类的析构及虚析构探究

正常析构及析构在多继承基类中产生的不足

#include <iostream>
using namespace std;
//////////////////////////////////////////////////////////////////////////
// 正常析构解决不了父类new子类时析构函数调用的问题
// 也就是构造函数被调用了四次，而析构函数却被调用了三次
//
// 正常析构不能解决父子类同台出现的某些极端情况
/*
class A
class B
class A
class B
first delete A
class ~A
second delete B
class ~B
class ~A
*/
class A
{
public:
    A()
    {
        cout << "class A" << endl;
    }
    ~A()
    {
        cout << "class ~A" << endl;
    }
};
class B: public A
{
public:
    B()
    {
        cout << "class B" << endl;
    }
    ~B()
    {
        cout << "class ~B" << endl;
    }
};
int main1()
{
    A* a = new B();
    B* b = new B(); 
    cout << "first delete A" << endl;
    delete a;
    cout << "second delete B" << endl;
    delete b;
    return 0;
} 

虚析构能解决上述所产生的问题

#include <iostream>
using namespace std;
//////////////////////////////////////////////////////////////////////////
// 用虚基类析构函数能解决正常析构函数不能解放完的问题
/*
class AA
class BB
class AA
class BB
fir delete delete
class ~BB
class ~AA
sec delete delete
class ~BB
class ~AA
*/
class AA
{
public:
    AA()
    {
        cout << "class AA" << endl;
    }
    virtual ~AA()
    {
        cout << "class ~AA" << endl;
    }
};
class BB :public AA
{
public:
    BB()
    {
        cout << "class BB" << endl;
    }
    ~BB()
    {
        cout << "class ~BB" << endl;
    }
};
int main()
{
    AA* a = new BB();
    BB* b = new BB();
    cout << "fir delete delete" << endl;
    delete a;
    cout << "sec delete delete" << endl;
    delete b;
    return 0;
}

来自为知笔记(Wiz)