使用成员变量的偏移量访问结构的私有成员 [英] Accessing private members of a struct using offset of member variables

问题描述

我正在阅读有关结构和结构填充的内容，并编写了此代码.它使用从 a 的地址偏移量来编辑结构的私有成员.这是否意味着您可以参加某人制作的课程并提取/更改私有变量和函数?

I was reading about structs and struct padding and I wrote this code. It edits a private member of a struct using its address offset from a. Does this mean you can take a class someone made and extract/change private varriables and functions?

#include <iostream>
typedef struct x {
    int a; 
private:
    int b;
public:
//Init
    x(int a, int b) : a(a) , b(b){}

    void print(){
        //Print values
        std::cout << a << " " << b << std::endl;
    }
} x;

int main()
{
    struct x s(10,20) ;
    int *p = (int *)(((char*)&s)+4); //4 Byte offset from a (a is at base)
    s.print();
    (*p) +=1;
    s.print();

    //Stops terminal closing
    int junk;
    std::cin >> junk;
    return 1;
}

推荐答案

C++ 的 private 用于为抽象数据类型提供封装机制.不是阻止人们编写坏代码，如果他们真的想要.

C++'s private is for giving abstract data types an encapsulation mechanism. It's not for preventing people from writing bad code if they really want to.

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