |
| @end defvar |
| @end table |
| |
| The following methods are provided: |
| |
| @table @code |
| @defun Value.__init__ (@var{val}) |
| Many Python values can be converted directly to a @code{gdb.Value} via |
| this object initializer. Specifically: |
| |
| @table @asis |
| @item Python boolean |
| A Python boolean is converted to the boolean type from the current |
| language. |
| |
| @item Python integer |
| A Python integer is converted to the C @code{long} type for the |
| current architecture. |
| |
| @item Python long |
| A Python long is converted to the C @code{long long} type for the |
| current architecture. |
| |
| @item Python float |
| A Python float is converted to the C @code{double} type for the |
| current architecture. |
| |
| @item Python string |
| A Python string is converted to a target string, using the current |
| target encoding. |
| |
| @item @code{gdb.Value} |
| If @code{val} is a @code{gdb.Value}, then a copy of the value is made. |
| |
| @item @code{gdb.LazyString} |
| If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In |
| Python}), then the lazy string's @code{value} method is called, and |
| its result is used. |
| @end table |
| @end defun |
| |
| @defun Value.cast (type) |
| Return a new instance of @code{gdb.Value} that is the result of |
| casting this instance to the type described by @var{type}, which must |
| be a @code{gdb.Type} object. If the cast cannot be performed for some |
| reason, this method throws an exception. |
| @end defun |
| |
| @defun Value.dereference () |
| For pointer data types, this method returns a new @code{gdb.Value} object |
| whose contents is the object pointed to by the pointer. For example, if |
| @code{foo} is a C pointer to an @code{int}, declared in your C program as |
| |
| @smallexample |
| int *foo; |
| @end smallexample |
| |
| @noindent |
| then you can use the corresponding @code{gdb.Value} to access what |
| @code{foo} points to like this: |
| |
| @smallexample |
| bar = foo.dereference () |
| @end smallexample |
| |
| The result @code{bar} will be a @code{gdb.Value} object holding the |
| value pointed to by @code{foo}. |
| |
| A similar function @code{Value.referenced_value} exists which also |
| returns @code{gdb.Value} objects corresonding to the values pointed to |
| by pointer values (and additionally, values referenced by reference |
| values). However, the behavior of @code{Value.dereference} |
| differs from @code{Value.referenced_value} by the fact that the |
| behavior of @code{Value.dereference} is identical to applying the C |
| unary operator @code{*} on a given value. For example, consider a |
| reference to a pointer @code{ptrref}, declared in your C@t{++} program |
| as |
| |
| @smallexample |
| typedef int *intptr; |
| ... |
| int val = 10; |
| intptr ptr = &val; |
| intptr &ptrref = ptr; |
| @end smallexample |
| |
| Though @code{ptrref} is a reference value, one can apply the method |
| @code{Value.dereference} to the @code{gdb.Value} object corresponding |
| to it and obtain a @code{gdb.Value} which is identical to that |
| corresponding to @code{val}. However, if you apply the method |
| @code{Value.referenced_value}, the result would be a @code{gdb.Value} |
| object identical to that corresponding to @code{ptr}. |
| |
| @smallexample |
| py_ptrref = gdb.parse_and_eval ("ptrref") |
| py_val = py_ptrref.dereference () |
| py_ptr = py_ptrref.referenced_value () |
| @end smallexample |
| |
| The @code{gdb.Value} object @code{py_val} is identical to that |
| corresponding to @code{val}, and @code{py_ptr} is identical to that |
| corresponding to @code{ptr}. In general, @code{Value.dereference} can |
| be applied whenever the C unary operator @code{*} can be applied |
| to the corresponding C value. For those cases where applying both |
| @code{Value.dereference} and @code{Value.referenced_value} is allowed, |
| the results obtained need not be identical (as we have seen in the above |
| example). The results are however identical when applied on |
| @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value} |
| objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program. |
| @end defun |
| |
| @defun Value.referenced_value () |
| For pointer or reference data types, this method returns a new |
| @code{gdb.Value} object corresponding to the value referenced by the |
| pointer/reference value. For pointer data types, |
| @code{Value.dereference} and @code{Value.referenced_value} produce |
| identical results. The difference between these methods is that |
| @code{Value.dereference} cannot get the values referenced by reference |
| values. For example, consider a reference to an @code{int}, declared |
| in your C@t{++} program as |
| |
| @smallexample |
| int val = 10; |
| int &ref = val; |
| @end smallexample |
| |
| @noindent |
| then applying @code{Value.dereference} to the @code{gdb.Value} object |
| corresponding to @code{ref} will result in an error, while applying |
| @code{Value.referenced_value} will result in a @code{gdb.Value} object |
| identical to that corresponding to @code{val}. |
| |
| @smallexample |
| py_ref = gdb.parse_and_eval ("ref") |
| er_ref = py_ref.dereference () # Results in error |
| py_val = py_ref.referenced_value () # Returns the referenced value |
| @end smallexample |
| |
| The @code{gdb.Value} object @code{py_val} is identical to that |
| corresponding to @code{val}. |
| @end defun |
| |
| @defun Value.dynamic_cast (type) |
| Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast} |
| operator were used. Consult a C@t{++} reference for details. |
| @end defun |
| |
| @defun Value.reinterpret_cast (type) |
| Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast} |
| operator were used. Consult a C@t{++} reference for details. |
| @end defun |
| |
| @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]}) |
| If this @code{gdb.Value} represents a string, then this method |
| converts the contents to a Python string. Otherwise, this method will |
| throw an exception. |
| |
| Strings are recognized in a language-specific way; whether a given |
| @code{gdb.Value} represents a string is determined by the current |
| language. |
| |
| For C-like languages, a value is a string if it is a pointer to or an |
| array of characters or ints. The string is assumed to be terminated |
| by a zero of the appropriate width. However if the optional length |
| argument is given, the string will be converted to that given length, |
| ignoring any embedded zeros that the string may contain. |
| |
| If the optional @var{encoding} argument is given, it must be a string |
| naming the encoding of the string in the @code{gdb.Value}, such as |
| @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts |
| the same encodings as the corresponding argument to Python's |
| @code{string.decode} method, and the Python codec machinery will be used |
| to convert the string. If @var{encoding} is not given, or if |
| @var{encoding} is the empty string, then either the @code{target-charset} |
| (@pxref{Character Sets}) will be used, or a language-specific encoding |
| will be used, if the current language is able to supply one. |
| |
| The optional @var{errors} argument is the same as the corresponding |
| argument to Python's @code{string.decode} method. |
| |
| If the optional @var{length} argument is given, the string will be |
| fetched and converted to the given length. |
| @end defun |
| |
| @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]}) |
| If this @code{gdb.Value} represents a string, then this method |
| converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings |
| In Python}). Otherwise, this method will throw an exception. |
| |
| If the optional @var{encoding} argument is given, it must be a string |
| naming the encoding of the @code{gdb.LazyString}. Some examples are: |
| @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the |
| @var{encoding} argument is an encoding that @value{GDBN} does |
| recognize, @value{GDBN} will raise an error. |
| |
| When a lazy string is printed, the @value{GDBN} encoding machinery is |
| used to convert the string during printing. If the optional |
| @var{encoding} argument is not provided, or is an empty string, |
| @value{GDBN} will automatically select the encoding most suitable for |
| the string type. For further information on encoding in @value{GDBN} |
| please see @ref{Character Sets}. |
| |
| If the optional @var{length} argument is given, the string will be |
| fetched and encoded to the length of characters specified. If |
| the @var{length} argument is not provided, the string will be fetched |
| and encoded until a null of appropriate width is found. |
| @end defun |
| |
| @defun Value.fetch_lazy () |
| If the @code{gdb.Value} object is currently a lazy value |
| (@code{gdb.Value.is_lazy} is @code{True}), then the value is |
| fetched from the inferior. Any errors that occur in the process |
| will produce a Python exception. |
| |
| If the @code{gdb.Value} object is not a lazy value, this method |
| has no effect. |
| |
| This method does not return a value. |
| @end defun |
| |
| @end table |
| |
| @node Types In Python |
| @subsubsection Types In Python |
| @cindex types in Python |
| @cindex Python, working with types |
| |
| @tindex gdb.Type |
| @value{GDBN} represents types from the inferior using the class |
| @code{gdb.Type}. |
| |
| The following type-related functions are available in the @code{gdb} |
| module: |
| |
| @findex gdb.lookup_type |
| @defun gdb.lookup_type (name @r{[}, block@r{]}) |
| This function looks up a type by name. @var{name} is the name of the |
| type to look up. It must be a string. |
| |
| If @var{block} is given, then @var{name} is looked up in that scope. |
| Otherwise, it is searched for globally. |
| |
| Ordinarily, this function will return an instance of @code{gdb.Type}. |
| If the named type cannot be found, it will throw an exception. |
| @end defun |
| |
| If the type is a structure or class type, or an enum type, the fields |
| of that type can be accessed using the Python @dfn{dictionary syntax}. |
| For example, if @code{some_type} is a @code{gdb.Type} instance holding |
| a structure type, you can access its @code{foo} field with: |
| |
| @smallexample |
| bar = some_type['foo'] |
| @end smallexample |
| |
| @code{bar} will be a @code{gdb.Field} object; see below under the |
| description of the @code{Type.fields} method for a description of the |
| @code{gdb.Field} class. |
| |
| An instance of @code{Type} has the following attributes: |
| |
| @table @code |
| @defvar Type.code |
| The type code for this type. The type code will be one of the |
| @code{TYPE_CODE_} constants defined below. |
| @end defvar |
| |
| @defvar Type.sizeof |
| The size of this type, in target @code{char} units. Usually, a |
| target's @code{char} type will be an 8-bit byte. However, on some |
| unusual platforms, this type may have a different size. |
| @end defvar |
| |
| @defvar Type.tag |
| The tag name for this type. The tag name is the name after |
| @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all |
| languages have this concept. If this type has no tag name, then |
| @code{None} is returned. |
| @end defvar |
| @end table |
| |
| The following methods are provided: |
| |
| @table @code |
| @defun Type.fields () |
| For structure and union types, this method returns the fields. Range |
| types have two fields, the minimum and maximum values. Enum types |
| have one field per enum constant. Function and method types have one |
| field per parameter. The base types of C@t{++} classes are also |
| represented as fields. If the type has no fields, or does not fit |
| into one of these categories, an empty sequence will be returned. |
| |
| Each field is a @code{gdb.Field} object, with some pre-defined attributes: |
| @table @code |
| @item bitpos |
| This attribute is not available for @code{static} fields (as in |
| C@t{++} or Java). For non-@code{static} fields, the value is the bit |
| position of the field. For @code{enum} fields, the value is the |
| enumeration member's integer representation. |
| |
| @item name |
| The name of the field, or @code{None} for anonymous fields. |
| |
| @item artificial |
| This is @code{True} if the field is artificial, usually meaning that |
| it was provided by the compiler and not the user. This attribute is |
| always provided, and is @code{False} if the field is not artificial. |
| |
| @item is_base_class |
| This is @code{True} if the field represents a base class of a C@t{++} |
| structure. This attribute is always provided, and is @code{False} |
| if the field is not a base class of the type that is the argument of |
| @code{fields}, or if that type was not a C@t{++} class. |
| |
| @item bitsize |
| If the field is packed, or is a bitfield, then this will have a |
| non-zero value, which is the size of the field in bits. Otherwise, |
| this will be zero; in this case the field's size is given by its type. |
| |
| @item type |
| The type of the field. This is usually an instance of @code{Type}, |
| but it can be @code{None} in some situations. |
| @end table |
| @end defun |
| |
| @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]}) |
| Return a new @code{gdb.Type} object which represents an array of this |
| type. If one argument is given, it is the inclusive upper bound of |
| the array; in this case the lower bound is zero. If two arguments are |
| given, the first argument is the lower bound of the array, and the |
| second argument is the upper bound of the array. An array's length |
| must not be negative, but the bounds can be. |
| @end defun |
| |
| @defun Type.const () |
| Return a new @code{gdb.Type} object which represents a |
| @code{const}-qualified variant of this type. |
| @end defun |
| |
| @defun Type.volatile () |
| Return a new @code{gdb.Type} object which represents a |
| @code{volatile}-qualified variant of this type. |
| @end defun |
| |
| @defun Type.unqualified () |
| Return a new @code{gdb.Type} object which represents an unqualified |
| variant of this type. That is, the result is neither @code{const} nor |
| @code{volatile}. |
| @end defun |
| |
| @defun Type.range () |
| Return a Python @code{Tuple} object that contains two elements: the |
| low bound of the argument type and the high bound of that type. If |
| the type does not have a range, @value{GDBN} will raise a |
| @code{gdb.error} exception (@pxref{Exception Handling}). |
| @end defun |
| |
| @defun Type.reference () |
| Return a new @code{gdb.Type} object which represents a reference to this |
| type. |
| @end defun |
| |
| @defun Type.pointer () |
| Return a new @code{gdb.Type} object which represents a pointer to this |
| type. |
| @end defun |
| |
| @defun Type.strip_typedefs () |
| Return a new @code{gdb.Type} that represents the real type, |
| after removing all layers of typedefs. |
| @end defun |
| |
| @defun Type.target () |
| Return a new @code{gdb.Type} object which represents the target type |
| of this type. |
| |
| For a pointer type, the target type is the type of the pointed-to |
| object. For an array type (meaning C-like arrays), the target type is |
| the type of the elements of the array. For a function or method type, |
| the target type is the type of the return value. For a complex type, |
| the target type is the type of the elements. For a typedef, the |
| target type is the aliased type. |
| |
| If the type does not have a target, this method will throw an |
| exception. |
| @end defun |
| |
| @defun Type.template_argument (n @r{[}, block@r{]}) |
| If this @code{gdb.Type} is an instantiation of a template, this will |
| return a new @code{gdb.Type} which represents the type of the |
| @var{n}th template argument. |
| |
| If this @code{gdb.Type} is not a template type, this will throw an |
| exception. Ordinarily, only C@t{++} code will have template types. |
| |
| If @var{block} is given, then @var{name} is looked up in that scope. |
| Otherwise, it is searched for globally. |
| @end defun |
| @end table |
| |
| |
| Each type has a code, which indicates what category this type falls |
| into. The available type categories are represented by constants |
| defined in the @code{gdb} module: |
| |
| @table @code |
| @findex TYPE_CODE_PTR |
| @findex gdb.TYPE_CODE_PTR |
| @item gdb.TYPE_CODE_PTR |
| The type is a pointer. |
| |
| @findex TYPE_CODE_ARRAY |
| @findex gdb.TYPE_CODE_ARRAY |
| @item gdb.TYPE_CODE_ARRAY |
| The type is an array. |
| |
| @findex TYPE_CODE_STRUCT |
| @findex gdb.TYPE_CODE_STRUCT |
| @item gdb.TYPE_CODE_STRUCT |
| The type is a structure. |
| |
| @findex TYPE_CODE_UNION |
| @findex gdb.TYPE_CODE_UNION |
| @item gdb.TYPE_CODE_UNION |
| The type is a union. |
| |
| @findex TYPE_CODE_ENUM |
| @findex gdb.TYPE_CODE_ENUM |
| @item gdb.TYPE_CODE_ENUM |
| The type is an enum. |
| |
| @findex TYPE_CODE_FLAGS |
| @findex gdb.TYPE_CODE_FLAGS |
| @item gdb.TYPE_CODE_FLAGS |
| A bit flags type, used for things such as status registers. |
| |
| @findex TYPE_CODE_FUNC |
| @findex gdb.TYPE_CODE_FUNC |
| @item gdb.TYPE_CODE_FUNC |
| The type is a function. |
| |
| @findex TYPE_CODE_INT |
| @findex gdb.TYPE_CODE_INT |
| @item gdb.TYPE_CODE_INT |
| The type is an integer type. |
| |
| @findex TYPE_CODE_FLT |
| @findex gdb.TYPE_CODE_FLT |
| @item gdb.TYPE_CODE_FLT |
| A floating point type. |
| |
| @findex TYPE_CODE_VOID |
| @findex gdb.TYPE_CODE_VOID |
| @item gdb.TYPE_CODE_VOID |
| The special type @code{void}. |
| |
| @findex TYPE_CODE_SET |
| @findex gdb.TYPE_CODE_SET |
| @item gdb.TYPE_CODE_SET |
| A Pascal set type. |
| |
| @findex TYPE_CODE_RANGE |
| @findex gdb.TYPE_CODE_RANGE |
| @item gdb.TYPE_CODE_RANGE |
| A range type, that is, an integer type with bounds. |
| |
| @findex TYPE_CODE_STRING |
| @findex gdb.TYPE_CODE_STRING |
| @item gdb.TYPE_CODE_STRING |
| A string type. Note that this is only used for certain languages with |
| language-defined string types; C strings are not represented this way. |
| |
| @findex TYPE_CODE_BITSTRING |
| @findex gdb.TYPE_CODE_BITSTRING |
| @item gdb.TYPE_CODE_BITSTRING |
| A string of bits. |
| |
| @findex TYPE_CODE_ERROR |
| @findex gdb.TYPE_CODE_ERROR |
| @item gdb.TYPE_CODE_ERROR |
| An unknown or erroneous type. |
| |
| @findex TYPE_CODE_METHOD |
| @findex gdb.TYPE_CODE_METHOD |
| @item gdb.TYPE_CODE_METHOD |
| A method type, as found in C@t{++} or Java. |
| |
| @findex TYPE_CODE_METHODPTR |
| @findex gdb.TYPE_CODE_METHODPTR |
| @item gdb.TYPE_CODE_METHODPTR |
| A pointer-to-member-function. |
| |
| @findex TYPE_CODE_MEMBERPTR |
| @findex gdb.TYPE_CODE_MEMBERPTR |
| @item gdb.TYPE_CODE_MEMBERPTR |
| A pointer-to-member. |
| |
| @findex TYPE_CODE_REF |
| @findex gdb.TYPE_CODE_REF |
| @item gdb.TYPE_CODE_REF |
| A reference type. |
| |
| @findex TYPE_CODE_CHAR |
| @findex gdb.TYPE_CODE_CHAR |
| @item gdb.TYPE_CODE_CHAR |
| A character type. |
| |
| @findex TYPE_CODE_BOOL |
| @findex gdb.TYPE_CODE_BOOL |
| @item gdb.TYPE_CODE_BOOL |
| A boolean type. |
| |
| @findex TYPE_CODE_COMPLEX |
| @findex gdb.TYPE_CODE_COMPLEX |
| @item gdb.TYPE_CODE_COMPLEX |
| A complex float type. |
| |
| @findex TYPE_CODE_TYPEDEF |
| @findex gdb.TYPE_CODE_TYPEDEF |
| @item gdb.TYPE_CODE_TYPEDEF |
| A typedef to some other type. |
| |
| @findex TYPE_CODE_NAMESPACE |
| @findex gdb.TYPE_CODE_NAMESPACE |
| @item gdb.TYPE_CODE_NAMESPACE |
| A C@t{++} namespace. |
| |
| @findex TYPE_CODE_DECFLOAT |
| @findex gdb.TYPE_CODE_DECFLOAT |
| @item gdb.TYPE_CODE_DECFLOAT |
| A decimal floating point type. |
| |
| @findex TYPE_CODE_INTERNAL_FUNCTION |
| @findex gdb.TYPE_CODE_INTERNAL_FUNCTION |
| @item gdb.TYPE_CODE_INTERNAL_FUNCTION |
| A function internal to @value{GDBN}. This is the type used to represent |
| convenience functions. |
| @end table |
| |
| Further support for types is provided in the @code{gdb.types} |
| Python module (@pxref{gdb.types}). |
| |
| @node Pretty Printing API |
| @subsubsection Pretty Printing API |
| |
| An example output is provided (@pxref{Pretty Printing}). |
| |
| A pretty-printer is just an object that holds a value and implements a |
| specific interface, defined here. |
| |
| @defun pretty_printer.children (self) |
| @value{GDBN} will call this method on a pretty-printer to compute the |
| children of the pretty-printer's value. |
| |
| This method must return an object conforming to the Python iterator |
| protocol. Each item returned by the iterator must be a tuple holding |
| two elements. The first element is the ``name'' of the child; the |
| second element is the child's value. The value can be any Python |
| object which is convertible to a @value{GDBN} value. |
| |
| This method is optional. If it does not exist, @value{GDBN} will act |
| as though the value has no children. |
| @end defun |
| |
| @defun pretty_printer.display_hint (self) |
| The CLI may call this method and use its result to change the |
| formatting of a value. The result will also be supplied to an MI |
| consumer as a @samp{displayhint} attribute of the variable being |
| printed. |
| |
| This method is optional. If it does exist, this method must return a |
| string. |
| |
| Some display hints are predefined by @value{GDBN}: |
| |
| @table @samp |
| @item array |
| Indicate that the object being printed is ``array-like''. The CLI |
| uses this to respect parameters such as @code{set print elements} and |
| @code{set print array}. |
| |
| @item map |
| Indicate that the object being printed is ``map-like'', and that the |
| children of this value can be assumed to alternate between keys and |
| values. |
| |
| @item string |
| Indicate that the object being printed is ``string-like''. If the |
| printer's @code{to_string} method returns a Python string of some |
| kind, then @value{GDBN} will call its internal language-specific |
| string-printing function to format the string. For the CLI this means |
| adding quotation marks, possibly escaping some characters, respecting |
| @code{set print elements}, and the like. |
| @end table |
| @end defun |
| |
| @defun pretty_printer.to_string (self) |
| @value{GDBN} will call this method to display the string |
| representation of the value passed to the object's constructor. |
| |
| When printing from the CLI, if the @code{to_string} method exists, |
| then @value{GDBN} will prepend its result to the values returned by |
| @code{children}. Exactly how this formatting is done is dependent on |
| the display hint, and may change as more hints are added. Also, |
| depending on the print settings (@pxref{Print Settings}), the CLI may |
| print just the result of @code{to_string} in a stack trace, omitting |
| the result of @code{children}. |
| |
| If this method returns a string, it is printed verbatim. |
| |
| Otherwise, if this method returns an instance of @code{gdb.Value}, |
| then @value{GDBN} prints this value. This may result in a call to |
| another pretty-printer. |
| |
| If instead the method returns a Python value which is convertible to a |
| @code{gdb.Value}, then @value{GDBN} performs the conversion and prints |
| the resulting value. Again, this may result in a call to another |
| pretty-printer. Python scalars (integers, floats, and booleans) and |
| strings are convertible to @code{gdb.Value}; other types are not. |
| |
| Finally, if this method returns @code{None} then no further operations |
| are peformed in this method and nothing is printed. |
| |
| If the result is not one of these types, an exception is raised. |
| @end defun |
| |
| @value{GDBN} provides a function which can be used to look up the |
| default pretty-printer for a @code{gdb.Value}: |
| |
| @findex gdb.default_visualizer |
| @defun gdb.default_visualizer (value) |
| This function takes a @code{gdb.Value} object as an argument. If a |
| pretty-printer for this value exists, then it is returned. If no such |
| printer exists, then this returns @code{None}. |
| @end defun |
| |
| @node Selecting Pretty-Printers |
| @subsubsection Selecting Pretty-Printers |
| |
| The Python list @code{gdb.pretty_printers} contains an array of |
| functions or callable objects that have been registered via addition |
| as a pretty-printer. Printers in this list are called @code{global} |
| printers, they're available when debugging all inferiors. |
| Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute. |
| Each @code{gdb.Objfile} also contains a @code{pretty_printers} |
| attribute. |
| |
| Each function on these lists is passed a single @code{gdb.Value} |
| argument and should return a pretty-printer object conforming to the |
| interface definition above (@pxref{Pretty Printing API}). If a function |
| cannot create a pretty-printer for the value, it should return |
| @code{None}. |
| |
| @value{GDBN} first checks the @code{pretty_printers} attribute of each |
| @code{gdb.Objfile} in the current program space and iteratively calls |
| each enabled lookup routine in the list for that @code{gdb.Objfile} |
| until it receives a pretty-printer object. |
| If no pretty-printer is found in the objfile lists, @value{GDBN} then |
| searches the pretty-printer list of the current program space, |
| calling each enabled function until an object is returned. |
| After these lists have been exhausted, it tries the global |
| @code{gdb.pretty_printers} list, again calling each enabled function until an |
| object is returned. |
| |
| The order in which the objfiles are searched is not specified. For a |
| given list, functions are always invoked from the head of the list, |
| and iterated over sequentially until the end of the list, or a printer |
| object is returned. |
| |
| For various reasons a pretty-printer may not work. |
| For example, the underlying data structure may have changed and |
| the pretty-printer is out of date. |
| |
| The consequences of a broken pretty-printer are severe enough that |
| @value{GDBN} provides support for enabling and disabling individual |
| printers. For example, if @code{print frame-arguments} is on, |
| a backtrace can become highly illegible if any argument is printed |
| with a broken printer. |
| |
| Pretty-printers are enabled and disabled by attaching an @code{enabled} |
| attribute to the registered function or callable object. If this attribute |
| is present and its value is @code{False}, the printer is disabled, otherwise |
| the printer is enabled. |
| |
| @node Writing a Pretty-Printer |
| @subsubsection Writing a Pretty-Printer |
| @cindex writing a pretty-printer |
| |
| A pretty-printer consists of two parts: a lookup function to detect |
| if the type is supported, and the printer itself. |
| |
| Here is an example showing how a @code{std::string} printer might be |
| written. @xref{Pretty Printing API}, for details on the API this class |
| must provide. |
| |
| @smallexample |
| class StdStringPrinter(object): |
| "Print a std::string" |
| |
| def __init__(self, val): |
| self.val = val |
| |
| def to_string(self): |
| return self.val['_M_dataplus']['_M_p'] |
| |
| def display_hint(self): |
| return 'string' |
| @end smallexample |
| |
| And here is an example showing how a lookup function for the printer |
| example above might be written. |
| |
| @smallexample |
| def str_lookup_function(val): |
| lookup_tag = val.type.tag |
| if lookup_tag == None: |
| return None |
| regex = re.compile("^std::basic_string<char,.*>$") |
| if regex.match(lookup_tag): |
| return StdStringPrinter(val) |
| return None |
| @end smallexample |
| |
| The example lookup function extracts the value's type, and attempts to |
| match it to a type that it can pretty-print. If it is a type the |
| printer can pretty-print, it will return a printer object. If not, it |
| returns @code{None}. |
| |
| We recommend that you put your core pretty-printers into a Python |
| package. If your pretty-printers are for use with a library, we |
| further recommend embedding a version number into the package name. |
| This practice will enable @value{GDBN} to load multiple versions of |
| your pretty-printers at the same time, because they will have |
| different names. |
| |
| You should write auto-loaded code (@pxref{Python Auto-loading}) such that it |
| can be evaluated multiple times without changing its meaning. An |
| ideal auto-load file will consist solely of @code{import}s of your |
| printer modules, followed by a call to a register pretty-printers with |
| the current objfile. |
| |
| Taken as a whole, this approach will scale nicely to multiple |
| inferiors, each potentially using a different library version. |
| Embedding a version number in the Python package name will ensure that |
| @value{GDBN} is able to load both sets of printers simultaneously. |
| Then, because the search for pretty-printers is done by objfile, and |
| because your auto-loaded code took care to register your library's |
| printers with a specific objfile, @value{GDBN} will find the correct |
| printers for the specific version of the library used by each |
| inferior. |
| |
| To continue the @code{std::string} example (@pxref{Pretty Printing API}), |
| this code might appear in @code{gdb.libstdcxx.v6}: |
| |
| @smallexample |
| def register_printers(objfile): |
| objfile.pretty_printers.append(str_lookup_function) |
| @end smallexample |
| |
| @noindent |
| And then the corresponding contents of the auto-load file would be: |
| |
| @smallexample |
| import gdb.libstdcxx.v6 |
| gdb.libstdcxx.v6.register_printers(gdb.current_objfile()) |
| @end smallexample |
| |
| The previous example illustrates a basic pretty-printer. |
| There are a few things that can be improved on. |
| The printer doesn't have a name, making it hard to identify in a |
| list of installed printers. The lookup function has a name, but |
| lookup functions can have arbitrary, even identical, names. |
| |
| Second, the printer only handles one type, whereas a library typically has |
| several types. One could install a lookup function for each desired type |
| in the library, but one could also have a single lookup function recognize |
| several types. The latter is the conventional way this is handled. |
| If a pretty-printer can handle multiple data types, then its |
| @dfn{subprinters} are the printers for the individual data types. |
| |
| The @code{gdb.printing} module provides a formal way of solving these |
| problems (@pxref{gdb.printing}). |
| Here is another example that handles multiple types. |
| |
| These are the types we are going to pretty-print: |
| |
| @smallexample |
| struct foo @{ int a, b; @}; |
| struct bar @{ struct foo x, y; @}; |
| @end smallexample |
| |
| Here are the printers: |
| |
| @smallexample |
| class fooPrinter: |
| """Print a foo object.""" |
| |
| def __init__(self, val): |
| self.val = val |
| |
| def to_string(self): |
| return ("a=<" + str(self.val["a"]) + |
| "> b=<" + str(self.val["b"]) + ">") |
| |
| class barPrinter: |
| """Print a bar object.""" |
| |
| def __init__(self, val): |
| self.val = val |
| |
| def to_string(self): |
| return ("x=<" + str(self.val["x"]) + |
| "> y=<" + str(self.val["y"]) + ">") |
| @end smallexample |
| |
| This example doesn't need a lookup function, that is handled by the |
| @code{gdb.printing} module. Instead a function is provided to build up |
| the object that handles the lookup. |
| |
| @smallexample |
| import gdb.printing |
| |
| def build_pretty_printer(): |
| pp = gdb.printing.RegexpCollectionPrettyPrinter( |
| "my_library") |
| pp.add_printer('foo', '^foo$', fooPrinter) |
| pp.add_printer('bar', '^bar$', barPrinter) |
| return pp |
| @end smallexample |
| |
| And here is the autoload support: |
| |
| @smallexample |
| import gdb.printing |
| import my_library |
| gdb.printing.register_pretty_printer( |
| gdb.current_objfile(), |
| my_library.build_pretty_printer()) |
| @end smallexample |
| |
| Finally, when this printer is loaded into @value{GDBN}, here is the |
| corresponding output of @samp{info pretty-printer}: |
| |
| @smallexample |
| (gdb) info pretty-printer |
| my_library.so: |
| my_library |
| foo |
| bar |
| @end smallexample |
| |
| @node Inferiors In Python |
| @subsubsection Inferiors In Python |
| @cindex inferiors in Python |
| |
| @findex gdb.Inferior |
| Programs which are being run under @value{GDBN} are called inferiors |
| (@pxref{Inferiors and Programs}). Python scripts can access |
| information about and manipulate inferiors controlled by @value{GDBN} |
| via objects of the @code{gdb.Inferior} class. |
| |
| The following inferior-related functions are available in the @code{gdb} |
| module: |
| |
| @defun gdb.inferiors () |
| Return a tuple containing all inferior objects. |
| @end defun |
| |
| @defun gdb.selected_inferior () |
| Return an object representing the current inferior. |
| @end defun |
| |
| A @code{gdb.Inferior} object has the following attributes: |
| |
| @table @code |
| @defvar Inferior.num |
| ID of inferior, as assigned by GDB. |
| @end defvar |
| |
| @defvar Inferior.pid |
| Process ID of the inferior, as assigned by the underlying operating |
| system. |
| @end defvar |
| |
| @defvar Inferior.was_attached |
| Boolean signaling whether the inferior was created using `attach', or |
| started by @value{GDBN} itself. |
| @end defvar |
| @end table |
| |
| A @code{gdb.Inferior} object has the following methods: |
| |
| @table @code |
| @defun Inferior.is_valid () |
| Returns @code{True} if the @code{gdb.Inferior} object is valid, |
| @code{False} if not. A @code{gdb.Inferior} object will become invalid |
| if the inferior no longer exists within @value{GDBN}. All other |
| @code{gdb.Inferior} methods will throw an exception if it is invalid |
| at the time the method is called. |
| @end defun |
| |
| @defun Inferior.threads () |
| This method returns a tuple holding all the threads which are valid |
| when it is called. If there are no valid threads, the method will |
| return an empty tuple. |
| @end defun |
| |
| @findex Inferior.read_memory |
| @defun Inferior.read_memory (address, length) |
| Read @var{length} bytes of memory from the inferior, starting at |
| @var{address}. Returns a buffer object, which behaves much like an array |
| or a string. It can be modified and given to the |
| @code{Inferior.write_memory} function. |
| @end defun |
| |
| @findex Inferior.write_memory |
| @defun Inferior.write_memory (address, buffer @r{[}, length@r{]}) |
| Write the contents of @var{buffer} to the inferior, starting at |
| @var{address}. The @var{buffer} parameter must be a Python object |
| which supports the buffer protocol, i.e., a string, an array or the |
| object returned from @code{Inferior.read_memory}. If given, @var{length} |
| determines the number of bytes from @var{buffer} to be written. |
| @end defun |
| |
| @findex gdb.search_memory |
| @defun Inferior.search_memory (address, length, pattern) |
| Search a region of the inferior memory starting at @var{address} with |
| the given @var{length} using the search pattern supplied in |
| @var{pattern}. The @var{pattern} parameter must be a Python object |
| which supports the buffer protocol, i.e., a string, an array or the |
| object returned from @code{gdb.read_memory}. Returns a Python @code{Long} |
| containing the address where the pattern was found, or @code{None} if |
| the pattern could not be found. |
| @end defun |
| @end table |
| |
| @node Events In Python |
| @subsubsection Events In Python |
| @cindex inferior events in Python |
| |
| @value{GDBN} provides a general event facility so that Python code can be |
| notified of various state changes, particularly changes that occur in |
| the inferior. |
| |
| An @dfn{event} is just an object that describes some state change. The |
| type of the object and its attributes will vary depending on the details |
| of the change. All the existing events are described below. |
| |
| In order to be notified of an event, you must register an event handler |
| with an @dfn{event registry}. An event registry is an object in the |
| @code{gdb.events} module which dispatches particular events. A registry |
| provides methods to register and unregister event handlers: |
| |
| @table @code |
| @defun EventRegistry.connect (object) |
| Add the given callable @var{object} to the registry. This object will be |
| called when an event corresponding to this registry occurs. |
| @end defun |
| |
| @defun EventRegistry.disconnect (object) |
| Remove the given @var{object} from the registry. Once removed, the object |
| will no longer receive notifications of events. |
| @end defun |
| @end table |
| |
| Here is an example: |
| |
| @smallexample |
| def exit_handler (event): |
| print "event type: exit" |
| print "exit code: %d" % (event.exit_code) |
| |
| gdb.events.exited.connect (exit_handler) |
| @end smallexample |
| |
| In the above example we connect our handler @code{exit_handler} to the |
| registry @code{events.exited}. Once connected, @code{exit_handler} gets |
| called when the inferior exits. The argument @dfn{event} in this example is |
| of type @code{gdb.ExitedEvent}. As you can see in the example the |
| @code{ExitedEvent} object has an attribute which indicates the exit code of |
| the inferior. |
| |
| The following is a listing of the event registries that are available and |
| details of the events they emit: |
| |
| @table @code |
| |
| @item events.cont |
| Emits @code{gdb.ThreadEvent}. |
| |
| Some events can be thread specific when @value{GDBN} is running in non-stop |
| mode. When represented in Python, these events all extend |
| @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead, |
| events which are emitted by this or other modules might extend this event. |
| Examples of these events are @code{gdb.BreakpointEvent} and |
| @code{gdb.ContinueEvent}. |
| |
| @table @code |
| @defvar ThreadEvent.inferior_thread |
| In non-stop mode this attribute will be set to the specific thread which was |
| involved in the emitted event. Otherwise, it will be set to @code{None}. |
| @end defvar |
| @end table |
| |
| Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}. |
| |
| This event indicates that the inferior has been continued after a stop. For |
| inherited attribute refer to @code{gdb.ThreadEvent} above. |
| |
| @item events.exited |
| Emits @code{events.ExitedEvent} which indicates that the inferior has exited. |
| @code{events.ExitedEvent} has two attributes: |
| @table @code |
| @defvar ExitedEvent.exit_code |
| An integer representing the exit code, if available, which the inferior |
| has returned. (The exit code could be unavailable if, for example, |
| @value{GDBN} detaches from the inferior.) If the exit code is unavailable, |
| the attribute does not exist. |
| @end defvar |
| @defvar ExitedEvent inferior |
| A reference to the inferior which triggered the @code{exited} event. |
| @end defvar |
| @end table |
| |
| @item events.stop |
| Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}. |
| |
| Indicates that the inferior has stopped. All events emitted by this registry |
| extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent} |
| will indicate the stopped thread when @value{GDBN} is running in non-stop |
| mode. Refer to @code{gdb.ThreadEvent} above for more details. |
| |
| Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}. |
| |
| This event indicates that the inferior or one of its threads has received as |
| signal. @code{gdb.SignalEvent} has the following attributes: |
| |
| @table @code |
| @defvar SignalEvent.stop_signal |
| A string representing the signal received by the inferior. A list of possible |
| signal values can be obtained by running the command @code{info signals} in |
| the @value{GDBN} command prompt. |
| @end defvar |
| @end table |
| |
| Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}. |
| |
| @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have |
| been hit, and has the following attributes: |
| |
| @table @code |
| @defvar BreakpointEvent.breakpoints |
| A sequence containing references to all the breakpoints (type |
| @code{gdb.Breakpoint}) that were hit. |
| @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object. |
| @end defvar |
| @defvar BreakpointEvent.breakpoint |
| A reference to the first breakpoint that was hit. |
| This function is maintained for backward compatibility and is now deprecated |
| in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute. |
| @end defvar |
| @end table |
| |
| @item events.new_objfile |
| Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has |
| been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute: |
| |
| @table @code |
| @defvar NewObjFileEvent.new_objfile |
| A reference to the object file (@code{gdb.Objfile}) which has been loaded. |
| @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object. |
| @end defvar |
| @end table |
| |
| @end table |
| |
| @node Threads In Python |
| @subsubsection Threads In Python |
| @cindex threads in python |
| |
| @findex gdb.InferiorThread |
| Python scripts can access information about, and manipulate inferior threads |
| controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class. |
| |
| The following thread-related functions are available in the @code{gdb} |
| module: |
| |
| @findex gdb.selected_thread |
| @defun gdb.selected_thread () |
| This function returns the thread object for the selected thread. If there |
| is no selected thread, this will return @code{None}. |
| @end defun |
| |
| A @code{gdb.InferiorThread} object has the following attributes: |
| |
| @table @code |
| @defvar InferiorThread.name |
| The name of the thread. If the user specified a name using |
| @code{thread name}, then this returns that name. Otherwise, if an |
| OS-supplied name is available, then it is returned. Otherwise, this |
| returns @code{None}. |
| |
| This attribute can be assigned to. The new value must be a string |
| object, which sets the new name, or @code{None}, which removes any |
| user-specified thread name. |
| @end defvar |
| |
| @defvar InferiorThread.num |
| ID of the thread, as assigned by GDB. |
| @end defvar |
| |
| @defvar InferiorThread.ptid |
| ID of the thread, as assigned by the operating system. This attribute is a |
| tuple containing three integers. The first is the Process ID (PID); the second |
| is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID). |
| Either the LWPID or TID may be 0, which indicates that the operating system |
| does not use that identifier. |
| @end defvar |
| @end table |
| |
| A @code{gdb.InferiorThread} object has the following methods: |
| |
| @table @code |
| @defun InferiorThread.is_valid () |
| Returns @code{True} if the @code{gdb.InferiorThread} object is valid, |
| @code{False} if not. A @code{gdb.InferiorThread} object will become |
| invalid if the thread exits, or the inferior that the thread belongs |
| is deleted. All other @code{gdb.InferiorThread} methods will throw an |
| exception if it is invalid at the time the method is called. |
| @end defun |
| |
| @defun InferiorThread.switch () |
| This changes @value{GDBN}'s currently selected thread to the one represented |
| by this object. |
| @end defun |
| |
| @defun InferiorThread.is_stopped () |
| Return a Boolean indicating whether the thread is stopped. |
| @end defun |
| |
| @defun InferiorThread.is_running () |
| Return a Boolean indicating whether the thread is running. |
| @end defun |
| |
| @defun InferiorThread.is_exited () |
| Return a Boolean indicating whether the thread is exited. |
| @end defun |
| @end table |
| |
| @node Commands In Python |
| @subsubsection Commands In Python |
| |
| @cindex commands in python |
| @cindex python commands |
| You can implement new @value{GDBN} CLI commands in Python. A CLI |
| command is implemented using an instance of the @code{gdb.Command} |
| class, most commonly using a subclass. |
| |
| @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]}) |
| The object initializer for @code{Command} registers the new command |
| with @value{GDBN}. This initializer is normally invoked from the |
| subclass' own @code{__init__} method. |
| |
| @var{name} is the name of the command. If @var{name} consists of |
| multiple words, then the initial words are looked for as prefix |
| commands. In this case, if one of the prefix commands does not exist, |
| an exception is raised. |
| |
| There is no support for multi-line commands. |
| |
| @var{command_class} should be one of the @samp{COMMAND_} constants |
| defined below. This argument tells @value{GDBN} how to categorize the |
| new command in the help system. |
| |
| @var{completer_class} is an optional argument. If given, it should be |
| one of the @samp{COMPLETE_} constants defined below. This argument |
| tells @value{GDBN} how to perform completion for this command. If not |
| given, @value{GDBN} will attempt to complete using the object's |
| @code{complete} method (see below); if no such method is found, an |
| error will occur when completion is attempted. |
| |
| @var{prefix} is an optional argument. If @code{True}, then the new |
| command is a prefix command; sub-commands of this command may be |
| registered. |
| |
| The help text for the new command is taken from the Python |
| documentation string for the command's class, if there is one. If no |
| documentation string is provided, the default value ``This command is |
| not documented.'' is used. |
| @end defun |
| |
| @cindex don't repeat Python command |
| @defun Command.dont_repeat () |
| By default, a @value{GDBN} command is repeated when the user enters a |
| blank line at the command prompt. A command can suppress this |
| behavior by invoking the @code{dont_repeat} method. This is similar |
| to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}. |
| @end defun |
| |
| @defun Command.invoke (argument, from_tty) |
| This method is called by @value{GDBN} when this command is invoked. |
| |
| @var{argument} is a string. It is the argument to the command, after |
| leading and trailing whitespace has been stripped. |
| |
| @var{from_tty} is a boolean argument. When true, this means that the |
| command was entered by the user at the terminal; when false it means |
| that the command came from elsewhere. |
| |
| If this method throws an exception, it is turned into a @value{GDBN} |
| @code{error} call. Otherwise, the return value is ignored. |
| |
| @findex gdb.string_to_argv |
| To break @var{argument} up into an argv-like string use |
| @code{gdb.string_to_argv}. This function behaves identically to |
| @value{GDBN}'s internal argument lexer @code{buildargv}. |
| It is recommended to use this for consistency. |
| Arguments are separated by spaces and may be quoted. |
| Example: |
| |
| @smallexample |
| print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"") |
| ['1', '2 "3', '4 "5', "6 '7"] |
| @end smallexample |
| |
| @end defun |
| |
| @cindex completion of Python commands |
| @defun Command.complete (text, word) |
| This method is called by @value{GDBN} when the user attempts |
| completion on this command. All forms of completion are handled by |
| this method, that is, the @key{TAB} and @key{M-?} key bindings |
| (@pxref{Completion}), and the @code{complete} command (@pxref{Help, |
| complete}). |
| |
| The arguments @var{text} and @var{word} are both strings. @var{text} |
| holds the complete command line up to the cursor's location. |
| @var{word} holds the last word of the command line; this is computed |
| using a word-breaking heuristic. |
| |
| The @code{complete} method can return several values: |
| @itemize @bullet |
| @item |
| If the return value is a sequence, the contents of the sequence are |
| used as the completions. It is up to @code{complete} to ensure that the |
| contents actually do complete the word. A zero-length sequence is |
| allowed, it means that there were no completions available. Only |
| string elements of the sequence are used; other elements in the |
| sequence are ignored. |
| |
| @item |
| If the return value is one of the @samp{COMPLETE_} constants defined |
| below, then the corresponding @value{GDBN}-internal completion |
| function is invoked, and its result is used. |
| |
| @item |
| All other results are treated as though there were no available |
| completions. |
| @end itemize |
| @end defun |
| |
| When a new command is registered, it must be declared as a member of |
| some general class of commands. This is used to classify top-level |
| commands in the on-line help system; note that prefix commands are not |
| listed under their own category but rather that of their top-level |
| command. The available classifications are represented by constants |
| defined in the @code{gdb} module: |
| |
| @table @code |
| @findex COMMAND_NONE |
| @findex gdb.COMMAND_NONE |
| @item gdb.COMMAND_NONE |
| The command does not belong to any particular class. A command in |
| this category will not be displayed in any of the help categories. |
| |
| @findex COMMAND_RUNNING |
| @findex gdb.COMMAND_RUNNING |
| @item gdb.COMMAND_RUNNING |
| The command is related to running the inferior. For example, |
| @code{start}, @code{step}, and @code{continue} are in this category. |
| Type @kbd{help running} at the @value{GDBN} prompt to see a list of |
| commands in this category. |
| |
| @findex COMMAND_DATA |
| @findex gdb.COMMAND_DATA |
| @item gdb.COMMAND_DATA |
| The command is related to data or variables. For example, |
| @code{call}, @code{find}, and @code{print} are in this category. Type |
| @kbd{help data} at the @value{GDBN} prompt to see a list of commands |
| in this category. |
| |
| @findex COMMAND_STACK |
| @findex gdb.COMMAND_STACK |
| @item gdb.COMMAND_STACK |
| The command has to do with manipulation of the stack. For example, |
| @code{backtrace}, @code{frame}, and @code{return} are in this |
| category. Type @kbd{help stack} at the @value{GDBN} prompt to see a |
| list of commands in this category. |
| |
| @findex COMMAND_FILES |
| @findex gdb.COMMAND_FILES |
| @item gdb.COMMAND_FILES |
| This class is used for file-related commands. For example, |
| @code{file}, @code{list} and @code{section} are in this category. |
| Type @kbd{help files} at the @value{GDBN} prompt to see a list of |
| commands in this category. |
| |
| @findex COMMAND_SUPPORT |
| @findex gdb.COMMAND_SUPPORT |
| @item gdb.COMMAND_SUPPORT |
| This should be used for ``support facilities'', generally meaning |
| things that are useful to the user when interacting with @value{GDBN}, |
| but not related to the state of the inferior. For example, |
| @code{help}, @code{make}, and @code{shell} are in this category. Type |
| @kbd{help support} at the @value{GDBN} prompt to see a list of |
| commands in this category. |
| |
| @findex COMMAND_STATUS |
| @findex gdb.COMMAND_STATUS |
| @item gdb.COMMAND_STATUS |
| The command is an @samp{info}-related command, that is, related to the |
| state of @value{GDBN} itself. For example, @code{info}, @code{macro}, |
| and @code{show} are in this category. Type @kbd{help status} at the |
| @value{GDBN} prompt to see a list of commands in this category. |
| |
| @findex COMMAND_BREAKPOINTS |
| @findex gdb.COMMAND_BREAKPOINTS |
| @item gdb.COMMAND_BREAKPOINTS |
| The command has to do with breakpoints. For example, @code{break}, |
| @code{clear}, and @code{delete} are in this category. Type @kbd{help |
| breakpoints} at the @value{GDBN} prompt to see a list of commands in |
| this category. |
| |
| @findex COMMAND_TRACEPOINTS |
| @findex gdb.COMMAND_TRACEPOINTS |
| @item gdb.COMMAND_TRACEPOINTS |
| The command has to do with tracepoints. For example, @code{trace}, |
| @code{actions}, and @code{tfind} are in this category. Type |
| @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of |
| commands in this category. |
| |
| @findex COMMAND_USER |
| @findex gdb.COMMAND_USER |
| @item gdb.COMMAND_USER |
| The command is a general purpose command for the user, and typically |
| does not fit in one of the other categories. |
| Type @kbd{help user-defined} at the @value{GDBN} prompt to see |
| a list of commands in this category, as well as the list of gdb macros |
| (@pxref{Sequences}). |
| |
| @findex COMMAND_OBSCURE |
| @findex gdb.COMMAND_OBSCURE |
| @item gdb.COMMAND_OBSCURE |
| The command is only used in unusual circumstances, or is not of |
| general interest to users. For example, @code{checkpoint}, |
| @code{fork}, and @code{stop} are in this category. Type @kbd{help |
| obscure} at the @value{GDBN} prompt to see a list of commands in this |
| category. |
| |
| @findex COMMAND_MAINTENANCE |
| @findex gdb.COMMAND_MAINTENANCE |
| @item gdb.COMMAND_MAINTENANCE |
| The command is only useful to @value{GDBN} maintainers. The |
| @code{maintenance} and @code{flushregs} commands are in this category. |
| Type @kbd{help internals} at the @value{GDBN} prompt to see a list of |
| commands in this category. |
| @end table |
| |
| A new command can use a predefined completion function, either by |
| specifying it via an argument at initialization, or by returning it |
| from the @code{complete} method. These predefined completion |
| constants are all defined in the @code{gdb} module: |
| |
| @table @code |
| @findex COMPLETE_NONE |
| @findex gdb.COMPLETE_NONE |
| @item gdb.COMPLETE_NONE |
| This constant means that no completion should be done. |
| |
| @findex COMPLETE_FILENAME |
| @findex gdb.COMPLETE_FILENAME |
| @item gdb.COMPLETE_FILENAME |
| This constant means that filename completion should be performed. |
| |
| @findex COMPLETE_LOCATION |
| @findex gdb.COMPLETE_LOCATION |
| @item gdb.COMPLETE_LOCATION |
| This constant means that location completion should be done. |
| @xref{Specify Location}. |
| |
| @findex COMPLETE_COMMAND |
| @findex gdb.COMPLETE_COMMAND |
| @item gdb.COMPLETE_COMMAND |
| This constant means that completion should examine @value{GDBN} |
| command names. |
| |
| @findex COMPLETE_SYMBOL |
| @findex gdb.COMPLETE_SYMBOL |
| @item gdb.COMPLETE_SYMBOL |
| This constant means that completion should be done using symbol names |
| as the source. |
| @end table |
| |
| The following code snippet shows how a trivial CLI command can be |
| implemented in Python: |
| |
| @smallexample |
| class HelloWorld (gdb.Command): |
| """Greet the whole world.""" |
| |
| def __init__ (self): |
| super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) |
| |
| def invoke (self, arg, from_tty): |
| print "Hello, World!" |
| |
| HelloWorld () |
| @end smallexample |
| |
| The last line instantiates the class, and is necessary to trigger the |
| registration of the command with @value{GDBN}. Depending on how the |
| Python code is read into @value{GDBN}, you may need to import the |
| @code{gdb} module explicitly. |
| |
| @node Parameters In Python |
| @subsubsection Parameters In Python |
| |
| @cindex parameters in python |
| @cindex python parameters |
| @tindex gdb.Parameter |
| @tindex Parameter |
| You can implement new @value{GDBN} parameters using Python. A new |
| parameter is implemented as an instance of the @code{gdb.Parameter} |
| class. |
| |
| Parameters are exposed to the user via the @code{set} and |
| @code{show} commands. @xref{Help}. |
| |
| There are many parameters that already exist and can be set in |
| @value{GDBN}. Two examples are: @code{set follow fork} and |
| @code{set charset}. Setting these parameters influences certain |
| behavior in @value{GDBN}. Similarly, you can define parameters that |
| can be used to influence behavior in custom Python scripts and commands. |
| |
| @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]}) |
| The object initializer for @code{Parameter} registers the new |
| parameter with @value{GDBN}. This initializer is normally invoked |
| from the subclass' own @code{__init__} method. |
| |
| @var{name} is the name of the new parameter. If @var{name} consists |
| of multiple words, then the initial words are looked for as prefix |
| parameters. An example of this can be illustrated with the |
| @code{set print} set of parameters. If @var{name} is |
| @code{print foo}, then @code{print} will be searched as the prefix |
| parameter. In this case the parameter can subsequently be accessed in |
| @value{GDBN} as @code{set print foo}. |
| |
| If @var{name} consists of multiple words, and no prefix parameter group |
| can be found, an exception is raised. |
| |
| @var{command-class} should be one of the @samp{COMMAND_} constants |
| (@pxref{Commands In Python}). This argument tells @value{GDBN} how to |
| categorize the new parameter in the help system. |
| |
| @var{parameter-class} should be one of the @samp{PARAM_} constants |
| defined below. This argument tells @value{GDBN} the type of the new |
| parameter; this information is used for input validation and |
| completion. |
| |
| If @var{parameter-class} is @code{PARAM_ENUM}, then |
| @var{enum-sequence} must be a sequence of strings. These strings |
| represent the possible values for the parameter. |
| |
| If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence |
| of a fourth argument will cause an exception to be thrown. |
| |
| The help text for the new parameter is taken from the Python |
| documentation string for the parameter's class, if there is one. If |
| there is no documentation string, a default value is used. |
| @end defun |
| |
| @defvar Parameter.set_doc |
| If this attribute exists, and is a string, then its value is used as |
| the help text for this parameter's @code{set} command. The value is |
| examined when @code{Parameter.__init__} is invoked; subsequent changes |
| have no effect. |
| @end defvar |
| |
| @defvar Parameter.show_doc |
| If this attribute exists, and is a string, then its value is used as |
| the help text for this parameter's @code{show} command. The value is |
| examined when @code{Parameter.__init__} is invoked; subsequent changes |
| have no effect. |
| @end defvar |
| |
| @defvar Parameter.value |
| The @code{value} attribute holds the underlying value of the |
| parameter. It can be read and assigned to just as any other |
| attribute. @value{GDBN} does validation when assignments are made. |
| @end defvar |
| |
| There are two methods that should be implemented in any |
| @code{Parameter} class. These are: |
| |
| @defun Parameter.get_set_string (self) |
| @value{GDBN} will call this method when a @var{parameter}'s value has |
| been changed via the @code{set} API (for example, @kbd{set foo off}). |
| The @code{value} attribute has already been populated with the new |
| value and may be used in output. This method must return a string. |
| @end defun |
| |
| @defun Parameter.get_show_string (self, svalue) |
| @value{GDBN} will call this method when a @var{parameter}'s |
| @code{show} API has been invoked (for example, @kbd{show foo}). The |
| argument @code{svalue} receives the string representation of the |
| current value. This method must return a string. |
| @end defun |
| |
| When a new parameter is defined, its type must be specified. The |
| available types are represented by constants defined in the @code{gdb} |
| module: |
| |
| @table @code |
| @findex PARAM_BOOLEAN |
| @findex gdb.PARAM_BOOLEAN |
| @item gdb.PARAM_BOOLEAN |
| The value is a plain boolean. The Python boolean values, @code{True} |
| and @code{False} are the only valid values. |
| |
| @findex PARAM_AUTO_BOOLEAN |
| @findex gdb.PARAM_AUTO_BOOLEAN |
| @item gdb.PARAM_AUTO_BOOLEAN |
| The value has three possible states: true, false, and @samp{auto}. In |
| Python, true and false are represented using boolean constants, and |
| @samp{auto} is represented using @code{None}. |
| |
| @findex PARAM_UINTEGER |
| @findex gdb.PARAM_UINTEGER |
| @item gdb.PARAM_UINTEGER |
| The value is an unsigned integer. The value of 0 should be |
| interpreted to mean ``unlimited''. |
| |
| @findex PARAM_INTEGER |
| @findex gdb.PARAM_INTEGER |
| @item gdb.PARAM_INTEGER |
| The value is a signed integer. The value of 0 should be interpreted |
| to mean ``unlimited''. |
| |
| @findex PARAM_STRING |
| @findex gdb.PARAM_STRING |
| @item gdb.PARAM_STRING |
| The value is a string. When the user modifies the string, any escape |
| sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are |
| translated into corresponding characters and encoded into the current |
| host charset. |
| |
| @findex PARAM_STRING_NOESCAPE |
| @findex gdb.PARAM_STRING_NOESCAPE |
| @item gdb.PARAM_STRING_NOESCAPE |
| The value is a string. When the user modifies the string, escapes are |
| passed through untranslated. |
| |
| @findex PARAM_OPTIONAL_FILENAME |
| @findex gdb.PARAM_OPTIONAL_FILENAME |
| @item gdb.PARAM_OPTIONAL_FILENAME |
| The value is a either a filename (a string), or @code{None}. |
| |
| @findex PARAM_FILENAME |
| @findex gdb.PARAM_FILENAME |
| @item gdb.PARAM_FILENAME |
| The value is a filename. This is just like |
| @code{PARAM_STRING_NOESCAPE}, but uses file names for completion. |
| |
| @findex PARAM_ZINTEGER |
| @findex gdb.PARAM_ZINTEGER |
| @item gdb.PARAM_ZINTEGER |
| The value is an integer. This is like @code{PARAM_INTEGER}, except 0 |
| is interpreted as itself. |
| |
| @findex PARAM_ENUM |
| @findex gdb.PARAM_ENUM |
| @item gdb.PARAM_ENUM |
| The value is a string, which must be one of a collection string |
| constants provided when the parameter is created. |
| @end table |
| |
| @node Functions In Python |
| @subsubsection Writing new convenience functions |
| |
| @cindex writing convenience functions |
| @cindex convenience functions in python |
| @cindex python convenience functions |
| @tindex gdb.Function |
| @tindex Function |
| You can implement new convenience functions (@pxref{Convenience Vars}) |
| in Python. A convenience function is an instance of a subclass of the |
| class @code{gdb.Function}. |
| |
| @defun Function.__init__ (name) |
| The initializer for @code{Function} registers the new function with |
| @value{GDBN}. The argument @var{name} is the name of the function, |
| a string. The function will be visible to the user as a convenience |
| variable of type @code{internal function}, whose name is the same as |
| the given @var{name}. |
| |
| The documentation for the new function is taken from the documentation |
| string for the new class. |
| @end defun |
| |
| @defun Function.invoke (@var{*args}) |
| When a convenience function is evaluated, its arguments are converted |
| to instances of @code{gdb.Value}, and then the function's |
| @code{invoke} method is called. Note that @value{GDBN} does not |
| predetermine the arity of convenience functions. Instead, all |
| available arguments are passed to @code{invoke}, following the |
| standard Python calling convention. In particular, a convenience |
| function can have default values for parameters without ill effect. |
| |
| The return value of this method is used as its value in the enclosing |
| expression. If an ordinary Python value is returned, it is converted |
| to a @code{gdb.Value} following the usual rules. |
| @end defun |
| |
| The following code snippet shows how a trivial convenience function can |
| be implemented in Python: |
| |
| @smallexample |
| class Greet (gdb.Function): |
| """Return string to greet someone. |
| Takes a name as argument.""" |
| |
| def __init__ (self): |
| super (Greet, self).__init__ ("greet") |
| |
| def invoke (self, name): |
| return "Hello, %s!" % name.string () |
| |
| Greet () |
| @end smallexample |
| |
| The last line instantiates the class, and is necessary to trigger the |
| registration of the function with @value{GDBN}. Depending on how the |
| Python code is read into @value{GDBN}, you may need to import the |
| @code{gdb} module explicitly. |
| |
| @node Progspaces In Python |
| @subsubsection Program Spaces In Python |
| |
| @cindex progspaces in python |
| @tindex gdb.Progspace |
| @tindex Progspace |
| A program space, or @dfn{progspace}, represents a symbolic view |
| of an address space. |
| It consists of all of the objfiles of the program. |
| @xref{Objfiles In Python}. |
| @xref{Inferiors and Programs, program spaces}, for more details |
| about program spaces. |
| |
| The following progspace-related functions are available in the |
| @code{gdb} module: |
| |
| @findex gdb.current_progspace |
| @defun gdb.current_progspace () |
| This function returns the program space of the currently selected inferior. |
| @xref{Inferiors and Programs}. |
| @end defun |
| |
| @findex gdb.progspaces |
| @defun gdb.progspaces () |
| Return a sequence of all the progspaces currently known to @value{GDBN}. |
| @end defun |
| |
| Each progspace is represented by an instance of the @code{gdb.Progspace} |
| class. |
| |
| @defvar Progspace.filename |
| The file name of the progspace as a string. |
| @end defvar |
| |
| @defvar Progspace.pretty_printers |
| The @code{pretty_printers} attribute is a list of functions. It is |
| used to look up pretty-printers. A @code{Value} is passed to each |
| function in order; if the function returns @code{None}, then the |
| search continues. Otherwise, the return value should be an object |
| which is used to format the value. @xref{Pretty Printing API}, for more |
| information. |
| @end defvar |
| |
| @node Objfiles In Python |
| @subsubsection Objfiles In Python |
| |
| @cindex objfiles in python |
| @tindex gdb.Objfile |
| @tindex Objfile |
| @value{GDBN} loads symbols for an inferior from various |
| symbol-containing files (@pxref{Files}). These include the primary |
| executable file, any shared libraries used by the inferior, and any |
| separate debug info files (@pxref{Separate Debug Files}). |
| @value{GDBN} calls these symbol-containing files @dfn{objfiles}. |
| |
| The following objfile-related functions are available in the |
| @code{gdb} module: |
| |
| @findex gdb.current_objfile |
| @defun gdb.current_objfile () |
| When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN} |
| sets the ``current objfile'' to the corresponding objfile. This |
| function returns the current objfile. If there is no current objfile, |
| this function returns @code{None}. |
| @end defun |
| |
| @findex gdb.objfiles |
| @defun gdb.objfiles () |
| Return a sequence of all the objfiles current known to @value{GDBN}. |
| @xref{Objfiles In Python}. |
| @end defun |
| |
| Each objfile is represented by an instance of the @code{gdb.Objfile} |
| class. |
| |
| @defvar Objfile.filename |
| The file name of the objfile as a string. |
| @end defvar |
| |
| @defvar Objfile.pretty_printers |
| The @code{pretty_printers} attribute is a list of functions. It is |
| used to look up pretty-printers. A @code{Value} is passed to each |
| function in order; if the function returns @code{None}, then the |
| search continues. Otherwise, the return value should be an object |
| which is used to format the value. @xref{Pretty Printing API}, for more |
| information. |
| @end defvar |
| |
| A @code{gdb.Objfile} object has the following methods: |
| |
| @defun Objfile.is_valid () |
| Returns @code{True} if the @code{gdb.Objfile} object is valid, |
| @code{False} if not. A @code{gdb.Objfile} object can become invalid |
| if the object file it refers to is not loaded in @value{GDBN} any |
| longer. All other @code{gdb.Objfile} methods will throw an exception |
| if it is invalid at the time the method is called. |
| @end defun |
| |
| @node Frames In Python |
| @subsubsection Accessing inferior stack frames from Python. |
| |
| @cindex frames in python |
| When the debugged program stops, @value{GDBN} is able to analyze its call |
| stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class |
| represents a frame in the stack. A @code{gdb.Frame} object is only valid |
| while its corresponding frame exists in the inferior's stack. If you try |
| to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error} |
| exception (@pxref{Exception Handling}). |
| |
| Two @code{gdb.Frame} objects can be compared for equality with the @code{==} |
| operator, like: |
| |
| @smallexample |
| (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame () |
| True |
| @end smallexample |
| |
| The following frame-related functions are available in the @code{gdb} module: |
| |
| @findex gdb.selected_frame |
| @defun gdb.selected_frame () |
| Return the selected frame object. (@pxref{Selection,,Selecting a Frame}). |
| @end defun |
| |
| @findex gdb.newest_frame |
| @defun gdb.newest_frame () |
| Return the newest frame object for the selected thread. |
| @end defun |
| |
| @defun gdb.frame_stop_reason_string (reason) |
| Return a string explaining the reason why @value{GDBN} stopped unwinding |
| frames, as expressed by the given @var{reason} code (an integer, see the |
| @code{unwind_stop_reason} method further down in this section). |
| @end defun |
| |
| A @code{gdb.Frame} object has the following methods: |
| |
| @table @code |
| @defun Frame.is_valid () |
| Returns true if the @code{gdb.Frame} object is valid, false if not. |
| A frame object can become invalid if the frame it refers to doesn't |
| exist anymore in the inferior. All @code{gdb.Frame} methods will throw |
| an exception if it is invalid at the time the method is called. |
| @end defun |
| |
| @defun Frame.name () |
| Returns the function name of the frame, or @code{None} if it can't be |
| obtained. |
| @end defun |
| |
| @defun Frame.type () |
| Returns the type of the frame. The value can be one of: |
| @table @code |
| @item gdb.NORMAL_FRAME |
| An ordinary stack frame. |
| |
| @item gdb.DUMMY_FRAME |
| A fake stack frame that was created by @value{GDBN} when performing an |
| inferior function call. |
| |
| @item gdb.INLINE_FRAME |
| A frame representing an inlined function. The function was inlined |
| into a @code{gdb.NORMAL_FRAME} that is older than this one. |
| |
| @item gdb.TAILCALL_FRAME |
| A frame representing a tail call. @xref{Tail Call Frames}. |
| |
| @item gdb.SIGTRAMP_FRAME |
| A signal trampoline frame. This is the frame created by the OS when |
| it calls into a signal handler. |
| |
| @item gdb.ARCH_FRAME |
| A fake stack frame representing a cross-architecture call. |
| |
| @item gdb.SENTINEL_FRAME |
| This is like @code{gdb.NORMAL_FRAME}, but it is only used for the |
| newest frame. |
| @end table |
| @end defun |
| |
| @defun Frame.unwind_stop_reason () |
| Return an integer representing the reason why it's not possible to find |
| more frames toward the outermost frame. Use |
| @code{gdb.frame_stop_reason_string} to convert the value returned by this |
| function to a string. The value can be one of: |
| |
| @table @code |
| @item gdb.FRAME_UNWIND_NO_REASON |
| No particular reason (older frames should be available). |
| |
| @item gdb.FRAME_UNWIND_NULL_ID |
| The previous frame's analyzer returns an invalid result. |
| |
| @item gdb.FRAME_UNWIND_OUTERMOST |
| This frame is the outermost. |
| |
| @item gdb.FRAME_UNWIND_UNAVAILABLE |
| Cannot unwind further, because that would require knowing the |
| values of registers or memory that have not been collected. |
| |
| @item gdb.FRAME_UNWIND_INNER_ID |
| This frame ID looks like it ought to belong to a NEXT frame, |
| but we got it for a PREV frame. Normally, this is a sign of |
| unwinder failure. It could also indicate stack corruption. |
| |
| @item gdb.FRAME_UNWIND_SAME_ID |
| This frame has the same ID as the previous one. That means |
| that unwinding further would almost certainly give us another |
| frame with exactly the same ID, so break the chain. Normally, |
| this is a sign of unwinder failure. It could also indicate |
| stack corruption. |
| |
| @item gdb.FRAME_UNWIND_NO_SAVED_PC |
| The frame unwinder did not find any saved PC, but we needed |
| one to unwind further. |
| |
| @item gdb.FRAME_UNWIND_FIRST_ERROR |
| Any stop reason greater or equal to this value indicates some kind |
| of error. This special value facilitates writing code that tests |
| for errors in unwinding in a way that will work correctly even if |
| the list of the other values is modified in future @value{GDBN} |
| versions. Using it, you could write: |
| @smallexample |
| reason = gdb.selected_frame().unwind_stop_reason () |
| reason_str = gdb.frame_stop_reason_string (reason) |
| if reason >= gdb.FRAME_UNWIND_FIRST_ERROR: |
| print "An error occured: %s" % reason_str |
| @end smallexample |
| @end table |
| |
| @end defun |
| |
| @defun Frame.pc () |
| Returns the frame's resume address. |
| @end defun |
| |
| @defun Frame.block () |
| Return the frame's code block. @xref{Blocks In Python}. |
| @end defun |
| |
| @defun Frame.function () |
| Return the symbol for the function corresponding to this frame. |
| @xref{Symbols In Python}. |
| @end defun |
| |
| @defun Frame.older () |
| Return the frame that called this frame. |
| @end defun |
| |
| @defun Frame.newer () |
| Return the frame called by this frame. |
| @end defun |
| |
| @defun Frame.find_sal () |
| Return the frame's symtab and line object. |
| @xref{Symbol Tables In Python}. |
| @end defun |
| |
| @defun Frame.read_var (variable @r{[}, block@r{]}) |
| Return the value of @var{variable} in this frame. If the optional |
| argument @var{block} is provided, search for the variable from that |
| block; otherwise start at the frame's current block (which is |
| determined by the frame's current program counter). @var{variable} |
| must be a string or a @code{gdb.Symbol} object. @var{block} must be a |
| @code{gdb.Block} object. |
| @end defun |
| |
| @defun Frame.select () |
| Set this frame to be the selected frame. @xref{Stack, ,Examining the |
| Stack}. |
| @end defun |
| @end table |
| |
| @node Blocks In Python |
| @subsubsection Accessing frame blocks from Python. |
| |
| @cindex blocks in python |
| @tindex gdb.Block |
| |
| Within each frame, @value{GDBN} maintains information on each block |
| stored in that frame. These blocks are organized hierarchically, and |
| are represented individually in Python as a @code{gdb.Block}. |
| Please see @ref{Frames In Python}, for a more in-depth discussion on |
| frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more |
| detailed technical information on @value{GDBN}'s book-keeping of the |
| stack. |
| |
| A @code{gdb.Block} is iterable. The iterator returns the symbols |
| (@pxref{Symbols In Python}) local to the block. Python programs |
| should not assume that a specific block object will always contain a |
| given symbol, since changes in @value{GDBN} features and |
| infrastructure may cause symbols move across blocks in a symbol |
| table. |
| |
| The following block-related functions are available in the @code{gdb} |
| module: |
| |
| @findex gdb.block_for_pc |
| @defun gdb.block_for_pc (pc) |
| Return the @code{gdb.Block} containing the given @var{pc} value. If the |
| block cannot be found for the @var{pc} value specified, the function |
| will return @code{None}. |
| @end defun |
| |
| A @code{gdb.Block} object has the following methods: |
| |
| @table @code |
| @defun Block.is_valid () |
| Returns @code{True} if the @code{gdb.Block} object is valid, |
| @code{False} if not. A block object can become invalid if the block it |
| refers to doesn't exist anymore in the inferior. All other |
| @code{gdb.Block} methods will throw an exception if it is invalid at |
| the time the method is called. The block's validity is also checked |
| during iteration over symbols of the block. |
| @end defun |
| @end table |
| |
| A @code{gdb.Block} object has the following attributes: |
| |
| @table @code |
| @defvar Block.start |
| The start address of the block. This attribute is not writable. |
| @end defvar |
| |
| @defvar Block.end |
| The end address of the block. This attribute is not writable. |
| @end defvar |
| |
| @defvar Block.function |
| The name of the block represented as a @code{gdb.Symbol}. If the |
| block is not named, then this attribute holds @code{None}. This |
| attribute is not writable. |
| @end defvar |
| |
| @defvar Block.superblock |
| The block containing this block. If this parent block does not exist, |
| this attribute holds @code{None}. This attribute is not writable. |
| @end defvar |
| |
| @defvar Block.global_block |
| The global block associated with this block. This attribute is not |
| writable. |
| @end defvar |
| |
| @defvar Block.static_block |
| The static block associated with this block. This attribute is not |
| writable. |
| @end defvar |
| |
| @defvar Block.is_global |
| @code{True} if the @code{gdb.Block} object is a global block, |
| @code{False} if not. This attribute is not |
| writable. |
| @end defvar |
| |
| @defvar Block.is_static |
| @code{True} if the @code{gdb.Block} object is a static block, |
| @code{False} if not. This attribute is not writable. |
| @end defvar |
| @end table |
| |
| @node Symbols In Python |
| @subsubsection Python representation of Symbols. |
| |
| @cindex symbols in python |
| @tindex gdb.Symbol |
| |
| @value{GDBN} represents every variable, function and type as an |
| entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}. |
| Similarly, Python represents these symbols in @value{GDBN} with the |
| @code{gdb.Symbol} object. |
| |
| The following symbol-related functions are available in the @code{gdb} |
| module: |
| |
| @findex gdb.lookup_symbol |
| @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]}) |
| This function searches for a symbol by name. The search scope can be |
| restricted to the parameters defined in the optional domain and block |
| arguments. |
| |
| @var{name} is the name of the symbol. It must be a string. The |
| optional @var{block} argument restricts the search to symbols visible |
| in that @var{block}. The @var{block} argument must be a |
