clang/docs/ReleaseNotes.rst - llvm-project - Git at Google

 ===========================================
 Clang |release| |ReleaseNotesTitle|
 ===========================================

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

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

 .. only:: PreRelease

   .. warning::
      These are in-progress notes for the upcoming Clang |version| release.
      Release notes for previous releases can be found on
      `the Releases Page <https://llvm.org/releases/>`_.

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

 This document contains the release notes for the Clang C/C++/Objective-C
 frontend, part of the LLVM Compiler Infrastructure, release |release|. 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 <https://llvm.org/docs/ReleaseNotes.html>`_. For the libc++ release notes,
 see `this page <https://libcxx.llvm.org/ReleaseNotes.html>`_. All LLVM releases
 may be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_.

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

 Potentially Breaking Changes
 ============================
 These changes are ones which we think may surprise users when upgrading to
 Clang |release| because of the opportunity they pose for disruption to existing
 code bases.

 C/C++ Language Potentially Breaking Changes
 -------------------------------------------

 C++ Specific Potentially Breaking Changes
 -----------------------------------------

 ABI Changes in This Version
 ---------------------------

 AST Dumping Potentially Breaking Changes
 ----------------------------------------

 Clang Frontend Potentially Breaking Changes
 -------------------------------------------

 Clang Python Bindings Potentially Breaking Changes
 --------------------------------------------------
 - Parts of the interface returning string results will now return
   the empty string `""` when no result is available, instead of `None`.
 - Calling a property on the `CompletionChunk` or `CompletionString` class
   statically now leads to an error, instead of returning a `CachedProperty` object
   that is used internally. Properties are only available on instances.

 What's New in Clang |release|?
 ==============================
 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.

 C++ Language Changes
 --------------------

 C++17 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^

 C++14 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^

 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^

 C++23 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 - Removed the restriction to literal types in constexpr functions in C++23 mode.

 C++2c Feature Support
 ^^^^^^^^^^^^^^^^^^^^^

 - Add ``__builtin_is_virtual_base_of`` intrinsic, which supports
   `P2985R0 A type trait for detecting virtual base classes <https://wg21.link/p2985r0>`_

 Resolutions to C++ Defect Reports
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 C Language Changes
 ------------------

 C2y Feature Support
 ^^^^^^^^^^^^^^^^^^^

 C23 Feature Support
 ^^^^^^^^^^^^^^^^^^^

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

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

 Modified Compiler Flags
 -----------------------

 Removed Compiler Flags
 -------------------------

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

 - Clang now disallows more than one ``__attribute__((ownership_returns(class, idx)))`` with
   different class names attached to one function.

 - Introduced a new format attribute ``__attribute__((format(syslog, 1, 2)))`` from OpenBSD.

 - The ``hybrid_patchable`` attribute is now supported on ARM64EC targets. It can be used to specify
   that a function requires an additional x86-64 thunk, which may be patched at runtime.

 Improvements to Clang's diagnostics
 -----------------------------------

 - Some template related diagnostics have been improved.

   .. code-block:: c++

      void foo() { template <typename> int i; } // error: templates can only be declared in namespace or class scope

      struct S {
       template <typename> int i; // error: non-static data member 'i' cannot be declared as a template
      };

 - Clang now has improved diagnostics for functions with explicit 'this' parameters. Fixes #GH97878

 - Clang now diagnoses dangling references to fields of temporary objects. Fixes #GH81589.

 - Clang now diagnoses undefined behavior in constant expressions more consistently. This includes invalid shifts, and signed overflow in arithmetic.

 - -Wdangling-assignment-gsl is enabled by default.

 Improvements to Clang's time-trace
 ----------------------------------

 Improvements to Coverage Mapping
 --------------------------------

 Bug Fixes in This Version
 -------------------------

 - Fixed the definition of ``ATOMIC_FLAG_INIT`` in ``<stdatomic.h>`` so it can
   be used in C++.

