析构函数怎么多调用2次？

chenhao_no1

代码如下：
#include <map>
#include <algorithm>
#include <iostream>

class A
{
    public:
        A( void)
        {
            std::cout << "A::A() is called\n";
        }

        ~A()
        {
            std::cout << "A::~A() is called\n";
        }
};

int main( void)
{
    std::map< int, A> oMap;

    std::pair<int, A> o( 1, A());
    oMap.insert(o);

    std::cout << "----------------------------\n";
    oMap.clear();
    return 0;
}


输出如下：
A::A() is called
A::~A() is called
----------------------------
A::~A() is called
A::~A() is called
A::~A() is called

疑问是：红色的输出为什么会有？谢谢！

杨二

不奇怪，stl里面copy的东西很多，
楼主加个构造函数看看构造了几遍
A( A const &a )
        {
            std::cout << "A::A(a) is called\n";
        }

chenhao_no1

3xs, you are right!