[clang] [C++20] [Modules] Write comments in C++20 modules' module file (PR #192398)

Thu Apr 16 02:23:00 PDT 2026

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-x86_64-windows` running on `minipc-ryzen-win` while building `clang` at step 7 "test-build-unified-tree-check-flang".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/166/builds/8377

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 7 (test-build-unified-tree-check-flang) failure: test (failure)
...
42.619 [28/6/939] Building CXX object tools\flang\unittests\Optimizer\CMakeFiles\FlangOptimizerTests.dir\InternalNamesTest.cpp.obj
42.655 [27/6/940] Building CXX object tools\flang\unittests\Optimizer\CMakeFiles\FlangOptimizerTests.dir\FIRTypesTest.cpp.obj
42.672 [26/6/941] Building CXX object tools\flang\unittests\Optimizer\CMakeFiles\FlangOptimizerTests.dir\FortranVariableTest.cpp.obj
42.751 [25/6/942] Building CXX object tools\flang\unittests\Optimizer\CMakeFiles\FlangOptimizerTests.dir\KindMappingTest.cpp.obj
42.756 [24/6/943] Building RC object tools\flang\unittests\Optimizer\CMakeFiles\FlangOptimizerTests.dir\C_\buildbot\flang-x86_64-windows\llvm-project\llvm\resources\windows_version_resource.rc.res
42.843 [23/6/944] Building RC object tools\flang\unittests\Frontend\CMakeFiles\FlangFrontendTests.dir\C_\buildbot\flang-x86_64-windows\llvm-project\llvm\resources\windows_version_resource.rc.res
42.871 [22/6/945] Building CXX object tools\flang\unittests\Optimizer\CMakeFiles\FlangOptimizerTests.dir\RTBuilder.cpp.obj
42.907 [21/6/946] Building CXX object tools\flang\unittests\Semantics\CMakeFiles\OpenMPUtilsTests.dir\OpenMPUtils.cpp.obj
42.916 [20/6/947] Building RC object tools\flang\unittests\Semantics\CMakeFiles\OpenMPUtilsTests.dir\C_\buildbot\flang-x86_64-windows\llvm-project\llvm\resources\windows_version_resource.rc.res
44.089 [19/6/948] Linking CXX executable bin\flang.exe
FAILED: [code=4294967295] bin/flang.exe 
C:\Windows\system32\cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --msvc-ver=1944 --intdir=tools\flang\tools\flang-driver\CMakeFiles\flang.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\mt.exe --manifests  -- C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\flang.rsp  /out:bin\flang.exe /implib:lib\flang.lib /pdb:bin\flang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console && C:\Windows\system32\cmd.exe /C "cd /D C:\buildbot\flang-x86_64-windows\build\tools\flang\tools\flang-driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/flang.exe C:/buildbot/flang-x86_64-windows/build/./bin/flang-new.exe""
LINK: command "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\flang.rsp /out:bin\flang.exe /implib:lib\flang.lib /pdb:bin\flang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console /MANIFEST:EMBED,ID=1" failed (exit code 1235) with the following output:
clangSerialization.lib(ASTReader.cpp.obj) : fatal error LNK1235: corrupt or invalid COFF symbol table

