C++实例之虚析构函数

（一）父类的析构函数是虚函数时

// Test1.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>

using namespace std;

class ClxBase
{
public:
    ClxBase() { cout << "Output from the constructor of class ClxBase!" << endl; };
    virtual ~ClxBase() { cout << "Output from the destructor of class ClxBase!" << endl; };
    virtual void DoSomething() { cout << "Do something in class ClxBase!" << endl; };
};

class ClxDerived : public ClxBase
{
public:
    ClxDerived() { cout << "Output from the constructor of class ClxDerived!" << endl; };
    ~ClxDerived() { cout << "Output from the destructor of class ClxDerived!" << endl; }; 
    void DoSomething() { cout << "Do something in class ClxDerived!" << endl; };
};

/* 情形一
// Output from the constructor of class ClxBase!
// Do something in class ClxBase!
// Output from the destructor of class ClxBase!

int _tmain(int argc, _TCHAR* argv[])
{
	ClxBase pTest;
	pTest.DoSomething();
	return 0;
}
*/


/* 情形二
// 输出为：
// Output from the constructor of class ClxBase!
// Output from the constructor of class ClxDerived!
// Do something in class ClxDerived!

int _tmain(int argc, _TCHAR* argv[])
{
	ClxBase *pTest = new ClxDerived;
	pTest->DoSomething();
	return 0;
}
*/

/* 情形三
// 输出为：
// Output from the constructor of class ClxBase!
// Output from the constructor of class ClxDerived!
// Do something in class ClxDerived!
// Output from the destructor of class ClxDerived!
// Output from the destructor of class ClxBase!

int _tmain(int argc, _TCHAR* argv[])
{
	ClxBase *pTest = new ClxDerived;
	pTest->DoSomething();
	delete pTest;
	return 0;
}
*/

/* 情形四  
// Output from the constructor of class ClxBase!  
// Output from the constructor of class ClxDerived!  
// Do something in class ClxDerived! 
// Output from the destructor of class ClxDerived!   
// Output from the destructor of class ClxBase!   
*/ 

int _tmain(int argc, _TCHAR* argv[])  
{  
    ClxDerived pTest;  
    pTest.DoSomething();  
    return 0;  
}  
 

（二）父类的析构函数不是虚函数时

// Test2.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>

using namespace std;

class ClxBase
{
public:
    ClxBase() { cout << "Output from the constructor of class ClxBase!" << endl; };
    ~ClxBase() { cout << "Output from the destructor of class ClxBase!" << endl; };
    virtual void DoSomething() { cout << "Do something in class ClxBase!" << endl; };
};

class ClxDerived : public ClxBase
{
public:
    ClxDerived() { cout << "Output from the constructor of class ClxDerived!" << endl; };
    ~ClxDerived() { cout << "Output from the destructor of class ClxDerived!" << endl; }; 
    void DoSomething() { cout << "Do something in class ClxDerived!" << endl; };
};

/* 情形三
// 输出为：
// Output from the constructor of class ClxBase!
// Output from the constructor of class ClxDerived!
// Do something in class ClxDerived!
// Output from the destructor of class ClxDerived!
*/

int _tmain(int argc, _TCHAR* argv[])
{
	ClxBase *pTest = new ClxDerived;
	pTest->DoSomething();
	delete pTest;
	return 0;
}

可见如果父类的析构函数没有定义为虚函数的话，当用父类指针指向子类对象的时候，delete父类指针，只会调用父类中的析构函数，不会调用子类中的析构函数。