clang/docs/ReleaseNotes.rst

.. If you want to modify sections/contents permanently, you should modify both
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===========================================
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``.

- Clang now correctly rejects ``export`` declarations in module implementation
  partitions. (#GH107602)

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.
- Fixed a number of issues with the ``__regcall`` calling convention for passing
  structs on non-Windows x86-64 targets, including a crash when handling empty
  struct arguments. This changes how structs that contain arrays, floating point
  types, or ``_Complex float`` types are passed, and may introduce
  incompatibilities with code compiled by earlier versions of Clang that uses
  the ``__regcall`` calling convention on these targets. (#GH62999) (#GH98635)

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.
- Colons that appear at the end of a ParamCommentCommand name are not serialized
  as part of the name.

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.
- ``TranslationUnit.get_tokens`` now throws an error if both the ``extent`` and
  ``locations`` argument are passed. Previousy, ``locations`` took precedence.
- ``_CXUnsavedFile`` will be renamed to ``UnsavedFile`` for consistency.
  ``UnsavedFile`` is already available to use and existing uses should
  be adapted to refer to it instead. ``_CXUnsavedFile`` will be removed in a
  future release.

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)

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

- Clang now emits Objective-C number, array, and dictionary literals as
  compile-time constant data structures rather than runtime ``objc_msgSend``
  calls on targets whose runtime supports constant literal classes. The
  feature can be disabled altogether with ``-fno-objc-constant-literals``,
  or selectively per literal kind with ``-fno-constant-nsnumber-literals``,
  ``-fno-constant-nsarray-literals``, and
  ``-fno-constant-nsdictionary-literals``.

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

- Added support for floating point and pointer values in most ``__atomic_``
  builtins.

- 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.
- Implemented the following C23 ``<stdbit.h>`` builtins with ``_BitInt``
  support and constexpr evaluation:
  ``__builtin_stdc_leading_zeros``, ``__builtin_stdc_leading_ones``,
  ``__builtin_stdc_trailing_zeros``, ``__builtin_stdc_trailing_ones``,
  ``__builtin_stdc_first_leading_zero``, ``__builtin_stdc_first_leading_one``,
  ``__builtin_stdc_first_trailing_zero``, ``__builtin_stdc_first_trailing_one``,
  ``__builtin_stdc_count_zeros``, ``__builtin_stdc_count_ones``,
  ``__builtin_stdc_has_single_bit``, ``__builtin_stdc_bit_width``,
  ``__builtin_stdc_bit_floor``, and ``__builtin_stdc_bit_ceil``.

- Implemented the type-specific C23 ``<stdbit.h>`` functions with constexpr
  evaluation support:
  ``stdc_leading_zeros_{uc,us,ui,ul,ull}``,
  ``stdc_leading_ones_{uc,us,ui,ul,ull}``,
  ``stdc_trailing_zeros_{uc,us,ui,ul,ull}``,
  ``stdc_trailing_ones_{uc,us,ui,ul,ull}``,
  ``stdc_first_leading_zero_{uc,us,ui,ul,ull}``,
  ``stdc_first_leading_one_{uc,us,ui,ul,ull}``,
  ``stdc_first_trailing_zero_{uc,us,ui,ul,ull}``,
  ``stdc_first_trailing_one_{uc,us,ui,ul,ull}``,
  ``stdc_count_zeros_{uc,us,ui,ul,ull}``,
  ``stdc_count_ones_{uc,us,ui,ul,ull}``,
  ``stdc_has_single_bit_{uc,us,ui,ul,ull}``,
  ``stdc_bit_width_{uc,us,ui,ul,ull}``,
  ``stdc_bit_floor_{uc,us,ui,ul,ull}``, and
  ``stdc_bit_ceil_{uc,us,ui,ul,ull}``.

- 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``.

- Added header ``endian.h`` which contains byte order helpers specified in POSIX

- Added #pragma loop licm(disable) for llvm.loop.licm.disable metadata

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.

- New option ``-fdiagnostics-show-inlining-chain`` added to show inlining chain
  notes for ``[[gnu::warning]]`` and ``[[gnu::error]]`` diagnostics. When a
  function with these attributes is called from an inlined context, Clang can
  now show which functions were inlined to reach the call. When debug info is
  available (``-gline-directives-only`` (implicitly enabled at ``-g1``) or
  higher), accurate source locations are used; otherwise, a heuristic fallback
  is used with a note suggesting how to enable debug info for better accuracy.