| @code{gdb.Block} object. If omitted, the block for the current frame |
| is used. The optional @var{domain} argument restricts |
| the search to the domain type. The @var{domain} argument must be a |
| domain constant defined in the @code{gdb} module and described later |
| in this chapter. |
| |
| The result is a tuple of two elements. |
| The first element is a @code{gdb.Symbol} object or @code{None} if the symbol |
| is not found. |
| If the symbol is found, the second element is @code{True} if the symbol |
| is a field of a method's object (e.g., @code{this} in C@t{++}), |
| otherwise it is @code{False}. |
| If the symbol is not found, the second element is @code{False}. |
| @end defun |
| |
| @findex gdb.lookup_global_symbol |
| @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]}) |
| This function searches for a global symbol by name. |
| The search scope can be restricted to by the domain argument. |
| |
| @var{name} is the name of the symbol. It must be a string. |
| The optional @var{domain} argument restricts the search to the domain type. |
| The @var{domain} argument must be a domain constant defined in the @code{gdb} |
| module and described later in this chapter. |
| |
| The result is a @code{gdb.Symbol} object or @code{None} if the symbol |
| is not found. |
| @end defun |
| |
| A @code{gdb.Symbol} object has the following attributes: |
| |
| @table @code |
| @defvar Symbol.type |
| The type of the symbol or @code{None} if no type is recorded. |
| This attribute is represented as a @code{gdb.Type} object. |
| @xref{Types In Python}. This attribute is not writable. |
| @end defvar |
| |
| @defvar Symbol.symtab |
| The symbol table in which the symbol appears. This attribute is |
| represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In |
| Python}. This attribute is not writable. |
| @end defvar |
| |
| @defvar Symbol.line |
| The line number in the source code at which the symbol was defined. |
| This is an integer. |
| @end defvar |
| |
| @defvar Symbol.name |
| The name of the symbol as a string. This attribute is not writable. |
| @end defvar |
| |
| @defvar Symbol.linkage_name |
| The name of the symbol, as used by the linker (i.e., may be mangled). |
| This attribute is not writable. |
| @end defvar |
| |
| @defvar Symbol.print_name |
| The name of the symbol in a form suitable for output. This is either |
| @code{name} or @code{linkage_name}, depending on whether the user |
| asked @value{GDBN} to display demangled or mangled names. |
| @end defvar |
| |
| @defvar Symbol.addr_class |
| The address class of the symbol. This classifies how to find the value |
| of a symbol. Each address class is a constant defined in the |
| @code{gdb} module and described later in this chapter. |
| @end defvar |
| |
| @defvar Symbol.needs_frame |
| This is @code{True} if evaluating this symbol's value requires a frame |
| (@pxref{Frames In Python}) and @code{False} otherwise. Typically, |
| local variables will require a frame, but other symbols will not. |
| @end defvar |
| |
| @defvar Symbol.is_argument |
| @code{True} if the symbol is an argument of a function. |
| @end defvar |
| |
| @defvar Symbol.is_constant |
| @code{True} if the symbol is a constant. |
| @end defvar |
| |
| @defvar Symbol.is_function |
| @code{True} if the symbol is a function or a method. |
| @end defvar |
| |
| @defvar Symbol.is_variable |
| @code{True} if the symbol is a variable. |
| @end defvar |
| @end table |
| |
| A @code{gdb.Symbol} object has the following methods: |
| |
| @table @code |
| @defun Symbol.is_valid () |
| Returns @code{True} if the @code{gdb.Symbol} object is valid, |
| @code{False} if not. A @code{gdb.Symbol} object can become invalid if |
| the symbol it refers to does not exist in @value{GDBN} any longer. |
| All other @code{gdb.Symbol} methods will throw an exception if it is |
| invalid at the time the method is called. |
| @end defun |
| |
| @defun Symbol.value (@r{[}frame@r{]}) |
| Compute the value of the symbol, as a @code{gdb.Value}. For |
| functions, this computes the address of the function, cast to the |
| appropriate type. If the symbol requires a frame in order to compute |
| its value, then @var{frame} must be given. If @var{frame} is not |
| given, or if @var{frame} is invalid, then this method will throw an |
| exception. |
| @end defun |
| @end table |
| |
| The available domain categories in @code{gdb.Symbol} are represented |
| as constants in the @code{gdb} module: |
| |
| @table @code |
| @findex SYMBOL_UNDEF_DOMAIN |
| @findex gdb.SYMBOL_UNDEF_DOMAIN |
| @item gdb.SYMBOL_UNDEF_DOMAIN |
| This is used when a domain has not been discovered or none of the |
| following domains apply. This usually indicates an error either |
| in the symbol information or in @value{GDBN}'s handling of symbols. |
| @findex SYMBOL_VAR_DOMAIN |
| @findex gdb.SYMBOL_VAR_DOMAIN |
| @item gdb.SYMBOL_VAR_DOMAIN |
| This domain contains variables, function names, typedef names and enum |
| type values. |
| @findex SYMBOL_STRUCT_DOMAIN |
| @findex gdb.SYMBOL_STRUCT_DOMAIN |
| @item gdb.SYMBOL_STRUCT_DOMAIN |
| This domain holds struct, union and enum type names. |
| @findex SYMBOL_LABEL_DOMAIN |
| @findex gdb.SYMBOL_LABEL_DOMAIN |
| @item gdb.SYMBOL_LABEL_DOMAIN |
| This domain contains names of labels (for gotos). |
| @findex SYMBOL_VARIABLES_DOMAIN |
| @findex gdb.SYMBOL_VARIABLES_DOMAIN |
| @item gdb.SYMBOL_VARIABLES_DOMAIN |
| This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it |
| contains everything minus functions and types. |
| @findex SYMBOL_FUNCTIONS_DOMAIN |
| @findex gdb.SYMBOL_FUNCTIONS_DOMAIN |
| @item gdb.SYMBOL_FUNCTION_DOMAIN |
| This domain contains all functions. |
| @findex SYMBOL_TYPES_DOMAIN |
| @findex gdb.SYMBOL_TYPES_DOMAIN |
| @item gdb.SYMBOL_TYPES_DOMAIN |
| This domain contains all types. |
| @end table |
| |
| The available address class categories in @code{gdb.Symbol} are represented |
| as constants in the @code{gdb} module: |
| |
| @table @code |
| @findex SYMBOL_LOC_UNDEF |
| @findex gdb.SYMBOL_LOC_UNDEF |
| @item gdb.SYMBOL_LOC_UNDEF |
| If this is returned by address class, it indicates an error either in |
| the symbol information or in @value{GDBN}'s handling of symbols. |
| @findex SYMBOL_LOC_CONST |
| @findex gdb.SYMBOL_LOC_CONST |
| @item gdb.SYMBOL_LOC_CONST |
| Value is constant int. |
| @findex SYMBOL_LOC_STATIC |
| @findex gdb.SYMBOL_LOC_STATIC |
| @item gdb.SYMBOL_LOC_STATIC |
| Value is at a fixed address. |
| @findex SYMBOL_LOC_REGISTER |
| @findex gdb.SYMBOL_LOC_REGISTER |
| @item gdb.SYMBOL_LOC_REGISTER |
| Value is in a register. |
| @findex SYMBOL_LOC_ARG |
| @findex gdb.SYMBOL_LOC_ARG |
| @item gdb.SYMBOL_LOC_ARG |
| Value is an argument. This value is at the offset stored within the |
| symbol inside the frame's argument list. |
| @findex SYMBOL_LOC_REF_ARG |
| @findex gdb.SYMBOL_LOC_REF_ARG |
| @item gdb.SYMBOL_LOC_REF_ARG |
| Value address is stored in the frame's argument list. Just like |
| @code{LOC_ARG} except that the value's address is stored at the |
| offset, not the value itself. |
| @findex SYMBOL_LOC_REGPARM_ADDR |
| @findex gdb.SYMBOL_LOC_REGPARM_ADDR |
| @item gdb.SYMBOL_LOC_REGPARM_ADDR |
| Value is a specified register. Just like @code{LOC_REGISTER} except |
| the register holds the address of the argument instead of the argument |
| itself. |
| @findex SYMBOL_LOC_LOCAL |
| @findex gdb.SYMBOL_LOC_LOCAL |
| @item gdb.SYMBOL_LOC_LOCAL |
| Value is a local variable. |
| @findex SYMBOL_LOC_TYPEDEF |
| @findex gdb.SYMBOL_LOC_TYPEDEF |
| @item gdb.SYMBOL_LOC_TYPEDEF |
| Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all |
| have this class. |
| @findex SYMBOL_LOC_BLOCK |
| @findex gdb.SYMBOL_LOC_BLOCK |
| @item gdb.SYMBOL_LOC_BLOCK |
| Value is a block. |
| @findex SYMBOL_LOC_CONST_BYTES |
| @findex gdb.SYMBOL_LOC_CONST_BYTES |
| @item gdb.SYMBOL_LOC_CONST_BYTES |
| Value is a byte-sequence. |
| @findex SYMBOL_LOC_UNRESOLVED |
| @findex gdb.SYMBOL_LOC_UNRESOLVED |
| @item gdb.SYMBOL_LOC_UNRESOLVED |
| Value is at a fixed address, but the address of the variable has to be |
| determined from the minimal symbol table whenever the variable is |
| referenced. |
| @findex SYMBOL_LOC_OPTIMIZED_OUT |
| @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT |
| @item gdb.SYMBOL_LOC_OPTIMIZED_OUT |
| The value does not actually exist in the program. |
| @findex SYMBOL_LOC_COMPUTED |
| @findex gdb.SYMBOL_LOC_COMPUTED |
| @item gdb.SYMBOL_LOC_COMPUTED |
| The value's address is a computed location. |
| @end table |
| |
| @node Symbol Tables In Python |
| @subsubsection Symbol table representation in Python. |
| |
| @cindex symbol tables in python |
| @tindex gdb.Symtab |
| @tindex gdb.Symtab_and_line |
| |
| Access to symbol table data maintained by @value{GDBN} on the inferior |
| is exposed to Python via two objects: @code{gdb.Symtab_and_line} and |
| @code{gdb.Symtab}. Symbol table and line data for a frame is returned |
| from the @code{find_sal} method in @code{gdb.Frame} object. |
| @xref{Frames In Python}. |
| |
| For more information on @value{GDBN}'s symbol table management, see |
| @ref{Symbols, ,Examining the Symbol Table}, for more information. |
| |
| A @code{gdb.Symtab_and_line} object has the following attributes: |
| |
| @table @code |
| @defvar Symtab_and_line.symtab |
| The symbol table object (@code{gdb.Symtab}) for this frame. |
| This attribute is not writable. |
| @end defvar |
| |
| @defvar Symtab_and_line.pc |
| Indicates the start of the address range occupied by code for the |
| current source line. This attribute is not writable. |
| @end defvar |
| |
| @defvar Symtab_and_line.last |
| Indicates the end of the address range occupied by code for the current |
| source line. This attribute is not writable. |
| @end defvar |
| |
| @defvar Symtab_and_line.line |
| Indicates the current line number for this object. This |
| attribute is not writable. |
| @end defvar |
| @end table |
| |
| A @code{gdb.Symtab_and_line} object has the following methods: |
| |
| @table @code |
| @defun Symtab_and_line.is_valid () |
| Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid, |
| @code{False} if not. A @code{gdb.Symtab_and_line} object can become |
| invalid if the Symbol table and line object it refers to does not |
| exist in @value{GDBN} any longer. All other |
| @code{gdb.Symtab_and_line} methods will throw an exception if it is |
| invalid at the time the method is called. |
| @end defun |
| @end table |
| |
| A @code{gdb.Symtab} object has the following attributes: |
| |
| @table @code |
| @defvar Symtab.filename |
| The symbol table's source filename. This attribute is not writable. |
| @end defvar |
| |
| @defvar Symtab.objfile |
| The symbol table's backing object file. @xref{Objfiles In Python}. |
| This attribute is not writable. |
| @end defvar |
| @end table |
| |
| A @code{gdb.Symtab} object has the following methods: |
| |
| @table @code |
| @defun Symtab.is_valid () |
| Returns @code{True} if the @code{gdb.Symtab} object is valid, |
| @code{False} if not. A @code{gdb.Symtab} object can become invalid if |
| the symbol table it refers to does not exist in @value{GDBN} any |
| longer. All other @code{gdb.Symtab} methods will throw an exception |
| if it is invalid at the time the method is called. |
| @end defun |
| |
| @defun Symtab.fullname () |
| Return the symbol table's source absolute file name. |
| @end defun |
| |
| @defun Symtab.global_block () |
| Return the global block of the underlying symbol table. |
| @xref{Blocks In Python}. |
| @end defun |
| |
| @defun Symtab.static_block () |
| Return the static block of the underlying symbol table. |
| @xref{Blocks In Python}. |
| @end defun |
| @end table |
| |
| @node Breakpoints In Python |
| @subsubsection Manipulating breakpoints using Python |
| |
| @cindex breakpoints in python |
| @tindex gdb.Breakpoint |
| |
| Python code can manipulate breakpoints via the @code{gdb.Breakpoint} |
| class. |
| |
| @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]}) |
| Create a new breakpoint. @var{spec} is a string naming the |
| location of the breakpoint, or an expression that defines a |
| watchpoint. The contents can be any location recognized by the |
| @code{break} command, or in the case of a watchpoint, by the @code{watch} |
| command. The optional @var{type} denotes the breakpoint to create |
| from the types defined later in this chapter. This argument can be |
| either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type} |
| defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument |
| allows the breakpoint to become invisible to the user. The breakpoint |
| will neither be reported when created, nor will it be listed in the |
| output from @code{info breakpoints} (but will be listed with the |
| @code{maint info breakpoints} command). The optional @var{wp_class} |
| argument defines the class of watchpoint to create, if @var{type} is |
| @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is |
| assumed to be a @code{gdb.WP_WRITE} class. |
| @end defun |
| |
| @defun Breakpoint.stop (self) |
| The @code{gdb.Breakpoint} class can be sub-classed and, in |
| particular, you may choose to implement the @code{stop} method. |
| If this method is defined as a sub-class of @code{gdb.Breakpoint}, |
| it will be called when the inferior reaches any location of a |
| breakpoint which instantiates that sub-class. If the method returns |
| @code{True}, the inferior will be stopped at the location of the |
| breakpoint, otherwise the inferior will continue. |
| |
| If there are multiple breakpoints at the same location with a |
| @code{stop} method, each one will be called regardless of the |
| return status of the previous. This ensures that all @code{stop} |
| methods have a chance to execute at that location. In this scenario |
| if one of the methods returns @code{True} but the others return |
| @code{False}, the inferior will still be stopped. |
| |
| You should not alter the execution state of the inferior (i.e.@:, step, |
| next, etc.), alter the current frame context (i.e.@:, change the current |
| active frame), or alter, add or delete any breakpoint. As a general |
| rule, you should not alter any data within @value{GDBN} or the inferior |
| at this time. |
| |
| Example @code{stop} implementation: |
| |
| @smallexample |
| class MyBreakpoint (gdb.Breakpoint): |
| def stop (self): |
| inf_val = gdb.parse_and_eval("foo") |
| if inf_val == 3: |
| return True |
| return False |
| @end smallexample |
| @end defun |
| |
| The available watchpoint types represented by constants are defined in the |
| @code{gdb} module: |
| |
| @table @code |
| @findex WP_READ |
| @findex gdb.WP_READ |
| @item gdb.WP_READ |
| Read only watchpoint. |
| |
| @findex WP_WRITE |
| @findex gdb.WP_WRITE |
| @item gdb.WP_WRITE |
| Write only watchpoint. |
| |
| @findex WP_ACCESS |
| @findex gdb.WP_ACCESS |
| @item gdb.WP_ACCESS |
| Read/Write watchpoint. |
| @end table |
| |
| @defun Breakpoint.is_valid () |
| Return @code{True} if this @code{Breakpoint} object is valid, |
| @code{False} otherwise. A @code{Breakpoint} object can become invalid |
| if the user deletes the breakpoint. In this case, the object still |
| exists, but the underlying breakpoint does not. In the cases of |
| watchpoint scope, the watchpoint remains valid even if execution of the |
| inferior leaves the scope of that watchpoint. |
| @end defun |
| |
| @defun Breakpoint.delete |
| Permanently deletes the @value{GDBN} breakpoint. This also |
| invalidates the Python @code{Breakpoint} object. Any further access |
| to this object's attributes or methods will raise an error. |
| @end defun |
| |
| @defvar Breakpoint.enabled |
| This attribute is @code{True} if the breakpoint is enabled, and |
| @code{False} otherwise. This attribute is writable. |
| @end defvar |
| |
| @defvar Breakpoint.silent |
| This attribute is @code{True} if the breakpoint is silent, and |
| @code{False} otherwise. This attribute is writable. |
| |
| Note that a breakpoint can also be silent if it has commands and the |
| first command is @code{silent}. This is not reported by the |
| @code{silent} attribute. |
| @end defvar |
| |
| @defvar Breakpoint.thread |
| If the breakpoint is thread-specific, this attribute holds the thread |
| id. If the breakpoint is not thread-specific, this attribute is |
| @code{None}. This attribute is writable. |
| @end defvar |
| |
| @defvar Breakpoint.task |
| If the breakpoint is Ada task-specific, this attribute holds the Ada task |
| id. If the breakpoint is not task-specific (or the underlying |
| language is not Ada), this attribute is @code{None}. This attribute |
| is writable. |
| @end defvar |
| |
| @defvar Breakpoint.ignore_count |
| This attribute holds the ignore count for the breakpoint, an integer. |
| This attribute is writable. |
| @end defvar |
| |
| @defvar Breakpoint.number |
| This attribute holds the breakpoint's number --- the identifier used by |
| the user to manipulate the breakpoint. This attribute is not writable. |
| @end defvar |
| |
| @defvar Breakpoint.type |
| This attribute holds the breakpoint's type --- the identifier used to |
| determine the actual breakpoint type or use-case. This attribute is not |
| writable. |
| @end defvar |
| |
| @defvar Breakpoint.visible |
| This attribute tells whether the breakpoint is visible to the user |
| when set, or when the @samp{info breakpoints} command is run. This |
| attribute is not writable. |
| @end defvar |
| |
| The available types are represented by constants defined in the @code{gdb} |
| module: |
| |
| @table @code |
| @findex BP_BREAKPOINT |
| @findex gdb.BP_BREAKPOINT |
| @item gdb.BP_BREAKPOINT |
| Normal code breakpoint. |
| |
| @findex BP_WATCHPOINT |
| @findex gdb.BP_WATCHPOINT |
| @item gdb.BP_WATCHPOINT |
| Watchpoint breakpoint. |
| |
| @findex BP_HARDWARE_WATCHPOINT |
| @findex gdb.BP_HARDWARE_WATCHPOINT |
| @item gdb.BP_HARDWARE_WATCHPOINT |
| Hardware assisted watchpoint. |
| |
| @findex BP_READ_WATCHPOINT |
| @findex gdb.BP_READ_WATCHPOINT |
| @item gdb.BP_READ_WATCHPOINT |
| Hardware assisted read watchpoint. |
| |
| @findex BP_ACCESS_WATCHPOINT |
| @findex gdb.BP_ACCESS_WATCHPOINT |
| @item gdb.BP_ACCESS_WATCHPOINT |
| Hardware assisted access watchpoint. |
| @end table |
| |
| @defvar Breakpoint.hit_count |
| This attribute holds the hit count for the breakpoint, an integer. |
| This attribute is writable, but currently it can only be set to zero. |
| @end defvar |
| |
| @defvar Breakpoint.location |
| This attribute holds the location of the breakpoint, as specified by |
| the user. It is a string. If the breakpoint does not have a location |
| (that is, it is a watchpoint) the attribute's value is @code{None}. This |
| attribute is not writable. |
| @end defvar |
| |
| @defvar Breakpoint.expression |
| This attribute holds a breakpoint expression, as specified by |
| the user. It is a string. If the breakpoint does not have an |
| expression (the breakpoint is not a watchpoint) the attribute's value |
| is @code{None}. This attribute is not writable. |
| @end defvar |
| |
| @defvar Breakpoint.condition |
| This attribute holds the condition of the breakpoint, as specified by |
| the user. It is a string. If there is no condition, this attribute's |
| value is @code{None}. This attribute is writable. |
| @end defvar |
| |
| @defvar Breakpoint.commands |
| This attribute holds the commands attached to the breakpoint. If |
| there are commands, this attribute's value is a string holding all the |
| commands, separated by newlines. If there are no commands, this |
| attribute is @code{None}. This attribute is not writable. |
| @end defvar |
| |
| @node Finish Breakpoints in Python |
| @subsubsection Finish Breakpoints |
| |
| @cindex python finish breakpoints |
| @tindex gdb.FinishBreakpoint |
| |
| A finish breakpoint is a temporary breakpoint set at the return address of |
| a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint} |
| extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled |
| and deleted when the execution will run out of the breakpoint scope (i.e.@: |
| @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered). |
| Finish breakpoints are thread specific and must be create with the right |
| thread selected. |
| |
| @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]}) |
| Create a finish breakpoint at the return address of the @code{gdb.Frame} |
| object @var{frame}. If @var{frame} is not provided, this defaults to the |
| newest frame. The optional @var{internal} argument allows the breakpoint to |
| become invisible to the user. @xref{Breakpoints In Python}, for further |
| details about this argument. |
| @end defun |
| |
| @defun FinishBreakpoint.out_of_scope (self) |
| In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN} |
| @code{return} command, @dots{}), a function may not properly terminate, and |
| thus never hit the finish breakpoint. When @value{GDBN} notices such a |
| situation, the @code{out_of_scope} callback will be triggered. |
| |
| You may want to sub-class @code{gdb.FinishBreakpoint} and override this |
| method: |
| |
| @smallexample |
| class MyFinishBreakpoint (gdb.FinishBreakpoint) |
| def stop (self): |
| print "normal finish" |
| return True |
| |
| def out_of_scope (): |
| print "abnormal finish" |
| @end smallexample |
| @end defun |
| |
| @defvar FinishBreakpoint.return_value |
| When @value{GDBN} is stopped at a finish breakpoint and the frame |
| used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this |
| attribute will contain a @code{gdb.Value} object corresponding to the return |
| value of the function. The value will be @code{None} if the function return |
| type is @code{void} or if the return value was not computable. This attribute |
| is not writable. |
| @end defvar |
| |
| @node Lazy Strings In Python |
| @subsubsection Python representation of lazy strings. |
| |
| @cindex lazy strings in python |
| @tindex gdb.LazyString |
| |
| A @dfn{lazy string} is a string whose contents is not retrieved or |
| encoded until it is needed. |
| |
| A @code{gdb.LazyString} is represented in @value{GDBN} as an |
| @code{address} that points to a region of memory, an @code{encoding} |
| that will be used to encode that region of memory, and a @code{length} |
| to delimit the region of memory that represents the string. The |
| difference between a @code{gdb.LazyString} and a string wrapped within |
| a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated |
| differently by @value{GDBN} when printing. A @code{gdb.LazyString} is |
| retrieved and encoded during printing, while a @code{gdb.Value} |
| wrapping a string is immediately retrieved and encoded on creation. |
| |
| A @code{gdb.LazyString} object has the following functions: |
| |
| @defun LazyString.value () |
| Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value |
| will point to the string in memory, but will lose all the delayed |
| retrieval, encoding and handling that @value{GDBN} applies to a |
| @code{gdb.LazyString}. |
| @end defun |
| |
| @defvar LazyString.address |
| This attribute holds the address of the string. This attribute is not |
| writable. |
| @end defvar |
| |
| @defvar LazyString.length |
| This attribute holds the length of the string in characters. If the |
| length is -1, then the string will be fetched and encoded up to the |
| first null of appropriate width. This attribute is not writable. |
| @end defvar |
| |
| @defvar LazyString.encoding |
| This attribute holds the encoding that will be applied to the string |
| when the string is printed by @value{GDBN}. If the encoding is not |
| set, or contains an empty string, then @value{GDBN} will select the |
| most appropriate encoding when the string is printed. This attribute |
| is not writable. |
| @end defvar |
| |
| @defvar LazyString.type |
| This attribute holds the type that is represented by the lazy string's |
| type. For a lazy string this will always be a pointer type. To |
| resolve this to the lazy string's character type, use the type's |
| @code{target} method. @xref{Types In Python}. This attribute is not |
| writable. |
| @end defvar |
| |
| @node Python Auto-loading |
| @subsection Python Auto-loading |
| @cindex Python auto-loading |
| |
| When a new object file is read (for example, due to the @code{file} |
| command, or because the inferior has loaded a shared library), |
| @value{GDBN} will look for Python support scripts in several ways: |
| @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file}) |
| and @code{.debug_gdb_scripts} section |
| (@pxref{dotdebug_gdb_scripts section}). |
| |
| The auto-loading feature is useful for supplying application-specific |
| debugging commands and scripts. |
| |
| Auto-loading can be enabled or disabled, |
| and the list of auto-loaded scripts can be printed. |
| |
| @table @code |
| @anchor{set auto-load python-scripts} |
| @kindex set auto-load python-scripts |
| @item set auto-load python-scripts [on|off] |
| Enable or disable the auto-loading of Python scripts. |
| |
| @anchor{show auto-load python-scripts} |
| @kindex show auto-load python-scripts |
| @item show auto-load python-scripts |
| Show whether auto-loading of Python scripts is enabled or disabled. |
| |
| @anchor{info auto-load python-scripts} |
| @kindex info auto-load python-scripts |
| @cindex print list of auto-loaded Python scripts |
| @item info auto-load python-scripts [@var{regexp}] |
| Print the list of all Python scripts that @value{GDBN} auto-loaded. |
| |
| Also printed is the list of Python scripts that were mentioned in |
| the @code{.debug_gdb_scripts} section and were not found |
| (@pxref{dotdebug_gdb_scripts section}). |
| This is useful because their names are not printed when @value{GDBN} |
| tries to load them and fails. There may be many of them, and printing |
| an error message for each one is problematic. |
| |
| If @var{regexp} is supplied only Python scripts with matching names are printed. |
| |
| Example: |
| |
| @smallexample |
| (gdb) info auto-load python-scripts |
| Loaded Script |
| Yes py-section-script.py |
| full name: /tmp/py-section-script.py |
| No my-foo-pretty-printers.py |
| @end smallexample |
| @end table |
| |
| When reading an auto-loaded file, @value{GDBN} sets the |
| @dfn{current objfile}. This is available via the @code{gdb.current_objfile} |
| function (@pxref{Objfiles In Python}). This can be useful for |
| registering objfile-specific pretty-printers. |
| |
| @menu |
| * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file |
| * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section |
| * Which flavor to choose?:: |
| @end menu |
| |
| @node objfile-gdb.py file |
| @subsubsection The @file{@var{objfile}-gdb.py} file |
| @cindex @file{@var{objfile}-gdb.py} |
| |
| When a new object file is read, @value{GDBN} looks for |
| a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below), |
| where @var{objfile} is the object file's real name, formed by ensuring |
| that the file name is absolute, following all symlinks, and resolving |
| @code{.} and @code{..} components. If this file exists and is |
| readable, @value{GDBN} will evaluate it as a Python script. |
| |
| If this file does not exist, then @value{GDBN} will look for |
| @var{script-name} file in all of the directories as specified below. |
| |
| Note that loading of this script file also requires accordingly configured |
| @code{auto-load safe-path} (@pxref{Auto-loading safe path}). |
| |
| @table @code |
| @anchor{set auto-load scripts-directory} |
| @kindex set auto-load scripts-directory |
| @item set auto-load scripts-directory @r{[}@var{directories}@r{]} |
| Control @value{GDBN} auto-loaded scripts location. Multiple directory entries |
| may be delimited by the host platform path separator in use |
| (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS). |
| |
| Each entry here needs to be covered also by the security setting |
| @code{set auto-load safe-path} (@pxref{set auto-load safe-path}). |
| |
| @anchor{with-auto-load-dir} |
| This variable defaults to @file{$debugdir:$datadir/auto-load}. The default |
| @code{set auto-load safe-path} value can be also overriden by @value{GDBN} |
| configuration option @option{--with-auto-load-dir}. |
| |
| Any reference to @file{$debugdir} will get replaced by |
| @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any |
| reference to @file{$datadir} will get replaced by @var{data-directory} which is |
| determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and |
| @file{$datadir} must be placed as a directory component --- either alone or |
| delimited by @file{/} or @file{\} directory separators, depending on the host |
| platform. |
| |
| The list of directories uses path separator (@samp{:} on GNU and Unix |
| systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly |
| to the @env{PATH} environment variable. |
| |
| @anchor{show auto-load scripts-directory} |
| @kindex show auto-load scripts-directory |
| @item show auto-load scripts-directory |
| Show @value{GDBN} auto-loaded scripts location. |
| @end table |
| |
| @value{GDBN} does not track which files it has already auto-loaded this way. |
| @value{GDBN} will load the associated script every time the corresponding |
| @var{objfile} is opened. |
| So your @file{-gdb.py} file should be careful to avoid errors if it |
| is evaluated more than once. |
| |
| @node dotdebug_gdb_scripts section |
| @subsubsection The @code{.debug_gdb_scripts} section |
| @cindex @code{.debug_gdb_scripts} section |
| |
| For systems using file formats like ELF and COFF, |
| when @value{GDBN} loads a new object file |
| it will look for a special section named @samp{.debug_gdb_scripts}. |
| If this section exists, its contents is a list of names of scripts to load. |
| |
| @value{GDBN} will look for each specified script file first in the |
| current directory and then along the source search path |
| (@pxref{Source Path, ,Specifying Source Directories}), |
| except that @file{$cdir} is not searched, since the compilation |
| directory is not relevant to scripts. |
| |
| Entries can be placed in section @code{.debug_gdb_scripts} with, |
| for example, this GCC macro: |
| |
| @example |
| /* Note: The "MS" section flags are to remove duplicates. */ |
| #define DEFINE_GDB_SCRIPT(script_name) \ |
| asm("\ |
| .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\ |
| .byte 1\n\ |
| .asciz \"" script_name "\"\n\ |
| .popsection \n\ |
| "); |
| @end example |
| |
| @noindent |
| Then one can reference the macro in a header or source file like this: |
| |
| @example |
| DEFINE_GDB_SCRIPT ("my-app-scripts.py") |
| @end example |
| |
| The script name may include directories if desired. |
| |
| Note that loading of this script file also requires accordingly configured |
| @code{auto-load safe-path} (@pxref{Auto-loading safe path}). |
| |
| If the macro is put in a header, any application or library |
| using this header will get a reference to the specified script. |
| |
| @node Which flavor to choose? |
| @subsubsection Which flavor to choose? |
| |
| Given the multiple ways of auto-loading Python scripts, it might not always |
| be clear which one to choose. This section provides some guidance. |
| |
| Benefits of the @file{-gdb.py} way: |
| |
| @itemize @bullet |
| @item |
| Can be used with file formats that don't support multiple sections. |
| |
| @item |
| Ease of finding scripts for public libraries. |
| |
| Scripts specified in the @code{.debug_gdb_scripts} section are searched for |
| in the source search path. |
| For publicly installed libraries, e.g., @file{libstdc++}, there typically |
| isn't a source directory in which to find the script. |
| |
| @item |
| Doesn't require source code additions. |
| @end itemize |
| |
| Benefits of the @code{.debug_gdb_scripts} way: |
| |
| @itemize @bullet |
| @item |
| Works with static linking. |
| |
| Scripts for libraries done the @file{-gdb.py} way require an objfile to |
| trigger their loading. When an application is statically linked the only |
| objfile available is the executable, and it is cumbersome to attach all the |
| scripts from all the input libraries to the executable's @file{-gdb.py} script. |
| |
| @item |
| Works with classes that are entirely inlined. |
| |
| Some classes can be entirely inlined, and thus there may not be an associated |
| shared library to attach a @file{-gdb.py} script to. |
| |
| @item |
| Scripts needn't be copied out of the source tree. |
| |
| In some circumstances, apps can be built out of large collections of internal |
| libraries, and the build infrastructure necessary to install the |
| @file{-gdb.py} scripts in a place where @value{GDBN} can find them is |
| cumbersome. It may be easier to specify the scripts in the |
| @code{.debug_gdb_scripts} section as relative paths, and add a path to the |
| top of the source tree to the source search path. |
| @end itemize |
| |
| @node Python modules |
| @subsection Python modules |
| @cindex python modules |
| |
| @value{GDBN} comes with several modules to assist writing Python code. |
| |
| @menu |
| * gdb.printing:: Building and registering pretty-printers. |
| * gdb.types:: Utilities for working with types. |
| * gdb.prompt:: Utilities for prompt value substitution. |
| @end menu |
| |
| @node gdb.printing |
| @subsubsection gdb.printing |
| @cindex gdb.printing |
| |
| This module provides a collection of utilities for working with |
| pretty-printers. |
| |
| @table @code |
| @item PrettyPrinter (@var{name}, @var{subprinters}=None) |
| This class specifies the API that makes @samp{info pretty-printer}, |
| @samp{enable pretty-printer} and @samp{disable pretty-printer} work. |
| Pretty-printers should generally inherit from this class. |
| |
| @item SubPrettyPrinter (@var{name}) |
| For printers that handle multiple types, this class specifies the |
| corresponding API for the subprinters. |
| |
| @item RegexpCollectionPrettyPrinter (@var{name}) |
| Utility class for handling multiple printers, all recognized via |
| regular expressions. |
| @xref{Writing a Pretty-Printer}, for an example. |
| |
| @item FlagEnumerationPrinter (@var{name}) |
| A pretty-printer which handles printing of @code{enum} values. Unlike |
| @value{GDBN}'s built-in @code{enum} printing, this printer attempts to |
| work properly when there is some overlap between the enumeration |
| constants. @var{name} is the name of the printer and also the name of |
| the @code{enum} type to look up. |
| |
| @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False) |
| Register @var{printer} with the pretty-printer list of @var{obj}. |
| If @var{replace} is @code{True} then any existing copy of the printer |
| is replaced. Otherwise a @code{RuntimeError} exception is raised |
| if a printer with the same name already exists. |
| @end table |
| |
| @node gdb.types |
| @subsubsection gdb.types |
| @cindex gdb.types |
| |
| This module provides a collection of utilities for working with |
| @code{gdb.Types} objects. |
| |
| @table @code |
| @item get_basic_type (@var{type}) |
| Return @var{type} with const and volatile qualifiers stripped, |
| and with typedefs and C@t{++} references converted to the underlying type. |
| |
| C@t{++} example: |
| |
| @smallexample |
| typedef const int const_int; |
| const_int foo (3); |
| const_int& foo_ref (foo); |
| int main () @{ return 0; @} |
| @end smallexample |
| |
| Then in gdb: |
| |
| @smallexample |
| (gdb) start |
| (gdb) python import gdb.types |
| (gdb) python foo_ref = gdb.parse_and_eval("foo_ref") |
| (gdb) python print gdb.types.get_basic_type(foo_ref.type) |
| int |
| @end smallexample |
| |
| @item has_field (@var{type}, @var{field}) |
| Return @code{True} if @var{type}, assumed to be a type with fields |
| (e.g., a structure or union), has field @var{field}. |
| |
| @item make_enum_dict (@var{enum_type}) |
| Return a Python @code{dictionary} type produced from @var{enum_type}. |
| |
| @item deep_items (@var{type}) |
| Returns a Python iterator similar to the standard |
| @code{gdb.Type.iteritems} method, except that the iterator returned |
| by @code{deep_items} will recursively traverse anonymous struct or |
| union fields. For example: |
| |
| @smallexample |
| struct A |
| @{ |
| int a; |
| union @{ |
| int b0; |
| int b1; |
| @}; |
| @}; |
| @end smallexample |
| |
| @noindent |
| Then in @value{GDBN}: |
| @smallexample |
| (@value{GDBP}) python import gdb.types |
| (@value{GDBP}) python struct_a = gdb.lookup_type("struct A") |
| (@value{GDBP}) python print struct_a.keys () |
| @{['a', '']@} |
| (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)] |
| @{['a', 'b0', 'b1']@} |
| @end smallexample |
| |
| @end table |
| |
| @node gdb.prompt |
| @subsubsection gdb.prompt |
| @cindex gdb.prompt |
| |
| This module provides a method for prompt value-substitution. |
| |
| @table @code |
| @item substitute_prompt (@var{string}) |
| Return @var{string} with escape sequences substituted by values. Some |
| escape sequences take arguments. You can specify arguments inside |
| ``@{@}'' immediately following the escape sequence. |
| |
| The escape sequences you can pass to this function are: |
| |
| @table @code |
| @item \\ |
| Substitute a backslash. |
| @item \e |
| Substitute an ESC character. |
| @item \f |
| Substitute the selected frame; an argument names a frame parameter. |
| @item \n |
| Substitute a newline. |
| @item \p |
| Substitute a parameter's value; the argument names the parameter. |
| @item \r |
| Substitute a carriage return. |
| @item \t |
| Substitute the selected thread; an argument names a thread parameter. |
| @item \v |
| Substitute the version of GDB. |
| @item \w |
| Substitute the current working directory. |
| @item \[ |
| Begin a sequence of non-printing characters. These sequences are |
| typically used with the ESC character, and are not counted in the string |
| length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a |
| blue-colored ``(gdb)'' prompt where the length is five. |
| @item \] |
| End a sequence of non-printing characters. |
| @end table |
| |
| For example: |
| |
| @smallexample |
| substitute_prompt (``frame: \f, |
| print arguments: \p@{print frame-arguments@}'') |
| @end smallexample |
| |
| @exdent will return the string: |
| |
| @smallexample |
| "frame: main, print arguments: scalars" |
| @end smallexample |
| @end table |
| |
| @node Aliases |
| @section Creating new spellings of existing commands |
| @cindex aliases for commands |
| |
| It is often useful to define alternate spellings of existing commands. |
| For example, if a new @value{GDBN} command defined in Python has |
| a long name to type, it is handy to have an abbreviated version of it |
| that involves less typing. |
| |
| @value{GDBN} itself uses aliases. For example @samp{s} is an alias |
| of the @samp{step} command even though it is otherwise an ambiguous |
| abbreviation of other commands like @samp{set} and @samp{show}. |
| |
| Aliases are also used to provide shortened or more common versions |
| of multi-word commands. For example, @value{GDBN} provides the |
| @samp{tty} alias of the @samp{set inferior-tty} command. |
| |
| You can define a new alias with the @samp{alias} command. |
| |
| @table @code |
| |
| @kindex alias |
| @item alias [-a] [--] @var{ALIAS} = @var{COMMAND} |
| |
| @end table |
| |
| @var{ALIAS} specifies the name of the new alias. |
| Each word of @var{ALIAS} must consist of letters, numbers, dashes and |
| underscores. |
| |
| @var{COMMAND} specifies the name of an existing command |
| that is being aliased. |
| |
| The @samp{-a} option specifies that the new alias is an abbreviation |
| of the command. Abbreviations are not shown in command |
| lists displayed by the @samp{help} command. |
| |
| The @samp{--} option specifies the end of options, |
| and is useful when @var{ALIAS} begins with a dash. |
| |
| Here is a simple example showing how to make an abbreviation |
| of a command so that there is less to type. |
| Suppose you were tired of typing @samp{disas}, the current |
| shortest unambiguous abbreviation of the @samp{disassemble} command |
| and you wanted an even shorter version named @samp{di}. |
| The following will accomplish this. |
| |
| @smallexample |
| (gdb) alias -a di = disas |
| @end smallexample |
| |
| Note that aliases are different from user-defined commands. |
| With a user-defined command, you also need to write documentation |
| for it with the @samp{document} command. |
| An alias automatically picks up the documentation of the existing command. |
| |
| Here is an example where we make @samp{elms} an abbreviation of |
| @samp{elements} in the @samp{set print elements} command. |
| This is to show that you can make an abbreviation of any part |
| of a command. |
| |
| @smallexample |
| (gdb) alias -a set print elms = set print elements |
| (gdb) alias -a show print elms = show print elements |
| (gdb) set p elms 20 |
| (gdb) show p elms |
| Limit on string chars or array elements to print is 200. |
| @end smallexample |
| |
| Note that if you are defining an alias of a @samp{set} command, |
| and you want to have an alias for the corresponding @samp{show} |
| command, then you need to define the latter separately. |
| |
| Unambiguously abbreviated commands are allowed in @var{COMMAND} and |
| @var{ALIAS}, just as they are normally. |
| |
| @smallexample |
| (gdb) alias -a set pr elms = set p ele |
| @end smallexample |
| |
| Finally, here is an example showing the creation of a one word |
| alias for a more complex command. |
| This creates alias @samp{spe} of the command @samp{set print elements}. |
| |
| @smallexample |
| (gdb) alias spe = set print elements |
| (gdb) spe 20 |
| @end smallexample |
| |
| @node Interpreters |
| @chapter Command Interpreters |
| @cindex command interpreters |
| |
| @value{GDBN} supports multiple command interpreters, and some command |
| infrastructure to allow users or user interface writers to switch |
| between interpreters or run commands in other interpreters. |
| |
| @value{GDBN} currently supports two command interpreters, the console |
| interpreter (sometimes called the command-line interpreter or @sc{cli}) |
| and the machine interface interpreter (or @sc{gdb/mi}). This manual |
| describes both of these interfaces in great detail. |
| |
| By default, @value{GDBN} will start with the console interpreter. |
| However, the user may choose to start @value{GDBN} with another |
| interpreter by specifying the @option{-i} or @option{--interpreter} |
| startup options. Defined interpreters include: |
| |
| @table @code |
| @item console |
| @cindex console interpreter |
| The traditional console or command-line interpreter. This is the most often |
| used interpreter with @value{GDBN}. With no interpreter specified at runtime, |
| @value{GDBN} will use this interpreter. |
| |
| @item mi |
| @cindex mi interpreter |
| The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily |
| by programs wishing to use @value{GDBN} as a backend for a debugger GUI |
| or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi} |
| Interface}. |
| |
| @item mi2 |
| @cindex mi2 interpreter |
| The current @sc{gdb/mi} interface. |
| |
| @item mi1 |
| @cindex mi1 interpreter |
| The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3. |
| |
| @end table |
| |
| @cindex invoke another interpreter |
| The interpreter being used by @value{GDBN} may not be dynamically |
| switched at runtime. Although possible, this could lead to a very |
| precarious situation. Consider an IDE using @sc{gdb/mi}. If a user |
| enters the command "interpreter-set console" in a console view, |
| @value{GDBN} would switch to using the console interpreter, rendering |
| the IDE inoperable! |
| |
| @kindex interpreter-exec |
| Although you may only choose a single interpreter at startup, you may execute |
| commands in any interpreter from the current interpreter using the appropriate |
| command. If you are running the console interpreter, simply use the |
| @code{interpreter-exec} command: |
| |
| @smallexample |
| interpreter-exec mi "-data-list-register-names" |
| @end smallexample |
| |
| @sc{gdb/mi} has a similar command, although it is only available in versions of |
| @value{GDBN} which support @sc{gdb/mi} version 2 (or greater). |
| |
| @node TUI |
| @chapter @value{GDBN} Text User Interface |
| @cindex TUI |
| @cindex Text User Interface |
| |
| @menu |
| * TUI Overview:: TUI overview |
| * TUI Keys:: TUI key bindings |
| * TUI Single Key Mode:: TUI single key mode |
| * TUI Commands:: TUI-specific commands |
| * TUI Configuration:: TUI configuration variables |
| @end menu |
| |
| The @value{GDBN} Text User Interface (TUI) is a terminal |
| interface which uses the @code{curses} library to show the source |
| file, the assembly output, the program registers and @value{GDBN} |
| commands in separate text windows. The TUI mode is supported only |
| on platforms where a suitable version of the @code{curses} library |
| is available. |
| |
| The TUI mode is enabled by default when you invoke @value{GDBN} as |
| @samp{@value{GDBP} -tui}. |
| You can also switch in and out of TUI mode while @value{GDBN} runs by |
| using various TUI commands and key bindings, such as @kbd{C-x C-a}. |
| @xref{TUI Keys, ,TUI Key Bindings}. |
| |
| @node TUI Overview |
| @section TUI Overview |
| |
| In TUI mode, @value{GDBN} can display several text windows: |
| |
| @table @emph |
| @item command |
| This window is the @value{GDBN} command window with the @value{GDBN} |
| prompt and the @value{GDBN} output. The @value{GDBN} input is still |
| managed using readline. |
| |
| @item source |
| The source window shows the source file of the program. The current |
| line and active breakpoints are displayed in this window. |
| |
| @item assembly |
| The assembly window shows the disassembly output of the program. |
| |
| @item register |
| This window shows the processor registers. Registers are highlighted |
| when their values change. |
| @end table |
| |
| The source and assembly windows show the current program position |
| by highlighting the current line and marking it with a @samp{>} marker. |
| Breakpoints are indicated with two markers. The first marker |
| indicates the breakpoint type: |
| |
| @table @code |
| @item B |
| Breakpoint which was hit at least once. |
| |
| @item b |
| Breakpoint which was never hit. |
| |
| @item H |
| Hardware breakpoint which was hit at least once. |
| |
| @item h |
| Hardware breakpoint which was never hit. |
| @end table |
| |
| The second marker indicates whether the breakpoint is enabled or not: |
| |
| @table @code |
| @item + |
| Breakpoint is enabled. |
| |
| @item - |
| Breakpoint is disabled. |
| @end table |
| |
| The source, assembly and register windows are updated when the current |
| thread changes, when the frame changes, or when the program counter |
| changes. |
| |
| These windows are not all visible at the same time. The command |
| window is always visible. The others can be arranged in several |
| layouts: |
| |
| @itemize @bullet |
| @item |
| source only, |
| |
| @item |
| assembly only, |
| |
| @item |
| source and assembly, |
| |
| @item |
| source and registers, or |
| |
| @item |
| assembly and registers. |
| @end itemize |
| |
| A status line above the command window shows the following information: |
| |
| @table @emph |
| @item target |
| Indicates the current @value{GDBN} target. |
| (@pxref{Targets, ,Specifying a Debugging Target}). |
| |
| @item process |
| Gives the current process or thread number. |
| When no process is being debugged, this field is set to @code{No process}. |
| |
| @item function |
| Gives the current function name for the selected frame. |
| The name is demangled if demangling is turned on (@pxref{Print Settings}). |
| When there is no symbol corresponding to the current program counter, |
| the string @code{??} is displayed. |
| |
| @item line |
| Indicates the current line number for the selected frame. |
| When the current line number is not known, the string @code{??} is displayed. |
| |
| @item pc |
| Indicates the current program counter address. |
| @end table |
| |
| @node TUI Keys |
| @section TUI Key Bindings |
| @cindex TUI key bindings |
| |
| The TUI installs several key bindings in the readline keymaps |
| @ifset SYSTEM_READLINE |
| (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}). |
| @end ifset |
| @ifclear SYSTEM_READLINE |
| (@pxref{Command Line Editing}). |
| @end ifclear |
| The following key bindings are installed for both TUI mode and the |
| @value{GDBN} standard mode. |
| |
| @table @kbd |
| @kindex C-x C-a |
| @item C-x C-a |
| @kindex C-x a |
| @itemx C-x a |
| @kindex C-x A |
| @itemx C-x A |
| Enter or leave the TUI mode. When leaving the TUI mode, |
| the curses window management stops and @value{GDBN} operates using |
| its standard mode, writing on the terminal directly. When reentering |
| the TUI mode, control is given back to the curses windows. |
| The screen is then refreshed. |
| |
| @kindex C-x 1 |
| @item C-x 1 |
| Use a TUI layout with only one window. The layout will |
| either be @samp{source} or @samp{assembly}. When the TUI mode |
| is not active, it will switch to the TUI mode. |
| |
| Think of this key binding as the Emacs @kbd{C-x 1} binding. |
| |
| @kindex C-x 2 |
| @item C-x 2 |
| Use a TUI layout with at least two windows. When the current |
| layout already has two windows, the next layout with two windows is used. |
| When a new layout is chosen, one window will always be common to the |
| previous layout and the new one. |
| |
| Think of it as the Emacs @kbd{C-x 2} binding. |
| |
| @kindex C-x o |
| @item C-x o |
| Change the active window. The TUI associates several key bindings |
| (like scrolling and arrow keys) with the active window. This command |
| gives the focus to the next TUI window. |
| |
| Think of it as the Emacs @kbd{C-x o} binding. |
| |
| @kindex C-x s |
| @item C-x s |
| Switch in and out of the TUI SingleKey mode that binds single |
| keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}). |
| @end table |
| |
| The following key bindings only work in the TUI mode: |
| |
| @table @asis |
| @kindex PgUp |
| @item @key{PgUp} |
| Scroll the active window one page up. |
| |
| @kindex PgDn |
| @item @key{PgDn} |
| Scroll the active window one page down. |
| |
| @kindex Up |
| @item @key{Up} |
| Scroll the active window one line up. |
| |
| @kindex Down |
| @item @key{Down} |
| Scroll the active window one line down. |
| |
| @kindex Left |
| @item @key{Left} |
| Scroll the active window one column left. |
| |
| @kindex Right |
| @item @key{Right} |
| Scroll the active window one column right. |
| |
| @kindex C-L |
| @item @kbd{C-L} |
| Refresh the screen. |
| @end table |
| |
| Because the arrow keys scroll the active window in the TUI mode, they |
| are not available for their normal use by readline unless the command |
| window has the focus. When another window is active, you must use |
| other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b} |
| and @kbd{C-f} to control the command window. |
| |
| @node TUI Single Key Mode |
| @section TUI Single Key Mode |
| @cindex TUI single key mode |
| |
| The TUI also provides a @dfn{SingleKey} mode, which binds several |
| frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to |
| switch into this mode, where the following key bindings are used: |
| |
| @table @kbd |
| @kindex c @r{(SingleKey TUI key)} |
| @item c |
| continue |
| |
| @kindex d @r{(SingleKey TUI key)} |
| @item d |
| down |
| |
| @kindex f @r{(SingleKey TUI key)} |
| @item f |
| finish |
| |
| @kindex n @r{(SingleKey TUI key)} |
| @item n |
| next |
| |
| @kindex q @r{(SingleKey TUI key)} |
| @item q |
| exit the SingleKey mode. |
| |
| @kindex r @r{(SingleKey TUI key)} |
| @item r |
| run |
| |
| @kindex s @r{(SingleKey TUI key)} |
| @item s |
| step |
| |
| @kindex u @r{(SingleKey TUI key)} |
| @item u |
| up |
| |
| @kindex v @r{(SingleKey TUI key)} |
| @item v |
| info locals |
| |
| @kindex w @r{(SingleKey TUI key)} |
| @item w |
| where |
| @end table |
| |
| Other keys temporarily switch to the @value{GDBN} command prompt. |
| The key that was pressed is inserted in the editing buffer so that |
| it is possible to type most @value{GDBN} commands without interaction |
| with the TUI SingleKey mode. Once the command is entered the TUI |
| SingleKey mode is restored. The only way to permanently leave |
| this mode is by typing @kbd{q} or @kbd{C-x s}. |
| |
| |
| @node TUI Commands |
| @section TUI-specific Commands |
| @cindex TUI commands |
| |
| The TUI has specific commands to control the text windows. |
| These commands are always available, even when @value{GDBN} is not in |
| the TUI mode. When @value{GDBN} is in the standard mode, most |
| of these commands will automatically switch to the TUI mode. |
| |
| Note that if @value{GDBN}'s @code{stdout} is not connected to a |
| terminal, or @value{GDBN} has been started with the machine interface |
| interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of |
| these commands will fail with an error, because it would not be |
| possible or desirable to enable curses window management. |
| |
| @table @code |
| @item info win |
| @kindex info win |
| List and give the size of all displayed windows. |
| |
| @item layout next |
| @kindex layout |
| Display the next layout. |
| |
| @item layout prev |
| Display the previous layout. |
| |
| @item layout src |
| Display the source window only. |
| |
| @item layout asm |
| Display the assembly window only. |
| |
| @item layout split |
| Display the source and assembly window. |
| |
| @item layout regs |
| Display the register window together with the source or assembly window. |
| |
| @item focus next |
| @kindex focus |
| Make the next window active for scrolling. |
| |
| @item focus prev |
| Make the previous window active for scrolling. |
| |
| @item focus src |
| Make the source window active for scrolling. |
| |
| @item focus asm |
| Make the assembly window active for scrolling. |
| |
| @item focus regs |
| Make the register window active for scrolling. |
| |
| @item focus cmd |
| Make the command window active for scrolling. |
| |
| @item refresh |
| @kindex refresh |
| Refresh the screen. This is similar to typing @kbd{C-L}. |
| |
| @item tui reg float |
| @kindex tui reg |
| Show the floating point registers in the register window. |
| |
| @item tui reg general |
| Show the general registers in the register window. |
| |
| @item tui reg next |
| Show the next register group. The list of register groups as well as |
| their order is target specific. The predefined register groups are the |
| following: @code{general}, @code{float}, @code{system}, @code{vector}, |
| @code{all}, @code{save}, @code{restore}. |
| |
| @item tui reg system |
| Show the system registers in the register window. |
| |
| @item update |
| @kindex update |
| Update the source window and the current execution point. |
| |
| @item winheight @var{name} +@var{count} |
| @itemx winheight @var{name} -@var{count} |
| @kindex winheight |
| Change the height of the window @var{name} by @var{count} |
| lines. Positive counts increase the height, while negative counts |
| decrease it. |
| |
| @item tabset @var{nchars} |
| @kindex tabset |
| Set the width of tab stops to be @var{nchars} characters. |
| @end table |
| |
| @node TUI Configuration |
| @section TUI Configuration Variables |
| @cindex TUI configuration variables |
| |
| Several configuration variables control the appearance of TUI windows. |
| |
| @table @code |
| @item set tui border-kind @var{kind} |
| @kindex set tui border-kind |
| Select the border appearance for the source, assembly and register windows. |
| The possible values are the following: |
| @table @code |
| @item space |
| Use a space character to draw the border. |
| |
| @item ascii |
| Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border. |
| |
| @item acs |
| Use the Alternate Character Set to draw the border. The border is |
| drawn using character line graphics if the terminal supports them. |
| @end table |
| |
| @item set tui border-mode @var{mode} |
| @kindex set tui border-mode |
| @itemx set tui active-border-mode @var{mode} |
| @kindex set tui active-border-mode |
| Select the display attributes for the borders of the inactive windows |
| or the active window. The @var{mode} can be one of the following: |
| @table @code |
| @item normal |
| Use normal attributes to display the border. |
| |
| @item standout |
| Use standout mode. |
| |
| @item reverse |
| Use reverse video mode. |
| |
| @item half |
| Use half bright mode. |
| |
| @item half-standout |
| Use half bright and standout mode. |
| |
| @item bold |
| Use extra bright or bold mode. |
| |
| @item bold-standout |
| Use extra bright or bold and standout mode. |
| @end table |
| @end table |
| |
| @node Emacs |
| @chapter Using @value{GDBN} under @sc{gnu} Emacs |
| |
| @cindex Emacs |
| @cindex @sc{gnu} Emacs |
| A special interface allows you to use @sc{gnu} Emacs to view (and |
| edit) the source files for the program you are debugging with |
| @value{GDBN}. |
| |
| To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the |
| executable file you want to debug as an argument. This command starts |
| @value{GDBN} as a subprocess of Emacs, with input and output through a newly |
| created Emacs buffer. |
| @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.) |
| |
| Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two |
| things: |
| |
| @itemize @bullet |
| @item |
| All ``terminal'' input and output goes through an Emacs buffer, called |
| the GUD buffer. |
| |
| This applies both to @value{GDBN} commands and their output, and to the input |
| and output done by the program you are debugging. |
| |
| This is useful because it means that you can copy the text of previous |
| commands and input them again; you can even use parts of the output |
| in this way. |
| |
| All the facilities of Emacs' Shell mode are available for interacting |
| with your program. In particular, you can send signals the usual |
| way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a |
| stop. |
| |
| @item |
| @value{GDBN} displays source code through Emacs. |
| |
| Each time @value{GDBN} displays a stack frame, Emacs automatically finds the |
| source file for that frame and puts an arrow (@samp{=>}) at the |
| left margin of the current line. Emacs uses a separate buffer for |
| source display, and splits the screen to show both your @value{GDBN} session |
| and the source. |
| |
| Explicit @value{GDBN} @code{list} or search commands still produce output as |
| usual, but you probably have no reason to use them from Emacs. |
| @end itemize |
| |
| We call this @dfn{text command mode}. Emacs 22.1, and later, also uses |
| a graphical mode, enabled by default, which provides further buffers |
| that can control the execution and describe the state of your program. |
| @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}. |
| |
| If you specify an absolute file name when prompted for the @kbd{M-x |
| gdb} argument, then Emacs sets your current working directory to where |
| your program resides. If you only specify the file name, then Emacs |
| sets your current working directory to the directory associated |
| with the previous buffer. In this case, @value{GDBN} may find your |
| program by searching your environment's @code{PATH} variable, but on |
| some operating systems it might not find the source. So, although the |
| @value{GDBN} input and output session proceeds normally, the auxiliary |
| buffer does not display the current source and line of execution. |
| |
| The initial working directory of @value{GDBN} is printed on the top |
| line of the GUD buffer and this serves as a default for the commands |
| that specify files for @value{GDBN} to operate on. @xref{Files, |
| ,Commands to Specify Files}. |
| |
| By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you |
| need to call @value{GDBN} by a different name (for example, if you |
| keep several configurations around, with different names) you can |
| customize the Emacs variable @code{gud-gdb-command-name} to run the |
| one you want. |
| |
| In the GUD buffer, you can use these special Emacs commands in |
| addition to the standard Shell mode commands: |
| |
| @table @kbd |
| @item C-h m |
| Describe the features of Emacs' GUD Mode. |
| |
| @item C-c C-s |
| Execute to another source line, like the @value{GDBN} @code{step} command; also |
| update the display window to show the current file and location. |
| |
| @item C-c C-n |
| Execute to next source line in this function, skipping all function |
| calls, like the @value{GDBN} @code{next} command. Then update the display window |
| to show the current file and location. |
| |
| @item C-c C-i |
| Execute one instruction, like the @value{GDBN} @code{stepi} command; update |
| display window accordingly. |
| |
| @item C-c C-f |
| Execute until exit from the selected stack frame, like the @value{GDBN} |
| @code{finish} command. |
| |
| @item C-c C-r |
| Continue execution of your program, like the @value{GDBN} @code{continue} |
| command. |
| |
| @item C-c < |
| Go up the number of frames indicated by the numeric argument |
| (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}), |
| like the @value{GDBN} @code{up} command. |
| |
| @item C-c > |
| Go down the number of frames indicated by the numeric argument, like the |
| @value{GDBN} @code{down} command. |
| @end table |
| |
| In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break}) |
| tells @value{GDBN} to set a breakpoint on the source line point is on. |
| |
| In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a |
| separate frame which shows a backtrace when the GUD buffer is current. |
| Move point to any frame in the stack and type @key{RET} to make it |
| become the current frame and display the associated source in the |
| source buffer. Alternatively, click @kbd{Mouse-2} to make the |
| selected frame become the current one. In graphical mode, the |
| speedbar displays watch expressions. |
| |
| If you accidentally delete the source-display buffer, an easy way to get |
| it back is to type the command @code{f} in the @value{GDBN} buffer, to |
| request a frame display; when you run under Emacs, this recreates |
| the source buffer if necessary to show you the context of the current |
| frame. |
| |
| The source files displayed in Emacs are in ordinary Emacs buffers |
| which are visiting the source files in the usual way. You can edit |
| the files with these buffers if you wish; but keep in mind that @value{GDBN} |
| communicates with Emacs in terms of line numbers. If you add or |
| delete lines from the text, the line numbers that @value{GDBN} knows cease |
| to correspond properly with the code. |
| |
| A more detailed description of Emacs' interaction with @value{GDBN} is |
| given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} |
| Emacs Manual}). |
| |
| @c The following dropped because Epoch is nonstandard. Reactivate |
| @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990 |
| @ignore |
| @kindex Emacs Epoch environment |
| @kindex Epoch |
| @kindex inspect |
| |
| Version 18 of @sc{gnu} Emacs has a built-in window system |
| called the @code{epoch} |
| environment. Users of this environment can use a new command, |
| @code{inspect} which performs identically to @code{print} except that |
| each value is printed in its own window. |
| @end ignore |
| |
| |
| @node GDB/MI |
| @chapter The @sc{gdb/mi} Interface |
| |
| @unnumberedsec Function and Purpose |
| |
| @cindex @sc{gdb/mi}, its purpose |
| @sc{gdb/mi} is a line based machine oriented text interface to |
| @value{GDBN} and is activated by specifying using the |
| @option{--interpreter} command line option (@pxref{Mode Options}). It |
| is specifically intended to support the development of systems which |
| use the debugger as just one small component of a larger system. |
| |
| This chapter is a specification of the @sc{gdb/mi} interface. It is written |
| in the form of a reference manual. |
| |
| Note that @sc{gdb/mi} is still under construction, so some of the |
| features described below are incomplete and subject to change |
| (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}). |
| |
| @unnumberedsec Notation and Terminology |
| |
| @cindex notational conventions, for @sc{gdb/mi} |
| This chapter uses the following notation: |
| |
| @itemize @bullet |
| @item |
| @code{|} separates two alternatives. |
| |
| @item |
| @code{[ @var{something} ]} indicates that @var{something} is optional: |
| it may or may not be given. |
| |
| @item |
| @code{( @var{group} )*} means that @var{group} inside the parentheses |
| may repeat zero or more times. |
| |
| @item |
| @code{( @var{group} )+} means that @var{group} inside the parentheses |
| may repeat one or more times. |
| |
| @item |
| @code{"@var{string}"} means a literal @var{string}. |
| @end itemize |
| |
| @ignore |
| @heading Dependencies |
| @end ignore |
| |
| @menu |
| * GDB/MI General Design:: |
| * GDB/MI Command Syntax:: |
| * GDB/MI Compatibility with CLI:: |
| * GDB/MI Development and Front Ends:: |
| * GDB/MI Output Records:: |
| * GDB/MI Simple Examples:: |
| * GDB/MI Command Description Format:: |
| * GDB/MI Breakpoint Commands:: |
| * GDB/MI Program Context:: |
| * GDB/MI Thread Commands:: |
| * GDB/MI Ada Tasking Commands:: |
| * GDB/MI Program Execution:: |
| * GDB/MI Stack Manipulation:: |
| * GDB/MI Variable Objects:: |
| * GDB/MI Data Manipulation:: |
| * GDB/MI Tracepoint Commands:: |
| * GDB/MI Symbol Query:: |
| * GDB/MI File Commands:: |
| @ignore |
| * GDB/MI Kod Commands:: |
| * GDB/MI Memory Overlay Commands:: |
| * GDB/MI Signal Handling Commands:: |
| @end ignore |
| * GDB/MI Target Manipulation:: |
| * GDB/MI File Transfer Commands:: |
| * GDB/MI Miscellaneous Commands:: |
| @end menu |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI General Design |
| @section @sc{gdb/mi} General Design |
| @cindex GDB/MI General Design |
| |
| Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three |
| parts---commands sent to @value{GDBN}, responses to those commands |
| and notifications. Each command results in exactly one response, |
| indicating either successful completion of the command, or an error. |
| For the commands that do not resume the target, the response contains the |
| requested information. For the commands that resume the target, the |
| response only indicates whether the target was successfully resumed. |
| Notifications is the mechanism for reporting changes in the state of the |
| target, or in @value{GDBN} state, that cannot conveniently be associated with |
| a command and reported as part of that command response. |
| |
| The important examples of notifications are: |
| @itemize @bullet |
| |
| @item |
| Exec notifications. These are used to report changes in |
| target state---when a target is resumed, or stopped. It would not |
| be feasible to include this information in response of resuming |
| commands, because one resume commands can result in multiple events in |
| different threads. Also, quite some time may pass before any event |
| happens in the target, while a frontend needs to know whether the resuming |
| command itself was successfully executed. |
| |
| @item |
| Console output, and status notifications. Console output |
| notifications are used to report output of CLI commands, as well as |
| diagnostics for other commands. Status notifications are used to |
| report the progress of a long-running operation. Naturally, including |
| this information in command response would mean no output is produced |
| until the command is finished, which is undesirable. |
| |
| @item |
| General notifications. Commands may have various side effects on |
| the @value{GDBN} or target state beyond their official purpose. For example, |
| a command may change the selected thread. Although such changes can |
| be included in command response, using notification allows for more |
| orthogonal frontend design. |
| |
| @end itemize |
| |
| There's no guarantee that whenever an MI command reports an error, |
| @value{GDBN} or the target are in any specific state, and especially, |
| the state is not reverted to the state before the MI command was |
| processed. Therefore, whenever an MI command results in an error, |
| we recommend that the frontend refreshes all the information shown in |
| the user interface. |
| |
| |
| @menu |
| * Context management:: |
| * Asynchronous and non-stop modes:: |
| * Thread groups:: |
| @end menu |
| |
| @node Context management |
| @subsection Context management |
| |
| In most cases when @value{GDBN} accesses the target, this access is |
| done in context of a specific thread and frame (@pxref{Frames}). |
| Often, even when accessing global data, the target requires that a thread |
| be specified. The CLI interface maintains the selected thread and frame, |
| and supplies them to target on each command. This is convenient, |
| because a command line user would not want to specify that information |
| explicitly on each command, and because user interacts with |
| @value{GDBN} via a single terminal, so no confusion is possible as |
| to what thread and frame are the current ones. |
| |
| In the case of MI, the concept of selected thread and frame is less |
| useful. First, a frontend can easily remember this information |
| itself. Second, a graphical frontend can have more than one window, |
| each one used for debugging a different thread, and the frontend might |
| want to access additional threads for internal purposes. This |
| increases the risk that by relying on implicitly selected thread, the |
| frontend may be operating on a wrong one. Therefore, each MI command |
| should explicitly specify which thread and frame to operate on. To |
| make it possible, each MI command accepts the @samp{--thread} and |
| @samp{--frame} options, the value to each is @value{GDBN} identifier |
| for thread and frame to operate on. |
| |
| Usually, each top-level window in a frontend allows the user to select |
| a thread and a frame, and remembers the user selection for further |
| operations. However, in some cases @value{GDBN} may suggest that the |
| current thread be changed. For example, when stopping on a breakpoint |
| it is reasonable to switch to the thread where breakpoint is hit. For |
| another example, if the user issues the CLI @samp{thread} command via |
| the frontend, it is desirable to change the frontend's selected thread to the |
| one specified by user. @value{GDBN} communicates the suggestion to |
| change current thread using the @samp{=thread-selected} notification. |
| No such notification is available for the selected frame at the moment. |
| |
| Note that historically, MI shares the selected thread with CLI, so |
| frontends used the @code{-thread-select} to execute commands in the |
| right context. However, getting this to work right is cumbersome. The |
| simplest way is for frontend to emit @code{-thread-select} command |
| before every command. This doubles the number of commands that need |
| to be sent. The alternative approach is to suppress @code{-thread-select} |
| if the selected thread in @value{GDBN} is supposed to be identical to the |
| thread the frontend wants to operate on. However, getting this |
| optimization right can be tricky. In particular, if the frontend |
| sends several commands to @value{GDBN}, and one of the commands changes the |
| selected thread, then the behaviour of subsequent commands will |
| change. So, a frontend should either wait for response from such |
| problematic commands, or explicitly add @code{-thread-select} for |
| all subsequent commands. No frontend is known to do this exactly |
| right, so it is suggested to just always pass the @samp{--thread} and |
| @samp{--frame} options. |
| |
| @node Asynchronous and non-stop modes |
| @subsection Asynchronous command execution and non-stop mode |
| |
| On some targets, @value{GDBN} is capable of processing MI commands |
| even while the target is running. This is called @dfn{asynchronous |
| command execution} (@pxref{Background Execution}). The frontend may |
| specify a preferrence for asynchronous execution using the |
| @code{-gdb-set target-async 1} command, which should be emitted before |
| either running the executable or attaching to the target. After the |
| frontend has started the executable or attached to the target, it can |
| find if asynchronous execution is enabled using the |
| @code{-list-target-features} command. |
| |
| Even if @value{GDBN} can accept a command while target is running, |
| many commands that access the target do not work when the target is |
| running. Therefore, asynchronous command execution is most useful |
| when combined with non-stop mode (@pxref{Non-Stop Mode}). Then, |
| it is possible to examine the state of one thread, while other threads |
| are running. |
| |
| When a given thread is running, MI commands that try to access the |
| target in the context of that thread may not work, or may work only on |
| some targets. In particular, commands that try to operate on thread's |
| stack will not work, on any target. Commands that read memory, or |
| modify breakpoints, may work or not work, depending on the target. Note |
| that even commands that operate on global state, such as @code{print}, |
| @code{set}, and breakpoint commands, still access the target in the |
| context of a specific thread, so frontend should try to find a |
| stopped thread and perform the operation on that thread (using the |
| @samp{--thread} option). |
| |
| Which commands will work in the context of a running thread is |
| highly target dependent. However, the two commands |
| @code{-exec-interrupt}, to stop a thread, and @code{-thread-info}, |
| to find the state of a thread, will always work. |
| |
| @node Thread groups |
| @subsection Thread groups |
| @value{GDBN} may be used to debug several processes at the same time. |
| On some platfroms, @value{GDBN} may support debugging of several |
| hardware systems, each one having several cores with several different |
| processes running on each core. This section describes the MI |
| mechanism to support such debugging scenarios. |
| |
| The key observation is that regardless of the structure of the |
| target, MI can have a global list of threads, because most commands that |
| accept the @samp{--thread} option do not need to know what process that |
| thread belongs to. Therefore, it is not necessary to introduce |
| neither additional @samp{--process} option, nor an notion of the |
| current process in the MI interface. The only strictly new feature |
| that is required is the ability to find how the threads are grouped |
| into processes. |
| |
| To allow the user to discover such grouping, and to support arbitrary |
| hierarchy of machines/cores/processes, MI introduces the concept of a |
| @dfn{thread group}. Thread group is a collection of threads and other |
| thread groups. A thread group always has a string identifier, a type, |
| and may have additional attributes specific to the type. A new |
| command, @code{-list-thread-groups}, returns the list of top-level |
| thread groups, which correspond to processes that @value{GDBN} is |
| debugging at the moment. By passing an identifier of a thread group |
| to the @code{-list-thread-groups} command, it is possible to obtain |
| the members of specific thread group. |
| |
| To allow the user to easily discover processes, and other objects, he |
| wishes to debug, a concept of @dfn{available thread group} is |
| introduced. Available thread group is an thread group that |
| @value{GDBN} is not debugging, but that can be attached to, using the |
| @code{-target-attach} command. The list of available top-level thread |
| groups can be obtained using @samp{-list-thread-groups --available}. |
| In general, the content of a thread group may be only retrieved only |
| after attaching to that thread group. |
| |
| Thread groups are related to inferiors (@pxref{Inferiors and |
| Programs}). Each inferior corresponds to a thread group of a special |
| type @samp{process}, and some additional operations are permitted on |
| such thread groups. |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Command Syntax |
| @section @sc{gdb/mi} Command Syntax |
| |
| @menu |
| * GDB/MI Input Syntax:: |
| * GDB/MI Output Syntax:: |
| @end menu |
| |
| @node GDB/MI Input Syntax |
| @subsection @sc{gdb/mi} Input Syntax |
| |
| @cindex input syntax for @sc{gdb/mi} |
| @cindex @sc{gdb/mi}, input syntax |
| @table @code |
| @item @var{command} @expansion{} |
| @code{@var{cli-command} | @var{mi-command}} |
| |
| @item @var{cli-command} @expansion{} |
| @code{[ @var{token} ] @var{cli-command} @var{nl}}, where |
| @var{cli-command} is any existing @value{GDBN} CLI command. |
| |
| @item @var{mi-command} @expansion{} |
| @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )* |
| @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}} |
| |
| @item @var{token} @expansion{} |
| "any sequence of digits" |
| |
| @item @var{option} @expansion{} |
| @code{"-" @var{parameter} [ " " @var{parameter} ]} |
| |
| @item @var{parameter} @expansion{} |
