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| <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" /> |
| <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++" /> |
| <meta name="DESCRIPTION" content="Configuration options for libstdc++-v3." /> |
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| |
| <h1 class="centered"><a name="top">Interesting <code>configure</code> |
| options</a></h1> |
| |
| <p class="fineprint"><em> |
| The latest version of this document is always available at |
| <a href="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html"> |
| http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</a>. |
| </em></p> |
| |
| <p><em> |
| To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>. |
| </em></p> |
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| <!-- ####################################################### --> |
| <hr /> |
| <p>Here are some of the non-obvious options to libstdc++'s configure. |
| Keep in mind that |
| <!-- This SECnn should be the "Choosing Package Options" section. --> |
| <a href="http://www.gnu.org/software/autoconf/manual/autoconf-2.57/html_node/autoconf_131.html#SEC131">they |
| all have opposite forms as well</a> |
| (enable/disable and with/without). The defaults are for <strong>current |
| development sources</strong>, which may be different than those for |
| released versions. |
| </p> |
| <p>The canonical way to find out the configure options that are |
| available for a given set of libstdc++ sources is to go to the |
| source directory and then type:<code> ./configure --help</code> |
| </p> |
| |
| <dl> |
| <dt><code>--enable-multilib </code>[default]</dt> |
| <dd><p>This is part of the generic multilib support for building cross |
| compilers. As such, targets like "powerpc-elf" will have |
| libstdc++ built many different ways: "-msoft-float" |
| and not, etc. A different libstdc++ will be built for each of |
| the different multilib versions. This option is on by default. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-sjlj-exceptions </code></dt> |
| <dd><p>Forces old, set-jump/long-jump exception handling model. If |
| at all possible, the new, frame unwinding exception handling routines |
| should be used instead, as they significantly reduce both |
| runtime memory usage and executable size. This option can |
| change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-version-specific-runtime-libs </code></dt> |
| <dd><p>Specify that run-time libraries should be installed in the |
| compiler-specific subdirectory (i.e., |
| <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>) |
| instead of <code>${libdir}</code>. This option is useful if you |
| intend to use several versions of gcc in parallel. In addition, |
| libstdc++'s include files will be installed in |
| <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>, |
| unless you also specify |
| <code>--with-gxx-include-dir=<em>dirname</em></code> during configuration. |
| </p> |
| </dd> |
| |
| <dt><code>--with-gxx-include-dir=<include-files dir></code></dt> |
| <dd><p>Adds support for named libstdc++ include directory. For instance, |
| the following puts all the libstdc++ headers into a directory |
| called "2.97-20001008" instead of the usual |
| "c++/(version)". |
| </p> |
| <pre> |
| --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre> </dd> |
| |
| <dt><code>--enable-cstdio </code></dt> |
| <dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code> |
| (described next). This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-cstdio=OPTION </code></dt> |
| <dd><p>Select a target-specific I/O package. At the moment, the only |
| choice is to use 'stdio', a generic "C" abstraction. |
| The default is 'stdio'. A longer explanation is <a |
| href="explanations.html#cstdio">here</a>. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-clocale </code></dt> |
| <dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code> |
| (described next). This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-clocale=OPTION </code></dt> |
| <dd><p>Select a target-specific underlying locale package. The |
| choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix |
| (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets, |
| 'gnu' to specify a model based on functionality from the GNU C |
| library (langinfo/iconv/gettext) (from <a |
| href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C |
| library), or 'generic' to use a generic "C" |
| abstraction which consists of "C" locale info. |
| </p> |
| |
| <p>As part of the configuration process, the "C" library is |
| probed both for sufficient vintage, and installed locale |
| data. If either of these elements are not present, the C++ |
| locale model default to 'generic.' On glibc-based systems of |
| version 2.2.5 and above with installed locale files, 'gnu' is |
| automatically selected. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-libstdcxx-allocator </code></dt> |
| <dd><p>This is an abbreviated form of |
| <code>'--enable-libstdcxx-allocator=auto'</code> (described |
| next). This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-libstdcxx-allocator=OPTION </code></dt> |
| <dd><p>Select a target-specific underlying std::allocator. The |
| choices are 'new' to specify a wrapper for new, 'malloc' to |
| specify a wrapper for malloc, 'mt' for a fixed power of two allocator |
| (<a href="ext/mt_allocator.html">documented</a> under extensions), |
| 'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator. |
| This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-cheaders=OPTION </code></dt> |
| <dd><p>This allows the user to define what kind of C headers are |
| used. Options are c and c_std. These correspond to the source |
| directory's include/c and include/c_std. The default is c_std. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-threads </code></dt> |
| <dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code> |
| (described next). This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-threads=OPTION </code></dt> |
| <dd><p>Select a threading library. A full description is given in the |
| general <a href="http://gcc.gnu.org/install/configure.html">compiler |
| configuration instructions</a>. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-libstdcxx-debug </code></dt> |
| <dd><p>Build separate debug libraries in addition to what is normally built. |
| By default, the debug libraries are compiled with |
| <code> CXXFLAGS='-g3 -O0'</code> |
| , are installed in <code>${libdir}/debug</code>, and have the |
| same names and versioning information as the non-debug |
| libraries. This option is off by default. |
| </p> |
| <p>Note this make command, executed in |
| the build directory, will do much the same thing, without the |
