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llvm-project/clang/docs/ReleaseNotes.rst
YunQiang Su 5f22decefa
Clang: Deprecate float support from __builtin_elementwise_max (#180885) 
Now we have
  __builtin_elementwise_maxnum
  __builtin_elementwise_maximum
  __builtin_elementwise_maximumnum
2026-02-28 10:56:02 +08:00

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.. If you want to modify sections/contents permanently, you should modify both
ReleaseNotes.rst and ReleaseNotesTemplate.txt.
===========================================
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
============================
C/C++ Language Potentially Breaking Changes
-------------------------------------------
C++ Specific Potentially Breaking Changes
-----------------------------------------
- Clang now more aggressively optimizes away stores to objects after they are
dead. This behavior can be disabled with ``-fno-lifetime-dse``.
ABI Changes in This Version
---------------------------
- Fixed incorrect struct layout for ``_BitInt`` bitfields wider than 255 bits
on MSVC targets. Internal bitfield tracking fields were changed from
``unsigned char`` to ``uint64_t`` to prevent overflow. This might be an ABI
break for such structs compared to earlier Clang versions.
AST Dumping Potentially Breaking Changes
----------------------------------------
- The JSON AST dump now includes all fields from ``AvailabilityAttr``: ``platform``,
``introduced``, ``deprecated``, ``obsoleted``, ``unavailable``, ``message``,
``strict``, ``replacement``, ``priority``, and ``environment``. Previously, these
fields were missing from the JSON output.
Clang Frontend Potentially Breaking Changes
-------------------------------------------
- HIPSPV toolchain: `--offload-targets=spirv{32,64}` option is
deprecated and will be removed when the new offload driver becomes
default. The replacement for the option is
`--offload-targets=spirv{32,64}-unknown-chipstar` when using the new
offload driver (`--offload-new-driver`).
- The new driver (`--offload-new-driver`) is now default for all offloading
compilations. This changes the ABI for relocatable device code. Currently,
libraries will need to be recompiled, or used with
(`--no-offload-new-driver`). This option will be removed in the next release.
Clang Python Bindings Potentially Breaking Changes
--------------------------------------------------
- Remove ``CompletionString.Availability``. No libclang interfaces returned instances of it.
- ``CompletionString.availability`` now returns instances of ``CompletionString.AvailabilityKindCompat``.
Instances of ``AvailabilityKindCompat`` have the same ``__str__`` representation
as the previous ``CompletionChunk.Kind`` and are equality-comparable with
the existing ``AvailabilityKind`` enum. It will be replaced by ``AvailabilityKind``
in a future release. When this happens, the return type of ``CompletionString.availability``
will change to ``AvailabilityKind``, so it is recommended to use ``AvailabilityKind``
to compare with the return values of ``CompletionString.availability``.
- Remove ``availabilityKinds``. In this release, uses of ``availabilityKinds``
need to be replaced by ``CompletionString.AvailabilityKind``.
- ``CompletionChunk.kind`` now returns instances of ``CompletionChunkKind``.
Instances of ``CompletionChunkKind`` have the same ``__str__`` representation
as the previous ``CompletionChunk.Kind`` for compatibility.
These representations will be changed in a future release to match other enums.
- Remove ``completionChunkKindMap``. In this release, uses of ``completionChunkKindMap``
need to be replaced by ``CompletionChunkKind``.
- Move ``SPELLING_CACHE`` into ``CompletionChunk`` and change it to use
``CompletionChunkKind`` instances as keys, instead of the enum values.
An alias is kept in the form of a ``SPELLING_CACHE`` variable, but it only supports
``__getitem__`` and ``__contains__``. It will be removed in a future release.
Please migrate to using ``CompletionChunk.SPELLING_CACHE`` instead.
- ``SourceLocation`` and ``SourceRange`` now use ``NotImplemented`` to delegate
equality checks (``__eq__``) to the other object they are compared with when
they are of different classes. They previously returned ``False`` when compared
with objects of other classes.
What's New in Clang |release|?
==============================
C++ Language Changes
--------------------
- ``__is_trivially_equality_comparable`` no longer returns false for all enum types. (#GH132672)
C++2c Feature Support
^^^^^^^^^^^^^^^^^^^^^
C++23 Feature Support
^^^^^^^^^^^^^^^^^^^^^
C++20 Feature Support
^^^^^^^^^^^^^^^^^^^^^
- Clang now supports `P1857R3 <https://wg21.link/p1857r3>`_ Modules Dependency Discovery. (#GH54047)
C++17 Feature Support
^^^^^^^^^^^^^^^^^^^^^
Resolutions to C++ Defect Reports
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
C Language Changes
------------------
C2y Feature Support
^^^^^^^^^^^^^^^^^^^
C23 Feature Support
^^^^^^^^^^^^^^^^^^^
- Clang now allows C23 ``constexpr`` struct member access through the dot operator in constant expressions. (#GH178349)
Non-comprehensive list of changes in this release
-------------------------------------------------
- Added ``__builtin_stdc_rotate_left`` and ``__builtin_stdc_rotate_right``
for bit rotation of unsigned integers including ``_BitInt`` types. Rotation
counts are normalized modulo the bit-width and support negative values.
