类的sizeof

#include<iostream>

using namespace std;

class A{};

class B : public A{public:      void fun(){}};

class C : public B{public:       virtual void func(){}             };

int main(){    cout << sizeof(A) << endl;    cout << sizeof(B) << endl;    cout << sizeof(C) << endl;    system("pause");    return 0;}

dev-c++4.9.9.2输出结果为

1

1

4