[Bug preprocessor/103026] Implement warning for Unicode bidi override characters [CVE-2021-42574]

[mpolacek at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103026

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Patch posted:
https://gcc.gnu.org/pipermail/gcc-patches/2021-November/583031.html