docs/ReleaseNotes.rst - clang - Git at Google

 =======================================
 Clang 6.0.0 (In-Progress) Release Notes
 =======================================

 .. contents::
    :local:
    :depth: 2

 Written by the `LLVM Team <http://llvm.org/>`_

 .. warning::

    These are in-progress notes for the upcoming Clang 6 release.
    Release notes for previous releases can be found on
    `the Download Page <http://releases.llvm.org/download.html>`_.

 Introduction
 ============

 This document contains the release notes for the Clang C/C++/Objective-C
 frontend, part of the LLVM Compiler Infrastructure, release 6.0.0. Here we
 describe the status of Clang in some detail, including major
 improvements from the previous release and new feature work. For the
 general LLVM release notes, see `the LLVM
 documentation <http://llvm.org/docs/ReleaseNotes.html>`_. All LLVM
 releases may be downloaded from the `LLVM releases web
 site <http://llvm.org/releases/>`_.

 For more information about Clang or LLVM, including information about the
 latest release, please see the `Clang Web Site <http://clang.llvm.org>`_ or the
 `LLVM Web Site <http://llvm.org>`_.

 Note that if you are reading this file from a Subversion checkout or the
 main Clang web page, this document applies to the *next* release, not
 the current one. To see the release notes for a specific release, please
 see the `releases page <http://llvm.org/releases/>`_.

 What's New in Clang 6.0.0?
 ==========================

 Some of the major new features and improvements to Clang are listed
 here. Generic improvements to Clang as a whole or to its underlying
 infrastructure are described first, followed by language-specific
 sections with improvements to Clang's support for those languages.

 Major New Features
 ------------------

 -  ...

 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 - ``-Wpragma-pack`` is a new warning that warns in the following cases:

   - When a translation unit is missing terminating ``#pragma pack (pop)``
     directives.

   - When leaving an included file that changes the current alignment value,
     i.e. when the alignment before ``#include`` is different to the alignment
     after ``#include``.

   - ``-Wpragma-pack-suspicious-include`` (disabled by default) warns on an
     ``#include`` when the included file contains structures or unions affected by
     a non-default alignment that has been specified using a ``#pragma pack``
     directive prior to the ``#include``.

 - ``-Wobjc-messaging-id`` is a new, non-default warning that warns about
   message sends to unqualified ``id`` in Objective-C. This warning is useful
   for projects that would like to avoid any potential future compiler
   errors/warnings, as the system frameworks might add a method with the same
   selector which could make the message send to ``id`` ambiguous.

 - ``-Wtautological-compare`` now warns when comparing an unsigned integer and 0
   regardless of whether the constant is signed or unsigned."

 - ``-Wtautological-compare`` now warns about comparing a signed integer and 0
   when the signed integer is coerced to an unsigned type for the comparison.
   ``-Wsign-compare`` was adjusted not to warn in this case.

 - ``-Wtautological-constant-compare`` is a new warning that warns on
   tautological comparisons between integer variable of the type ``T`` and the
   largest/smallest possible integer constant of that same type.

 - For C code, ``-Wsign-compare``, ``-Wsign-conversion``,
   ``-Wtautological-constant-compare`` and
   ``-Wtautological-constant-out-of-range-compare`` were adjusted to use the
   underlying datatype of ``enum``.

 - ``-Wnull-pointer-arithmetic`` now warns about performing pointer arithmetic
   on a null pointer. Such pointer arithmetic has an undefined behavior if the
   offset is nonzero. It also now warns about arithmetic on a null pointer
   treated as a cast from integer to pointer (GNU extension).

 - ``-Wzero-as-null-pointer-constant`` was adjusted not to warn on null pointer
   constants that originate from system macros, except ``NULL`` macro.

 Non-comprehensive list of changes in this release
 -------------------------------------------------

 - Bitrig OS was merged back into OpenBSD, so Bitrig support has been
   removed from Clang/LLVM.

 - The default value of _MSC_VER was raised from 1800 to 1911, making it
   compatible with the Visual Studio 2015 and 2017 C++ standard library headers.
   Users should generally expect this to be regularly raised to match the most
   recently released version of the Visual C++ compiler.

 - clang now defaults to ``.init_array`` if no gcc installation can be found.
   If a gcc installation is found, it still prefers ``.ctors`` if the found
   gcc is older than 4.7.0.

 New Compiler Flags
 ------------------

 - --autocomplete was implemented to obtain a list of flags and its arguments. This is used for shell autocompletion.

