C++之虚析构函数

代码一、

#include <iostream>
using namespace std;

class Base
{
public:
    Base(){};
    ~Base()
    {
        cout << "Base destructor." << endl;
    };
};

class Derive : public Base
{
public:
    Derive(){};
    ~Derive()
    {
        cout << "Derive destructor." << endl;
    };
};

int main(int argc, char **argv)
{
    cout << "delete pBase" << endl;
    Base *pBase = new Derive();
    delete pBase;

    cout << "delete pDerive" << endl;
    Derive *pDerive = new Derive();
    delete pDerive;
    return 0;
}

运行结果:

代码二、

#include <iostream>
using namespace std;

class Base
{
public:
    Base(){};
    virtual ~Base()
    {
        cout << "Base destructor." << endl;
    };
};

class Derive : public Base
{
public:
    Derive(){};
    ~Derive()
    {
        cout << "Derive destructor." << endl;
    };
};

int main(int argc, char **argv)
{
    cout << "delete pBase" << endl;
    Base *pBase = new Derive();
    delete pBase;

    cout << "delete pDerive" << endl;
    Derive *pDerive = new Derive();
    delete pDerive;
    return 0;
}

运行结果:

结论:

基类的析构函数是为了,删除指向派生类对象的基类指针时,会调用派生类的析构函数。

只要派生类析构函数被调用,之后必定调用基类的析构函数。

疑问:按照C++的内存布局,虚函数是由放在虚函数表中的函数指针指向的,由函数指针间接调用的。而且派生类中如果定义了虚函数,那么虚函数表中相应存放指向基类虚函数的指针就会被指向派生类虚函数的指针替换。以此实现多态,即用基类指针调用派生类函数。

但是析构函数是特殊呢,因为派生类的析构函数和基类的析构函数并不重名,因此可能不是这样处理的,此处还需要深究。

posted @ 2015-03-19 11:08  冷冰若水  阅读(299)  评论(0编辑  收藏  举报