通过指向 Base 的指针删除 Derived 对象时，一定会先调用 Derived 的析构函数，再调用 Base 的析构函数

#include<iostream>
using namespace std;
class Base{
public:
    ~Base(){
        cout<<"Base destructor"<< endl;
    }
};

class Derived: public Base{
public:
    ~Derived(){
        cout<<"Derived destructor"<< endl;
    }
};

int main(){
    Base* p= new Derived();
    delete p;
    return 0;
}