 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 Bug Fixes to Attribute Support
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^

 - Fixed a crash when an expression with a dependent ``__typeof__`` type is used as the operand of a unary operator. (#GH97646)
 - Fixed a failed assertion when checking invalid delete operator declaration. (#GH96191)
 - Fix a crash when checking destructor reference with an invalid initializer. (#GH97230)
 - Clang now correctly parses potentially declarative nested-name-specifiers in pointer-to-member declarators.

 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

 Miscellaneous Bug Fixes
 ^^^^^^^^^^^^^^^^^^^^^^^

 Miscellaneous Clang Crashes Fixed
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 - Fixed a crash in C due to incorrect lookup that members in nested anonymous struct/union
   can be found as ordinary identifiers in struct/union definition. (#GH31295)

 OpenACC Specific Changes
 ------------------------

 Target Specific Changes
 -----------------------

 AMDGPU Support
 ^^^^^^^^^^^^^^

 X86 Support
 ^^^^^^^^^^^

 - The MMX vector intrinsic functions from ``*mmintrin.h`` which
   operate on `__m64` vectors, such as ``_mm_add_pi8``, have been
   reimplemented to use the SSE2 instruction-set and XMM registers
   unconditionally. These intrinsics are therefore *no longer
   supported* if MMX is enabled without SSE2 -- either from targeting
   CPUs from the Pentium-MMX through the Pentium 3, or explicitly via
   passing arguments such as ``-mmmx -mno-sse2``. MMX assembly code
   remains supported without requiring SSE2, including inside
   inline-assembly.

 - The compiler builtins such as ``__builtin_ia32_paddb`` which
   formerly implemented the above MMX intrinsic functions have been
   removed. Any uses of these removed functions should migrate to the
   functions defined by the ``*mmintrin.h`` headers. A mapping can be
   found in the file ``clang/www/builtins.py``.

 Arm and AArch64 Support
 ^^^^^^^^^^^^^^^^^^^^^^^

 Android Support
 ^^^^^^^^^^^^^^^

 Windows Support
 ^^^^^^^^^^^^^^^

 LoongArch Support
 ^^^^^^^^^^^^^^^^^

 RISC-V Support
 ^^^^^^^^^^^^^^

 CUDA/HIP Language Changes
 ^^^^^^^^^^^^^^^^^^^^^^^^^

 CUDA Support
 ^^^^^^^^^^^^

 AIX Support
 ^^^^^^^^^^^

 NetBSD Support
 ^^^^^^^^^^^^^^

 WebAssembly Support
 ^^^^^^^^^^^^^^^^^^^

 AVR Support
 ^^^^^^^^^^^

 DWARF Support in Clang
 ----------------------

 Floating Point Support in Clang
 -------------------------------

 Fixed Point Support in Clang
 ----------------------------

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

 - Fixed an issue with the `hasName` and `hasAnyName` matcher when matching
   inline namespaces with an enclosing namespace of the same name.

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

 libclang
 --------

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

 New features
 ^^^^^^^^^^^^

 - MallocChecker now checks for ``ownership_returns(class, idx)`` and ``ownership_takes(class, idx)``
   attributes with class names different from "malloc". Clang static analyzer now reports an error
   if class of allocation and deallocation function mismatches.
   `Documentation <https://clang.llvm.org/docs/analyzer/checkers.html#unix-mismatcheddeallocator-c-c>`__.

 Crash and bug fixes
 ^^^^^^^^^^^^^^^^^^^

 Improvements
 ^^^^^^^^^^^^

 - Improved the handling of the ``ownership_returns`` attribute. Now, Clang reports an
   error if the attribute is attached to a function that returns a non-pointer value.
   Fixes (#GH99501)

 Moved checkers
 ^^^^^^^^^^^^^^

 .. _release-notes-sanitizers:

 Sanitizers
 ----------

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

 OpenMP Support
 --------------

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

 A wide variety of additional information is available on the `Clang web
 page <https://clang.llvm.org/>`_. The web page contains versions of the
 API documentation which are up-to-date with the Git 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 on the `Discourse forums (Clang Frontend category)
 <https://discourse.llvm.org/c/clang/6>`_.
	===========================================
	Clang \|release\| \|ReleaseNotesTitle\|
	===========================================

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

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

	.. only:: PreRelease

	.. warning::
	These are in-progress notes for the upcoming Clang \|version\| release.
	Release notes for previous releases can be found on
	`the Releases Page <https://llvm.org/releases/>`_.

