深入C++中构造函数、拷贝构造函数、赋值操作符、析构函数的调用过程总结

    #include "stdafx.h" 
    #include <iostream> 
    using namespace std; 
    class B 
    { 
    public: 
        B():data(0)    //默认构造函数 
        {  
            cout << "Default constructor is called." << endl; 
        } 
        B(int i):data(i) //带参数的构造函数 
        { 
            cout << "Constructor is called." << data << endl; 
        } 
        B(B &b)   // 复制（拷贝）构造函数 
        { 
            data = b.data; cout << "Copy Constructor is called." << data << endl; 
        } 
        B& operator = (const B &b) //赋值运算符的重载 
        { 
            this->data = b.data; 
            cout << "The operator \"= \" is called." << data << endl; 
            return *this; 
        } 
        ~B() //析构函数 
        { 
            cout << "Destructor is called. " << data << endl; 
        } 
    private: 
        int data; 
    }; 

    //函数，参数是一个B类型对象，返回值也是一个B类型的对象 
    B fun(B b) 
    { 
        return b; 
    } 

    //测试函数 
    int _tmain(int argc, _TCHAR* argv[]) 
    { 
        fun(1); 
        cout << endl; 

        B t1 = fun(2); 
        cout << endl; 

        B t2; 
        t2 = fun(3); 

        return 0; 
    } 

    Constructor is called.1             //用1构造参数b    
    Copy Constructor is called.1      //用b拷贝构造一个临时对象，因为此时没有对象来接受fun的返回值    
    Destructor is called. 1            //参数b被析构    
    Destructor is called. 1             //临时对象被析构 
    Constructor is called.2                  //用2构造参数b       
    Copy Constructor is called.2           //用b拷贝构造t1，此时调用的是拷贝构造函数    
    Destructor is called. 2                  //参数b被析构 
    Default constructor is called.             //调用默认的构造函数构造t2       
    Constructor is called.3                       //用3构造参数b       
    Copy Constructor is called.3             //用b拷贝构造一个临时对象       
    Destructor is called. 3                        //参数b被析构       
    The operator "= " is called.3              //调用=操作符初始化t2，此时调用的是赋值操作符    
    Destructor is called. 3                         //临时对象被析构       
    Destructor is called. 3                         //t2被析构       
    Destructor is called. 2                         //t1被析构       
    请按任意键继续. . .