c++中一个多态的实例

#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;

class A{
public:
    A(){
        a = ;
    }
    int a;
};

class B :public A{
public:
    B(){
        a = ;
    }
    int a;
};

int main(){
    B b ;
    B *pb = &b;
    A* pa = &b;

    printf("a in B is: %d\n", pb->a);
    printf("a in A is: %d\n", pa->a);

    printf("value of pb is: %p\n", pb);
    printf("value of pa is: %p\n", pa);

    printf("address of pb->a is: %p\n", &(pb->a));
    printf("address of pa->a is: %p\n", &(pa->a));

    return ;
}

结果如下：