See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103026 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103027 ... for adding warnings to GCC.
... and https://gcc.gnu.org/pipermail/gcc-patches/2021-November/583031.html.
https://gcc.gnu.org/pipermail/gcc-patches/2021-November/583039.html for homoglyph patch to preprocessor
Seems to be only in 12.1.0?