| @code{@var{non-blank-sequence} | @var{c-string}} |
| |
| @item @var{operation} @expansion{} |
| @emph{any of the operations described in this chapter} |
| |
| @item @var{non-blank-sequence} @expansion{} |
| @emph{anything, provided it doesn't contain special characters such as |
| "-", @var{nl}, """ and of course " "} |
| |
| @item @var{c-string} @expansion{} |
| @code{""" @var{seven-bit-iso-c-string-content} """} |
| |
| @item @var{nl} @expansion{} |
| @code{CR | CR-LF} |
| @end table |
| |
| @noindent |
| Notes: |
| |
| @itemize @bullet |
| @item |
| The CLI commands are still handled by the @sc{mi} interpreter; their |
| output is described below. |
| |
| @item |
| The @code{@var{token}}, when present, is passed back when the command |
| finishes. |
| |
| @item |
| Some @sc{mi} commands accept optional arguments as part of the parameter |
| list. Each option is identified by a leading @samp{-} (dash) and may be |
| followed by an optional argument parameter. Options occur first in the |
| parameter list and can be delimited from normal parameters using |
| @samp{--} (this is useful when some parameters begin with a dash). |
| @end itemize |
| |
| Pragmatics: |
| |
| @itemize @bullet |
| @item |
| We want easy access to the existing CLI syntax (for debugging). |
| |
| @item |
| We want it to be easy to spot a @sc{mi} operation. |
| @end itemize |
| |
| @node GDB/MI Output Syntax |
| @subsection @sc{gdb/mi} Output Syntax |
| |
| @cindex output syntax of @sc{gdb/mi} |
| @cindex @sc{gdb/mi}, output syntax |
| The output from @sc{gdb/mi} consists of zero or more out-of-band records |
| followed, optionally, by a single result record. This result record |
| is for the most recent command. The sequence of output records is |
| terminated by @samp{(gdb)}. |
| |
| If an input command was prefixed with a @code{@var{token}} then the |
| corresponding output for that command will also be prefixed by that same |
| @var{token}. |
| |
| @table @code |
| @item @var{output} @expansion{} |
| @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}} |
| |
| @item @var{result-record} @expansion{} |
| @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}} |
| |
| @item @var{out-of-band-record} @expansion{} |
| @code{@var{async-record} | @var{stream-record}} |
| |
| @item @var{async-record} @expansion{} |
| @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}} |
| |
| @item @var{exec-async-output} @expansion{} |
| @code{[ @var{token} ] "*" @var{async-output}} |
| |
| @item @var{status-async-output} @expansion{} |
| @code{[ @var{token} ] "+" @var{async-output}} |
| |
| @item @var{notify-async-output} @expansion{} |
| @code{[ @var{token} ] "=" @var{async-output}} |
| |
| @item @var{async-output} @expansion{} |
| @code{@var{async-class} ( "," @var{result} )* @var{nl}} |
| |
| @item @var{result-class} @expansion{} |
| @code{"done" | "running" | "connected" | "error" | "exit"} |
| |
| @item @var{async-class} @expansion{} |
| @code{"stopped" | @var{others}} (where @var{others} will be added |
| depending on the needs---this is still in development). |
| |
| @item @var{result} @expansion{} |
| @code{ @var{variable} "=" @var{value}} |
| |
| @item @var{variable} @expansion{} |
| @code{ @var{string} } |
| |
| @item @var{value} @expansion{} |
| @code{ @var{const} | @var{tuple} | @var{list} } |
| |
| @item @var{const} @expansion{} |
| @code{@var{c-string}} |
| |
| @item @var{tuple} @expansion{} |
| @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" } |
| |
| @item @var{list} @expansion{} |
| @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "[" |
| @var{result} ( "," @var{result} )* "]" } |
| |
| @item @var{stream-record} @expansion{} |
| @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}} |
| |
| @item @var{console-stream-output} @expansion{} |
| @code{"~" @var{c-string}} |
| |
| @item @var{target-stream-output} @expansion{} |
| @code{"@@" @var{c-string}} |
| |
| @item @var{log-stream-output} @expansion{} |
| @code{"&" @var{c-string}} |
| |
| @item @var{nl} @expansion{} |
| @code{CR | CR-LF} |
| |
| @item @var{token} @expansion{} |
| @emph{any sequence of digits}. |
| @end table |
| |
| @noindent |
| Notes: |
| |
| @itemize @bullet |
| @item |
| All output sequences end in a single line containing a period. |
| |
| @item |
| The @code{@var{token}} is from the corresponding request. Note that |
| for all async output, while the token is allowed by the grammar and |
| may be output by future versions of @value{GDBN} for select async |
| output messages, it is generally omitted. Frontends should treat |
| all async output as reporting general changes in the state of the |
| target and there should be no need to associate async output to any |
| prior command. |
| |
| @item |
| @cindex status output in @sc{gdb/mi} |
| @var{status-async-output} contains on-going status information about the |
| progress of a slow operation. It can be discarded. All status output is |
| prefixed by @samp{+}. |
| |
| @item |
| @cindex async output in @sc{gdb/mi} |
| @var{exec-async-output} contains asynchronous state change on the target |
| (stopped, started, disappeared). All async output is prefixed by |
| @samp{*}. |
| |
| @item |
| @cindex notify output in @sc{gdb/mi} |
| @var{notify-async-output} contains supplementary information that the |
| client should handle (e.g., a new breakpoint information). All notify |
| output is prefixed by @samp{=}. |
| |
| @item |
| @cindex console output in @sc{gdb/mi} |
| @var{console-stream-output} is output that should be displayed as is in the |
| console. It is the textual response to a CLI command. All the console |
| output is prefixed by @samp{~}. |
| |
| @item |
| @cindex target output in @sc{gdb/mi} |
| @var{target-stream-output} is the output produced by the target program. |
| All the target output is prefixed by @samp{@@}. |
| |
| @item |
| @cindex log output in @sc{gdb/mi} |
| @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for |
| instance messages that should be displayed as part of an error log. All |
| the log output is prefixed by @samp{&}. |
| |
| @item |
| @cindex list output in @sc{gdb/mi} |
| New @sc{gdb/mi} commands should only output @var{lists} containing |
| @var{values}. |
| |
| |
| @end itemize |
| |
| @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more |
| details about the various output records. |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Compatibility with CLI |
| @section @sc{gdb/mi} Compatibility with CLI |
| |
| @cindex compatibility, @sc{gdb/mi} and CLI |
| @cindex @sc{gdb/mi}, compatibility with CLI |
| |
| For the developers convenience CLI commands can be entered directly, |
| but there may be some unexpected behaviour. For example, commands |
| that query the user will behave as if the user replied yes, breakpoint |
| command lists are not executed and some CLI commands, such as |
| @code{if}, @code{when} and @code{define}, prompt for further input with |
| @samp{>}, which is not valid MI output. |
| |
| This feature may be removed at some stage in the future and it is |
| recommended that front ends use the @code{-interpreter-exec} command |
| (@pxref{-interpreter-exec}). |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Development and Front Ends |
| @section @sc{gdb/mi} Development and Front Ends |
| @cindex @sc{gdb/mi} development |
| |
| The application which takes the MI output and presents the state of the |
| program being debugged to the user is called a @dfn{front end}. |
| |
| Although @sc{gdb/mi} is still incomplete, it is currently being used |
| by a variety of front ends to @value{GDBN}. This makes it difficult |
| to introduce new functionality without breaking existing usage. This |
| section tries to minimize the problems by describing how the protocol |
| might change. |
| |
| Some changes in MI need not break a carefully designed front end, and |
| for these the MI version will remain unchanged. The following is a |
| list of changes that may occur within one level, so front ends should |
| parse MI output in a way that can handle them: |
| |
| @itemize @bullet |
| @item |
| New MI commands may be added. |
| |
| @item |
| New fields may be added to the output of any MI command. |
| |
| @item |
| The range of values for fields with specified values, e.g., |
| @code{in_scope} (@pxref{-var-update}) may be extended. |
| |
| @c The format of field's content e.g type prefix, may change so parse it |
| @c at your own risk. Yes, in general? |
| |
| @c The order of fields may change? Shouldn't really matter but it might |
| @c resolve inconsistencies. |
| @end itemize |
| |
| If the changes are likely to break front ends, the MI version level |
| will be increased by one. This will allow the front end to parse the |
| output according to the MI version. Apart from mi0, new versions of |
| @value{GDBN} will not support old versions of MI and it will be the |
| responsibility of the front end to work with the new one. |
| |
| @c Starting with mi3, add a new command -mi-version that prints the MI |
| @c version? |
| |
| The best way to avoid unexpected changes in MI that might break your front |
| end is to make your project known to @value{GDBN} developers and |
| follow development on @email{gdb@@sourceware.org} and |
| @email{gdb-patches@@sourceware.org}. |
| @cindex mailing lists |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Output Records |
| @section @sc{gdb/mi} Output Records |
| |
| @menu |
| * GDB/MI Result Records:: |
| * GDB/MI Stream Records:: |
| * GDB/MI Async Records:: |
| * GDB/MI Frame Information:: |
| * GDB/MI Thread Information:: |
| * GDB/MI Ada Exception Information:: |
| @end menu |
| |
| @node GDB/MI Result Records |
| @subsection @sc{gdb/mi} Result Records |
| |
| @cindex result records in @sc{gdb/mi} |
| @cindex @sc{gdb/mi}, result records |
| In addition to a number of out-of-band notifications, the response to a |
| @sc{gdb/mi} command includes one of the following result indications: |
| |
| @table @code |
| @findex ^done |
| @item "^done" [ "," @var{results} ] |
| The synchronous operation was successful, @code{@var{results}} are the return |
| values. |
| |
| @item "^running" |
| @findex ^running |
| This result record is equivalent to @samp{^done}. Historically, it |
| was output instead of @samp{^done} if the command has resumed the |
| target. This behaviour is maintained for backward compatibility, but |
| all frontends should treat @samp{^done} and @samp{^running} |
| identically and rely on the @samp{*running} output record to determine |
| which threads are resumed. |
| |
| @item "^connected" |
| @findex ^connected |
| @value{GDBN} has connected to a remote target. |
| |
| @item "^error" "," @var{c-string} |
| @findex ^error |
| The operation failed. The @code{@var{c-string}} contains the corresponding |
| error message. |
| |
| @item "^exit" |
| @findex ^exit |
| @value{GDBN} has terminated. |
| |
| @end table |
| |
| @node GDB/MI Stream Records |
| @subsection @sc{gdb/mi} Stream Records |
| |
| @cindex @sc{gdb/mi}, stream records |
| @cindex stream records in @sc{gdb/mi} |
| @value{GDBN} internally maintains a number of output streams: the console, the |
| target, and the log. The output intended for each of these streams is |
| funneled through the @sc{gdb/mi} interface using @dfn{stream records}. |
| |
| Each stream record begins with a unique @dfn{prefix character} which |
| identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output |
| Syntax}). In addition to the prefix, each stream record contains a |
| @code{@var{string-output}}. This is either raw text (with an implicit new |
| line) or a quoted C string (which does not contain an implicit newline). |
| |
| @table @code |
| @item "~" @var{string-output} |
| The console output stream contains text that should be displayed in the |
| CLI console window. It contains the textual responses to CLI commands. |
| |
| @item "@@" @var{string-output} |
| The target output stream contains any textual output from the running |
| target. This is only present when GDB's event loop is truly |
| asynchronous, which is currently only the case for remote targets. |
| |
| @item "&" @var{string-output} |
| The log stream contains debugging messages being produced by @value{GDBN}'s |
| internals. |
| @end table |
| |
| @node GDB/MI Async Records |
| @subsection @sc{gdb/mi} Async Records |
| |
| @cindex async records in @sc{gdb/mi} |
| @cindex @sc{gdb/mi}, async records |
| @dfn{Async} records are used to notify the @sc{gdb/mi} client of |
| additional changes that have occurred. Those changes can either be a |
| consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of |
| target activity (e.g., target stopped). |
| |
| The following is the list of possible async records: |
| |
| @table @code |
| |
| @item *running,thread-id="@var{thread}" |
| The target is now running. The @var{thread} field tells which |
| specific thread is now running, and can be @samp{all} if all threads |
| are running. The frontend should assume that no interaction with a |
| running thread is possible after this notification is produced. |
| The frontend should not assume that this notification is output |
| only once for any command. @value{GDBN} may emit this notification |
| several times, either for different threads, because it cannot resume |
| all threads together, or even for a single thread, if the thread must |
| be stepped though some code before letting it run freely. |
| |
| @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}" |
| The target has stopped. The @var{reason} field can have one of the |
| following values: |
| |
| @table @code |
| @item breakpoint-hit |
| A breakpoint was reached. |
| @item watchpoint-trigger |
| A watchpoint was triggered. |
| @item read-watchpoint-trigger |
| A read watchpoint was triggered. |
| @item access-watchpoint-trigger |
| An access watchpoint was triggered. |
| @item function-finished |
| An -exec-finish or similar CLI command was accomplished. |
| @item location-reached |
| An -exec-until or similar CLI command was accomplished. |
| @item watchpoint-scope |
| A watchpoint has gone out of scope. |
| @item end-stepping-range |
| An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or |
| similar CLI command was accomplished. |
| @item exited-signalled |
| The inferior exited because of a signal. |
| @item exited |
| The inferior exited. |
| @item exited-normally |
| The inferior exited normally. |
| @item signal-received |
| A signal was received by the inferior. |
| @item solib-event |
| The inferior has stopped due to a library being loaded or unloaded. |
| This can happen when @code{stop-on-solib-events} (@pxref{Files}) is |
| set or when a @code{catch load} or @code{catch unload} catchpoint is |
| in use (@pxref{Set Catchpoints}). |
| @item fork |
| The inferior has forked. This is reported when @code{catch fork} |
| (@pxref{Set Catchpoints}) has been used. |
| @item vfork |
| The inferior has vforked. This is reported in when @code{catch vfork} |
| (@pxref{Set Catchpoints}) has been used. |
| @item syscall-entry |
| The inferior entered a system call. This is reported when @code{catch |
| syscall} (@pxref{Set Catchpoints}) has been used. |
| @item syscall-entry |
| The inferior returned from a system call. This is reported when |
| @code{catch syscall} (@pxref{Set Catchpoints}) has been used. |
| @item exec |
| The inferior called @code{exec}. This is reported when @code{catch exec} |
| (@pxref{Set Catchpoints}) has been used. |
| @end table |
| |
| The @var{id} field identifies the thread that directly caused the stop |
| -- for example by hitting a breakpoint. Depending on whether all-stop |
| mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either |
| stop all threads, or only the thread that directly triggered the stop. |
| If all threads are stopped, the @var{stopped} field will have the |
| value of @code{"all"}. Otherwise, the value of the @var{stopped} |
| field will be a list of thread identifiers. Presently, this list will |
| always include a single thread, but frontend should be prepared to see |
| several threads in the list. The @var{core} field reports the |
| processor core on which the stop event has happened. This field may be absent |
| if such information is not available. |
| |
| @item =thread-group-added,id="@var{id}" |
| @itemx =thread-group-removed,id="@var{id}" |
| A thread group was either added or removed. The @var{id} field |
| contains the @value{GDBN} identifier of the thread group. When a thread |
| group is added, it generally might not be associated with a running |
| process. When a thread group is removed, its id becomes invalid and |
| cannot be used in any way. |
| |
| @item =thread-group-started,id="@var{id}",pid="@var{pid}" |
| A thread group became associated with a running program, |
| either because the program was just started or the thread group |
| was attached to a program. The @var{id} field contains the |
| @value{GDBN} identifier of the thread group. The @var{pid} field |
| contains process identifier, specific to the operating system. |
| |
| @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"] |
| A thread group is no longer associated with a running program, |
| either because the program has exited, or because it was detached |
| from. The @var{id} field contains the @value{GDBN} identifier of the |
| thread group. @var{code} is the exit code of the inferior; it exists |
| only when the inferior exited with some code. |
| |
| @item =thread-created,id="@var{id}",group-id="@var{gid}" |
| @itemx =thread-exited,id="@var{id}",group-id="@var{gid}" |
| A thread either was created, or has exited. The @var{id} field |
| contains the @value{GDBN} identifier of the thread. The @var{gid} |
| field identifies the thread group this thread belongs to. |
| |
| @item =thread-selected,id="@var{id}" |
| Informs that the selected thread was changed as result of the last |
| command. This notification is not emitted as result of @code{-thread-select} |
| command but is emitted whenever an MI command that is not documented |
| to change the selected thread actually changes it. In particular, |
| invoking, directly or indirectly (via user-defined command), the CLI |
| @code{thread} command, will generate this notification. |
| |
| We suggest that in response to this notification, front ends |
| highlight the selected thread and cause subsequent commands to apply to |
| that thread. |
| |
| @item =library-loaded,... |
| Reports that a new library file was loaded by the program. This |
| notification has 4 fields---@var{id}, @var{target-name}, |
| @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an |
| opaque identifier of the library. For remote debugging case, |
| @var{target-name} and @var{host-name} fields give the name of the |
| library file on the target, and on the host respectively. For native |
| debugging, both those fields have the same value. The |
| @var{symbols-loaded} field is emitted only for backward compatibility |
| and should not be relied on to convey any useful information. The |
| @var{thread-group} field, if present, specifies the id of the thread |
| group in whose context the library was loaded. If the field is |
| absent, it means the library was loaded in the context of all present |
| thread groups. |
| |
| @item =library-unloaded,... |
| Reports that a library was unloaded by the program. This notification |
| has 3 fields---@var{id}, @var{target-name} and @var{host-name} with |
| the same meaning as for the @code{=library-loaded} notification. |
| The @var{thread-group} field, if present, specifies the id of the |
| thread group in whose context the library was unloaded. If the field is |
| absent, it means the library was unloaded in the context of all present |
| thread groups. |
| |
| @item =breakpoint-created,bkpt=@{...@} |
| @itemx =breakpoint-modified,bkpt=@{...@} |
| @itemx =breakpoint-deleted,bkpt=@{...@} |
| Reports that a breakpoint was created, modified, or deleted, |
| respectively. Only user-visible breakpoints are reported to the MI |
| user. |
| |
| The @var{bkpt} argument is of the same form as returned by the various |
| breakpoint commands; @xref{GDB/MI Breakpoint Commands}. |
| |
| Note that if a breakpoint is emitted in the result record of a |
| command, then it will not also be emitted in an async record. |
| |
| @end table |
| |
| @node GDB/MI Frame Information |
| @subsection @sc{gdb/mi} Frame Information |
| |
| Response from many MI commands includes an information about stack |
| frame. This information is a tuple that may have the following |
| fields: |
| |
| @table @code |
| @item level |
| The level of the stack frame. The innermost frame has the level of |
| zero. This field is always present. |
| |
| @item func |
| The name of the function corresponding to the frame. This field may |
| be absent if @value{GDBN} is unable to determine the function name. |
| |
| @item addr |
| The code address for the frame. This field is always present. |
| |
| @item file |
| The name of the source files that correspond to the frame's code |
| address. This field may be absent. |
| |
| @item line |
| The source line corresponding to the frames' code address. This field |
| may be absent. |
| |
| @item from |
| The name of the binary file (either executable or shared library) the |
| corresponds to the frame's code address. This field may be absent. |
| |
| @end table |
| |
| @node GDB/MI Thread Information |
| @subsection @sc{gdb/mi} Thread Information |
| |
| Whenever @value{GDBN} has to report an information about a thread, it |
| uses a tuple with the following fields: |
| |
| @table @code |
| @item id |
| The numeric id assigned to the thread by @value{GDBN}. This field is |
| always present. |
| |
| @item target-id |
| Target-specific string identifying the thread. This field is always present. |
| |
| @item details |
| Additional information about the thread provided by the target. |
| It is supposed to be human-readable and not interpreted by the |
| frontend. This field is optional. |
| |
| @item state |
| Either @samp{stopped} or @samp{running}, depending on whether the |
| thread is presently running. This field is always present. |
| |
| @item core |
| The value of this field is an integer number of the processor core the |
| thread was last seen on. This field is optional. |
| @end table |
| |
| @node GDB/MI Ada Exception Information |
| @subsection @sc{gdb/mi} Ada Exception Information |
| |
| Whenever a @code{*stopped} record is emitted because the program |
| stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}), |
| @value{GDBN} provides the name of the exception that was raised via |
| the @code{exception-name} field. |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Simple Examples |
| @section Simple Examples of @sc{gdb/mi} Interaction |
| @cindex @sc{gdb/mi}, simple examples |
| |
| This subsection presents several simple examples of interaction using |
| the @sc{gdb/mi} interface. In these examples, @samp{->} means that the |
| following line is passed to @sc{gdb/mi} as input, while @samp{<-} means |
| the output received from @sc{gdb/mi}. |
| |
| Note the line breaks shown in the examples are here only for |
| readability, they don't appear in the real output. |
| |
| @subheading Setting a Breakpoint |
| |
| Setting a breakpoint generates synchronous output which contains detailed |
| information of the breakpoint. |
| |
| @smallexample |
| -> -break-insert main |
| <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep", |
| enabled="y",addr="0x08048564",func="main",file="myprog.c", |
| fullname="/home/nickrob/myprog.c",line="68",times="0"@} |
| <- (gdb) |
| @end smallexample |
| |
| @subheading Program Execution |
| |
| Program execution generates asynchronous records and MI gives the |
| reason that execution stopped. |
| |
| @smallexample |
| -> -exec-run |
| <- ^running |
| <- (gdb) |
| <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0", |
| frame=@{addr="0x08048564",func="main", |
| args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}], |
| file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@} |
| <- (gdb) |
| -> -exec-continue |
| <- ^running |
| <- (gdb) |
| <- *stopped,reason="exited-normally" |
| <- (gdb) |
| @end smallexample |
| |
| @subheading Quitting @value{GDBN} |
| |
| Quitting @value{GDBN} just prints the result class @samp{^exit}. |
| |
| @smallexample |
| -> (gdb) |
| <- -gdb-exit |
| <- ^exit |
| @end smallexample |
| |
| Please note that @samp{^exit} is printed immediately, but it might |
| take some time for @value{GDBN} to actually exit. During that time, @value{GDBN} |
| performs necessary cleanups, including killing programs being debugged |
| or disconnecting from debug hardware, so the frontend should wait till |
| @value{GDBN} exits and should only forcibly kill @value{GDBN} if it |
| fails to exit in reasonable time. |
| |
| @subheading A Bad Command |
| |
| Here's what happens if you pass a non-existent command: |
| |
| @smallexample |
| -> -rubbish |
| <- ^error,msg="Undefined MI command: rubbish" |
| <- (gdb) |
| @end smallexample |
| |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Command Description Format |
| @section @sc{gdb/mi} Command Description Format |
| |
| The remaining sections describe blocks of commands. Each block of |
| commands is laid out in a fashion similar to this section. |
| |
| @subheading Motivation |
| |
| The motivation for this collection of commands. |
| |
| @subheading Introduction |
| |
| A brief introduction to this collection of commands as a whole. |
| |
| @subheading Commands |
| |
| For each command in the block, the following is described: |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -command @var{args}@dots{} |
| @end smallexample |
| |
| @subsubheading Result |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} CLI command(s), if any. |
| |
| @subsubheading Example |
| |
| Example(s) formatted for readability. Some of the described commands have |
| not been implemented yet and these are labeled N.A.@: (not available). |
| |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Breakpoint Commands |
| @section @sc{gdb/mi} Breakpoint Commands |
| |
| @cindex breakpoint commands for @sc{gdb/mi} |
| @cindex @sc{gdb/mi}, breakpoint commands |
| This section documents @sc{gdb/mi} commands for manipulating |
| breakpoints. |
| |
| @subheading The @code{-break-after} Command |
| @findex -break-after |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-after @var{number} @var{count} |
| @end smallexample |
| |
| The breakpoint number @var{number} is not in effect until it has been |
| hit @var{count} times. To see how this is reflected in the output of |
| the @samp{-break-list} command, see the description of the |
| @samp{-break-list} command below. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{ignore}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-insert main |
| ^done,bkpt=@{number="1",type="breakpoint",disp="keep", |
| enabled="y",addr="0x000100d0",func="main",file="hello.c", |
| fullname="/home/foo/hello.c",line="5",times="0"@} |
| (gdb) |
| -break-after 1 3 |
| ~ |
| ^done |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="1",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", |
| line="5",times="0",ignore="3"@}]@} |
| (gdb) |
| @end smallexample |
| |
| @ignore |
| @subheading The @code{-break-catch} Command |
| @findex -break-catch |
| @end ignore |
| |
| @subheading The @code{-break-commands} Command |
| @findex -break-commands |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-commands @var{number} [ @var{command1} ... @var{commandN} ] |
| @end smallexample |
| |
| Specifies the CLI commands that should be executed when breakpoint |
| @var{number} is hit. The parameters @var{command1} to @var{commandN} |
| are the commands. If no command is specified, any previously-set |
| commands are cleared. @xref{Break Commands}. Typical use of this |
| functionality is tracing a program, that is, printing of values of |
| some variables whenever breakpoint is hit and then continuing. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{commands}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-insert main |
| ^done,bkpt=@{number="1",type="breakpoint",disp="keep", |
| enabled="y",addr="0x000100d0",func="main",file="hello.c", |
| fullname="/home/foo/hello.c",line="5",times="0"@} |
| (gdb) |
| -break-commands 1 "print v" "continue" |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-break-condition} Command |
| @findex -break-condition |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-condition @var{number} @var{expr} |
| @end smallexample |
| |
| Breakpoint @var{number} will stop the program only if the condition in |
| @var{expr} is true. The condition becomes part of the |
| @samp{-break-list} output (see the description of the @samp{-break-list} |
| command below). |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{condition}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-condition 1 1 |
| ^done |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="1",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", |
| line="5",cond="1",times="0",ignore="3"@}]@} |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-break-delete} Command |
| @findex -break-delete |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-delete ( @var{breakpoint} )+ |
| @end smallexample |
| |
| Delete the breakpoint(s) whose number(s) are specified in the argument |
| list. This is obviously reflected in the breakpoint list. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{delete}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-delete 1 |
| ^done |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="0",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[]@} |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-break-disable} Command |
| @findex -break-disable |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-disable ( @var{breakpoint} )+ |
| @end smallexample |
| |
| Disable the named @var{breakpoint}(s). The field @samp{enabled} in the |
| break list is now set to @samp{n} for the named @var{breakpoint}(s). |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{disable}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-disable 2 |
| ^done |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="1",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n", |
| addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", |
| line="5",times="0"@}]@} |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-break-enable} Command |
| @findex -break-enable |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-enable ( @var{breakpoint} )+ |
| @end smallexample |
| |
| Enable (previously disabled) @var{breakpoint}(s). |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{enable}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-enable 2 |
| ^done |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="1",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y", |
| addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c", |
| line="5",times="0"@}]@} |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-break-info} Command |
| @findex -break-info |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-info @var{breakpoint} |
| @end smallexample |
| |
| @c REDUNDANT??? |
| Get information about a single breakpoint. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}. |
| |
| @subsubheading Example |
| N.A. |
| |
| @subheading The @code{-break-insert} Command |
| @findex -break-insert |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] |
| [ -c @var{condition} ] [ -i @var{ignore-count} ] |
| [ -p @var{thread-id} ] [ @var{location} ] |
| @end smallexample |
| |
| @noindent |
| If specified, @var{location}, can be one of: |
| |
| @itemize @bullet |
| @item function |
| @c @item +offset |
| @c @item -offset |
| @c @item linenum |
| @item filename:linenum |
| @item filename:function |
| @item *address |
| @end itemize |
| |
| The possible optional parameters of this command are: |
| |
| @table @samp |
| @item -t |
| Insert a temporary breakpoint. |
| @item -h |
| Insert a hardware breakpoint. |
| @item -f |
| If @var{location} cannot be parsed (for example if it |
| refers to unknown files or functions), create a pending |
| breakpoint. Without this flag, @value{GDBN} will report |
| an error, and won't create a breakpoint, if @var{location} |
| cannot be parsed. |
| @item -d |
| Create a disabled breakpoint. |
| @item -a |
| Create a tracepoint. @xref{Tracepoints}. When this parameter |
| is used together with @samp{-h}, a fast tracepoint is created. |
| @item -c @var{condition} |
| Make the breakpoint conditional on @var{condition}. |
| @item -i @var{ignore-count} |
| Initialize the @var{ignore-count}. |
| @item -p @var{thread-id} |
| Restrict the breakpoint to the specified @var{thread-id}. |
| @end table |
| |
| @subsubheading Result |
| |
| The result is in the form: |
| |
| @smallexample |
| ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep", |
| enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}", |
| fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},] |
| times="@var{times}"@} |
| @end smallexample |
| |
| @noindent |
| where @var{number} is the @value{GDBN} number for this breakpoint, |
| @var{funcname} is the name of the function where the breakpoint was |
| inserted, @var{filename} is the name of the source file which contains |
| this function, @var{lineno} is the source line number within that file |
| and @var{times} the number of times that the breakpoint has been hit |
| (always 0 for -break-insert but may be greater for -break-info or -break-list |
| which use the same output). |
| |
| Note: this format is open to change. |
| @c An out-of-band breakpoint instead of part of the result? |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak}, |
| @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-insert main |
| ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c", |
| fullname="/home/foo/recursive2.c,line="4",times="0"@} |
| (gdb) |
| -break-insert -t foo |
| ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c", |
| fullname="/home/foo/recursive2.c,line="11",times="0"@} |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="2",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x0001072c", func="main",file="recursive2.c", |
| fullname="/home/foo/recursive2.c,"line="4",times="0"@}, |
| bkpt=@{number="2",type="breakpoint",disp="del",enabled="y", |
| addr="0x00010774",func="foo",file="recursive2.c", |
| fullname="/home/foo/recursive2.c",line="11",times="0"@}]@} |
| (gdb) |
| @c -break-insert -r foo.* |
| @c ~int foo(int, int); |
| @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c, |
| @c "fullname="/home/foo/recursive2.c",line="11",times="0"@} |
| @c (gdb) |
| @end smallexample |
| |
| @subheading The @code{-break-list} Command |
| @findex -break-list |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-list |
| @end smallexample |
| |
| Displays the list of inserted breakpoints, showing the following fields: |
| |
| @table @samp |
| @item Number |
| number of the breakpoint |
| @item Type |
| type of the breakpoint: @samp{breakpoint} or @samp{watchpoint} |
| @item Disposition |
| should the breakpoint be deleted or disabled when it is hit: @samp{keep} |
| or @samp{nokeep} |
| @item Enabled |
| is the breakpoint enabled or no: @samp{y} or @samp{n} |
| @item Address |
| memory location at which the breakpoint is set |
| @item What |
| logical location of the breakpoint, expressed by function name, file |
| name, line number |
| @item Times |
| number of times the breakpoint has been hit |
| @end table |
| |
| If there are no breakpoints or watchpoints, the @code{BreakpointTable} |
| @code{body} field is an empty list. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info break}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="2",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}, |
| bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y", |
| addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c", |
| line="13",times="0"@}]@} |
| (gdb) |
| @end smallexample |
| |
| Here's an example of the result when there are no breakpoints: |
| |
| @smallexample |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="0",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[]@} |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-break-passcount} Command |
| @findex -break-passcount |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-passcount @var{tracepoint-number} @var{passcount} |
| @end smallexample |
| |
| Set the passcount for tracepoint @var{tracepoint-number} to |
| @var{passcount}. If the breakpoint referred to by @var{tracepoint-number} |
| is not a tracepoint, error is emitted. This corresponds to CLI |
| command @samp{passcount}. |
| |
| @subheading The @code{-break-watch} Command |
| @findex -break-watch |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -break-watch [ -a | -r ] |
| @end smallexample |
| |
| Create a watchpoint. With the @samp{-a} option it will create an |
| @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a |
| read from or on a write to the memory location. With the @samp{-r} |
| option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will |
| trigger only when the memory location is accessed for reading. Without |
| either of the options, the watchpoint created is a regular watchpoint, |
| i.e., it will trigger when the memory location is accessed for writing. |
| @xref{Set Watchpoints, , Setting Watchpoints}. |
| |
| Note that @samp{-break-list} will report a single list of watchpoints and |
| breakpoints inserted. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and |
| @samp{rwatch}. |
| |
| @subsubheading Example |
| |
| Setting a watchpoint on a variable in the @code{main} function: |
| |
| @smallexample |
| (gdb) |
| -break-watch x |
| ^done,wpt=@{number="2",exp="x"@} |
| (gdb) |
| -exec-continue |
| ^running |
| (gdb) |
| *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@}, |
| value=@{old="-268439212",new="55"@}, |
| frame=@{func="main",args=[],file="recursive2.c", |
| fullname="/home/foo/bar/recursive2.c",line="5"@} |
| (gdb) |
| @end smallexample |
| |
| Setting a watchpoint on a variable local to a function. @value{GDBN} will stop |
| the program execution twice: first for the variable changing value, then |
| for the watchpoint going out of scope. |
| |
| @smallexample |
| (gdb) |
| -break-watch C |
| ^done,wpt=@{number="5",exp="C"@} |
| (gdb) |
| -exec-continue |
| ^running |
| (gdb) |
| *stopped,reason="watchpoint-trigger", |
| wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@}, |
| frame=@{func="callee4",args=[], |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@} |
| (gdb) |
| -exec-continue |
| ^running |
| (gdb) |
| *stopped,reason="watchpoint-scope",wpnum="5", |
| frame=@{func="callee3",args=[@{name="strarg", |
| value="0x11940 \"A string argument.\""@}], |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@} |
| (gdb) |
| @end smallexample |
| |
| Listing breakpoints and watchpoints, at different points in the program |
| execution. Note that once the watchpoint goes out of scope, it is |
| deleted. |
| |
| @smallexample |
| (gdb) |
| -break-watch C |
| ^done,wpt=@{number="2",exp="C"@} |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="2",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x00010734",func="callee4", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@}, |
| bkpt=@{number="2",type="watchpoint",disp="keep", |
| enabled="y",addr="",what="C",times="0"@}]@} |
| (gdb) |
| -exec-continue |
| ^running |
| (gdb) |
| *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@}, |
| value=@{old="-276895068",new="3"@}, |
| frame=@{func="callee4",args=[], |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@} |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="2",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x00010734",func="callee4", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}, |
| bkpt=@{number="2",type="watchpoint",disp="keep", |
| enabled="y",addr="",what="C",times="-5"@}]@} |
| (gdb) |
| -exec-continue |
| ^running |
| ^done,reason="watchpoint-scope",wpnum="2", |
| frame=@{func="callee3",args=[@{name="strarg", |
| value="0x11940 \"A string argument.\""@}], |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@} |
| (gdb) |
| -break-list |
| ^done,BreakpointTable=@{nr_rows="1",nr_cols="6", |
| hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@}, |
| @{width="14",alignment="-1",col_name="type",colhdr="Type"@}, |
| @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@}, |
| @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@}, |
| @{width="10",alignment="-1",col_name="addr",colhdr="Address"@}, |
| @{width="40",alignment="2",col_name="what",colhdr="What"@}], |
| body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x00010734",func="callee4", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8", |
| times="1"@}]@} |
| (gdb) |
| @end smallexample |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Program Context |
| @section @sc{gdb/mi} Program Context |
| |
| @subheading The @code{-exec-arguments} Command |
| @findex -exec-arguments |
| |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-arguments @var{args} |
| @end smallexample |
| |
| Set the inferior program arguments, to be used in the next |
| @samp{-exec-run}. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{set args}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -exec-arguments -v word |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @ignore |
| @subheading The @code{-exec-show-arguments} Command |
| @findex -exec-show-arguments |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-show-arguments |
| @end smallexample |
| |
| Print the arguments of the program. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{show args}. |
| |
| @subsubheading Example |
| N.A. |
| @end ignore |
| |
| |
| @subheading The @code{-environment-cd} Command |
| @findex -environment-cd |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -environment-cd @var{pathdir} |
| @end smallexample |
| |
| Set @value{GDBN}'s working directory. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{cd}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-environment-directory} Command |
| @findex -environment-directory |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -environment-directory [ -r ] [ @var{pathdir} ]+ |
| @end smallexample |
| |
| Add directories @var{pathdir} to beginning of search path for source files. |
| If the @samp{-r} option is used, the search path is reset to the default |
| search path. If directories @var{pathdir} are supplied in addition to the |
| @samp{-r} option, the search path is first reset and then addition |
| occurs as normal. |
| Multiple directories may be specified, separated by blanks. Specifying |
| multiple directories in a single command |
| results in the directories added to the beginning of the |
| search path in the same order they were presented in the command. |
| If blanks are needed as |
| part of a directory name, double-quotes should be used around |
| the name. In the command output, the path will show up separated |
| by the system directory-separator character. The directory-separator |
| character must not be used |
| in any directory name. |
| If no directories are specified, the current search path is displayed. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{dir}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb |
| ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd" |
| (gdb) |
| -environment-directory "" |
| ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd" |
| (gdb) |
| -environment-directory -r /home/jjohnstn/src/gdb /usr/src |
| ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd" |
| (gdb) |
| -environment-directory -r |
| ^done,source-path="$cdir:$cwd" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-environment-path} Command |
| @findex -environment-path |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -environment-path [ -r ] [ @var{pathdir} ]+ |
| @end smallexample |
| |
| Add directories @var{pathdir} to beginning of search path for object files. |
| If the @samp{-r} option is used, the search path is reset to the original |
| search path that existed at gdb start-up. If directories @var{pathdir} are |
| supplied in addition to the |
| @samp{-r} option, the search path is first reset and then addition |
| occurs as normal. |
| Multiple directories may be specified, separated by blanks. Specifying |
| multiple directories in a single command |
| results in the directories added to the beginning of the |
| search path in the same order they were presented in the command. |
| If blanks are needed as |
| part of a directory name, double-quotes should be used around |
| the name. In the command output, the path will show up separated |
| by the system directory-separator character. The directory-separator |
| character must not be used |
| in any directory name. |
| If no directories are specified, the current path is displayed. |
| |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{path}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -environment-path |
| ^done,path="/usr/bin" |
| (gdb) |
| -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin |
| ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin" |
| (gdb) |
| -environment-path -r /usr/local/bin |
| ^done,path="/usr/local/bin:/usr/bin" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-environment-pwd} Command |
| @findex -environment-pwd |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -environment-pwd |
| @end smallexample |
| |
| Show the current working directory. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{pwd}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -environment-pwd |
| ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb" |
| (gdb) |
| @end smallexample |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Thread Commands |
| @section @sc{gdb/mi} Thread Commands |
| |
| |
| @subheading The @code{-thread-info} Command |
| @findex -thread-info |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -thread-info [ @var{thread-id} ] |
| @end smallexample |
| |
| Reports information about either a specific thread, if |
| the @var{thread-id} parameter is present, or about all |
| threads. When printing information about all threads, |
| also reports the current thread. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The @samp{info thread} command prints the same information |
| about all threads. |
| |
| @subsubheading Result |
| |
| The result is a list of threads. The following attributes are |
| defined for a given thread: |
| |
| @table @samp |
| @item current |
| This field exists only for the current thread. It has the value @samp{*}. |
| |
| @item id |
| The identifier that @value{GDBN} uses to refer to the thread. |
| |
| @item target-id |
| The identifier that the target uses to refer to the thread. |
| |
| @item details |
| Extra information about the thread, in a target-specific format. This |
| field is optional. |
| |
| @item name |
| The name of the thread. If the user specified a name using the |
| @code{thread name} command, then this name is given. Otherwise, if |
| @value{GDBN} can extract the thread name from the target, then that |
| name is given. If @value{GDBN} cannot find the thread name, then this |
| field is omitted. |
| |
| @item frame |
| The stack frame currently executing in the thread. |
| |
| @item state |
| The thread's state. The @samp{state} field may have the following |
| values: |
| |
| @table @code |
| @item stopped |
| The thread is stopped. Frame information is available for stopped |
| threads. |
| |
| @item running |
| The thread is running. There's no frame information for running |
| threads. |
| |
| @end table |
| |
| @item core |
| If @value{GDBN} can find the CPU core on which this thread is running, |
| then this field is the core identifier. This field is optional. |
| |
| @end table |
| |
| @subsubheading Example |
| |
| @smallexample |
| -thread-info |
| ^done,threads=[ |
| @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)", |
| frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall", |
| args=[]@},state="running"@}, |
| @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)", |
| frame=@{level="0",addr="0x0804891f",func="foo", |
| args=[@{name="i",value="10"@}], |
| file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}, |
| state="running"@}], |
| current-thread-id="1" |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-thread-list-ids} Command |
| @findex -thread-list-ids |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -thread-list-ids |
| @end smallexample |
| |
| Produces a list of the currently known @value{GDBN} thread ids. At the |
| end of the list it also prints the total number of such threads. |
| |
| This command is retained for historical reasons, the |
| @code{-thread-info} command should be used instead. |
| |
| @subsubheading @value{GDBN} Command |
| |
| Part of @samp{info threads} supplies the same information. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -thread-list-ids |
| ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@}, |
| current-thread-id="1",number-of-threads="3" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-thread-select} Command |
| @findex -thread-select |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -thread-select @var{threadnum} |
| @end smallexample |
| |
| Make @var{threadnum} the current thread. It prints the number of the new |
| current thread, and the topmost frame for that thread. |
| |
| This command is deprecated in favor of explicitly using the |
| @samp{--thread} option to each command. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{thread}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -exec-next |
| ^running |
| (gdb) |
| *stopped,reason="end-stepping-range",thread-id="2",line="187", |
| file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c" |
| (gdb) |
| -thread-list-ids |
| ^done, |
| thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@}, |
| number-of-threads="3" |
| (gdb) |
| -thread-select 3 |
| ^done,new-thread-id="3", |
| frame=@{level="0",func="vprintf", |
| args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@}, |
| @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@} |
| (gdb) |
| @end smallexample |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Ada Tasking Commands |
| @section @sc{gdb/mi} Ada Tasking Commands |
| |
| @subheading The @code{-ada-task-info} Command |
| @findex -ada-task-info |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -ada-task-info [ @var{task-id} ] |
| @end smallexample |
| |
| Reports information about either a specific Ada task, if the |
| @var{task-id} parameter is present, or about all Ada tasks. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The @samp{info tasks} command prints the same information |
| about all Ada tasks (@pxref{Ada Tasks}). |
| |
| @subsubheading Result |
| |
| The result is a table of Ada tasks. The following columns are |
| defined for each Ada task: |
| |
| @table @samp |
| @item current |
| This field exists only for the current thread. It has the value @samp{*}. |
| |
| @item id |
| The identifier that @value{GDBN} uses to refer to the Ada task. |
| |
| @item task-id |
| The identifier that the target uses to refer to the Ada task. |
| |
| @item thread-id |
| The identifier of the thread corresponding to the Ada task. |
| |
| This field should always exist, as Ada tasks are always implemented |
| on top of a thread. But if @value{GDBN} cannot find this corresponding |
| thread for any reason, the field is omitted. |
| |
| @item parent-id |
| This field exists only when the task was created by another task. |
| In this case, it provides the ID of the parent task. |
| |
| @item priority |
| The base priority of the task. |
| |
| @item state |
| The current state of the task. For a detailed description of the |
| possible states, see @ref{Ada Tasks}. |
| |
| @item name |
| The name of the task. |
| |
| @end table |
| |
| @subsubheading Example |
| |
| @smallexample |
| -ada-task-info |
| ^done,tasks=@{nr_rows="3",nr_cols="8", |
| hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@}, |
| @{width="3",alignment="1",col_name="id",colhdr="ID"@}, |
| @{width="9",alignment="1",col_name="task-id",colhdr="TID"@}, |
| @{width="4",alignment="1",col_name="thread-id",colhdr=""@}, |
| @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@}, |
| @{width="3",alignment="1",col_name="priority",colhdr="Pri"@}, |
| @{width="22",alignment="-1",col_name="state",colhdr="State"@}, |
| @{width="1",alignment="2",col_name="name",colhdr="Name"@}], |
| body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48", |
| state="Child Termination Wait",name="main_task"@}]@} |
| (gdb) |
| @end smallexample |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Program Execution |
| @section @sc{gdb/mi} Program Execution |
| |
| These are the asynchronous commands which generate the out-of-band |
| record @samp{*stopped}. Currently @value{GDBN} only really executes |
| asynchronously with remote targets and this interaction is mimicked in |
| other cases. |
| |
| @subheading The @code{-exec-continue} Command |
| @findex -exec-continue |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-continue [--reverse] [--all|--thread-group N] |
| @end smallexample |
| |
| Resumes the execution of the inferior program, which will continue |
| to execute until it reaches a debugger stop event. If the |
| @samp{--reverse} option is specified, execution resumes in reverse until |
| it reaches a stop event. Stop events may include |
| @itemize @bullet |
| @item |
| breakpoints or watchpoints |
| @item |
| signals or exceptions |
| @item |
| the end of the process (or its beginning under @samp{--reverse}) |
| @item |
| the end or beginning of a replay log if one is being used. |
| @end itemize |
| In all-stop mode (@pxref{All-Stop |
| Mode}), may resume only one thread, or all threads, depending on the |
| value of the @samp{scheduler-locking} variable. If @samp{--all} is |
| specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is |
| ignored in all-stop mode. If the @samp{--thread-group} options is |
| specified, then all threads in that thread group are resumed. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} corresponding is @samp{continue}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| -exec-continue |
| ^running |
| (gdb) |
| @@Hello world |
| *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{ |
| func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c", |
| line="13"@} |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-finish} Command |
| @findex -exec-finish |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-finish [--reverse] |
| @end smallexample |
| |
| Resumes the execution of the inferior program until the current |
| function is exited. Displays the results returned by the function. |
| If the @samp{--reverse} option is specified, resumes the reverse |
| execution of the inferior program until the point where current |
| function was called. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{finish}. |
| |
| @subsubheading Example |
| |
| Function returning @code{void}. |
| |
| @smallexample |
| -exec-finish |
| ^running |
| (gdb) |
| @@hello from foo |
| *stopped,reason="function-finished",frame=@{func="main",args=[], |
| file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@} |
| (gdb) |
| @end smallexample |
| |
| Function returning other than @code{void}. The name of the internal |
| @value{GDBN} variable storing the result is printed, together with the |
| value itself. |
| |
| @smallexample |
| -exec-finish |
| ^running |
| (gdb) |
| *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo", |
| args=[@{name="a",value="1"],@{name="b",value="9"@}@}, |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| gdb-result-var="$1",return-value="0" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-interrupt} Command |
| @findex -exec-interrupt |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-interrupt [--all|--thread-group N] |
| @end smallexample |
| |
| Interrupts the background execution of the target. Note how the token |
| associated with the stop message is the one for the execution command |
| that has been interrupted. The token for the interrupt itself only |
| appears in the @samp{^done} output. If the user is trying to |
| interrupt a non-running program, an error message will be printed. |
| |
| Note that when asynchronous execution is enabled, this command is |
| asynchronous just like other execution commands. That is, first the |
| @samp{^done} response will be printed, and the target stop will be |
| reported after that using the @samp{*stopped} notification. |
| |
| In non-stop mode, only the context thread is interrupted by default. |
| All threads (in all inferiors) will be interrupted if the |
| @samp{--all} option is specified. If the @samp{--thread-group} |
| option is specified, all threads in that group will be interrupted. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{interrupt}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| 111-exec-continue |
| 111^running |
| |
| (gdb) |
| 222-exec-interrupt |
| 222^done |
| (gdb) |
| 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt", |
| frame=@{addr="0x00010140",func="foo",args=[],file="try.c", |
| fullname="/home/foo/bar/try.c",line="13"@} |
| (gdb) |
| |
| (gdb) |
| -exec-interrupt |
| ^error,msg="mi_cmd_exec_interrupt: Inferior not executing." |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-exec-jump} Command |
| @findex -exec-jump |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-jump @var{location} |
| @end smallexample |
| |
| Resumes execution of the inferior program at the location specified by |
| parameter. @xref{Specify Location}, for a description of the |
| different forms of @var{location}. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{jump}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| -exec-jump foo.c:10 |
| *running,thread-id="all" |
| ^running |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-next} Command |
| @findex -exec-next |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-next [--reverse] |
| @end smallexample |
| |
| Resumes execution of the inferior program, stopping when the beginning |
| of the next source line is reached. |
| |
| If the @samp{--reverse} option is specified, resumes reverse execution |
| of the inferior program, stopping at the beginning of the previous |
| source line. If you issue this command on the first line of a |
| function, it will take you back to the caller of that function, to the |
| source line where the function was called. |
| |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{next}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| -exec-next |
| ^running |
| (gdb) |
| *stopped,reason="end-stepping-range",line="8",file="hello.c" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-next-instruction} Command |
| @findex -exec-next-instruction |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-next-instruction [--reverse] |
| @end smallexample |
| |
| Executes one machine instruction. If the instruction is a function |
| call, continues until the function returns. If the program stops at an |
| instruction in the middle of a source line, the address will be |
| printed as well. |
| |
| If the @samp{--reverse} option is specified, resumes reverse execution |
| of the inferior program, stopping at the previous instruction. If the |
| previously executed instruction was a return from another function, |
| it will continue to execute in reverse until the call to that function |
| (from the current stack frame) is reached. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{nexti}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -exec-next-instruction |
| ^running |
| |
| (gdb) |
| *stopped,reason="end-stepping-range", |
| addr="0x000100d4",line="5",file="hello.c" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-return} Command |
| @findex -exec-return |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-return |
| @end smallexample |
| |
| Makes current function return immediately. Doesn't execute the inferior. |
| Displays the new current frame. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{return}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| 200-break-insert callee4 |
| 200^done,bkpt=@{number="1",addr="0x00010734", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@} |
| (gdb) |
| 000-exec-run |
| 000^running |
| (gdb) |
| 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1", |
| frame=@{func="callee4",args=[], |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@} |
| (gdb) |
| 205-break-delete |
| 205^done |
| (gdb) |
| 111-exec-return |
| 111^done,frame=@{level="0",func="callee3", |
| args=[@{name="strarg", |
| value="0x11940 \"A string argument.\""@}], |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@} |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-run} Command |
| @findex -exec-run |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-run [--all | --thread-group N] |
| @end smallexample |
| |
| Starts execution of the inferior from the beginning. The inferior |
| executes until either a breakpoint is encountered or the program |
| exits. In the latter case the output will include an exit code, if |
| the program has exited exceptionally. |
| |
| When no option is specified, the current inferior is started. If the |
| @samp{--thread-group} option is specified, it should refer to a thread |
| group of type @samp{process}, and that thread group will be started. |
| If the @samp{--all} option is specified, then all inferiors will be started. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{run}. |
| |
| @subsubheading Examples |
| |
| @smallexample |
| (gdb) |
| -break-insert main |
| ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@} |
| (gdb) |
| -exec-run |
| ^running |
| (gdb) |
| *stopped,reason="breakpoint-hit",disp="keep",bkptno="1", |
| frame=@{func="main",args=[],file="recursive2.c", |
| fullname="/home/foo/bar/recursive2.c",line="4"@} |
| (gdb) |
| @end smallexample |
| |
| @noindent |
| Program exited normally: |
| |
| @smallexample |
| (gdb) |
| -exec-run |
| ^running |
| (gdb) |
| x = 55 |
| *stopped,reason="exited-normally" |
| (gdb) |
| @end smallexample |
| |
| @noindent |
| Program exited exceptionally: |
| |
| @smallexample |
| (gdb) |
| -exec-run |
| ^running |
| (gdb) |
| x = 55 |
| *stopped,reason="exited",exit-code="01" |
| (gdb) |
| @end smallexample |
| |
| Another way the program can terminate is if it receives a signal such as |
| @code{SIGINT}. In this case, @sc{gdb/mi} displays this: |
| |
| @smallexample |
| (gdb) |
| *stopped,reason="exited-signalled",signal-name="SIGINT", |
| signal-meaning="Interrupt" |
| @end smallexample |
| |
| |
| @c @subheading -exec-signal |
| |
| |
| @subheading The @code{-exec-step} Command |
| @findex -exec-step |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-step [--reverse] |
| @end smallexample |
| |
| Resumes execution of the inferior program, stopping when the beginning |
| of the next source line is reached, if the next source line is not a |
| function call. If it is, stop at the first instruction of the called |
| function. If the @samp{--reverse} option is specified, resumes reverse |
| execution of the inferior program, stopping at the beginning of the |
| previously executed source line. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{step}. |
| |
| @subsubheading Example |
| |
| Stepping into a function: |
| |
| @smallexample |
| -exec-step |
| ^running |
| (gdb) |
| *stopped,reason="end-stepping-range", |
| frame=@{func="foo",args=[@{name="a",value="10"@}, |
| @{name="b",value="0"@}],file="recursive2.c", |
| fullname="/home/foo/bar/recursive2.c",line="11"@} |
| (gdb) |
| @end smallexample |
| |
| Regular stepping: |
| |
| @smallexample |
| -exec-step |
| ^running |
| (gdb) |
| *stopped,reason="end-stepping-range",line="14",file="recursive2.c" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-step-instruction} Command |
| @findex -exec-step-instruction |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-step-instruction [--reverse] |
| @end smallexample |
| |
| Resumes the inferior which executes one machine instruction. If the |
| @samp{--reverse} option is specified, resumes reverse execution of the |
| inferior program, stopping at the previously executed instruction. |
| The output, once @value{GDBN} has stopped, will vary depending on |
| whether we have stopped in the middle of a source line or not. In the |
| former case, the address at which the program stopped will be printed |
| as well. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{stepi}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -exec-step-instruction |
| ^running |
| |
| (gdb) |
| *stopped,reason="end-stepping-range", |
| frame=@{func="foo",args=[],file="try.c", |
| fullname="/home/foo/bar/try.c",line="10"@} |
| (gdb) |
| -exec-step-instruction |
| ^running |
| |
| (gdb) |
| *stopped,reason="end-stepping-range", |
| frame=@{addr="0x000100f4",func="foo",args=[],file="try.c", |
| fullname="/home/foo/bar/try.c",line="10"@} |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-exec-until} Command |
| @findex -exec-until |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-until [ @var{location} ] |
| @end smallexample |
| |
| Executes the inferior until the @var{location} specified in the |
| argument is reached. If there is no argument, the inferior executes |
| until a source line greater than the current one is reached. The |
| reason for stopping in this case will be @samp{location-reached}. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{until}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -exec-until recursive2.c:6 |
| ^running |
| (gdb) |
| x = 55 |
| *stopped,reason="location-reached",frame=@{func="main",args=[], |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@} |
| (gdb) |
| @end smallexample |
| |
| @ignore |
| @subheading -file-clear |
| Is this going away???? |
| @end ignore |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Stack Manipulation |
| @section @sc{gdb/mi} Stack Manipulation Commands |
| |
| |
| @subheading The @code{-stack-info-frame} Command |
| @findex -stack-info-frame |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -stack-info-frame |
| @end smallexample |
| |
| Get info on the selected frame. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame} |
| (without arguments). |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -stack-info-frame |
| ^done,frame=@{level="1",addr="0x0001076c",func="callee3", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@} |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-stack-info-depth} Command |
| @findex -stack-info-depth |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -stack-info-depth [ @var{max-depth} ] |
| @end smallexample |
| |
| Return the depth of the stack. If the integer argument @var{max-depth} |
| is specified, do not count beyond @var{max-depth} frames. |
| |
| @subsubheading @value{GDBN} Command |
| |
| There's no equivalent @value{GDBN} command. |
| |
| @subsubheading Example |
| |
| For a stack with frame levels 0 through 11: |
| |
| @smallexample |
| (gdb) |
| -stack-info-depth |
| ^done,depth="12" |
| (gdb) |
| -stack-info-depth 4 |
| ^done,depth="4" |
| (gdb) |
| -stack-info-depth 12 |
| ^done,depth="12" |
| (gdb) |
| -stack-info-depth 11 |
| ^done,depth="11" |
| (gdb) |
| -stack-info-depth 13 |
| ^done,depth="12" |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-stack-list-arguments} Command |
| @findex -stack-list-arguments |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -stack-list-arguments @var{print-values} |
| [ @var{low-frame} @var{high-frame} ] |
| @end smallexample |
| |
| Display a list of the arguments for the frames between @var{low-frame} |
| and @var{high-frame} (inclusive). If @var{low-frame} and |
| @var{high-frame} are not provided, list the arguments for the whole |
| call stack. If the two arguments are equal, show the single frame |
| at the corresponding level. It is an error if @var{low-frame} is |
| larger than the actual number of frames. On the other hand, |
| @var{high-frame} may be larger than the actual number of frames, in |
| which case only existing frames will be returned. |
| |
| If @var{print-values} is 0 or @code{--no-values}, print only the names of |
| the variables; if it is 1 or @code{--all-values}, print also their |
| values; and if it is 2 or @code{--simple-values}, print the name, |
| type and value for simple data types, and the name and type for arrays, |
| structures and unions. |
| |
| Use of this command to obtain arguments in a single frame is |
| deprecated in favor of the @samp{-stack-list-variables} command. |
| |
| @subsubheading @value{GDBN} Command |
| |
| @value{GDBN} does not have an equivalent command. @code{gdbtk} has a |
| @samp{gdb_get_args} command which partially overlaps with the |
| functionality of @samp{-stack-list-arguments}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -stack-list-frames |
| ^done, |
| stack=[ |
| frame=@{level="0",addr="0x00010734",func="callee4", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}, |
| frame=@{level="1",addr="0x0001076c",func="callee3", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}, |
| frame=@{level="2",addr="0x0001078c",func="callee2", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@}, |
| frame=@{level="3",addr="0x000107b4",func="callee1", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@}, |
| frame=@{level="4",addr="0x000107e0",func="main", |
| file="../../../devo/gdb/testsuite/gdb.mi/basics.c", |
| fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}] |
| (gdb) |
| -stack-list-arguments 0 |
| ^done, |
| stack-args=[ |
| frame=@{level="0",args=[]@}, |
| frame=@{level="1",args=[name="strarg"]@}, |
| frame=@{level="2",args=[name="intarg",name="strarg"]@}, |
| frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@}, |
| frame=@{level="4",args=[]@}] |
| (gdb) |
| -stack-list-arguments 1 |
| ^done, |
| stack-args=[ |
| frame=@{level="0",args=[]@}, |
| frame=@{level="1", |
| args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@}, |
| frame=@{level="2",args=[ |
| @{name="intarg",value="2"@}, |
| @{name="strarg",value="0x11940 \"A string argument.\""@}]@}, |
| @{frame=@{level="3",args=[ |
| @{name="intarg",value="2"@}, |
| @{name="strarg",value="0x11940 \"A string argument.\""@}, |
| @{name="fltarg",value="3.5"@}]@}, |
| frame=@{level="4",args=[]@}] |
| (gdb) |
| -stack-list-arguments 0 2 2 |
| ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}] |
| (gdb) |
| -stack-list-arguments 1 2 2 |
| ^done,stack-args=[frame=@{level="2", |
| args=[@{name="intarg",value="2"@}, |
| @{name="strarg",value="0x11940 \"A string argument.\""@}]@}] |
| (gdb) |
| @end smallexample |
| |
| @c @subheading -stack-list-exception-handlers |
| |
| |
| @subheading The @code{-stack-list-frames} Command |
| @findex -stack-list-frames |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -stack-list-frames [ @var{low-frame} @var{high-frame} ] |
| @end smallexample |
| |
| List the frames currently on the stack. For each frame it displays the |
| following info: |
| |
| @table @samp |
| @item @var{level} |
| The frame number, 0 being the topmost frame, i.e., the innermost function. |
| @item @var{addr} |
| The @code{$pc} value for that frame. |
| @item @var{func} |
| Function name. |
| @item @var{file} |
| File name of the source file where the function lives. |
| @item @var{fullname} |
| The full file name of the source file where the function lives. |
| @item @var{line} |
| Line number corresponding to the @code{$pc}. |
| @item @var{from} |
| The shared library where this function is defined. This is only given |
| if the frame's function is not known. |
| @end table |
| |
| If invoked without arguments, this command prints a backtrace for the |
| whole stack. If given two integer arguments, it shows the frames whose |
| levels are between the two arguments (inclusive). If the two arguments |
| are equal, it shows the single frame at the corresponding level. It is |
| an error if @var{low-frame} is larger than the actual number of |
| frames. On the other hand, @var{high-frame} may be larger than the |
| actual number of frames, in which case only existing frames will be returned. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}. |
| |
| @subsubheading Example |
| |
| Full stack backtrace: |
| |
| @smallexample |
| (gdb) |
| -stack-list-frames |
| ^done,stack= |
| [frame=@{level="0",addr="0x0001076c",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@}, |
| frame=@{level="1",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="2",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="3",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="4",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="5",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="6",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="7",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="8",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="9",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="10",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="11",addr="0x00010738",func="main", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}] |
| (gdb) |
| @end smallexample |
| |
| Show frames between @var{low_frame} and @var{high_frame}: |
| |
| @smallexample |
| (gdb) |
| -stack-list-frames 3 5 |
| ^done,stack= |
| [frame=@{level="3",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="4",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}, |
| frame=@{level="5",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}] |
| (gdb) |
| @end smallexample |
| |
| Show a single frame: |
| |
| @smallexample |
| (gdb) |
| -stack-list-frames 3 3 |
| ^done,stack= |
| [frame=@{level="3",addr="0x000107a4",func="foo", |
| file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}] |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-stack-list-locals} Command |
| @findex -stack-list-locals |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -stack-list-locals @var{print-values} |
| @end smallexample |
| |
| Display the local variable names for the selected frame. If |
| @var{print-values} is 0 or @code{--no-values}, print only the names of |
| the variables; if it is 1 or @code{--all-values}, print also their |
| values; and if it is 2 or @code{--simple-values}, print the name, |
| type and value for simple data types, and the name and type for arrays, |
| structures and unions. In this last case, a frontend can immediately |
| display the value of simple data types and create variable objects for |
| other data types when the user wishes to explore their values in |
| more detail. |
| |
| This command is deprecated in favor of the |
| @samp{-stack-list-variables} command. |
| |
| @subsubheading @value{GDBN} Command |
| |
| @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -stack-list-locals 0 |
| ^done,locals=[name="A",name="B",name="C"] |
| (gdb) |
| -stack-list-locals --all-values |
| ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@}, |
| @{name="C",value="@{1, 2, 3@}"@}] |
| -stack-list-locals --simple-values |
| ^done,locals=[@{name="A",type="int",value="1"@}, |
| @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}] |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-stack-list-variables} Command |
| @findex -stack-list-variables |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -stack-list-variables @var{print-values} |
| @end smallexample |
| |
| Display the names of local variables and function arguments for the selected frame. If |
| @var{print-values} is 0 or @code{--no-values}, print only the names of |
| the variables; if it is 1 or @code{--all-values}, print also their |
| values; and if it is 2 or @code{--simple-values}, print the name, |
| type and value for simple data types, and the name and type for arrays, |
| structures and unions. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -stack-list-variables --thread 1 --frame 0 --all-values |
| ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}] |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-stack-select-frame} Command |
| @findex -stack-select-frame |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -stack-select-frame @var{framenum} |
| @end smallexample |
| |
| Change the selected frame. Select a different frame @var{framenum} on |
| the stack. |
| |
| This command in deprecated in favor of passing the @samp{--frame} |
| option to every command. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} commands are @samp{frame}, @samp{up}, |
| @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -stack-select-frame 2 |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Variable Objects |
| @section @sc{gdb/mi} Variable Objects |
| |
| @ignore |
| |
| @subheading Motivation for Variable Objects in @sc{gdb/mi} |
| |
| For the implementation of a variable debugger window (locals, watched |
| expressions, etc.), we are proposing the adaptation of the existing code |
| used by @code{Insight}. |
