C++ 虚函数

using namespace std;
#include <iostream>

using namespace std;

class A{                                                                                                                                                                                        
public:
    virtual void Fun1(){
        cout << "A::Func1" << endl;
    }   

    virtual void Fun2(){
        cout << "A::Func2" << endl;
    }   
};

class B : public A{
public:
    virtual void Fun1(){
        cout << "B::Func1" << endl;
    }   

    virtual void Fun3(){
        cout << "B::Func3" << endl;
    }   
};

class C : public B{
public:
    virtual void Fun1(){
        cout << "C::Func1" << endl;
    }   

    virtual void Fun4(){
        cout << "C::Func4" << endl;
    }   
};

typedef void(*FUNC)();
int main()
{
    A a;
    cout << "A::虚表" << endl << endl;
    ((FUNC)(*(long*)(*(long*)(&a))))();
    ((FUNC)(*((long*)(*(long*)(&a)) + 1)))();
    cout << "------------------------" << endl;

    B b;
    cout << "B::虚表" << endl << endl;
    ((FUNC)(*(long*)(*(long*)(&b))))();
    ((FUNC)(*((long*)(*(long*)(&b)) + 1)))();
    ((FUNC)(*((long*)(*(long*)(&b)) + 2)))();
    cout << "------------------------" << endl;

    C c;
    cout << "C::虚表" << endl << endl;
    ((FUNC)(*(long*)(*(long*)(&c))))();
    ((FUNC)(*((long*)(*(long*)(&c)) + 1)))();
    ((FUNC)(*((long*)(*(long*)(&c)) + 2)))();
    ((FUNC)(*((long*)(*(long*)(&c)) + 3)))();
    cout << "------------------------" << endl;
    return 0;
}  

  虚函数表继承替换原则：

有则替换， 无则末尾追加。