在多重继承里的虚函数表可以在vs里面看到，如下

 

有一个基类就有一张表，可以通过

int** pVtab = (int**)&d;    pFun = (Fun)pVtab[0][0]; 来访问每一个虚函数，如下代码：

// pvtable1.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include 
     
      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<
      
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运行结果如下：

最后用sizeof获取对象的大小等于成员变量的大小加上虚函数表指针的大小