docs/ReleaseNotes.rst - platform/external/clang - Git at Google

 =====================================
 Clang 3.9 (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 3.9 release. You may
    prefer the `Clang 3.8 Release Notes
    <http://llvm.org/releases/3.8.0/tools/clang/docs/ReleaseNotes.html>`_.

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

 This document contains the release notes for the Clang C/C++/Objective-C
 frontend, part of the LLVM Compiler Infrastructure, release 3.9. 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 check out the main 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 3.9?
 ========================

 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
 ------------------

 - Clang will no longer passes --build-id by default to the linker. In modern
   linkers that is a relatively expensive option. It can be passed explicitly
   with -Wl,--build-id. To have clang always pass it, build clang with
   -DENABLE_LINKER_BUILD_ID.

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

 Clang's diagnostics are constantly being improved to catch more issues,
 explain them more clearly, and provide more accurate source information
 about them. The improvements since the 3.7 release include:

 -  ...

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

 The option ....


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

 Clang now supports the ...

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

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

 TLS is enabled for Cygwin defaults to -femulated-tls.


 C Language Changes in Clang
 ---------------------------
 The -faltivec and -maltivec flags no longer silently include altivec.h on Power platforms.

 `RenderScript
 <https://developer.android.com/guide/topics/renderscript/compute.html>`_
 support added to the Frontend and enabled by the '-x renderscript' option or
 the '.rs' file extension.

 ...

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

 ...

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

 - Clang now enforces the rule that a *using-declaration* cannot name an enumerator of a
   scoped enumeration.

   .. code-block:: c++

     namespace Foo { enum class E { e }; }
     namespace Bar {
       using Foo::E::e; // error
       constexpr auto e = Foo::E::e; // ok
     }

 - Clang now enforces the rule that an enumerator of an unscoped enumeration declared at
   class scope can only be named by a *using-declaration* in a derived class.

   .. code-block:: c++

     class Foo { enum E { e }; }
     using Foo::e; // error
     static constexpr auto e = Foo::e; // ok

 ...

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

 Clang's experimental support for the upcoming C++1z standard can be enabled with ``-std=c++1z``.
 Changes to C++1z features since Clang 3.8:

 - The ``[[fallthrough]]``, ``[[nodiscard]]``, and ``[[maybe_unused]]`` attributes are
   supported in C++11 onwards, and are largely synonymous with Clang's existing attributes
   ``[[clang::fallthrough]]``, ``[[gnu::warn_unused_result]]``, and ``[[gnu::unused]]``.
   Use ``-Wimplicit-fallthrough`` to warn on unannotated fallthrough within ``switch``
   statements.

 - In C++1z mode, aggregate initialization can be performed for classes with base classes:

   .. code-block:: c++

     struct A { int n; };
     struct B : A { int x, y; };
     B b = { 1, 2, 3 }; // b.n == 1, b.x == 2, b.y == 3

 - The range in a range-based ``for`` statement can have different types for its ``begin``
   and ``end`` iterators. This is permitted as an extension in C++11 onwards.

 - Lambda-expressions can explicitly capture ``*this`` (to capture the surrounding object
   by copy). This is permitted as an extension in C++11 onwards.

 - Objects of enumeration type can be direct-list-initialized from a value of the underlying
   type. ``E{n}`` is equivalent to ``E(n)``, except that it implies a check for a narrowing
   conversion.

 - Unary *fold-expression*\s over an empty pack are now rejected for all operators
   other than ``&&``, ``||``, and ``,``.

 ...

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

 ...

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

 ...

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

 Added support for all non-offloading features from OpenMP 4.5, including using
 data members in private clauses of non-static member functions. Additionally,
 data members can be used as loop control variables in loop-based directives.

 Currently Clang supports OpenMP 3.1 and all non-offloading features of
 OpenMP 4.0/4.5. Offloading features are under development. Clang defines macro
 _OPENMP and sets it to OpenMP 3.1 (in accordance with OpenMP standard) by
 default. User may change this value using ``-fopenmp-version=[31|40|45]`` option.

 The codegen for OpenMP constructs was significantly improved to produce much
 more stable and faster code.

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

 These are major API changes that have happened since the 3.8 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
 ------------

 - has and hasAnyArgument: Matchers no longer ignores parentheses and implicit
   casts on the argument before applying the inner matcher. The fix was done to
   allow for greater control by the user. In all existing checkers that use this
   matcher all instances of code ``hasAnyArgument(<inner matcher>)`` or
   ``has(<inner matcher>)`` must be changed to
   ``hasAnyArgument(ignoringParenImpCasts(<inner matcher>))`` or
   ``has(ignoringParenImpCasts(<inner matcher>))``.

