char32_t
size_t mbrtoc32(char32_t * __restrict, const char * __restrict, size_t,
size_t c32rtomb(char * __restrict, char32_t, mbstate_t * __restrict);
c32rtomb(char *s, char32_t c32, mbstate_t *ps)
mbrtoc32(char32_t *pc32, const char *s, size_t n, mbstate_t *ps)