wmemchr
extern const wchar_t *wmemchr(const wchar_t *, wchar_t, size_t);
return (wchar_t *)wmemchr((const wchar_t *)__ws, __wc, __n);
extern wchar_t *wmemchr(const wchar_t *, wchar_t, size_t);
using std::wmemchr;