Usable in constant expressions. Implicit conversion is supported for
class/struct types with conversion operators.
- A new generic bit-reverse builtin function ``__builtin_bitreverseg`` that
extends bit-reversal support to all standard integers type, including
``_BitInt``
- Deprecated float types support from ``__builtin_elementwise_max`` and
``__builtin_elementwise_min``.
New Compiler Flags
------------------
- New option ``-fms-anonymous-structs`` / ``-fno-ms-anonymous-structs`` added
to enable or disable Microsoft's anonymous struct/union extension without
enabling other ``-fms-extensions`` features (#GH177607).
- New option ``--precompile-reduced-bmi`` allows build system to generate a
reduced BMI only for a C++20 importable module unit. Previously the users
can only generate the reduced BMI as a by-product, e.g, an object files or
a full BMI.
- New ``-cc1`` option ``-fexperimental-overflow-behavior-types`` added to
enable parsing of the experimental ``overflow_behavior`` type attribute and
type specifiers.
- New ``-cl`` option ``/d2guardnochecks`` added to match MSVC. When Windows
Control Flow Guard (CFG) is enabled by other options, it will instruct Clang
to emit the CFG metadata, but disable adding checks.
Deprecated Compiler Flags
-------------------------
Modified Compiler Flags
-----------------------
- The `-mno-outline` and `-moutline` compiler flags are now allowed on RISC-V and X86, which both support the machine outliner.
- The `-mno-outline` flag will now add the `nooutline` IR attribute, so that
`-mno-outline` and `-moutline` objects can be mixed correctly during LTO.
Removed Compiler Flags
----------------------
Attribute Changes in Clang
--------------------------
- Added new attribute ``stack_protector_ignore`` to opt specific local variables out of
the analysis which determines if a function should get a stack protector. A function
will still generate a stack protector if other local variables or command line flags
require it.
- Added a new attribute, ``[[clang::no_outline]]`` to suppress outlining from
annotated functions. This uses the LLVM `nooutline` attribute.
- Introduced a new type attribute ``__attribute__((overflow_behavior))`` which
currently accepts either ``wrap`` or ``trap`` as an argument, enabling
type-level control over overflow behavior. There is also an accompanying type
specifier for each behavior kind via `__ob_wrap` and `__ob_trap`.
Improvements to Clang's diagnostics
-----------------------------------
- Added ``-Wlifetime-safety`` to enable lifetime safety analysis,
a CFG-based intra-procedural analysis that detects use-after-free and related
temporal safety bugs. See the
`RFC <https://discourse.llvm.org/t/rfc-intra-procedural-lifetime-analysis-in-clang/86291>`_
for more details. By design, this warning is enabled in ``-Weverything``. To disable
the analysis, use ``-Wno-lifetime-safety`` or ``-fno-lifetime-safety``.
- Added ``-Wlifetime-safety-suggestions`` to enable lifetime annotation suggestions.
This provides suggestions for function parameters that
should be marked ``[[clang::lifetimebound]]`` based on lifetime analysis. For
example, for the following function:
.. code-block:: c++
int* p(int *in) { return in; }
Clang will suggest:
.. code-block:: c++
warning: parameter in intra-TU function should be marked [[clang::lifetimebound]]
int* p(int *in) { return in; }
^~~~~~~
[[clang::lifetimebound]]
note: param returned here
int* p(int *in) { return in; }
^~
- Added ``-Wlifetime-safety-noescape`` to detect misuse of ``[[clang::noescape]]``
annotation where the parameter escapes through return. For example:
.. code-block:: c++
int* p(int *in [[clang::noescape]]) { return in; }
Clang will warn:
.. code-block:: c++
warning: parameter is marked [[clang::noescape]] but escapes
int* p(int *in [[clang::noescape]]) { return in; }
^~~~~~~
note: returned here
int* p(int *in [[clang::noescape]]) { return in; }
^~
- Added ``-Wlifetime-safety-dangling-field`` to detect dangling field references
when stack memory escapes to class fields. This is part of ``-Wlifetime-safety``
and detects cases where local variables or parameters are stored in fields but
outlive their scope. For example:
.. code-block:: c++
struct DanglingView {
std::string_view view;
DanglingView(std::string s) : view(s) {} // warning: address of stack memory escapes to a field
};
- Improved ``-Wassign-enum`` performance by caching enum enumerator values. (#GH176454)
- Fixed a false negative in ``-Warray-bounds`` where the warning was suppressed
when accessing a member function on a past-the-end array element.
