c++ 继承类强制转换时的虚函数表工作原理

#include<iostream>
using namespace std;

class Base
{
public:
    virtual void f()
    {
        cout<<"Base::f()"<<endl;
    }
};

class child1:public Base
{
public:
    virtual void f()
    {
        cout<<"child1::f()"<<endl;
    }

    virtual void a()
    {
        cout<<"child1::a()"<<endl;
    }
};

class child2:public Base
{
public:
    virtual void f()
    {
        cout<<"child2::f()"<<endl;
    }

    virtual void b()
    {
        cout<<"child2::b()"<<endl;
    }

    virtual void a()
    {
        cout<<"child2::a()"<<endl;
    }
};

int main()
{


    child1 c1;
    child2* pc21=(child2*)&c1;
    pc21->b();//输出 child1::a()
//  pc21->a();//访问越界，程序运行时崩溃

    child2 c2;
    child1* pc12=(child1*)&c2;
    pc12->a();//输出 child2::b()
    return 0;
}