Clang 13.0.0 (In-Progress) Release Notes

Written by the LLVM Team


These are in-progress notes for the upcoming Clang 13 release. Release notes for previous releases can be found on the Download Page.


This document contains the release notes for the Clang C/C++/Objective-C frontend, part of the LLVM Compiler Infrastructure, release 13.0.0. 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. 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.

Note that if you are reading this file from a Git checkout or the main Clang web page, this document applies to the next release, not the current one. To see the release notes for a specific release, please see the releases page.

What’s New in Clang 13.0.0?

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.

Major New Features

Improvements to Clang’s diagnostics

Modified Compiler Flags

  • -Wshadow now also checks for shadowed structured bindings

Removed Compiler Flags

  • The clang-cl /fallback flag, which made clang-cl invoke Microsoft Visual C++ on files it couldn’t compile itself, has been removed.
  • -Wreturn-std-move-in-c++11, which checked whether an entity is affected by CWG1579 to become implicitly movable, has been removed.

C++ Language Changes in Clang

C++1z Feature Support

Internal API Changes

These are major API changes that have happened since the 12.0.0 release of Clang. If upgrading an external codebase that uses Clang as a library, this section should help get you past the largest hurdles of upgrading.

Build System Changes

These are major changes to the build system that have happened since the 12.0.0 release of Clang. Users of the build system should adjust accordingly.


  • Option SpacesInLineCommentPrefix has been added to control the number of spaces in a line comments prefix.

  • Option SortIncludes has been updated from a bool to an enum with backwards compatibility. In addition to the previous true/false states (now CaseInsensitive/Never), a third state has been added (CaseSensitive) which causes an alphabetical sort with case used as a tie-breaker.

    // Never (previously false)
    #include "B/A.h"
    #include "A/B.h"
    #include "a/b.h"
    #include "A/b.h"
    #include "B/a.h"
    // CaseInsensitive (previously true)
    #include "A/B.h"
    #include "A/b.h"
    #include "B/A.h"
    #include "B/a.h"
    #include "a/b.h"
    // CaseSensitive
    #include "A/B.h"
    #include "A/b.h"
    #include "a/b.h"
    #include "B/A.h"
    #include "B/a.h"
  • BasedOnStyle: InheritParentConfig allows to use the .clang-format of the parent directories to overwrite only parts of it.

  • Option IndentAccessModifiers has been added to be able to give access modifiers their own indentation level inside records.

New Issues Found

Python Binding Changes

The following methods have been added:

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 via the mailing list.