c++ virtual 析构函数

今天试了下c++ 虚析构函数。

虚析构函数的目的是当一个基类指针指向一个派生类指针时，当delete该基类指针时，也会调用派生类的析构函数。

具体看如下代码

 

#include <iostream>

using namespace std;

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

    virtual ~base()
    {
        cout << "base: Destructor" << endl;
    };
};

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

    virtual ~derived()
    {
        cout << "derived: Destructor" << endl;
    }
};

int    main()
{
    base *b = NULL;

    derived *p = new derived;

    b = p;

    if( b != NULL )
    {
        delete b;
    }

    return 0;
}

函数输出：

base: Constructor

Derived: Constructor

Derived: Destructor

base: Destructor

如果base基类中的析构函数没有添加virtual关键字，函数输出如下：

base: Constructor

Derived: Constructor

base: Destructor

可以看出，当基类的析构函数添加了virtual关键字后，当其delete时，也会调用子类的析构函数。