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

	This document contains the release notes for the Clang C/C++/Objective-C
	frontend, part of the LLVM Compiler Infrastructure, release \|release\|. 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 <https://llvm.org/docs/ReleaseNotes.html>`_. For the libc++ release notes,
	see `this page <https://libcxx.llvm.org/ReleaseNotes.html>`_. All LLVM releases
	may be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_.

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

	Potentially Breaking Changes
	============================
	These changes are ones which we think may surprise users when upgrading to
	Clang \|release\| because of the opportunity they pose for disruption to existing
	code bases.

	C/C++ Language Potentially Breaking Changes
	-------------------------------------------

	C++ Specific Potentially Breaking Changes
	-----------------------------------------

	ABI Changes in This Version
	---------------------------

	AST Dumping Potentially Breaking Changes
	----------------------------------------

	Clang Frontend Potentially Breaking Changes
	-------------------------------------------

	Clang Python Bindings Potentially Breaking Changes
	--------------------------------------------------
	- Parts of the interface returning string results will now return
	the empty string `""` when no result is available, instead of `None`.
	- Calling a property on the `CompletionChunk` or `CompletionString` class
	statically now leads to an error, instead of returning a `CachedProperty` object
	that is used internally. Properties are only available on instances.

	What's New in Clang \|release\|?
	==============================
	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.

	C++ Language Changes
	--------------------

	C++17 Feature Support
	^^^^^^^^^^^^^^^^^^^^^

	C++14 Feature Support
	^^^^^^^^^^^^^^^^^^^^^

	C++20 Feature Support
	^^^^^^^^^^^^^^^^^^^^^

	C++23 Feature Support
	^^^^^^^^^^^^^^^^^^^^^
	- Removed the restriction to literal types in constexpr functions in C++23 mode.

	C++2c Feature Support
	^^^^^^^^^^^^^^^^^^^^^

	- Add ``__builtin_is_virtual_base_of`` intrinsic, which supports
	`P2985R0 A type trait for detecting virtual base classes <https://wg21.link/p2985r0>`_

	Resolutions to C++ Defect Reports
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	C Language Changes
	------------------

	C2y Feature Support
	^^^^^^^^^^^^^^^^^^^

	C23 Feature Support
	^^^^^^^^^^^^^^^^^^^

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

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

	Modified Compiler Flags
	-----------------------

	Removed Compiler Flags
	-------------------------

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

	- Clang now disallows more than one ``__attribute__((ownership_returns(class, idx)))`` with
	different class names attached to one function.

	- Introduced a new format attribute ``__attribute__((format(syslog, 1, 2)))`` from OpenBSD.

	- The ``hybrid_patchable`` attribute is now supported on ARM64EC targets. It can be used to specify
	that a function requires an additional x86-64 thunk, which may be patched at runtime.

	Improvements to Clang's diagnostics
	-----------------------------------

	- Some template related diagnostics have been improved.

	.. code-block:: c++

	void foo() { template <typename> int i; } // error: templates can only be declared in namespace or class scope

	struct S {
	template <typename> int i; // error: non-static data member 'i' cannot be declared as a template
	};

	- Clang now has improved diagnostics for functions with explicit 'this' parameters. Fixes #GH97878

	- Clang now diagnoses dangling references to fields of temporary objects. Fixes #GH81589.

	- Clang now diagnoses undefined behavior in constant expressions more consistently. This includes invalid shifts, and signed overflow in arithmetic.

	- -Wdangling-assignment-gsl is enabled by default.

	Improvements to Clang's time-trace
	----------------------------------

	Improvements to Coverage Mapping
	--------------------------------

	Bug Fixes in This Version
	-------------------------

	- Fixed the definition of ``ATOMIC_FLAG_INIT`` in ``<stdatomic.h>`` so it can
	be used in C++.