| |
| The two main reasons for that are: |
| |
| @enumerate 1 |
| @item |
| It has been proven in practice (it is already on its second generation). |
| |
| @item |
| It will shorten development time (needless to say how important it is |
| now). |
| @end enumerate |
| |
| The original interface was designed to be used by Tcl code, so it was |
| slightly changed so it could be used through @sc{gdb/mi}. This section |
| describes the @sc{gdb/mi} operations that will be available and gives some |
| hints about their use. |
| |
| @emph{Note}: In addition to the set of operations described here, we |
| expect the @sc{gui} implementation of a variable window to require, at |
| least, the following operations: |
| |
| @itemize @bullet |
| @item @code{-gdb-show} @code{output-radix} |
| @item @code{-stack-list-arguments} |
| @item @code{-stack-list-locals} |
| @item @code{-stack-select-frame} |
| @end itemize |
| |
| @end ignore |
| |
| @subheading Introduction to Variable Objects |
| |
| @cindex variable objects in @sc{gdb/mi} |
| |
| Variable objects are "object-oriented" MI interface for examining and |
| changing values of expressions. Unlike some other MI interfaces that |
| work with expressions, variable objects are specifically designed for |
| simple and efficient presentation in the frontend. A variable object |
| is identified by string name. When a variable object is created, the |
| frontend specifies the expression for that variable object. The |
| expression can be a simple variable, or it can be an arbitrary complex |
| expression, and can even involve CPU registers. After creating a |
| variable object, the frontend can invoke other variable object |
| operations---for example to obtain or change the value of a variable |
| object, or to change display format. |
| |
| Variable objects have hierarchical tree structure. Any variable object |
| that corresponds to a composite type, such as structure in C, has |
| a number of child variable objects, for example corresponding to each |
| element of a structure. A child variable object can itself have |
| children, recursively. Recursion ends when we reach |
| leaf variable objects, which always have built-in types. Child variable |
| objects are created only by explicit request, so if a frontend |
| is not interested in the children of a particular variable object, no |
| child will be created. |
| |
| For a leaf variable object it is possible to obtain its value as a |
| string, or set the value from a string. String value can be also |
| obtained for a non-leaf variable object, but it's generally a string |
| that only indicates the type of the object, and does not list its |
| contents. Assignment to a non-leaf variable object is not allowed. |
| |
| A frontend does not need to read the values of all variable objects each time |
| the program stops. Instead, MI provides an update command that lists all |
| variable objects whose values has changed since the last update |
| operation. This considerably reduces the amount of data that must |
| be transferred to the frontend. As noted above, children variable |
| objects are created on demand, and only leaf variable objects have a |
| real value. As result, gdb will read target memory only for leaf |
| variables that frontend has created. |
| |
| The automatic update is not always desirable. For example, a frontend |
| might want to keep a value of some expression for future reference, |
| and never update it. For another example, fetching memory is |
| relatively slow for embedded targets, so a frontend might want |
| to disable automatic update for the variables that are either not |
| visible on the screen, or ``closed''. This is possible using so |
| called ``frozen variable objects''. Such variable objects are never |
| implicitly updated. |
| |
| Variable objects can be either @dfn{fixed} or @dfn{floating}. For the |
| fixed variable object, the expression is parsed when the variable |
| object is created, including associating identifiers to specific |
| variables. The meaning of expression never changes. For a floating |
| variable object the values of variables whose names appear in the |
| expressions are re-evaluated every time in the context of the current |
| frame. Consider this example: |
| |
| @smallexample |
| void do_work(...) |
| @{ |
| struct work_state state; |
| |
| if (...) |
| do_work(...); |
| @} |
| @end smallexample |
| |
| If a fixed variable object for the @code{state} variable is created in |
| this function, and we enter the recursive call, the variable |
| object will report the value of @code{state} in the top-level |
| @code{do_work} invocation. On the other hand, a floating variable |
| object will report the value of @code{state} in the current frame. |
| |
| If an expression specified when creating a fixed variable object |
| refers to a local variable, the variable object becomes bound to the |
| thread and frame in which the variable object is created. When such |
| variable object is updated, @value{GDBN} makes sure that the |
| thread/frame combination the variable object is bound to still exists, |
| and re-evaluates the variable object in context of that thread/frame. |
| |
| The following is the complete set of @sc{gdb/mi} operations defined to |
| access this functionality: |
| |
| @multitable @columnfractions .4 .6 |
| @item @strong{Operation} |
| @tab @strong{Description} |
| |
| @item @code{-enable-pretty-printing} |
| @tab enable Python-based pretty-printing |
| @item @code{-var-create} |
| @tab create a variable object |
| @item @code{-var-delete} |
| @tab delete the variable object and/or its children |
| @item @code{-var-set-format} |
| @tab set the display format of this variable |
| @item @code{-var-show-format} |
| @tab show the display format of this variable |
| @item @code{-var-info-num-children} |
| @tab tells how many children this object has |
| @item @code{-var-list-children} |
| @tab return a list of the object's children |
| @item @code{-var-info-type} |
| @tab show the type of this variable object |
| @item @code{-var-info-expression} |
| @tab print parent-relative expression that this variable object represents |
| @item @code{-var-info-path-expression} |
| @tab print full expression that this variable object represents |
| @item @code{-var-show-attributes} |
| @tab is this variable editable? does it exist here? |
| @item @code{-var-evaluate-expression} |
| @tab get the value of this variable |
| @item @code{-var-assign} |
| @tab set the value of this variable |
| @item @code{-var-update} |
| @tab update the variable and its children |
| @item @code{-var-set-frozen} |
| @tab set frozeness attribute |
| @item @code{-var-set-update-range} |
| @tab set range of children to display on update |
| @end multitable |
| |
| In the next subsection we describe each operation in detail and suggest |
| how it can be used. |
| |
| @subheading Description And Use of Operations on Variable Objects |
| |
| @subheading The @code{-enable-pretty-printing} Command |
| @findex -enable-pretty-printing |
| |
| @smallexample |
| -enable-pretty-printing |
| @end smallexample |
| |
| @value{GDBN} allows Python-based visualizers to affect the output of the |
| MI variable object commands. However, because there was no way to |
| implement this in a fully backward-compatible way, a front end must |
| request that this functionality be enabled. |
| |
| Once enabled, this feature cannot be disabled. |
| |
| Note that if Python support has not been compiled into @value{GDBN}, |
| this command will still succeed (and do nothing). |
| |
| This feature is currently (as of @value{GDBN} 7.0) experimental, and |
| may work differently in future versions of @value{GDBN}. |
| |
| @subheading The @code{-var-create} Command |
| @findex -var-create |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-create @{@var{name} | "-"@} |
| @{@var{frame-addr} | "*" | "@@"@} @var{expression} |
| @end smallexample |
| |
| This operation creates a variable object, which allows the monitoring of |
| a variable, the result of an expression, a memory cell or a CPU |
| register. |
| |
| The @var{name} parameter is the string by which the object can be |
| referenced. It must be unique. If @samp{-} is specified, the varobj |
| system will generate a string ``varNNNNNN'' automatically. It will be |
| unique provided that one does not specify @var{name} of that format. |
| The command fails if a duplicate name is found. |
| |
| The frame under which the expression should be evaluated can be |
| specified by @var{frame-addr}. A @samp{*} indicates that the current |
| frame should be used. A @samp{@@} indicates that a floating variable |
| object must be created. |
| |
| @var{expression} is any expression valid on the current language set (must not |
| begin with a @samp{*}), or one of the following: |
| |
| @itemize @bullet |
| @item |
| @samp{*@var{addr}}, where @var{addr} is the address of a memory cell |
| |
| @item |
| @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD) |
| |
| @item |
| @samp{$@var{regname}} --- a CPU register name |
| @end itemize |
| |
| @cindex dynamic varobj |
| A varobj's contents may be provided by a Python-based pretty-printer. In this |
| case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs |
| have slightly different semantics in some cases. If the |
| @code{-enable-pretty-printing} command is not sent, then @value{GDBN} |
| will never create a dynamic varobj. This ensures backward |
| compatibility for existing clients. |
| |
| @subsubheading Result |
| |
| This operation returns attributes of the newly-created varobj. These |
| are: |
| |
| @table @samp |
| @item name |
| The name of the varobj. |
| |
| @item numchild |
| The number of children of the varobj. This number is not necessarily |
| reliable for a dynamic varobj. Instead, you must examine the |
| @samp{has_more} attribute. |
| |
| @item value |
| The varobj's scalar value. For a varobj whose type is some sort of |
| aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value |
| will not be interesting. |
| |
| @item type |
| The varobj's type. This is a string representation of the type, as |
| would be printed by the @value{GDBN} CLI. If @samp{print object} |
| (@pxref{Print Settings, set print object}) is set to @code{on}, the |
| @emph{actual} (derived) type of the object is shown rather than the |
| @emph{declared} one. |
| |
| @item thread-id |
| If a variable object is bound to a specific thread, then this is the |
| thread's identifier. |
| |
| @item has_more |
| For a dynamic varobj, this indicates whether there appear to be any |
| children available. For a non-dynamic varobj, this will be 0. |
| |
| @item dynamic |
| This attribute will be present and have the value @samp{1} if the |
| varobj is a dynamic varobj. If the varobj is not a dynamic varobj, |
| then this attribute will not be present. |
| |
| @item displayhint |
| A dynamic varobj can supply a display hint to the front end. The |
| value comes directly from the Python pretty-printer object's |
| @code{display_hint} method. @xref{Pretty Printing API}. |
| @end table |
| |
| Typical output will look like this: |
| |
| @smallexample |
| name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}", |
| has_more="@var{has_more}" |
| @end smallexample |
| |
| |
| @subheading The @code{-var-delete} Command |
| @findex -var-delete |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-delete [ -c ] @var{name} |
| @end smallexample |
| |
| Deletes a previously created variable object and all of its children. |
| With the @samp{-c} option, just deletes the children. |
| |
| Returns an error if the object @var{name} is not found. |
| |
| |
| @subheading The @code{-var-set-format} Command |
| @findex -var-set-format |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-set-format @var{name} @var{format-spec} |
| @end smallexample |
| |
| Sets the output format for the value of the object @var{name} to be |
| @var{format-spec}. |
| |
| @anchor{-var-set-format} |
| The syntax for the @var{format-spec} is as follows: |
| |
| @smallexample |
| @var{format-spec} @expansion{} |
| @{binary | decimal | hexadecimal | octal | natural@} |
| @end smallexample |
| |
| The natural format is the default format choosen automatically |
| based on the variable type (like decimal for an @code{int}, hex |
| for pointers, etc.). |
| |
| For a variable with children, the format is set only on the |
| variable itself, and the children are not affected. |
| |
| @subheading The @code{-var-show-format} Command |
| @findex -var-show-format |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-show-format @var{name} |
| @end smallexample |
| |
| Returns the format used to display the value of the object @var{name}. |
| |
| @smallexample |
| @var{format} @expansion{} |
| @var{format-spec} |
| @end smallexample |
| |
| |
| @subheading The @code{-var-info-num-children} Command |
| @findex -var-info-num-children |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-info-num-children @var{name} |
| @end smallexample |
| |
| Returns the number of children of a variable object @var{name}: |
| |
| @smallexample |
| numchild=@var{n} |
| @end smallexample |
| |
| Note that this number is not completely reliable for a dynamic varobj. |
| It will return the current number of children, but more children may |
| be available. |
| |
| |
| @subheading The @code{-var-list-children} Command |
| @findex -var-list-children |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}] |
| @end smallexample |
| @anchor{-var-list-children} |
| |
| Return a list of the children of the specified variable object and |
| create variable objects for them, if they do not already exist. With |
| a single argument or if @var{print-values} has a value of 0 or |
| @code{--no-values}, print only the names of the variables; if |
| @var{print-values} is 1 or @code{--all-values}, also print their |
| values; and if it is 2 or @code{--simple-values} print the name and |
| value for simple data types and just the name for arrays, structures |
| and unions. |
| |
| @var{from} and @var{to}, if specified, indicate the range of children |
| to report. If @var{from} or @var{to} is less than zero, the range is |
| reset and all children will be reported. Otherwise, children starting |
| at @var{from} (zero-based) and up to and excluding @var{to} will be |
| reported. |
| |
| If a child range is requested, it will only affect the current call to |
| @code{-var-list-children}, but not future calls to @code{-var-update}. |
| For this, you must instead use @code{-var-set-update-range}. The |
| intent of this approach is to enable a front end to implement any |
| update approach it likes; for example, scrolling a view may cause the |
| front end to request more children with @code{-var-list-children}, and |
| then the front end could call @code{-var-set-update-range} with a |
| different range to ensure that future updates are restricted to just |
| the visible items. |
| |
| For each child the following results are returned: |
| |
| @table @var |
| |
| @item name |
| Name of the variable object created for this child. |
| |
| @item exp |
| The expression to be shown to the user by the front end to designate this child. |
| For example this may be the name of a structure member. |
| |
| For a dynamic varobj, this value cannot be used to form an |
| expression. There is no way to do this at all with a dynamic varobj. |
| |
| For C/C@t{++} structures there are several pseudo children returned to |
| designate access qualifiers. For these pseudo children @var{exp} is |
| @samp{public}, @samp{private}, or @samp{protected}. In this case the |
| type and value are not present. |
| |
| A dynamic varobj will not report the access qualifying |
| pseudo-children, regardless of the language. This information is not |
| available at all with a dynamic varobj. |
| |
| @item numchild |
| Number of children this child has. For a dynamic varobj, this will be |
| 0. |
| |
| @item type |
| The type of the child. If @samp{print object} |
| (@pxref{Print Settings, set print object}) is set to @code{on}, the |
| @emph{actual} (derived) type of the object is shown rather than the |
| @emph{declared} one. |
| |
| @item value |
| If values were requested, this is the value. |
| |
| @item thread-id |
| If this variable object is associated with a thread, this is the thread id. |
| Otherwise this result is not present. |
| |
| @item frozen |
| If the variable object is frozen, this variable will be present with a value of 1. |
| @end table |
| |
| The result may have its own attributes: |
| |
| @table @samp |
| @item displayhint |
| A dynamic varobj can supply a display hint to the front end. The |
| value comes directly from the Python pretty-printer object's |
| @code{display_hint} method. @xref{Pretty Printing API}. |
| |
| @item has_more |
| This is an integer attribute which is nonzero if there are children |
| remaining after the end of the selected range. |
| @end table |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -var-list-children n |
| ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp}, |
| numchild=@var{n},type=@var{type}@},@r{(repeats N times)}] |
| (gdb) |
| -var-list-children --all-values n |
| ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp}, |
| numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}] |
| @end smallexample |
| |
| |
| @subheading The @code{-var-info-type} Command |
| @findex -var-info-type |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-info-type @var{name} |
| @end smallexample |
| |
| Returns the type of the specified variable @var{name}. The type is |
| returned as a string in the same format as it is output by the |
| @value{GDBN} CLI: |
| |
| @smallexample |
| type=@var{typename} |
| @end smallexample |
| |
| |
| @subheading The @code{-var-info-expression} Command |
| @findex -var-info-expression |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-info-expression @var{name} |
| @end smallexample |
| |
| Returns a string that is suitable for presenting this |
| variable object in user interface. The string is generally |
| not valid expression in the current language, and cannot be evaluated. |
| |
| For example, if @code{a} is an array, and variable object |
| @code{A} was created for @code{a}, then we'll get this output: |
| |
| @smallexample |
| (gdb) -var-info-expression A.1 |
| ^done,lang="C",exp="1" |
| @end smallexample |
| |
| @noindent |
| Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}. |
| |
| Note that the output of the @code{-var-list-children} command also |
| includes those expressions, so the @code{-var-info-expression} command |
| is of limited use. |
| |
| @subheading The @code{-var-info-path-expression} Command |
| @findex -var-info-path-expression |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-info-path-expression @var{name} |
| @end smallexample |
| |
| Returns an expression that can be evaluated in the current |
| context and will yield the same value that a variable object has. |
| Compare this with the @code{-var-info-expression} command, which |
| result can be used only for UI presentation. Typical use of |
| the @code{-var-info-path-expression} command is creating a |
| watchpoint from a variable object. |
| |
| This command is currently not valid for children of a dynamic varobj, |
| and will give an error when invoked on one. |
| |
| For example, suppose @code{C} is a C@t{++} class, derived from class |
| @code{Base}, and that the @code{Base} class has a member called |
| @code{m_size}. Assume a variable @code{c} is has the type of |
| @code{C} and a variable object @code{C} was created for variable |
| @code{c}. Then, we'll get this output: |
| @smallexample |
| (gdb) -var-info-path-expression C.Base.public.m_size |
| ^done,path_expr=((Base)c).m_size) |
| @end smallexample |
| |
| @subheading The @code{-var-show-attributes} Command |
| @findex -var-show-attributes |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-show-attributes @var{name} |
| @end smallexample |
| |
| List attributes of the specified variable object @var{name}: |
| |
| @smallexample |
| status=@var{attr} [ ( ,@var{attr} )* ] |
| @end smallexample |
| |
| @noindent |
| where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}. |
| |
| @subheading The @code{-var-evaluate-expression} Command |
| @findex -var-evaluate-expression |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-evaluate-expression [-f @var{format-spec}] @var{name} |
| @end smallexample |
| |
| Evaluates the expression that is represented by the specified variable |
| object and returns its value as a string. The format of the string |
| can be specified with the @samp{-f} option. The possible values of |
| this option are the same as for @code{-var-set-format} |
| (@pxref{-var-set-format}). If the @samp{-f} option is not specified, |
| the current display format will be used. The current display format |
| can be changed using the @code{-var-set-format} command. |
| |
| @smallexample |
| value=@var{value} |
| @end smallexample |
| |
| Note that one must invoke @code{-var-list-children} for a variable |
| before the value of a child variable can be evaluated. |
| |
| @subheading The @code{-var-assign} Command |
| @findex -var-assign |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-assign @var{name} @var{expression} |
| @end smallexample |
| |
| Assigns the value of @var{expression} to the variable object specified |
| by @var{name}. The object must be @samp{editable}. If the variable's |
| value is altered by the assign, the variable will show up in any |
| subsequent @code{-var-update} list. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -var-assign var1 3 |
| ^done,value="3" |
| (gdb) |
| -var-update * |
| ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}] |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-var-update} Command |
| @findex -var-update |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-update [@var{print-values}] @{@var{name} | "*"@} |
| @end smallexample |
| |
| Reevaluate the expressions corresponding to the variable object |
| @var{name} and all its direct and indirect children, and return the |
| list of variable objects whose values have changed; @var{name} must |
| be a root variable object. Here, ``changed'' means that the result of |
| @code{-var-evaluate-expression} before and after the |
| @code{-var-update} is different. If @samp{*} is used as the variable |
| object names, all existing variable objects are updated, except |
| for frozen ones (@pxref{-var-set-frozen}). The option |
| @var{print-values} determines whether both names and values, or just |
| names are printed. The possible values of this option are the same |
| as for @code{-var-list-children} (@pxref{-var-list-children}). It is |
| recommended to use the @samp{--all-values} option, to reduce the |
| number of MI commands needed on each program stop. |
| |
| With the @samp{*} parameter, if a variable object is bound to a |
| currently running thread, it will not be updated, without any |
| diagnostic. |
| |
| If @code{-var-set-update-range} was previously used on a varobj, then |
| only the selected range of children will be reported. |
| |
| @code{-var-update} reports all the changed varobjs in a tuple named |
| @samp{changelist}. |
| |
| Each item in the change list is itself a tuple holding: |
| |
| @table @samp |
| @item name |
| The name of the varobj. |
| |
| @item value |
| If values were requested for this update, then this field will be |
| present and will hold the value of the varobj. |
| |
| @item in_scope |
| @anchor{-var-update} |
| This field is a string which may take one of three values: |
| |
| @table @code |
| @item "true" |
| The variable object's current value is valid. |
| |
| @item "false" |
| The variable object does not currently hold a valid value but it may |
| hold one in the future if its associated expression comes back into |
| scope. |
| |
| @item "invalid" |
| The variable object no longer holds a valid value. |
| This can occur when the executable file being debugged has changed, |
| either through recompilation or by using the @value{GDBN} @code{file} |
| command. The front end should normally choose to delete these variable |
| objects. |
| @end table |
| |
| In the future new values may be added to this list so the front should |
| be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}. |
| |
| @item type_changed |
| This is only present if the varobj is still valid. If the type |
| changed, then this will be the string @samp{true}; otherwise it will |
| be @samp{false}. |
| |
| When a varobj's type changes, its children are also likely to have |
| become incorrect. Therefore, the varobj's children are automatically |
| deleted when this attribute is @samp{true}. Also, the varobj's update |
| range, when set using the @code{-var-set-update-range} command, is |
| unset. |
| |
| @item new_type |
| If the varobj's type changed, then this field will be present and will |
| hold the new type. |
| |
| @item new_num_children |
| For a dynamic varobj, if the number of children changed, or if the |
| type changed, this will be the new number of children. |
| |
| The @samp{numchild} field in other varobj responses is generally not |
| valid for a dynamic varobj -- it will show the number of children that |
| @value{GDBN} knows about, but because dynamic varobjs lazily |
| instantiate their children, this will not reflect the number of |
| children which may be available. |
| |
| The @samp{new_num_children} attribute only reports changes to the |
| number of children known by @value{GDBN}. This is the only way to |
| detect whether an update has removed children (which necessarily can |
| only happen at the end of the update range). |
| |
| @item displayhint |
| The display hint, if any. |
| |
| @item has_more |
| This is an integer value, which will be 1 if there are more children |
| available outside the varobj's update range. |
| |
| @item dynamic |
| This attribute will be present and have the value @samp{1} if the |
| varobj is a dynamic varobj. If the varobj is not a dynamic varobj, |
| then this attribute will not be present. |
| |
| @item new_children |
| If new children were added to a dynamic varobj within the selected |
| update range (as set by @code{-var-set-update-range}), then they will |
| be listed in this attribute. |
| @end table |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -var-assign var1 3 |
| ^done,value="3" |
| (gdb) |
| -var-update --all-values var1 |
| ^done,changelist=[@{name="var1",value="3",in_scope="true", |
| type_changed="false"@}] |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-var-set-frozen} Command |
| @findex -var-set-frozen |
| @anchor{-var-set-frozen} |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-set-frozen @var{name} @var{flag} |
| @end smallexample |
| |
| Set the frozenness flag on the variable object @var{name}. The |
| @var{flag} parameter should be either @samp{1} to make the variable |
| frozen or @samp{0} to make it unfrozen. If a variable object is |
| frozen, then neither itself, nor any of its children, are |
| implicitly updated by @code{-var-update} of |
| a parent variable or by @code{-var-update *}. Only |
| @code{-var-update} of the variable itself will update its value and |
| values of its children. After a variable object is unfrozen, it is |
| implicitly updated by all subsequent @code{-var-update} operations. |
| Unfreezing a variable does not update it, only subsequent |
| @code{-var-update} does. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -var-set-frozen V 1 |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-var-set-update-range} command |
| @findex -var-set-update-range |
| @anchor{-var-set-update-range} |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-set-update-range @var{name} @var{from} @var{to} |
| @end smallexample |
| |
| Set the range of children to be returned by future invocations of |
| @code{-var-update}. |
| |
| @var{from} and @var{to} indicate the range of children to report. If |
| @var{from} or @var{to} is less than zero, the range is reset and all |
| children will be reported. Otherwise, children starting at @var{from} |
| (zero-based) and up to and excluding @var{to} will be reported. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -var-set-update-range V 1 2 |
| ^done |
| @end smallexample |
| |
| @subheading The @code{-var-set-visualizer} command |
| @findex -var-set-visualizer |
| @anchor{-var-set-visualizer} |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -var-set-visualizer @var{name} @var{visualizer} |
| @end smallexample |
| |
| Set a visualizer for the variable object @var{name}. |
| |
| @var{visualizer} is the visualizer to use. The special value |
| @samp{None} means to disable any visualizer in use. |
| |
| If not @samp{None}, @var{visualizer} must be a Python expression. |
| This expression must evaluate to a callable object which accepts a |
| single argument. @value{GDBN} will call this object with the value of |
| the varobj @var{name} as an argument (this is done so that the same |
| Python pretty-printing code can be used for both the CLI and MI). |
| When called, this object must return an object which conforms to the |
| pretty-printing interface (@pxref{Pretty Printing API}). |
| |
| The pre-defined function @code{gdb.default_visualizer} may be used to |
| select a visualizer by following the built-in process |
| (@pxref{Selecting Pretty-Printers}). This is done automatically when |
| a varobj is created, and so ordinarily is not needed. |
| |
| This feature is only available if Python support is enabled. The MI |
| command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands}) |
| can be used to check this. |
| |
| @subsubheading Example |
| |
| Resetting the visualizer: |
| |
| @smallexample |
| (gdb) |
| -var-set-visualizer V None |
| ^done |
| @end smallexample |
| |
| Reselecting the default (type-based) visualizer: |
| |
| @smallexample |
| (gdb) |
| -var-set-visualizer V gdb.default_visualizer |
| ^done |
| @end smallexample |
| |
| Suppose @code{SomeClass} is a visualizer class. A lambda expression |
| can be used to instantiate this class for a varobj: |
| |
| @smallexample |
| (gdb) |
| -var-set-visualizer V "lambda val: SomeClass()" |
| ^done |
| @end smallexample |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Data Manipulation |
| @section @sc{gdb/mi} Data Manipulation |
| |
| @cindex data manipulation, in @sc{gdb/mi} |
| @cindex @sc{gdb/mi}, data manipulation |
| This section describes the @sc{gdb/mi} commands that manipulate data: |
| examine memory and registers, evaluate expressions, etc. |
| |
| @c REMOVED FROM THE INTERFACE. |
| @c @subheading -data-assign |
| @c Change the value of a program variable. Plenty of side effects. |
| @c @subsubheading GDB Command |
| @c set variable |
| @c @subsubheading Example |
| @c N.A. |
| |
| @subheading The @code{-data-disassemble} Command |
| @findex -data-disassemble |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-disassemble |
| [ -s @var{start-addr} -e @var{end-addr} ] |
| | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ] |
| -- @var{mode} |
| @end smallexample |
| |
| @noindent |
| Where: |
| |
| @table @samp |
| @item @var{start-addr} |
| is the beginning address (or @code{$pc}) |
| @item @var{end-addr} |
| is the end address |
| @item @var{filename} |
| is the name of the file to disassemble |
| @item @var{linenum} |
| is the line number to disassemble around |
| @item @var{lines} |
| is the number of disassembly lines to be produced. If it is -1, |
| the whole function will be disassembled, in case no @var{end-addr} is |
| specified. If @var{end-addr} is specified as a non-zero value, and |
| @var{lines} is lower than the number of disassembly lines between |
| @var{start-addr} and @var{end-addr}, only @var{lines} lines are |
| displayed; if @var{lines} is higher than the number of lines between |
| @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr} |
| are displayed. |
| @item @var{mode} |
| is either 0 (meaning only disassembly), 1 (meaning mixed source and |
| disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning |
| mixed source and disassembly with raw opcodes). |
| @end table |
| |
| @subsubheading Result |
| |
| The output for each instruction is composed of four fields: |
| |
| @itemize @bullet |
| @item Address |
| @item Func-name |
| @item Offset |
| @item Instruction |
| @end itemize |
| |
| Note that whatever included in the instruction field, is not manipulated |
| directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format. |
| |
| @subsubheading @value{GDBN} Command |
| |
| There's no direct mapping from this command to the CLI. |
| |
| @subsubheading Example |
| |
| Disassemble from the current value of @code{$pc} to @code{$pc + 20}: |
| |
| @smallexample |
| (gdb) |
| -data-disassemble -s $pc -e "$pc + 20" -- 0 |
| ^done, |
| asm_insns=[ |
| @{address="0x000107c0",func-name="main",offset="4", |
| inst="mov 2, %o0"@}, |
| @{address="0x000107c4",func-name="main",offset="8", |
| inst="sethi %hi(0x11800), %o2"@}, |
| @{address="0x000107c8",func-name="main",offset="12", |
| inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@}, |
| @{address="0x000107cc",func-name="main",offset="16", |
| inst="sethi %hi(0x11800), %o2"@}, |
| @{address="0x000107d0",func-name="main",offset="20", |
| inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}] |
| (gdb) |
| @end smallexample |
| |
| Disassemble the whole @code{main} function. Line 32 is part of |
| @code{main}. |
| |
| @smallexample |
| -data-disassemble -f basics.c -l 32 -- 0 |
| ^done,asm_insns=[ |
| @{address="0x000107bc",func-name="main",offset="0", |
| inst="save %sp, -112, %sp"@}, |
| @{address="0x000107c0",func-name="main",offset="4", |
| inst="mov 2, %o0"@}, |
| @{address="0x000107c4",func-name="main",offset="8", |
| inst="sethi %hi(0x11800), %o2"@}, |
| [@dots{}] |
| @{address="0x0001081c",func-name="main",offset="96",inst="ret "@}, |
| @{address="0x00010820",func-name="main",offset="100",inst="restore "@}] |
| (gdb) |
| @end smallexample |
| |
| Disassemble 3 instructions from the start of @code{main}: |
| |
| @smallexample |
| (gdb) |
| -data-disassemble -f basics.c -l 32 -n 3 -- 0 |
| ^done,asm_insns=[ |
| @{address="0x000107bc",func-name="main",offset="0", |
| inst="save %sp, -112, %sp"@}, |
| @{address="0x000107c0",func-name="main",offset="4", |
| inst="mov 2, %o0"@}, |
| @{address="0x000107c4",func-name="main",offset="8", |
| inst="sethi %hi(0x11800), %o2"@}] |
| (gdb) |
| @end smallexample |
| |
| Disassemble 3 instructions from the start of @code{main} in mixed mode: |
| |
| @smallexample |
| (gdb) |
| -data-disassemble -f basics.c -l 32 -n 3 -- 1 |
| ^done,asm_insns=[ |
| src_and_asm_line=@{line="31", |
| file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \ |
| testsuite/gdb.mi/basics.c",line_asm_insn=[ |
| @{address="0x000107bc",func-name="main",offset="0", |
| inst="save %sp, -112, %sp"@}]@}, |
| src_and_asm_line=@{line="32", |
| file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \ |
| testsuite/gdb.mi/basics.c",line_asm_insn=[ |
| @{address="0x000107c0",func-name="main",offset="4", |
| inst="mov 2, %o0"@}, |
| @{address="0x000107c4",func-name="main",offset="8", |
| inst="sethi %hi(0x11800), %o2"@}]@}] |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-data-evaluate-expression} Command |
| @findex -data-evaluate-expression |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-evaluate-expression @var{expr} |
| @end smallexample |
| |
| Evaluate @var{expr} as an expression. The expression could contain an |
| inferior function call. The function call will execute synchronously. |
| If the expression contains spaces, it must be enclosed in double quotes. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and |
| @samp{call}. In @code{gdbtk} only, there's a corresponding |
| @samp{gdb_eval} command. |
| |
| @subsubheading Example |
| |
| In the following example, the numbers that precede the commands are the |
| @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi} |
| Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its |
| output. |
| |
| @smallexample |
| 211-data-evaluate-expression A |
| 211^done,value="1" |
| (gdb) |
| 311-data-evaluate-expression &A |
| 311^done,value="0xefffeb7c" |
| (gdb) |
| 411-data-evaluate-expression A+3 |
| 411^done,value="4" |
| (gdb) |
| 511-data-evaluate-expression "A + 3" |
| 511^done,value="4" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-data-list-changed-registers} Command |
| @findex -data-list-changed-registers |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-list-changed-registers |
| @end smallexample |
| |
| Display a list of the registers that have changed. |
| |
| @subsubheading @value{GDBN} Command |
| |
| @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk} |
| has the corresponding command @samp{gdb_changed_register_list}. |
| |
| @subsubheading Example |
| |
| On a PPC MBX board: |
| |
| @smallexample |
| (gdb) |
| -exec-continue |
| ^running |
| |
| (gdb) |
| *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{ |
| func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c", |
| line="5"@} |
| (gdb) |
| -data-list-changed-registers |
| ^done,changed-registers=["0","1","2","4","5","6","7","8","9", |
| "10","11","13","14","15","16","17","18","19","20","21","22","23", |
| "24","25","26","27","28","30","31","64","65","66","67","69"] |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-data-list-register-names} Command |
| @findex -data-list-register-names |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-list-register-names [ ( @var{regno} )+ ] |
| @end smallexample |
| |
| Show a list of register names for the current target. If no arguments |
| are given, it shows a list of the names of all the registers. If |
| integer numbers are given as arguments, it will print a list of the |
| names of the registers corresponding to the arguments. To ensure |
| consistency between a register name and its number, the output list may |
| include empty register names. |
| |
| @subsubheading @value{GDBN} Command |
| |
| @value{GDBN} does not have a command which corresponds to |
| @samp{-data-list-register-names}. In @code{gdbtk} there is a |
| corresponding command @samp{gdb_regnames}. |
| |
| @subsubheading Example |
| |
| For the PPC MBX board: |
| @smallexample |
| (gdb) |
| -data-list-register-names |
| ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7", |
| "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18", |
| "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29", |
| "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9", |
| "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20", |
| "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31", |
| "", "pc","ps","cr","lr","ctr","xer"] |
| (gdb) |
| -data-list-register-names 1 2 3 |
| ^done,register-names=["r1","r2","r3"] |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-data-list-register-values} Command |
| @findex -data-list-register-values |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-list-register-values @var{fmt} [ ( @var{regno} )*] |
| @end smallexample |
| |
| Display the registers' contents. @var{fmt} is the format according to |
| which the registers' contents are to be returned, followed by an optional |
| list of numbers specifying the registers to display. A missing list of |
| numbers indicates that the contents of all the registers must be returned. |
| |
| Allowed formats for @var{fmt} are: |
| |
| @table @code |
| @item x |
| Hexadecimal |
| @item o |
| Octal |
| @item t |
| Binary |
| @item d |
| Decimal |
| @item r |
| Raw |
| @item N |
| Natural |
| @end table |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info |
| all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}. |
| |
| @subsubheading Example |
| |
| For a PPC MBX board (note: line breaks are for readability only, they |
| don't appear in the actual output): |
| |
| @smallexample |
| (gdb) |
| -data-list-register-values r 64 65 |
| ^done,register-values=[@{number="64",value="0xfe00a300"@}, |
| @{number="65",value="0x00029002"@}] |
| (gdb) |
| -data-list-register-values x |
| ^done,register-values=[@{number="0",value="0xfe0043c8"@}, |
| @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@}, |
| @{number="3",value="0x0"@},@{number="4",value="0xa"@}, |
| @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@}, |
| @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@}, |
| @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@}, |
| @{number="11",value="0x1"@},@{number="12",value="0x0"@}, |
| @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@}, |
| @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@}, |
| @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@}, |
| @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@}, |
| @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@}, |
| @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@}, |
| @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@}, |
| @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@}, |
| @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@}, |
| @{number="31",value="0x0"@},@{number="32",value="0x0"@}, |
| @{number="33",value="0x0"@},@{number="34",value="0x0"@}, |
| @{number="35",value="0x0"@},@{number="36",value="0x0"@}, |
| @{number="37",value="0x0"@},@{number="38",value="0x0"@}, |
| @{number="39",value="0x0"@},@{number="40",value="0x0"@}, |
| @{number="41",value="0x0"@},@{number="42",value="0x0"@}, |
| @{number="43",value="0x0"@},@{number="44",value="0x0"@}, |
| @{number="45",value="0x0"@},@{number="46",value="0x0"@}, |
| @{number="47",value="0x0"@},@{number="48",value="0x0"@}, |
| @{number="49",value="0x0"@},@{number="50",value="0x0"@}, |
| @{number="51",value="0x0"@},@{number="52",value="0x0"@}, |
| @{number="53",value="0x0"@},@{number="54",value="0x0"@}, |
| @{number="55",value="0x0"@},@{number="56",value="0x0"@}, |
| @{number="57",value="0x0"@},@{number="58",value="0x0"@}, |
| @{number="59",value="0x0"@},@{number="60",value="0x0"@}, |
| @{number="61",value="0x0"@},@{number="62",value="0x0"@}, |
| @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@}, |
| @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@}, |
| @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@}, |
| @{number="69",value="0x20002b03"@}] |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-data-read-memory} Command |
| @findex -data-read-memory |
| |
| This command is deprecated, use @code{-data-read-memory-bytes} instead. |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-read-memory [ -o @var{byte-offset} ] |
| @var{address} @var{word-format} @var{word-size} |
| @var{nr-rows} @var{nr-cols} [ @var{aschar} ] |
| @end smallexample |
| |
| @noindent |
| where: |
| |
| @table @samp |
| @item @var{address} |
| An expression specifying the address of the first memory word to be |
| read. Complex expressions containing embedded white space should be |
| quoted using the C convention. |
| |
| @item @var{word-format} |
| The format to be used to print the memory words. The notation is the |
| same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats, |
| ,Output Formats}). |
| |
| @item @var{word-size} |
| The size of each memory word in bytes. |
| |
| @item @var{nr-rows} |
| The number of rows in the output table. |
| |
| @item @var{nr-cols} |
| The number of columns in the output table. |
| |
| @item @var{aschar} |
| If present, indicates that each row should include an @sc{ascii} dump. The |
| value of @var{aschar} is used as a padding character when a byte is not a |
| member of the printable @sc{ascii} character set (printable @sc{ascii} |
| characters are those whose code is between 32 and 126, inclusively). |
| |
| @item @var{byte-offset} |
| An offset to add to the @var{address} before fetching memory. |
| @end table |
| |
| This command displays memory contents as a table of @var{nr-rows} by |
| @var{nr-cols} words, each word being @var{word-size} bytes. In total, |
| @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read |
| (returned as @samp{total-bytes}). Should less than the requested number |
| of bytes be returned by the target, the missing words are identified |
| using @samp{N/A}. The number of bytes read from the target is returned |
| in @samp{nr-bytes} and the starting address used to read memory in |
| @samp{addr}. |
| |
| The address of the next/previous row or page is available in |
| @samp{next-row} and @samp{prev-row}, @samp{next-page} and |
| @samp{prev-page}. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has |
| @samp{gdb_get_mem} memory read command. |
| |
| @subsubheading Example |
| |
| Read six bytes of memory starting at @code{bytes+6} but then offset by |
| @code{-6} bytes. Format as three rows of two columns. One byte per |
| word. Display each word in hex. |
| |
| @smallexample |
| (gdb) |
| 9-data-read-memory -o -6 -- bytes+6 x 1 3 2 |
| 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6", |
| next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396", |
| prev-page="0x0000138a",memory=[ |
| @{addr="0x00001390",data=["0x00","0x01"]@}, |
| @{addr="0x00001392",data=["0x02","0x03"]@}, |
| @{addr="0x00001394",data=["0x04","0x05"]@}] |
| (gdb) |
| @end smallexample |
| |
| Read two bytes of memory starting at address @code{shorts + 64} and |
| display as a single word formatted in decimal. |
| |
| @smallexample |
| (gdb) |
| 5-data-read-memory shorts+64 d 2 1 1 |
| 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2", |
| next-row="0x00001512",prev-row="0x0000150e", |
| next-page="0x00001512",prev-page="0x0000150e",memory=[ |
| @{addr="0x00001510",data=["128"]@}] |
| (gdb) |
| @end smallexample |
| |
| Read thirty two bytes of memory starting at @code{bytes+16} and format |
| as eight rows of four columns. Include a string encoding with @samp{x} |
| used as the non-printable character. |
| |
| @smallexample |
| (gdb) |
| 4-data-read-memory bytes+16 x 1 8 4 x |
| 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32", |
| next-row="0x000013c0",prev-row="0x0000139c", |
| next-page="0x000013c0",prev-page="0x00001380",memory=[ |
| @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@}, |
| @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@}, |
| @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@}, |
| @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@}, |
| @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@}, |
| @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@}, |
| @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@}, |
| @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}] |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-data-read-memory-bytes} Command |
| @findex -data-read-memory-bytes |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-read-memory-bytes [ -o @var{byte-offset} ] |
| @var{address} @var{count} |
| @end smallexample |
| |
| @noindent |
| where: |
| |
| @table @samp |
| @item @var{address} |
| An expression specifying the address of the first memory word to be |
| read. Complex expressions containing embedded white space should be |
| quoted using the C convention. |
| |
| @item @var{count} |
| The number of bytes to read. This should be an integer literal. |
| |
| @item @var{byte-offset} |
| The offsets in bytes relative to @var{address} at which to start |
| reading. This should be an integer literal. This option is provided |
| so that a frontend is not required to first evaluate address and then |
| perform address arithmetics itself. |
| |
| @end table |
| |
| This command attempts to read all accessible memory regions in the |
| specified range. First, all regions marked as unreadable in the memory |
| map (if one is defined) will be skipped. @xref{Memory Region |
| Attributes}. Second, @value{GDBN} will attempt to read the remaining |
| regions. For each one, if reading full region results in an errors, |
| @value{GDBN} will try to read a subset of the region. |
| |
| In general, every single byte in the region may be readable or not, |
| and the only way to read every readable byte is to try a read at |
| every address, which is not practical. Therefore, @value{GDBN} will |
| attempt to read all accessible bytes at either beginning or the end |
| of the region, using a binary division scheme. This heuristic works |
| well for reading accross a memory map boundary. Note that if a region |
| has a readable range that is neither at the beginning or the end, |
| @value{GDBN} will not read it. |
| |
| The result record (@pxref{GDB/MI Result Records}) that is output of |
| the command includes a field named @samp{memory} whose content is a |
| list of tuples. Each tuple represent a successfully read memory block |
| and has the following fields: |
| |
| @table @code |
| @item begin |
| The start address of the memory block, as hexadecimal literal. |
| |
| @item end |
| The end address of the memory block, as hexadecimal literal. |
| |
| @item offset |
| The offset of the memory block, as hexadecimal literal, relative to |
| the start address passed to @code{-data-read-memory-bytes}. |
| |
| @item contents |
| The contents of the memory block, in hex. |
| |
| @end table |
| |
| |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{x}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -data-read-memory-bytes &a 10 |
| ^done,memory=[@{begin="0xbffff154",offset="0x00000000", |
| end="0xbffff15e", |
| contents="01000000020000000300"@}] |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-data-write-memory-bytes} Command |
| @findex -data-write-memory-bytes |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -data-write-memory-bytes @var{address} @var{contents} |
| @end smallexample |
| |
| @noindent |
| where: |
| |
| @table @samp |
| @item @var{address} |
| An expression specifying the address of the first memory word to be |
| read. Complex expressions containing embedded white space should be |
| quoted using the C convention. |
| |
| @item @var{contents} |
| The hex-encoded bytes to write. |
| |
| @end table |
| |
| @subsubheading @value{GDBN} Command |
| |
| There's no corresponding @value{GDBN} command. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -data-write-memory-bytes &a "aabbccdd" |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Tracepoint Commands |
| @section @sc{gdb/mi} Tracepoint Commands |
| |
| The commands defined in this section implement MI support for |
| tracepoints. For detailed introduction, see @ref{Tracepoints}. |
| |
| @subheading The @code{-trace-find} Command |
| @findex -trace-find |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -trace-find @var{mode} [@var{parameters}@dots{}] |
| @end smallexample |
| |
| Find a trace frame using criteria defined by @var{mode} and |
| @var{parameters}. The following table lists permissible |
| modes and their parameters. For details of operation, see @ref{tfind}. |
| |
| @table @samp |
| |
| @item none |
| No parameters are required. Stops examining trace frames. |
| |
| @item frame-number |
| An integer is required as parameter. Selects tracepoint frame with |
| that index. |
| |
| @item tracepoint-number |
| An integer is required as parameter. Finds next |
| trace frame that corresponds to tracepoint with the specified number. |
| |
| @item pc |
| An address is required as parameter. Finds |
| next trace frame that corresponds to any tracepoint at the specified |
| address. |
| |
| @item pc-inside-range |
| Two addresses are required as parameters. Finds next trace |
| frame that corresponds to a tracepoint at an address inside the |
| specified range. Both bounds are considered to be inside the range. |
| |
| @item pc-outside-range |
| Two addresses are required as parameters. Finds |
| next trace frame that corresponds to a tracepoint at an address outside |
| the specified range. Both bounds are considered to be inside the range. |
| |
| @item line |
| Line specification is required as parameter. @xref{Specify Location}. |
| Finds next trace frame that corresponds to a tracepoint at |
| the specified location. |
| |
| @end table |
| |
| If @samp{none} was passed as @var{mode}, the response does not |
| have fields. Otherwise, the response may have the following fields: |
| |
| @table @samp |
| @item found |
| This field has either @samp{0} or @samp{1} as the value, depending |
| on whether a matching tracepoint was found. |
| |
| @item traceframe |
| The index of the found traceframe. This field is present iff |
| the @samp{found} field has value of @samp{1}. |
| |
| @item tracepoint |
| The index of the found tracepoint. This field is present iff |
| the @samp{found} field has value of @samp{1}. |
| |
| @item frame |
| The information about the frame corresponding to the found trace |
| frame. This field is present only if a trace frame was found. |
| @xref{GDB/MI Frame Information}, for description of this field. |
| |
| @end table |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{tfind}. |
| |
| @subheading -trace-define-variable |
| @findex -trace-define-variable |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -trace-define-variable @var{name} [ @var{value} ] |
| @end smallexample |
| |
| Create trace variable @var{name} if it does not exist. If |
| @var{value} is specified, sets the initial value of the specified |
| trace variable to that value. Note that the @var{name} should start |
| with the @samp{$} character. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{tvariable}. |
| |
| @subheading -trace-list-variables |
| @findex -trace-list-variables |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -trace-list-variables |
| @end smallexample |
| |
| Return a table of all defined trace variables. Each element of the |
| table has the following fields: |
| |
| @table @samp |
| @item name |
| The name of the trace variable. This field is always present. |
| |
| @item initial |
| The initial value. This is a 64-bit signed integer. This |
| field is always present. |
| |
| @item current |
| The value the trace variable has at the moment. This is a 64-bit |
| signed integer. This field is absent iff current value is |
| not defined, for example if the trace was never run, or is |
| presently running. |
| |
| @end table |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{tvariables}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -trace-list-variables |
| ^done,trace-variables=@{nr_rows="1",nr_cols="3", |
| hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@}, |
| @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@}, |
| @{width="11",alignment="-1",col_name="current",colhdr="Current"@}], |
| body=[variable=@{name="$trace_timestamp",initial="0"@} |
| variable=@{name="$foo",initial="10",current="15"@}]@} |
| (gdb) |
| @end smallexample |
| |
| @subheading -trace-save |
| @findex -trace-save |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -trace-save [-r ] @var{filename} |
| @end smallexample |
| |
| Saves the collected trace data to @var{filename}. Without the |
| @samp{-r} option, the data is downloaded from the target and saved |
| in a local file. With the @samp{-r} option the target is asked |
| to perform the save. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{tsave}. |
| |
| |
| @subheading -trace-start |
| @findex -trace-start |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -trace-start |
| @end smallexample |
| |
| Starts a tracing experiments. The result of this command does not |
| have any fields. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{tstart}. |
| |
| @subheading -trace-status |
| @findex -trace-status |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -trace-status |
| @end smallexample |
| |
| Obtains the status of a tracing experiment. The result may include |
| the following fields: |
| |
| @table @samp |
| |
| @item supported |
| May have a value of either @samp{0}, when no tracing operations are |
| supported, @samp{1}, when all tracing operations are supported, or |
| @samp{file} when examining trace file. In the latter case, examining |
| of trace frame is possible but new tracing experiement cannot be |
| started. This field is always present. |
| |
| @item running |
| May have a value of either @samp{0} or @samp{1} depending on whether |
| tracing experiement is in progress on target. This field is present |
| if @samp{supported} field is not @samp{0}. |
| |
| @item stop-reason |
| Report the reason why the tracing was stopped last time. This field |
| may be absent iff tracing was never stopped on target yet. The |
| value of @samp{request} means the tracing was stopped as result of |
| the @code{-trace-stop} command. The value of @samp{overflow} means |
| the tracing buffer is full. The value of @samp{disconnection} means |
| tracing was automatically stopped when @value{GDBN} has disconnected. |
| The value of @samp{passcount} means tracing was stopped when a |
| tracepoint was passed a maximal number of times for that tracepoint. |
| This field is present if @samp{supported} field is not @samp{0}. |
| |
| @item stopping-tracepoint |
| The number of tracepoint whose passcount as exceeded. This field is |
| present iff the @samp{stop-reason} field has the value of |
| @samp{passcount}. |
| |
| @item frames |
| @itemx frames-created |
| The @samp{frames} field is a count of the total number of trace frames |
| in the trace buffer, while @samp{frames-created} is the total created |
| during the run, including ones that were discarded, such as when a |
| circular trace buffer filled up. Both fields are optional. |
| |
| @item buffer-size |
| @itemx buffer-free |
| These fields tell the current size of the tracing buffer and the |
| remaining space. These fields are optional. |
| |
| @item circular |
| The value of the circular trace buffer flag. @code{1} means that the |
| trace buffer is circular and old trace frames will be discarded if |
| necessary to make room, @code{0} means that the trace buffer is linear |
| and may fill up. |
| |
| @item disconnected |
| The value of the disconnected tracing flag. @code{1} means that |
| tracing will continue after @value{GDBN} disconnects, @code{0} means |
| that the trace run will stop. |
| |
| @end table |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{tstatus}. |
| |
| @subheading -trace-stop |
| @findex -trace-stop |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -trace-stop |
| @end smallexample |
| |
| Stops a tracing experiment. The result of this command has the same |
| fields as @code{-trace-status}, except that the @samp{supported} and |
| @samp{running} fields are not output. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{tstop}. |
| |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Symbol Query |
| @section @sc{gdb/mi} Symbol Query Commands |
| |
| |
| @ignore |
| @subheading The @code{-symbol-info-address} Command |
| @findex -symbol-info-address |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-info-address @var{symbol} |
| @end smallexample |
| |
| Describe where @var{symbol} is stored. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info address}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-info-file} Command |
| @findex -symbol-info-file |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-info-file |
| @end smallexample |
| |
| Show the file for the symbol. |
| |
| @subsubheading @value{GDBN} Command |
| |
| There's no equivalent @value{GDBN} command. @code{gdbtk} has |
| @samp{gdb_find_file}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-info-function} Command |
| @findex -symbol-info-function |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-info-function |
| @end smallexample |
| |
| Show which function the symbol lives in. |
| |
| @subsubheading @value{GDBN} Command |
| |
| @samp{gdb_get_function} in @code{gdbtk}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-info-line} Command |
| @findex -symbol-info-line |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-info-line |
| @end smallexample |
| |
| Show the core addresses of the code for a source line. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info line}. |
| @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-info-symbol} Command |
| @findex -symbol-info-symbol |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-info-symbol @var{addr} |
| @end smallexample |
| |
| Describe what symbol is at location @var{addr}. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info symbol}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-list-functions} Command |
| @findex -symbol-list-functions |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-list-functions |
| @end smallexample |
| |
| List the functions in the executable. |
| |
| @subsubheading @value{GDBN} Command |
| |
| @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and |
| @samp{gdb_search} in @code{gdbtk}. |
| |
| @subsubheading Example |
| N.A. |
| @end ignore |
| |
| |
| @subheading The @code{-symbol-list-lines} Command |
| @findex -symbol-list-lines |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-list-lines @var{filename} |
| @end smallexample |
| |
| Print the list of lines that contain code and their associated program |
| addresses for the given source filename. The entries are sorted in |
| ascending PC order. |
| |
| @subsubheading @value{GDBN} Command |
| |
| There is no corresponding @value{GDBN} command. |
| |
| @subsubheading Example |
| @smallexample |
| (gdb) |
| -symbol-list-lines basics.c |
| ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}] |
| (gdb) |
| @end smallexample |
| |
| |
| @ignore |
| @subheading The @code{-symbol-list-types} Command |
| @findex -symbol-list-types |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-list-types |
| @end smallexample |
| |
| List all the type names. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding commands are @samp{info types} in @value{GDBN}, |
| @samp{gdb_search} in @code{gdbtk}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-list-variables} Command |
| @findex -symbol-list-variables |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-list-variables |
| @end smallexample |
| |
| List all the global and static variable names. |
| |
| @subsubheading @value{GDBN} Command |
| |
| @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-locate} Command |
| @findex -symbol-locate |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-locate |
| @end smallexample |
| |
| @subsubheading @value{GDBN} Command |
| |
| @samp{gdb_loc} in @code{gdbtk}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-symbol-type} Command |
| @findex -symbol-type |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -symbol-type @var{variable} |
| @end smallexample |
| |
| Show type of @var{variable}. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has |
| @samp{gdb_obj_variable}. |
| |
| @subsubheading Example |
| N.A. |
| @end ignore |
| |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI File Commands |
| @section @sc{gdb/mi} File Commands |
| |
| This section describes the GDB/MI commands to specify executable file names |
| and to read in and obtain symbol table information. |
| |
| @subheading The @code{-file-exec-and-symbols} Command |
| @findex -file-exec-and-symbols |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-exec-and-symbols @var{file} |
| @end smallexample |
| |
| Specify the executable file to be debugged. This file is the one from |
| which the symbol table is also read. If no file is specified, the |
| command clears the executable and symbol information. If breakpoints |
| are set when using this command with no arguments, @value{GDBN} will produce |
| error messages. Otherwise, no output is produced, except a completion |
| notification. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{file}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-file-exec-file} Command |
| @findex -file-exec-file |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-exec-file @var{file} |
| @end smallexample |
| |
| Specify the executable file to be debugged. Unlike |
| @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read |
| from this file. If used without argument, @value{GDBN} clears the information |
| about the executable file. No output is produced, except a completion |
| notification. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{exec-file}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @ignore |
| @subheading The @code{-file-list-exec-sections} Command |
| @findex -file-list-exec-sections |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-list-exec-sections |
| @end smallexample |
| |
| List the sections of the current executable file. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The @value{GDBN} command @samp{info file} shows, among the rest, the same |
| information as this command. @code{gdbtk} has a corresponding command |
| @samp{gdb_load_info}. |
| |
| @subsubheading Example |
| N.A. |
| @end ignore |
| |
| |
| @subheading The @code{-file-list-exec-source-file} Command |
| @findex -file-list-exec-source-file |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-list-exec-source-file |
| @end smallexample |
| |
| List the line number, the current source file, and the absolute path |
| to the current source file for the current executable. The macro |
| information field has a value of @samp{1} or @samp{0} depending on |
| whether or not the file includes preprocessor macro information. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The @value{GDBN} equivalent is @samp{info source} |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| 123-file-list-exec-source-file |
| 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1" |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-file-list-exec-source-files} Command |
| @findex -file-list-exec-source-files |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-list-exec-source-files |
| @end smallexample |
| |
| List the source files for the current executable. |
| |
| It will always output the filename, but only when @value{GDBN} can find |
| the absolute file name of a source file, will it output the fullname. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The @value{GDBN} equivalent is @samp{info sources}. |
| @code{gdbtk} has an analogous command @samp{gdb_listfiles}. |
| |
| @subsubheading Example |
| @smallexample |
| (gdb) |
| -file-list-exec-source-files |
| ^done,files=[ |
| @{file=foo.c,fullname=/home/foo.c@}, |
| @{file=/home/bar.c,fullname=/home/bar.c@}, |
| @{file=gdb_could_not_find_fullpath.c@}] |
| (gdb) |
| @end smallexample |
| |
| @ignore |
| @subheading The @code{-file-list-shared-libraries} Command |
| @findex -file-list-shared-libraries |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-list-shared-libraries |
| @end smallexample |
| |
| List the shared libraries in the program. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info shared}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-file-list-symbol-files} Command |
| @findex -file-list-symbol-files |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-list-symbol-files |
| @end smallexample |
| |
| List symbol files. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info file} (part of it). |
| |
| @subsubheading Example |
| N.A. |
| @end ignore |
| |
| |
| @subheading The @code{-file-symbol-file} Command |
| @findex -file-symbol-file |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -file-symbol-file @var{file} |
| @end smallexample |
| |
| Read symbol table info from the specified @var{file} argument. When |
| used without arguments, clears @value{GDBN}'s symbol table info. No output is |
| produced, except for a completion notification. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{symbol-file}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @ignore |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Memory Overlay Commands |
| @section @sc{gdb/mi} Memory Overlay Commands |
| |
| The memory overlay commands are not implemented. |
| |
| @c @subheading -overlay-auto |
| |
| @c @subheading -overlay-list-mapping-state |
| |
| @c @subheading -overlay-list-overlays |
| |
| @c @subheading -overlay-map |
| |
| @c @subheading -overlay-off |
| |
| @c @subheading -overlay-on |
| |
| @c @subheading -overlay-unmap |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Signal Handling Commands |
| @section @sc{gdb/mi} Signal Handling Commands |
| |
| Signal handling commands are not implemented. |
| |
| @c @subheading -signal-handle |
| |
| @c @subheading -signal-list-handle-actions |
| |
| @c @subheading -signal-list-signal-types |
| @end ignore |
| |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Target Manipulation |
| @section @sc{gdb/mi} Target Manipulation Commands |
| |
| |
| @subheading The @code{-target-attach} Command |
| @findex -target-attach |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-attach @var{pid} | @var{gid} | @var{file} |
| @end smallexample |
| |
| Attach to a process @var{pid} or a file @var{file} outside of |
| @value{GDBN}, or a thread group @var{gid}. If attaching to a thread |
| group, the id previously returned by |
| @samp{-list-thread-groups --available} must be used. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{attach}. |
| |
| @subsubheading Example |
| @smallexample |
| (gdb) |
| -target-attach 34 |
| =thread-created,id="1" |
| *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@} |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @ignore |
| @subheading The @code{-target-compare-sections} Command |
| @findex -target-compare-sections |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-compare-sections [ @var{section} ] |
| @end smallexample |
| |
| Compare data of section @var{section} on target to the exec file. |
| Without the argument, all sections are compared. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The @value{GDBN} equivalent is @samp{compare-sections}. |
| |
| @subsubheading Example |
| N.A. |
| @end ignore |
| |
| |
| @subheading The @code{-target-detach} Command |
| @findex -target-detach |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-detach [ @var{pid} | @var{gid} ] |
| @end smallexample |
| |
| Detach from the remote target which normally resumes its execution. |
| If either @var{pid} or @var{gid} is specified, detaches from either |
| the specified process, or specified thread group. There's no output. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{detach}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -target-detach |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-target-disconnect} Command |
| @findex -target-disconnect |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-disconnect |
| @end smallexample |
| |
| Disconnect from the remote target. There's no output and the target is |
| generally not resumed. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{disconnect}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -target-disconnect |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-target-download} Command |
| @findex -target-download |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-download |
| @end smallexample |
| |
| Loads the executable onto the remote target. |
| It prints out an update message every half second, which includes the fields: |
| |
| @table @samp |
| @item section |
| The name of the section. |
| @item section-sent |
| The size of what has been sent so far for that section. |
| @item section-size |
| The size of the section. |
| @item total-sent |
| The total size of what was sent so far (the current and the previous sections). |
| @item total-size |
| The size of the overall executable to download. |
| @end table |
| |
| @noindent |
| Each message is sent as status record (@pxref{GDB/MI Output Syntax, , |
| @sc{gdb/mi} Output Syntax}). |
| |
| In addition, it prints the name and size of the sections, as they are |
| downloaded. These messages include the following fields: |
| |
| @table @samp |
| @item section |
| The name of the section. |
| @item section-size |
| The size of the section. |
| @item total-size |
| The size of the overall executable to download. |
| @end table |
| |
| @noindent |
| At the end, a summary is printed. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{load}. |
| |
| @subsubheading Example |
| |
| Note: each status message appears on a single line. Here the messages |
| have been broken down so that they can fit onto a page. |
| |
| @smallexample |
| (gdb) |
| -target-download |
| +download,@{section=".text",section-size="6668",total-size="9880"@} |
| +download,@{section=".text",section-sent="512",section-size="6668", |
| total-sent="512",total-size="9880"@} |
| +download,@{section=".text",section-sent="1024",section-size="6668", |
| total-sent="1024",total-size="9880"@} |
| +download,@{section=".text",section-sent="1536",section-size="6668", |
| total-sent="1536",total-size="9880"@} |
| +download,@{section=".text",section-sent="2048",section-size="6668", |
| total-sent="2048",total-size="9880"@} |
| +download,@{section=".text",section-sent="2560",section-size="6668", |
| total-sent="2560",total-size="9880"@} |
| +download,@{section=".text",section-sent="3072",section-size="6668", |
| total-sent="3072",total-size="9880"@} |
| +download,@{section=".text",section-sent="3584",section-size="6668", |
| total-sent="3584",total-size="9880"@} |
| +download,@{section=".text",section-sent="4096",section-size="6668", |
| total-sent="4096",total-size="9880"@} |
| +download,@{section=".text",section-sent="4608",section-size="6668", |
| total-sent="4608",total-size="9880"@} |
| +download,@{section=".text",section-sent="5120",section-size="6668", |
| total-sent="5120",total-size="9880"@} |
| +download,@{section=".text",section-sent="5632",section-size="6668", |
| total-sent="5632",total-size="9880"@} |
| +download,@{section=".text",section-sent="6144",section-size="6668", |
| total-sent="6144",total-size="9880"@} |
| +download,@{section=".text",section-sent="6656",section-size="6668", |
| total-sent="6656",total-size="9880"@} |
| +download,@{section=".init",section-size="28",total-size="9880"@} |
| +download,@{section=".fini",section-size="28",total-size="9880"@} |
| +download,@{section=".data",section-size="3156",total-size="9880"@} |
| +download,@{section=".data",section-sent="512",section-size="3156", |
| total-sent="7236",total-size="9880"@} |
| +download,@{section=".data",section-sent="1024",section-size="3156", |
| total-sent="7748",total-size="9880"@} |
| +download,@{section=".data",section-sent="1536",section-size="3156", |
| total-sent="8260",total-size="9880"@} |
| +download,@{section=".data",section-sent="2048",section-size="3156", |
| total-sent="8772",total-size="9880"@} |
| +download,@{section=".data",section-sent="2560",section-size="3156", |
| total-sent="9284",total-size="9880"@} |
| +download,@{section=".data",section-sent="3072",section-size="3156", |
| total-sent="9796",total-size="9880"@} |
| ^done,address="0x10004",load-size="9880",transfer-rate="6586", |
| write-rate="429" |
| (gdb) |
| @end smallexample |
| |
| |
| @ignore |
| @subheading The @code{-target-exec-status} Command |
| @findex -target-exec-status |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-exec-status |
| @end smallexample |
| |
| Provide information on the state of the target (whether it is running or |
| not, for instance). |
| |
| @subsubheading @value{GDBN} Command |
| |
| There's no equivalent @value{GDBN} command. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-target-list-available-targets} Command |
| @findex -target-list-available-targets |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-list-available-targets |
| @end smallexample |
| |
| List the possible targets to connect to. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{help target}. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-target-list-current-targets} Command |
| @findex -target-list-current-targets |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-list-current-targets |
| @end smallexample |
| |
| Describe the current target. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding information is printed by @samp{info file} (among |
| other things). |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-target-list-parameters} Command |
| @findex -target-list-parameters |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-list-parameters |
| @end smallexample |
| |
| @c ???? |
| @end ignore |
| |
| @subsubheading @value{GDBN} Command |
| |
| No equivalent. |
| |
| @subsubheading Example |
| N.A. |
| |
| |
| @subheading The @code{-target-select} Command |
| @findex -target-select |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-select @var{type} @var{parameters @dots{}} |
| @end smallexample |
| |
| Connect @value{GDBN} to the remote target. This command takes two args: |
| |
| @table @samp |
| @item @var{type} |
| The type of target, for instance @samp{remote}, etc. |
| @item @var{parameters} |
| Device names, host names and the like. @xref{Target Commands, , |
| Commands for Managing Targets}, for more details. |
| @end table |
| |
| The output is a connection notification, followed by the address at |
| which the target program is, in the following form: |
| |
| @smallexample |
| ^connected,addr="@var{address}",func="@var{function name}", |
