同一内存地址的两个不同值

问题描述

代码

#include 使用命名空间标准；int main() {const int N = 22;int * pN = const_cast(&N);*pN = 33；cout<<N＜＜'	' <<&N <<结束;cout<<*pN＜＜'	' <<pN＜＜结束;}

输出

22 0x22ff74

33 0x22ff74

为什么同一个地址有两个不同的值?

为什么同一个地址有两个不同的数据?

没有.编译器可以优化任何对 const 的提及，就好像您在其中写入了它的编译时值一样.

请注意，如果您做了一些讨厌的技巧，例如写入为常量保留的内存，编译器也可以生成在您运行时擦除硬盘的代码.

Code

#include <iostream>
using namespace std;

int main() {
    const int N = 22;
    int * pN = const_cast<int*>(&N);
    *pN = 33;
    cout << N << '	' << &N << endl;
    cout << *pN << '	' << pN << endl;
}

Output

22 0x22ff74

33 0x22ff74

Why are there two different values at the same address?

Why are there two different datas at the same address?

There aren't. The compiler is allowed to optimize any mention of a const to be as though you had written its compile-time value in there.

Note that the compiler is also allowed to generate code that erases your hard disk when you run it if you do nasty tricks like writing to memory reserved for consts.

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