虚函数表是个什么鬼详解编程语言

// pvtable1.cpp : 定义控制台应用程序的入口点。 
// 
 
#include "stdafx.h" 
#include <iostream> 
using namespace std; 
class Base1 { 
public: 
Base1(){ cout << "Base1::Base1()" << endl; } 
~Base1(){ cout << "Base1::~Base1()" << endl; } 
virtual void f() { cout << "Base1::f" << endl; } 
virtual void g() { cout << "Base1::g" << endl; } 
virtual void h() { cout << "Base1::h" << endl; } 
}; 
class Base2 { 
public: 
Base2(){ cout << "Base2::Base2()" << endl; } 
~Base2(){ cout << "Base2::~Base2()" << endl; } 
virtual void f() { cout << "Base2::f" << endl; } 
virtual void g() { cout << "Base2::g" << endl; } 
virtual void h() { cout << "Base2::h" << endl; } 
}; 
class Base3 { 
public: 
Base3(){ cout << "Base3::Base3()" << endl; } 
~Base3(){ cout << "Base3::~Base3()" << endl; } 
virtual void f() { cout << "Base3::f" << endl; } 
virtual void g() { cout << "Base3::g" << endl; } 
virtual void h() { cout << "Base3::h" << endl; } 
}; 
class Derive : public Base1, public Base2, public Base3 { 
public: 
Derive(){ cout << "Derive::Derive()" << endl; } 
~Derive(){ cout << "Derive::~Derive()" << endl; } 
virtual void f() { cout << "Derive::f" << endl; } 
virtual void g1() { cout << "Derive::g1" << endl; } 
}; 
typedef void(*Fun)(void); 
int doIt()  
{ 
Fun pFun = NULL; 
Derive d; 
int** pVtab = (int**)&d; 
//Base1's vtable 
//pFun = (Fun)*((int*)*(int*)((int*)&d+0)+0); 
 
pFun = (Fun)pVtab[0][0]; 
pFun(); 
//pFun = (Fun)*((int*)*(int*)((int*)&d+0)+1); 
 
pFun = (Fun)pVtab[0][1]; 
pFun(); 
//pFun = (Fun)*((int*)*(int*)((int*)&d+0)+2); 
 
pFun = (Fun)pVtab[0][2]; 
pFun(); 
//Derive's vtable 
//pFun = (Fun)*((int*)*(int*)((int*)&d+0)+3); 
 
pFun = (Fun)pVtab[0][3]; 
pFun(); 
//The tail of the vtable 
 
pFun = (Fun)pVtab[0][4]; 
cout<<pFun<<endl; 
//Base2's vtable 
//pFun = (Fun)*((int*)*(int*)((int*)&d+1)+0); 
 
pFun = (Fun)pVtab[1][0]; 
pFun(); 
//pFun = (Fun)*((int*)*(int*)((int*)&d+1)+1); 
 
pFun = (Fun)pVtab[1][1]; 
pFun(); 
pFun = (Fun)pVtab[1][2]; 
pFun();  
//The tail of the vtable 
 
pFun = (Fun)pVtab[1][3]; 
cout<<pFun<<endl; 
//Base3's vtable 
//pFun = (Fun)*((int*)*(int*)((int*)&d+1)+0); 
 
pFun = (Fun)pVtab[2][0]; 
pFun(); 
//pFun = (Fun)*((int*)*(int*)((int*)&d+1)+1); 
 
pFun = (Fun)pVtab[2][1]; 
pFun(); 
pFun = (Fun)pVtab[2][2]; 
pFun();  
//The tail of the vtable 
 
pFun = (Fun)pVtab[2][3]; 
cout<<pFun<<endl; 
cout<<sizeof(d)<<endl; 
return 0; 
} 
int _tmain(int argc, _TCHAR* argv[]) 
{ 
doIt(); 
return 0; 
}