| args=[@var{arg list}] |
| @end smallexample |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{target}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -target-select remote /dev/ttya |
| ^connected,addr="0xfe00a300",func="??",args=[] |
| (gdb) |
| @end smallexample |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI File Transfer Commands |
| @section @sc{gdb/mi} File Transfer Commands |
| |
| |
| @subheading The @code{-target-file-put} Command |
| @findex -target-file-put |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-file-put @var{hostfile} @var{targetfile} |
| @end smallexample |
| |
| Copy file @var{hostfile} from the host system (the machine running |
| @value{GDBN}) to @var{targetfile} on the target system. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{remote put}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -target-file-put localfile remotefile |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-target-file-get} Command |
| @findex -target-file-get |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-file-get @var{targetfile} @var{hostfile} |
| @end smallexample |
| |
| Copy file @var{targetfile} from the target system to @var{hostfile} |
| on the host system. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{remote get}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -target-file-get remotefile localfile |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-target-file-delete} Command |
| @findex -target-file-delete |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -target-file-delete @var{targetfile} |
| @end smallexample |
| |
| Delete @var{targetfile} from the target system. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{remote delete}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -target-file-delete remotefile |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
| @node GDB/MI Miscellaneous Commands |
| @section Miscellaneous @sc{gdb/mi} Commands |
| |
| @c @subheading -gdb-complete |
| |
| @subheading The @code{-gdb-exit} Command |
| @findex -gdb-exit |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -gdb-exit |
| @end smallexample |
| |
| Exit @value{GDBN} immediately. |
| |
| @subsubheading @value{GDBN} Command |
| |
| Approximately corresponds to @samp{quit}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -gdb-exit |
| ^exit |
| @end smallexample |
| |
| |
| @ignore |
| @subheading The @code{-exec-abort} Command |
| @findex -exec-abort |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -exec-abort |
| @end smallexample |
| |
| Kill the inferior running program. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{kill}. |
| |
| @subsubheading Example |
| N.A. |
| @end ignore |
| |
| |
| @subheading The @code{-gdb-set} Command |
| @findex -gdb-set |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -gdb-set |
| @end smallexample |
| |
| Set an internal @value{GDBN} variable. |
| @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ????? |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{set}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -gdb-set $foo=3 |
| ^done |
| (gdb) |
| @end smallexample |
| |
| |
| @subheading The @code{-gdb-show} Command |
| @findex -gdb-show |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -gdb-show |
| @end smallexample |
| |
| Show the current value of a @value{GDBN} variable. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{show}. |
| |
| @subsubheading Example |
| |
| @smallexample |
| (gdb) |
| -gdb-show annotate |
| ^done,value="0" |
| (gdb) |
| @end smallexample |
| |
| @c @subheading -gdb-source |
| |
| |
| @subheading The @code{-gdb-version} Command |
| @findex -gdb-version |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -gdb-version |
| @end smallexample |
| |
| Show version information for @value{GDBN}. Used mostly in testing. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by |
| default shows this information when you start an interactive session. |
| |
| @subsubheading Example |
| |
| @c This example modifies the actual output from GDB to avoid overfull |
| @c box in TeX. |
| @smallexample |
| (gdb) |
| -gdb-version |
| ~GNU gdb 5.2.1 |
| ~Copyright 2000 Free Software Foundation, Inc. |
| ~GDB is free software, covered by the GNU General Public License, and |
| ~you are welcome to change it and/or distribute copies of it under |
| ~ certain conditions. |
| ~Type "show copying" to see the conditions. |
| ~There is absolutely no warranty for GDB. Type "show warranty" for |
| ~ details. |
| ~This GDB was configured as |
| "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi". |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-list-features} Command |
| @findex -list-features |
| |
| Returns a list of particular features of the MI protocol that |
| this version of gdb implements. A feature can be a command, |
| or a new field in an output of some command, or even an |
| important bugfix. While a frontend can sometimes detect presence |
| of a feature at runtime, it is easier to perform detection at debugger |
| startup. |
| |
| The command returns a list of strings, with each string naming an |
| available feature. Each returned string is just a name, it does not |
| have any internal structure. The list of possible feature names |
| is given below. |
| |
| Example output: |
| |
| @smallexample |
| (gdb) -list-features |
| ^done,result=["feature1","feature2"] |
| @end smallexample |
| |
| The current list of features is: |
| |
| @table @samp |
| @item frozen-varobjs |
| Indicates support for the @code{-var-set-frozen} command, as well |
| as possible presense of the @code{frozen} field in the output |
| of @code{-varobj-create}. |
| @item pending-breakpoints |
| Indicates support for the @option{-f} option to the @code{-break-insert} |
| command. |
| @item python |
| Indicates Python scripting support, Python-based |
| pretty-printing commands, and possible presence of the |
| @samp{display_hint} field in the output of @code{-var-list-children} |
| @item thread-info |
| Indicates support for the @code{-thread-info} command. |
| @item data-read-memory-bytes |
| Indicates support for the @code{-data-read-memory-bytes} and the |
| @code{-data-write-memory-bytes} commands. |
| @item breakpoint-notifications |
| Indicates that changes to breakpoints and breakpoints created via the |
| CLI will be announced via async records. |
| @item ada-task-info |
| Indicates support for the @code{-ada-task-info} command. |
| @end table |
| |
| @subheading The @code{-list-target-features} Command |
| @findex -list-target-features |
| |
| Returns a list of particular features that are supported by the |
| target. Those features affect the permitted MI commands, but |
| unlike the features reported by the @code{-list-features} command, the |
| features depend on which target GDB is using at the moment. Whenever |
| a target can change, due to commands such as @code{-target-select}, |
| @code{-target-attach} or @code{-exec-run}, the list of target features |
| may change, and the frontend should obtain it again. |
| Example output: |
| |
| @smallexample |
| (gdb) -list-features |
| ^done,result=["async"] |
| @end smallexample |
| |
| The current list of features is: |
| |
| @table @samp |
| @item async |
| Indicates that the target is capable of asynchronous command |
| execution, which means that @value{GDBN} will accept further commands |
| while the target is running. |
| |
| @item reverse |
| Indicates that the target is capable of reverse execution. |
| @xref{Reverse Execution}, for more information. |
| |
| @end table |
| |
| @subheading The @code{-list-thread-groups} Command |
| @findex -list-thread-groups |
| |
| @subheading Synopsis |
| |
| @smallexample |
| -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ] |
| @end smallexample |
| |
| Lists thread groups (@pxref{Thread groups}). When a single thread |
| group is passed as the argument, lists the children of that group. |
| When several thread group are passed, lists information about those |
| thread groups. Without any parameters, lists information about all |
| top-level thread groups. |
| |
| Normally, thread groups that are being debugged are reported. |
| With the @samp{--available} option, @value{GDBN} reports thread groups |
| available on the target. |
| |
| The output of this command may have either a @samp{threads} result or |
| a @samp{groups} result. The @samp{thread} result has a list of tuples |
| as value, with each tuple describing a thread (@pxref{GDB/MI Thread |
| Information}). The @samp{groups} result has a list of tuples as value, |
| each tuple describing a thread group. If top-level groups are |
| requested (that is, no parameter is passed), or when several groups |
| are passed, the output always has a @samp{groups} result. The format |
| of the @samp{group} result is described below. |
| |
| To reduce the number of roundtrips it's possible to list thread groups |
| together with their children, by passing the @samp{--recurse} option |
| and the recursion depth. Presently, only recursion depth of 1 is |
| permitted. If this option is present, then every reported thread group |
| will also include its children, either as @samp{group} or |
| @samp{threads} field. |
| |
| In general, any combination of option and parameters is permitted, with |
| the following caveats: |
| |
| @itemize @bullet |
| @item |
| When a single thread group is passed, the output will typically |
| be the @samp{threads} result. Because threads may not contain |
| anything, the @samp{recurse} option will be ignored. |
| |
| @item |
| When the @samp{--available} option is passed, limited information may |
| be available. In particular, the list of threads of a process might |
| be inaccessible. Further, specifying specific thread groups might |
| not give any performance advantage over listing all thread groups. |
| The frontend should assume that @samp{-list-thread-groups --available} |
| is always an expensive operation and cache the results. |
| |
| @end itemize |
| |
| The @samp{groups} result is a list of tuples, where each tuple may |
| have the following fields: |
| |
| @table @code |
| @item id |
| Identifier of the thread group. This field is always present. |
| The identifier is an opaque string; frontends should not try to |
| convert it to an integer, even though it might look like one. |
| |
| @item type |
| The type of the thread group. At present, only @samp{process} is a |
| valid type. |
| |
| @item pid |
| The target-specific process identifier. This field is only present |
| for thread groups of type @samp{process} and only if the process exists. |
| |
| @item num_children |
| The number of children this thread group has. This field may be |
| absent for an available thread group. |
| |
| @item threads |
| This field has a list of tuples as value, each tuple describing a |
| thread. It may be present if the @samp{--recurse} option is |
| specified, and it's actually possible to obtain the threads. |
| |
| @item cores |
| This field is a list of integers, each identifying a core that one |
| thread of the group is running on. This field may be absent if |
| such information is not available. |
| |
| @item executable |
| The name of the executable file that corresponds to this thread group. |
| The field is only present for thread groups of type @samp{process}, |
| and only if there is a corresponding executable file. |
| |
| @end table |
| |
| @subheading Example |
| |
| @smallexample |
| @value{GDBP} |
| -list-thread-groups |
| ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}] |
| -list-thread-groups 17 |
| ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)", |
| frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@}, |
| @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)", |
| frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}], |
| file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]] |
| -list-thread-groups --available |
| ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}] |
| -list-thread-groups --available --recurse 1 |
| ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2], |
| threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@}, |
| @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..] |
| -list-thread-groups --available --recurse 1 17 18 |
| ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2], |
| threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@}, |
| @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...] |
| @end smallexample |
| |
| @subheading The @code{-info-os} Command |
| @findex -info-os |
| |
| @subsubheading Synopsis |
| |
| @smallexample |
| -info-os [ @var{type} ] |
| @end smallexample |
| |
| If no argument is supplied, the command returns a table of available |
| operating-system-specific information types. If one of these types is |
| supplied as an argument @var{type}, then the command returns a table |
| of data of that type. |
| |
| The types of information available depend on the target operating |
| system. |
| |
| @subsubheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{info os}. |
| |
| @subsubheading Example |
| |
| When run on a @sc{gnu}/Linux system, the output will look something |
| like this: |
| |
| @smallexample |
| @value{GDBP} |
| -info-os |
| ^done,OSDataTable=@{nr_rows="9",nr_cols="3", |
| hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@}, |
| @{width="10",alignment="-1",col_name="col1",colhdr="Description"@}, |
| @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}], |
| body=[item=@{col0="processes",col1="Listing of all processes", |
| col2="Processes"@}, |
| item=@{col0="procgroups",col1="Listing of all process groups", |
| col2="Process groups"@}, |
| item=@{col0="threads",col1="Listing of all threads", |
| col2="Threads"@}, |
| item=@{col0="files",col1="Listing of all file descriptors", |
| col2="File descriptors"@}, |
| item=@{col0="sockets",col1="Listing of all internet-domain sockets", |
| col2="Sockets"@}, |
| item=@{col0="shm",col1="Listing of all shared-memory regions", |
| col2="Shared-memory regions"@}, |
| item=@{col0="semaphores",col1="Listing of all semaphores", |
| col2="Semaphores"@}, |
| item=@{col0="msg",col1="Listing of all message queues", |
| col2="Message queues"@}, |
| item=@{col0="modules",col1="Listing of all loaded kernel modules", |
| col2="Kernel modules"@}]@} |
| @value{GDBP} |
| -info-os processes |
| ^done,OSDataTable=@{nr_rows="190",nr_cols="4", |
| hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@}, |
| @{width="10",alignment="-1",col_name="col1",colhdr="user"@}, |
| @{width="10",alignment="-1",col_name="col2",colhdr="command"@}, |
| @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}], |
| body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@}, |
| item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@}, |
| item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@}, |
| ... |
| item=@{col0="26446",col1="stan",col2="bash",col3="0"@}, |
| item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@} |
| (gdb) |
| @end smallexample |
| |
| (Note that the MI output here includes a @code{"Title"} column that |
| does not appear in command-line @code{info os}; this column is useful |
| for MI clients that want to enumerate the types of data, such as in a |
| popup menu, but is needless clutter on the command line, and |
| @code{info os} omits it.) |
| |
| @subheading The @code{-add-inferior} Command |
| @findex -add-inferior |
| |
| @subheading Synopsis |
| |
| @smallexample |
| -add-inferior |
| @end smallexample |
| |
| Creates a new inferior (@pxref{Inferiors and Programs}). The created |
| inferior is not associated with any executable. Such association may |
| be established with the @samp{-file-exec-and-symbols} command |
| (@pxref{GDB/MI File Commands}). The command response has a single |
| field, @samp{thread-group}, whose value is the identifier of the |
| thread group corresponding to the new inferior. |
| |
| @subheading Example |
| |
| @smallexample |
| @value{GDBP} |
| -add-inferior |
| ^done,thread-group="i3" |
| @end smallexample |
| |
| @subheading The @code{-interpreter-exec} Command |
| @findex -interpreter-exec |
| |
| @subheading Synopsis |
| |
| @smallexample |
| -interpreter-exec @var{interpreter} @var{command} |
| @end smallexample |
| @anchor{-interpreter-exec} |
| |
| Execute the specified @var{command} in the given @var{interpreter}. |
| |
| @subheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{interpreter-exec}. |
| |
| @subheading Example |
| |
| @smallexample |
| (gdb) |
| -interpreter-exec console "break main" |
| &"During symbol reading, couldn't parse type; debugger out of date?.\n" |
| &"During symbol reading, bad structure-type format.\n" |
| ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n" |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-inferior-tty-set} Command |
| @findex -inferior-tty-set |
| |
| @subheading Synopsis |
| |
| @smallexample |
| -inferior-tty-set /dev/pts/1 |
| @end smallexample |
| |
| Set terminal for future runs of the program being debugged. |
| |
| @subheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1. |
| |
| @subheading Example |
| |
| @smallexample |
| (gdb) |
| -inferior-tty-set /dev/pts/1 |
| ^done |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-inferior-tty-show} Command |
| @findex -inferior-tty-show |
| |
| @subheading Synopsis |
| |
| @smallexample |
| -inferior-tty-show |
| @end smallexample |
| |
| Show terminal for future runs of program being debugged. |
| |
| @subheading @value{GDBN} Command |
| |
| The corresponding @value{GDBN} command is @samp{show inferior-tty}. |
| |
| @subheading Example |
| |
| @smallexample |
| (gdb) |
| -inferior-tty-set /dev/pts/1 |
| ^done |
| (gdb) |
| -inferior-tty-show |
| ^done,inferior_tty_terminal="/dev/pts/1" |
| (gdb) |
| @end smallexample |
| |
| @subheading The @code{-enable-timings} Command |
| @findex -enable-timings |
| |
| @subheading Synopsis |
| |
| @smallexample |
| -enable-timings [yes | no] |
| @end smallexample |
| |
| Toggle the printing of the wallclock, user and system times for an MI |
| command as a field in its output. This command is to help frontend |
| developers optimize the performance of their code. No argument is |
| equivalent to @samp{yes}. |
| |
| @subheading @value{GDBN} Command |
| |
| No equivalent. |
| |
| @subheading Example |
| |
| @smallexample |
| (gdb) |
| -enable-timings |
| ^done |
| (gdb) |
| -break-insert main |
| ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y", |
| addr="0x080484ed",func="main",file="myprog.c", |
| fullname="/home/nickrob/myprog.c",line="73",times="0"@}, |
| time=@{wallclock="0.05185",user="0.00800",system="0.00000"@} |
| (gdb) |
| -enable-timings no |
| ^done |
| (gdb) |
| -exec-run |
| ^running |
| (gdb) |
| *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0", |
| frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@}, |
| @{name="argv",value="0xbfb60364"@}],file="myprog.c", |
| fullname="/home/nickrob/myprog.c",line="73"@} |
| (gdb) |
| @end smallexample |
| |
| @node Annotations |
| @chapter @value{GDBN} Annotations |
| |
| This chapter describes annotations in @value{GDBN}. Annotations were |
| designed to interface @value{GDBN} to graphical user interfaces or other |
| similar programs which want to interact with @value{GDBN} at a |
| relatively high level. |
| |
| The annotation mechanism has largely been superseded by @sc{gdb/mi} |
| (@pxref{GDB/MI}). |
| |
| @ignore |
| This is Edition @value{EDITION}, @value{DATE}. |
| @end ignore |
| |
| @menu |
| * Annotations Overview:: What annotations are; the general syntax. |
| * Server Prefix:: Issuing a command without affecting user state. |
| * Prompting:: Annotations marking @value{GDBN}'s need for input. |
| * Errors:: Annotations for error messages. |
| * Invalidation:: Some annotations describe things now invalid. |
| * Annotations for Running:: |
| Whether the program is running, how it stopped, etc. |
| * Source Annotations:: Annotations describing source code. |
| @end menu |
| |
| @node Annotations Overview |
| @section What is an Annotation? |
| @cindex annotations |
| |
| Annotations start with a newline character, two @samp{control-z} |
| characters, and the name of the annotation. If there is no additional |
| information associated with this annotation, the name of the annotation |
| is followed immediately by a newline. If there is additional |
| information, the name of the annotation is followed by a space, the |
| additional information, and a newline. The additional information |
| cannot contain newline characters. |
| |
| Any output not beginning with a newline and two @samp{control-z} |
| characters denotes literal output from @value{GDBN}. Currently there is |
| no need for @value{GDBN} to output a newline followed by two |
| @samp{control-z} characters, but if there was such a need, the |
| annotations could be extended with an @samp{escape} annotation which |
| means those three characters as output. |
| |
| The annotation @var{level}, which is specified using the |
| @option{--annotate} command line option (@pxref{Mode Options}), controls |
| how much information @value{GDBN} prints together with its prompt, |
| values of expressions, source lines, and other types of output. Level 0 |
| is for no annotations, level 1 is for use when @value{GDBN} is run as a |
| subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable |
| for programs that control @value{GDBN}, and level 2 annotations have |
| been made obsolete (@pxref{Limitations, , Limitations of the Annotation |
| Interface, annotate, GDB's Obsolete Annotations}). |
| |
| @table @code |
| @kindex set annotate |
| @item set annotate @var{level} |
| The @value{GDBN} command @code{set annotate} sets the level of |
| annotations to the specified @var{level}. |
| |
| @item show annotate |
| @kindex show annotate |
| Show the current annotation level. |
| @end table |
| |
| This chapter describes level 3 annotations. |
| |
| A simple example of starting up @value{GDBN} with annotations is: |
| |
| @smallexample |
| $ @kbd{gdb --annotate=3} |
| GNU gdb 6.0 |
| Copyright 2003 Free Software Foundation, Inc. |
| GDB is free software, covered by the GNU General Public License, |
| and you are welcome to change it and/or distribute copies of it |
| under certain conditions. |
| Type "show copying" to see the conditions. |
| There is absolutely no warranty for GDB. Type "show warranty" |
| for details. |
| This GDB was configured as "i386-pc-linux-gnu" |
| |
| ^Z^Zpre-prompt |
| (@value{GDBP}) |
| ^Z^Zprompt |
| @kbd{quit} |
| |
| ^Z^Zpost-prompt |
| $ |
| @end smallexample |
| |
| Here @samp{quit} is input to @value{GDBN}; the rest is output from |
| @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z} |
| denotes a @samp{control-z} character) are annotations; the rest is |
| output from @value{GDBN}. |
| |
| @node Server Prefix |
| @section The Server Prefix |
| @cindex server prefix |
| |
| If you prefix a command with @samp{server } then it will not affect |
| the command history, nor will it affect @value{GDBN}'s notion of which |
| command to repeat if @key{RET} is pressed on a line by itself. This |
| means that commands can be run behind a user's back by a front-end in |
| a transparent manner. |
| |
| The @code{server } prefix does not affect the recording of values into |
| the value history; to print a value without recording it into the |
| value history, use the @code{output} command instead of the |
| @code{print} command. |
| |
| Using this prefix also disables confirmation requests |
| (@pxref{confirmation requests}). |
| |
| @node Prompting |
| @section Annotation for @value{GDBN} Input |
| |
| @cindex annotations for prompts |
| When @value{GDBN} prompts for input, it annotates this fact so it is possible |
| to know when to send output, when the output from a given command is |
| over, etc. |
| |
| Different kinds of input each have a different @dfn{input type}. Each |
| input type has three annotations: a @code{pre-} annotation, which |
| denotes the beginning of any prompt which is being output, a plain |
| annotation, which denotes the end of the prompt, and then a @code{post-} |
| annotation which denotes the end of any echo which may (or may not) be |
| associated with the input. For example, the @code{prompt} input type |
| features the following annotations: |
| |
| @smallexample |
| ^Z^Zpre-prompt |
| ^Z^Zprompt |
| ^Z^Zpost-prompt |
| @end smallexample |
| |
| The input types are |
| |
| @table @code |
| @findex pre-prompt annotation |
| @findex prompt annotation |
| @findex post-prompt annotation |
| @item prompt |
| When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt). |
| |
| @findex pre-commands annotation |
| @findex commands annotation |
| @findex post-commands annotation |
| @item commands |
| When @value{GDBN} prompts for a set of commands, like in the @code{commands} |
| command. The annotations are repeated for each command which is input. |
| |
| @findex pre-overload-choice annotation |
| @findex overload-choice annotation |
| @findex post-overload-choice annotation |
| @item overload-choice |
| When @value{GDBN} wants the user to select between various overloaded functions. |
| |
| @findex pre-query annotation |
| @findex query annotation |
| @findex post-query annotation |
| @item query |
| When @value{GDBN} wants the user to confirm a potentially dangerous operation. |
| |
| @findex pre-prompt-for-continue annotation |
| @findex prompt-for-continue annotation |
| @findex post-prompt-for-continue annotation |
| @item prompt-for-continue |
| When @value{GDBN} is asking the user to press return to continue. Note: Don't |
| expect this to work well; instead use @code{set height 0} to disable |
| prompting. This is because the counting of lines is buggy in the |
| presence of annotations. |
| @end table |
| |
| @node Errors |
| @section Errors |
| @cindex annotations for errors, warnings and interrupts |
| |
| @findex quit annotation |
| @smallexample |
| ^Z^Zquit |
| @end smallexample |
| |
| This annotation occurs right before @value{GDBN} responds to an interrupt. |
| |
| @findex error annotation |
| @smallexample |
| ^Z^Zerror |
| @end smallexample |
| |
| This annotation occurs right before @value{GDBN} responds to an error. |
| |
| Quit and error annotations indicate that any annotations which @value{GDBN} was |
| in the middle of may end abruptly. For example, if a |
| @code{value-history-begin} annotation is followed by a @code{error}, one |
| cannot expect to receive the matching @code{value-history-end}. One |
| cannot expect not to receive it either, however; an error annotation |
| does not necessarily mean that @value{GDBN} is immediately returning all the way |
| to the top level. |
| |
| @findex error-begin annotation |
| A quit or error annotation may be preceded by |
| |
| @smallexample |
| ^Z^Zerror-begin |
| @end smallexample |
| |
| Any output between that and the quit or error annotation is the error |
| message. |
| |
| Warning messages are not yet annotated. |
| @c If we want to change that, need to fix warning(), type_error(), |
| @c range_error(), and possibly other places. |
| |
| @node Invalidation |
| @section Invalidation Notices |
| |
| @cindex annotations for invalidation messages |
| The following annotations say that certain pieces of state may have |
| changed. |
| |
| @table @code |
| @findex frames-invalid annotation |
| @item ^Z^Zframes-invalid |
| |
| The frames (for example, output from the @code{backtrace} command) may |
| have changed. |
| |
| @findex breakpoints-invalid annotation |
| @item ^Z^Zbreakpoints-invalid |
| |
| The breakpoints may have changed. For example, the user just added or |
| deleted a breakpoint. |
| @end table |
| |
| @node Annotations for Running |
| @section Running the Program |
| @cindex annotations for running programs |
| |
| @findex starting annotation |
| @findex stopping annotation |
| When the program starts executing due to a @value{GDBN} command such as |
| @code{step} or @code{continue}, |
| |
| @smallexample |
| ^Z^Zstarting |
| @end smallexample |
| |
| is output. When the program stops, |
| |
| @smallexample |
| ^Z^Zstopped |
| @end smallexample |
| |
| is output. Before the @code{stopped} annotation, a variety of |
| annotations describe how the program stopped. |
| |
| @table @code |
| @findex exited annotation |
| @item ^Z^Zexited @var{exit-status} |
| The program exited, and @var{exit-status} is the exit status (zero for |
| successful exit, otherwise nonzero). |
| |
| @findex signalled annotation |
| @findex signal-name annotation |
| @findex signal-name-end annotation |
| @findex signal-string annotation |
| @findex signal-string-end annotation |
| @item ^Z^Zsignalled |
| The program exited with a signal. After the @code{^Z^Zsignalled}, the |
| annotation continues: |
| |
| @smallexample |
| @var{intro-text} |
| ^Z^Zsignal-name |
| @var{name} |
| ^Z^Zsignal-name-end |
| @var{middle-text} |
| ^Z^Zsignal-string |
| @var{string} |
| ^Z^Zsignal-string-end |
| @var{end-text} |
| @end smallexample |
| |
| @noindent |
| where @var{name} is the name of the signal, such as @code{SIGILL} or |
| @code{SIGSEGV}, and @var{string} is the explanation of the signal, such |
| as @code{Illegal Instruction} or @code{Segmentation fault}. |
| @var{intro-text}, @var{middle-text}, and @var{end-text} are for the |
| user's benefit and have no particular format. |
| |
| @findex signal annotation |
| @item ^Z^Zsignal |
| The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is |
| just saying that the program received the signal, not that it was |
| terminated with it. |
| |
| @findex breakpoint annotation |
| @item ^Z^Zbreakpoint @var{number} |
| The program hit breakpoint number @var{number}. |
| |
| @findex watchpoint annotation |
| @item ^Z^Zwatchpoint @var{number} |
| The program hit watchpoint number @var{number}. |
| @end table |
| |
| @node Source Annotations |
| @section Displaying Source |
| @cindex annotations for source display |
| |
| @findex source annotation |
| The following annotation is used instead of displaying source code: |
| |
| @smallexample |
| ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr} |
| @end smallexample |
| |
| where @var{filename} is an absolute file name indicating which source |
| file, @var{line} is the line number within that file (where 1 is the |
| first line in the file), @var{character} is the character position |
| within the file (where 0 is the first character in the file) (for most |
| debug formats this will necessarily point to the beginning of a line), |
| @var{middle} is @samp{middle} if @var{addr} is in the middle of the |
| line, or @samp{beg} if @var{addr} is at the beginning of the line, and |
| @var{addr} is the address in the target program associated with the |
| source which is being displayed. @var{addr} is in the form @samp{0x} |
| followed by one or more lowercase hex digits (note that this does not |
| depend on the language). |
| |
| @node JIT Interface |
| @chapter JIT Compilation Interface |
| @cindex just-in-time compilation |
| @cindex JIT compilation interface |
| |
| This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation |
| interface. A JIT compiler is a program or library that generates native |
| executable code at runtime and executes it, usually in order to achieve good |
| performance while maintaining platform independence. |
| |
| Programs that use JIT compilation are normally difficult to debug because |
| portions of their code are generated at runtime, instead of being loaded from |
| object files, which is where @value{GDBN} normally finds the program's symbols |
| and debug information. In order to debug programs that use JIT compilation, |
| @value{GDBN} has an interface that allows the program to register in-memory |
| symbol files with @value{GDBN} at runtime. |
| |
| If you are using @value{GDBN} to debug a program that uses this interface, then |
| it should work transparently so long as you have not stripped the binary. If |
| you are developing a JIT compiler, then the interface is documented in the rest |
| of this chapter. At this time, the only known client of this interface is the |
| LLVM JIT. |
| |
| Broadly speaking, the JIT interface mirrors the dynamic loader interface. The |
| JIT compiler communicates with @value{GDBN} by writing data into a global |
| variable and calling a fuction at a well-known symbol. When @value{GDBN} |
| attaches, it reads a linked list of symbol files from the global variable to |
| find existing code, and puts a breakpoint in the function so that it can find |
| out about additional code. |
| |
| @menu |
| * Declarations:: Relevant C struct declarations |
| * Registering Code:: Steps to register code |
| * Unregistering Code:: Steps to unregister code |
| * Custom Debug Info:: Emit debug information in a custom format |
| @end menu |
| |
| @node Declarations |
| @section JIT Declarations |
| |
| These are the relevant struct declarations that a C program should include to |
| implement the interface: |
| |
| @smallexample |
| typedef enum |
| @{ |
| JIT_NOACTION = 0, |
| JIT_REGISTER_FN, |
| JIT_UNREGISTER_FN |
| @} jit_actions_t; |
| |
| struct jit_code_entry |
| @{ |
| struct jit_code_entry *next_entry; |
| struct jit_code_entry *prev_entry; |
| const char *symfile_addr; |
| uint64_t symfile_size; |
| @}; |
| |
| struct jit_descriptor |
| @{ |
| uint32_t version; |
| /* This type should be jit_actions_t, but we use uint32_t |
| to be explicit about the bitwidth. */ |
| uint32_t action_flag; |
| struct jit_code_entry *relevant_entry; |
| struct jit_code_entry *first_entry; |
| @}; |
| |
| /* GDB puts a breakpoint in this function. */ |
| void __attribute__((noinline)) __jit_debug_register_code() @{ @}; |
| |
| /* Make sure to specify the version statically, because the |
| debugger may check the version before we can set it. */ |
| struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @}; |
| @end smallexample |
| |
| If the JIT is multi-threaded, then it is important that the JIT synchronize any |
| modifications to this global data properly, which can easily be done by putting |
| a global mutex around modifications to these structures. |
| |
| @node Registering Code |
| @section Registering Code |
| |
| To register code with @value{GDBN}, the JIT should follow this protocol: |
| |
| @itemize @bullet |
| @item |
| Generate an object file in memory with symbols and other desired debug |
| information. The file must include the virtual addresses of the sections. |
| |
| @item |
| Create a code entry for the file, which gives the start and size of the symbol |
| file. |
| |
| @item |
| Add it to the linked list in the JIT descriptor. |
| |
| @item |
| Point the relevant_entry field of the descriptor at the entry. |
| |
| @item |
| Set @code{action_flag} to @code{JIT_REGISTER} and call |
| @code{__jit_debug_register_code}. |
| @end itemize |
| |
| When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the |
| @code{relevant_entry} pointer so it doesn't have to walk the list looking for |
| new code. However, the linked list must still be maintained in order to allow |
| @value{GDBN} to attach to a running process and still find the symbol files. |
| |
| @node Unregistering Code |
| @section Unregistering Code |
| |
| If code is freed, then the JIT should use the following protocol: |
| |
| @itemize @bullet |
| @item |
| Remove the code entry corresponding to the code from the linked list. |
| |
| @item |
| Point the @code{relevant_entry} field of the descriptor at the code entry. |
| |
| @item |
| Set @code{action_flag} to @code{JIT_UNREGISTER} and call |
| @code{__jit_debug_register_code}. |
| @end itemize |
| |
| If the JIT frees or recompiles code without unregistering it, then @value{GDBN} |
| and the JIT will leak the memory used for the associated symbol files. |
| |
| @node Custom Debug Info |
| @section Custom Debug Info |
| @cindex custom JIT debug info |
| @cindex JIT debug info reader |
| |
| Generating debug information in platform-native file formats (like ELF |
| or COFF) may be an overkill for JIT compilers; especially if all the |
| debug info is used for is displaying a meaningful backtrace. The |
| issue can be resolved by having the JIT writers decide on a debug info |
| format and also provide a reader that parses the debug info generated |
| by the JIT compiler. This section gives a brief overview on writing |
| such a parser. More specific details can be found in the source file |
| @file{gdb/jit-reader.in}, which is also installed as a header at |
| @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion. |
| |
| The reader is implemented as a shared object (so this functionality is |
| not available on platforms which don't allow loading shared objects at |
| runtime). Two @value{GDBN} commands, @code{jit-reader-load} and |
| @code{jit-reader-unload} are provided, to be used to load and unload |
| the readers from a preconfigured directory. Once loaded, the shared |
| object is used the parse the debug information emitted by the JIT |
| compiler. |
| |
| @menu |
| * Using JIT Debug Info Readers:: How to use supplied readers correctly |
| * Writing JIT Debug Info Readers:: Creating a debug-info reader |
| @end menu |
| |
| @node Using JIT Debug Info Readers |
| @subsection Using JIT Debug Info Readers |
| @kindex jit-reader-load |
| @kindex jit-reader-unload |
| |
| Readers can be loaded and unloaded using the @code{jit-reader-load} |
| and @code{jit-reader-unload} commands. |
| |
| @table @code |
| @item jit-reader-load @var{reader-name} |
| Load the JIT reader named @var{reader-name}. On a UNIX system, this |
| will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where |
| @var{libdir} is the system library directory, usually |
| @file{/usr/local/lib}. Only one reader can be active at a time; |
| trying to load a second reader when one is already loaded will result |
| in @value{GDBN} reporting an error. A new JIT reader can be loaded by |
| first unloading the current one using @code{jit-reader-load} and then |
| invoking @code{jit-reader-load}. |
| |
| @item jit-reader-unload |
| Unload the currently loaded JIT reader. |
| |
| @end table |
| |
| @node Writing JIT Debug Info Readers |
| @subsection Writing JIT Debug Info Readers |
| @cindex writing JIT debug info readers |
| |
| As mentioned, a reader is essentially a shared object conforming to a |
| certain ABI. This ABI is described in @file{jit-reader.h}. |
| |
| @file{jit-reader.h} defines the structures, macros and functions |
| required to write a reader. It is installed (along with |
| @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is |
| the system include directory. |
| |
| Readers need to be released under a GPL compatible license. A reader |
| can be declared as released under such a license by placing the macro |
| @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file. |
| |
| The entry point for readers is the symbol @code{gdb_init_reader}, |
| which is expected to be a function with the prototype |
| |
| @findex gdb_init_reader |
| @smallexample |
| extern struct gdb_reader_funcs *gdb_init_reader (void); |
| @end smallexample |
| |
| @cindex @code{struct gdb_reader_funcs} |
| |
| @code{struct gdb_reader_funcs} contains a set of pointers to callback |
| functions. These functions are executed to read the debug info |
| generated by the JIT compiler (@code{read}), to unwind stack frames |
| (@code{unwind}) and to create canonical frame IDs |
| (@code{get_Frame_id}). It also has a callback that is called when the |
| reader is being unloaded (@code{destroy}). The struct looks like this |
| |
| @smallexample |
| struct gdb_reader_funcs |
| @{ |
| /* Must be set to GDB_READER_INTERFACE_VERSION. */ |
| int reader_version; |
| |
| /* For use by the reader. */ |
| void *priv_data; |
| |
| gdb_read_debug_info *read; |
| gdb_unwind_frame *unwind; |
| gdb_get_frame_id *get_frame_id; |
| gdb_destroy_reader *destroy; |
| @}; |
| @end smallexample |
| |
| @cindex @code{struct gdb_symbol_callbacks} |
| @cindex @code{struct gdb_unwind_callbacks} |
| |
| The callbacks are provided with another set of callbacks by |
| @value{GDBN} to do their job. For @code{read}, these callbacks are |
| passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind} |
| and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}. |
| @code{struct gdb_symbol_callbacks} has callbacks to create new object |
| files and new symbol tables inside those object files. @code{struct |
| gdb_unwind_callbacks} has callbacks to read registers off the current |
| frame and to write out the values of the registers in the previous |
| frame. Both have a callback (@code{target_read}) to read bytes off the |
| target's address space. |
| |
| @node In-Process Agent |
| @chapter In-Process Agent |
| @cindex debugging agent |
| The traditional debugging model is conceptually low-speed, but works fine, |
| because most bugs can be reproduced in debugging-mode execution. However, |
| as multi-core or many-core processors are becoming mainstream, and |
| multi-threaded programs become more and more popular, there should be more |
| and more bugs that only manifest themselves at normal-mode execution, for |
| example, thread races, because debugger's interference with the program's |
| timing may conceal the bugs. On the other hand, in some applications, |
| it is not feasible for the debugger to interrupt the program's execution |
| long enough for the developer to learn anything helpful about its behavior. |
| If the program's correctness depends on its real-time behavior, delays |
| introduced by a debugger might cause the program to fail, even when the |
| code itself is correct. It is useful to be able to observe the program's |
| behavior without interrupting it. |
| |
| Therefore, traditional debugging model is too intrusive to reproduce |
| some bugs. In order to reduce the interference with the program, we can |
| reduce the number of operations performed by debugger. The |
| @dfn{In-Process Agent}, a shared library, is running within the same |
| process with inferior, and is able to perform some debugging operations |
| itself. As a result, debugger is only involved when necessary, and |
| performance of debugging can be improved accordingly. Note that |
| interference with program can be reduced but can't be removed completely, |
| because the in-process agent will still stop or slow down the program. |
| |
| The in-process agent can interpret and execute Agent Expressions |
| (@pxref{Agent Expressions}) during performing debugging operations. The |
| agent expressions can be used for different purposes, such as collecting |
| data in tracepoints, and condition evaluation in breakpoints. |
| |
| @anchor{Control Agent} |
| You can control whether the in-process agent is used as an aid for |
| debugging with the following commands: |
| |
| @table @code |
| @kindex set agent on |
| @item set agent on |
| Causes the in-process agent to perform some operations on behalf of the |
| debugger. Just which operations requested by the user will be done |
| by the in-process agent depends on the its capabilities. For example, |
| if you request to evaluate breakpoint conditions in the in-process agent, |
| and the in-process agent has such capability as well, then breakpoint |
| conditions will be evaluated in the in-process agent. |
| |
| @kindex set agent off |
| @item set agent off |
| Disables execution of debugging operations by the in-process agent. All |
| of the operations will be performed by @value{GDBN}. |
| |
| @kindex show agent |
| @item show agent |
| Display the current setting of execution of debugging operations by |
| the in-process agent. |
| @end table |
| |
| @menu |
| * In-Process Agent Protocol:: |
| @end menu |
| |
| @node In-Process Agent Protocol |
| @section In-Process Agent Protocol |
| @cindex in-process agent protocol |
| |
| The in-process agent is able to communicate with both @value{GDBN} and |
| GDBserver (@pxref{In-Process Agent}). This section documents the protocol |
| used for communications between @value{GDBN} or GDBserver and the IPA. |
| In general, @value{GDBN} or GDBserver sends commands |
| (@pxref{IPA Protocol Commands}) and data to in-process agent, and then |
| in-process agent replies back with the return result of the command, or |
| some other information. The data sent to in-process agent is composed |
| of primitive data types, such as 4-byte or 8-byte type, and composite |
| types, which are called objects (@pxref{IPA Protocol Objects}). |
| |
| @menu |
| * IPA Protocol Objects:: |
| * IPA Protocol Commands:: |
| @end menu |
| |
| @node IPA Protocol Objects |
| @subsection IPA Protocol Objects |
| @cindex ipa protocol objects |
| |
| The commands sent to and results received from agent may contain some |
| complex data types called @dfn{objects}. |
| |
| The in-process agent is running on the same machine with @value{GDBN} |
| or GDBserver, so it doesn't have to handle as much differences between |
| two ends as remote protocol (@pxref{Remote Protocol}) tries to handle. |
| However, there are still some differences of two ends in two processes: |
| |
| @enumerate |
| @item |
| word size. On some 64-bit machines, @value{GDBN} or GDBserver can be |
| compiled as a 64-bit executable, while in-process agent is a 32-bit one. |
| @item |
| ABI. Some machines may have multiple types of ABI, @value{GDBN} or |
| GDBserver is compiled with one, and in-process agent is compiled with |
| the other one. |
| @end enumerate |
| |
| Here are the IPA Protocol Objects: |
| |
| @enumerate |
| @item |
| agent expression object. It represents an agent expression |
| (@pxref{Agent Expressions}). |
| @anchor{agent expression object} |
| @item |
| tracepoint action object. It represents a tracepoint action |
| (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers, |
| memory, static trace data and to evaluate expression. |
| @anchor{tracepoint action object} |
| @item |
| tracepoint object. It represents a tracepoint (@pxref{Tracepoints}). |
| @anchor{tracepoint object} |
| |
| @end enumerate |
| |
| The following table describes important attributes of each IPA protocol |
| object: |
| |
| @multitable @columnfractions .30 .20 .50 |
| @headitem Name @tab Size @tab Description |
| @item @emph{agent expression object} @tab @tab |
| @item length @tab 4 @tab length of bytes code |
| @item byte code @tab @var{length} @tab contents of byte code |
| @item @emph{tracepoint action for collecting memory} @tab @tab |
| @item 'M' @tab 1 @tab type of tracepoint action |
| @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the |
| address of the lowest byte to collect, otherwise @var{addr} is the offset |
| of @var{basereg} for memory collecting. |
| @item len @tab 8 @tab length of memory for collecting |
| @item basereg @tab 4 @tab the register number containing the starting |
| memory address for collecting. |
| @item @emph{tracepoint action for collecting registers} @tab @tab |
| @item 'R' @tab 1 @tab type of tracepoint action |
| @item @emph{tracepoint action for collecting static trace data} @tab @tab |
| @item 'L' @tab 1 @tab type of tracepoint action |
| @item @emph{tracepoint action for expression evaluation} @tab @tab |
| @item 'X' @tab 1 @tab type of tracepoint action |
| @item agent expression @tab length of @tab @ref{agent expression object} |
| @item @emph{tracepoint object} @tab @tab |
| @item number @tab 4 @tab number of tracepoint |
| @item address @tab 8 @tab address of tracepoint inserted on |
| @item type @tab 4 @tab type of tracepoint |
| @item enabled @tab 1 @tab enable or disable of tracepoint |
| @item step_count @tab 8 @tab step |
| @item pass_count @tab 8 @tab pass |
| @item numactions @tab 4 @tab number of tracepoint actions |
| @item hit count @tab 8 @tab hit count |
| @item trace frame usage @tab 8 @tab trace frame usage |
| @item compiled_cond @tab 8 @tab compiled condition |
| @item orig_size @tab 8 @tab orig size |
| @item condition @tab 4 if condition is NULL otherwise length of |
| @ref{agent expression object} |
| @tab zero if condition is NULL, otherwise is |
| @ref{agent expression object} |
| @item actions @tab variable |
| @tab numactions number of @ref{tracepoint action object} |
| @end multitable |
| |
| @node IPA Protocol Commands |
| @subsection IPA Protocol Commands |
| @cindex ipa protocol commands |
| |
| The spaces in each command are delimiters to ease reading this commands |
| specification. They don't exist in real commands. |
| |
| @table @samp |
| |
| @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head} |
| Installs a new fast tracepoint described by @var{tracepoint_object} |
| (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the |
| head of @dfn{jumppad}, which is used to jump to data collection routine |
| in IPA finally. |
| |
| Replies: |
| @table @samp |
| @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump} |
| @var{target_address} is address of tracepoint in the inferior. |
| @var{gdb_jump_pad_head} is updated head of jumppad. Both of |
| @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long. |
| @var{fjump} contains a sequence of instructions jump to jumppad entry. |
| @var{fjump_size}, 4-byte long, is the size of @var{fjump}. |
| @item E @var{NN} |
| for an error |
| |
| @end table |
| |
| @item qTfSTM |
| @xref{qTfSTM}. |
| @item qTsSTM |
| @xref{qTsSTM}. |
| @item qTSTMat |
| @xref{qTSTMat}. |
| @item probe_marker_at:@var{address} |
| Asks in-process agent to probe the marker at @var{address}. |
| |
| Replies: |
| @table @samp |
| @item E @var{NN} |
| for an error |
| @end table |
| @item unprobe_marker_at:@var{address} |
| Asks in-process agent to unprobe the marker at @var{address}. |
| @end table |
| |
| @node GDB Bugs |
| @chapter Reporting Bugs in @value{GDBN} |
| @cindex bugs in @value{GDBN} |
| @cindex reporting bugs in @value{GDBN} |
| |
| Your bug reports play an essential role in making @value{GDBN} reliable. |
| |
| Reporting a bug may help you by bringing a solution to your problem, or it |
| may not. But in any case the principal function of a bug report is to help |
| the entire community by making the next version of @value{GDBN} work better. Bug |
| reports are your contribution to the maintenance of @value{GDBN}. |
| |
| In order for a bug report to serve its purpose, you must include the |
| information that enables us to fix the bug. |
| |
| @menu |
| * Bug Criteria:: Have you found a bug? |
| * Bug Reporting:: How to report bugs |
| @end menu |
| |
| @node Bug Criteria |
| @section Have You Found a Bug? |
| @cindex bug criteria |
| |
| If you are not sure whether you have found a bug, here are some guidelines: |
| |
| @itemize @bullet |
| @cindex fatal signal |
| @cindex debugger crash |
| @cindex crash of debugger |
| @item |
| If the debugger gets a fatal signal, for any input whatever, that is a |
| @value{GDBN} bug. Reliable debuggers never crash. |
| |
| @cindex error on valid input |
| @item |
| If @value{GDBN} produces an error message for valid input, that is a |
| bug. (Note that if you're cross debugging, the problem may also be |
| somewhere in the connection to the target.) |
| |
| @cindex invalid input |
| @item |
| If @value{GDBN} does not produce an error message for invalid input, |
| that is a bug. However, you should note that your idea of |
| ``invalid input'' might be our idea of ``an extension'' or ``support |
| for traditional practice''. |
| |
| @item |
| If you are an experienced user of debugging tools, your suggestions |
| for improvement of @value{GDBN} are welcome in any case. |
| @end itemize |
| |
| @node Bug Reporting |
| @section How to Report Bugs |
| @cindex bug reports |
| @cindex @value{GDBN} bugs, reporting |
| |
| A number of companies and individuals offer support for @sc{gnu} products. |
| If you obtained @value{GDBN} from a support organization, we recommend you |
| contact that organization first. |
| |
| You can find contact information for many support companies and |
| individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs |
| distribution. |
| @c should add a web page ref... |
| |
| @ifset BUGURL |
| @ifset BUGURL_DEFAULT |
| In any event, we also recommend that you submit bug reports for |
| @value{GDBN}. The preferred method is to submit them directly using |
| @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web |
| page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can |
| be used. |
| |
| @strong{Do not send bug reports to @samp{info-gdb}, or to |
| @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do |
| not want to receive bug reports. Those that do have arranged to receive |
| @samp{bug-gdb}. |
| |
| The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which |
| serves as a repeater. The mailing list and the newsgroup carry exactly |
| the same messages. Often people think of posting bug reports to the |
| newsgroup instead of mailing them. This appears to work, but it has one |
| problem which can be crucial: a newsgroup posting often lacks a mail |
| path back to the sender. Thus, if we need to ask for more information, |
| we may be unable to reach you. For this reason, it is better to send |
| bug reports to the mailing list. |
| @end ifset |
| @ifclear BUGURL_DEFAULT |
| In any event, we also recommend that you submit bug reports for |
| @value{GDBN} to @value{BUGURL}. |
| @end ifclear |
| @end ifset |
| |
| The fundamental principle of reporting bugs usefully is this: |
| @strong{report all the facts}. If you are not sure whether to state a |
| fact or leave it out, state it! |
| |
| Often people omit facts because they think they know what causes the |
| problem and assume that some details do not matter. Thus, you might |
| assume that the name of the variable you use in an example does not matter. |
| Well, probably it does not, but one cannot be sure. Perhaps the bug is a |
| stray memory reference which happens to fetch from the location where that |
| name is stored in memory; perhaps, if the name were different, the contents |
| of that location would fool the debugger into doing the right thing despite |
| the bug. Play it safe and give a specific, complete example. That is the |
| easiest thing for you to do, and the most helpful. |
| |
| Keep in mind that the purpose of a bug report is to enable us to fix the |
| bug. It may be that the bug has been reported previously, but neither |
| you nor we can know that unless your bug report is complete and |
| self-contained. |
| |
| Sometimes people give a few sketchy facts and ask, ``Does this ring a |
| bell?'' Those bug reports are useless, and we urge everyone to |
| @emph{refuse to respond to them} except to chide the sender to report |
| bugs properly. |
| |
| To enable us to fix the bug, you should include all these things: |
| |
| @itemize @bullet |
| @item |
| The version of @value{GDBN}. @value{GDBN} announces it if you start |
| with no arguments; you can also print it at any time using @code{show |
| version}. |
| |
| Without this, we will not know whether there is any point in looking for |
| the bug in the current version of @value{GDBN}. |
| |
| @item |
| The type of machine you are using, and the operating system name and |
| version number. |
| |
| @item |
| What compiler (and its version) was used to compile @value{GDBN}---e.g.@: |
| ``@value{GCC}--2.8.1''. |
| |
| @item |
| What compiler (and its version) was used to compile the program you are |
| debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP |
| C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version} |
| to get this information; for other compilers, see the documentation for |
| those compilers. |
| |
| @item |
| The command arguments you gave the compiler to compile your example and |
| observe the bug. For example, did you use @samp{-O}? To guarantee |
| you will not omit something important, list them all. A copy of the |
| Makefile (or the output from make) is sufficient. |
| |
| If we were to try to guess the arguments, we would probably guess wrong |
| and then we might not encounter the bug. |
| |
| @item |
| A complete input script, and all necessary source files, that will |
| reproduce the bug. |
| |
| @item |
| A description of what behavior you observe that you believe is |
| incorrect. For example, ``It gets a fatal signal.'' |
| |
| Of course, if the bug is that @value{GDBN} gets a fatal signal, then we |
| will certainly notice it. But if the bug is incorrect output, we might |
| not notice unless it is glaringly wrong. You might as well not give us |
| a chance to make a mistake. |
| |
| Even if the problem you experience is a fatal signal, you should still |
| say so explicitly. Suppose something strange is going on, such as, your |
| copy of @value{GDBN} is out of synch, or you have encountered a bug in |
| the C library on your system. (This has happened!) Your copy might |
| crash and ours would not. If you told us to expect a crash, then when |
| ours fails to crash, we would know that the bug was not happening for |
| us. If you had not told us to expect a crash, then we would not be able |
| to draw any conclusion from our observations. |
| |
| @pindex script |
| @cindex recording a session script |
| To collect all this information, you can use a session recording program |
| such as @command{script}, which is available on many Unix systems. |
| Just run your @value{GDBN} session inside @command{script} and then |
| include the @file{typescript} file with your bug report. |
| |
| Another way to record a @value{GDBN} session is to run @value{GDBN} |
| inside Emacs and then save the entire buffer to a file. |
| |
| @item |
| If you wish to suggest changes to the @value{GDBN} source, send us context |
| diffs. If you even discuss something in the @value{GDBN} source, refer to |
| it by context, not by line number. |
| |
| The line numbers in our development sources will not match those in your |
| sources. Your line numbers would convey no useful information to us. |
| |
| @end itemize |
| |
| Here are some things that are not necessary: |
| |
| @itemize @bullet |
| @item |
| A description of the envelope of the bug. |
| |
| Often people who encounter a bug spend a lot of time investigating |
| which changes to the input file will make the bug go away and which |
| changes will not affect it. |
| |
| This is often time consuming and not very useful, because the way we |
| will find the bug is by running a single example under the debugger |
| with breakpoints, not by pure deduction from a series of examples. |
| We recommend that you save your time for something else. |
| |
| Of course, if you can find a simpler example to report @emph{instead} |
| of the original one, that is a convenience for us. Errors in the |
| output will be easier to spot, running under the debugger will take |
| less time, and so on. |
| |
| However, simplification is not vital; if you do not want to do this, |
| report the bug anyway and send us the entire test case you used. |
| |
| @item |
| A patch for the bug. |
| |
| A patch for the bug does help us if it is a good one. But do not omit |
| the necessary information, such as the test case, on the assumption that |
| a patch is all we need. We might see problems with your patch and decide |
| to fix the problem another way, or we might not understand it at all. |
| |
| Sometimes with a program as complicated as @value{GDBN} it is very hard to |
| construct an example that will make the program follow a certain path |
| through the code. If you do not send us the example, we will not be able |
| to construct one, so we will not be able to verify that the bug is fixed. |
| |
| And if we cannot understand what bug you are trying to fix, or why your |
| patch should be an improvement, we will not install it. A test case will |
| help us to understand. |
| |
| @item |
| A guess about what the bug is or what it depends on. |
| |
| Such guesses are usually wrong. Even we cannot guess right about such |
| things without first using the debugger to find the facts. |
| @end itemize |
| |
| @c The readline documentation is distributed with the readline code |
| @c and consists of the two following files: |
| @c rluser.texi |
| @c hsuser.texi |
| @c Use -I with makeinfo to point to the appropriate directory, |
| @c environment var TEXINPUTS with TeX. |
| @ifclear SYSTEM_READLINE |
| @include rluser.texi |
| @include hsuser.texi |
| @end ifclear |
| |
| @node In Memoriam |
| @appendix In Memoriam |
| |
| The @value{GDBN} project mourns the loss of the following long-time |
| contributors: |
| |
| @table @code |
| @item Fred Fish |
| Fred was a long-standing contributor to @value{GDBN} (1991-2006), and |
| to Free Software in general. Outside of @value{GDBN}, he was known in |
| the Amiga world for his series of Fish Disks, and the GeekGadget project. |
| |
| @item Michael Snyder |
| Michael was one of the Global Maintainers of the @value{GDBN} project, |
| with contributions recorded as early as 1996, until 2011. In addition |
| to his day to day participation, he was a large driving force behind |
| adding Reverse Debugging to @value{GDBN}. |
| @end table |
| |
| Beyond their technical contributions to the project, they were also |
| enjoyable members of the Free Software Community. We will miss them. |
| |
| @node Formatting Documentation |
| @appendix Formatting Documentation |
| |
| @cindex @value{GDBN} reference card |
| @cindex reference card |
| The @value{GDBN} 4 release includes an already-formatted reference card, ready |
| for printing with PostScript or Ghostscript, in the @file{gdb} |
| subdirectory of the main source directory@footnote{In |
| @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN} |
| release.}. If you can use PostScript or Ghostscript with your printer, |
| you can print the reference card immediately with @file{refcard.ps}. |
| |
| The release also includes the source for the reference card. You |
| can format it, using @TeX{}, by typing: |
| |
| @smallexample |
| make refcard.dvi |
| @end smallexample |
| |
| The @value{GDBN} reference card is designed to print in @dfn{landscape} |
| mode on US ``letter'' size paper; |
| that is, on a sheet 11 inches wide by 8.5 inches |
| high. You will need to specify this form of printing as an option to |
| your @sc{dvi} output program. |
| |
| @cindex documentation |
| |
| All the documentation for @value{GDBN} comes as part of the machine-readable |
| distribution. The documentation is written in Texinfo format, which is |
| a documentation system that uses a single source file to produce both |
| on-line information and a printed manual. You can use one of the Info |
| formatting commands to create the on-line version of the documentation |
| and @TeX{} (or @code{texi2roff}) to typeset the printed version. |
| |
| @value{GDBN} includes an already formatted copy of the on-line Info |
| version of this manual in the @file{gdb} subdirectory. The main Info |
| file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to |
| subordinate files matching @samp{gdb.info*} in the same directory. If |
| necessary, you can print out these files, or read them with any editor; |
| but they are easier to read using the @code{info} subsystem in @sc{gnu} |
| Emacs or the standalone @code{info} program, available as part of the |
| @sc{gnu} Texinfo distribution. |
| |
| If you want to format these Info files yourself, you need one of the |
| Info formatting programs, such as @code{texinfo-format-buffer} or |
| @code{makeinfo}. |
| |
| If you have @code{makeinfo} installed, and are in the top level |
| @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of |
| version @value{GDBVN}), you can make the Info file by typing: |
| |
| @smallexample |
| cd gdb |
| make gdb.info |
| @end smallexample |
| |
| If you want to typeset and print copies of this manual, you need @TeX{}, |
| a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the |
| Texinfo definitions file. |
| |
| @TeX{} is a typesetting program; it does not print files directly, but |
| produces output files called @sc{dvi} files. To print a typeset |
| document, you need a program to print @sc{dvi} files. If your system |
| has @TeX{} installed, chances are it has such a program. The precise |
| command to use depends on your system; @kbd{lpr -d} is common; another |
| (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may |
| require a file name without any extension or a @samp{.dvi} extension. |
| |
| @TeX{} also requires a macro definitions file called |
| @file{texinfo.tex}. This file tells @TeX{} how to typeset a document |
| written in Texinfo format. On its own, @TeX{} cannot either read or |
| typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB |
| and is located in the @file{gdb-@var{version-number}/texinfo} |
| directory. |
| |
| If you have @TeX{} and a @sc{dvi} printer program installed, you can |
| typeset and print this manual. First switch to the @file{gdb} |
| subdirectory of the main source directory (for example, to |
| @file{gdb-@value{GDBVN}/gdb}) and type: |
| |
| @smallexample |
| make gdb.dvi |
| @end smallexample |
| |
| Then give @file{gdb.dvi} to your @sc{dvi} printing program. |
| |
| @node Installing GDB |
| @appendix Installing @value{GDBN} |
| @cindex installation |
| |
| @menu |
| * Requirements:: Requirements for building @value{GDBN} |
| * Running Configure:: Invoking the @value{GDBN} @file{configure} script |
| * Separate Objdir:: Compiling @value{GDBN} in another directory |
| * Config Names:: Specifying names for hosts and targets |
| * Configure Options:: Summary of options for configure |
| * System-wide configuration:: Having a system-wide init file |
| @end menu |
| |
| @node Requirements |
| @section Requirements for Building @value{GDBN} |
| @cindex building @value{GDBN}, requirements for |
| |
| Building @value{GDBN} requires various tools and packages to be available. |
| Other packages will be used only if they are found. |
| |
| @heading Tools/Packages Necessary for Building @value{GDBN} |
| @table @asis |
| @item ISO C90 compiler |
| @value{GDBN} is written in ISO C90. It should be buildable with any |
| working C90 compiler, e.g.@: GCC. |
| |
| @end table |
| |
| @heading Tools/Packages Optional for Building @value{GDBN} |
| @table @asis |
| @item Expat |
| @anchor{Expat} |
| @value{GDBN} can use the Expat XML parsing library. This library may be |
| included with your operating system distribution; if it is not, you |
| can get the latest version from @url{http://expat.sourceforge.net}. |
| The @file{configure} script will search for this library in several |
| standard locations; if it is installed in an unusual path, you can |
| use the @option{--with-libexpat-prefix} option to specify its location. |
| |
| Expat is used for: |
| |
| @itemize @bullet |
| @item |
| Remote protocol memory maps (@pxref{Memory Map Format}) |
| @item |
| Target descriptions (@pxref{Target Descriptions}) |
| @item |
| Remote shared library lists (@xref{Library List Format}, |
| or alternatively @pxref{Library List Format for SVR4 Targets}) |
| @item |
| MS-Windows shared libraries (@pxref{Shared Libraries}) |
| @item |
| Traceframe info (@pxref{Traceframe Info Format}) |
| @end itemize |
| |
| @item zlib |
| @cindex compressed debug sections |
| @value{GDBN} will use the @samp{zlib} library, if available, to read |
| compressed debug sections. Some linkers, such as GNU gold, are capable |
| of producing binaries with compressed debug sections. If @value{GDBN} |
| is compiled with @samp{zlib}, it will be able to read the debug |
| information in such binaries. |
| |
| The @samp{zlib} library is likely included with your operating system |
| distribution; if it is not, you can get the latest version from |
| @url{http://zlib.net}. |
| |
| @item iconv |
| @value{GDBN}'s features related to character sets (@pxref{Character |
| Sets}) require a functioning @code{iconv} implementation. If you are |
| on a GNU system, then this is provided by the GNU C Library. Some |
| other systems also provide a working @code{iconv}. |
| |
| If @value{GDBN} is using the @code{iconv} program which is installed |
| in a non-standard place, you will need to tell @value{GDBN} where to find it. |
| This is done with @option{--with-iconv-bin} which specifies the |
| directory that contains the @code{iconv} program. |
| |
| On systems without @code{iconv}, you can install GNU Libiconv. If you |
| have previously installed Libiconv, you can use the |
| @option{--with-libiconv-prefix} option to configure. |
| |
| @value{GDBN}'s top-level @file{configure} and @file{Makefile} will |
| arrange to build Libiconv if a directory named @file{libiconv} appears |
| in the top-most source directory. If Libiconv is built this way, and |
| if the operating system does not provide a suitable @code{iconv} |
| implementation, then the just-built library will automatically be used |
| by @value{GDBN}. One easy way to set this up is to download GNU |
| Libiconv, unpack it, and then rename the directory holding the |
| Libiconv source code to @samp{libiconv}. |
| @end table |
| |
| @node Running Configure |
| @section Invoking the @value{GDBN} @file{configure} Script |
| @cindex configuring @value{GDBN} |
| @value{GDBN} comes with a @file{configure} script that automates the process |
| of preparing @value{GDBN} for installation; you can then use @code{make} to |
| build the @code{gdb} program. |
| @iftex |
| @c irrelevant in info file; it's as current as the code it lives with. |
| @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN}, |
| look at the @file{README} file in the sources; we may have improved the |
| installation procedures since publishing this manual.} |
| @end iftex |
| |
| The @value{GDBN} distribution includes all the source code you need for |
| @value{GDBN} in a single directory, whose name is usually composed by |
| appending the version number to @samp{gdb}. |
| |
| For example, the @value{GDBN} version @value{GDBVN} distribution is in the |
| @file{gdb-@value{GDBVN}} directory. That directory contains: |
| |
| @table @code |
| @item gdb-@value{GDBVN}/configure @r{(and supporting files)} |
| script for configuring @value{GDBN} and all its supporting libraries |
| |
| @item gdb-@value{GDBVN}/gdb |
| the source specific to @value{GDBN} itself |
| |
| @item gdb-@value{GDBVN}/bfd |
| source for the Binary File Descriptor library |
| |
| @item gdb-@value{GDBVN}/include |
| @sc{gnu} include files |
| |
| @item gdb-@value{GDBVN}/libiberty |
| source for the @samp{-liberty} free software library |
| |
| @item gdb-@value{GDBVN}/opcodes |
| source for the library of opcode tables and disassemblers |
| |
| @item gdb-@value{GDBVN}/readline |
| source for the @sc{gnu} command-line interface |
| |
| @item gdb-@value{GDBVN}/glob |
| source for the @sc{gnu} filename pattern-matching subroutine |
| |
| @item gdb-@value{GDBVN}/mmalloc |
| source for the @sc{gnu} memory-mapped malloc package |
| @end table |
| |
| The simplest way to configure and build @value{GDBN} is to run @file{configure} |
| from the @file{gdb-@var{version-number}} source directory, which in |
| this example is the @file{gdb-@value{GDBVN}} directory. |
| |
| First switch to the @file{gdb-@var{version-number}} source directory |
| if you are not already in it; then run @file{configure}. Pass the |
| identifier for the platform on which @value{GDBN} will run as an |
| argument. |
| |
| For example: |
| |
| @smallexample |
| cd gdb-@value{GDBVN} |
| ./configure @var{host} |
| make |
| @end smallexample |
| |
| @noindent |
| where @var{host} is an identifier such as @samp{sun4} or |
| @samp{decstation}, that identifies the platform where @value{GDBN} will run. |
| (You can often leave off @var{host}; @file{configure} tries to guess the |
| correct value by examining your system.) |
| |
| Running @samp{configure @var{host}} and then running @code{make} builds the |
| @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty} |
| libraries, then @code{gdb} itself. The configured source files, and the |
| binaries, are left in the corresponding source directories. |
| |
| @need 750 |
| @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your |
| system does not recognize this automatically when you run a different |
| shell, you may need to run @code{sh} on it explicitly: |
| |
| @smallexample |
| sh configure @var{host} |
| @end smallexample |
| |
| If you run @file{configure} from a directory that contains source |
| directories for multiple libraries or programs, such as the |
| @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, |
| @file{configure} |
| creates configuration files for every directory level underneath (unless |
| you tell it not to, with the @samp{--norecursion} option). |
| |
| You should run the @file{configure} script from the top directory in the |
| source tree, the @file{gdb-@var{version-number}} directory. If you run |
| @file{configure} from one of the subdirectories, you will configure only |
| that subdirectory. That is usually not what you want. In particular, |
| if you run the first @file{configure} from the @file{gdb} subdirectory |
| of the @file{gdb-@var{version-number}} directory, you will omit the |
| configuration of @file{bfd}, @file{readline}, and other sibling |
| directories of the @file{gdb} subdirectory. This leads to build errors |
| about missing include files such as @file{bfd/bfd.h}. |
| |
| You can install @code{@value{GDBP}} anywhere; it has no hardwired paths. |
| However, you should make sure that the shell on your path (named by |
| the @samp{SHELL} environment variable) is publicly readable. Remember |
| that @value{GDBN} uses the shell to start your program---some systems refuse to |
| let @value{GDBN} debug child processes whose programs are not readable. |
| |
| @node Separate Objdir |
| @section Compiling @value{GDBN} in Another Directory |
| |
| If you want to run @value{GDBN} versions for several host or target machines, |
| you need a different @code{gdb} compiled for each combination of |
| host and target. @file{configure} is designed to make this easy by |
| allowing you to generate each configuration in a separate subdirectory, |
| rather than in the source directory. If your @code{make} program |
| handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running |
| @code{make} in each of these directories builds the @code{gdb} |
| program specified there. |
| |
| To build @code{gdb} in a separate directory, run @file{configure} |
| with the @samp{--srcdir} option to specify where to find the source. |
| (You also need to specify a path to find @file{configure} |
| itself from your working directory. If the path to @file{configure} |
| would be the same as the argument to @samp{--srcdir}, you can leave out |
| the @samp{--srcdir} option; it is assumed.) |
| |
| For example, with version @value{GDBVN}, you can build @value{GDBN} in a |
| separate directory for a Sun 4 like this: |
| |
| @smallexample |
| @group |
| cd gdb-@value{GDBVN} |
| mkdir ../gdb-sun4 |
| cd ../gdb-sun4 |
| ../gdb-@value{GDBVN}/configure sun4 |
| make |
| @end group |
| @end smallexample |
| |
| When @file{configure} builds a configuration using a remote source |
| directory, it creates a tree for the binaries with the same structure |
| (and using the same names) as the tree under the source directory. In |
| the example, you'd find the Sun 4 library @file{libiberty.a} in the |
| directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in |
| @file{gdb-sun4/gdb}. |
| |
| Make sure that your path to the @file{configure} script has just one |
| instance of @file{gdb} in it. If your path to @file{configure} looks |
| like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only |
| one subdirectory of @value{GDBN}, not the whole package. This leads to |
| build errors about missing include files such as @file{bfd/bfd.h}. |
| |
| One popular reason to build several @value{GDBN} configurations in separate |
| directories is to configure @value{GDBN} for cross-compiling (where |
| @value{GDBN} runs on one machine---the @dfn{host}---while debugging |
| programs that run on another machine---the @dfn{target}). |
| You specify a cross-debugging target by |
| giving the @samp{--target=@var{target}} option to @file{configure}. |
| |
| When you run @code{make} to build a program or library, you must run |
| it in a configured directory---whatever directory you were in when you |
| called @file{configure} (or one of its subdirectories). |
| |
| The @code{Makefile} that @file{configure} generates in each source |
| directory also runs recursively. If you type @code{make} in a source |
| directory such as @file{gdb-@value{GDBVN}} (or in a separate configured |
| directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you |
| will build all the required libraries, and then build GDB. |
| |
| When you have multiple hosts or targets configured in separate |
| directories, you can run @code{make} on them in parallel (for example, |
| if they are NFS-mounted on each of the hosts); they will not interfere |
| with each other. |
| |
| @node Config Names |
| @section Specifying Names for Hosts and Targets |
| |
| The specifications used for hosts and targets in the @file{configure} |
| script are based on a three-part naming scheme, but some short predefined |