- New option ``-fwin-cfg-mechanism=`` added to control the mechanism used by
  Control Flow Guard on Windows. Accepted values are ``automatic`` (default),
  ``dispatch``, and ``check``. The ``dispatch`` mechanism uses the dispatch
  function to perform indirect call checks and can improve performance, while
  ``check`` uses the traditional check mechanism.
- New ``-cl`` option ``/d2guardcfgdispatch`` added to match MSVC. This acts as a
  shorthand for ``-fwin-cfg-mechanism=dispatch``.
- New ``-cl`` option ``/d2guardcfgdispatch-`` added to match MSVC. This acts as a
  shorthand for ``-fwin-cfg-mechanism=check``.

- New option ``-f[no-]strict-bool`` added to control whether Clang can assume
  that ``bool`` values loaded from memory cannot have a bit pattern other
  than 0 or 1.

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`.

- Introduced a new function attribute ``__attribute__((__personality__(...)))``
  to explicitly specify the personality routine for exception handling. THis is
  meant to be a low level tool for language runtime authors to associate a
  foreign language personality with a given function. Note that this does not
  perform any ABI validation for the personality routine.

- The :doc:`ThreadSafetyAnalysis` attributes ``guarded_by`` and
  ``pt_guarded_by`` now accept multiple capability arguments with refined
  access semantics: *writing* requires all listed capabilities to be held
  exclusively, while *reading* requires at least one to be held.  This is
  sound because any writer must hold all capabilities, so holding any one
  prevents concurrent writes.

- The ``[[clang::unsafe_buffer_usage]]`` attribute is now supported in API
  notes. For example:
  
  .. code-block:: yaml

    Functions:
      - Name: myUnsafeFunction
        UnsafeBufferUsage: true

- Added support for ``[[msvc::forceinline]]`` for functions and
  ``[[msvc::forceinline_calls]]`` for statements. Both are aliases to
  ``[[clang::always_inline]]`` with additional checks to ensure that they
  are only accepted in places where MSVC also does.

- The AMDGPU ``amdgpu_num_sgpr`` and ``amdgpu_num_vgpr`` attributes are now
  deprecated. Clang emits a ``-Wdeprecated-declarations`` warning when they
  are used. Use ``amdgpu_waves_per_eu`` instead to control SGPR and VGPR
  usage.

Improvements to Clang's diagnostics
-----------------------------------
- Fixed bug in ``-Wdocumentation`` so that it correctly handles explicit
  function template instantiations (#64087).

- ``-Wunused-but-set-variable`` now diagnoses file-scope variables with
  internal linkage (``static`` storage class) that are assigned but never used.
  This new coverage is added under the subgroup ``-Wunused-but-set-global``,
  allowing it to be disabled independently with ``-Wno-unused-but-set-global``.
  (#GH148361)

- 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)

- Fixed the Fix-It insertion point for ``expected ';' after alias declaration``
  when parsing alias declarations involving a token-split ``>>`` sequence
  (for example, ``using A = X<int>>;``). (#GH184425)

- Fixed incorrect ``implicitly deleted`` diagnostic for explicitly deleted
  candidate function. (#GH185693)

- 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)

- Added ``-Wmodule-map-path-outside-directory`` (off by default) to warn on
  header and umbrella directory paths that use ``..`` to refer outside the module
  directory in module maps found via implicit search
  (``-fimplicit-module-maps``). This does not affect module maps specified
  explicitly via ``-fmodule-map-file=``.

- Honour ``[[maybe_unused]]`` attribute on private fields.
  ``-Wunused-private-field`` no longer emits a warning for annotated private
  fields.

- Improved ``-Wgnu-zero-variadic-macro-arguments`` to suggest using
  ``__VA_OPT__`` if the current language version supports it(#GH188624)

- Clang now emits an error when implicitly casting a complex type to a built-in vector type. (#GH186805)

- Added ``-Wnonportable-include-path-separator`` (off by default) to catch
  #include directives that use backslashes as a path separator. The warning
  includes a FixIt to change all the backslashes to forward slashes, so that the
  code can automatically be made portable to other host platforms that don't
  support backslashes.

- No longer emitting a ``-Wpre-c2y-compat`` or extension diagnostic about use
  of octal literals with a ``0o`` prefix, and no longer emitting a
  ``-Wdeprecated-octal-literals`` diagnostic for use of octal literals without
  a ``0o`` prefix, when the literal is expanded from a macro defined in a
  system header. (#GH192389)

- Improved error recovery for missing semicolons after class members. Clang now avoids
  skipping subsequent valid declarations when their previous decl is missing semicolon.