 - The ``-fdouble-square-bracket-attributes`` and corresponding
   ``-fno-double-square-bracket-attributes`` flags were added to enable or
   disable [[]] attributes in any language mode. Currently, only a limited
   number of attributes are supported outside of C++ mode. See the Clang
   attribute documentation for more information about which attributes are
   supported for each syntax.

 Deprecated Compiler Flags
 -------------------------

 The following options are deprecated and ignored. They will be removed in
 future versions of Clang.

 - ...

 New Pragmas in Clang
 -----------------------

 Clang now supports the ...


 Attribute Changes in Clang
 --------------------------

 - The presence of __attribute__((availability(...))) on a declaration no longer
   implies default visibility for that declaration on macOS.

 - ...

 Windows Support
 ---------------

 Clang's support for building native Windows programs ...


 C Language Changes in Clang
 ---------------------------

 - ...

 ...

 C11 Feature Support
 ^^^^^^^^^^^^^^^^^^^

 ...

 C++ Language Changes in Clang
 -----------------------------

 ...

 C++1z Feature Support
 ^^^^^^^^^^^^^^^^^^^^^

 ...

 Objective-C Language Changes in Clang
 -------------------------------------

 ...

 OpenCL C Language Changes in Clang
 ----------------------------------

 ...

 OpenMP Support in Clang
 ----------------------------------

 ...

 Internal API Changes
 --------------------

 These are major API changes that have happened since the 4.0.0 release of
 Clang. If upgrading an external codebase that uses Clang as a library,
 this section should help get you past the largest hurdles of upgrading.

 -  ...

 AST Matchers
 ------------

 The hasDeclaration matcher now works the same for Type and QualType and only
 ever looks through one level of sugaring in a limited number of cases.

 There are two main patterns affected by this:

 -  qualType(hasDeclaration(recordDecl(...))): previously, we would look through
    sugar like TypedefType to get at the underlying recordDecl; now, we need
    to explicitly remove the sugaring:
    qualType(hasUnqualifiedDesugaredType(hasDeclaration(recordDecl(...))))

 -  hasType(recordDecl(...)): hasType internally uses hasDeclaration; previously,
    this matcher used to match for example TypedefTypes of the RecordType, but
    after the change they don't; to fix, use:

 ::
    hasType(hasUnqualifiedDesugaredType(
        recordType(hasDeclaration(recordDecl(...)))))

 -  templateSpecializationType(hasDeclaration(classTemplateDecl(...))):
    previously, we would directly match the underlying ClassTemplateDecl;
    now, we can explicitly match the ClassTemplateSpecializationDecl, but that
    requires to explicitly get the ClassTemplateDecl:

 ::
    templateSpecializationType(hasDeclaration(
        classTemplateSpecializationDecl(
            hasSpecializedTemplate(classTemplateDecl(...)))))

 clang-format
 ------------

 * Option *IndentPPDirectives* added to indent preprocessor directives on
   conditionals.

   +----------------------+----------------------+
   | Before               | After                |
   +======================+======================+
   |  .. code-block:: c++ | .. code-block:: c++  |
   |                      |                      |
   |    #if FOO           |   #if FOO            |
   |    #if BAR           |   #  if BAR          |
   |    #include <foo>    |   #    include <foo> |
   |    #endif            |   #  endif           |
   |    #endif            |   #endif             |
   +----------------------+----------------------+

 * Option -verbose added to the command line.
   Shows the list of processed files.

 libclang
 --------

 ...


 Static Analyzer
 ---------------

 ...

 Undefined Behavior Sanitizer (UBSan)
 ------------------------------------

 * A minimal runtime is now available. It is suitable for use in production
   environments, and has a small attack surface. It only provides very basic
   issue logging and deduplication, and does not support ``-fsanitize=vptr``
   checking.

 Core Analysis Improvements
 ==========================

 - ...

 New Issues Found
 ================

 - ...

 Python Binding Changes
 ----------------------

 The following methods have been added:

 -  ...

 Significant Known Problems
 ==========================

 Additional Information
 ======================

 A wide variety of additional information is available on the `Clang web
 page <http://clang.llvm.org/>`_. The web page contains versions of the
 API documentation which are up-to-date with the Subversion version of
 the source code. You can access versions of these documents specific to
 this release by going into the "``clang/docs/``" directory in the Clang
 tree.

