Without Virtual Destructor(虚析构函数)

class A{public:    int a = 3;    A()    {        cout <<"A()..."<< endl;    }     ~A()    {        cout << "~A()..." << endl;    }};class B : public A{public:    int b;    B(){        cout << "B()..." << endl;    }    ~B(){        cout << "~B()..." << endl;    }};void main(){    A *a = new B;    delete a;    system("pause");} result: A()... B()... ~A()... Press any key to continue . . . 没有~B（），内存泄漏！！

Virtual Destructor(虚析构函数)

class A{public:    int a = 3;    A()    {        cout <<"A()..."<< endl;    }    virtual ~A()    {        cout << "~A()..." << endl;    }};class B : public A{public:    int b;    B(){        cout << "B()..." << endl;    }    ~B(){        cout << "~B()..." << endl;    }};void main(){    A *a = new B;    delete a;    system("pause");} result:

　A()...

　B()...

　~B()...

　~A()...

　Press any key to continue . . .

防止内存泄漏！！