怎么可能？问题是“预测输出“。 [英] How is it possibble? Question is " predict the output".

问题描述

#include <iostream>
using namespace std;

int main()
{
    if (sizeof(int) > -1)
        cout << "Yes";
    else
        cout << "No";
    return 0;
}

我的尝试：



根据我的回答应该是肯定的。

ut正确的答案是否定的。

怎么可能？

What I have tried:

according to me the answer should be yes.
ut the correct answer is no.
how is it possibble?

推荐答案

因为 sizeof 运算符返回无符号值。因此编译器然后将-1视为无符号值。十六进制值-1是0xFFFFFFFF或无符号十进制4294967295，当然远大于整数的大小（4（不是8））。在软件中混合有符号和无符号值的缺陷之一。

Because the sizeof operator returns an unsigned value. So the compiler then treats -1 also as an unsigned value. The hexadecimal value of -1 is 0xFFFFFFFF or unsigned decimal 4294967295, which of course is much greater than the size of an integer (which is 4 (not 8)). One of the pitfalls of mixing signed and unsigned values in software.

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