mbrtoc16
extern size_t mbrtoc16(char16_t *_RESTRICT_KYWD, const char *_RESTRICT_KYWD,
if ((len = mbrtoc16(&out, uchar_hello, 5, mbs)) != 1) {
if ((len = mbrtoc16(&out, uchar_hello + 1, 4, mbs)) != 1) {
len = mbrtoc16(&out, NULL, 1, &mbs);
len = mbrtoc16(&out, "", 1, &mbs);
len = mbrtoc16(&out, uchar_wide, 0, &mbs);
len = mbrtoc16(&out, uchar_wide, strlen(uchar_wide), &mbs);
len = mbrtoc16(&out, uchar_wide + i, 1, &mbs);
len = mbrtoc16(&out, uchar_wide + i, 1, &mbs);
len = mbrtoc16(&out0, surrogate, slen, &mbs);
len = mbrtoc16(&out1, uchar_wide, strlen(uchar_wide), &mbs);