GCC-2——杂项汇总

1. __builtin_constant_p

它是GCC的内建函数，用于判断一个值是否为编译时常数，如果参数是常数，函数返回 1，否则返回 0。

#include <stdio.h>

#define MAX 10 //built in constant

int global = 10; //non built in constant

int * const p = NULL; //non built in constant

int test_func() //non built in constant
{
    return 0;
}

void main()
{
    if (__builtin_constant_p(p)) {
        printf("built in constant\n");
    } else {
        printf("non built in constant\n");
    }
}