虚表与类对象内存结构

https://www.cnblogs.com/hushpa/p/5707475.html

#include
using namespace std;

class Base {
public:
	virtual void f() { cout << "Base::f" << endl; }
	virtual void g() { cout << "Base::g" << endl; }
	virtual void h() { cout << "Base::h" << endl; }
};
class Drived : public Base
{
	virtual void f() { cout << "Drived::f" << endl; }
	//virtual void g() { cout << "Drived::g" << endl; }//这个函数使用基类的
	virtual void h() { cout << "Drived::h" << endl; }
	virtual void i() { cout << "Drived::i" << endl; }
};

int main()
{
	typedef void(*Fun)(void);
	Fun pFun = NULL;

	Base b;

	cout << "变量地址：" << (int*)(&b) << endl;
	auto pobj = (int*)(&b);
	cout << "虚表在其他地方，变量地址指向的内存里存着虚表的地址：" << endl;
	auto vtb = (int*)*pobj;//通过虚表地址，得到虚表变量
	
	pFun = (Fun)(vtb[0]);//第一个函数地址Base::f
	pFun();
	pFun = (Fun)vtb[1];//第二个函数地址Base::g
	pFun();
	pFun = (Fun)vtb[2];//第三个函数地址Base::h
	pFun();

	Drived d;
	cout << "变量地址：" << (int*)(&d) << endl;
	pobj = (int*)(&d);
	cout << "虚表在其他地方，变量地址指向的内存里存着虚表的地址：" << endl;
	vtb = (int*)*pobj;//通过虚表地址，得到虚表变量

	pFun = (Fun)vtb[0];//第一个函数地址Drived::f
	pFun();
	pFun = (Fun)vtb[1];//第二个函数地址Drived::g
	pFun();
	pFun = (Fun)vtb[2];//第三个函数地址Drived::h
	pFun();
	pFun = (Fun)vtb[3];//第四个函数地址Drived::i
	pFun();

	return 1;
}