 ...

 libclang
 --------

 ...

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

 ...

 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 3.9 (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 3.9 release. You may
	prefer the `Clang 3.8 Release Notes
	<http://llvm.org/releases/3.8.0/tools/clang/docs/ReleaseNotes.html>`_.

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

	This document contains the release notes for the Clang C/C++/Objective-C
	frontend, part of the LLVM Compiler Infrastructure, release 3.9. 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 check out the main 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 3.9?
	========================

	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
	------------------

	- Clang will no longer passes --build-id by default to the linker. In modern
	linkers that is a relatively expensive option. It can be passed explicitly
	with -Wl,--build-id. To have clang always pass it, build clang with
	-DENABLE_LINKER_BUILD_ID.

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

	Clang's diagnostics are constantly being improved to catch more issues,
	explain them more clearly, and provide more accurate source information
	about them. The improvements since the 3.7 release include:

	- ...

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

	The option ....


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

	Clang now supports the ...

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

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

	TLS is enabled for Cygwin defaults to -femulated-tls.


	C Language Changes in Clang
	---------------------------
	The -faltivec and -maltivec flags no longer silently include altivec.h on Power platforms.

	`RenderScript
	<https://developer.android.com/guide/topics/renderscript/compute.html>`_
	support added to the Frontend and enabled by the '-x renderscript' option or
	the '.rs' file extension.

	...

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

	...

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

	- Clang now enforces the rule that a using-declaration cannot name an enumerator of a
	scoped enumeration.

	.. code-block:: c++

	namespace Foo { enum class E { e }; }
	namespace Bar {
	using Foo::E::e; // error
	constexpr auto e = Foo::E::e; // ok
	}

	- Clang now enforces the rule that an enumerator of an unscoped enumeration declared at
	class scope can only be named by a using-declaration in a derived class.

	.. code-block:: c++

	class Foo { enum E { e }; }
	using Foo::e; // error
	static constexpr auto e = Foo::e; // ok

	...

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

	Clang's experimental support for the upcoming C++1z standard can be enabled with ``-std=c++1z``.
	Changes to C++1z features since Clang 3.8:

	- The ``[[fallthrough]]``, ``[[nodiscard]]``, and ``[[maybe_unused]]`` attributes are
	supported in C++11 onwards, and are largely synonymous with Clang's existing attributes
	``[[clang::fallthrough]]``, ``[[gnu::warn_unused_result]]``, and ``[[gnu::unused]]``.
	Use ``-Wimplicit-fallthrough`` to warn on unannotated fallthrough within ``switch``
	statements.

	- In C++1z mode, aggregate initialization can be performed for classes with base classes:

	.. code-block:: c++

	struct A { int n; };
	struct B : A { int x, y; };
	B b = { 1, 2, 3 }; // b.n == 1, b.x == 2, b.y == 3

	- The range in a range-based ``for`` statement can have different types for its ``begin``
	and ``end`` iterators. This is permitted as an extension in C++11 onwards.

	- Lambda-expressions can explicitly capture ``*this`` (to capture the surrounding object
	by copy). This is permitted as an extension in C++11 onwards.

	- Objects of enumeration type can be direct-list-initialized from a value of the underlying
	type. ``E{n}`` is equivalent to ``E(n)``, except that it implies a check for a narrowing
	conversion.

	- Unary fold-expression\s over an empty pack are now rejected for all operators
	other than ``&&``, ``\|\|``, and ``,``.

	...

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

	...

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

	...

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

	Added support for all non-offloading features from OpenMP 4.5, including using
	data members in private clauses of non-static member functions. Additionally,
	data members can be used as loop control variables in loop-based directives.

	Currently Clang supports OpenMP 3.1 and all non-offloading features of
	OpenMP 4.0/4.5. Offloading features are under development. Clang defines macro
	_OPENMP and sets it to OpenMP 3.1 (in accordance with OpenMP standard) by
	default. User may change this value using ``-fopenmp-version=[31\|40\|45]`` option.

	The codegen for OpenMP constructs was significantly improved to produce much
	more stable and faster code.

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

	These are major API changes that have happened since the 3.8 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
	------------

	- has and hasAnyArgument: Matchers no longer ignores parentheses and implicit
	casts on the argument before applying the inner matcher. The fix was done to
	allow for greater control by the user. In all existing checkers that use this
	matcher all instances of code ``hasAnyArgument(<inner matcher>)`` or
	``has(<inner matcher>)`` must be changed to
	``hasAnyArgument(ignoringParenImpCasts(<inner matcher>))`` or
	``has(ignoringParenImpCasts(<inner matcher>))``.

	...

	libclang
	--------

	...

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

	...

	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>`_.