基类析构函数加上Virtual

下面的内容要说明两个问题：1. 基类的析构函数为什么要加上Virtual–防止内存泄露

1. 基类虚构函数无virtual，派生类无法析构，会导致内存泄露

#include <stdio.h>

class Base
{
    
    
public:
    int a;
    Base(){
    
    
        a=0;
    }

    ~Base(){
    
    
        printf("base delete");
    }

    virtual void setA()=0;
};

 

class A:public Base
{
    
    
public:
    A(){
    
    
        a = 10;
    }

    ~A(){
    
    
        printf("A class delete\n");
    }

    virtual void setA()
    {
    
    
        a = 2;
    }

};

class B:public Base
{
    
    
public:
    B(){
    
    
        a=20;
    }

    ~B(){
    
    
        a=-20;
    }

    virtual void setA()
    {
    
    
        a = 3;
    }
};

int main()
{
    
    
    Base *ax = new A();
    Base *bx = new B();
    Base *aClass =  ax;
    Base *bClass = bx;
    printf("a value of a construct %d\n", aClass->a);
    printf("a value of b construct %d\n", bClass->a);
    
    aClass->setA();
    bClass->setA();
    printf("a value of a %d\n", aClass->a);
    printf("a value of b %d\n", bClass->a);
    delete aClass;
    return 0;
}

2. 若在基类析构函数前加上Virtual

class Base
{
    
    
public:
    int a;
    Base(){
    
    
        a=0;
    }
    virtual ~Base(){
    
    
        printf("base delete");
    }
    virtual void setA()=0;
};