feat: support LLVM 23

[shenxianpeng]

Adds 23 to the accepted version values and to the self-test matrix, now that clang-tools-static-binaries ships the LLVM 23 builds.

Changes

• action.yml — 23 added to the accepted version values
• .github/workflows/self-test.yml — '23' added to the clang-version matrix

That is the whole diff. No change to the installation steps was needed, because every path already resolves 23:

Path	Status
clang-tools (fallback, all platforms)	1.3.0 raises MAX_VERSION to 23 and pins the 2026.09.01-5fb8802d binary release that carries the 23 builds. Already on main via #477.
apt.llvm.org (Linux)	llvm.sh carries LLVM_VERSION_PATTERNS[23]="-23".
Homebrew (macOS)	llvm@23 is an alias of the current llvm formula (23.1.1), so brew install llvm@23 resolves.

Verification

Installed and ran the tools through the dependency set this repo locks:

$ uv run --group action clang-tools install clang-format clang-tidy --version 23
Downloading clang-format (version 23)
Installing clang-format-23 to ...
Downloading clang-tidy (version 23)
Installing clang-tidy-23 to ...

$ ./clang-format-23 --version
clang-format version 23.1.0

$ ./clang-tidy-23 --version
LLVM version 23.1.0

mkdocs build regenerates the inputs doc with the updated list, and both YAML files parse.

Note for review

The default version stays at 21 — bumping it is a separate call, so I left it out. Historically it has trailed the newest release by one or two (18 → 20 when 22 landed in #398, then 20 → 21 in #458). Happy to bump it to 22 here if you'd rather keep that cadence.

The matrix now runs 12 through 23 (12 versions × 3 OS). Earlier releases dropped the oldest entry when adding a new one (#398 dropped 9 and 10, #458 dropped 11), but clang-tools still declares MIN_VERSION = 12, so nothing is forced out yet.

Summary by CodeRabbit

• New Features
  • Added support for Clang Tools version 23.
  • Updated the version input guidance to include version 23.
• Tests
  • Extended automated testing to cover Clang Tools version 23.

[github-actions]

Cpp-Linter Report ⚠️

Some files did not pass the configured checks!

clang-format (v16.0.6) reports: 2 file(s) not formatted

• docs/examples/demo/demo.hpp
• docs/examples/demo/demo.cpp

clang-tidy (v16.0.6) reports: 7 concern(s)

• docs/examples/demo/demo.hpp:6:11: warning: [modernize-use-default-member-init]

  use default member initializer for 'useless'

      char* useless;
            ^
                   {"\0"}

• docs/examples/demo/demo.hpp:7:9: warning: [modernize-use-default-member-init]

  use default member initializer for 'numb'

      int numb;
          ^
              {0}

• docs/examples/demo/demo.hpp:11:11: warning: [modernize-use-trailing-return-type]

  use a trailing return type for this function

      void *not_useful(char *str){useless = str;}
      ~~~~~~^
      auto                        -> void *

• docs/examples/demo/demo.cpp:3:10: warning: [modernize-deprecated-headers]

  inclusion of deprecated C++ header 'stdio.h'; consider using 'cstdio' instead

  #include <stdio.h>
           ^~~~~~~~~
           <cstdio>

• docs/examples/demo/demo.cpp:8:5: warning: [modernize-use-trailing-return-type]

  use a trailing return type for this function

  int main(){
  ~~~ ^
  auto       -> int

• docs/examples/demo/demo.cpp:10:13: warning: [readability-braces-around-statements]

  statement should be inside braces

      for (;;) break;
              ^
               {

• docs/examples/demo/demo.cpp:13:5: warning: [cppcoreguidelines-pro-type-vararg]

  do not call c-style vararg functions

      printf("Hello world!\n");
      ^

Have any feedback or feature suggestions? Share it here.

[coderabbitai]

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Reviewing files that changed from the base of the PR and between 32e4c65 and 375609b.

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• .github/workflows/self-test.yml
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Walkthrough

Changes

Clang 23 support

Layer / File(s)	Summary
Version metadata and validation .github/workflows/self-test.yml, action.yml	The self-test matrix adds clang version 23. The version input description lists 23 as an accepted clang-tools version.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 37560

The PR adds LLVM 23 to the accepted versions and self-test matrix without changing installation behavior.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding LLVM 23 support.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[shenxianpeng]

Maybe support LLVM 23 first to release a minor release, then move to auto-fix as a minor release if it works as expected.