46.380 [19/5/949] Linking CXX executable tools\flang\unittests\Optimizer\FlangOptimizerTests.exe
46.558 [19/4/950] Linking CXX executable bin\tco.exe
48.252 [19/3/951] Linking CXX executable bin\fir-opt.exe
51.851 [19/2/952] Linking CXX executable bin\bbc.exe
54.783 [19/1/953] Linking CXX executable tools\flang\unittests\Frontend\FlangFrontendTests.exe
ninja: build stopped: subcommand failed.
Cache directory:       C:\Users\buildbot-worker\AppData\Local\ccache
Config file:           C:\Users\buildbot-worker\AppData\Local\ccache\ccache.conf
Directory config file:
System config file:    C:\ProgramData\ccache\ccache.conf
Stats updated:         04/16/26 02:22:10
Cacheable calls:          31 /  31 (100.0%)
  Hits:                   31 /  31 (100.0%)
    Direct:               31 /  31 (100.0%)
    Preprocessed:          0 /  31 ( 0.00%)
  Misses:                  0 /  31 ( 0.00%)
Successful lookups:
  Direct:                 31 /  31 (100.0%)
  Preprocessed:            0
Local storage:
  Cache size (GB):       5.0 / 5.0 (99.94%)
  Files:               21418
  Hits:                   31 /  31 (100.0%)
  Misses:                  0 /  31 ( 0.00%)
  Reads:                  62
  Writes:                  0
Step 8 (test-build-unified-tree-check-flang-rt) failure: test (failure)
...
2.169 [41/4/7] Building Opts.inc...
2.170 [40/3/8] Building WindresOpts.inc...
2.174 [39/2/9] Building Opts.inc...
2.302 [38/1/10] Generating VCSRevision.h, __FakeVCSRevision.h
3.108 [13/6/11] Linking CXX executable bin\llvm-ar.exe
3.188 [12/6/12] Generating ../../bin/llvm-ranlib.exe
3.257 [11/6/13] Linking CXX executable bin\llvm-nm.exe
3.264 [10/6/14] Generating ../../bin/llvm-lib.exe
3.332 [9/6/15] Linking CXX executable bin\llvm-objdump.exe
3.771 [8/6/16] Linking CXX executable bin\clang.exe
FAILED: [code=4294967295] bin/clang.exe 
C:\Windows\system32\cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --msvc-ver=1944 --intdir=tools\clang\tools\driver\CMakeFiles\clang.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\mt.exe --manifests  -- C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\clang.rsp  /out:bin\clang.exe /implib:lib\clang.lib /pdb:bin\clang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console && C:\Windows\system32\cmd.exe /C "cd /D C:\buildbot\flang-x86_64-windows\build\tools\clang\tools\driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/clang.exe C:/buildbot/flang-x86_64-windows/build/./bin/clang++.exe && cd /D C:\buildbot\flang-x86_64-windows\build\tools\clang\tools\driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/clang.exe C:/buildbot/flang-x86_64-windows/build/./bin/clang-cl.exe && cd /D C:\buildbot\flang-x86_64-windows\build\tools\clang\tools\driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/clang.exe C:/buildbot/flang-x86_64-windows/build/./bin/clang-cpp.exe""
LINK: command "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\clang.rsp /out:bin\clang.exe /implib:lib\clang.lib /pdb:bin\clang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console /MANIFEST:EMBED,ID=1" failed (exit code 1235) with the following output:
clangSerialization.lib(ASTReader.cpp.obj) : fatal error LNK1235: corrupt or invalid COFF symbol table

4.610 [8/5/17] Linking CXX executable bin\llvm-jitlink.exe
5.375 [8/4/18] Linking CXX executable bin\flang.exe
FAILED: [code=4294967295] bin/flang.exe 
C:\Windows\system32\cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --msvc-ver=1944 --intdir=tools\flang\tools\flang-driver\CMakeFiles\flang.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\mt.exe --manifests  -- C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\flang.rsp  /out:bin\flang.exe /implib:lib\flang.lib /pdb:bin\flang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console && C:\Windows\system32\cmd.exe /C "cd /D C:\buildbot\flang-x86_64-windows\build\tools\flang\tools\flang-driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/flang.exe C:/buildbot/flang-x86_64-windows/build/./bin/flang-new.exe""
LINK: command "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\flang.rsp /out:bin\flang.exe /implib:lib\flang.lib /pdb:bin\flang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console /MANIFEST:EMBED,ID=1" failed (exit code 1235) with the following output:
clangSerialization.lib(ASTReader.cpp.obj) : fatal error LNK1235: corrupt or invalid COFF symbol table

6.034 [8/3/19] Linking CXX executable bin\lli.exe
6.200 [8/2/20] Linking CXX executable bin\llvm-lto.exe
7.088 [8/1/21] Linking CXX executable bin\opt.exe
ninja: build stopped: subcommand failed.
Cache directory:       C:\Users\buildbot-worker\AppData\Local\ccache
Config file:           C:\Users\buildbot-worker\AppData\Local\ccache\ccache.conf
Directory config file:
System config file:    C:\ProgramData\ccache\ccache.conf
Stats updated:         04/16/26 02:22:23
Local storage:
  Cache size (GB):       5.0 / 5.0 (99.94%)
  Files:               21418
  Hits:                    0
  Misses:                  0
  Reads:                   0
  Writes:                  0
Step 9 (install-build-unified-treeall) failure: build (failure)
...
2.698 [91/6/26] Building Opts.inc...
2.700 [88/6/27] Building Opts.inc...
2.760 [86/6/28] Building LipoOpts.inc...
2.762 [84/6/29] Building TapiOpts.inc...
2.817 [81/6/30] Building Opts.inc...
2.820 [78/6/31] Building Opts.inc...
3.516 [75/6/32] Linking CXX executable bin\sancov.exe
3.641 [74/6/33] Linking CXX executable bin\llvm-dwarfdump.exe
3.865 [73/6/34] Linking CXX executable bin\llvm-ml.exe
3.903 [72/6/35] Linking CXX shared library bin\libclang.dll
FAILED: [code=4294967295] bin/libclang.dll lib/libclang.lib 
C:\Windows\system32\cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_dll --msvc-ver=1944 --intdir=tools\clang\tools\libclang\CMakeFiles\libclang.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\mt.exe --manifests  -- C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\libclang.rsp  /out:bin\libclang.dll /implib:lib\libclang.lib /pdb:bin\libclang.pdb /dll /version:23.0 /machine:x64 /INCREMENTAL:NO && cd ."
LINK: command "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\libclang.rsp /out:bin\libclang.dll /implib:lib\libclang.lib /pdb:bin\libclang.pdb /dll /version:23.0 /machine:x64 /INCREMENTAL:NO /MANIFEST:EMBED,ID=2" failed (exit code 1235) with the following output:
clangSerialization.lib(ASTReader.cpp.obj) : fatal error LNK1235: corrupt or invalid COFF symbol table