| configuration difference and without building everything twice: |
| <code>make CXXFLAGS='-g3 -O0' all</code> |
| </p> |
| </dd> |
| |
| <dt><code>--enable-libstdcxx-debug-flags=FLAGS</code></dt> |
| |
| <dd><p>This option is only valid when <code> --enable-debug </code> |
| is also specified, and applies to the debug builds only. With |
| this option, you can pass a specific string of flags to the |
| compiler to use when building the debug versions of libstdc++. |
| FLAGS is a quoted string of options, like |
| </p> |
| <pre> |
| --enable-libstdcxx-debug-flags='-g3 -O1 -gdwarf-2'</pre> |
| </dd> |
| |
| <dt><code>--enable-cxx-flags=FLAGS</code></dt> |
| <dd><p>With this option, you can pass a string of -f (functionality) |
| flags to the compiler to use when building libstdc++. This |
| option can change the library ABI. FLAGS is a quoted string of |
| options, like |
| </p> |
| <pre> |
| --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre> |
| <p> |
| Note that the flags don't necessarily have to all be -f flags, |
| as shown, but usually those are the ones that will make sense |
| for experimentation and configure-time overriding. |
| </p> |
| <p>The advantage of --enable-cxx-flags over setting CXXFLAGS in |
| the 'make' environment is that, if files are automatically |
| rebuilt, the same flags will be used when compiling those files |
| as well, so that everything matches. |
| </p> |
| <p>Fun flags to try might include combinations of |
| </p> |
| <pre> |
| -fstrict-aliasing |
| -fno-exceptions |
| -ffunction-sections |
| -fvtable-gc</pre> |
| <p>and opposite forms (-fno-) of the same. Tell us (the libstdc++ |
| mailing list) if you discover more! |
| </p> |
| </dd> |
| |
| <dt><code>--enable-c99 </code></dt> |
| <dd><p>The "long long" type was introduced in C99, along |
| with many other functions for wide characters, and math |
| classification macros, etc. If enabled, all C99 functions not |
| specified by the C++ standard will be put into <code>namespace |
| __gnu_cxx</code>, and then all these names will |
| be injected into namespace std, so that C99 functions can be |
| used "as if" they were in the C++ standard (as they |
| will eventually be in some future revision of the standard, |
| without a doubt). By default, C99 support is on, assuming the |
| configure probes find all the necessary functions and bits |
| necessary. This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-wchar_t </code>[default]</dt> |
| <dd><p>Template specializations for the "wchar_t" type are |
| required for wide character conversion support. Disabling |
| wide character specializations may be expedient for initial |
| porting efforts, but builds only a subset of what is required by |
| ISO, and is not recommended. By default, this option is on. |
| This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-long-long </code></dt> |
| <dd><p>The "long long" type was introduced in C99. It is |
| provided as a GNU extension to C++98 in g++. This flag builds |
| support for "long long" into the library (specialized |
| templates and the like for iostreams). This option is on by default: |
| if enabled, users will have to either use the new-style "C" |
| headers by default (i.e., <cmath> not <math.h>) |
| or add appropriate compile-time flags to all compile lines to |
| allow "C" visibility of this feature (on GNU/Linux, |
| the flag is -D_ISOC99_SOURCE, which is added automatically via |
| CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE). |
| This option can change the library ABI. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-fully-dynamic-string </code></dt> |
| <dd><p>This option enables a special version of basic_string avoiding |
| the optimization that allocates empty objects in static memory. |
| Mostly useful together with shared memory allocators, see PR |
| libstdc++/16612 for details. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-concept-checks </code></dt> |
| <dd><p>This turns on additional compile-time checks for instantiated |
| library templates, in the form of specialized templates, |
| <a href="19_diagnostics/howto.html#3">described here</a>. They |
| can help users discover when they break the rules of the STL, before |
| their programs run. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-symvers[=style] </code></dt> |
| |
| <dd><p>In 3.1 and later, tries to turn on symbol versioning in the |
| shared library (if a shared library has been |
| requested). Values for 'style' that are currently supported |
| are 'gnu', 'gnu-versioned-namespace', 'darwin', and |
| 'darwin-export'. Both gnu- options require that a recent |
| version of the GNU linker be in use. Both darwin options are |
| equivalent. With no style given, the configure script will try |
| to guess correct defaults for the host system, probe to see if |
| additional requirements are necessary and present for |
| activation, and if so, will turn symbol versioning on. This |
| option can change the library ABI. |
| </p> |
| |
| </dd> |
| |
| <dt><code>--enable-visibility </code></dt> |
| <dd><p> In 4.2 and later, enables or disables visibility attributes. |
| If enabled (as by default), and the compiler seems capable of |
| passing the simple sanity checks thrown at it, adjusts items |
| in namespace std, namespace std::tr1, and namespace __gnu_cxx |
| so that -fvisibility options work. |
| </p> |
| </dd> |
| |
| <dt><code>--enable-libstdcxx-pch </code></dt> |
| <dd><p>In 3.4 and later, tries to turn on the generation of |
| stdc++.h.gch, a pre-compiled file including all the standard |
| C++ includes. If enabled (as by default), and the compiler |
| seems capable of passing the simple sanity checks thrown at |
| it, try to build stdc++.h.gch as part of the make process. |
| In addition, this generated file is used later on (by appending <code> |
| --include bits/stdc++.h </code> to CXXFLAGS) when running the |
| testsuite. |
| </p> |
| </dd> |
| |
| <dt><code>--disable-hosted-libstdcxx </code></dt> |
| <dd><p>By default, a complete <em>hosted</em> C++ library is built. The |
| C++ Standard also describes a <em>freestanding</em> environment, |
| in which only a minimal set of headers are provided. This option |
| builds such an environment. |
| </p> |
| </dd> |
| </dl> |
| <p>Return <a href="#top">to the top of the page</a> or |
| <a href="http://gcc.gnu.org/libstdc++/">to the libstdc++ homepage</a>. |
| </p> |
| |
| |
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| See <a href="17_intro/license.html">license.html</a> for copying conditions. |
| Comments and suggestions are welcome, and may be sent to |
| <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>. |
| </em></p> |
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