完全洞悉C++虚函数--1

1.单继承，派生类继承父类的虚表, 更新父类已有的虚函数或者添加新的虚函数

2.多继承，派生类继承所有直接父类的虚表，更新所有父类已有的虚函数（在派生类中重写的），并将派生类新定义的虚函数添加到第一个父类的虚表里。

class Base1

{
public:
virtual void fun1(){cout<<"Bas1:fun1"< virtual void fun2(){cout<<"Bas1:fun2"< //virtual ~Base1(){}
};
class Base2
{
public:
virtual void fun4(){cout<<"Bas2:fun3"< virtual void fun1(){cout<<"Bas2:fun1"< virtual void fun2(){cout<<"Bas2:fun2"< //virtual ~Base2(){}
};


class Derive:public Base1,public Base2
{
public:
//virtual void fun1(){cout<<"derive:fun1"< virtual void fun4(){cout<<"derive:fun3"< };


typedef void(*fun)(void);


void main()
{
Base1 base1;
Base2 base2;
Derive derive;
cout<
fun Fun=(fun)*((int *)*((int *)&derive+0)+0);
Fun();
Fun=(fun)*((int *)*((int *)&derive+0)+1);
Fun();
  cout<<*((int *)*((int *)&derive+0)+2);//为0，虚表结束标志
Fun=(fun)*((int *)*((int *)&derive+1)+0);
Fun();
Fun=(fun)*((int *)*((int *)&derive+1)+1);
Fun();
Fun=(fun)*((int *)*((int *)&derive+1)+2);
Fun();
Base2 * pBase=&derive;
pBase->fun1();

}