| aliases are also supported. The full naming scheme encodes three pieces |
| of information in the following pattern: |
| |
| @smallexample |
| @var{architecture}-@var{vendor}-@var{os} |
| @end smallexample |
| |
| For example, you can use the alias @code{sun4} as a @var{host} argument, |
| or as the value for @var{target} in a @code{--target=@var{target}} |
| option. The equivalent full name is @samp{sparc-sun-sunos4}. |
| |
| The @file{configure} script accompanying @value{GDBN} does not provide |
| any query facility to list all supported host and target names or |
| aliases. @file{configure} calls the Bourne shell script |
| @code{config.sub} to map abbreviations to full names; you can read the |
| script, if you wish, or you can use it to test your guesses on |
| abbreviations---for example: |
| |
| @smallexample |
| % sh config.sub i386-linux |
| i386-pc-linux-gnu |
| % sh config.sub alpha-linux |
| alpha-unknown-linux-gnu |
| % sh config.sub hp9k700 |
| hppa1.1-hp-hpux |
| % sh config.sub sun4 |
| sparc-sun-sunos4.1.1 |
| % sh config.sub sun3 |
| m68k-sun-sunos4.1.1 |
| % sh config.sub i986v |
| Invalid configuration `i986v': machine `i986v' not recognized |
| @end smallexample |
| |
| @noindent |
| @code{config.sub} is also distributed in the @value{GDBN} source |
| directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}). |
| |
| @node Configure Options |
| @section @file{configure} Options |
| |
| Here is a summary of the @file{configure} options and arguments that |
| are most often useful for building @value{GDBN}. @file{configure} also has |
| several other options not listed here. @inforef{What Configure |
| Does,,configure.info}, for a full explanation of @file{configure}. |
| |
| @smallexample |
| configure @r{[}--help@r{]} |
| @r{[}--prefix=@var{dir}@r{]} |
| @r{[}--exec-prefix=@var{dir}@r{]} |
| @r{[}--srcdir=@var{dirname}@r{]} |
| @r{[}--norecursion@r{]} @r{[}--rm@r{]} |
| @r{[}--target=@var{target}@r{]} |
| @var{host} |
| @end smallexample |
| |
| @noindent |
| You may introduce options with a single @samp{-} rather than |
| @samp{--} if you prefer; but you may abbreviate option names if you use |
| @samp{--}. |
| |
| @table @code |
| @item --help |
| Display a quick summary of how to invoke @file{configure}. |
| |
| @item --prefix=@var{dir} |
| Configure the source to install programs and files under directory |
| @file{@var{dir}}. |
| |
| @item --exec-prefix=@var{dir} |
| Configure the source to install programs under directory |
| @file{@var{dir}}. |
| |
| @c avoid splitting the warning from the explanation: |
| @need 2000 |
| @item --srcdir=@var{dirname} |
| @strong{Warning: using this option requires @sc{gnu} @code{make}, or another |
| @code{make} that implements the @code{VPATH} feature.}@* |
| Use this option to make configurations in directories separate from the |
| @value{GDBN} source directories. Among other things, you can use this to |
| build (or maintain) several configurations simultaneously, in separate |
| directories. @file{configure} writes configuration-specific files in |
| the current directory, but arranges for them to use the source in the |
| directory @var{dirname}. @file{configure} creates directories under |
| the working directory in parallel to the source directories below |
| @var{dirname}. |
| |
| @item --norecursion |
| Configure only the directory level where @file{configure} is executed; do not |
| propagate configuration to subdirectories. |
| |
| @item --target=@var{target} |
| Configure @value{GDBN} for cross-debugging programs running on the specified |
| @var{target}. Without this option, @value{GDBN} is configured to debug |
| programs that run on the same machine (@var{host}) as @value{GDBN} itself. |
| |
| There is no convenient way to generate a list of all available targets. |
| |
| @item @var{host} @dots{} |
| Configure @value{GDBN} to run on the specified @var{host}. |
| |
| There is no convenient way to generate a list of all available hosts. |
| @end table |
| |
| There are many other options available as well, but they are generally |
| needed for special purposes only. |
| |
| @node System-wide configuration |
| @section System-wide configuration and settings |
| @cindex system-wide init file |
| |
| @value{GDBN} can be configured to have a system-wide init file; |
| this file will be read and executed at startup (@pxref{Startup, , What |
| @value{GDBN} does during startup}). |
| |
| Here is the corresponding configure option: |
| |
| @table @code |
| @item --with-system-gdbinit=@var{file} |
| Specify that the default location of the system-wide init file is |
| @var{file}. |
| @end table |
| |
| If @value{GDBN} has been configured with the option @option{--prefix=$prefix}, |
| it may be subject to relocation. Two possible cases: |
| |
| @itemize @bullet |
| @item |
| If the default location of this init file contains @file{$prefix}, |
| it will be subject to relocation. Suppose that the configure options |
| are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit}; |
| if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system |
| init file is looked for as @file{$install/etc/gdbinit} instead of |
| @file{$prefix/etc/gdbinit}. |
| |
| @item |
| By contrast, if the default location does not contain the prefix, |
| it will not be relocated. E.g.@: if @value{GDBN} has been configured with |
| @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit}, |
| then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit}, |
| wherever @value{GDBN} is installed. |
| @end itemize |
| |
| @node Maintenance Commands |
| @appendix Maintenance Commands |
| @cindex maintenance commands |
| @cindex internal commands |
| |
| In addition to commands intended for @value{GDBN} users, @value{GDBN} |
| includes a number of commands intended for @value{GDBN} developers, |
| that are not documented elsewhere in this manual. These commands are |
| provided here for reference. (For commands that turn on debugging |
| messages, see @ref{Debugging Output}.) |
| |
| @table @code |
| @kindex maint agent |
| @kindex maint agent-eval |
| @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression} |
| @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression} |
| Translate the given @var{expression} into remote agent bytecodes. |
| This command is useful for debugging the Agent Expression mechanism |
| (@pxref{Agent Expressions}). The @samp{agent} version produces an |
| expression useful for data collection, such as by tracepoints, while |
| @samp{maint agent-eval} produces an expression that evaluates directly |
| to a result. For instance, a collection expression for @code{globa + |
| globb} will include bytecodes to record four bytes of memory at each |
| of the addresses of @code{globa} and @code{globb}, while discarding |
| the result of the addition, while an evaluation expression will do the |
| addition and return the sum. |
| If @code{-at} is given, generate remote agent bytecode for @var{location}. |
| If not, generate remote agent bytecode for current frame PC address. |
| |
| @kindex maint agent-printf |
| @item maint agent-printf @var{format},@var{expr},... |
| Translate the given format string and list of argument expressions |
| into remote agent bytecodes and display them as a disassembled list. |
| This command is useful for debugging the agent version of dynamic |
| printf (@pxref{Dynamic Printf}. |
| |
| @kindex maint info breakpoints |
| @item @anchor{maint info breakpoints}maint info breakpoints |
| Using the same format as @samp{info breakpoints}, display both the |
| breakpoints you've set explicitly, and those @value{GDBN} is using for |
| internal purposes. Internal breakpoints are shown with negative |
| breakpoint numbers. The type column identifies what kind of breakpoint |
| is shown: |
| |
| @table @code |
| @item breakpoint |
| Normal, explicitly set breakpoint. |
| |
| @item watchpoint |
| Normal, explicitly set watchpoint. |
| |
| @item longjmp |
| Internal breakpoint, used to handle correctly stepping through |
| @code{longjmp} calls. |
| |
| @item longjmp resume |
| Internal breakpoint at the target of a @code{longjmp}. |
| |
| @item until |
| Temporary internal breakpoint used by the @value{GDBN} @code{until} command. |
| |
| @item finish |
| Temporary internal breakpoint used by the @value{GDBN} @code{finish} command. |
| |
| @item shlib events |
| Shared library events. |
| |
| @end table |
| |
| @kindex set displaced-stepping |
| @kindex show displaced-stepping |
| @cindex displaced stepping support |
| @cindex out-of-line single-stepping |
| @item set displaced-stepping |
| @itemx show displaced-stepping |
| Control whether or not @value{GDBN} will do @dfn{displaced stepping} |
| if the target supports it. Displaced stepping is a way to single-step |
| over breakpoints without removing them from the inferior, by executing |
| an out-of-line copy of the instruction that was originally at the |
| breakpoint location. It is also known as out-of-line single-stepping. |
| |
| @table @code |
| @item set displaced-stepping on |
| If the target architecture supports it, @value{GDBN} will use |
| displaced stepping to step over breakpoints. |
| |
| @item set displaced-stepping off |
| @value{GDBN} will not use displaced stepping to step over breakpoints, |
| even if such is supported by the target architecture. |
| |
| @cindex non-stop mode, and @samp{set displaced-stepping} |
| @item set displaced-stepping auto |
| This is the default mode. @value{GDBN} will use displaced stepping |
| only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target |
| architecture supports displaced stepping. |
| @end table |
| |
| @kindex maint check-symtabs |
| @item maint check-symtabs |
| Check the consistency of psymtabs and symtabs. |
| |
| @kindex maint cplus first_component |
| @item maint cplus first_component @var{name} |
| Print the first C@t{++} class/namespace component of @var{name}. |
| |
| @kindex maint cplus namespace |
| @item maint cplus namespace |
| Print the list of possible C@t{++} namespaces. |
| |
| @kindex maint demangle |
| @item maint demangle @var{name} |
| Demangle a C@t{++} or Objective-C mangled @var{name}. |
| |
| @kindex maint deprecate |
| @kindex maint undeprecate |
| @cindex deprecated commands |
| @item maint deprecate @var{command} @r{[}@var{replacement}@r{]} |
| @itemx maint undeprecate @var{command} |
| Deprecate or undeprecate the named @var{command}. Deprecated commands |
| cause @value{GDBN} to issue a warning when you use them. The optional |
| argument @var{replacement} says which newer command should be used in |
| favor of the deprecated one; if it is given, @value{GDBN} will mention |
| the replacement as part of the warning. |
| |
| @kindex maint dump-me |
| @item maint dump-me |
| @cindex @code{SIGQUIT} signal, dump core of @value{GDBN} |
| Cause a fatal signal in the debugger and force it to dump its core. |
| This is supported only on systems which support aborting a program |
| with the @code{SIGQUIT} signal. |
| |
| @kindex maint internal-error |
| @kindex maint internal-warning |
| @item maint internal-error @r{[}@var{message-text}@r{]} |
| @itemx maint internal-warning @r{[}@var{message-text}@r{]} |
| Cause @value{GDBN} to call the internal function @code{internal_error} |
| or @code{internal_warning} and hence behave as though an internal error |
| or internal warning has been detected. In addition to reporting the |
| internal problem, these functions give the user the opportunity to |
| either quit @value{GDBN} or create a core file of the current |
| @value{GDBN} session. |
| |
| These commands take an optional parameter @var{message-text} that is |
| used as the text of the error or warning message. |
| |
| Here's an example of using @code{internal-error}: |
| |
| @smallexample |
| (@value{GDBP}) @kbd{maint internal-error testing, 1, 2} |
| @dots{}/maint.c:121: internal-error: testing, 1, 2 |
| A problem internal to GDB has been detected. Further |
| debugging may prove unreliable. |
| Quit this debugging session? (y or n) @kbd{n} |
| Create a core file? (y or n) @kbd{n} |
| (@value{GDBP}) |
| @end smallexample |
| |
| @cindex @value{GDBN} internal error |
| @cindex internal errors, control of @value{GDBN} behavior |
| |
| @kindex maint set internal-error |
| @kindex maint show internal-error |
| @kindex maint set internal-warning |
| @kindex maint show internal-warning |
| @item maint set internal-error @var{action} [ask|yes|no] |
| @itemx maint show internal-error @var{action} |
| @itemx maint set internal-warning @var{action} [ask|yes|no] |
| @itemx maint show internal-warning @var{action} |
| When @value{GDBN} reports an internal problem (error or warning) it |
| gives the user the opportunity to both quit @value{GDBN} and create a |
| core file of the current @value{GDBN} session. These commands let you |
| override the default behaviour for each particular @var{action}, |
| described in the table below. |
| |
| @table @samp |
| @item quit |
| You can specify that @value{GDBN} should always (yes) or never (no) |
| quit. The default is to ask the user what to do. |
| |
| @item corefile |
| You can specify that @value{GDBN} should always (yes) or never (no) |
| create a core file. The default is to ask the user what to do. |
| @end table |
| |
| @kindex maint packet |
| @item maint packet @var{text} |
| If @value{GDBN} is talking to an inferior via the serial protocol, |
| then this command sends the string @var{text} to the inferior, and |
| displays the response packet. @value{GDBN} supplies the initial |
| @samp{$} character, the terminating @samp{#} character, and the |
| checksum. |
| |
| @kindex maint print architecture |
| @item maint print architecture @r{[}@var{file}@r{]} |
| Print the entire architecture configuration. The optional argument |
| @var{file} names the file where the output goes. |
| |
| @kindex maint print c-tdesc |
| @item maint print c-tdesc |
| Print the current target description (@pxref{Target Descriptions}) as |
| a C source file. The created source file can be used in @value{GDBN} |
| when an XML parser is not available to parse the description. |
| |
| @kindex maint print dummy-frames |
| @item maint print dummy-frames |
| Prints the contents of @value{GDBN}'s internal dummy-frame stack. |
| |
| @smallexample |
| (@value{GDBP}) @kbd{b add} |
| @dots{} |
| (@value{GDBP}) @kbd{print add(2,3)} |
| Breakpoint 2, add (a=2, b=3) at @dots{} |
| 58 return (a + b); |
| The program being debugged stopped while in a function called from GDB. |
| @dots{} |
| (@value{GDBP}) @kbd{maint print dummy-frames} |
| 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6 |
| top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@} |
| call_lo=0x01014000 call_hi=0x01014001 |
| (@value{GDBP}) |
| @end smallexample |
| |
| Takes an optional file parameter. |
| |
| @kindex maint print registers |
| @kindex maint print raw-registers |
| @kindex maint print cooked-registers |
| @kindex maint print register-groups |
| @kindex maint print remote-registers |
| @item maint print registers @r{[}@var{file}@r{]} |
| @itemx maint print raw-registers @r{[}@var{file}@r{]} |
| @itemx maint print cooked-registers @r{[}@var{file}@r{]} |
| @itemx maint print register-groups @r{[}@var{file}@r{]} |
| @itemx maint print remote-registers @r{[}@var{file}@r{]} |
| Print @value{GDBN}'s internal register data structures. |
| |
| The command @code{maint print raw-registers} includes the contents of |
| the raw register cache; the command @code{maint print |
| cooked-registers} includes the (cooked) value of all registers, |
| including registers which aren't available on the target nor visible |
| to user; the command @code{maint print register-groups} includes the |
| groups that each register is a member of; and the command @code{maint |
| print remote-registers} includes the remote target's register numbers |
| and offsets in the `G' packets. @xref{Registers,, Registers, gdbint, |
| @value{GDBN} Internals}. |
| |
| These commands take an optional parameter, a file name to which to |
| write the information. |
| |
| @kindex maint print reggroups |
| @item maint print reggroups @r{[}@var{file}@r{]} |
| Print @value{GDBN}'s internal register group data structures. The |
| optional argument @var{file} tells to what file to write the |
| information. |
| |
| The register groups info looks like this: |
| |
| @smallexample |
| (@value{GDBP}) @kbd{maint print reggroups} |
| Group Type |
| general user |
| float user |
| all user |
| vector user |
| system user |
| save internal |
| restore internal |
| @end smallexample |
| |
| @kindex flushregs |
| @item flushregs |
| This command forces @value{GDBN} to flush its internal register cache. |
| |
| @kindex maint print objfiles |
| @cindex info for known object files |
| @item maint print objfiles |
| Print a dump of all known object files. For each object file, this |
| command prints its name, address in memory, and all of its psymtabs |
| and symtabs. |
| |
| @kindex maint print section-scripts |
| @cindex info for known .debug_gdb_scripts-loaded scripts |
| @item maint print section-scripts [@var{regexp}] |
| Print a dump of scripts specified in the @code{.debug_gdb_section} section. |
| If @var{regexp} is specified, only print scripts loaded by object files |
| matching @var{regexp}. |
| For each script, this command prints its name as specified in the objfile, |
| and the full path if known. |
| @xref{dotdebug_gdb_scripts section}. |
| |
| @kindex maint print statistics |
| @cindex bcache statistics |
| @item maint print statistics |
| This command prints, for each object file in the program, various data |
| about that object file followed by the byte cache (@dfn{bcache}) |
| statistics for the object file. The objfile data includes the number |
| of minimal, partial, full, and stabs symbols, the number of types |
| defined by the objfile, the number of as yet unexpanded psym tables, |
| the number of line tables and string tables, and the amount of memory |
| used by the various tables. The bcache statistics include the counts, |
| sizes, and counts of duplicates of all and unique objects, max, |
| average, and median entry size, total memory used and its overhead and |
| savings, and various measures of the hash table size and chain |
| lengths. |
| |
| @kindex maint print target-stack |
| @cindex target stack description |
| @item maint print target-stack |
| A @dfn{target} is an interface between the debugger and a particular |
| kind of file or process. Targets can be stacked in @dfn{strata}, |
| so that more than one target can potentially respond to a request. |
| In particular, memory accesses will walk down the stack of targets |
| until they find a target that is interested in handling that particular |
| address. |
| |
| This command prints a short description of each layer that was pushed on |
| the @dfn{target stack}, starting from the top layer down to the bottom one. |
| |
| @kindex maint print type |
| @cindex type chain of a data type |
| @item maint print type @var{expr} |
| Print the type chain for a type specified by @var{expr}. The argument |
| can be either a type name or a symbol. If it is a symbol, the type of |
| that symbol is described. The type chain produced by this command is |
| a recursive definition of the data type as stored in @value{GDBN}'s |
| data structures, including its flags and contained types. |
| |
| @kindex maint set dwarf2 always-disassemble |
| @kindex maint show dwarf2 always-disassemble |
| @item maint set dwarf2 always-disassemble |
| @item maint show dwarf2 always-disassemble |
| Control the behavior of @code{info address} when using DWARF debugging |
| information. |
| |
| The default is @code{off}, which means that @value{GDBN} should try to |
| describe a variable's location in an easily readable format. When |
| @code{on}, @value{GDBN} will instead display the DWARF location |
| expression in an assembly-like format. Note that some locations are |
| too complex for @value{GDBN} to describe simply; in this case you will |
| always see the disassembly form. |
| |
| Here is an example of the resulting disassembly: |
| |
| @smallexample |
| (gdb) info addr argc |
| Symbol "argc" is a complex DWARF expression: |
| 1: DW_OP_fbreg 0 |
| @end smallexample |
| |
| For more information on these expressions, see |
| @uref{http://www.dwarfstd.org/, the DWARF standard}. |
| |
| @kindex maint set dwarf2 max-cache-age |
| @kindex maint show dwarf2 max-cache-age |
| @item maint set dwarf2 max-cache-age |
| @itemx maint show dwarf2 max-cache-age |
| Control the DWARF 2 compilation unit cache. |
| |
| @cindex DWARF 2 compilation units cache |
| In object files with inter-compilation-unit references, such as those |
| produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2 |
| reader needs to frequently refer to previously read compilation units. |
| This setting controls how long a compilation unit will remain in the |
| cache if it is not referenced. A higher limit means that cached |
| compilation units will be stored in memory longer, and more total |
| memory will be used. Setting it to zero disables caching, which will |
| slow down @value{GDBN} startup, but reduce memory consumption. |
| |
| @kindex maint set profile |
| @kindex maint show profile |
| @cindex profiling GDB |
| @item maint set profile |
| @itemx maint show profile |
| Control profiling of @value{GDBN}. |
| |
| Profiling will be disabled until you use the @samp{maint set profile} |
| command to enable it. When you enable profiling, the system will begin |
| collecting timing and execution count data; when you disable profiling or |
| exit @value{GDBN}, the results will be written to a log file. Remember that |
| if you use profiling, @value{GDBN} will overwrite the profiling log file |
| (often called @file{gmon.out}). If you have a record of important profiling |
| data in a @file{gmon.out} file, be sure to move it to a safe location. |
| |
| Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be |
| compiled with the @samp{-pg} compiler option. |
| |
| @kindex maint set show-debug-regs |
| @kindex maint show show-debug-regs |
| @cindex hardware debug registers |
| @item maint set show-debug-regs |
| @itemx maint show show-debug-regs |
| Control whether to show variables that mirror the hardware debug |
| registers. Use @code{ON} to enable, @code{OFF} to disable. If |
| enabled, the debug registers values are shown when @value{GDBN} inserts or |
| removes a hardware breakpoint or watchpoint, and when the inferior |
| triggers a hardware-assisted breakpoint or watchpoint. |
| |
| @kindex maint set show-all-tib |
| @kindex maint show show-all-tib |
| @item maint set show-all-tib |
| @itemx maint show show-all-tib |
| Control whether to show all non zero areas within a 1k block starting |
| at thread local base, when using the @samp{info w32 thread-information-block} |
| command. |
| |
| @kindex maint space |
| @cindex memory used by commands |
| @item maint space |
| Control whether to display memory usage for each command. If set to a |
| nonzero value, @value{GDBN} will display how much memory each command |
| took, following the command's own output. This can also be requested |
| by invoking @value{GDBN} with the @option{--statistics} command-line |
| switch (@pxref{Mode Options}). |
| |
| @kindex maint time |
| @cindex time of command execution |
| @item maint time |
| Control whether to display the execution time of @value{GDBN} for each command. |
| If set to a nonzero value, @value{GDBN} will display how much time it |
| took to execute each command, following the command's own output. |
| Both CPU time and wallclock time are printed. |
| Printing both is useful when trying to determine whether the cost is |
| CPU or, e.g., disk/network, latency. |
| Note that the CPU time printed is for @value{GDBN} only, it does not include |
| the execution time of the inferior because there's no mechanism currently |
| to compute how much time was spent by @value{GDBN} and how much time was |
| spent by the program been debugged. |
| This can also be requested by invoking @value{GDBN} with the |
| @option{--statistics} command-line switch (@pxref{Mode Options}). |
| |
| @kindex maint translate-address |
| @item maint translate-address @r{[}@var{section}@r{]} @var{addr} |
| Find the symbol stored at the location specified by the address |
| @var{addr} and an optional section name @var{section}. If found, |
| @value{GDBN} prints the name of the closest symbol and an offset from |
| the symbol's location to the specified address. This is similar to |
| the @code{info address} command (@pxref{Symbols}), except that this |
| command also allows to find symbols in other sections. |
| |
| If section was not specified, the section in which the symbol was found |
| is also printed. For dynamically linked executables, the name of |
| executable or shared library containing the symbol is printed as well. |
| |
| @end table |
| |
| The following command is useful for non-interactive invocations of |
| @value{GDBN}, such as in the test suite. |
| |
| @table @code |
| @item set watchdog @var{nsec} |
| @kindex set watchdog |
| @cindex watchdog timer |
| @cindex timeout for commands |
| Set the maximum number of seconds @value{GDBN} will wait for the |
| target operation to finish. If this time expires, @value{GDBN} |
| reports and error and the command is aborted. |
| |
| @item show watchdog |
| Show the current setting of the target wait timeout. |
| @end table |
| |
| @node Remote Protocol |
| @appendix @value{GDBN} Remote Serial Protocol |
| |
| @menu |
| * Overview:: |
| * Packets:: |
| * Stop Reply Packets:: |
| * General Query Packets:: |
| * Architecture-Specific Protocol Details:: |
| * Tracepoint Packets:: |
| * Host I/O Packets:: |
| * Interrupts:: |
| * Notification Packets:: |
| * Remote Non-Stop:: |
| * Packet Acknowledgment:: |
| * Examples:: |
| * File-I/O Remote Protocol Extension:: |
| * Library List Format:: |
| * Library List Format for SVR4 Targets:: |
| * Memory Map Format:: |
| * Thread List Format:: |
| * Traceframe Info Format:: |
| @end menu |
| |
| @node Overview |
| @section Overview |
| |
| There may be occasions when you need to know something about the |
| protocol---for example, if there is only one serial port to your target |
| machine, you might want your program to do something special if it |
| recognizes a packet meant for @value{GDBN}. |
| |
| In the examples below, @samp{->} and @samp{<-} are used to indicate |
| transmitted and received data, respectively. |
| |
| @cindex protocol, @value{GDBN} remote serial |
| @cindex serial protocol, @value{GDBN} remote |
| @cindex remote serial protocol |
| All @value{GDBN} commands and responses (other than acknowledgments |
| and notifications, see @ref{Notification Packets}) are sent as a |
| @var{packet}. A @var{packet} is introduced with the character |
| @samp{$}, the actual @var{packet-data}, and the terminating character |
| @samp{#} followed by a two-digit @var{checksum}: |
| |
| @smallexample |
| @code{$}@var{packet-data}@code{#}@var{checksum} |
| @end smallexample |
| @noindent |
| |
| @cindex checksum, for @value{GDBN} remote |
| @noindent |
| The two-digit @var{checksum} is computed as the modulo 256 sum of all |
| characters between the leading @samp{$} and the trailing @samp{#} (an |
| eight bit unsigned checksum). |
| |
| Implementors should note that prior to @value{GDBN} 5.0 the protocol |
| specification also included an optional two-digit @var{sequence-id}: |
| |
| @smallexample |
| @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum} |
| @end smallexample |
| |
| @cindex sequence-id, for @value{GDBN} remote |
| @noindent |
| That @var{sequence-id} was appended to the acknowledgment. @value{GDBN} |
| has never output @var{sequence-id}s. Stubs that handle packets added |
| since @value{GDBN} 5.0 must not accept @var{sequence-id}. |
| |
| When either the host or the target machine receives a packet, the first |
| response expected is an acknowledgment: either @samp{+} (to indicate |
| the package was received correctly) or @samp{-} (to request |
| retransmission): |
| |
| @smallexample |
| -> @code{$}@var{packet-data}@code{#}@var{checksum} |
| <- @code{+} |
| @end smallexample |
| @noindent |
| |
| The @samp{+}/@samp{-} acknowledgments can be disabled |
| once a connection is established. |
| @xref{Packet Acknowledgment}, for details. |
| |
| The host (@value{GDBN}) sends @var{command}s, and the target (the |
| debugging stub incorporated in your program) sends a @var{response}. In |
| the case of step and continue @var{command}s, the response is only sent |
| when the operation has completed, and the target has again stopped all |
| threads in all attached processes. This is the default all-stop mode |
| behavior, but the remote protocol also supports @value{GDBN}'s non-stop |
| execution mode; see @ref{Remote Non-Stop}, for details. |
| |
| @var{packet-data} consists of a sequence of characters with the |
| exception of @samp{#} and @samp{$} (see @samp{X} packet for additional |
| exceptions). |
| |
| @cindex remote protocol, field separator |
| Fields within the packet should be separated using @samp{,} @samp{;} or |
| @samp{:}. Except where otherwise noted all numbers are represented in |
| @sc{hex} with leading zeros suppressed. |
| |
| Implementors should note that prior to @value{GDBN} 5.0, the character |
| @samp{:} could not appear as the third character in a packet (as it |
| would potentially conflict with the @var{sequence-id}). |
| |
| @cindex remote protocol, binary data |
| @anchor{Binary Data} |
| Binary data in most packets is encoded either as two hexadecimal |
| digits per byte of binary data. This allowed the traditional remote |
| protocol to work over connections which were only seven-bit clean. |
| Some packets designed more recently assume an eight-bit clean |
| connection, and use a more efficient encoding to send and receive |
| binary data. |
| |
| The binary data representation uses @code{7d} (@sc{ascii} @samp{@}}) |
| as an escape character. Any escaped byte is transmitted as the escape |
| character followed by the original character XORed with @code{0x20}. |
| For example, the byte @code{0x7d} would be transmitted as the two |
| bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}), |
| @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii} |
| @samp{@}}) must always be escaped. Responses sent by the stub |
| must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it |
| is not interpreted as the start of a run-length encoded sequence |
| (described next). |
| |
| Response @var{data} can be run-length encoded to save space. |
| Run-length encoding replaces runs of identical characters with one |
| instance of the repeated character, followed by a @samp{*} and a |
| repeat count. The repeat count is itself sent encoded, to avoid |
| binary characters in @var{data}: a value of @var{n} is sent as |
| @code{@var{n}+29}. For a repeat count greater or equal to 3, this |
| produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii} |
| code 32) for a repeat count of 3. (This is because run-length |
| encoding starts to win for counts 3 or more.) Thus, for example, |
| @samp{0* } is a run-length encoding of ``0000'': the space character |
| after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 = |
| 3}} more times. |
| |
| The printable characters @samp{#} and @samp{$} or with a numeric value |
| greater than 126 must not be used. Runs of six repeats (@samp{#}) or |
| seven repeats (@samp{$}) can be expanded using a repeat count of only |
| five (@samp{"}). For example, @samp{00000000} can be encoded as |
| @samp{0*"00}. |
| |
| The error response returned for some packets includes a two character |
| error number. That number is not well defined. |
| |
| @cindex empty response, for unsupported packets |
| For any @var{command} not supported by the stub, an empty response |
| (@samp{$#00}) should be returned. That way it is possible to extend the |
| protocol. A newer @value{GDBN} can tell if a packet is supported based |
| on that response. |
| |
| At a minimum, a stub is required to support the @samp{g} and @samp{G} |
| commands for register access, and the @samp{m} and @samp{M} commands |
| for memory access. Stubs that only control single-threaded targets |
| can implement run control with the @samp{c} (continue), and @samp{s} |
| (step) commands. Stubs that support multi-threading targets should |
| support the @samp{vCont} command. All other commands are optional. |
| |
| @node Packets |
| @section Packets |
| |
| The following table provides a complete list of all currently defined |
| @var{command}s and their corresponding response @var{data}. |
| @xref{File-I/O Remote Protocol Extension}, for details about the File |
| I/O extension of the remote protocol. |
| |
| Each packet's description has a template showing the packet's overall |
| syntax, followed by an explanation of the packet's meaning. We |
| include spaces in some of the templates for clarity; these are not |
| part of the packet's syntax. No @value{GDBN} packet uses spaces to |
| separate its components. For example, a template like @samp{foo |
| @var{bar} @var{baz}} describes a packet beginning with the three ASCII |
| bytes @samp{foo}, followed by a @var{bar}, followed directly by a |
| @var{baz}. @value{GDBN} does not transmit a space character between the |
| @samp{foo} and the @var{bar}, or between the @var{bar} and the |
| @var{baz}. |
| |
| @cindex @var{thread-id}, in remote protocol |
| @anchor{thread-id syntax} |
| Several packets and replies include a @var{thread-id} field to identify |
| a thread. Normally these are positive numbers with a target-specific |
| interpretation, formatted as big-endian hex strings. A @var{thread-id} |
| can also be a literal @samp{-1} to indicate all threads, or @samp{0} to |
| pick any thread. |
| |
| In addition, the remote protocol supports a multiprocess feature in |
| which the @var{thread-id} syntax is extended to optionally include both |
| process and thread ID fields, as @samp{p@var{pid}.@var{tid}}. |
| The @var{pid} (process) and @var{tid} (thread) components each have the |
| format described above: a positive number with target-specific |
| interpretation formatted as a big-endian hex string, literal @samp{-1} |
| to indicate all processes or threads (respectively), or @samp{0} to |
| indicate an arbitrary process or thread. Specifying just a process, as |
| @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an |
| error to specify all processes but a specific thread, such as |
| @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used |
| for those packets and replies explicitly documented to include a process |
| ID, rather than a @var{thread-id}. |
| |
| The multiprocess @var{thread-id} syntax extensions are only used if both |
| @value{GDBN} and the stub report support for the @samp{multiprocess} |
| feature using @samp{qSupported}. @xref{multiprocess extensions}, for |
| more information. |
| |
| Note that all packet forms beginning with an upper- or lower-case |
| letter, other than those described here, are reserved for future use. |
| |
| Here are the packet descriptions. |
| |
| @table @samp |
| |
| @item ! |
| @cindex @samp{!} packet |
| @anchor{extended mode} |
| Enable extended mode. In extended mode, the remote server is made |
| persistent. The @samp{R} packet is used to restart the program being |
| debugged. |
| |
| Reply: |
| @table @samp |
| @item OK |
| The remote target both supports and has enabled extended mode. |
| @end table |
| |
| @item ? |
| @cindex @samp{?} packet |
| Indicate the reason the target halted. The reply is the same as for |
| step and continue. This packet has a special interpretation when the |
| target is in non-stop mode; see @ref{Remote Non-Stop}. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @item A @var{arglen},@var{argnum},@var{arg},@dots{} |
| @cindex @samp{A} packet |
| Initialized @code{argv[]} array passed into program. @var{arglen} |
| specifies the number of bytes in the hex encoded byte stream |
| @var{arg}. See @code{gdbserver} for more details. |
| |
| Reply: |
| @table @samp |
| @item OK |
| The arguments were set. |
| @item E @var{NN} |
| An error occurred. |
| @end table |
| |
| @item b @var{baud} |
| @cindex @samp{b} packet |
| (Don't use this packet; its behavior is not well-defined.) |
| Change the serial line speed to @var{baud}. |
| |
| JTC: @emph{When does the transport layer state change? When it's |
| received, or after the ACK is transmitted. In either case, there are |
| problems if the command or the acknowledgment packet is dropped.} |
| |
| Stan: @emph{If people really wanted to add something like this, and get |
| it working for the first time, they ought to modify ser-unix.c to send |
| some kind of out-of-band message to a specially-setup stub and have the |
| switch happen "in between" packets, so that from remote protocol's point |
| of view, nothing actually happened.} |
| |
| @item B @var{addr},@var{mode} |
| @cindex @samp{B} packet |
| Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a |
| breakpoint at @var{addr}. |
| |
| Don't use this packet. Use the @samp{Z} and @samp{z} packets instead |
| (@pxref{insert breakpoint or watchpoint packet}). |
| |
| @cindex @samp{bc} packet |
| @anchor{bc} |
| @item bc |
| Backward continue. Execute the target system in reverse. No parameter. |
| @xref{Reverse Execution}, for more information. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @cindex @samp{bs} packet |
| @anchor{bs} |
| @item bs |
| Backward single step. Execute one instruction in reverse. No parameter. |
| @xref{Reverse Execution}, for more information. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @item c @r{[}@var{addr}@r{]} |
| @cindex @samp{c} packet |
| Continue. @var{addr} is address to resume. If @var{addr} is omitted, |
| resume at current address. |
| |
| This packet is deprecated for multi-threading support. @xref{vCont |
| packet}. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @item C @var{sig}@r{[};@var{addr}@r{]} |
| @cindex @samp{C} packet |
| Continue with signal @var{sig} (hex signal number). If |
| @samp{;@var{addr}} is omitted, resume at same address. |
| |
| This packet is deprecated for multi-threading support. @xref{vCont |
| packet}. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @item d |
| @cindex @samp{d} packet |
| Toggle debug flag. |
| |
| Don't use this packet; instead, define a general set packet |
| (@pxref{General Query Packets}). |
| |
| @item D |
| @itemx D;@var{pid} |
| @cindex @samp{D} packet |
| The first form of the packet is used to detach @value{GDBN} from the |
| remote system. It is sent to the remote target |
| before @value{GDBN} disconnects via the @code{detach} command. |
| |
| The second form, including a process ID, is used when multiprocess |
| protocol extensions are enabled (@pxref{multiprocess extensions}), to |
| detach only a specific process. The @var{pid} is specified as a |
| big-endian hex string. |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item F @var{RC},@var{EE},@var{CF};@var{XX} |
| @cindex @samp{F} packet |
| A reply from @value{GDBN} to an @samp{F} packet sent by the target. |
| This is part of the File-I/O protocol extension. @xref{File-I/O |
| Remote Protocol Extension}, for the specification. |
| |
| @item g |
| @anchor{read registers packet} |
| @cindex @samp{g} packet |
| Read general registers. |
| |
| Reply: |
| @table @samp |
| @item @var{XX@dots{}} |
| Each byte of register data is described by two hex digits. The bytes |
| with the register are transmitted in target byte order. The size of |
| each register and their position within the @samp{g} packet are |
| determined by the @value{GDBN} internal gdbarch functions |
| @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The |
| specification of several standard @samp{g} packets is specified below. |
| |
| When reading registers from a trace frame (@pxref{Analyze Collected |
| Data,,Using the Collected Data}), the stub may also return a string of |
| literal @samp{x}'s in place of the register data digits, to indicate |
| that the corresponding register has not been collected, thus its value |
| is unavailable. For example, for an architecture with 4 registers of |
| 4 bytes each, the following reply indicates to @value{GDBN} that |
| registers 0 and 2 have not been collected, while registers 1 and 3 |
| have been collected, and both have zero value: |
| |
| @smallexample |
| -> @code{g} |
| <- @code{xxxxxxxx00000000xxxxxxxx00000000} |
| @end smallexample |
| |
| @item E @var{NN} |
| for an error. |
| @end table |
| |
| @item G @var{XX@dots{}} |
| @cindex @samp{G} packet |
| Write general registers. @xref{read registers packet}, for a |
| description of the @var{XX@dots{}} data. |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item H @var{op} @var{thread-id} |
| @cindex @samp{H} packet |
| Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g}, |
| @samp{G}, et.al.). @var{op} depends on the operation to be performed: |
| it should be @samp{c} for step and continue operations (note that this |
| is deprecated, supporting the @samp{vCont} command is a better |
| option), @samp{g} for other operations. The thread designator |
| @var{thread-id} has the format and interpretation described in |
| @ref{thread-id syntax}. |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @c FIXME: JTC: |
| @c 'H': How restrictive (or permissive) is the thread model. If a |
| @c thread is selected and stopped, are other threads allowed |
| @c to continue to execute? As I mentioned above, I think the |
| @c semantics of each command when a thread is selected must be |
| @c described. For example: |
| @c |
| @c 'g': If the stub supports threads and a specific thread is |
| @c selected, returns the register block from that thread; |
| @c otherwise returns current registers. |
| @c |
| @c 'G' If the stub supports threads and a specific thread is |
| @c selected, sets the registers of the register block of |
| @c that thread; otherwise sets current registers. |
| |
| @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]} |
| @anchor{cycle step packet} |
| @cindex @samp{i} packet |
| Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is |
| present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle |
| step starting at that address. |
| |
| @item I |
| @cindex @samp{I} packet |
| Signal, then cycle step. @xref{step with signal packet}. @xref{cycle |
| step packet}. |
| |
| @item k |
| @cindex @samp{k} packet |
| Kill request. |
| |
| FIXME: @emph{There is no description of how to operate when a specific |
| thread context has been selected (i.e.@: does 'k' kill only that |
| thread?)}. |
| |
| @item m @var{addr},@var{length} |
| @cindex @samp{m} packet |
| Read @var{length} bytes of memory starting at address @var{addr}. |
| Note that @var{addr} may not be aligned to any particular boundary. |
| |
| The stub need not use any particular size or alignment when gathering |
| data from memory for the response; even if @var{addr} is word-aligned |
| and @var{length} is a multiple of the word size, the stub is free to |
| use byte accesses, or not. For this reason, this packet may not be |
| suitable for accessing memory-mapped I/O devices. |
| @cindex alignment of remote memory accesses |
| @cindex size of remote memory accesses |
| @cindex memory, alignment and size of remote accesses |
| |
| Reply: |
| @table @samp |
| @item @var{XX@dots{}} |
| Memory contents; each byte is transmitted as a two-digit hexadecimal |
| number. The reply may contain fewer bytes than requested if the |
| server was able to read only part of the region of memory. |
| @item E @var{NN} |
| @var{NN} is errno |
| @end table |
| |
| @item M @var{addr},@var{length}:@var{XX@dots{}} |
| @cindex @samp{M} packet |
| Write @var{length} bytes of memory starting at address @var{addr}. |
| @var{XX@dots{}} is the data; each byte is transmitted as a two-digit |
| hexadecimal number. |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E @var{NN} |
| for an error (this includes the case where only part of the data was |
| written). |
| @end table |
| |
| @item p @var{n} |
| @cindex @samp{p} packet |
| Read the value of register @var{n}; @var{n} is in hex. |
| @xref{read registers packet}, for a description of how the returned |
| register value is encoded. |
| |
| Reply: |
| @table @samp |
| @item @var{XX@dots{}} |
| the register's value |
| @item E @var{NN} |
| for an error |
| @item |
| Indicating an unrecognized @var{query}. |
| @end table |
| |
| @item P @var{n@dots{}}=@var{r@dots{}} |
| @anchor{write register packet} |
| @cindex @samp{P} packet |
| Write register @var{n@dots{}} with value @var{r@dots{}}. The register |
| number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex |
| digits for each byte in the register (target byte order). |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item q @var{name} @var{params}@dots{} |
| @itemx Q @var{name} @var{params}@dots{} |
| @cindex @samp{q} packet |
| @cindex @samp{Q} packet |
| General query (@samp{q}) and set (@samp{Q}). These packets are |
| described fully in @ref{General Query Packets}. |
| |
| @item r |
| @cindex @samp{r} packet |
| Reset the entire system. |
| |
| Don't use this packet; use the @samp{R} packet instead. |
| |
| @item R @var{XX} |
| @cindex @samp{R} packet |
| Restart the program being debugged. @var{XX}, while needed, is ignored. |
| This packet is only available in extended mode (@pxref{extended mode}). |
| |
| The @samp{R} packet has no reply. |
| |
| @item s @r{[}@var{addr}@r{]} |
| @cindex @samp{s} packet |
| Single step. @var{addr} is the address at which to resume. If |
| @var{addr} is omitted, resume at same address. |
| |
| This packet is deprecated for multi-threading support. @xref{vCont |
| packet}. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @item S @var{sig}@r{[};@var{addr}@r{]} |
| @anchor{step with signal packet} |
| @cindex @samp{S} packet |
| Step with signal. This is analogous to the @samp{C} packet, but |
| requests a single-step, rather than a normal resumption of execution. |
| |
| This packet is deprecated for multi-threading support. @xref{vCont |
| packet}. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @item t @var{addr}:@var{PP},@var{MM} |
| @cindex @samp{t} packet |
| Search backwards starting at address @var{addr} for a match with pattern |
| @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes. |
| @var{addr} must be at least 3 digits. |
| |
| @item T @var{thread-id} |
| @cindex @samp{T} packet |
| Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}. |
| |
| Reply: |
| @table @samp |
| @item OK |
| thread is still alive |
| @item E @var{NN} |
| thread is dead |
| @end table |
| |
| @item v |
| Packets starting with @samp{v} are identified by a multi-letter name, |
| up to the first @samp{;} or @samp{?} (or the end of the packet). |
| |
| @item vAttach;@var{pid} |
| @cindex @samp{vAttach} packet |
| Attach to a new process with the specified process ID @var{pid}. |
| The process ID is a |
| hexadecimal integer identifying the process. In all-stop mode, all |
| threads in the attached process are stopped; in non-stop mode, it may be |
| attached without being stopped if that is supported by the target. |
| |
| @c In non-stop mode, on a successful vAttach, the stub should set the |
| @c current thread to a thread of the newly-attached process. After |
| @c attaching, GDB queries for the attached process's thread ID with qC. |
| @c Also note that, from a user perspective, whether or not the |
| @c target is stopped on attach in non-stop mode depends on whether you |
| @c use the foreground or background version of the attach command, not |
| @c on what vAttach does; GDB does the right thing with respect to either |
| @c stopping or restarting threads. |
| |
| This packet is only available in extended mode (@pxref{extended mode}). |
| |
| Reply: |
| @table @samp |
| @item E @var{nn} |
| for an error |
| @item @r{Any stop packet} |
| for success in all-stop mode (@pxref{Stop Reply Packets}) |
| @item OK |
| for success in non-stop mode (@pxref{Remote Non-Stop}) |
| @end table |
| |
| @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{} |
| @cindex @samp{vCont} packet |
| @anchor{vCont packet} |
| Resume the inferior, specifying different actions for each thread. |
| If an action is specified with no @var{thread-id}, then it is applied to any |
| threads that don't have a specific action specified; if no default action is |
| specified then other threads should remain stopped in all-stop mode and |
| in their current state in non-stop mode. |
| Specifying multiple |
| default actions is an error; specifying no actions is also an error. |
| Thread IDs are specified using the syntax described in @ref{thread-id syntax}. |
| |
| Currently supported actions are: |
| |
| @table @samp |
| @item c |
| Continue. |
| @item C @var{sig} |
| Continue with signal @var{sig}. The signal @var{sig} should be two hex digits. |
| @item s |
| Step. |
| @item S @var{sig} |
| Step with signal @var{sig}. The signal @var{sig} should be two hex digits. |
| @item t |
| Stop. |
| @end table |
| |
| The optional argument @var{addr} normally associated with the |
| @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is |
| not supported in @samp{vCont}. |
| |
| The @samp{t} action is only relevant in non-stop mode |
| (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise. |
| A stop reply should be generated for any affected thread not already stopped. |
| When a thread is stopped by means of a @samp{t} action, |
| the corresponding stop reply should indicate that the thread has stopped with |
| signal @samp{0}, regardless of whether the target uses some other signal |
| as an implementation detail. |
| |
| The stub must support @samp{vCont} if it reports support for |
| multiprocess extensions (@pxref{multiprocess extensions}). Note that in |
| this case @samp{vCont} actions can be specified to apply to all threads |
| in a process by using the @samp{p@var{pid}.-1} form of the |
| @var{thread-id}. |
| |
| Reply: |
| @xref{Stop Reply Packets}, for the reply specifications. |
| |
| @item vCont? |
| @cindex @samp{vCont?} packet |
| Request a list of actions supported by the @samp{vCont} packet. |
| |
| Reply: |
| @table @samp |
| @item vCont@r{[};@var{action}@dots{}@r{]} |
| The @samp{vCont} packet is supported. Each @var{action} is a supported |
| command in the @samp{vCont} packet. |
| @item |
| The @samp{vCont} packet is not supported. |
| @end table |
| |
| @item vFile:@var{operation}:@var{parameter}@dots{} |
| @cindex @samp{vFile} packet |
| Perform a file operation on the target system. For details, |
| see @ref{Host I/O Packets}. |
| |
| @item vFlashErase:@var{addr},@var{length} |
| @cindex @samp{vFlashErase} packet |
| Direct the stub to erase @var{length} bytes of flash starting at |
| @var{addr}. The region may enclose any number of flash blocks, but |
| its start and end must fall on block boundaries, as indicated by the |
| flash block size appearing in the memory map (@pxref{Memory Map |
| Format}). @value{GDBN} groups flash memory programming operations |
| together, and sends a @samp{vFlashDone} request after each group; the |
| stub is allowed to delay erase operation until the @samp{vFlashDone} |
| packet is received. |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item vFlashWrite:@var{addr}:@var{XX@dots{}} |
| @cindex @samp{vFlashWrite} packet |
| Direct the stub to write data to flash address @var{addr}. The data |
| is passed in binary form using the same encoding as for the @samp{X} |
| packet (@pxref{Binary Data}). The memory ranges specified by |
| @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must |
| not overlap, and must appear in order of increasing addresses |
| (although @samp{vFlashErase} packets for higher addresses may already |
| have been received; the ordering is guaranteed only between |
| @samp{vFlashWrite} packets). If a packet writes to an address that was |
| neither erased by a preceding @samp{vFlashErase} packet nor by some other |
| target-specific method, the results are unpredictable. |
| |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E.memtype |
| for vFlashWrite addressing non-flash memory |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item vFlashDone |
| @cindex @samp{vFlashDone} packet |
| Indicate to the stub that flash programming operation is finished. |
| The stub is permitted to delay or batch the effects of a group of |
| @samp{vFlashErase} and @samp{vFlashWrite} packets until a |
| @samp{vFlashDone} packet is received. The contents of the affected |
| regions of flash memory are unpredictable until the @samp{vFlashDone} |
| request is completed. |
| |
| @item vKill;@var{pid} |
| @cindex @samp{vKill} packet |
| Kill the process with the specified process ID. @var{pid} is a |
| hexadecimal integer identifying the process. This packet is used in |
| preference to @samp{k} when multiprocess protocol extensions are |
| supported; see @ref{multiprocess extensions}. |
| |
| Reply: |
| @table @samp |
| @item E @var{nn} |
| for an error |
| @item OK |
| for success |
| @end table |
| |
| @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{} |
| @cindex @samp{vRun} packet |
| Run the program @var{filename}, passing it each @var{argument} on its |
| command line. The file and arguments are hex-encoded strings. If |
| @var{filename} is an empty string, the stub may use a default program |
| (e.g.@: the last program run). The program is created in the stopped |
| state. |
| |
| @c FIXME: What about non-stop mode? |
| |
| This packet is only available in extended mode (@pxref{extended mode}). |
| |
| Reply: |
| @table @samp |
| @item E @var{nn} |
| for an error |
| @item @r{Any stop packet} |
| for success (@pxref{Stop Reply Packets}) |
| @end table |
| |
| @item vStopped |
| @anchor{vStopped packet} |
| @cindex @samp{vStopped} packet |
| |
| In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop |
| reply and prompt for the stub to report another one. |
| |
| Reply: |
| @table @samp |
| @item @r{Any stop packet} |
| if there is another unreported stop event (@pxref{Stop Reply Packets}) |
| @item OK |
| if there are no unreported stop events |
| @end table |
| |
| @item X @var{addr},@var{length}:@var{XX@dots{}} |
| @anchor{X packet} |
| @cindex @samp{X} packet |
| Write data to memory, where the data is transmitted in binary. |
| @var{addr} is address, @var{length} is number of bytes, |
| @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}). |
| |
| Reply: |
| @table @samp |
| @item OK |
| for success |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item z @var{type},@var{addr},@var{kind} |
| @itemx Z @var{type},@var{addr},@var{kind} |
| @anchor{insert breakpoint or watchpoint packet} |
| @cindex @samp{z} packet |
| @cindex @samp{Z} packets |
| Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or |
| watchpoint starting at address @var{address} of kind @var{kind}. |
| |
| Each breakpoint and watchpoint packet @var{type} is documented |
| separately. |
| |
| @emph{Implementation notes: A remote target shall return an empty string |
| for an unrecognized breakpoint or watchpoint packet @var{type}. A |
| remote target shall support either both or neither of a given |
| @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To |
| avoid potential problems with duplicate packets, the operations should |
| be implemented in an idempotent way.} |
| |
| @item z0,@var{addr},@var{kind} |
| @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]} |
| @cindex @samp{z0} packet |
| @cindex @samp{Z0} packet |
| Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address |
| @var{addr} of type @var{kind}. |
| |
| A memory breakpoint is implemented by replacing the instruction at |
| @var{addr} with a software breakpoint or trap instruction. The |
| @var{kind} is target-specific and typically indicates the size of |
| the breakpoint in bytes that should be inserted. E.g., the @sc{arm} |
| and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some |
| architectures have additional meanings for @var{kind}; |
| @var{cond_list} is an optional list of conditional expressions in bytecode |
| form that should be evaluated on the target's side. These are the |
| conditions that should be taken into consideration when deciding if |
| the breakpoint trigger should be reported back to @var{GDBN}. |
| |
| The @var{cond_list} parameter is comprised of a series of expressions, |
| concatenated without separators. Each expression has the following form: |
| |
| @table @samp |
| |
| @item X @var{len},@var{expr} |
| @var{len} is the length of the bytecode expression and @var{expr} is the |
| actual conditional expression in bytecode form. |
| |
| @end table |
| |
| The optional @var{cmd_list} parameter introduces commands that may be |
| run on the target, rather than being reported back to @value{GDBN}. |
| The parameter starts with a numeric flag @var{persist}; if the flag is |
| nonzero, then the breakpoint may remain active and the commands |
| continue to be run even when @value{GDBN} disconnects from the target. |
| Following this flag is a series of expressions concatenated with no |
| separators. Each expression has the following form: |
| |
| @table @samp |
| |
| @item X @var{len},@var{expr} |
| @var{len} is the length of the bytecode expression and @var{expr} is the |
| actual conditional expression in bytecode form. |
| |
| @end table |
| |
| see @ref{Architecture-Specific Protocol Details}. |
| |
| @emph{Implementation note: It is possible for a target to copy or move |
| code that contains memory breakpoints (e.g., when implementing |
| overlays). The behavior of this packet, in the presence of such a |
| target, is not defined.} |
| |
| Reply: |
| @table @samp |
| @item OK |
| success |
| @item |
| not supported |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item z1,@var{addr},@var{kind} |
| @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]} |
| @cindex @samp{z1} packet |
| @cindex @samp{Z1} packet |
| Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at |
| address @var{addr}. |
| |
| A hardware breakpoint is implemented using a mechanism that is not |
| dependant on being able to modify the target's memory. @var{kind} |
| and @var{cond_list} have the same meaning as in @samp{Z0} packets. |
| |
| @emph{Implementation note: A hardware breakpoint is not affected by code |
| movement.} |
| |
| Reply: |
| @table @samp |
| @item OK |
| success |
| @item |
| not supported |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item z2,@var{addr},@var{kind} |
| @itemx Z2,@var{addr},@var{kind} |
| @cindex @samp{z2} packet |
| @cindex @samp{Z2} packet |
| Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}. |
| @var{kind} is interpreted as the number of bytes to watch. |
| |
| Reply: |
| @table @samp |
| @item OK |
| success |
| @item |
| not supported |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item z3,@var{addr},@var{kind} |
| @itemx Z3,@var{addr},@var{kind} |
| @cindex @samp{z3} packet |
| @cindex @samp{Z3} packet |
| Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}. |
| @var{kind} is interpreted as the number of bytes to watch. |
| |
| Reply: |
| @table @samp |
| @item OK |
| success |
| @item |
| not supported |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @item z4,@var{addr},@var{kind} |
| @itemx Z4,@var{addr},@var{kind} |
| @cindex @samp{z4} packet |
| @cindex @samp{Z4} packet |
| Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}. |
| @var{kind} is interpreted as the number of bytes to watch. |
| |
| Reply: |
| @table @samp |
| @item OK |
| success |
| @item |
| not supported |
| @item E @var{NN} |
| for an error |
| @end table |
| |
| @end table |
| |
| @node Stop Reply Packets |
| @section Stop Reply Packets |
| @cindex stop reply packets |
| |
| The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont}, |
| @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can |
| receive any of the below as a reply. Except for @samp{?} |
| and @samp{vStopped}, that reply is only returned |
| when the target halts. In the below the exact meaning of @dfn{signal |
| number} is defined by the header @file{include/gdb/signals.h} in the |
| @value{GDBN} source code. |
| |
| As in the description of request packets, we include spaces in the |
| reply templates for clarity; these are not part of the reply packet's |
| syntax. No @value{GDBN} stop reply packet uses spaces to separate its |
| components. |
| |
| @table @samp |
| |
| @item S @var{AA} |
| The program received signal number @var{AA} (a two-digit hexadecimal |
| number). This is equivalent to a @samp{T} response with no |
| @var{n}:@var{r} pairs. |
| |
| @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{} |
| @cindex @samp{T} packet reply |
| The program received signal number @var{AA} (a two-digit hexadecimal |
| number). This is equivalent to an @samp{S} response, except that the |
| @samp{@var{n}:@var{r}} pairs can carry values of important registers |
| and other information directly in the stop reply packet, reducing |
| round-trip latency. Single-step and breakpoint traps are reported |
| this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows: |
| |
| @itemize @bullet |
| @item |
| If @var{n} is a hexadecimal number, it is a register number, and the |
| corresponding @var{r} gives that register's value. @var{r} is a |
| series of bytes in target byte order, with each byte given by a |
| two-digit hex number. |
| |
| @item |
| If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of |
| the stopped thread, as specified in @ref{thread-id syntax}. |
| |
| @item |
| If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of |
| the core on which the stop event was detected. |
| |
| @item |
| If @var{n} is a recognized @dfn{stop reason}, it describes a more |
| specific event that stopped the target. The currently defined stop |
| reasons are listed below. @var{aa} should be @samp{05}, the trap |
| signal. At most one stop reason should be present. |
| |
| @item |
| Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair |
| and go on to the next; this allows us to extend the protocol in the |
| future. |
| @end itemize |
| |
| The currently defined stop reasons are: |
| |
| @table @samp |
| @item watch |
| @itemx rwatch |
| @itemx awatch |
| The packet indicates a watchpoint hit, and @var{r} is the data address, in |
| hex. |
| |
| @cindex shared library events, remote reply |
| @item library |
| The packet indicates that the loaded libraries have changed. |
| @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new |
| list of loaded libraries. @var{r} is ignored. |
| |
| @cindex replay log events, remote reply |
| @item replaylog |
| The packet indicates that the target cannot continue replaying |
| logged execution events, because it has reached the end (or the |
| beginning when executing backward) of the log. The value of @var{r} |
| will be either @samp{begin} or @samp{end}. @xref{Reverse Execution}, |
| for more information. |
| @end table |
| |
| @item W @var{AA} |
| @itemx W @var{AA} ; process:@var{pid} |
| The process exited, and @var{AA} is the exit status. This is only |
| applicable to certain targets. |
| |
| The second form of the response, including the process ID of the exited |
| process, can be used only when @value{GDBN} has reported support for |
| multiprocess protocol extensions; see @ref{multiprocess extensions}. |
| The @var{pid} is formatted as a big-endian hex string. |
| |
| @item X @var{AA} |
| @itemx X @var{AA} ; process:@var{pid} |
| The process terminated with signal @var{AA}. |
| |
| The second form of the response, including the process ID of the |
| terminated process, can be used only when @value{GDBN} has reported |
| support for multiprocess protocol extensions; see @ref{multiprocess |
| extensions}. The @var{pid} is formatted as a big-endian hex string. |
| |
| @item O @var{XX}@dots{} |
| @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be |
| written as the program's console output. This can happen at any time |
| while the program is running and the debugger should continue to wait |
| for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode. |
| |
| @item F @var{call-id},@var{parameter}@dots{} |
| @var{call-id} is the identifier which says which host system call should |
| be called. This is just the name of the function. Translation into the |
| correct system call is only applicable as it's defined in @value{GDBN}. |
| @xref{File-I/O Remote Protocol Extension}, for a list of implemented |
| system calls. |
| |
| @samp{@var{parameter}@dots{}} is a list of parameters as defined for |
| this very system call. |
| |
| The target replies with this packet when it expects @value{GDBN} to |
| call a host system call on behalf of the target. @value{GDBN} replies |
| with an appropriate @samp{F} packet and keeps up waiting for the next |
| reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S} |
| or @samp{s} action is expected to be continued. @xref{File-I/O Remote |
| Protocol Extension}, for more details. |
| |
| @end table |
| |
| @node General Query Packets |
| @section General Query Packets |
| @cindex remote query requests |
| |
| Packets starting with @samp{q} are @dfn{general query packets}; |
| packets starting with @samp{Q} are @dfn{general set packets}. General |
| query and set packets are a semi-unified form for retrieving and |
| sending information to and from the stub. |
| |
| The initial letter of a query or set packet is followed by a name |
| indicating what sort of thing the packet applies to. For example, |
| @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol |
| definitions with the stub. These packet names follow some |
| conventions: |
| |
| @itemize @bullet |
| @item |
| The name must not contain commas, colons or semicolons. |
| @item |
| Most @value{GDBN} query and set packets have a leading upper case |
| letter. |
| @item |
| The names of custom vendor packets should use a company prefix, in |
| lower case, followed by a period. For example, packets designed at |
| the Acme Corporation might begin with @samp{qacme.foo} (for querying |
| foos) or @samp{Qacme.bar} (for setting bars). |
| @end itemize |
| |
| The name of a query or set packet should be separated from any |
| parameters by a @samp{:}; the parameters themselves should be |
| separated by @samp{,} or @samp{;}. Stubs must be careful to match the |
| full packet name, and check for a separator or the end of the packet, |
| in case two packet names share a common prefix. New packets should not begin |
| with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL} |
| packets predate these conventions, and have arguments without any terminator |
| for the packet name; we suspect they are in widespread use in places that |
| are difficult to upgrade. The @samp{qC} packet has no arguments, but some |
| existing stubs (e.g.@: RedBoot) are known to not check for the end of the |
| packet.}. |
| |
| Like the descriptions of the other packets, each description here |
| has a template showing the packet's overall syntax, followed by an |
| explanation of the packet's meaning. We include spaces in some of the |
| templates for clarity; these are not part of the packet's syntax. No |
| @value{GDBN} packet uses spaces to separate its components. |
| |
| Here are the currently defined query and set packets: |
| |
| @table @samp |
| |
| @item QAgent:1 |
| @item QAgent:0 |
| Turn on or off the agent as a helper to perform some debugging operations |
| delegated from @value{GDBN} (@pxref{Control Agent}). |
| |
| @item QAllow:@var{op}:@var{val}@dots{} |
| @cindex @samp{QAllow} packet |
| Specify which operations @value{GDBN} expects to request of the |
| target, as a semicolon-separated list of operation name and value |
| pairs. Possible values for @var{op} include @samp{WriteReg}, |
| @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace}, |
| @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0, |
| indicating that @value{GDBN} will not request the operation, or 1, |
| indicating that it may. (The target can then use this to set up its |
| own internals optimally, for instance if the debugger never expects to |
| insert breakpoints, it may not need to install its own trap handler.) |
| |
| @item qC |
| @cindex current thread, remote request |
| @cindex @samp{qC} packet |
| Return the current thread ID. |
| |
| Reply: |
| @table @samp |
| @item QC @var{thread-id} |
| Where @var{thread-id} is a thread ID as documented in |
| @ref{thread-id syntax}. |
| @item @r{(anything else)} |
| Any other reply implies the old thread ID. |
| @end table |
| |
| @item qCRC:@var{addr},@var{length} |
| @cindex CRC of memory block, remote request |
| @cindex @samp{qCRC} packet |
| Compute the CRC checksum of a block of memory using CRC-32 defined in |
| IEEE 802.3. The CRC is computed byte at a time, taking the most |
| significant bit of each byte first. The initial pattern code |
| @code{0xffffffff} is used to ensure leading zeros affect the CRC. |
| |
| @emph{Note:} This is the same CRC used in validating separate debug |
| files (@pxref{Separate Debug Files, , Debugging Information in Separate |
| Files}). However the algorithm is slightly different. When validating |
| separate debug files, the CRC is computed taking the @emph{least} |
| significant bit of each byte first, and the final result is inverted to |
| detect trailing zeros. |
| |
| Reply: |
| @table @samp |
| @item E @var{NN} |
| An error (such as memory fault) |
| @item C @var{crc32} |
| The specified memory region's checksum is @var{crc32}. |
| @end table |
| |
| @item QDisableRandomization:@var{value} |
| @cindex disable address space randomization, remote request |
| @cindex @samp{QDisableRandomization} packet |
| Some target operating systems will randomize the virtual address space |
| of the inferior process as a security feature, but provide a feature |
| to disable such randomization, e.g.@: to allow for a more deterministic |
| debugging experience. On such systems, this packet with a @var{value} |
| of 1 directs the target to disable address space randomization for |
| processes subsequently started via @samp{vRun} packets, while a packet |
| with a @var{value} of 0 tells the target to enable address space |
| randomization. |
| |
| This packet is only available in extended mode (@pxref{extended mode}). |
| |
| Reply: |
| @table @samp |
| @item OK |
| The request succeeded. |
| |
| @item E @var{nn} |
| An error occurred. @var{nn} are hex digits. |
| |
| @item |
| An empty reply indicates that @samp{QDisableRandomization} is not supported |
| by the stub. |
| @end table |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| This should only be done on targets that actually support disabling |
| address space randomization. |
| |
| @item qfThreadInfo |
| @itemx qsThreadInfo |
| @cindex list active threads, remote request |
| @cindex @samp{qfThreadInfo} packet |
| @cindex @samp{qsThreadInfo} packet |
| Obtain a list of all active thread IDs from the target (OS). Since there |
| may be too many active threads to fit into one reply packet, this query |
| works iteratively: it may require more than one query/reply sequence to |
| obtain the entire list of threads. The first query of the sequence will |
| be the @samp{qfThreadInfo} query; subsequent queries in the |
| sequence will be the @samp{qsThreadInfo} query. |
| |
| NOTE: This packet replaces the @samp{qL} query (see below). |
| |
| Reply: |
| @table @samp |
| @item m @var{thread-id} |
| A single thread ID |
| @item m @var{thread-id},@var{thread-id}@dots{} |
| a comma-separated list of thread IDs |
| @item l |
| (lower case letter @samp{L}) denotes end of list. |
| @end table |
| |
| In response to each query, the target will reply with a list of one or |
| more thread IDs, separated by commas. |
| @value{GDBN} will respond to each reply with a request for more thread |
| ids (using the @samp{qs} form of the query), until the target responds |
| with @samp{l} (lower-case ell, for @dfn{last}). |
| Refer to @ref{thread-id syntax}, for the format of the @var{thread-id} |
| fields. |
| |
| @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm} |
| @cindex get thread-local storage address, remote request |
| @cindex @samp{qGetTLSAddr} packet |
| Fetch the address associated with thread local storage specified |
| by @var{thread-id}, @var{offset}, and @var{lm}. |
| |
| @var{thread-id} is the thread ID associated with the |
| thread for which to fetch the TLS address. @xref{thread-id syntax}. |
| |
| @var{offset} is the (big endian, hex encoded) offset associated with the |
| thread local variable. (This offset is obtained from the debug |
| information associated with the variable.) |
| |
| @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the |
| load module associated with the thread local storage. For example, |
| a @sc{gnu}/Linux system will pass the link map address of the shared |
| object associated with the thread local storage under consideration. |
| Other operating environments may choose to represent the load module |
| differently, so the precise meaning of this parameter will vary. |
| |
| Reply: |
| @table @samp |
| @item @var{XX}@dots{} |
| Hex encoded (big endian) bytes representing the address of the thread |
| local storage requested. |
| |
| @item E @var{nn} |
| An error occurred. @var{nn} are hex digits. |
| |
| @item |
| An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub. |
| @end table |
| |
| @item qGetTIBAddr:@var{thread-id} |
| @cindex get thread information block address |
| @cindex @samp{qGetTIBAddr} packet |
| Fetch address of the Windows OS specific Thread Information Block. |
| |
| @var{thread-id} is the thread ID associated with the thread. |
| |
| Reply: |
| @table @samp |
| @item @var{XX}@dots{} |
| Hex encoded (big endian) bytes representing the linear address of the |
| thread information block. |
| |
| @item E @var{nn} |
| An error occured. This means that either the thread was not found, or the |
| address could not be retrieved. |
| |
| @item |
| An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub. |
| @end table |
| |
| @item qL @var{startflag} @var{threadcount} @var{nextthread} |
| Obtain thread information from RTOS. Where: @var{startflag} (one hex |
| digit) is one to indicate the first query and zero to indicate a |
| subsequent query; @var{threadcount} (two hex digits) is the maximum |
| number of threads the response packet can contain; and @var{nextthread} |
| (eight hex digits), for subsequent queries (@var{startflag} is zero), is |
| returned in the response as @var{argthread}. |
| |
| Don't use this packet; use the @samp{qfThreadInfo} query instead (see above). |
| |
| Reply: |
| @table @samp |
| @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{} |
| Where: @var{count} (two hex digits) is the number of threads being |
| returned; @var{done} (one hex digit) is zero to indicate more threads |
| and one indicates no further threads; @var{argthreadid} (eight hex |
| digits) is @var{nextthread} from the request packet; @var{thread}@dots{} |
| is a sequence of thread IDs from the target. @var{threadid} (eight hex |
| digits). See @code{remote.c:parse_threadlist_response()}. |
| @end table |
| |
| @item qOffsets |
| @cindex section offsets, remote request |
| @cindex @samp{qOffsets} packet |
| Get section offsets that the target used when relocating the downloaded |
| image. |
| |
| Reply: |
| @table @samp |
| @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]} |
| Relocate the @code{Text} section by @var{xxx} from its original address. |
| Relocate the @code{Data} section by @var{yyy} from its original address. |
| If the object file format provides segment information (e.g.@: @sc{elf} |
| @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire |
| segments by the supplied offsets. |
| |
| @emph{Note: while a @code{Bss} offset may be included in the response, |
| @value{GDBN} ignores this and instead applies the @code{Data} offset |
| to the @code{Bss} section.} |
| |
| @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]} |
| Relocate the first segment of the object file, which conventionally |
| contains program code, to a starting address of @var{xxx}. If |
| @samp{DataSeg} is specified, relocate the second segment, which |
| conventionally contains modifiable data, to a starting address of |
| @var{yyy}. @value{GDBN} will report an error if the object file |
| does not contain segment information, or does not contain at least |
| as many segments as mentioned in the reply. Extra segments are |
| kept at fixed offsets relative to the last relocated segment. |
| @end table |
| |
| @item qP @var{mode} @var{thread-id} |
| @cindex thread information, remote request |
| @cindex @samp{qP} packet |
| Returns information on @var{thread-id}. Where: @var{mode} is a hex |
| encoded 32 bit mode; @var{thread-id} is a thread ID |
| (@pxref{thread-id syntax}). |
| |
| Don't use this packet; use the @samp{qThreadExtraInfo} query instead |
| (see below). |
| |
| Reply: see @code{remote.c:remote_unpack_thread_info_response()}. |
| |
| @item QNonStop:1 |
| @item QNonStop:0 |
| @cindex non-stop mode, remote request |
| @cindex @samp{QNonStop} packet |
