c++ 拷贝控制

例子：

#include <iostream>
#include <vector>
using namespace std;

struct X
{
    X(){cout << "construct func X()" << endl;}
    X(const X&){cout << "construct func X(const X&)" << endl;}
    X& operator= (const X &rhs){cout << "copy assignment operator = (const X&)" << endl; return *this; }
    ~X(){cout << "deconstructor ~X()" << endl;}
};

void f1(X x)
{}

void f2(X &x)
{}

int main()
{
    cout << "local: " << endl;
    X x;
    cout << endl;

    cout << "Non reference parameter passing" << endl;
    f1(x);
    cout << endl;

    cout << "Reference parameter passing" << endl;
    f2(x);
    cout << endl;

    cout << "Dynamic allocation" << endl;
    X *px = new X;
    cout << endl;

    cout << "Add to container" << endl;
    vector<X> vx;
    vx.push_back(x);
    cout << endl;

    cout << "Free dynamic allocation object" << endl;
    delete px;
    cout << endl;

    cout << "Indirect initialization assignment" << endl;
    X y = x;
    y = x;
    cout << endl;

    cout << "Program over" << endl;
}

分析：

local: 
construct func X()

Non reference parameter passing
construct func X(const X&)//非引用参数传递，拷贝构造函数
deconstructor ~X()//函数结束，调用析构函数

Reference parameter passing
//引用构造函数：传引用，不会调用构造和析构函数

Dynamic allocation
construct func X()//动态分配会调用构造函数

Add to container
construct func X(const X&)//将对象添加到容器中，会调用构造函数

Free dynamic allocation object
deconstructor ~X()//释放动态对象，会调用析构函数

Indirect initialization assignment
construct func X(const X&)//间接初始化，会调用拷贝构造函数
copy assignment operator = (const X&)//间接赋值，会调用赋值构造函数

Program over
deconstructor ~X()
deconstructor ~X()
deconstructor ~X()
// x y vx