虚析构函数必要性

虚析构函数必要性

未声明virtual：

#include  < iostream >
#include  < cstdlib >
using   namespace  std;

class   base
{
    public:
        ~base(){cout<<"base destr"<<endl;}
} ;

class  derived : public   base
{
    public:
        ~derived(){cout<<"derived destr"<<endl;}
} ;

int  main()
{
    base *pb = new derived();
    delete pb;
    system("PAUSE");
    return 0;
}

声明virtual：

#include  < iostream >
#include  < cstdlib >
using   namespace  std;

class   base
{
    public:
        virtual ~base(){cout<<"base destr"<<endl;}
} ;

class  derived : public   base
{
    public:
        virtual ~derived(){cout<<"derived destr"<<endl;}
        
        //~derived(){cout<<"derived destr"<<endl;} //不加virtual也可以，默认会继承 
} ;

int  main()
{
    base *pb = new derived();
    delete pb;
    system("PAUSE");
    return 0;
}