 If you have any questions or comments about Clang, please feel free to
 contact us via the `mailing
 list <http://lists.llvm.org/mailman/listinfo/cfe-dev>`_.
	=======================================
	Clang 6.0.0 (In-Progress) Release Notes
	=======================================

	.. contents::
	:local:
	:depth: 2

	Written by the `LLVM Team <http://llvm.org/>`_

	.. warning::

	These are in-progress notes for the upcoming Clang 6 release.
	Release notes for previous releases can be found on
	`the Download Page <http://releases.llvm.org/download.html>`_.

	Introduction
	============

	This document contains the release notes for the Clang C/C++/Objective-C
	frontend, part of the LLVM Compiler Infrastructure, release 6.0.0. Here we
	describe the status of Clang in some detail, including major
	improvements from the previous release and new feature work. For the
	general LLVM release notes, see `the LLVM
	documentation <http://llvm.org/docs/ReleaseNotes.html>`_. All LLVM
	releases may be downloaded from the `LLVM releases web
	site <http://llvm.org/releases/>`_.

	For more information about Clang or LLVM, including information about the
	latest release, please see the `Clang Web Site <http://clang.llvm.org>`_ or the
	`LLVM Web Site <http://llvm.org>`_.

	Note that if you are reading this file from a Subversion checkout or the
	main Clang web page, this document applies to the next release, not
	the current one. To see the release notes for a specific release, please
	see the `releases page <http://llvm.org/releases/>`_.

	What's New in Clang 6.0.0?
	==========================

	Some of the major new features and improvements to Clang are listed
	here. Generic improvements to Clang as a whole or to its underlying
	infrastructure are described first, followed by language-specific
	sections with improvements to Clang's support for those languages.

	Major New Features
	------------------

	- ...

	Improvements to Clang's diagnostics
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	- ``-Wpragma-pack`` is a new warning that warns in the following cases:

	- When a translation unit is missing terminating ``#pragma pack (pop)``
	directives.

	- When leaving an included file that changes the current alignment value,
	i.e. when the alignment before ``#include`` is different to the alignment
	after ``#include``.

	- ``-Wpragma-pack-suspicious-include`` (disabled by default) warns on an
	``#include`` when the included file contains structures or unions affected by
	a non-default alignment that has been specified using a ``#pragma pack``
	directive prior to the ``#include``.

	- ``-Wobjc-messaging-id`` is a new, non-default warning that warns about
	message sends to unqualified ``id`` in Objective-C. This warning is useful
	for projects that would like to avoid any potential future compiler
	errors/warnings, as the system frameworks might add a method with the same
	selector which could make the message send to ``id`` ambiguous.

	- ``-Wtautological-compare`` now warns when comparing an unsigned integer and 0
	regardless of whether the constant is signed or unsigned."

	- ``-Wtautological-compare`` now warns about comparing a signed integer and 0
	when the signed integer is coerced to an unsigned type for the comparison.
	``-Wsign-compare`` was adjusted not to warn in this case.

	- ``-Wtautological-constant-compare`` is a new warning that warns on
	tautological comparisons between integer variable of the type ``T`` and the
	largest/smallest possible integer constant of that same type.

	- For C code, ``-Wsign-compare``, ``-Wsign-conversion``,
	``-Wtautological-constant-compare`` and
	``-Wtautological-constant-out-of-range-compare`` were adjusted to use the
	underlying datatype of ``enum``.

	- ``-Wnull-pointer-arithmetic`` now warns about performing pointer arithmetic
	on a null pointer. Such pointer arithmetic has an undefined behavior if the
	offset is nonzero. It also now warns about arithmetic on a null pointer
	treated as a cast from integer to pointer (GNU extension).

	- ``-Wzero-as-null-pointer-constant`` was adjusted not to warn on null pointer
	constants that originate from system macros, except ``NULL`` macro.

	Non-comprehensive list of changes in this release
	-------------------------------------------------

	- Bitrig OS was merged back into OpenBSD, so Bitrig support has been
	removed from Clang/LLVM.

	- The default value of _MSC_VER was raised from 1800 to 1911, making it
	compatible with the Visual Studio 2015 and 2017 C++ standard library headers.
	Users should generally expect this to be regularly raised to match the most
	recently released version of the Visual C++ compiler.

	- clang now defaults to ``.init_array`` if no gcc installation can be found.
	If a gcc installation is found, it still prefers ``.ctors`` if the found
	gcc is older than 4.7.0.

	New Compiler Flags
	------------------

	- --autocomplete was implemented to obtain a list of flags and its arguments. This is used for shell autocompletion.

