C++太多的析构函数称为这么少的对象

Question

这是代码(也在http://pastebin.com/yw5z2hnG):

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

class X
{
    public:
    int i;
    X();
    ~X();
};

X::X()
{
    i = 1;
    cout << "---constructor" << '\n';
}

X::~X()
{
    cout << "***desctructor" << '\n';
}

int main()
{
    vector<X> *vx = new vector<X>;
    cout << "------------------------------------" << endl;
    vx->push_back(X());
    vx->push_back(X());
    vx->push_back(X());
    vx->push_back(X());
    vx->push_back(X());
    cout << "------------------------------------" << endl;
    delete vx;
}

我得到的输出为:

------------------------------------
---constructor
***desctructor
---constructor
***desctructor
***desctructor
---constructor
***desctructor
***desctructor
***desctructor
---constructor
***desctructor
---constructor
***desctructor
***desctructor
***desctructor
***desctructor
***desctructor
------------------------------------
***desctructor
***desctructor
***desctructor
***desctructor
***desctructor

我不明白为什么这么多的析构函数被称为.

Answer 1

如果您定义自己的复制构造函数,您将看到正在构造的其他对象:

class X
{
    public:
    int i;
    X(const X&);
    X();
    ~X();
};

X::X(const X& x) : i( x.i )
{
    cout << "---copy constructor\n";
}

// ... rest as before

如果您没有声明自己的日志,编译器将提供一个不执行日志记录的复制构造函数.