(#GH179128)
- Added a missing space to the FixIt for the ``implicit-int`` group of diagnostics and
made sure that only one such diagnostic and FixIt is emitted per declaration group. (#GH179354)
- The ``-Wloop-analysis`` warning has been extended to catch more cases of
variable modification inside lambda expressions (#GH132038).
- Clang now emits ``-Wsizeof-pointer-memaccess`` when snprintf/vsnprintf use the sizeof
the destination buffer(dynamically allocated) in the len parameter(#GH162366)
Improvements to Clang's time-trace
----------------------------------
Improvements to Coverage Mapping
--------------------------------
- [MC/DC] Nested expressions are handled as individual MC/DC expressions.
- "Single byte coverage" now supports branch coverage and can be used
together with ``-fcoverage-mcdc``.
Bug Fixes in This Version
-------------------------
- Fixed atomic boolean compound assignment; the conversion back to atomic bool would be miscompiled. (#GH33210)
- Fixed a failed assertion in the preprocessor when ``__has_embed`` parameters are missing parentheses. (#GH175088)
- Fix lifetime extension of temporaries in for-range-initializers in templates. (#GH165182)
- Fixed a preprocessor crash in ``__has_cpp_attribute`` on incomplete scoped attributes. (#GH178098)
- Fixes an assertion failure when evaluating ``__underlying_type`` on enum redeclarations. (#GH177943)
- Fixed an assertion failure caused by nested macro expansion during header-name lexing (``__has_embed(__has_include)``). (#GH178635)
- Clang now outputs relative paths of embeds for dependency output. (#GH161950)
- Fixed an assertion failure when evaluating ``_Countof`` on invalid ``void``-typed operands. (#GH180893)
- Fixed an assertion failure in the serialized diagnostic printer when it is destroyed without calling ``finish()``. (#GH140433)
- Fixed an assertion failure caused by error recovery while extending a nested name specifier with results from ordinary lookup. (#GH181470)
- Fixed a crash when parsing ``#pragma clang attribute`` arguments for attributes that forbid arguments. (#GH182122)
Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Bug Fixes to Attribute Support
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed a behavioral discrepancy between deleted functions and private members when checking the ``enable_if`` attribute. (#GH175895)
- Fixed ``init_priority`` attribute by delaying type checks until after the type is deduced.
Bug Fixes to C++ Support
^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed a crash on error recovery when dealing with invalid templates. (#GH183075)
- Fixed a crash when instantiating ``requires`` expressions involving substitution failures in C++ concepts. (#GH176402)
- Fixed an incorrect template argument deduction when matching packs of template
template parameters when one of its parameters is also a pack. (#GH181166)
- Fixed a crash when a default argument is passed to an explicit object parameter. (#GH176639)
- Fixed a crash when diagnosing an invalid static member function with an explicit object parameter (#GH177741)
- Fixed a bug where captured variables in non-mutable lambdas were incorrectly treated as mutable
when used inside decltype in the return type. (#GH180460)
- Fixed a crash when evaluating uninitialized GCC vector/ext_vector_type vectors in ``constexpr``. (#GH180044)
- Fixed a crash on ``typeid`` of incomplete local types during template instantiation. (#GH63242), (#GH176397)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed a bug where explicit nullability property attributes were not stored in AST nodes in Objective-C. (#GH179703)
Miscellaneous Bug Fixes
^^^^^^^^^^^^^^^^^^^^^^^
- Fixed the arguments of the format attribute on ``__builtin_os_log_format``. Previously, they were off by 1.
Miscellaneous Clang Crashes Fixed
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed a crash when attempting to jump over initialization of a variable with variably modified type. (#GH175540)
- Fixed a crash when using loop hint with a value dependent argument inside a
generic lambda. (#GH172289)
- Fixed a crash in C++ overload resolution with ``_Atomic``-qualified argument types. (#GH170433)
- Fixed a crash when casting a parenthesized unresolved template-id or array section. (#GH183505)
- Fixed a crash when initializing a ``constexpr`` pointer with a floating-point literal in C23. (#GH180313)
- Fixed an assertion when diagnosing address-space qualified ``new``/``delete`` in language-defined address spaces such as OpenCL ``__local``. (#GH178319)
- Fixed an assertion failure in ObjC++ ARC when binding a rvalue reference to reference with different lifetimes (#GH178524)
- Fixed a crash when subscripting a vector type with large unsigned integer values. (#GH180563)
OpenACC Specific Changes
------------------------
Target Specific Changes
-----------------------
AMDGPU Support
^^^^^^^^^^^^^^
- Initial support for gfx1310
NVPTX Support
^^^^^^^^^^^^^^
X86 Support
^^^^^^^^^^^
- ``march=znver6`` is now supported.
