https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113658
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> --- It doesn't help that __has_feature/__has_extension is very badly documented, obviously the best meaning for a feature check would be that the selected builtins are usable in constexpr expressions if they are implemented, but it has been added before __has_builtin has been introduced/standardized. And for __builtin_wcs* etc. implementation we have the long standing problem what APIs to use to access the wchar_ts, I think that is the reason why we don't implement format attribute for *wprintf etc.