- Removed the body of lambdas from some diagnostic messages.

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)
- Correctly handle default template argument when establishing subsumption. (#GH188640)
- 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)
- Fix the result type of a binary operation where both operands are 'void' l-values. (#GH111300)
- 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)
- Fixed a bug with multiple-include optimization (MIOpt) state not being preserved in some cases during lexing, which could suppress header-guard mismatch diagnostics and interfere with include-guard optimization. (#GH180155)
- Fixed a crash when normalizing constraints involving concept template parameters whose index coincided with non-concept template parameters in the same parameter mapping.
- Fixed a crash caused by accessing dependent diagnostics of a non-dependent context.
- Fixed a crash when substituting into a non-type template parameter that has a type containing an undeduced placeholder type.
- Fixed several crashes and improved diagnostics when a multidimensional subscript operator is applied to a built-in type. (#GH187800)
- Correctly diagnosing and no longer crashing when ``export module foo``
  (without a semicolon) are the final tokens in a module file. (#GH187771)
- Fixed a crash in duplicate attribute checking caused by comparing constant arguments with different integer signedness. (#GH188259)
- Clang now emits an error when returning an initializer list from a lambda
  with an explicit return type of void. The diagnostic now correctly refers
  to "lambda" instead of "block". (#GH188661)
- Fixed a crash on _BitInt(N) arrays where 129 ≤ N ≤ 192 due to incorrect array filler lowering. (#GH189643)
- Fixed the behavior in C23 of ``auto``, by emitting an error when an array type is specified for a ``char *``. (#GH162694)
- Fixed an issue where an assert was thrown instead of an error if no vulkan env was specified with ``--triple spirv``. (#GH189964)
- Fixed incorrect rejection of ``auto`` with reordered declaration specifiers in C23. (#GH164121)
- Fixed a crash where constexpr evaluation encountered invalid overrides. (#GH183290)
- Fixed a crash when assigning to an element of an ``ext_vector_type`` with ``bool`` element type. (#GH189260)
- Clang now emits an error for friend declarations of lambda members. (#GH26540)

Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Fix a crash when passing an unresolved overload set to ``__builtin_classify_type``. (#GH175589)
- Fixed a crash when calling `__builtin_allow_sanitize_check` with no arguments. (#GH183927)

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 when a function template is defined as a non-template friend with a global scope qualifier. (#GH185341)
- Clang now rejects constant template parameters with block pointer types, since these are not implemented anyway and would lead to crashes. (#GH189247)
- 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)
- We no longer caches invalid variable specializations. (#GH132592)
- Fixed an incorrect template argument deduction when matching packs of template
  template parameters when one of its parameters is also a pack. (#GH181166)
- Clang no longer errors on overloads with different ref-qualifiers and constraints. (#GH120812)
- Fixed a crash when a default argument is passed to an explicit object parameter. (#GH176639)
- Fixed an alias template CTAD crash.
- Correctly diagnose uses of ``co_await`` / ``co_yield`` in the default argument of nested function declarations. (#GH98923)
- Fixed a crash when diagnosing an invalid static member function with an explicit object parameter (#GH177741)
- Clang incorrectly instantiated variable specializations outside of the immediate context. (#GH54439)
- Fixed a bug matching constrained out-of-line definitions of class members.
- Fixed a crash when instantiating an invalid out-of-line static data member definition in a local class. (#GH176152)
- Fixed a crash when pack expansions are used as arguments for non-pack parameters of built-in templates. (#GH180307)
- Fix a problem where pack index expressions where incorrectly being regarded as equivalent.
- 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 when `explicit(bool)` is used with an incomplete enumeration. (#GH183887)
- Fixed a crash on ``typeid`` of incomplete local types during template instantiation. (#GH63242), (#GH176397)
- Fixed a crash when an immediate-invoked ``consteval`` lambda is used as an invalid initializer. (#GH185270)
- Fixed an assertion failure when using a global destructor with a target with a non-default program address space. (#GH186484)

