stdc_bit_width_ull
return (1ULL << (stdc_bit_width_ull(ull) - 1));
return (2ULL << (stdc_bit_width_ull(ull - 1) - 1));
.so_ull = stdc_bit_width_ull,
extern unsigned int stdc_bit_width_ull(unsigned long long) _C23_UNSEQ_ATTR;
char(*)[8]: stdc_bit_width_ull(val))