[clang-tools-extra] [clang-tidy] warn when `true` is used as a preprocessor keyword in C (PR #128265)

[via cfe-commits]

isuckatcs wrote:

> Clang-tidy uses clang to process the source file, so any warning implemented in clang is available to all clang-tidy users regardless of whether they compile with clang or GCC or something else.

A fair point indeed. I'll proceed with option 3 then.

https://github.com/llvm/llvm-project/pull/128265