https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80265
--- Comment #23 from Pedro Alves <palves at redhat dot com> --- I think support in the compiler directly is likely to have better compile-time performance, and I've stated from the beginning that I'd prefer that, FWIW. OTOH, meanwhile, AFAICT, there's nothing preventing factoring out the trick bits from char_traits into libstdc++-internal __constexpr_strlen/__constexpr_memcmp etc. functions, that fallback into the __builtin_xxx functions when arguments are not constexpr (just like the char_traits versions), and using those throughout instead in constexpr functions.