c++ - 为什么在sizeof()中添加两个变量类型会返回最大的变量大小值而不是它们的总和？

Question

#include <iostream>

using namespace std;

int main()
{
    int a;
    long b;

    cout<<sizeof(a+b);

    return 0;
}

输出为8(长变量的大小)。为什么不返回它们的总和？

Answer 1

the output is 8(size of a long variable)

由于整型促销。

根据cppreference.com:

the ranks of all signed integer types are different and increase with their precision: rank of signed char < rank of short < rank of int < rank of long int < rank of long long int

因此，a + b会生成long，因为a是int，而b是long(long的秩大于int)。

因此，您具有sizeof(long)，即 8 。

why it doesn't return their addition

您可能正在寻找sizeof(a) + sizeof(b);