	Bug Fixes to Compiler Builtins
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	Bug Fixes to Attribute Support
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	Bug Fixes to C++ Support
	^^^^^^^^^^^^^^^^^^^^^^^^

	- Fixed a crash when an expression with a dependent ``__typeof__`` type is used as the operand of a unary operator. (#GH97646)
	- Fixed a failed assertion when checking invalid delete operator declaration. (#GH96191)
	- Fix a crash when checking destructor reference with an invalid initializer. (#GH97230)
	- Clang now correctly parses potentially declarative nested-name-specifiers in pointer-to-member declarators.

	Bug Fixes to AST Handling
	^^^^^^^^^^^^^^^^^^^^^^^^^

	Miscellaneous Bug Fixes
	^^^^^^^^^^^^^^^^^^^^^^^

	Miscellaneous Clang Crashes Fixed
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

	- Fixed a crash in C due to incorrect lookup that members in nested anonymous struct/union
	can be found as ordinary identifiers in struct/union definition. (#GH31295)

	OpenACC Specific Changes
	------------------------

	Target Specific Changes
	-----------------------

	AMDGPU Support
	^^^^^^^^^^^^^^

	X86 Support
	^^^^^^^^^^^

	- The MMX vector intrinsic functions from ``*mmintrin.h`` which
	operate on `__m64` vectors, such as ``_mm_add_pi8``, have been
	reimplemented to use the SSE2 instruction-set and XMM registers
	unconditionally. These intrinsics are therefore *no longer
	supported* if MMX is enabled without SSE2 -- either from targeting
	CPUs from the Pentium-MMX through the Pentium 3, or explicitly via
	passing arguments such as ``-mmmx -mno-sse2``. MMX assembly code
	remains supported without requiring SSE2, including inside
	inline-assembly.

	- The compiler builtins such as ``__builtin_ia32_paddb`` which
	formerly implemented the above MMX intrinsic functions have been
	removed. Any uses of these removed functions should migrate to the
	functions defined by the ``*mmintrin.h`` headers. A mapping can be
	found in the file ``clang/www/builtins.py``.

	Arm and AArch64 Support
	^^^^^^^^^^^^^^^^^^^^^^^

	Android Support
	^^^^^^^^^^^^^^^

	Windows Support
	^^^^^^^^^^^^^^^

	LoongArch Support
	^^^^^^^^^^^^^^^^^

	RISC-V Support
	^^^^^^^^^^^^^^

	CUDA/HIP Language Changes
	^^^^^^^^^^^^^^^^^^^^^^^^^

	CUDA Support
	^^^^^^^^^^^^

	AIX Support
	^^^^^^^^^^^

	NetBSD Support
	^^^^^^^^^^^^^^

	WebAssembly Support
	^^^^^^^^^^^^^^^^^^^

	AVR Support
	^^^^^^^^^^^

	DWARF Support in Clang
	----------------------

	Floating Point Support in Clang
	-------------------------------

	Fixed Point Support in Clang
	----------------------------

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

	- Fixed an issue with the `hasName` and `hasAnyName` matcher when matching
	inline namespaces with an enclosing namespace of the same name.

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

	libclang
	--------

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

	New features
	^^^^^^^^^^^^

	- MallocChecker now checks for ``ownership_returns(class, idx)`` and ``ownership_takes(class, idx)``
	attributes with class names different from "malloc". Clang static analyzer now reports an error
	if class of allocation and deallocation function mismatches.
	`Documentation <https://clang.llvm.org/docs/analyzer/checkers.html#unix-mismatcheddeallocator-c-c>`__.

	Crash and bug fixes
	^^^^^^^^^^^^^^^^^^^

	Improvements
	^^^^^^^^^^^^

	- Improved the handling of the ``ownership_returns`` attribute. Now, Clang reports an
	error if the attribute is attached to a function that returns a non-pointer value.
	Fixes (#GH99501)

	Moved checkers
	^^^^^^^^^^^^^^

	.. _release-notes-sanitizers:

	Sanitizers
	----------

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

	OpenMP Support
	--------------

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

	A wide variety of additional information is available on the `Clang web
	page <https://clang.llvm.org/>`_. The web page contains versions of the
	API documentation which are up-to-date with the Git 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 on the `Discourse forums (Clang Frontend category)
	<https://discourse.llvm.org/c/clang/6>`_.