clang-tidy not respecting -Wno-builtin-macro-redefined with gnu++20

[barci2]

If clang-tidy is set to use the gnu++20 language standard (does not work with regular c++ or lower versions of gnu++) then the -Wno-builtin-macro-redefined CDB flag is not respected, even if the macro is redefined as a compilation flag itself. Note that this is not an issue with the regular compiler as it does not throw that error. Minimal reproducer:
touch test.cc && llvm-project/build/bin/clang-tidy test.cc -- -std=gnu++20 -D__TIME__ -Wno-builtin-macro-redefined

[llvmbot]

@llvm/issue-subscribers-clang-tidy

[HappyCerberus]

Is there any workaround?

This just cropped up for me when using the Bazel module for clang-tidy integration: https://github.com/erenon/bazel_clang_tidy

[igormcoelho]

Just got into this error, with the same problem using https://github.com/erenon/bazel_clang_tidy.
The clang-tidy fix proposed there (erenon/bazel_clang_tidy#29) resolved this for me, putting this flag into .clang-tidy file: -clang-diagnostic-builtin-macro-redefined
So, maybe it's an issue of clang-tidy itself, not clang? Anyway, disabling this clang-tidy check resolved the issue for me.

[HappyCerberus]

So, maybe it's an issue of clang-tidy itself, not clang?

This is a clang-tidy bug report (nothing to do with clang).

[AaronBallman]

Can confirm this issue: https://godbolt.org/z/ohq19e8Wq Clang silences the diagnostic and clang-tidy continues to issue it.

[PiotrZSL]

Related to #61969