Arm and AArch64 Support
^^^^^^^^^^^^^^^^^^^^^^^
Android Support
^^^^^^^^^^^^^^^
Windows Support
^^^^^^^^^^^^^^^
LoongArch Support
^^^^^^^^^^^^^^^^^
- DWARF fission is now compatible with linker relaxations, allowing `-gsplit-dwarf` and `-mrelax`
to be used together when building for the LoongArch platform.
RISC-V Support
^^^^^^^^^^^^^^
- Tenstorrent Ascalon D8 was renamed to Ascalon X. Use `tt-ascalon-x` with `-mcpu` or `-mtune`.
CUDA/HIP Language Changes
^^^^^^^^^^^^^^^^^^^^^^^^^
- The new offloading driver is now the default for HIP. Use
`--no-oflfoad-new-driver` to return to the old behavior.
CUDA Support
^^^^^^^^^^^^
AIX Support
^^^^^^^^^^^
NetBSD Support
^^^^^^^^^^^^^^
WebAssembly Support
^^^^^^^^^^^^^^^^^^^
- Fixed a crash when ``__funcref`` is applied to a non-function pointer type.
(#GH118233)
AVR Support
^^^^^^^^^^^
SystemZ Support
^^^^^^^^^^^^^^^
- Add support for `#pragma export` for z/OS. This is a pragma used to export functions and variables
with external linkage from shared libraries. It provides compatibility with the IBM XL C/C++
compiler.
DWARF Support in Clang
----------------------
Floating Point Support in Clang
-------------------------------
Fixed Point Support in Clang
----------------------------
AST Matchers
------------
- Add ``functionTypeLoc`` matcher for matching ``FunctionTypeLoc``.
- Add missing support for ``TraversalKind`` in some ``addMatcher()`` overloads.
clang-format
------------
- Add ``ObjCSpaceAfterMethodDeclarationPrefix`` option to control space between the
'-'/'+' and the return type in Objective-C method declarations
- Add ``AfterComma`` value to ``BreakConstructorInitializers`` to allow breaking
constructor initializers after commas, keeping the colon on the same line.
- Extend ``BreakBinaryOperations`` to accept a structured configuration with
per-operator break rules and minimum chain length gating via ``PerOperator``.
libclang
--------
- Visit constraints of `auto` type to properly visit concept usages (#GH166580)
- Visit switch initializer statements (https://bugs.kde.org/show_bug.cgi?id=415537#c2)
- Fix crash in clang_getBinaryOperatorKindSpelling and clang_getUnaryOperatorKindSpelling
Code Completion
---------------
- Fixed a crash in code completion when using a C-Style cast with a parenthesized
operand in Objective-C++ mode. (#GH180125)
Static Analyzer
---------------
.. comment:
This is for the Static Analyzer.
Using the caret `^^^` underlining for subsections:
- Crash and bug fixes
- New checkers and features
- Improvements
- Moved checkers
.. _release-notes-sanitizers:
Sanitizers
----------
Python Binding Changes
----------------------
- Add deprecation warnings to ``CompletionChunk.isKind...`` methods.
These will be removed in a future release. Existing uses should be adapted
to directly compare equality of the ``CompletionChunk`` kind with
the corresponding ``CompletionChunkKind`` variant.
Affected methods: ``isKindOptional``, ``isKindTypedText``, ``isKindPlaceHolder``,
``isKindInformative`` and ``isKindResultType``.
- Add a deprecation warning to ``CodeCompletionResults.results``.
This property will become an implementation detail with changed behavior in a
future release and should not be used directly.. Existing uses of
``CodeCompletionResults.results`` should be changed to directly use
``CodeCompletionResults``: it nows supports ``__len__`` and ``__getitem__``,
so it can be used the same as ``CodeCompletionResults.results``.
OpenMP Support
--------------
- Added support for ``transparent`` clause in task and taskloop directives.
- Added support for ``use_device_ptr`` clause to accept an optional
``fallback`` modifier (``fb_nullify`` or ``fb_preserve``) with OpenMP >= 61.
Improvements
^^^^^^^^^^^^
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>`_.
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