- Inherited constructors in ``dllexport`` classes are now exported for ABI-compatible cases, matching
  MSVC behavior. Constructors with variadic arguments or callee-cleanup parameters are not yet supported
  and produce a warning. (#GH162640)
- Correctly diagnose invalid non-dependent calls in dependent contexts. (#GH135694)
- Fix initialization of GRO when GRO-return type mismatches, as part of CWG2563. (#GH98744)
- Fix an error using an initializer list with array new for a type that is not default-constructible. (#GH81157)
- We no longer consider conversion operators when copy-initializing from the same type. This was non
  conforming and could lead to recursive constraint satisfaction checking. (#GH149443)
- Fixed a crash in Itanium C++ name mangling for a lambda in a local class field initializer inside a constructor/destructor. (#GH176395)

Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed a bug where explicit nullability property attributes were not stored in AST nodes in Objective-C. (#GH179703)
- Fixed a crash when parsing Doxygen ``@param`` commands attached to invalid declarations or non-function entities. (#GH182737)
- Fixed the SourceLocation and SourceRange of reversed rewritten CXXOperatorCallExpr. (#GH192467)

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 related to missing source locations (#GH186655)
- 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)
- Fixed a crash when attempting to diagnose incompatible conversions involving function types (#GH182534)
- Fixed a crash when evaluating ``__is_bitwise_cloneable`` on invalid record types. (#GH183707)
- Fixed an assertion failure when casting a function pointer with a target with a non-default program address space. (#GH186210)
- Fixed a crash when ``decltype(__builtin_FUNCTION())`` is used as a template type argument. (#GH167433)
- Fixed an assertion failure when parsing an invalid ``decltype`` specifier with missing parentheses or extra semicolons. (#GH188014)
- Fixed a crash when explicitly casting a complex type to or from an atomic complex type. (#GH172208)
- Fixed a crash when explicitly casting a scalar to an atomic complex. (#GH114885)
- Fixed an assertion failure when parsing an invalid out-of-line enum definition with template parameters. (#GH187909)
- Fixed an assertion failure on invalid template template parameter during typo correction. (#GH183983)
- Fixed an assertion failure in ``isAtEndOfMacroExpansion`` on macro expansions crossing the boundary of two fileIDs. (#GH115007), (#GH21755)

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

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

AMDGPU Support
^^^^^^^^^^^^^^
- Introduced a new target specific builtin ``__builtin_amdgcn_processor_is``,
  a late / deferred query for the current target processor.
- Introduced a new target specific builtin ``__builtin_amdgcn_is_invocable``,
  a late / deferred query for the availability of target specific builtins.
- Initial support for gfx1310
- The ``amdgpu_num_sgpr`` and ``amdgpu_num_vgpr`` function attributes are now
  deprecated. Using them produces a ``-Wdeprecated-declarations`` warning. Use
  ``amdgpu_waves_per_eu`` instead.

NVPTX Support
^^^^^^^^^^^^^^

X86 Support
^^^^^^^^^^^
- ``march=znver6`` is now supported.

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

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

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

- Clang now defines the ``_MSVC_TRADITIONAL`` macro as ``1`` when emulating MSVC
  19.15 (Visual Studio 2017 version 15.8) and later. (#GH47114)

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`.
- Intrinsics were added for the 'Zvabd` (RISC-V Integer Vector Absolute Difference) extension.
- Intrinsics were added for the 'Zvzip` (Reordering Structured Data in Vector Registers) extension.

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
^^^^^^^^^^^

- The driver default for the linker flag `-bcdtors` now defaults to `mbr`
  (instead of `all`) which only extracts static init from archive members which
  would otherwise be referenced.
  (See https://www.ibm.com/docs/en/aix/7.2.0?topic=l-ld-command for details).

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
- Deprecate the ``BinPackParameters`` and ``BinPackArguments`` options and replace 
  them with the ``PackParameters`` and ``PackArguments`` structs (respectively) to 
  unify packing behavior. Add the ``BreakAfter`` option to the structs, allowing 
  parameter and argument lists to be formatted with one parameter/argument on each 
  line if they exceed the specified count.
- 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``.
- Add ``AllowShortRecordOnASingleLine`` option and set it to ``EmptyAndAttached`` for LLVM style.

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
- The clang_Module_getASTFile API is deprecated and now always returns nullptr

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``.
- Added a new helper method ``get_clang_version`` to the class ``Config`` to
  read the version string of the libclang in use.

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
^^^^^^^^^^^^
- Improved substitution performance in concept checking. (#GH172266)

- Clang now preserves the left-hand side of a binary expression (such as an
  assignment or comparison) in a ``RecoveryExpr`` when the right-hand side fails
  to parse. This improves IDE features like go-to-definition in ``clangd``.

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>`_.