https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78204
--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Fangrui Song from comment #8) > Note: Clang supports > __attribute__((no_sanitize("address","undefined"))) > but not > __attribute__((no_sanitize("address,undefined"))) > > Possibly reject `__attribute__((no_sanitize("address,undefined")))` as well > to prevent users from writing non-portable code. We document both ways already. https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Common-Function-Attributes.html#index-no_005fsanitize-function-attribute I would have said if we don't document both ways we should reject it but since it is documented already, maybe add to the documentation that clang does not accept the combined string way.