C++虚析构与纯虚析构

#include<iostream>
#include<string>
using namespace std;
class Animal {
public:
    Animal() {
        cout << "Animal 构造" << endl;
    }
    /*virtual ~Animal() {
        cout << "Animal 虚析构" << endl;
    }*/
    virtual ~Animal() = 0;//纯虚析构也需要代码实现
    virtual void speak() = 0;
};
Animal::~Animal() {
    cout << "Animal 纯虚析构" << endl;
}
class Cat :public Animal {
public:
    Cat(string name) {
        cout << "Cat 构造" << endl;
        m_Name = new string(name);
    }
    virtual void speak() {
        cout << *m_Name <<"小猫在说话" << endl;
    }
    ~Cat() {
        if (m_Name != NULL) {
            cout << "Cat 析构" << endl;
            delete m_Name;
            m_Name = NULL;
        }
    }
    string* m_Name;
};
void test01() {
    Animal* animal = new Cat("Tom");
    animal->speak();
    delete animal;
}
int main() {
    test01();
    //解决 父类指针在释放时无法调用子类的析构函数 的问题 
    system("pause");
    return 0;
}

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

class Circle:public Point
{public:
  Circle(){}
  ~Circle(){cout<<"executing Circle destructor"<<endl;}
};

int main()
{Point *p=new Circle;
 delete p;
 return 0;
}