https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118105
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to GCC Commits from comment #4) > I'm unsure if std::regex_traits<C>::transform_primary is supposed to > convert the string to lower case or not. The general regex traits > requirements ([re.req] p20) do say "when character case is not > considered" but the specification for the std::regex_traits<char> and > std::regex_traits<wchar_t> specializations ([re.traits] p7) don't say > anything about that. Libc++ apparently does not convert to lowercase, because it has tests to verify that the equivalence class [=M=] does not match "m".
