虚基类构造函数执行顺序

#include <iostream>

using namespace std;

class stream

{

public:

　　stream(){cout<<"stream constructer"<<endl;

　　~stream(){cout<<"stream destructer"<<endl;

};

 

class iistream : virtual stream

{

public:

　　iistream(){cout<<"iistream constructer"<<endl;

　　~iistream(){cout<<"iistream destructer"<<endl;

};

 

class oostream : virtual stream

{

public:

　　oostream(){cout<<"oostream constructer"<<endl;

　　~oostream(){cout<<"oostream destructer"<<endl;

};

 

class iiostream:public iistream, public oostream

{

public:

　　iiostream(){cout<<"iiostream constructer"<<endl;

　　~iiostream(){cout<<"iiostream destructer"<<endl;

};

 

int main()

{

　　iiostream oo;

　　return 0;

}

 

输出结果：

stream constructer

iistream constructer

oostream constructer

iiostream constructer

 

iiostream deconstructer

oostream deconstructer

iistream deconstructer

stream deconstructer

 

解释：

1. 虚基类构造函数会最先执行；

2. 派生类istream、ostream、iiostream都含有一个指向虚基类的vptr；