C++虚函数表理解

#include "iostream"using namespace std;class Base1{public:virtual void f(){cout <<"Base1::f" <<endl;}virtual void g(){cout <<"Base1::g" <<endl;}virtual void h(){cout <<"Base1::h" <<endl;}};class Base2{public:virtual void f(){cout <<"Base2::f" <<endl;}virtual void g(){cout <<"Base2::g" <<endl;}virtual void h(){cout <<"Base2::h" <<endl;}};class Base3{public: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:virtual void f(){cout <<"Derive::f" <<endl;}virtual void g1(){cout <<"Derive::g1" <<endl;}virtual void h1(){cout <<"Derive::h1" <<endl;}};typedef void(*Fun)(void);int main(){Fun pFun = NULL;Derive d;int** pVtab = (int**)&d;cout <<"虚函数表地址：" <<(int*)&d <<endl;/* Base1's vtable *///pFun = (Fun)*((int*)*((int*)&d + 0) + 0);pFun = (Fun)pVtab[0][0];pFun();//pFun = (Fun)*((int*)*((int*)&d + 0) + 1);pFun = (Fun)pVtab[0][1];pFun();//pFun = (Fun)*((int*)*((int*)&d + 0) + 2);pFun = (Fun)pVtab[0][2];pFun();//pFun = (Fun)*((int*)*((int*)&d + 0) + 3);pFun = (Fun)pVtab[0][3];pFun();//pFun = (Fun)*((int*)*((int*)&d + 0) + 4);pFun = (Fun)pVtab[0][4];pFun();/* Base2's vtable *///pFun = (Fun)*((int*)*((int*)&d + 1) + 0);pFun = (Fun)pVtab[1][0];pFun();//pFun = (Fun)*((int*)*((int*)&d + 1) + 1);pFun = (Fun)pVtab[1][1];pFun();//pFun = (Fun)*((int*)*((int*)&d + 1) + 2);pFun = (Fun)pVtab[1][2];pFun();/* Base3's vtable *///pFun = (Fun)*((int*)*((int*)&d + 2) + 0);pFun = (Fun)pVtab[2][0];pFun();//pFun = (Fun)*((int*)*((int*)&d + 2) + 1);pFun = (Fun)pVtab[2][1];pFun();//pFun = (Fun)*((int*)*((int*)&d + 2) + 2);pFun = (Fun)pVtab[2][2];pFun();return 0;}