bool size_t_mul_overflow(size_t a, size_t b, size_t *res)
{
#if __SIZEOF_SIZE_T__ == 4
    return __builtin_smul_overflow((int)a, (int)b, (int *)res);
#elif __SIZEOF_SIZE_T__ == 8
    return __builtin_smull_overflow((long)a, (long)b, (long *)res);
#endif
}