	- The ``-fdouble-square-bracket-attributes`` and corresponding
	``-fno-double-square-bracket-attributes`` flags were added to enable or
	disable [[]] attributes in any language mode. Currently, only a limited
	number of attributes are supported outside of C++ mode. See the Clang
	attribute documentation for more information about which attributes are
	supported for each syntax.

	Deprecated Compiler Flags
	-------------------------

	The following options are deprecated and ignored. They will be removed in
	future versions of Clang.

	- ...

	New Pragmas in Clang
	-----------------------

	Clang now supports the ...


	Attribute Changes in Clang
	--------------------------

	- The presence of __attribute__((availability(...))) on a declaration no longer
	implies default visibility for that declaration on macOS.

	- ...

	Windows Support
	---------------

	Clang's support for building native Windows programs ...


	C Language Changes in Clang
	---------------------------

	- ...

	...

	C11 Feature Support
	^^^^^^^^^^^^^^^^^^^

	...

	C++ Language Changes in Clang
	-----------------------------

	...

	C++1z Feature Support
	^^^^^^^^^^^^^^^^^^^^^

	...

	Objective-C Language Changes in Clang
	-------------------------------------

	...

	OpenCL C Language Changes in Clang
	----------------------------------

	...

	OpenMP Support in Clang
	----------------------------------

	...

	Internal API Changes
	--------------------

	These are major API changes that have happened since the 4.0.0 release of
	Clang. If upgrading an external codebase that uses Clang as a library,
	this section should help get you past the largest hurdles of upgrading.

	- ...

	AST Matchers
	------------

	The hasDeclaration matcher now works the same for Type and QualType and only
	ever looks through one level of sugaring in a limited number of cases.

	There are two main patterns affected by this:

	- qualType(hasDeclaration(recordDecl(...))): previously, we would look through
	sugar like TypedefType to get at the underlying recordDecl; now, we need
	to explicitly remove the sugaring:
	qualType(hasUnqualifiedDesugaredType(hasDeclaration(recordDecl(...))))

	- hasType(recordDecl(...)): hasType internally uses hasDeclaration; previously,
	this matcher used to match for example TypedefTypes of the RecordType, but
	after the change they don't; to fix, use:

	::
	hasType(hasUnqualifiedDesugaredType(
	recordType(hasDeclaration(recordDecl(...)))))

	- templateSpecializationType(hasDeclaration(classTemplateDecl(...))):
	previously, we would directly match the underlying ClassTemplateDecl;
	now, we can explicitly match the ClassTemplateSpecializationDecl, but that
	requires to explicitly get the ClassTemplateDecl:

	::
	templateSpecializationType(hasDeclaration(
	classTemplateSpecializationDecl(
	hasSpecializedTemplate(classTemplateDecl(...)))))

	clang-format
	------------

	* Option IndentPPDirectives added to indent preprocessor directives on
	conditionals.

	+----------------------+----------------------+
	\| Before \| After \|
	+======================+======================+
	\| .. code-block:: c++ \| .. code-block:: c++ \|
	\| \| \|
	\| #if FOO \| #if FOO \|
	\| #if BAR \| # if BAR \|
	\| #include <foo> \| # include <foo> \|
	\| #endif \| # endif \|
	\| #endif \| #endif \|
	+----------------------+----------------------+

	* Option -verbose added to the command line.
	Shows the list of processed files.

	libclang
	--------

	...


	Static Analyzer
	---------------

	...

	Undefined Behavior Sanitizer (UBSan)
	------------------------------------

	* A minimal runtime is now available. It is suitable for use in production
	environments, and has a small attack surface. It only provides very basic
	issue logging and deduplication, and does not support ``-fsanitize=vptr``
	checking.

	Core Analysis Improvements
	==========================

	- ...

	New Issues Found
	================

	- ...

	Python Binding Changes
	----------------------

	The following methods have been added:

	- ...

	Significant Known Problems
	==========================

	Additional Information
	======================

	A wide variety of additional information is available on the `Clang web
	page <http://clang.llvm.org/>`_. The web page contains versions of the
	API documentation which are up-to-date with the Subversion version of
	the source code. You can access versions of these documents specific to
	this release by going into the "``clang/docs/``" directory in the Clang
	tree.

	If you have any questions or comments about Clang, please feel free to
	contact us via the `mailing
	list <http://lists.llvm.org/mailman/listinfo/cfe-dev>`_.