namespace std { using mbstate_t = see below; using size_t = see [support.types.layout]; size_t mbrtoc16(char16_t* pc16, const char* s, size_t n, mbstate_t* ps); size_t c16rtomb(char* s, char16_t c16, mbstate_t* ps); size_t mbrtoc32(char32_t* pc32, const char* s, size_t n, mbstate_t* ps); size_t c32rtomb(char* s, char32_t c32, mbstate_t* ps); }