3.947 [72/5/36] Generating ../../bin/llvm-dlltool.exe
3.987 [72/4/37] Linking CXX executable bin\clang.exe
FAILED: [code=4294967295] bin/clang.exe 
C:\Windows\system32\cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --msvc-ver=1944 --intdir=tools\clang\tools\driver\CMakeFiles\clang.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\mt.exe --manifests  -- C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\clang.rsp  /out:bin\clang.exe /implib:lib\clang.lib /pdb:bin\clang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console && C:\Windows\system32\cmd.exe /C "cd /D C:\buildbot\flang-x86_64-windows\build\tools\clang\tools\driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/clang.exe C:/buildbot/flang-x86_64-windows/build/./bin/clang++.exe && cd /D C:\buildbot\flang-x86_64-windows\build\tools\clang\tools\driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/clang.exe C:/buildbot/flang-x86_64-windows/build/./bin/clang-cl.exe && cd /D C:\buildbot\flang-x86_64-windows\build\tools\clang\tools\driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/clang.exe C:/buildbot/flang-x86_64-windows/build/./bin/clang-cpp.exe""
LINK: command "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\clang.rsp /out:bin\clang.exe /implib:lib\clang.lib /pdb:bin\clang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console /MANIFEST:EMBED,ID=1" failed (exit code 1235) with the following output:
clangSerialization.lib(ASTReader.cpp.obj) : fatal error LNK1235: corrupt or invalid COFF symbol table

5.608 [72/3/38] Linking CXX executable bin\flang.exe
FAILED: [code=4294967295] bin/flang.exe 
C:\Windows\system32\cmd.exe /C "cd . && "C:\Program Files\CMake\bin\cmake.exe" -E vs_link_exe --msvc-ver=1944 --intdir=tools\flang\tools\flang-driver\CMakeFiles\flang.dir --rc=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\rc.exe --mt=C:\PROGRA~2\WI3CF2~1\10\bin\100261~1.0\x64\mt.exe --manifests  -- C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\flang.rsp  /out:bin\flang.exe /implib:lib\flang.lib /pdb:bin\flang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console && C:\Windows\system32\cmd.exe /C "cd /D C:\buildbot\flang-x86_64-windows\build\tools\flang\tools\flang-driver && "C:\Program Files\CMake\bin\cmake.exe" -E copy C:/buildbot/flang-x86_64-windows/build/bin/flang.exe C:/buildbot/flang-x86_64-windows/build/./bin/flang-new.exe""
LINK: command "C:\PROGRA~1\MICROS~2\2022\COMMUN~1\VC\Tools\MSVC\1444~1.352\bin\Hostx64\x64\link.exe /nologo @CMakeFiles\flang.rsp /out:bin\flang.exe /implib:lib\flang.lib /pdb:bin\flang.pdb /version:0.0 /machine:x64 /STACK:10000000 /INCREMENTAL:NO /subsystem:console /MANIFEST:EMBED,ID=1" failed (exit code 1235) with the following output:
clangSerialization.lib(ASTReader.cpp.obj) : fatal error LNK1235: corrupt or invalid COFF symbol table

7.675 [72/2/39] Linking CXX shared library bin\LTO.dll
14.928 [72/1/40] Generating export list for LLVM-C
ninja: build stopped: subcommand failed.
Cache directory:       C:\Users\buildbot-worker\AppData\Local\ccache
Config file:           C:\Users\buildbot-worker\AppData\Local\ccache\ccache.conf
Directory config file:
System config file:    C:\ProgramData\ccache\ccache.conf
Stats updated:         04/16/26 02:22:32
Local storage:
  Cache size (GB):       5.0 / 5.0 (99.94%)
  Files:               21418
  Hits:                    0
  Misses:                  0
  Reads:                   0
  Writes:                  0

```

</details>

https://github.com/llvm/llvm-project/pull/192398