C/C++ 判斷兩個整數相乘是否溢出

 判斷兩int相乘是否溢出，目前找到的最正確方式：

int is_mul_overflow(int a, int b) {
if( a >= 0 && b >=0  ) {
return INT_MAX / a < b;
    }
else if( a < 0 && b < 0 ) {
return INT_MAX / a > b;
    }
else if( a * b == INT_MIN ) {
return 0;
    }
else {
return a < 0 ? is_mul_overflow(-a, b) : is_mul_overflow(a, -b);
    }
}

void check(int n1, int n2, int expect_ret, int case_n) {
int ret = is_mul_overflow(n1, n2);
if( expect_ret == is_mul_overflow(n1, n2) )
        printf("test pass case:%d\n",case_n);
else
        printf("test fail case:%d\n",case_n);
}

int main() {
int case_n = 0;
    check(1, 0x80000000, 0, ++case_n);
    check(-1, 0x80000000, 1, ++case_n);
    check(0x80000000, -1, 1, ++case_n);
    check(-1, 0x80000001, 0, ++case_n);
    check(0x80000001, -1, 0, ++case_n);
    check(1, 0x7fffffff, 0, ++case_n);
    check(0x7fffffff, 1, 0, ++case_n);
    check(2, 0x7fffffff, 1, ++case_n);
    check(0x7fffffff, 2, 1, ++case_n);
    check(0x7fffffff, -1, 0, ++case_n);
    check(-1, 0x7fffffff, 0, ++case_n);
    check(2, 0xc0000000, 0, ++case_n);
    check(0xc0000000, 2, 0, ++case_n);
    check(0x70000000, 2, 1, ++case_n);
    check(2, 0x70000000, 1, ++case_n);

    printf("%x\n", INT_MIN);
    printf("%x\n", INT_MAX);
return 0;
}

歡迎給出更多測試資料