| @anchor{QNonStop} |
| Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode. |
| @xref{Remote Non-Stop}, for more information. |
| |
| Reply: |
| @table @samp |
| @item OK |
| The request succeeded. |
| |
| @item E @var{nn} |
| An error occurred. @var{nn} are hex digits. |
| |
| @item |
| An empty reply indicates that @samp{QNonStop} is not supported by |
| the stub. |
| @end table |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| Use of this packet is controlled by the @code{set non-stop} command; |
| @pxref{Non-Stop Mode}. |
| |
| @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{} |
| @cindex pass signals to inferior, remote request |
| @cindex @samp{QPassSignals} packet |
| @anchor{QPassSignals} |
| Each listed @var{signal} should be passed directly to the inferior process. |
| Signals are numbered identically to continue packets and stop replies |
| (@pxref{Stop Reply Packets}). Each @var{signal} list item should be |
| strictly greater than the previous item. These signals do not need to stop |
| the inferior, or be reported to @value{GDBN}. All other signals should be |
| reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not |
| combine; any earlier @samp{QPassSignals} list is completely replaced by the |
| new list. This packet improves performance when using @samp{handle |
| @var{signal} nostop noprint pass}. |
| |
| Reply: |
| @table @samp |
| @item OK |
| The request succeeded. |
| |
| @item E @var{nn} |
| An error occurred. @var{nn} are hex digits. |
| |
| @item |
| An empty reply indicates that @samp{QPassSignals} is not supported by |
| the stub. |
| @end table |
| |
| Use of this packet is controlled by the @code{set remote pass-signals} |
| command (@pxref{Remote Configuration, set remote pass-signals}). |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{} |
| @cindex signals the inferior may see, remote request |
| @cindex @samp{QProgramSignals} packet |
| @anchor{QProgramSignals} |
| Each listed @var{signal} may be delivered to the inferior process. |
| Others should be silently discarded. |
| |
| In some cases, the remote stub may need to decide whether to deliver a |
| signal to the program or not without @value{GDBN} involvement. One |
| example of that is while detaching --- the program's threads may have |
| stopped for signals that haven't yet had a chance of being reported to |
| @value{GDBN}, and so the remote stub can use the signal list specified |
| by this packet to know whether to deliver or ignore those pending |
| signals. |
| |
| This does not influence whether to deliver a signal as requested by a |
| resumption packet (@pxref{vCont packet}). |
| |
| Signals are numbered identically to continue packets and stop replies |
| (@pxref{Stop Reply Packets}). Each @var{signal} list item should be |
| strictly greater than the previous item. Multiple |
| @samp{QProgramSignals} packets do not combine; any earlier |
| @samp{QProgramSignals} list is completely replaced by the new list. |
| |
| Reply: |
| @table @samp |
| @item OK |
| The request succeeded. |
| |
| @item E @var{nn} |
| An error occurred. @var{nn} are hex digits. |
| |
| @item |
| An empty reply indicates that @samp{QProgramSignals} is not supported |
| by the stub. |
| @end table |
| |
| Use of this packet is controlled by the @code{set remote program-signals} |
| command (@pxref{Remote Configuration, set remote program-signals}). |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qRcmd,@var{command} |
| @cindex execute remote command, remote request |
| @cindex @samp{qRcmd} packet |
| @var{command} (hex encoded) is passed to the local interpreter for |
| execution. Invalid commands should be reported using the output |
| string. Before the final result packet, the target may also respond |
| with a number of intermediate @samp{O@var{output}} console output |
| packets. @emph{Implementors should note that providing access to a |
| stubs's interpreter may have security implications}. |
| |
| Reply: |
| @table @samp |
| @item OK |
| A command response with no output. |
| @item @var{OUTPUT} |
| A command response with the hex encoded output string @var{OUTPUT}. |
| @item E @var{NN} |
| Indicate a badly formed request. |
| @item |
| An empty reply indicates that @samp{qRcmd} is not recognized. |
| @end table |
| |
| (Note that the @code{qRcmd} packet's name is separated from the |
| command by a @samp{,}, not a @samp{:}, contrary to the naming |
| conventions above. Please don't use this packet as a model for new |
| packets.) |
| |
| @item qSearch:memory:@var{address};@var{length};@var{search-pattern} |
| @cindex searching memory, in remote debugging |
| @cindex @samp{qSearch:memory} packet |
| @anchor{qSearch memory} |
| Search @var{length} bytes at @var{address} for @var{search-pattern}. |
| @var{address} and @var{length} are encoded in hex. |
| @var{search-pattern} is a sequence of bytes, hex encoded. |
| |
| Reply: |
| @table @samp |
| @item 0 |
| The pattern was not found. |
| @item 1,address |
| The pattern was found at @var{address}. |
| @item E @var{NN} |
| A badly formed request or an error was encountered while searching memory. |
| @item |
| An empty reply indicates that @samp{qSearch:memory} is not recognized. |
| @end table |
| |
| @item QStartNoAckMode |
| @cindex @samp{QStartNoAckMode} packet |
| @anchor{QStartNoAckMode} |
| Request that the remote stub disable the normal @samp{+}/@samp{-} |
| protocol acknowledgments (@pxref{Packet Acknowledgment}). |
| |
| Reply: |
| @table @samp |
| @item OK |
| The stub has switched to no-acknowledgment mode. |
| @value{GDBN} acknowledges this reponse, |
| but neither the stub nor @value{GDBN} shall send or expect further |
| @samp{+}/@samp{-} acknowledgments in the current connection. |
| @item |
| An empty reply indicates that the stub does not support no-acknowledgment mode. |
| @end table |
| |
| @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]} |
| @cindex supported packets, remote query |
| @cindex features of the remote protocol |
| @cindex @samp{qSupported} packet |
| @anchor{qSupported} |
| Tell the remote stub about features supported by @value{GDBN}, and |
| query the stub for features it supports. This packet allows |
| @value{GDBN} and the remote stub to take advantage of each others' |
| features. @samp{qSupported} also consolidates multiple feature probes |
| at startup, to improve @value{GDBN} performance---a single larger |
| packet performs better than multiple smaller probe packets on |
| high-latency links. Some features may enable behavior which must not |
| be on by default, e.g.@: because it would confuse older clients or |
| stubs. Other features may describe packets which could be |
| automatically probed for, but are not. These features must be |
| reported before @value{GDBN} will use them. This ``default |
| unsupported'' behavior is not appropriate for all packets, but it |
| helps to keep the initial connection time under control with new |
| versions of @value{GDBN} which support increasing numbers of packets. |
| |
| Reply: |
| @table @samp |
| @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{} |
| The stub supports or does not support each returned @var{stubfeature}, |
| depending on the form of each @var{stubfeature} (see below for the |
| possible forms). |
| @item |
| An empty reply indicates that @samp{qSupported} is not recognized, |
| or that no features needed to be reported to @value{GDBN}. |
| @end table |
| |
| The allowed forms for each feature (either a @var{gdbfeature} in the |
| @samp{qSupported} packet, or a @var{stubfeature} in the response) |
| are: |
| |
| @table @samp |
| @item @var{name}=@var{value} |
| The remote protocol feature @var{name} is supported, and associated |
| with the specified @var{value}. The format of @var{value} depends |
| on the feature, but it must not include a semicolon. |
| @item @var{name}+ |
| The remote protocol feature @var{name} is supported, and does not |
| need an associated value. |
| @item @var{name}- |
| The remote protocol feature @var{name} is not supported. |
| @item @var{name}? |
| The remote protocol feature @var{name} may be supported, and |
| @value{GDBN} should auto-detect support in some other way when it is |
| needed. This form will not be used for @var{gdbfeature} notifications, |
| but may be used for @var{stubfeature} responses. |
| @end table |
| |
| Whenever the stub receives a @samp{qSupported} request, the |
| supplied set of @value{GDBN} features should override any previous |
| request. This allows @value{GDBN} to put the stub in a known |
| state, even if the stub had previously been communicating with |
| a different version of @value{GDBN}. |
| |
| The following values of @var{gdbfeature} (for the packet sent by @value{GDBN}) |
| are defined: |
| |
| @table @samp |
| @item multiprocess |
| This feature indicates whether @value{GDBN} supports multiprocess |
| extensions to the remote protocol. @value{GDBN} does not use such |
| extensions unless the stub also reports that it supports them by |
| including @samp{multiprocess+} in its @samp{qSupported} reply. |
| @xref{multiprocess extensions}, for details. |
| |
| @item xmlRegisters |
| This feature indicates that @value{GDBN} supports the XML target |
| description. If the stub sees @samp{xmlRegisters=} with target |
| specific strings separated by a comma, it will report register |
| description. |
| |
| @item qRelocInsn |
| This feature indicates whether @value{GDBN} supports the |
| @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate |
| instruction reply packet}). |
| @end table |
| |
| Stubs should ignore any unknown values for |
| @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported} |
| packet supports receiving packets of unlimited length (earlier |
| versions of @value{GDBN} may reject overly long responses). Additional values |
| for @var{gdbfeature} may be defined in the future to let the stub take |
| advantage of new features in @value{GDBN}, e.g.@: incompatible |
| improvements in the remote protocol---the @samp{multiprocess} feature is |
| an example of such a feature. The stub's reply should be independent |
| of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN} |
| describes all the features it supports, and then the stub replies with |
| all the features it supports. |
| |
| Similarly, @value{GDBN} will silently ignore unrecognized stub feature |
| responses, as long as each response uses one of the standard forms. |
| |
| Some features are flags. A stub which supports a flag feature |
| should respond with a @samp{+} form response. Other features |
| require values, and the stub should respond with an @samp{=} |
| form response. |
| |
| Each feature has a default value, which @value{GDBN} will use if |
| @samp{qSupported} is not available or if the feature is not mentioned |
| in the @samp{qSupported} response. The default values are fixed; a |
| stub is free to omit any feature responses that match the defaults. |
| |
| Not all features can be probed, but for those which can, the probing |
| mechanism is useful: in some cases, a stub's internal |
| architecture may not allow the protocol layer to know some information |
| about the underlying target in advance. This is especially common in |
| stubs which may be configured for multiple targets. |
| |
| These are the currently defined stub features and their properties: |
| |
| @multitable @columnfractions 0.35 0.2 0.12 0.2 |
| @c NOTE: The first row should be @headitem, but we do not yet require |
| @c a new enough version of Texinfo (4.7) to use @headitem. |
| @item Feature Name |
| @tab Value Required |
| @tab Default |
| @tab Probe Allowed |
| |
| @item @samp{PacketSize} |
| @tab Yes |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{qXfer:auxv:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:features:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:libraries:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:memory-map:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:sdata:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:spu:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:spu:write} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:siginfo:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:siginfo:write} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:threads:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:traceframe-info:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:uib:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{qXfer:fdpic:read} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{QNonStop} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{QPassSignals} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{QStartNoAckMode} |
| @tab No |
| @tab @samp{-} |
| @tab Yes |
| |
| @item @samp{multiprocess} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{ConditionalBreakpoints} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{ConditionalTracepoints} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{ReverseContinue} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{ReverseStep} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{TracepointSource} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{QAgent} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{QAllow} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{QDisableRandomization} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{EnableDisableTracepoints} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{tracenz} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @item @samp{BreakpointCommands} |
| @tab No |
| @tab @samp{-} |
| @tab No |
| |
| @end multitable |
| |
| These are the currently defined stub features, in more detail: |
| |
| @table @samp |
| @cindex packet size, remote protocol |
| @item PacketSize=@var{bytes} |
| The remote stub can accept packets up to at least @var{bytes} in |
| length. @value{GDBN} will send packets up to this size for bulk |
| transfers, and will never send larger packets. This is a limit on the |
| data characters in the packet, including the frame and checksum. |
| There is no trailing NUL byte in a remote protocol packet; if the stub |
| stores packets in a NUL-terminated format, it should allow an extra |
| byte in its buffer for the NUL. If this stub feature is not supported, |
| @value{GDBN} guesses based on the size of the @samp{g} packet response. |
| |
| @item qXfer:auxv:read |
| The remote stub understands the @samp{qXfer:auxv:read} packet |
| (@pxref{qXfer auxiliary vector read}). |
| |
| @item qXfer:features:read |
| The remote stub understands the @samp{qXfer:features:read} packet |
| (@pxref{qXfer target description read}). |
| |
| @item qXfer:libraries:read |
| The remote stub understands the @samp{qXfer:libraries:read} packet |
| (@pxref{qXfer library list read}). |
| |
| @item qXfer:libraries-svr4:read |
| The remote stub understands the @samp{qXfer:libraries-svr4:read} packet |
| (@pxref{qXfer svr4 library list read}). |
| |
| @item qXfer:memory-map:read |
| The remote stub understands the @samp{qXfer:memory-map:read} packet |
| (@pxref{qXfer memory map read}). |
| |
| @item qXfer:sdata:read |
| The remote stub understands the @samp{qXfer:sdata:read} packet |
| (@pxref{qXfer sdata read}). |
| |
| @item qXfer:spu:read |
| The remote stub understands the @samp{qXfer:spu:read} packet |
| (@pxref{qXfer spu read}). |
| |
| @item qXfer:spu:write |
| The remote stub understands the @samp{qXfer:spu:write} packet |
| (@pxref{qXfer spu write}). |
| |
| @item qXfer:siginfo:read |
| The remote stub understands the @samp{qXfer:siginfo:read} packet |
| (@pxref{qXfer siginfo read}). |
| |
| @item qXfer:siginfo:write |
| The remote stub understands the @samp{qXfer:siginfo:write} packet |
| (@pxref{qXfer siginfo write}). |
| |
| @item qXfer:threads:read |
| The remote stub understands the @samp{qXfer:threads:read} packet |
| (@pxref{qXfer threads read}). |
| |
| @item qXfer:traceframe-info:read |
| The remote stub understands the @samp{qXfer:traceframe-info:read} |
| packet (@pxref{qXfer traceframe info read}). |
| |
| @item qXfer:uib:read |
| The remote stub understands the @samp{qXfer:uib:read} |
| packet (@pxref{qXfer unwind info block}). |
| |
| @item qXfer:fdpic:read |
| The remote stub understands the @samp{qXfer:fdpic:read} |
| packet (@pxref{qXfer fdpic loadmap read}). |
| |
| @item QNonStop |
| The remote stub understands the @samp{QNonStop} packet |
| (@pxref{QNonStop}). |
| |
| @item QPassSignals |
| The remote stub understands the @samp{QPassSignals} packet |
| (@pxref{QPassSignals}). |
| |
| @item QStartNoAckMode |
| The remote stub understands the @samp{QStartNoAckMode} packet and |
| prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}. |
| |
| @item multiprocess |
| @anchor{multiprocess extensions} |
| @cindex multiprocess extensions, in remote protocol |
| The remote stub understands the multiprocess extensions to the remote |
| protocol syntax. The multiprocess extensions affect the syntax of |
| thread IDs in both packets and replies (@pxref{thread-id syntax}), and |
| add process IDs to the @samp{D} packet and @samp{W} and @samp{X} |
| replies. Note that reporting this feature indicates support for the |
| syntactic extensions only, not that the stub necessarily supports |
| debugging of more than one process at a time. The stub must not use |
| multiprocess extensions in packet replies unless @value{GDBN} has also |
| indicated it supports them in its @samp{qSupported} request. |
| |
| @item qXfer:osdata:read |
| The remote stub understands the @samp{qXfer:osdata:read} packet |
| ((@pxref{qXfer osdata read}). |
| |
| @item ConditionalBreakpoints |
| The target accepts and implements evaluation of conditional expressions |
| defined for breakpoints. The target will only report breakpoint triggers |
| when such conditions are true (@pxref{Conditions, ,Break Conditions}). |
| |
| @item ConditionalTracepoints |
| The remote stub accepts and implements conditional expressions defined |
| for tracepoints (@pxref{Tracepoint Conditions}). |
| |
| @item ReverseContinue |
| The remote stub accepts and implements the reverse continue packet |
| (@pxref{bc}). |
| |
| @item ReverseStep |
| The remote stub accepts and implements the reverse step packet |
| (@pxref{bs}). |
| |
| @item TracepointSource |
| The remote stub understands the @samp{QTDPsrc} packet that supplies |
| the source form of tracepoint definitions. |
| |
| @item QAgent |
| The remote stub understands the @samp{QAgent} packet. |
| |
| @item QAllow |
| The remote stub understands the @samp{QAllow} packet. |
| |
| @item QDisableRandomization |
| The remote stub understands the @samp{QDisableRandomization} packet. |
| |
| @item StaticTracepoint |
| @cindex static tracepoints, in remote protocol |
| The remote stub supports static tracepoints. |
| |
| @item InstallInTrace |
| @anchor{install tracepoint in tracing} |
| The remote stub supports installing tracepoint in tracing. |
| |
| @item EnableDisableTracepoints |
| The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and |
| @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints |
| to be enabled and disabled while a trace experiment is running. |
| |
| @item tracenz |
| @cindex string tracing, in remote protocol |
| The remote stub supports the @samp{tracenz} bytecode for collecting strings. |
| See @ref{Bytecode Descriptions} for details about the bytecode. |
| |
| @item BreakpointCommands |
| @cindex breakpoint commands, in remote protocol |
| The remote stub supports running a breakpoint's command list itself, |
| rather than reporting the hit to @value{GDBN}. |
| |
| @end table |
| |
| @item qSymbol:: |
| @cindex symbol lookup, remote request |
| @cindex @samp{qSymbol} packet |
| Notify the target that @value{GDBN} is prepared to serve symbol lookup |
| requests. Accept requests from the target for the values of symbols. |
| |
| Reply: |
| @table @samp |
| @item OK |
| The target does not need to look up any (more) symbols. |
| @item qSymbol:@var{sym_name} |
| The target requests the value of symbol @var{sym_name} (hex encoded). |
| @value{GDBN} may provide the value by using the |
| @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described |
| below. |
| @end table |
| |
| @item qSymbol:@var{sym_value}:@var{sym_name} |
| Set the value of @var{sym_name} to @var{sym_value}. |
| |
| @var{sym_name} (hex encoded) is the name of a symbol whose value the |
| target has previously requested. |
| |
| @var{sym_value} (hex) is the value for symbol @var{sym_name}. If |
| @value{GDBN} cannot supply a value for @var{sym_name}, then this field |
| will be empty. |
| |
| Reply: |
| @table @samp |
| @item OK |
| The target does not need to look up any (more) symbols. |
| @item qSymbol:@var{sym_name} |
| The target requests the value of a new symbol @var{sym_name} (hex |
| encoded). @value{GDBN} will continue to supply the values of symbols |
| (if available), until the target ceases to request them. |
| @end table |
| |
| @item qTBuffer |
| @item QTBuffer |
| @item QTDisconnected |
| @itemx QTDP |
| @itemx QTDPsrc |
| @itemx QTDV |
| @itemx qTfP |
| @itemx qTfV |
| @itemx QTFrame |
| @itemx qTMinFTPILen |
| |
| @xref{Tracepoint Packets}. |
| |
| @item qThreadExtraInfo,@var{thread-id} |
| @cindex thread attributes info, remote request |
| @cindex @samp{qThreadExtraInfo} packet |
| Obtain a printable string description of a thread's attributes from |
| the target OS. @var{thread-id} is a thread ID; |
| see @ref{thread-id syntax}. This |
| string may contain anything that the target OS thinks is interesting |
| for @value{GDBN} to tell the user about the thread. The string is |
| displayed in @value{GDBN}'s @code{info threads} display. Some |
| examples of possible thread extra info strings are @samp{Runnable}, or |
| @samp{Blocked on Mutex}. |
| |
| Reply: |
| @table @samp |
| @item @var{XX}@dots{} |
| Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data, |
| comprising the printable string containing the extra information about |
| the thread's attributes. |
| @end table |
| |
| (Note that the @code{qThreadExtraInfo} packet's name is separated from |
| the command by a @samp{,}, not a @samp{:}, contrary to the naming |
| conventions above. Please don't use this packet as a model for new |
| packets.) |
| |
| @item QTNotes |
| @item qTP |
| @item QTSave |
| @item qTsP |
| @item qTsV |
| @itemx QTStart |
| @itemx QTStop |
| @itemx QTEnable |
| @itemx QTDisable |
| @itemx QTinit |
| @itemx QTro |
| @itemx qTStatus |
| @itemx qTV |
| @itemx qTfSTM |
| @itemx qTsSTM |
| @itemx qTSTMat |
| @xref{Tracepoint Packets}. |
| |
| @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length} |
| @cindex read special object, remote request |
| @cindex @samp{qXfer} packet |
| @anchor{qXfer read} |
| Read uninterpreted bytes from the target's special data area |
| identified by the keyword @var{object}. Request @var{length} bytes |
| starting at @var{offset} bytes into the data. The content and |
| encoding of @var{annex} is specific to @var{object}; it can supply |
| additional details about what data to access. |
| |
| Here are the specific requests of this form defined so far. All |
| @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply |
| formats, listed below. |
| |
| @table @samp |
| @item qXfer:auxv:read::@var{offset},@var{length} |
| @anchor{qXfer auxiliary vector read} |
| Access the target's @dfn{auxiliary vector}. @xref{OS Information, |
| auxiliary vector}. Note @var{annex} must be empty. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:features:read:@var{annex}:@var{offset},@var{length} |
| @anchor{qXfer target description read} |
| Access the @dfn{target description}. @xref{Target Descriptions}. The |
| annex specifies which XML document to access. The main description is |
| always loaded from the @samp{target.xml} annex. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length} |
| @anchor{qXfer library list read} |
| Access the target's list of loaded libraries. @xref{Library List Format}. |
| The annex part of the generic @samp{qXfer} packet must be empty |
| (@pxref{qXfer read}). |
| |
| Targets which maintain a list of libraries in the program's memory do |
| not need to implement this packet; it is designed for platforms where |
| the operating system manages the list of loaded libraries. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length} |
| @anchor{qXfer svr4 library list read} |
| Access the target's list of loaded libraries when the target is an SVR4 |
| platform. @xref{Library List Format for SVR4 Targets}. The annex part |
| of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}). |
| |
| This packet is optional for better performance on SVR4 targets. |
| @value{GDBN} uses memory read packets to read the SVR4 library list otherwise. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:memory-map:read::@var{offset},@var{length} |
| @anchor{qXfer memory map read} |
| Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The |
| annex part of the generic @samp{qXfer} packet must be empty |
| (@pxref{qXfer read}). |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:sdata:read::@var{offset},@var{length} |
| @anchor{qXfer sdata read} |
| |
| Read contents of the extra collected static tracepoint marker |
| information. The annex part of the generic @samp{qXfer} packet must |
| be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint |
| Action Lists}. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response |
| (@pxref{qSupported}). |
| |
| @item qXfer:siginfo:read::@var{offset},@var{length} |
| @anchor{qXfer siginfo read} |
| Read contents of the extra signal information on the target |
| system. The annex part of the generic @samp{qXfer} packet must be |
| empty (@pxref{qXfer read}). |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response |
| (@pxref{qSupported}). |
| |
| @item qXfer:spu:read:@var{annex}:@var{offset},@var{length} |
| @anchor{qXfer spu read} |
| Read contents of an @code{spufs} file on the target system. The |
| annex specifies which file to read; it must be of the form |
| @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID |
| in the target process, and @var{name} identifes the @code{spufs} file |
| in that context to be accessed. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response |
| (@pxref{qSupported}). |
| |
| @item qXfer:threads:read::@var{offset},@var{length} |
| @anchor{qXfer threads read} |
| Access the list of threads on target. @xref{Thread List Format}. The |
| annex part of the generic @samp{qXfer} packet must be empty |
| (@pxref{qXfer read}). |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:traceframe-info:read::@var{offset},@var{length} |
| @anchor{qXfer traceframe info read} |
| |
| Return a description of the current traceframe's contents. |
| @xref{Traceframe Info Format}. The annex part of the generic |
| @samp{qXfer} packet must be empty (@pxref{qXfer read}). |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:uib:read:@var{pc}:@var{offset},@var{length} |
| @anchor{qXfer unwind info block} |
| |
| Return the unwind information block for @var{pc}. This packet is used |
| on OpenVMS/ia64 to ask the kernel unwind information. |
| |
| This packet is not probed by default. |
| |
| @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length} |
| @anchor{qXfer fdpic loadmap read} |
| Read contents of @code{loadmap}s on the target system. The |
| annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap}, |
| executable @code{loadmap} or interpreter @code{loadmap} to read. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| |
| @item qXfer:osdata:read::@var{offset},@var{length} |
| @anchor{qXfer osdata read} |
| Access the target's @dfn{operating system information}. |
| @xref{Operating System Information}. |
| |
| @end table |
| |
| Reply: |
| @table @samp |
| @item m @var{data} |
| Data @var{data} (@pxref{Binary Data}) has been read from the |
| target. There may be more data at a higher address (although |
| it is permitted to return @samp{m} even for the last valid |
| block of data, as long as at least one byte of data was read). |
| @var{data} may have fewer bytes than the @var{length} in the |
| request. |
| |
| @item l @var{data} |
| Data @var{data} (@pxref{Binary Data}) has been read from the target. |
| There is no more data to be read. @var{data} may have fewer bytes |
| than the @var{length} in the request. |
| |
| @item l |
| The @var{offset} in the request is at the end of the data. |
| There is no more data to be read. |
| |
| @item E00 |
| The request was malformed, or @var{annex} was invalid. |
| |
| @item E @var{nn} |
| The offset was invalid, or there was an error encountered reading the data. |
| @var{nn} is a hex-encoded @code{errno} value. |
| |
| @item |
| An empty reply indicates the @var{object} string was not recognized by |
| the stub, or that the object does not support reading. |
| @end table |
| |
| @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{} |
| @cindex write data into object, remote request |
| @anchor{qXfer write} |
| Write uninterpreted bytes into the target's special data area |
| identified by the keyword @var{object}, starting at @var{offset} bytes |
| into the data. @var{data}@dots{} is the binary-encoded data |
| (@pxref{Binary Data}) to be written. The content and encoding of @var{annex} |
| is specific to @var{object}; it can supply additional details about what data |
| to access. |
| |
| Here are the specific requests of this form defined so far. All |
| @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply |
| formats, listed below. |
| |
| @table @samp |
| @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{} |
| @anchor{qXfer siginfo write} |
| Write @var{data} to the extra signal information on the target system. |
| The annex part of the generic @samp{qXfer} packet must be |
| empty (@pxref{qXfer write}). |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response |
| (@pxref{qSupported}). |
| |
| @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{} |
| @anchor{qXfer spu write} |
| Write @var{data} to an @code{spufs} file on the target system. The |
| annex specifies which file to write; it must be of the form |
| @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID |
| in the target process, and @var{name} identifes the @code{spufs} file |
| in that context to be accessed. |
| |
| This packet is not probed by default; the remote stub must request it, |
| by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}). |
| @end table |
| |
| Reply: |
| @table @samp |
| @item @var{nn} |
| @var{nn} (hex encoded) is the number of bytes written. |
| This may be fewer bytes than supplied in the request. |
| |
| @item E00 |
| The request was malformed, or @var{annex} was invalid. |
| |
| @item E @var{nn} |
| The offset was invalid, or there was an error encountered writing the data. |
| @var{nn} is a hex-encoded @code{errno} value. |
| |
| @item |
| An empty reply indicates the @var{object} string was not |
| recognized by the stub, or that the object does not support writing. |
| @end table |
| |
| @item qXfer:@var{object}:@var{operation}:@dots{} |
| Requests of this form may be added in the future. When a stub does |
| not recognize the @var{object} keyword, or its support for |
| @var{object} does not recognize the @var{operation} keyword, the stub |
| must respond with an empty packet. |
| |
| @item qAttached:@var{pid} |
| @cindex query attached, remote request |
| @cindex @samp{qAttached} packet |
| Return an indication of whether the remote server attached to an |
| existing process or created a new process. When the multiprocess |
| protocol extensions are supported (@pxref{multiprocess extensions}), |
| @var{pid} is an integer in hexadecimal format identifying the target |
| process. Otherwise, @value{GDBN} will omit the @var{pid} field and |
| the query packet will be simplified as @samp{qAttached}. |
| |
| This query is used, for example, to know whether the remote process |
| should be detached or killed when a @value{GDBN} session is ended with |
| the @code{quit} command. |
| |
| Reply: |
| @table @samp |
| @item 1 |
| The remote server attached to an existing process. |
| @item 0 |
| The remote server created a new process. |
| @item E @var{NN} |
| A badly formed request or an error was encountered. |
| @end table |
| |
| @end table |
| |
| @node Architecture-Specific Protocol Details |
| @section Architecture-Specific Protocol Details |
| |
| This section describes how the remote protocol is applied to specific |
| target architectures. Also see @ref{Standard Target Features}, for |
| details of XML target descriptions for each architecture. |
| |
| @menu |
| * ARM-Specific Protocol Details:: |
| * MIPS-Specific Protocol Details:: |
| @end menu |
| |
| @node ARM-Specific Protocol Details |
| @subsection @acronym{ARM}-specific Protocol Details |
| |
| @menu |
| * ARM Breakpoint Kinds:: |
| @end menu |
| |
| @node ARM Breakpoint Kinds |
| @subsubsection @acronym{ARM} Breakpoint Kinds |
| @cindex breakpoint kinds, @acronym{ARM} |
| |
| These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets. |
| |
| @table @r |
| |
| @item 2 |
| 16-bit Thumb mode breakpoint. |
| |
| @item 3 |
| 32-bit Thumb mode (Thumb-2) breakpoint. |
| |
| @item 4 |
| 32-bit @acronym{ARM} mode breakpoint. |
| |
| @end table |
| |
| @node MIPS-Specific Protocol Details |
| @subsection @acronym{MIPS}-specific Protocol Details |
| |
| @menu |
| * MIPS Register packet Format:: |
| * MIPS Breakpoint Kinds:: |
| @end menu |
| |
| @node MIPS Register packet Format |
| @subsubsection @acronym{MIPS} Register Packet Format |
| @cindex register packet format, @acronym{MIPS} |
| |
| The following @code{g}/@code{G} packets have previously been defined. |
| In the below, some thirty-two bit registers are transferred as |
| sixty-four bits. Those registers should be zero/sign extended (which?) |
| to fill the space allocated. Register bytes are transferred in target |
| byte order. The two nibbles within a register byte are transferred |
| most-significant -- least-significant. |
| |
| @table @r |
| |
| @item MIPS32 |
| All registers are transferred as thirty-two bit quantities in the order: |
| 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point |
| registers; fsr; fir; fp. |
| |
| @item MIPS64 |
| All registers are transferred as sixty-four bit quantities (including |
| thirty-two bit registers such as @code{sr}). The ordering is the same |
| as @code{MIPS32}. |
| |
| @end table |
| |
| @node MIPS Breakpoint Kinds |
| @subsubsection @acronym{MIPS} Breakpoint Kinds |
| @cindex breakpoint kinds, @acronym{MIPS} |
| |
| These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets. |
| |
| @table @r |
| |
| @item 2 |
| 16-bit @acronym{MIPS16} mode breakpoint. |
| |
| @item 3 |
| 16-bit @acronym{microMIPS} mode breakpoint. |
| |
| @item 4 |
| 32-bit standard @acronym{MIPS} mode breakpoint. |
| |
| @item 5 |
| 32-bit @acronym{microMIPS} mode breakpoint. |
| |
| @end table |
| |
| @node Tracepoint Packets |
| @section Tracepoint Packets |
| @cindex tracepoint packets |
| @cindex packets, tracepoint |
| |
| Here we describe the packets @value{GDBN} uses to implement |
| tracepoints (@pxref{Tracepoints}). |
| |
| @table @samp |
| |
| @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]} |
| @cindex @samp{QTDP} packet |
| Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena} |
| is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then |
| the tracepoint is disabled. @var{step} is the tracepoint's step |
| count, and @var{pass} is its pass count. If an @samp{F} is present, |
| then the tracepoint is to be a fast tracepoint, and the @var{flen} is |
| the number of bytes that the target should copy elsewhere to make room |
| for the tracepoint. If an @samp{X} is present, it introduces a |
| tracepoint condition, which consists of a hexadecimal length, followed |
| by a comma and hex-encoded bytes, in a manner similar to action |
| encodings as described below. If the trailing @samp{-} is present, |
| further @samp{QTDP} packets will follow to specify this tracepoint's |
| actions. |
| |
| Replies: |
| @table @samp |
| @item OK |
| The packet was understood and carried out. |
| @item qRelocInsn |
| @xref{Tracepoint Packets,,Relocate instruction reply packet}. |
| @item |
| The packet was not recognized. |
| @end table |
| |
| @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]} |
| Define actions to be taken when a tracepoint is hit. @var{n} and |
| @var{addr} must be the same as in the initial @samp{QTDP} packet for |
| this tracepoint. This packet may only be sent immediately after |
| another @samp{QTDP} packet that ended with a @samp{-}. If the |
| trailing @samp{-} is present, further @samp{QTDP} packets will follow, |
| specifying more actions for this tracepoint. |
| |
| In the series of action packets for a given tracepoint, at most one |
| can have an @samp{S} before its first @var{action}. If such a packet |
| is sent, it and the following packets define ``while-stepping'' |
| actions. Any prior packets define ordinary actions --- that is, those |
| taken when the tracepoint is first hit. If no action packet has an |
| @samp{S}, then all the packets in the series specify ordinary |
| tracepoint actions. |
| |
| The @samp{@var{action}@dots{}} portion of the packet is a series of |
| actions, concatenated without separators. Each action has one of the |
| following forms: |
| |
| @table @samp |
| |
| @item R @var{mask} |
| Collect the registers whose bits are set in @var{mask}. @var{mask} is |
| a hexadecimal number whose @var{i}'th bit is set if register number |
| @var{i} should be collected. (The least significant bit is numbered |
| zero.) Note that @var{mask} may be any number of digits long; it may |
| not fit in a 32-bit word. |
| |
| @item M @var{basereg},@var{offset},@var{len} |
| Collect @var{len} bytes of memory starting at the address in register |
| number @var{basereg}, plus @var{offset}. If @var{basereg} is |
| @samp{-1}, then the range has a fixed address: @var{offset} is the |
| address of the lowest byte to collect. The @var{basereg}, |
| @var{offset}, and @var{len} parameters are all unsigned hexadecimal |
| values (the @samp{-1} value for @var{basereg} is a special case). |
| |
| @item X @var{len},@var{expr} |
| Evaluate @var{expr}, whose length is @var{len}, and collect memory as |
| it directs. @var{expr} is an agent expression, as described in |
| @ref{Agent Expressions}. Each byte of the expression is encoded as a |
| two-digit hex number in the packet; @var{len} is the number of bytes |
| in the expression (and thus one-half the number of hex digits in the |
| packet). |
| |
| @end table |
| |
| Any number of actions may be packed together in a single @samp{QTDP} |
| packet, as long as the packet does not exceed the maximum packet |
| length (400 bytes, for many stubs). There may be only one @samp{R} |
| action per tracepoint, and it must precede any @samp{M} or @samp{X} |
| actions. Any registers referred to by @samp{M} and @samp{X} actions |
| must be collected by a preceding @samp{R} action. (The |
| ``while-stepping'' actions are treated as if they were attached to a |
| separate tracepoint, as far as these restrictions are concerned.) |
| |
| Replies: |
| @table @samp |
| @item OK |
| The packet was understood and carried out. |
| @item qRelocInsn |
| @xref{Tracepoint Packets,,Relocate instruction reply packet}. |
| @item |
| The packet was not recognized. |
| @end table |
| |
| @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes} |
| @cindex @samp{QTDPsrc} packet |
| Specify a source string of tracepoint @var{n} at address @var{addr}. |
| This is useful to get accurate reproduction of the tracepoints |
| originally downloaded at the beginning of the trace run. @var{type} |
| is the name of the tracepoint part, such as @samp{cond} for the |
| tracepoint's conditional expression (see below for a list of types), while |
| @var{bytes} is the string, encoded in hexadecimal. |
| |
| @var{start} is the offset of the @var{bytes} within the overall source |
| string, while @var{slen} is the total length of the source string. |
| This is intended for handling source strings that are longer than will |
| fit in a single packet. |
| @c Add detailed example when this info is moved into a dedicated |
| @c tracepoint descriptions section. |
| |
| The available string types are @samp{at} for the location, |
| @samp{cond} for the conditional, and @samp{cmd} for an action command. |
| @value{GDBN} sends a separate packet for each command in the action |
| list, in the same order in which the commands are stored in the list. |
| |
| The target does not need to do anything with source strings except |
| report them back as part of the replies to the @samp{qTfP}/@samp{qTsP} |
| query packets. |
| |
| Although this packet is optional, and @value{GDBN} will only send it |
| if the target replies with @samp{TracepointSource} @xref{General |
| Query Packets}, it makes both disconnected tracing and trace files |
| much easier to use. Otherwise the user must be careful that the |
| tracepoints in effect while looking at trace frames are identical to |
| the ones in effect during the trace run; even a small discrepancy |
| could cause @samp{tdump} not to work, or a particular trace frame not |
| be found. |
| |
| @item QTDV:@var{n}:@var{value} |
| @cindex define trace state variable, remote request |
| @cindex @samp{QTDV} packet |
| Create a new trace state variable, number @var{n}, with an initial |
| value of @var{value}, which is a 64-bit signed integer. Both @var{n} |
| and @var{value} are encoded as hexadecimal values. @value{GDBN} has |
| the option of not using this packet for initial values of zero; the |
| target should simply create the trace state variables as they are |
| mentioned in expressions. |
| |
| @item QTFrame:@var{n} |
| @cindex @samp{QTFrame} packet |
| Select the @var{n}'th tracepoint frame from the buffer, and use the |
| register and memory contents recorded there to answer subsequent |
| request packets from @value{GDBN}. |
| |
| A successful reply from the stub indicates that the stub has found the |
| requested frame. The response is a series of parts, concatenated |
| without separators, describing the frame we selected. Each part has |
| one of the following forms: |
| |
| @table @samp |
| @item F @var{f} |
| The selected frame is number @var{n} in the trace frame buffer; |
| @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there |
| was no frame matching the criteria in the request packet. |
| |
| @item T @var{t} |
| The selected trace frame records a hit of tracepoint number @var{t}; |
| @var{t} is a hexadecimal number. |
| |
| @end table |
| |
| @item QTFrame:pc:@var{addr} |
| Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the |
| currently selected frame whose PC is @var{addr}; |
| @var{addr} is a hexadecimal number. |
| |
| @item QTFrame:tdp:@var{t} |
| Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the |
| currently selected frame that is a hit of tracepoint @var{t}; @var{t} |
| is a hexadecimal number. |
| |
| @item QTFrame:range:@var{start}:@var{end} |
| Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the |
| currently selected frame whose PC is between @var{start} (inclusive) |
| and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal |
| numbers. |
| |
| @item QTFrame:outside:@var{start}:@var{end} |
| Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first |
| frame @emph{outside} the given range of addresses (exclusive). |
| |
| @item qTMinFTPILen |
| @cindex @samp{qTMinFTPILen} packet |
| This packet requests the minimum length of instruction at which a fast |
| tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on |
| the 32-bit x86 architecture, it is possible to use a 4-byte jump, but |
| it depends on the target system being able to create trampolines in |
| the first 64K of memory, which might or might not be possible for that |
| system. So the reply to this packet will be 4 if it is able to |
| arrange for that. |
| |
| Replies: |
| |
| @table @samp |
| @item 0 |
| The minimum instruction length is currently unknown. |
| @item @var{length} |
| The minimum instruction length is @var{length}, where @var{length} is greater |
| or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means |
| that a fast tracepoint may be placed on any instruction regardless of size. |
| @item E |
| An error has occurred. |
| @item |
| An empty reply indicates that the request is not supported by the stub. |
| @end table |
| |
| @item QTStart |
| @cindex @samp{QTStart} packet |
| Begin the tracepoint experiment. Begin collecting data from |
| tracepoint hits in the trace frame buffer. This packet supports the |
| @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate |
| instruction reply packet}). |
| |
| @item QTStop |
| @cindex @samp{QTStop} packet |
| End the tracepoint experiment. Stop collecting trace frames. |
| |
| @item QTEnable:@var{n}:@var{addr} |
| @anchor{QTEnable} |
| @cindex @samp{QTEnable} packet |
| Enable tracepoint @var{n} at address @var{addr} in a started tracepoint |
| experiment. If the tracepoint was previously disabled, then collection |
| of data from it will resume. |
| |
| @item QTDisable:@var{n}:@var{addr} |
| @anchor{QTDisable} |
| @cindex @samp{QTDisable} packet |
| Disable tracepoint @var{n} at address @var{addr} in a started tracepoint |
| experiment. No more data will be collected from the tracepoint unless |
| @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued. |
| |
| @item QTinit |
| @cindex @samp{QTinit} packet |
| Clear the table of tracepoints, and empty the trace frame buffer. |
| |
| @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{} |
| @cindex @samp{QTro} packet |
| Establish the given ranges of memory as ``transparent''. The stub |
| will answer requests for these ranges from memory's current contents, |
| if they were not collected as part of the tracepoint hit. |
| |
| @value{GDBN} uses this to mark read-only regions of memory, like those |
| containing program code. Since these areas never change, they should |
| still have the same contents they did when the tracepoint was hit, so |
| there's no reason for the stub to refuse to provide their contents. |
| |
| @item QTDisconnected:@var{value} |
| @cindex @samp{QTDisconnected} packet |
| Set the choice to what to do with the tracing run when @value{GDBN} |
| disconnects from the target. A @var{value} of 1 directs the target to |
| continue the tracing run, while 0 tells the target to stop tracing if |
| @value{GDBN} is no longer in the picture. |
| |
| @item qTStatus |
| @cindex @samp{qTStatus} packet |
| Ask the stub if there is a trace experiment running right now. |
| |
| The reply has the form: |
| |
| @table @samp |
| |
| @item T@var{running}@r{[};@var{field}@r{]}@dots{} |
| @var{running} is a single digit @code{1} if the trace is presently |
| running, or @code{0} if not. It is followed by semicolon-separated |
| optional fields that an agent may use to report additional status. |
| |
| @end table |
| |
| If the trace is not running, the agent may report any of several |
| explanations as one of the optional fields: |
| |
| @table @samp |
| |
| @item tnotrun:0 |
| No trace has been run yet. |
| |
| @item tstop[:@var{text}]:0 |
| The trace was stopped by a user-originated stop command. The optional |
| @var{text} field is a user-supplied string supplied as part of the |
| stop command (for instance, an explanation of why the trace was |
| stopped manually). It is hex-encoded. |
| |
| @item tfull:0 |
| The trace stopped because the trace buffer filled up. |
| |
| @item tdisconnected:0 |
| The trace stopped because @value{GDBN} disconnected from the target. |
| |
| @item tpasscount:@var{tpnum} |
| The trace stopped because tracepoint @var{tpnum} exceeded its pass count. |
| |
| @item terror:@var{text}:@var{tpnum} |
| The trace stopped because tracepoint @var{tpnum} had an error. The |
| string @var{text} is available to describe the nature of the error |
| (for instance, a divide by zero in the condition expression). |
| @var{text} is hex encoded. |
| |
| @item tunknown:0 |
| The trace stopped for some other reason. |
| |
| @end table |
| |
| Additional optional fields supply statistical and other information. |
| Although not required, they are extremely useful for users monitoring |
| the progress of a trace run. If a trace has stopped, and these |
| numbers are reported, they must reflect the state of the just-stopped |
| trace. |
| |
| @table @samp |
| |
| @item tframes:@var{n} |
| The number of trace frames in the buffer. |
| |
| @item tcreated:@var{n} |
| The total number of trace frames created during the run. This may |
| be larger than the trace frame count, if the buffer is circular. |
| |
| @item tsize:@var{n} |
| The total size of the trace buffer, in bytes. |
| |
| @item tfree:@var{n} |
| The number of bytes still unused in the buffer. |
| |
| @item circular:@var{n} |
| The value of the circular trace buffer flag. @code{1} means that the |
| trace buffer is circular and old trace frames will be discarded if |
| necessary to make room, @code{0} means that the trace buffer is linear |
| and may fill up. |
| |
| @item disconn:@var{n} |
| The value of the disconnected tracing flag. @code{1} means that |
| tracing will continue after @value{GDBN} disconnects, @code{0} means |
| that the trace run will stop. |
| |
| @end table |
| |
| @item qTP:@var{tp}:@var{addr} |
| @cindex tracepoint status, remote request |
| @cindex @samp{qTP} packet |
| Ask the stub for the current state of tracepoint number @var{tp} at |
| address @var{addr}. |
| |
| Replies: |
| @table @samp |
| @item V@var{hits}:@var{usage} |
| The tracepoint has been hit @var{hits} times so far during the trace |
| run, and accounts for @var{usage} in the trace buffer. Note that |
| @code{while-stepping} steps are not counted as separate hits, but the |
| steps' space consumption is added into the usage number. |
| |
| @end table |
| |
| @item qTV:@var{var} |
| @cindex trace state variable value, remote request |
| @cindex @samp{qTV} packet |
| Ask the stub for the value of the trace state variable number @var{var}. |
| |
| Replies: |
| @table @samp |
| @item V@var{value} |
| The value of the variable is @var{value}. This will be the current |
| value of the variable if the user is examining a running target, or a |
| saved value if the variable was collected in the trace frame that the |
| user is looking at. Note that multiple requests may result in |
| different reply values, such as when requesting values while the |
| program is running. |
| |
| @item U |
| The value of the variable is unknown. This would occur, for example, |
| if the user is examining a trace frame in which the requested variable |
| was not collected. |
| @end table |
| |
| @item qTfP |
| @cindex @samp{qTfP} packet |
| @itemx qTsP |
| @cindex @samp{qTsP} packet |
| These packets request data about tracepoints that are being used by |
| the target. @value{GDBN} sends @code{qTfP} to get the first piece |
| of data, and multiple @code{qTsP} to get additional pieces. Replies |
| to these packets generally take the form of the @code{QTDP} packets |
| that define tracepoints. (FIXME add detailed syntax) |
| |
| @item qTfV |
| @cindex @samp{qTfV} packet |
| @itemx qTsV |
| @cindex @samp{qTsV} packet |
| These packets request data about trace state variables that are on the |
| target. @value{GDBN} sends @code{qTfV} to get the first vari of data, |
| and multiple @code{qTsV} to get additional variables. Replies to |
| these packets follow the syntax of the @code{QTDV} packets that define |
| trace state variables. |
| |
| @item qTfSTM |
| @itemx qTsSTM |
| @anchor{qTfSTM} |
| @anchor{qTsSTM} |
| @cindex @samp{qTfSTM} packet |
| @cindex @samp{qTsSTM} packet |
| These packets request data about static tracepoint markers that exist |
| in the target program. @value{GDBN} sends @code{qTfSTM} to get the |
| first piece of data, and multiple @code{qTsSTM} to get additional |
| pieces. Replies to these packets take the following form: |
| |
| Reply: |
| @table @samp |
| @item m @var{address}:@var{id}:@var{extra} |
| A single marker |
| @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{} |
| a comma-separated list of markers |
| @item l |
| (lower case letter @samp{L}) denotes end of list. |
| @item E @var{nn} |
| An error occurred. @var{nn} are hex digits. |
| @item |
| An empty reply indicates that the request is not supported by the |
| stub. |
| @end table |
| |
| @var{address} is encoded in hex. |
| @var{id} and @var{extra} are strings encoded in hex. |
| |
| In response to each query, the target will reply with a list of one or |
| more markers, separated by commas. @value{GDBN} will respond to each |
| reply with a request for more markers (using the @samp{qs} form of the |
| query), until the target responds with @samp{l} (lower-case ell, for |
| @dfn{last}). |
| |
| @item qTSTMat:@var{address} |
| @anchor{qTSTMat} |
| @cindex @samp{qTSTMat} packet |
| This packets requests data about static tracepoint markers in the |
| target program at @var{address}. Replies to this packet follow the |
| syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static |
| tracepoint markers. |
| |
| @item QTSave:@var{filename} |
| @cindex @samp{QTSave} packet |
| This packet directs the target to save trace data to the file name |
| @var{filename} in the target's filesystem. @var{filename} is encoded |
| as a hex string; the interpretation of the file name (relative vs |
| absolute, wild cards, etc) is up to the target. |
| |
| @item qTBuffer:@var{offset},@var{len} |
| @cindex @samp{qTBuffer} packet |
| Return up to @var{len} bytes of the current contents of trace buffer, |
| starting at @var{offset}. The trace buffer is treated as if it were |
| a contiguous collection of traceframes, as per the trace file format. |
| The reply consists as many hex-encoded bytes as the target can deliver |
| in a packet; it is not an error to return fewer than were asked for. |
| A reply consisting of just @code{l} indicates that no bytes are |
| available. |
| |
| @item QTBuffer:circular:@var{value} |
| This packet directs the target to use a circular trace buffer if |
| @var{value} is 1, or a linear buffer if the value is 0. |
| |
| @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{} |
| @cindex @samp{QTNotes} packet |
| This packet adds optional textual notes to the trace run. Allowable |
| types include @code{user}, @code{notes}, and @code{tstop}, the |
| @var{text} fields are arbitrary strings, hex-encoded. |
| |
| @end table |
| |
| @subsection Relocate instruction reply packet |
| When installing fast tracepoints in memory, the target may need to |
| relocate the instruction currently at the tracepoint address to a |
| different address in memory. For most instructions, a simple copy is |
| enough, but, for example, call instructions that implicitly push the |
| return address on the stack, and relative branches or other |
| PC-relative instructions require offset adjustment, so that the effect |
| of executing the instruction at a different address is the same as if |
| it had executed in the original location. |
| |
| In response to several of the tracepoint packets, the target may also |
| respond with a number of intermediate @samp{qRelocInsn} request |
| packets before the final result packet, to have @value{GDBN} handle |
| this relocation operation. If a packet supports this mechanism, its |
| documentation will explicitly say so. See for example the above |
| descriptions for the @samp{QTStart} and @samp{QTDP} packets. The |
| format of the request is: |
| |
| @table @samp |
| @item qRelocInsn:@var{from};@var{to} |
| |
| This requests @value{GDBN} to copy instruction at address @var{from} |
| to address @var{to}, possibly adjusted so that executing the |
| instruction at @var{to} has the same effect as executing it at |
| @var{from}. @value{GDBN} writes the adjusted instruction to target |
| memory starting at @var{to}. |
| @end table |
| |
| Replies: |
| @table @samp |
| @item qRelocInsn:@var{adjusted_size} |
| Informs the stub the relocation is complete. @var{adjusted_size} is |
| the length in bytes of resulting relocated instruction sequence. |
| @item E @var{NN} |
| A badly formed request was detected, or an error was encountered while |
| relocating the instruction. |
| @end table |
| |
| @node Host I/O Packets |
| @section Host I/O Packets |
| @cindex Host I/O, remote protocol |
| @cindex file transfer, remote protocol |
| |
| The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O |
| operations on the far side of a remote link. For example, Host I/O is |
| used to upload and download files to a remote target with its own |
| filesystem. Host I/O uses the same constant values and data structure |
| layout as the target-initiated File-I/O protocol. However, the |
| Host I/O packets are structured differently. The target-initiated |
| protocol relies on target memory to store parameters and buffers. |
| Host I/O requests are initiated by @value{GDBN}, and the |
| target's memory is not involved. @xref{File-I/O Remote Protocol |
| Extension}, for more details on the target-initiated protocol. |
| |
| The Host I/O request packets all encode a single operation along with |
| its arguments. They have this format: |
| |
| @table @samp |
| |
| @item vFile:@var{operation}: @var{parameter}@dots{} |
| @var{operation} is the name of the particular request; the target |
| should compare the entire packet name up to the second colon when checking |
| for a supported operation. The format of @var{parameter} depends on |
| the operation. Numbers are always passed in hexadecimal. Negative |
| numbers have an explicit minus sign (i.e.@: two's complement is not |
| used). Strings (e.g.@: filenames) are encoded as a series of |
| hexadecimal bytes. The last argument to a system call may be a |
| buffer of escaped binary data (@pxref{Binary Data}). |
| |
| @end table |
| |
| The valid responses to Host I/O packets are: |
| |
| @table @samp |
| |
| @item F @var{result} [, @var{errno}] [; @var{attachment}] |
| @var{result} is the integer value returned by this operation, usually |
| non-negative for success and -1 for errors. If an error has occured, |
| @var{errno} will be included in the result. @var{errno} will have a |
| value defined by the File-I/O protocol (@pxref{Errno Values}). For |
| operations which return data, @var{attachment} supplies the data as a |
| binary buffer. Binary buffers in response packets are escaped in the |
| normal way (@pxref{Binary Data}). See the individual packet |
| documentation for the interpretation of @var{result} and |
| @var{attachment}. |
| |
| @item |
| An empty response indicates that this operation is not recognized. |
| |
| @end table |
| |
| These are the supported Host I/O operations: |
| |
| @table @samp |
| @item vFile:open: @var{pathname}, @var{flags}, @var{mode} |
| Open a file at @var{pathname} and return a file descriptor for it, or |
| return -1 if an error occurs. @var{pathname} is a string, |
| @var{flags} is an integer indicating a mask of open flags |
| (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask |
| of mode bits to use if the file is created (@pxref{mode_t Values}). |
| @xref{open}, for details of the open flags and mode values. |
| |
| @item vFile:close: @var{fd} |
| Close the open file corresponding to @var{fd} and return 0, or |
| -1 if an error occurs. |
| |
| @item vFile:pread: @var{fd}, @var{count}, @var{offset} |
| Read data from the open file corresponding to @var{fd}. Up to |
| @var{count} bytes will be read from the file, starting at @var{offset} |
| relative to the start of the file. The target may read fewer bytes; |
| common reasons include packet size limits and an end-of-file |
| condition. The number of bytes read is returned. Zero should only be |
| returned for a successful read at the end of the file, or if |
| @var{count} was zero. |
| |
| The data read should be returned as a binary attachment on success. |
| If zero bytes were read, the response should include an empty binary |
| attachment (i.e.@: a trailing semicolon). The return value is the |
| number of target bytes read; the binary attachment may be longer if |
| some characters were escaped. |
| |
| @item vFile:pwrite: @var{fd}, @var{offset}, @var{data} |
| Write @var{data} (a binary buffer) to the open file corresponding |
| to @var{fd}. Start the write at @var{offset} from the start of the |
| file. Unlike many @code{write} system calls, there is no |
| separate @var{count} argument; the length of @var{data} in the |
| packet is used. @samp{vFile:write} returns the number of bytes written, |
| which may be shorter than the length of @var{data}, or -1 if an |
| error occurred. |
| |
| @item vFile:unlink: @var{pathname} |
| Delete the file at @var{pathname} on the target. Return 0, |
| or -1 if an error occurs. @var{pathname} is a string. |
| |
| @item vFile:readlink: @var{filename} |
| Read value of symbolic link @var{filename} on the target. Return |
| the number of bytes read, or -1 if an error occurs. |
| |
| The data read should be returned as a binary attachment on success. |
| If zero bytes were read, the response should include an empty binary |
| attachment (i.e.@: a trailing semicolon). The return value is the |
| number of target bytes read; the binary attachment may be longer if |
| some characters were escaped. |
| |
| @end table |
| |
| @node Interrupts |
| @section Interrupts |
| @cindex interrupts (remote protocol) |
| |
| When a program on the remote target is running, @value{GDBN} may |
| attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or |
| a @code{BREAK} followed by @code{g}, |
| control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}. |
| |
| The precise meaning of @code{BREAK} is defined by the transport |
| mechanism and may, in fact, be undefined. @value{GDBN} does not |
| currently define a @code{BREAK} mechanism for any of the network |
| interfaces except for TCP, in which case @value{GDBN} sends the |
| @code{telnet} BREAK sequence. |
| |
| @samp{Ctrl-C}, on the other hand, is defined and implemented for all |
| transport mechanisms. It is represented by sending the single byte |
| @code{0x03} without any of the usual packet overhead described in |
| the Overview section (@pxref{Overview}). When a @code{0x03} byte is |
| transmitted as part of a packet, it is considered to be packet data |
| and does @emph{not} represent an interrupt. E.g., an @samp{X} packet |
| (@pxref{X packet}), used for binary downloads, may include an unescaped |
| @code{0x03} as part of its packet. |
| |
| @code{BREAK} followed by @code{g} is also known as Magic SysRq g. |
| When Linux kernel receives this sequence from serial port, |
| it stops execution and connects to gdb. |
| |
| Stubs are not required to recognize these interrupt mechanisms and the |
| precise meaning associated with receipt of the interrupt is |
| implementation defined. If the target supports debugging of multiple |
| threads and/or processes, it should attempt to interrupt all |
| currently-executing threads and processes. |
| If the stub is successful at interrupting the |
| running program, it should send one of the stop |
| reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result |
| of successfully stopping the program in all-stop mode, and a stop reply |
| for each stopped thread in non-stop mode. |
| Interrupts received while the |
| program is stopped are discarded. |
| |
| @node Notification Packets |
| @section Notification Packets |
| @cindex notification packets |
| @cindex packets, notification |
| |
| The @value{GDBN} remote serial protocol includes @dfn{notifications}, |
| packets that require no acknowledgment. Both the GDB and the stub |
| may send notifications (although the only notifications defined at |
| present are sent by the stub). Notifications carry information |
| without incurring the round-trip latency of an acknowledgment, and so |
| are useful for low-impact communications where occasional packet loss |
| is not a problem. |
| |
| A notification packet has the form @samp{% @var{data} # |
| @var{checksum}}, where @var{data} is the content of the notification, |
| and @var{checksum} is a checksum of @var{data}, computed and formatted |
| as for ordinary @value{GDBN} packets. A notification's @var{data} |
| never contains @samp{$}, @samp{%} or @samp{#} characters. Upon |
| receiving a notification, the recipient sends no @samp{+} or @samp{-} |
| to acknowledge the notification's receipt or to report its corruption. |
| |
| Every notification's @var{data} begins with a name, which contains no |
| colon characters, followed by a colon character. |
| |
| Recipients should silently ignore corrupted notifications and |
| notifications they do not understand. Recipients should restart |
| timeout periods on receipt of a well-formed notification, whether or |
| not they understand it. |
| |
| Senders should only send the notifications described here when this |
| protocol description specifies that they are permitted. In the |
| future, we may extend the protocol to permit existing notifications in |
| new contexts; this rule helps older senders avoid confusing newer |
| recipients. |
| |
| (Older versions of @value{GDBN} ignore bytes received until they see |
| the @samp{$} byte that begins an ordinary packet, so new stubs may |
| transmit notifications without fear of confusing older clients. There |
| are no notifications defined for @value{GDBN} to send at the moment, but we |
| assume that most older stubs would ignore them, as well.) |
| |
| The following notification packets from the stub to @value{GDBN} are |
| defined: |
| |
| @table @samp |
| @item Stop: @var{reply} |
| Report an asynchronous stop event in non-stop mode. |
| The @var{reply} has the form of a stop reply, as |
| described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop}, |
| for information on how these notifications are acknowledged by |
| @value{GDBN}. |
| @end table |
| |
| @node Remote Non-Stop |
| @section Remote Protocol Support for Non-Stop Mode |
| |
| @value{GDBN}'s remote protocol supports non-stop debugging of |
| multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub |
| supports non-stop mode, it should report that to @value{GDBN} by including |
| @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}). |
| |
| @value{GDBN} typically sends a @samp{QNonStop} packet only when |
| establishing a new connection with the stub. Entering non-stop mode |
| does not alter the state of any currently-running threads, but targets |
| must stop all threads in any already-attached processes when entering |
| all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to |
| probe the target state after a mode change. |
| |
| In non-stop mode, when an attached process encounters an event that |
| would otherwise be reported with a stop reply, it uses the |
| asynchronous notification mechanism (@pxref{Notification Packets}) to |
| inform @value{GDBN}. In contrast to all-stop mode, where all threads |
| in all processes are stopped when a stop reply is sent, in non-stop |
| mode only the thread reporting the stop event is stopped. That is, |
| when reporting a @samp{S} or @samp{T} response to indicate completion |
| of a step operation, hitting a breakpoint, or a fault, only the |
| affected thread is stopped; any other still-running threads continue |
| to run. When reporting a @samp{W} or @samp{X} response, all running |
| threads belonging to other attached processes continue to run. |
| |
| Only one stop reply notification at a time may be pending; if |
| additional stop events occur before @value{GDBN} has acknowledged the |
| previous notification, they must be queued by the stub for later |
| synchronous transmission in response to @samp{vStopped} packets from |
| @value{GDBN}. Because the notification mechanism is unreliable, |
| the stub is permitted to resend a stop reply notification |
| if it believes @value{GDBN} may not have received it. @value{GDBN} |
| ignores additional stop reply notifications received before it has |
| finished processing a previous notification and the stub has completed |
| sending any queued stop events. |
| |
| Otherwise, @value{GDBN} must be prepared to receive a stop reply |
| notification at any time. Specifically, they may appear when |
| @value{GDBN} is not otherwise reading input from the stub, or when |
| @value{GDBN} is expecting to read a normal synchronous response or a |
| @samp{+}/@samp{-} acknowledgment to a packet it has sent. |
| Notification packets are distinct from any other communication from |
| the stub so there is no ambiguity. |
| |
| After receiving a stop reply notification, @value{GDBN} shall |
| acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet}) |
| as a regular, synchronous request to the stub. Such acknowledgment |
| is not required to happen immediately, as @value{GDBN} is permitted to |
| send other, unrelated packets to the stub first, which the stub should |
| process normally. |
| |
| Upon receiving a @samp{vStopped} packet, if the stub has other queued |
| stop events to report to @value{GDBN}, it shall respond by sending a |
| normal stop reply response. @value{GDBN} shall then send another |
| @samp{vStopped} packet to solicit further responses; again, it is |
| permitted to send other, unrelated packets as well which the stub |
| should process normally. |
| |
| If the stub receives a @samp{vStopped} packet and there are no |
| additional stop events to report, the stub shall return an @samp{OK} |
| response. At this point, if further stop events occur, the stub shall |
| send a new stop reply notification, @value{GDBN} shall accept the |
| notification, and the process shall be repeated. |
| |
| In non-stop mode, the target shall respond to the @samp{?} packet as |
| follows. First, any incomplete stop reply notification/@samp{vStopped} |
| sequence in progress is abandoned. The target must begin a new |
| sequence reporting stop events for all stopped threads, whether or not |
| it has previously reported those events to @value{GDBN}. The first |
| stop reply is sent as a synchronous reply to the @samp{?} packet, and |
| subsequent stop replies are sent as responses to @samp{vStopped} packets |
| using the mechanism described above. The target must not send |
| asynchronous stop reply notifications until the sequence is complete. |
| If all threads are running when the target receives the @samp{?} packet, |
| or if the target is not attached to any process, it shall respond |
| @samp{OK}. |
| |
| @node Packet Acknowledgment |
| @section Packet Acknowledgment |
| |
| @cindex acknowledgment, for @value{GDBN} remote |
| @cindex packet acknowledgment, for @value{GDBN} remote |
| By default, when either the host or the target machine receives a packet, |
| the first response expected is an acknowledgment: either @samp{+} (to indicate |
| the package was received correctly) or @samp{-} (to request retransmission). |
| This mechanism allows the @value{GDBN} remote protocol to operate over |
| unreliable transport mechanisms, such as a serial line. |
| |
| In cases where the transport mechanism is itself reliable (such as a pipe or |
| TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant. |
| It may be desirable to disable them in that case to reduce communication |
| overhead, or for other reasons. This can be accomplished by means of the |
| @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}. |
| |
| When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or |
| expect @samp{+}/@samp{-} protocol acknowledgments. The packet |
| and response format still includes the normal checksum, as described in |
| @ref{Overview}, but the checksum may be ignored by the receiver. |
| |
| If the stub supports @samp{QStartNoAckMode} and prefers to operate in |
| no-acknowledgment mode, it should report that to @value{GDBN} |
| by including @samp{QStartNoAckMode+} in its response to @samp{qSupported}; |
| @pxref{qSupported}. |
| If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been |
| disabled via the @code{set remote noack-packet off} command |
| (@pxref{Remote Configuration}), |
| @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub. |
| Only then may the stub actually turn off packet acknowledgments. |
| @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK} |
| response, which can be safely ignored by the stub. |
| |
| Note that @code{set remote noack-packet} command only affects negotiation |
| between @value{GDBN} and the stub when subsequent connections are made; |
| it does not affect the protocol acknowledgment state for any current |
| connection. |
| Since @samp{+}/@samp{-} acknowledgments are enabled by default when a |
| new connection is established, |
| there is also no protocol request to re-enable the acknowledgments |
| for the current connection, once disabled. |
| |
| @node Examples |
| @section Examples |
| |
| Example sequence of a target being re-started. Notice how the restart |
| does not get any direct output: |
| |
| @smallexample |
| -> @code{R00} |
| <- @code{+} |
| @emph{target restarts} |
| -> @code{?} |
| <- @code{+} |
| <- @code{T001:1234123412341234} |
| -> @code{+} |
| @end smallexample |
| |
| Example sequence of a target being stepped by a single instruction: |
| |
| @smallexample |
| -> @code{G1445@dots{}} |
| <- @code{+} |
| -> @code{s} |
| <- @code{+} |
| @emph{time passes} |
| <- @code{T001:1234123412341234} |
| -> @code{+} |
| -> @code{g} |
| <- @code{+} |
| <- @code{1455@dots{}} |
| -> @code{+} |
| @end smallexample |
| |
| @node File-I/O Remote Protocol Extension |
| @section File-I/O Remote Protocol Extension |
| @cindex File-I/O remote protocol extension |
| |
| @menu |
| * File-I/O Overview:: |
| * Protocol Basics:: |
| * The F Request Packet:: |
| * The F Reply Packet:: |
| * The Ctrl-C Message:: |
| * Console I/O:: |
| * List of Supported Calls:: |
| * Protocol-specific Representation of Datatypes:: |
| * Constants:: |
| * File-I/O Examples:: |
| @end menu |
| |
| @node File-I/O Overview |
| @subsection File-I/O Overview |
| @cindex file-i/o overview |
| |
| The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the |
| target to use the host's file system and console I/O to perform various |
| system calls. System calls on the target system are translated into a |
| remote protocol packet to the host system, which then performs the needed |
| actions and returns a response packet to the target system. |
| This simulates file system operations even on targets that lack file systems. |
| |
| The protocol is defined to be independent of both the host and target systems. |
| It uses its own internal representation of datatypes and values. Both |
| @value{GDBN} and the target's @value{GDBN} stub are responsible for |
| translating the system-dependent value representations into the internal |
| protocol representations when data is transmitted. |
| |
| The communication is synchronous. A system call is possible only when |
| @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S} |
| or @samp{s} packets. While @value{GDBN} handles the request for a system call, |
| the target is stopped to allow deterministic access to the target's |
| memory. Therefore File-I/O is not interruptible by target signals. On |
| the other hand, it is possible to interrupt File-I/O by a user interrupt |
| (@samp{Ctrl-C}) within @value{GDBN}. |
| |
| The target's request to perform a host system call does not finish |
| the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means, |
| after finishing the system call, the target returns to continuing the |
| previous activity (continue, step). No additional continue or step |
| request from @value{GDBN} is required. |
| |
| @smallexample |
| (@value{GDBP}) continue |
| <- target requests 'system call X' |
| target is stopped, @value{GDBN} executes system call |
| -> @value{GDBN} returns result |
| ... target continues, @value{GDBN} returns to wait for the target |
| <- target hits breakpoint and sends a Txx packet |
| @end smallexample |
| |
| The protocol only supports I/O on the console and to regular files on |
| the host file system. Character or block special devices, pipes, |
| named pipes, sockets or any other communication method on the host |
| system are not supported by this protocol. |
| |
| File I/O is not supported in non-stop mode. |
| |
| @node Protocol Basics |
| @subsection Protocol Basics |
| @cindex protocol basics, file-i/o |
| |
| The File-I/O protocol uses the @code{F} packet as the request as well |
| as reply packet. Since a File-I/O system call can only occur when |
| @value{GDBN} is waiting for a response from the continuing or stepping target, |
| the File-I/O request is a reply that @value{GDBN} has to expect as a result |
| of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet. |
| This @code{F} packet contains all information needed to allow @value{GDBN} |
| to call the appropriate host system call: |
| |
| @itemize @bullet |
| @item |
| A unique identifier for the requested system call. |
| |
| @item |
| All parameters to the system call. Pointers are given as addresses |
| in the target memory address space. Pointers to strings are given as |
