"if" c++ 中的语句不会从左到右评估条件

Question

我指的是问题“"IF" argument evaluation order?”，以了解 c++ 中 "if" 语句的求值顺序。

以下代码中 if 语句中条件的计算顺序错误。

#include <iostream>

using namespace std;

int main()
{
    int t = 0;
    if((1 / t) == 1 && t != 0)
    {
        cout << "0" << endl;
    }

    cout << "1" << endl;

    return 0;
}

结果是1而不是浮点数异常

Answer 1

被零除是未定义的行为。什么事都有可能发生。

[expr.mul]/4

If the second operand of / or % is zero the behavior is undefined.

Answer 2

除以零并不能保证每次程序都会抛出运行时错误。这就是为什么除以零是未定义的行为。

如 C 标准所述；

The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behaviour is undefined.

对于 C++ (03-5.6.4);

The binary / operator yields the quotient, and the binary % operator yields the remainder from the division of the first expression by the second. If the second operand of / or % is zero the behavior is undefined; otherwise (a/b)*b + a%b is equal to a. If both operands are nonnegative then the remainder is nonnegative; if not, the sign of the remainder is implementation-defined

"if" c++ 中的语句不会从左到右评估条件

"if" statement in c++ doesn't evaluate conditions from left to right

c++

integer-division

divide-by-zero

c++11

c++14