C++虚析构函数

//文件 Clx.h
#include "iostream.h"

class ClxBase
{
public:
    ClxBase() {};
    virtual ~ClxBase() {
        cout <<"Output from the destructor of class ClxBase!"<    };

    virtual void DoSomething() {
        cout << "Do something in class ClxBase!" << endl;
    };
};

class ClxDerived : public ClxBase
{
public:
    ClxDerived() {};
    ~ClxDerived() {
        cout << "Output from the destructor of class ClxDerived!" << endl;
    };

    void DoSomething() {
        cout << "Do something in class ClxDerived!" << endl;
    };
};

//文件test.cpp
#include "Clx.h"

int main(){

    ClxBase *pTest = new ClxDerived;
    pTest->DoSomething();
    delete pTest;

    printf("***************\n")
   
    ClxDerived a;
    a.DoSomething();
    return 0;
}

上面程序的输出结果为：

Do something in class ClxDerived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!
***************
Do something in class ClxDerived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!

如果把ClxBase类中的虚析构函数改为 非虚析构函数，则输出结果为：

Do something in class ClxDerived!
Output from the destructor of class ClxBase!
***************
Do something in class ClxDerived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!


我们由此可以知道虚析构函数的使用场合：当用一个基类的指针删除一个派生类的对象时，为了让派生类的析构函数会被调用，需要基类的析构函数为虚函数。