Clang 15 |ReleaseNotesTitle|

Written by the LLVM Team

Introduction

This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 15. 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

These changes are ones which we think may surprise users when upgrading to Clang 15 because of the opportunity they pose for disruption to existing code bases.

What’s New in Clang 15?

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++20 Feature Support

C++23 Feature Support

C++2c Feature Support

Resolutions to C++ Defect Reports

C Language Changes

C2x Feature Support

Bug Fixes in This Version

  • Fixed an issue where a class template specialization whose declaration is instantiated in one module and whose definition is instantiated in another module may end up with members associated with the wrong declaration of the class, which can result in miscompiles in some cases.

Bug Fixes to Compiler Builtins

Bug Fixes to Attribute Support

Bug Fixes to C++ Support

  • Clang limits the size of arrays it will try to evaluate at compile time to avoid memory exhaustion. This limit can be modified by -fconstexpr-steps. (#63562)
  • Fix a crash caused by some named unicode escape sequences designating a Unicode character whose name contains a -. (Fixes #64161 <https://github.com/llvm/llvm-project/issues/64161>_)
  • Fix cases where we ignore ambiguous name lookup when looking up memebers. (#22413 <https://github.com/llvm/llvm-project/issues/22413>_), (#29942 <https://github.com/llvm/llvm-project/issues/29942>_), (#35574 <https://github.com/llvm/llvm-project/issues/35574>_) and (#27224 <https://github.com/llvm/llvm-project/issues/27224>_).

Bug Fixes to AST Handling

Miscellaneous Bug Fixes

Miscellaneous Clang Crashes Fixed

Target Specific Changes

AMDGPU Support

X86 Support

Arm and AArch64 Support

Windows Support

LoongArch Support

  • The -march=native -mtune= options and __loongarch_{arch,tune} macros are now supported.

RISC-V Support

CUDA/HIP Language Changes

CUDA Support

AIX Support

WebAssembly Support

AVR Support

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).