Building on windows-latest sporadically has random LLVM version for bindgen

[vlovich]

Description

When I run Rust's bindgen on windows-latest, sometimes the reported version is 18.1 and sometimes it's 19.

The bindgen tool fails with:

  Failed to generate bindings: ClangDiagnostic("C:\\Program Files\\Microsoft Visual Studio\\2022\\Enterprise\\VC\\Tools\\MSVC\\14.44.35207\\include\\yvals_core.h:908:1: error: static assertion failed: error STL1000: Unexpected compiler version, expected Clang 19.0.0 or newer.\n")

because the headers in MSVC are newer than the last supported version of clang. This started sporadically breaking recently.

Platforms affected

• Azure DevOps
• GitHub Actions - Standard Runners
• GitHub Actions - Larger Runners

Runner images affected

• Ubuntu 22.04
• Ubuntu 24.04
• macOS 13
• macOS 13 Arm64
• macOS 14
• macOS 14 Arm64
• macOS 15
• macOS 15 Arm64
• Windows Server 2019
• Windows Server 2022
• Windows Server 2025

Image version and build link

No public example

Is it regression?

Yes. Works: https://github.com/actions/runner-images/blob/win22/20250609.2/images/windows/Windows2022-Readme.md Broken: https://github.com/actions/runner-images/blob/win22/20250617.1/images/windows/Windows2022-Readme.md

Expected behavior

The build capability shouldn't have regressed & bindgen should still be working.

Actual behavior

Bindgen is failing

Repro steps

windows-latest seems to be inconsistent about the image it's selecting (maybe incremental rollout?) and sometimes it's picking a broken image.

[hemanthmanga]

Hi @vlovich, Thank you for bringing this issue to our attention. We will look into this issue and will update you after investigating.

[Cvolton]

can reproduce outside of the context of Rust development as well - just building C++ binaries with Clang reports the exact same error (which makes sense since the error is the STL expecting a newer compiler version)

[1/11] Building CXX object _deps/fmt-build/CMakeFiles/fmt.dir/src/format.cc.obj
FAILED: [code=1] _deps/fmt-build/CMakeFiles/fmt.dir/src/format.cc.obj 
C:\Users\runneradmin\.cargo\bin\sccache.exe C:\PROGRA~1\LLVM\bin\CLANG_~1.EXE -D_HAS_ITERATOR_DEBUGGING=0 -ID:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/include -O3 -DNDEBUG -std=gnu++20 -D_DLL -D_MT -Xclang --dependent-lib=msvcrt -flto=thin --target=x86_64-pc-windows-msvc -MD -MT _deps/fmt-build/CMakeFiles/fmt.dir/src/format.cc.obj -MF _deps\fmt-build\CMakeFiles\fmt.dir\src\format.cc.obj.d -o _deps/fmt-build/CMakeFiles/fmt.dir/src/format.cc.obj -c D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/src/format.cc
In file included from D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/src/format.cc:8:
In file included from D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/include\fmt/format-inl.h:12:
In file included from C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\algorithm:8:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\yvals_core.h:908:1: error: static assertion failed: error STL1000: Unexpected compiler version, expected Clang 19.0.0 or newer.
  908 | _EMIT_STL_ERROR(STL1000, "Unexpected compiler version, expected Clang 19.0.0 or newer.");
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\yvals_core.h:534:58: note: expanded from macro '_EMIT_STL_ERROR'
  534 | #define _EMIT_STL_ERROR(NUMBER, MESSAGE)   static_assert(false, "error " #NUMBER ": " MESSAGE)
      |                                                          ^~~~~
1 error generated.
[2/11] Building CXX object _deps/fmt-build/CMakeFiles/fmt.dir/src/os.cc.obj
FAILED: [code=1] _deps/fmt-build/CMakeFiles/fmt.dir/src/os.cc.obj 
C:\Users\runneradmin\.cargo\bin\sccache.exe C:\PROGRA~1\LLVM\bin\CLANG_~1.EXE -D_HAS_ITERATOR_DEBUGGING=0 -ID:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/include -O3 -DNDEBUG -std=gnu++20 -D_DLL -D_MT -Xclang --dependent-lib=msvcrt -flto=thin --target=x86_64-pc-windows-msvc -MD -MT _deps/fmt-build/CMakeFiles/fmt.dir/src/os.cc.obj -MF _deps\fmt-build\CMakeFiles\fmt.dir\src\os.cc.obj.d -o _deps/fmt-build/CMakeFiles/fmt.dir/src/os.cc.obj -c D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/src/os.cc
In file included from D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/src/os.cc:13:
In file included from D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/include\fmt/os.h:11:
In file included from D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/include\fmt\format.h:41:
In file included from D:/a/Dash-Orb-Practice-Fix/Dash-Orb-Practice-Fix/cpm-cache/fmt/69912fb6b71fcb1f7e5deca191a2bb4748c4e7b6/include\fmt\base.h:20:
In file included from C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\type_traits:8:
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\yvals_core.h:908:1: error: static assertion failed: error STL1000: Unexpected compiler version, expected Clang 19.0.0 or newer.
  908 | _EMIT_STL_ERROR(STL1000, "Unexpected compiler version, expected Clang 19.0.0 or newer.");
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Tools\MSVC\14.44.35207\include\yvals_core.h:534:58: note: expanded from macro '_EMIT_STL_ERROR'
  534 | #define _EMIT_STL_ERROR(NUMBER, MESSAGE)   static_assert(false, "error " #NUMBER ": " MESSAGE)
      |                                                          ^~~~~
1 error generated.

[vlovich]

@Cvolton right but simultaneously it's weird that I'm observing flapping in our CI. I noted the image it seemed like it was working on vs broken which ostensibly in the release notes says it's Clang 18 yet I seem to observe Clang 19 in one and Clang 18 in the other.

[m6vrm]

-D_ALLOW_COMPILER_AND_STL_VERSION_MISMATCH is helped for me for now, but of course version mismatch should be fixed in the image (update to Clang 19).

[ZeunO8]

Do you need more logs of the same error? able to reproduce on windows-latest

[JoostHouben]

Seeing the same error on my clang-cl builds (pure C++, no Rust). E.g., see: https://github.com/JoostHouben/Euwe-chess-engine/actions/runs/15818282100/job/44581369301?pr=40#step:10:434

So far the error seems quite consistent to me, not random.

Is it possible to select the clang-cl binary that comes with Visual Studio, instead of the one from the LLVM toolchain installed on the runner image?