Clang 23.0.0git (In-Progress) Release Notes¶

Written by the LLVM Team

Warning

These are in-progress notes for the upcoming Clang 23 release. Release notes for previous releases can be found on the Releases Page.

Introduction ¶

This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 23.0.0git. 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. For the libc++ release notes, see this page. All LLVM releases may be downloaded from the LLVM releases web site.

For more information about Clang or LLVM, including information about the latest release, please see the Clang Web Site or the LLVM Web Site.

Potentially Breaking Changes ¶

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 ¶

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.

What’s New in Clang 23.0.0git?¶

C++ Language Changes ¶

C++2c Feature Support¶

C++23 Feature Support¶

C++20 Feature Support¶

Clang now supports P1857R3 Modules Dependency Discovery. (#54047)

C++17 Feature Support¶

Resolutions to C++ Defect Reports¶

C Language Changes ¶

C2y Feature Support¶

C23 Feature Support¶

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.

New Compiler Flags ¶

Deprecated Compiler Flags ¶

Modified Compiler Flags ¶

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.

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 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:

int* p(int *in) { return in; }

Clang will suggest:

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:

int* p(int *in [[clang::noescape]]) { return in; }

Clang will warn:

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:
```
struct DanglingView {
  std::string_view view;
  DanglingView(std::string s) : view(s) {}  // warning: address of stack memory escapes to a field
};
```

Improvements to Clang’s time-trace ¶

Improvements to Coverage Mapping ¶

Bug Fixes in This Version ¶

Fixed a failed assertion in the preprocessor when __has_embed parameters are missing parentheses. (#175088)
Fix lifetime extension of temporaries in for-range-initializers in templates. (#165182)
Fixed a preprocessor crash in __has_cpp_attribute on incomplete scoped attributes. (#178098)

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. (#175895)

Bug Fixes to C++ Support¶

Fixed a crash when instantiating requires expressions involving substitution failures in C++ concepts. (#176402)

Bug Fixes to AST Handling¶

Miscellaneous Bug Fixes¶

Miscellaneous Clang Crashes Fixed¶

Fixed a crash when attempting to jump over initialization of a variable with variably modified type. (#175540)
Fixed a crash when using loop hint with a value dependent argument inside a generic lambda. (#172289)
Fixed a crash in C++ overload resolution with _Atomic-qualified argument types. (#170433)

OpenACC Specific Changes ¶

Target Specific Changes ¶

AMDGPU Support¶

Initial support for gfx1310

NVPTX Support¶

X86 Support¶

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¶

CUDA Support¶

AIX Support¶

NetBSD Support¶

WebAssembly Support¶

Fixed a crash when __funcref is applied to a non-function pointer type. (#118233)

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.

clang-format ¶

Add ObjCSpaceAfterMethodDeclarationPrefix option to control space between the ‘-‘/’+’ and the return type in Objective-C method declarations

libclang ¶

Code Completion ¶

Static Analyzer ¶

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.

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. 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).