https://gcc.gnu.org/bugzilla/show_bug.cgi?id=33979
--- Comment #20 from Jonathan Wakely <redi at gcc dot gnu.org> --- Compiler support for char16_t and char32_t has been complete for many years. The libstdc++ support required by the standard has been complete since GCC 5.1, but I don't know if Paolo had more in mind (we don't implement all locale facets for char16_t and char32_t, which means e.g. std::basic_stringstream<char16_t> doesn't work, but the standard doesn't require it to work).
