C++ 对象模型分析

参考：https://www.cnblogs.com/wanmeishenghuo/p/9581270.html

 参考文章：https://coolshell.cn/articles/12176.html

 

测试代码：

#include <iostream>
#include <string>

using namespace std;

class Demo
{
protected:
    int mi;
    int mj;
public:
    virtual void print()
    {
        cout << "mi = " << mi << ", "
             << "mj = " << mj << endl;
    }
};


class Bro
{
public:

    int mb;
    
    void print111()
    {
        cout << "mj = " << mb << endl;
    }
};







class Derived : public Demo
{
    int mk;
    Bro bro;
public:
    Derived(int i,int j,int k, int b)
    {
        mi = i;
        mj = j;
        mk = k;
        bro.mb= b;
    
        
    }
    
    void print()
    {
        cout << "mi = " << mi << ", "
             << "mj = " <<mj<< ", "
             << "mk = " << mk << ", "
             << "bro.mb= " << bro.mb << endl;
    }
};

struct Test
{
    void* p;
    int mi;
    int mj;
    int mk;
    int mb;
 
};

int main()
{
    cout << "sizeof(Demo) = " << sizeof(Demo) << endl;
    cout << "sizeof(Bro) = " << sizeof(Bro) << endl;       
    cout << "sizeof(Derived) = " << sizeof(Derived) << endl;  
    
    Derived d(1, 2, 3,4);
    Test* p = reinterpret_cast<Test*>(&d);
    
    cout << "Before changing ..." << endl;
    
    d.print();
    
    p->mi = 10;
    p->mj = 20;
    p->mk = 30;
    p->mb = 40;
 
    
    cout << "After changing ..." << endl;
    
    d.print();
    
    return 0;
}

运行结果：