| pointer/length pair. Numerical values are given as they are. |
| Numerical control flags are given in a protocol-specific representation. |
| |
| @end itemize |
| |
| At this point, @value{GDBN} has to perform the following actions. |
| |
| @itemize @bullet |
| @item |
| If the parameters include pointer values to data needed as input to a |
| system call, @value{GDBN} requests this data from the target with a |
| standard @code{m} packet request. This additional communication has to be |
| expected by the target implementation and is handled as any other @code{m} |
| packet. |
| |
| @item |
| @value{GDBN} translates all value from protocol representation to host |
| representation as needed. Datatypes are coerced into the host types. |
| |
| @item |
| @value{GDBN} calls the system call. |
| |
| @item |
| It then coerces datatypes back to protocol representation. |
| |
| @item |
| If the system call is expected to return data in buffer space specified |
| by pointer parameters to the call, the data is transmitted to the |
| target using a @code{M} or @code{X} packet. This packet has to be expected |
| by the target implementation and is handled as any other @code{M} or @code{X} |
| packet. |
| |
| @end itemize |
| |
| Eventually @value{GDBN} replies with another @code{F} packet which contains all |
| necessary information for the target to continue. This at least contains |
| |
| @itemize @bullet |
| @item |
| Return value. |
| |
| @item |
| @code{errno}, if has been changed by the system call. |
| |
| @item |
| ``Ctrl-C'' flag. |
| |
| @end itemize |
| |
| After having done the needed type and value coercion, the target continues |
| the latest continue or step action. |
| |
| @node The F Request Packet |
| @subsection The @code{F} Request Packet |
| @cindex file-i/o request packet |
| @cindex @code{F} request packet |
| |
| The @code{F} request packet has the following format: |
| |
| @table @samp |
| @item F@var{call-id},@var{parameter@dots{}} |
| |
| @var{call-id} is the identifier to indicate the host system call to be called. |
| This is just the name of the function. |
| |
| @var{parameter@dots{}} are the parameters to the system call. |
| Parameters are hexadecimal integer values, either the actual values in case |
| of scalar datatypes, pointers to target buffer space in case of compound |
| datatypes and unspecified memory areas, or pointer/length pairs in case |
| of string parameters. These are appended to the @var{call-id} as a |
| comma-delimited list. All values are transmitted in ASCII |
| string representation, pointer/length pairs separated by a slash. |
| |
| @end table |
| |
| |
| |
| @node The F Reply Packet |
| @subsection The @code{F} Reply Packet |
| @cindex file-i/o reply packet |
| @cindex @code{F} reply packet |
| |
| The @code{F} reply packet has the following format: |
| |
| @table @samp |
| |
| @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment} |
| |
| @var{retcode} is the return code of the system call as hexadecimal value. |
| |
| @var{errno} is the @code{errno} set by the call, in protocol-specific |
| representation. |
| This parameter can be omitted if the call was successful. |
| |
| @var{Ctrl-C flag} is only sent if the user requested a break. In this |
| case, @var{errno} must be sent as well, even if the call was successful. |
| The @var{Ctrl-C flag} itself consists of the character @samp{C}: |
| |
| @smallexample |
| F0,0,C |
| @end smallexample |
| |
| @noindent |
| or, if the call was interrupted before the host call has been performed: |
| |
| @smallexample |
| F-1,4,C |
| @end smallexample |
| |
| @noindent |
| assuming 4 is the protocol-specific representation of @code{EINTR}. |
| |
| @end table |
| |
| |
| @node The Ctrl-C Message |
| @subsection The @samp{Ctrl-C} Message |
| @cindex ctrl-c message, in file-i/o protocol |
| |
| If the @samp{Ctrl-C} flag is set in the @value{GDBN} |
| reply packet (@pxref{The F Reply Packet}), |
| the target should behave as if it had |
| gotten a break message. The meaning for the target is ``system call |
| interrupted by @code{SIGINT}''. Consequentially, the target should actually stop |
| (as with a break message) and return to @value{GDBN} with a @code{T02} |
| packet. |
| |
| It's important for the target to know in which |
| state the system call was interrupted. There are two possible cases: |
| |
| @itemize @bullet |
| @item |
| The system call hasn't been performed on the host yet. |
| |
| @item |
| The system call on the host has been finished. |
| |
| @end itemize |
| |
| These two states can be distinguished by the target by the value of the |
| returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system |
| call hasn't been performed. This is equivalent to the @code{EINTR} handling |
| on POSIX systems. In any other case, the target may presume that the |
| system call has been finished --- successfully or not --- and should behave |
| as if the break message arrived right after the system call. |
| |
| @value{GDBN} must behave reliably. If the system call has not been called |
| yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as |
| @code{errno} in the packet. If the system call on the host has been finished |
| before the user requests a break, the full action must be finished by |
| @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary. |
| The @code{F} packet may only be sent when either nothing has happened |
| or the full action has been completed. |
| |
| @node Console I/O |
| @subsection Console I/O |
| @cindex console i/o as part of file-i/o |
| |
| By default and if not explicitly closed by the target system, the file |
| descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output |
| on the @value{GDBN} console is handled as any other file output operation |
| (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled |
| by @value{GDBN} so that after the target read request from file descriptor |
| 0 all following typing is buffered until either one of the following |
| conditions is met: |
| |
| @itemize @bullet |
| @item |
| The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the |
| @code{read} |
| system call is treated as finished. |
| |
| @item |
| The user presses @key{RET}. This is treated as end of input with a trailing |
| newline. |
| |
| @item |
| The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing |
| character (neither newline nor @samp{Ctrl-D}) is appended to the input. |
| |
| @end itemize |
| |
| If the user has typed more characters than fit in the buffer given to |
| the @code{read} call, the trailing characters are buffered in @value{GDBN} until |
| either another @code{read(0, @dots{})} is requested by the target, or debugging |
| is stopped at the user's request. |
| |
| |
| @node List of Supported Calls |
| @subsection List of Supported Calls |
| @cindex list of supported file-i/o calls |
| |
| @menu |
| * open:: |
| * close:: |
| * read:: |
| * write:: |
| * lseek:: |
| * rename:: |
| * unlink:: |
| * stat/fstat:: |
| * gettimeofday:: |
| * isatty:: |
| * system:: |
| @end menu |
| |
| @node open |
| @unnumberedsubsubsec open |
| @cindex open, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int open(const char *pathname, int flags); |
| int open(const char *pathname, int flags, mode_t mode); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}} |
| |
| @noindent |
| @var{flags} is the bitwise @code{OR} of the following values: |
| |
| @table @code |
| @item O_CREAT |
| If the file does not exist it will be created. The host |
| rules apply as far as file ownership and time stamps |
| are concerned. |
| |
| @item O_EXCL |
| When used with @code{O_CREAT}, if the file already exists it is |
| an error and open() fails. |
| |
| @item O_TRUNC |
| If the file already exists and the open mode allows |
| writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be |
| truncated to zero length. |
| |
| @item O_APPEND |
| The file is opened in append mode. |
| |
| @item O_RDONLY |
| The file is opened for reading only. |
| |
| @item O_WRONLY |
| The file is opened for writing only. |
| |
| @item O_RDWR |
| The file is opened for reading and writing. |
| @end table |
| |
| @noindent |
| Other bits are silently ignored. |
| |
| |
| @noindent |
| @var{mode} is the bitwise @code{OR} of the following values: |
| |
| @table @code |
| @item S_IRUSR |
| User has read permission. |
| |
| @item S_IWUSR |
| User has write permission. |
| |
| @item S_IRGRP |
| Group has read permission. |
| |
| @item S_IWGRP |
| Group has write permission. |
| |
| @item S_IROTH |
| Others have read permission. |
| |
| @item S_IWOTH |
| Others have write permission. |
| @end table |
| |
| @noindent |
| Other bits are silently ignored. |
| |
| |
| @item Return value: |
| @code{open} returns the new file descriptor or -1 if an error |
| occurred. |
| |
| @item Errors: |
| |
| @table @code |
| @item EEXIST |
| @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used. |
| |
| @item EISDIR |
| @var{pathname} refers to a directory. |
| |
| @item EACCES |
| The requested access is not allowed. |
| |
| @item ENAMETOOLONG |
| @var{pathname} was too long. |
| |
| @item ENOENT |
| A directory component in @var{pathname} does not exist. |
| |
| @item ENODEV |
| @var{pathname} refers to a device, pipe, named pipe or socket. |
| |
| @item EROFS |
| @var{pathname} refers to a file on a read-only filesystem and |
| write access was requested. |
| |
| @item EFAULT |
| @var{pathname} is an invalid pointer value. |
| |
| @item ENOSPC |
| No space on device to create the file. |
| |
| @item EMFILE |
| The process already has the maximum number of files open. |
| |
| @item ENFILE |
| The limit on the total number of files open on the system |
| has been reached. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node close |
| @unnumberedsubsubsec close |
| @cindex close, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int close(int fd); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fclose,@var{fd}} |
| |
| @item Return value: |
| @code{close} returns zero on success, or -1 if an error occurred. |
| |
| @item Errors: |
| |
| @table @code |
| @item EBADF |
| @var{fd} isn't a valid open file descriptor. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node read |
| @unnumberedsubsubsec read |
| @cindex read, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int read(int fd, void *buf, unsigned int count); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fread,@var{fd},@var{bufptr},@var{count}} |
| |
| @item Return value: |
| On success, the number of bytes read is returned. |
| Zero indicates end of file. If count is zero, read |
| returns zero as well. On error, -1 is returned. |
| |
| @item Errors: |
| |
| @table @code |
| @item EBADF |
| @var{fd} is not a valid file descriptor or is not open for |
| reading. |
| |
| @item EFAULT |
| @var{bufptr} is an invalid pointer value. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node write |
| @unnumberedsubsubsec write |
| @cindex write, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int write(int fd, const void *buf, unsigned int count); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fwrite,@var{fd},@var{bufptr},@var{count}} |
| |
| @item Return value: |
| On success, the number of bytes written are returned. |
| Zero indicates nothing was written. On error, -1 |
| is returned. |
| |
| @item Errors: |
| |
| @table @code |
| @item EBADF |
| @var{fd} is not a valid file descriptor or is not open for |
| writing. |
| |
| @item EFAULT |
| @var{bufptr} is an invalid pointer value. |
| |
| @item EFBIG |
| An attempt was made to write a file that exceeds the |
| host-specific maximum file size allowed. |
| |
| @item ENOSPC |
| No space on device to write the data. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node lseek |
| @unnumberedsubsubsec lseek |
| @cindex lseek, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| long lseek (int fd, long offset, int flag); |
| @end smallexample |
| |
| @item Request: |
| @samp{Flseek,@var{fd},@var{offset},@var{flag}} |
| |
| @var{flag} is one of: |
| |
| @table @code |
| @item SEEK_SET |
| The offset is set to @var{offset} bytes. |
| |
| @item SEEK_CUR |
| The offset is set to its current location plus @var{offset} |
| bytes. |
| |
| @item SEEK_END |
| The offset is set to the size of the file plus @var{offset} |
| bytes. |
| @end table |
| |
| @item Return value: |
| On success, the resulting unsigned offset in bytes from |
| the beginning of the file is returned. Otherwise, a |
| value of -1 is returned. |
| |
| @item Errors: |
| |
| @table @code |
| @item EBADF |
| @var{fd} is not a valid open file descriptor. |
| |
| @item ESPIPE |
| @var{fd} is associated with the @value{GDBN} console. |
| |
| @item EINVAL |
| @var{flag} is not a proper value. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node rename |
| @unnumberedsubsubsec rename |
| @cindex rename, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int rename(const char *oldpath, const char *newpath); |
| @end smallexample |
| |
| @item Request: |
| @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}} |
| |
| @item Return value: |
| On success, zero is returned. On error, -1 is returned. |
| |
| @item Errors: |
| |
| @table @code |
| @item EISDIR |
| @var{newpath} is an existing directory, but @var{oldpath} is not a |
| directory. |
| |
| @item EEXIST |
| @var{newpath} is a non-empty directory. |
| |
| @item EBUSY |
| @var{oldpath} or @var{newpath} is a directory that is in use by some |
| process. |
| |
| @item EINVAL |
| An attempt was made to make a directory a subdirectory |
| of itself. |
| |
| @item ENOTDIR |
| A component used as a directory in @var{oldpath} or new |
| path is not a directory. Or @var{oldpath} is a directory |
| and @var{newpath} exists but is not a directory. |
| |
| @item EFAULT |
| @var{oldpathptr} or @var{newpathptr} are invalid pointer values. |
| |
| @item EACCES |
| No access to the file or the path of the file. |
| |
| @item ENAMETOOLONG |
| |
| @var{oldpath} or @var{newpath} was too long. |
| |
| @item ENOENT |
| A directory component in @var{oldpath} or @var{newpath} does not exist. |
| |
| @item EROFS |
| The file is on a read-only filesystem. |
| |
| @item ENOSPC |
| The device containing the file has no room for the new |
| directory entry. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node unlink |
| @unnumberedsubsubsec unlink |
| @cindex unlink, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int unlink(const char *pathname); |
| @end smallexample |
| |
| @item Request: |
| @samp{Funlink,@var{pathnameptr}/@var{len}} |
| |
| @item Return value: |
| On success, zero is returned. On error, -1 is returned. |
| |
| @item Errors: |
| |
| @table @code |
| @item EACCES |
| No access to the file or the path of the file. |
| |
| @item EPERM |
| The system does not allow unlinking of directories. |
| |
| @item EBUSY |
| The file @var{pathname} cannot be unlinked because it's |
| being used by another process. |
| |
| @item EFAULT |
| @var{pathnameptr} is an invalid pointer value. |
| |
| @item ENAMETOOLONG |
| @var{pathname} was too long. |
| |
| @item ENOENT |
| A directory component in @var{pathname} does not exist. |
| |
| @item ENOTDIR |
| A component of the path is not a directory. |
| |
| @item EROFS |
| The file is on a read-only filesystem. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node stat/fstat |
| @unnumberedsubsubsec stat/fstat |
| @cindex fstat, file-i/o system call |
| @cindex stat, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int stat(const char *pathname, struct stat *buf); |
| int fstat(int fd, struct stat *buf); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@* |
| @samp{Ffstat,@var{fd},@var{bufptr}} |
| |
| @item Return value: |
| On success, zero is returned. On error, -1 is returned. |
| |
| @item Errors: |
| |
| @table @code |
| @item EBADF |
| @var{fd} is not a valid open file. |
| |
| @item ENOENT |
| A directory component in @var{pathname} does not exist or the |
| path is an empty string. |
| |
| @item ENOTDIR |
| A component of the path is not a directory. |
| |
| @item EFAULT |
| @var{pathnameptr} is an invalid pointer value. |
| |
| @item EACCES |
| No access to the file or the path of the file. |
| |
| @item ENAMETOOLONG |
| @var{pathname} was too long. |
| |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @node gettimeofday |
| @unnumberedsubsubsec gettimeofday |
| @cindex gettimeofday, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int gettimeofday(struct timeval *tv, void *tz); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fgettimeofday,@var{tvptr},@var{tzptr}} |
| |
| @item Return value: |
| On success, 0 is returned, -1 otherwise. |
| |
| @item Errors: |
| |
| @table @code |
| @item EINVAL |
| @var{tz} is a non-NULL pointer. |
| |
| @item EFAULT |
| @var{tvptr} and/or @var{tzptr} is an invalid pointer value. |
| @end table |
| |
| @end table |
| |
| @node isatty |
| @unnumberedsubsubsec isatty |
| @cindex isatty, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int isatty(int fd); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fisatty,@var{fd}} |
| |
| @item Return value: |
| Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise. |
| |
| @item Errors: |
| |
| @table @code |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| Note that the @code{isatty} call is treated as a special case: it returns |
| 1 to the target if the file descriptor is attached |
| to the @value{GDBN} console, 0 otherwise. Implementing through system calls |
| would require implementing @code{ioctl} and would be more complex than |
| needed. |
| |
| |
| @node system |
| @unnumberedsubsubsec system |
| @cindex system, file-i/o system call |
| |
| @table @asis |
| @item Synopsis: |
| @smallexample |
| int system(const char *command); |
| @end smallexample |
| |
| @item Request: |
| @samp{Fsystem,@var{commandptr}/@var{len}} |
| |
| @item Return value: |
| If @var{len} is zero, the return value indicates whether a shell is |
| available. A zero return value indicates a shell is not available. |
| For non-zero @var{len}, the value returned is -1 on error and the |
| return status of the command otherwise. Only the exit status of the |
| command is returned, which is extracted from the host's @code{system} |
| return value by calling @code{WEXITSTATUS(retval)}. In case |
| @file{/bin/sh} could not be executed, 127 is returned. |
| |
| @item Errors: |
| |
| @table @code |
| @item EINTR |
| The call was interrupted by the user. |
| @end table |
| |
| @end table |
| |
| @value{GDBN} takes over the full task of calling the necessary host calls |
| to perform the @code{system} call. The return value of @code{system} on |
| the host is simplified before it's returned |
| to the target. Any termination signal information from the child process |
| is discarded, and the return value consists |
| entirely of the exit status of the called command. |
| |
| Due to security concerns, the @code{system} call is by default refused |
| by @value{GDBN}. The user has to allow this call explicitly with the |
| @code{set remote system-call-allowed 1} command. |
| |
| @table @code |
| @item set remote system-call-allowed |
| @kindex set remote system-call-allowed |
| Control whether to allow the @code{system} calls in the File I/O |
| protocol for the remote target. The default is zero (disabled). |
| |
| @item show remote system-call-allowed |
| @kindex show remote system-call-allowed |
| Show whether the @code{system} calls are allowed in the File I/O |
| protocol. |
| @end table |
| |
| @node Protocol-specific Representation of Datatypes |
| @subsection Protocol-specific Representation of Datatypes |
| @cindex protocol-specific representation of datatypes, in file-i/o protocol |
| |
| @menu |
| * Integral Datatypes:: |
| * Pointer Values:: |
| * Memory Transfer:: |
| * struct stat:: |
| * struct timeval:: |
| @end menu |
| |
| @node Integral Datatypes |
| @unnumberedsubsubsec Integral Datatypes |
| @cindex integral datatypes, in file-i/o protocol |
| |
| The integral datatypes used in the system calls are @code{int}, |
| @code{unsigned int}, @code{long}, @code{unsigned long}, |
| @code{mode_t}, and @code{time_t}. |
| |
| @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are |
| implemented as 32 bit values in this protocol. |
| |
| @code{long} and @code{unsigned long} are implemented as 64 bit types. |
| |
| @xref{Limits}, for corresponding MIN and MAX values (similar to those |
| in @file{limits.h}) to allow range checking on host and target. |
| |
| @code{time_t} datatypes are defined as seconds since the Epoch. |
| |
| All integral datatypes transferred as part of a memory read or write of a |
| structured datatype e.g.@: a @code{struct stat} have to be given in big endian |
| byte order. |
| |
| @node Pointer Values |
| @unnumberedsubsubsec Pointer Values |
| @cindex pointer values, in file-i/o protocol |
| |
| Pointers to target data are transmitted as they are. An exception |
| is made for pointers to buffers for which the length isn't |
| transmitted as part of the function call, namely strings. Strings |
| are transmitted as a pointer/length pair, both as hex values, e.g.@: |
| |
| @smallexample |
| @code{1aaf/12} |
| @end smallexample |
| |
| @noindent |
| which is a pointer to data of length 18 bytes at position 0x1aaf. |
| The length is defined as the full string length in bytes, including |
| the trailing null byte. For example, the string @code{"hello world"} |
| at address 0x123456 is transmitted as |
| |
| @smallexample |
| @code{123456/d} |
| @end smallexample |
| |
| @node Memory Transfer |
| @unnumberedsubsubsec Memory Transfer |
| @cindex memory transfer, in file-i/o protocol |
| |
| Structured data which is transferred using a memory read or write (for |
| example, a @code{struct stat}) is expected to be in a protocol-specific format |
| with all scalar multibyte datatypes being big endian. Translation to |
| this representation needs to be done both by the target before the @code{F} |
| packet is sent, and by @value{GDBN} before |
| it transfers memory to the target. Transferred pointers to structured |
| data should point to the already-coerced data at any time. |
| |
| |
| @node struct stat |
| @unnumberedsubsubsec struct stat |
| @cindex struct stat, in file-i/o protocol |
| |
| The buffer of type @code{struct stat} used by the target and @value{GDBN} |
| is defined as follows: |
| |
| @smallexample |
| struct stat @{ |
| unsigned int st_dev; /* device */ |
| unsigned int st_ino; /* inode */ |
| mode_t st_mode; /* protection */ |
| unsigned int st_nlink; /* number of hard links */ |
| unsigned int st_uid; /* user ID of owner */ |
| unsigned int st_gid; /* group ID of owner */ |
| unsigned int st_rdev; /* device type (if inode device) */ |
| unsigned long st_size; /* total size, in bytes */ |
| unsigned long st_blksize; /* blocksize for filesystem I/O */ |
| unsigned long st_blocks; /* number of blocks allocated */ |
| time_t st_atime; /* time of last access */ |
| time_t st_mtime; /* time of last modification */ |
| time_t st_ctime; /* time of last change */ |
| @}; |
| @end smallexample |
| |
| The integral datatypes conform to the definitions given in the |
| appropriate section (see @ref{Integral Datatypes}, for details) so this |
| structure is of size 64 bytes. |
| |
| The values of several fields have a restricted meaning and/or |
| range of values. |
| |
| @table @code |
| |
| @item st_dev |
| A value of 0 represents a file, 1 the console. |
| |
| @item st_ino |
| No valid meaning for the target. Transmitted unchanged. |
| |
| @item st_mode |
| Valid mode bits are described in @ref{Constants}. Any other |
| bits have currently no meaning for the target. |
| |
| @item st_uid |
| @itemx st_gid |
| @itemx st_rdev |
| No valid meaning for the target. Transmitted unchanged. |
| |
| @item st_atime |
| @itemx st_mtime |
| @itemx st_ctime |
| These values have a host and file system dependent |
| accuracy. Especially on Windows hosts, the file system may not |
| support exact timing values. |
| @end table |
| |
| The target gets a @code{struct stat} of the above representation and is |
| responsible for coercing it to the target representation before |
| continuing. |
| |
| Note that due to size differences between the host, target, and protocol |
| representations of @code{struct stat} members, these members could eventually |
| get truncated on the target. |
| |
| @node struct timeval |
| @unnumberedsubsubsec struct timeval |
| @cindex struct timeval, in file-i/o protocol |
| |
| The buffer of type @code{struct timeval} used by the File-I/O protocol |
| is defined as follows: |
| |
| @smallexample |
| struct timeval @{ |
| time_t tv_sec; /* second */ |
| long tv_usec; /* microsecond */ |
| @}; |
| @end smallexample |
| |
| The integral datatypes conform to the definitions given in the |
| appropriate section (see @ref{Integral Datatypes}, for details) so this |
| structure is of size 8 bytes. |
| |
| @node Constants |
| @subsection Constants |
| @cindex constants, in file-i/o protocol |
| |
| The following values are used for the constants inside of the |
| protocol. @value{GDBN} and target are responsible for translating these |
| values before and after the call as needed. |
| |
| @menu |
| * Open Flags:: |
| * mode_t Values:: |
| * Errno Values:: |
| * Lseek Flags:: |
| * Limits:: |
| @end menu |
| |
| @node Open Flags |
| @unnumberedsubsubsec Open Flags |
| @cindex open flags, in file-i/o protocol |
| |
| All values are given in hexadecimal representation. |
| |
| @smallexample |
| O_RDONLY 0x0 |
| O_WRONLY 0x1 |
| O_RDWR 0x2 |
| O_APPEND 0x8 |
| O_CREAT 0x200 |
| O_TRUNC 0x400 |
| O_EXCL 0x800 |
| @end smallexample |
| |
| @node mode_t Values |
| @unnumberedsubsubsec mode_t Values |
| @cindex mode_t values, in file-i/o protocol |
| |
| All values are given in octal representation. |
| |
| @smallexample |
| S_IFREG 0100000 |
| S_IFDIR 040000 |
| S_IRUSR 0400 |
| S_IWUSR 0200 |
| S_IXUSR 0100 |
| S_IRGRP 040 |
| S_IWGRP 020 |
| S_IXGRP 010 |
| S_IROTH 04 |
| S_IWOTH 02 |
| S_IXOTH 01 |
| @end smallexample |
| |
| @node Errno Values |
| @unnumberedsubsubsec Errno Values |
| @cindex errno values, in file-i/o protocol |
| |
| All values are given in decimal representation. |
| |
| @smallexample |
| EPERM 1 |
| ENOENT 2 |
| EINTR 4 |
| EBADF 9 |
| EACCES 13 |
| EFAULT 14 |
| EBUSY 16 |
| EEXIST 17 |
| ENODEV 19 |
| ENOTDIR 20 |
| EISDIR 21 |
| EINVAL 22 |
| ENFILE 23 |
| EMFILE 24 |
| EFBIG 27 |
| ENOSPC 28 |
| ESPIPE 29 |
| EROFS 30 |
| ENAMETOOLONG 91 |
| EUNKNOWN 9999 |
| @end smallexample |
| |
| @code{EUNKNOWN} is used as a fallback error value if a host system returns |
| any error value not in the list of supported error numbers. |
| |
| @node Lseek Flags |
| @unnumberedsubsubsec Lseek Flags |
| @cindex lseek flags, in file-i/o protocol |
| |
| @smallexample |
| SEEK_SET 0 |
| SEEK_CUR 1 |
| SEEK_END 2 |
| @end smallexample |
| |
| @node Limits |
| @unnumberedsubsubsec Limits |
| @cindex limits, in file-i/o protocol |
| |
| All values are given in decimal representation. |
| |
| @smallexample |
| INT_MIN -2147483648 |
| INT_MAX 2147483647 |
| UINT_MAX 4294967295 |
| LONG_MIN -9223372036854775808 |
| LONG_MAX 9223372036854775807 |
| ULONG_MAX 18446744073709551615 |
| @end smallexample |
| |
| @node File-I/O Examples |
| @subsection File-I/O Examples |
| @cindex file-i/o examples |
| |
| Example sequence of a write call, file descriptor 3, buffer is at target |
| address 0x1234, 6 bytes should be written: |
| |
| @smallexample |
| <- @code{Fwrite,3,1234,6} |
| @emph{request memory read from target} |
| -> @code{m1234,6} |
| <- XXXXXX |
| @emph{return "6 bytes written"} |
| -> @code{F6} |
| @end smallexample |
| |
| Example sequence of a read call, file descriptor 3, buffer is at target |
| address 0x1234, 6 bytes should be read: |
| |
| @smallexample |
| <- @code{Fread,3,1234,6} |
| @emph{request memory write to target} |
| -> @code{X1234,6:XXXXXX} |
| @emph{return "6 bytes read"} |
| -> @code{F6} |
| @end smallexample |
| |
| Example sequence of a read call, call fails on the host due to invalid |
| file descriptor (@code{EBADF}): |
| |
| @smallexample |
| <- @code{Fread,3,1234,6} |
| -> @code{F-1,9} |
| @end smallexample |
| |
| Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on |
| host is called: |
| |
| @smallexample |
| <- @code{Fread,3,1234,6} |
| -> @code{F-1,4,C} |
| <- @code{T02} |
| @end smallexample |
| |
| Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on |
| host is called: |
| |
| @smallexample |
| <- @code{Fread,3,1234,6} |
| -> @code{X1234,6:XXXXXX} |
| <- @code{T02} |
| @end smallexample |
| |
| @node Library List Format |
| @section Library List Format |
| @cindex library list format, remote protocol |
| |
| On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the |
| same process as your application to manage libraries. In this case, |
| @value{GDBN} can use the loader's symbol table and normal memory |
| operations to maintain a list of shared libraries. On other |
| platforms, the operating system manages loaded libraries. |
| @value{GDBN} can not retrieve the list of currently loaded libraries |
| through memory operations, so it uses the @samp{qXfer:libraries:read} |
| packet (@pxref{qXfer library list read}) instead. The remote stub |
| queries the target's operating system and reports which libraries |
| are loaded. |
| |
| The @samp{qXfer:libraries:read} packet returns an XML document which |
| lists loaded libraries and their offsets. Each library has an |
| associated name and one or more segment or section base addresses, |
| which report where the library was loaded in memory. |
| |
| For the common case of libraries that are fully linked binaries, the |
| library should have a list of segments. If the target supports |
| dynamic linking of a relocatable object file, its library XML element |
| should instead include a list of allocated sections. The segment or |
| section bases are start addresses, not relocation offsets; they do not |
| depend on the library's link-time base addresses. |
| |
| @value{GDBN} must be linked with the Expat library to support XML |
| library lists. @xref{Expat}. |
| |
| A simple memory map, with one loaded library relocated by a single |
| offset, looks like this: |
| |
| @smallexample |
| <library-list> |
| <library name="/lib/libc.so.6"> |
| <segment address="0x10000000"/> |
| </library> |
| </library-list> |
| @end smallexample |
| |
| Another simple memory map, with one loaded library with three |
| allocated sections (.text, .data, .bss), looks like this: |
| |
| @smallexample |
| <library-list> |
| <library name="sharedlib.o"> |
| <section address="0x10000000"/> |
| <section address="0x20000000"/> |
| <section address="0x30000000"/> |
| </library> |
| </library-list> |
| @end smallexample |
| |
| The format of a library list is described by this DTD: |
| |
| @smallexample |
| <!-- library-list: Root element with versioning --> |
| <!ELEMENT library-list (library)*> |
| <!ATTLIST library-list version CDATA #FIXED "1.0"> |
| <!ELEMENT library (segment*, section*)> |
| <!ATTLIST library name CDATA #REQUIRED> |
| <!ELEMENT segment EMPTY> |
| <!ATTLIST segment address CDATA #REQUIRED> |
| <!ELEMENT section EMPTY> |
| <!ATTLIST section address CDATA #REQUIRED> |
| @end smallexample |
| |
| In addition, segments and section descriptors cannot be mixed within a |
| single library element, and you must supply at least one segment or |
| section for each library. |
| |
| @node Library List Format for SVR4 Targets |
| @section Library List Format for SVR4 Targets |
| @cindex library list format, remote protocol |
| |
| On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader |
| (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of |
| shared libraries. Still a special library list provided by this packet is |
| more efficient for the @value{GDBN} remote protocol. |
| |
| The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists |
| loaded libraries and their SVR4 linker parameters. For each library on SVR4 |
| target, the following parameters are reported: |
| |
| @itemize @minus |
| @item |
| @code{name}, the absolute file name from the @code{l_name} field of |
| @code{struct link_map}. |
| @item |
| @code{lm} with address of @code{struct link_map} used for TLS |
| (Thread Local Storage) access. |
| @item |
| @code{l_addr}, the displacement as read from the field @code{l_addr} of |
| @code{struct link_map}. For prelinked libraries this is not an absolute |
| memory address. It is a displacement of absolute memory address against |
| address the file was prelinked to during the library load. |
| @item |
| @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment |
| @end itemize |
| |
| Additionally the single @code{main-lm} attribute specifies address of |
| @code{struct link_map} used for the main executable. This parameter is used |
| for TLS access and its presence is optional. |
| |
| @value{GDBN} must be linked with the Expat library to support XML |
| SVR4 library lists. @xref{Expat}. |
| |
| A simple memory map, with two loaded libraries (which do not use prelink), |
| looks like this: |
| |
| @smallexample |
| <library-list-svr4 version="1.0" main-lm="0xe4f8f8"> |
| <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000" |
| l_ld="0xe4eefc"/> |
| <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000" |
| l_ld="0x152350"/> |
| </library-list-svr> |
| @end smallexample |
| |
| The format of an SVR4 library list is described by this DTD: |
| |
| @smallexample |
| <!-- library-list-svr4: Root element with versioning --> |
| <!ELEMENT library-list-svr4 (library)*> |
| <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0"> |
| <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED> |
| <!ELEMENT library EMPTY> |
| <!ATTLIST library name CDATA #REQUIRED> |
| <!ATTLIST library lm CDATA #REQUIRED> |
| <!ATTLIST library l_addr CDATA #REQUIRED> |
| <!ATTLIST library l_ld CDATA #REQUIRED> |
| @end smallexample |
| |
| @node Memory Map Format |
| @section Memory Map Format |
| @cindex memory map format |
| |
| To be able to write into flash memory, @value{GDBN} needs to obtain a |
| memory map from the target. This section describes the format of the |
| memory map. |
| |
| The memory map is obtained using the @samp{qXfer:memory-map:read} |
| (@pxref{qXfer memory map read}) packet and is an XML document that |
| lists memory regions. |
| |
| @value{GDBN} must be linked with the Expat library to support XML |
| memory maps. @xref{Expat}. |
| |
| The top-level structure of the document is shown below: |
| |
| @smallexample |
| <?xml version="1.0"?> |
| <!DOCTYPE memory-map |
| PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN" |
| "http://sourceware.org/gdb/gdb-memory-map.dtd"> |
| <memory-map> |
| region... |
| </memory-map> |
| @end smallexample |
| |
| Each region can be either: |
| |
| @itemize |
| |
| @item |
| A region of RAM starting at @var{addr} and extending for @var{length} |
| bytes from there: |
| |
| @smallexample |
| <memory type="ram" start="@var{addr}" length="@var{length}"/> |
| @end smallexample |
| |
| |
| @item |
| A region of read-only memory: |
| |
| @smallexample |
| <memory type="rom" start="@var{addr}" length="@var{length}"/> |
| @end smallexample |
| |
| |
| @item |
| A region of flash memory, with erasure blocks @var{blocksize} |
| bytes in length: |
| |
| @smallexample |
| <memory type="flash" start="@var{addr}" length="@var{length}"> |
| <property name="blocksize">@var{blocksize}</property> |
| </memory> |
| @end smallexample |
| |
| @end itemize |
| |
| Regions must not overlap. @value{GDBN} assumes that areas of memory not covered |
| by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X} |
| packets to write to addresses in such ranges. |
| |
| The formal DTD for memory map format is given below: |
| |
| @smallexample |
| <!-- ................................................... --> |
| <!-- Memory Map XML DTD ................................ --> |
| <!-- File: memory-map.dtd .............................. --> |
| <!-- .................................... .............. --> |
| <!-- memory-map.dtd --> |
| <!-- memory-map: Root element with versioning --> |
| <!ELEMENT memory-map (memory | property)> |
| <!ATTLIST memory-map version CDATA #FIXED "1.0.0"> |
| <!ELEMENT memory (property)> |
| <!-- memory: Specifies a memory region, |
| and its type, or device. --> |
| <!ATTLIST memory type CDATA #REQUIRED |
| start CDATA #REQUIRED |
| length CDATA #REQUIRED |
| device CDATA #IMPLIED> |
| <!-- property: Generic attribute tag --> |
| <!ELEMENT property (#PCDATA | property)*> |
| <!ATTLIST property name CDATA #REQUIRED> |
| @end smallexample |
| |
| @node Thread List Format |
| @section Thread List Format |
| @cindex thread list format |
| |
| To efficiently update the list of threads and their attributes, |
| @value{GDBN} issues the @samp{qXfer:threads:read} packet |
| (@pxref{qXfer threads read}) and obtains the XML document with |
| the following structure: |
| |
| @smallexample |
| <?xml version="1.0"?> |
| <threads> |
| <thread id="id" core="0"> |
| ... description ... |
| </thread> |
| </threads> |
| @end smallexample |
| |
| Each @samp{thread} element must have the @samp{id} attribute that |
| identifies the thread (@pxref{thread-id syntax}). The |
| @samp{core} attribute, if present, specifies which processor core |
| the thread was last executing on. The content of the of @samp{thread} |
| element is interpreted as human-readable auxilliary information. |
| |
| @node Traceframe Info Format |
| @section Traceframe Info Format |
| @cindex traceframe info format |
| |
| To be able to know which objects in the inferior can be examined when |
| inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of |
| memory ranges, registers and trace state variables that have been |
| collected in a traceframe. |
| |
| This list is obtained using the @samp{qXfer:traceframe-info:read} |
| (@pxref{qXfer traceframe info read}) packet and is an XML document. |
| |
| @value{GDBN} must be linked with the Expat library to support XML |
| traceframe info discovery. @xref{Expat}. |
| |
| The top-level structure of the document is shown below: |
| |
| @smallexample |
| <?xml version="1.0"?> |
| <!DOCTYPE traceframe-info |
| PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN" |
| "http://sourceware.org/gdb/gdb-traceframe-info.dtd"> |
| <traceframe-info> |
| block... |
| </traceframe-info> |
| @end smallexample |
| |
| Each traceframe block can be either: |
| |
| @itemize |
| |
| @item |
| A region of collected memory starting at @var{addr} and extending for |
| @var{length} bytes from there: |
| |
| @smallexample |
| <memory start="@var{addr}" length="@var{length}"/> |
| @end smallexample |
| |
| @end itemize |
| |
| The formal DTD for the traceframe info format is given below: |
| |
| @smallexample |
| <!ELEMENT traceframe-info (memory)* > |
| <!ATTLIST traceframe-info version CDATA #FIXED "1.0"> |
| |
| <!ELEMENT memory EMPTY> |
| <!ATTLIST memory start CDATA #REQUIRED |
| length CDATA #REQUIRED> |
| @end smallexample |
| |
| @include agentexpr.texi |
| |
| @node Target Descriptions |
| @appendix Target Descriptions |
| @cindex target descriptions |
| |
| One of the challenges of using @value{GDBN} to debug embedded systems |
| is that there are so many minor variants of each processor |
| architecture in use. It is common practice for vendors to start with |
| a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example --- |
| and then make changes to adapt it to a particular market niche. Some |
| architectures have hundreds of variants, available from dozens of |
| vendors. This leads to a number of problems: |
| |
| @itemize @bullet |
| @item |
| With so many different customized processors, it is difficult for |
| the @value{GDBN} maintainers to keep up with the changes. |
| @item |
| Since individual variants may have short lifetimes or limited |
| audiences, it may not be worthwhile to carry information about every |
| variant in the @value{GDBN} source tree. |
| @item |
| When @value{GDBN} does support the architecture of the embedded system |
| at hand, the task of finding the correct architecture name to give the |
| @command{set architecture} command can be error-prone. |
| @end itemize |
| |
| To address these problems, the @value{GDBN} remote protocol allows a |
| target system to not only identify itself to @value{GDBN}, but to |
| actually describe its own features. This lets @value{GDBN} support |
| processor variants it has never seen before --- to the extent that the |
| descriptions are accurate, and that @value{GDBN} understands them. |
| |
| @value{GDBN} must be linked with the Expat library to support XML |
| target descriptions. @xref{Expat}. |
| |
| @menu |
| * Retrieving Descriptions:: How descriptions are fetched from a target. |
| * Target Description Format:: The contents of a target description. |
| * Predefined Target Types:: Standard types available for target |
| descriptions. |
| * Standard Target Features:: Features @value{GDBN} knows about. |
| @end menu |
| |
| @node Retrieving Descriptions |
| @section Retrieving Descriptions |
| |
| Target descriptions can be read from the target automatically, or |
| specified by the user manually. The default behavior is to read the |
| description from the target. @value{GDBN} retrieves it via the remote |
| protocol using @samp{qXfer} requests (@pxref{General Query Packets, |
| qXfer}). The @var{annex} in the @samp{qXfer} packet will be |
| @samp{target.xml}. The contents of the @samp{target.xml} annex are an |
| XML document, of the form described in @ref{Target Description |
| Format}. |
| |
| Alternatively, you can specify a file to read for the target description. |
| If a file is set, the target will not be queried. The commands to |
| specify a file are: |
| |
| @table @code |
| @cindex set tdesc filename |
| @item set tdesc filename @var{path} |
| Read the target description from @var{path}. |
| |
| @cindex unset tdesc filename |
| @item unset tdesc filename |
| Do not read the XML target description from a file. @value{GDBN} |
| will use the description supplied by the current target. |
| |
| @cindex show tdesc filename |
| @item show tdesc filename |
| Show the filename to read for a target description, if any. |
| @end table |
| |
| |
| @node Target Description Format |
| @section Target Description Format |
| @cindex target descriptions, XML format |
| |
| A target description annex is an @uref{http://www.w3.org/XML/, XML} |
| document which complies with the Document Type Definition provided in |
| the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This |
| means you can use generally available tools like @command{xmllint} to |
| check that your feature descriptions are well-formed and valid. |
| However, to help people unfamiliar with XML write descriptions for |
| their targets, we also describe the grammar here. |
| |
| Target descriptions can identify the architecture of the remote target |
| and (for some architectures) provide information about custom register |
| sets. They can also identify the OS ABI of the remote target. |
| @value{GDBN} can use this information to autoconfigure for your |
| target, or to warn you if you connect to an unsupported target. |
| |
| Here is a simple target description: |
| |
| @smallexample |
| <target version="1.0"> |
| <architecture>i386:x86-64</architecture> |
| </target> |
| @end smallexample |
| |
| @noindent |
| This minimal description only says that the target uses |
| the x86-64 architecture. |
| |
| A target description has the following overall form, with [ ] marking |
| optional elements and @dots{} marking repeatable elements. The elements |
| are explained further below. |
| |
| @smallexample |
| <?xml version="1.0"?> |
| <!DOCTYPE target SYSTEM "gdb-target.dtd"> |
| <target version="1.0"> |
| @r{[}@var{architecture}@r{]} |
| @r{[}@var{osabi}@r{]} |
| @r{[}@var{compatible}@r{]} |
| @r{[}@var{feature}@dots{}@r{]} |
| </target> |
| @end smallexample |
| |
| @noindent |
| The description is generally insensitive to whitespace and line |
| breaks, under the usual common-sense rules. The XML version |
| declaration and document type declaration can generally be omitted |
| (@value{GDBN} does not require them), but specifying them may be |
| useful for XML validation tools. The @samp{version} attribute for |
| @samp{<target>} may also be omitted, but we recommend |
| including it; if future versions of @value{GDBN} use an incompatible |
| revision of @file{gdb-target.dtd}, they will detect and report |
| the version mismatch. |
| |
| @subsection Inclusion |
| @cindex target descriptions, inclusion |
| @cindex XInclude |
| @ifnotinfo |
| @cindex <xi:include> |
| @end ifnotinfo |
| |
| It can sometimes be valuable to split a target description up into |
| several different annexes, either for organizational purposes, or to |
| share files between different possible target descriptions. You can |
| divide a description into multiple files by replacing any element of |
| the target description with an inclusion directive of the form: |
| |
| @smallexample |
| <xi:include href="@var{document}"/> |
| @end smallexample |
| |
| @noindent |
| When @value{GDBN} encounters an element of this form, it will retrieve |
| the named XML @var{document}, and replace the inclusion directive with |
| the contents of that document. If the current description was read |
| using @samp{qXfer}, then so will be the included document; |
| @var{document} will be interpreted as the name of an annex. If the |
| current description was read from a file, @value{GDBN} will look for |
| @var{document} as a file in the same directory where it found the |
| original description. |
| |
| @subsection Architecture |
| @cindex <architecture> |
| |
| An @samp{<architecture>} element has this form: |
| |
| @smallexample |
| <architecture>@var{arch}</architecture> |
| @end smallexample |
| |
| @var{arch} is one of the architectures from the set accepted by |
| @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}). |
| |
| @subsection OS ABI |
| @cindex @code{<osabi>} |
| |
| This optional field was introduced in @value{GDBN} version 7.0. |
| Previous versions of @value{GDBN} ignore it. |
| |
| An @samp{<osabi>} element has this form: |
| |
| @smallexample |
| <osabi>@var{abi-name}</osabi> |
| @end smallexample |
| |
| @var{abi-name} is an OS ABI name from the same selection accepted by |
| @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}). |
| |
| @subsection Compatible Architecture |
| @cindex @code{<compatible>} |
| |
| This optional field was introduced in @value{GDBN} version 7.0. |
| Previous versions of @value{GDBN} ignore it. |
| |
| A @samp{<compatible>} element has this form: |
| |
| @smallexample |
| <compatible>@var{arch}</compatible> |
| @end smallexample |
| |
| @var{arch} is one of the architectures from the set accepted by |
| @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}). |
| |
| A @samp{<compatible>} element is used to specify that the target |
| is able to run binaries in some other than the main target architecture |
| given by the @samp{<architecture>} element. For example, on the |
| Cell Broadband Engine, the main architecture is @code{powerpc:common} |
| or @code{powerpc:common64}, but the system is able to run binaries |
| in the @code{spu} architecture as well. The way to describe this |
| capability with @samp{<compatible>} is as follows: |
| |
| @smallexample |
| <architecture>powerpc:common</architecture> |
| <compatible>spu</compatible> |
| @end smallexample |
| |
| @subsection Features |
| @cindex <feature> |
| |
| Each @samp{<feature>} describes some logical portion of the target |
| system. Features are currently used to describe available CPU |
| registers and the types of their contents. A @samp{<feature>} element |
| has this form: |
| |
| @smallexample |
| <feature name="@var{name}"> |
| @r{[}@var{type}@dots{}@r{]} |
| @var{reg}@dots{} |
| </feature> |
| @end smallexample |
| |
| @noindent |
| Each feature's name should be unique within the description. The name |
| of a feature does not matter unless @value{GDBN} has some special |
| knowledge of the contents of that feature; if it does, the feature |
| should have its standard name. @xref{Standard Target Features}. |
| |
| @subsection Types |
| |
| Any register's value is a collection of bits which @value{GDBN} must |
| interpret. The default interpretation is a two's complement integer, |
| but other types can be requested by name in the register description. |
| Some predefined types are provided by @value{GDBN} (@pxref{Predefined |
| Target Types}), and the description can define additional composite types. |
| |
| Each type element must have an @samp{id} attribute, which gives |
| a unique (within the containing @samp{<feature>}) name to the type. |
| Types must be defined before they are used. |
| |
| @cindex <vector> |
| Some targets offer vector registers, which can be treated as arrays |
| of scalar elements. These types are written as @samp{<vector>} elements, |
| specifying the array element type, @var{type}, and the number of elements, |
| @var{count}: |
| |
| @smallexample |
| <vector id="@var{id}" type="@var{type}" count="@var{count}"/> |
| @end smallexample |
| |
| @cindex <union> |
| If a register's value is usefully viewed in multiple ways, define it |
| with a union type containing the useful representations. The |
| @samp{<union>} element contains one or more @samp{<field>} elements, |
| each of which has a @var{name} and a @var{type}: |
| |
| @smallexample |
| <union id="@var{id}"> |
| <field name="@var{name}" type="@var{type}"/> |
| @dots{} |
| </union> |
| @end smallexample |
| |
| @cindex <struct> |
| If a register's value is composed from several separate values, define |
| it with a structure type. There are two forms of the @samp{<struct>} |
| element; a @samp{<struct>} element must either contain only bitfields |
| or contain no bitfields. If the structure contains only bitfields, |
| its total size in bytes must be specified, each bitfield must have an |
| explicit start and end, and bitfields are automatically assigned an |
| integer type. The field's @var{start} should be less than or |
| equal to its @var{end}, and zero represents the least significant bit. |
| |
| @smallexample |
| <struct id="@var{id}" size="@var{size}"> |
| <field name="@var{name}" start="@var{start}" end="@var{end}"/> |
| @dots{} |
| </struct> |
| @end smallexample |
| |
| If the structure contains no bitfields, then each field has an |
| explicit type, and no implicit padding is added. |
| |
| @smallexample |
| <struct id="@var{id}"> |
| <field name="@var{name}" type="@var{type}"/> |
| @dots{} |
| </struct> |
| @end smallexample |
| |
| @cindex <flags> |
| If a register's value is a series of single-bit flags, define it with |
| a flags type. The @samp{<flags>} element has an explicit @var{size} |
| and contains one or more @samp{<field>} elements. Each field has a |
| @var{name}, a @var{start}, and an @var{end}. Only single-bit flags |
| are supported. |
| |
| @smallexample |
| <flags id="@var{id}" size="@var{size}"> |
| <field name="@var{name}" start="@var{start}" end="@var{end}"/> |
| @dots{} |
| </flags> |
| @end smallexample |
| |
| @subsection Registers |
| @cindex <reg> |
| |
| Each register is represented as an element with this form: |
| |
| @smallexample |
| <reg name="@var{name}" |
| bitsize="@var{size}" |
| @r{[}regnum="@var{num}"@r{]} |
| @r{[}save-restore="@var{save-restore}"@r{]} |
| @r{[}type="@var{type}"@r{]} |
| @r{[}group="@var{group}"@r{]}/> |
| @end smallexample |
| |
| @noindent |
| The components are as follows: |
| |
| @table @var |
| |
| @item name |
| The register's name; it must be unique within the target description. |
| |
| @item bitsize |
| The register's size, in bits. |
| |
| @item regnum |
| The register's number. If omitted, a register's number is one greater |
| than that of the previous register (either in the current feature or in |
| a preceding feature); the first register in the target description |
| defaults to zero. This register number is used to read or write |
| the register; e.g.@: it is used in the remote @code{p} and @code{P} |
| packets, and registers appear in the @code{g} and @code{G} packets |
| in order of increasing register number. |
| |
| @item save-restore |
| Whether the register should be preserved across inferior function |
| calls; this must be either @code{yes} or @code{no}. The default is |
| @code{yes}, which is appropriate for most registers except for |
| some system control registers; this is not related to the target's |
| ABI. |
| |
| @item type |
| The type of the register. @var{type} may be a predefined type, a type |
| defined in the current feature, or one of the special types @code{int} |
| and @code{float}. @code{int} is an integer type of the correct size |
| for @var{bitsize}, and @code{float} is a floating point type (in the |
| architecture's normal floating point format) of the correct size for |
| @var{bitsize}. The default is @code{int}. |
| |
| @item group |
| The register group to which this register belongs. @var{group} must |
| be either @code{general}, @code{float}, or @code{vector}. If no |
| @var{group} is specified, @value{GDBN} will not display the register |
| in @code{info registers}. |
| |
| @end table |
| |
| @node Predefined Target Types |
| @section Predefined Target Types |
| @cindex target descriptions, predefined types |
| |
| Type definitions in the self-description can build up composite types |
| from basic building blocks, but can not define fundamental types. Instead, |
| standard identifiers are provided by @value{GDBN} for the fundamental |
| types. The currently supported types are: |
| |
| @table @code |
| |
| @item int8 |
| @itemx int16 |
| @itemx int32 |
| @itemx int64 |
| @itemx int128 |
| Signed integer types holding the specified number of bits. |
| |
| @item uint8 |
| @itemx uint16 |
| @itemx uint32 |
| @itemx uint64 |
| @itemx uint128 |
| Unsigned integer types holding the specified number of bits. |
| |
| @item code_ptr |
| @itemx data_ptr |
| Pointers to unspecified code and data. The program counter and |
| any dedicated return address register may be marked as code |
| pointers; printing a code pointer converts it into a symbolic |
| address. The stack pointer and any dedicated address registers |
| may be marked as data pointers. |
| |
| @item ieee_single |
| Single precision IEEE floating point. |
| |
| @item ieee_double |
| Double precision IEEE floating point. |
| |
| @item arm_fpa_ext |
| The 12-byte extended precision format used by ARM FPA registers. |
| |
| @item i387_ext |
| The 10-byte extended precision format used by x87 registers. |
| |
| @item i386_eflags |
| 32bit @sc{eflags} register used by x86. |
| |
| @item i386_mxcsr |
| 32bit @sc{mxcsr} register used by x86. |
| |
| @end table |
| |
| @node Standard Target Features |
| @section Standard Target Features |
| @cindex target descriptions, standard features |
| |
| A target description must contain either no registers or all the |
| target's registers. If the description contains no registers, then |
| @value{GDBN} will assume a default register layout, selected based on |
| the architecture. If the description contains any registers, the |
| default layout will not be used; the standard registers must be |
| described in the target description, in such a way that @value{GDBN} |
| can recognize them. |
| |
| This is accomplished by giving specific names to feature elements |
| which contain standard registers. @value{GDBN} will look for features |
| with those names and verify that they contain the expected registers; |
| if any known feature is missing required registers, or if any required |
| feature is missing, @value{GDBN} will reject the target |
| description. You can add additional registers to any of the |
| standard features --- @value{GDBN} will display them just as if |
| they were added to an unrecognized feature. |
| |
| This section lists the known features and their expected contents. |
| Sample XML documents for these features are included in the |
| @value{GDBN} source tree, in the directory @file{gdb/features}. |
| |
| Names recognized by @value{GDBN} should include the name of the |
| company or organization which selected the name, and the overall |
| architecture to which the feature applies; so e.g.@: the feature |
| containing ARM core registers is named @samp{org.gnu.gdb.arm.core}. |
| |
| The names of registers are not case sensitive for the purpose |
| of recognizing standard features, but @value{GDBN} will only display |
| registers using the capitalization used in the description. |
| |
| @menu |
| * ARM Features:: |
| * i386 Features:: |
| * MIPS Features:: |
| * M68K Features:: |
| * PowerPC Features:: |
| * TIC6x Features:: |
| @end menu |
| |
| |
| @node ARM Features |
| @subsection ARM Features |
| @cindex target descriptions, ARM features |
| |
| The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile |
| ARM targets. |
| It should contain registers @samp{r0} through @samp{r13}, @samp{sp}, |
| @samp{lr}, @samp{pc}, and @samp{cpsr}. |
| |
| For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core} |
| feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain |
| registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc}, |
| and @samp{xpsr}. |
| |
| The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it |
| should contain registers @samp{f0} through @samp{f7} and @samp{fps}. |
| |
| The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present, |
| it should contain at least registers @samp{wR0} through @samp{wR15} and |
| @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon}, |
| @samp{wCSSF}, and @samp{wCASF} registers are optional. |
| |
| The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it |
| should contain at least registers @samp{d0} through @samp{d15}. If |
| they are present, @samp{d16} through @samp{d31} should also be included. |
| @value{GDBN} will synthesize the single-precision registers from |
| halves of the double-precision registers. |
| |
| The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not |
| need to contain registers; it instructs @value{GDBN} to display the |
| VFP double-precision registers as vectors and to synthesize the |
| quad-precision registers from pairs of double-precision registers. |
| If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also |
| be present and include 32 double-precision registers. |
| |
| @node i386 Features |
| @subsection i386 Features |
| @cindex target descriptions, i386 features |
| |
| The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64 |
| targets. It should describe the following registers: |
| |
| @itemize @minus |
| @item |
| @samp{eax} through @samp{edi} plus @samp{eip} for i386 |
| @item |
| @samp{rax} through @samp{r15} plus @samp{rip} for amd64 |
| @item |
| @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es}, |
| @samp{fs}, @samp{gs} |
| @item |
| @samp{st0} through @samp{st7} |
| @item |
| @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff}, |
| @samp{foseg}, @samp{fooff} and @samp{fop} |
| @end itemize |
| |
| The register sets may be different, depending on the target. |
| |
| The @samp{org.gnu.gdb.i386.sse} feature is optional. It should |
| describe registers: |
| |
| @itemize @minus |
| @item |
| @samp{xmm0} through @samp{xmm7} for i386 |
| @item |
| @samp{xmm0} through @samp{xmm15} for amd64 |
| @item |
| @samp{mxcsr} |
| @end itemize |
| |
| The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the |
| @samp{org.gnu.gdb.i386.sse} feature. It should |
| describe the upper 128 bits of @sc{ymm} registers: |
| |
| @itemize @minus |
| @item |
| @samp{ymm0h} through @samp{ymm7h} for i386 |
| @item |
| @samp{ymm0h} through @samp{ymm15h} for amd64 |
| @end itemize |
| |
| The @samp{org.gnu.gdb.i386.linux} feature is optional. It should |
| describe a single register, @samp{orig_eax}. |
| |
| @node MIPS Features |
| @subsection @acronym{MIPS} Features |
| @cindex target descriptions, @acronym{MIPS} features |
| |
| The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets. |
| It should contain registers @samp{r0} through @samp{r31}, @samp{lo}, |
| @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending |
| on the target. |
| |
| The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should |
| contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause} |
| registers. They may be 32-bit or 64-bit depending on the target. |
| |
| The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though |
| it may be optional in a future version of @value{GDBN}. It should |
| contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and |
| @samp{fir}. They may be 32-bit or 64-bit depending on the target. |
| |
| The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should |
| contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through |
| @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should |
| be 32-bit and the rest may be 32-bit or 64-bit depending on the target. |
| |
| The @samp{org.gnu.gdb.mips.linux} feature is optional. It should |
| contain a single register, @samp{restart}, which is used by the |
| Linux kernel to control restartable syscalls. |
| |
| @node M68K Features |
| @subsection M68K Features |
| @cindex target descriptions, M68K features |
| |
| @table @code |
| @item @samp{org.gnu.gdb.m68k.core} |
| @itemx @samp{org.gnu.gdb.coldfire.core} |
| @itemx @samp{org.gnu.gdb.fido.core} |
| One of those features must be always present. |
| The feature that is present determines which flavor of m68k is |
| used. The feature that is present should contain registers |
| @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp}, |
| @samp{sp}, @samp{ps} and @samp{pc}. |
| |
| @item @samp{org.gnu.gdb.coldfire.fp} |
| This feature is optional. If present, it should contain registers |
| @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and |
| @samp{fpiaddr}. |
| @end table |
| |
| @node PowerPC Features |
| @subsection PowerPC Features |
| @cindex target descriptions, PowerPC features |
| |
| The @samp{org.gnu.gdb.power.core} feature is required for PowerPC |
| targets. It should contain registers @samp{r0} through @samp{r31}, |
| @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and |
| @samp{xer}. They may be 32-bit or 64-bit depending on the target. |
| |
| The @samp{org.gnu.gdb.power.fpu} feature is optional. It should |
| contain registers @samp{f0} through @samp{f31} and @samp{fpscr}. |
| |
| The @samp{org.gnu.gdb.power.altivec} feature is optional. It should |
| contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, |
| and @samp{vrsave}. |
| |
| The @samp{org.gnu.gdb.power.vsx} feature is optional. It should |
| contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} |
| will combine these registers with the floating point registers |
| (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0} |
| through @samp{vr31}) to present the 128-bit wide registers @samp{vs0} |
| through @samp{vs63}, the set of vector registers for POWER7. |
| |
| The @samp{org.gnu.gdb.power.spe} feature is optional. It should |
| contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and |
| @samp{spefscr}. SPE targets should provide 32-bit registers in |
| @samp{org.gnu.gdb.power.core} and provide the upper halves in |
| @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine |
| these to present registers @samp{ev0} through @samp{ev31} to the |
| user. |
| |
| @node TIC6x Features |
| @subsection TMS320C6x Features |
| @cindex target descriptions, TIC6x features |
| @cindex target descriptions, TMS320C6x features |
| The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x |
| targets. It should contain registers @samp{A0} through @samp{A15}, |
| registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}. |
| |
| The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should |
| contain registers @samp{A16} through @samp{A31} and @samp{B16} |
| through @samp{B31}. |
| |
| The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should |
| contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}. |
| |
| @node Operating System Information |
| @appendix Operating System Information |
| @cindex operating system information |
| |
| @menu |
| * Process list:: |
| @end menu |
| |
| Users of @value{GDBN} often wish to obtain information about the state of |
| the operating system running on the target---for example the list of |
| processes, or the list of open files. This section describes the |
| mechanism that makes it possible. This mechanism is similar to the |
| target features mechanism (@pxref{Target Descriptions}), but focuses |
| on a different aspect of target. |
| |
| Operating system information is retrived from the target via the |
| remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata |
| read}). The object name in the request should be @samp{osdata}, and |
| the @var{annex} identifies the data to be fetched. |
| |
| @node Process list |
| @appendixsection Process list |
| @cindex operating system information, process list |
| |
| When requesting the process list, the @var{annex} field in the |
| @samp{qXfer} request should be @samp{processes}. The returned data is |
| an XML document. The formal syntax of this document is defined in |
| @file{gdb/features/osdata.dtd}. |
| |
| An example document is: |
| |
| @smallexample |
| <?xml version="1.0"?> |
| <!DOCTYPE target SYSTEM "osdata.dtd"> |
| <osdata type="processes"> |
| <item> |
| <column name="pid">1</column> |
| <column name="user">root</column> |
| <column name="command">/sbin/init</column> |
| <column name="cores">1,2,3</column> |
| </item> |
| </osdata> |
| @end smallexample |
| |
| Each item should include a column whose name is @samp{pid}. The value |
| of that column should identify the process on the target. The |
| @samp{user} and @samp{command} columns are optional, and will be |
| displayed by @value{GDBN}. The @samp{cores} column, if present, |
| should contain a comma-separated list of cores that this process |
| is running on. Target may provide additional columns, |
| which @value{GDBN} currently ignores. |
| |
| @node Trace File Format |
| @appendix Trace File Format |
| @cindex trace file format |
| |
| The trace file comes in three parts: a header, a textual description |
| section, and a trace frame section with binary data. |
| |
| The header has the form @code{\x7fTRACE0\n}. The first byte is |
| @code{0x7f} so as to indicate that the file contains binary data, |
| while the @code{0} is a version number that may have different values |
| in the future. |
| |
| The description section consists of multiple lines of @sc{ascii} text |
| separated by newline characters (@code{0xa}). The lines may include a |
| variety of optional descriptive or context-setting information, such |
| as tracepoint definitions or register set size. @value{GDBN} will |
| ignore any line that it does not recognize. An empty line marks the end |
| of this section. |
| |
| @c FIXME add some specific types of data |
| |
| The trace frame section consists of a number of consecutive frames. |
| Each frame begins with a two-byte tracepoint number, followed by a |
| four-byte size giving the amount of data in the frame. The data in |
| the frame consists of a number of blocks, each introduced by a |
| character indicating its type (at least register, memory, and trace |
| state variable). The data in this section is raw binary, not a |
| hexadecimal or other encoding; its endianness matches the target's |
| endianness. |
| |
| @c FIXME bi-arch may require endianness/arch info in description section |
| |
| @table @code |
| @item R @var{bytes} |
| Register block. The number and ordering of bytes matches that of a |
| @code{g} packet in the remote protocol. Note that these are the |
| actual bytes, in target order and @value{GDBN} register order, not a |
| hexadecimal encoding. |
| |
| @item M @var{address} @var{length} @var{bytes}... |
| Memory block. This is a contiguous block of memory, at the 8-byte |
| address @var{address}, with a 2-byte length @var{length}, followed by |
| @var{length} bytes. |
| |
| @item V @var{number} @var{value} |
| Trace state variable block. This records the 8-byte signed value |
| @var{value} of trace state variable numbered @var{number}. |
| |
| @end table |
| |
| Future enhancements of the trace file format may include additional types |
| of blocks. |
| |
| @node Index Section Format |
| @appendix @code{.gdb_index} section format |
| @cindex .gdb_index section format |
| @cindex index section format |
| |
| This section documents the index section that is created by @code{save |
| gdb-index} (@pxref{Index Files}). The index section is |
| DWARF-specific; some knowledge of DWARF is assumed in this |
| description. |
| |
| The mapped index file format is designed to be directly |
| @code{mmap}able on any architecture. In most cases, a datum is |
| represented using a little-endian 32-bit integer value, called an |
| @code{offset_type}. Big endian machines must byte-swap the values |
| before using them. Exceptions to this rule are noted. The data is |
| laid out such that alignment is always respected. |
| |
| A mapped index consists of several areas, laid out in order. |
| |
| @enumerate |
| @item |
| The file header. This is a sequence of values, of @code{offset_type} |
| unless otherwise noted: |
| |
| @enumerate |
| @item |
| The version number, currently 7. Versions 1, 2 and 3 are obsolete. |
| Version 4 uses a different hashing function from versions 5 and 6. |
| Version 6 includes symbols for inlined functions, whereas versions 4 |
| and 5 do not. Version 7 adds attributes to the CU indices in the |
| symbol table. @value{GDBN} will only read version 4, 5, or 6 indices |
| by specifying @code{set use-deprecated-index-sections on}. |
| |
| @item |
| The offset, from the start of the file, of the CU list. |
| |
| @item |
| The offset, from the start of the file, of the types CU list. Note |
| that this area can be empty, in which case this offset will be equal |
| to the next offset. |
| |
| @item |
| The offset, from the start of the file, of the address area. |
| |
| @item |
| The offset, from the start of the file, of the symbol table. |
| |
| @item |
| The offset, from the start of the file, of the constant pool. |
| @end enumerate |
| |
| @item |
| The CU list. This is a sequence of pairs of 64-bit little-endian |
| values, sorted by the CU offset. The first element in each pair is |
| the offset of a CU in the @code{.debug_info} section. The second |
| element in each pair is the length of that CU. References to a CU |
| elsewhere in the map are done using a CU index, which is just the |
| 0-based index into this table. Note that if there are type CUs, then |
| conceptually CUs and type CUs form a single list for the purposes of |
| CU indices. |
| |
| @item |
| The types CU list. This is a sequence of triplets of 64-bit |
| little-endian values. In a triplet, the first value is the CU offset, |
| the second value is the type offset in the CU, and the third value is |
| the type signature. The types CU list is not sorted. |
| |
| @item |
| The address area. The address area consists of a sequence of address |
| entries. Each address entry has three elements: |
| |
| @enumerate |
| @item |
| The low address. This is a 64-bit little-endian value. |
| |
| @item |
| The high address. This is a 64-bit little-endian value. Like |
| @code{DW_AT_high_pc}, the value is one byte beyond the end. |
| |
| @item |
| The CU index. This is an @code{offset_type} value. |
| @end enumerate |
| |
| @item |
| The symbol table. This is an open-addressed hash table. The size of |
| the hash table is always a power of 2. |
| |
| Each slot in the hash table consists of a pair of @code{offset_type} |
| values. The first value is the offset of the symbol's name in the |
| constant pool. The second value is the offset of the CU vector in the |
| constant pool. |
| |
| If both values are 0, then this slot in the hash table is empty. This |
| is ok because while 0 is a valid constant pool index, it cannot be a |
| valid index for both a string and a CU vector. |
| |
| The hash value for a table entry is computed by applying an |
| iterative hash function to the symbol's name. Starting with an |
| initial value of @code{r = 0}, each (unsigned) character @samp{c} in |
| the string is incorporated into the hash using the formula depending on the |
| index version: |
| |
| @table @asis |
| @item Version 4 |
| The formula is @code{r = r * 67 + c - 113}. |
| |
| @item Versions 5 to 7 |
| The formula is @code{r = r * 67 + tolower (c) - 113}. |
| @end table |
| |
| The terminating @samp{\0} is not incorporated into the hash. |
| |
| The step size used in the hash table is computed via |
| @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash |
| value, and @samp{size} is the size of the hash table. The step size |
| is used to find the next candidate slot when handling a hash |
| collision. |
| |
| The names of C@t{++} symbols in the hash table are canonicalized. We |
| don't currently have a simple description of the canonicalization |
| algorithm; if you intend to create new index sections, you must read |
| the code. |
| |
| @item |
| The constant pool. This is simply a bunch of bytes. It is organized |
| so that alignment is correct: CU vectors are stored first, followed by |
| strings. |
| |
| A CU vector in the constant pool is a sequence of @code{offset_type} |
| values. The first value is the number of CU indices in the vector. |
| Each subsequent value is the index and symbol attributes of a CU in |
| the CU list. This element in the hash table is used to indicate which |
| CUs define the symbol and how the symbol is used. |
| See below for the format of each CU index+attributes entry. |
| |
| A string in the constant pool is zero-terminated. |
| @end enumerate |
| |
| Attributes were added to CU index values in @code{.gdb_index} version 7. |
| If a symbol has multiple uses within a CU then there is one |
| CU index+attributes value for each use. |
| |
| The format of each CU index+attributes entry is as follows |
| (bit 0 = LSB): |
| |
| @table @asis |
| |
| @item Bits 0-23 |
| This is the index of the CU in the CU list. |
| @item Bits 24-27 |
| These bits are reserved for future purposes and must be zero. |
| @item Bits 28-30 |
| The kind of the symbol in the CU. |
| |
| @table @asis |
| @item 0 |
| This value is reserved and should not be used. |
| By reserving zero the full @code{offset_type} value is backwards compatible |
| with previous versions of the index. |
| @item 1 |
| The symbol is a type. |
| @item 2 |
| The symbol is a variable or an enum value. |
| @item 3 |
| The symbol is a function. |
| @item 4 |
| Any other kind of symbol. |
| @item 5,6,7 |
| These values are reserved. |
| @end table |
| |
| @item Bit 31 |
| This bit is zero if the value is global and one if it is static. |
| |
| The determination of whether a symbol is global or static is complicated. |
| The authorative reference is the file @file{dwarf2read.c} in |
| @value{GDBN} sources. |
| |
| @end table |
| |
| This pseudo-code describes the computation of a symbol's kind and |
| global/static attributes in the index. |
| |
| @smallexample |
| is_external = get_attribute (die, DW_AT_external); |
| language = get_attribute (cu_die, DW_AT_language); |
| switch (die->tag) |
| @{ |
| case DW_TAG_typedef: |
| case DW_TAG_base_type: |
| case DW_TAG_subrange_type: |
| kind = TYPE; |
| is_static = 1; |
| break; |
| case DW_TAG_enumerator: |
| kind = VARIABLE; |
| is_static = (language != CPLUS && language != JAVA); |
| break; |
| case DW_TAG_subprogram: |
| kind = FUNCTION; |
| is_static = ! (is_external || language == ADA); |
| break; |
| case DW_TAG_constant: |
| kind = VARIABLE; |
| is_static = ! is_external; |
| break; |
| case DW_TAG_variable: |
| kind = VARIABLE; |
| is_static = ! is_external; |
| break; |
| case DW_TAG_namespace: |
| kind = TYPE; |
| is_static = 0; |
| break; |
| case DW_TAG_class_type: |
| case DW_TAG_interface_type: |
| case DW_TAG_structure_type: |
| case DW_TAG_union_type: |
| case DW_TAG_enumeration_type: |
| kind = TYPE; |
| is_static = (language != CPLUS && language != JAVA); |
| break; |
| default: |
| assert (0); |
| @} |
| @end smallexample |
| |
| @include gpl.texi |
| |
| @node GNU Free Documentation License |
| @appendix GNU Free Documentation License |
| @include fdl.texi |
| |
| @node Concept Index |
| @unnumbered Concept Index |
| |
| @printindex cp |
| |
| @node Command and Variable Index |
| @unnumbered Command, Variable, and Function Index |
| |
| @printindex fn |
| |
| @tex |
| % I think something like @@colophon should be in texinfo. In the |
| % meantime: |
| \long\def\colophon{\hbox to0pt{}\vfill |
| \centerline{The body of this manual is set in} |
| \centerline{\fontname\tenrm,} |
| \centerline{with headings in {\bf\fontname\tenbf}} |
| \centerline{and examples in {\tt\fontname\tentt}.} |
| \centerline{{\it\fontname\tenit\/},} |
| \centerline{{\bf\fontname\tenbf}, and} |
| \centerline{{\sl\fontname\tensl\/}} |
| \centerline{are used for emphasis.}\vfill} |
| \page\colophon |
| % Blame: doc@@cygnus.com, 1991. |
| @end tex |
| |
| @bye |