stdc_trailing_zeros_us
return (stdc_trailing_zeros_us(~us));
return (stdc_trailing_zeros_us(us) + 1);
.so_us = stdc_trailing_zeros_us,
char(*)[2]: stdc_trailing_zeros_us(val), \
extern unsigned int stdc_trailing_zeros_us(unsigned short) _C23_UNSEQ_ATTR;