复制构造函数和赋值运算符

我编写了以下程序来测试何时调用复制构造函数以及何时调用赋值运算符:

#include 

class Test
{
public:
    Test() :
        iItem (0)
    {
        std::cout << "This is the default ctor" << std::endl;
    }

    Test (const Test& t) :
        iItem (t.iItem)

    {
        std::cout << "This is the copy ctor" << std::endl;
    }

    ~Test()
    {
        std::cout << "This is the dtor" << std::endl;
    }

    const Test& operator=(const Test& t)
    {
        iItem = t.iItem;    
        std::cout << "This is the assignment operator" << std::endl;
        return *this;
    }

private:
    int iItem;
};

int main()
{
    {
        Test t1;
        Test t2 = t1;
    }
    {
        Test t1;
        Test t2 (t1);
    }
    {
        Test t1;
        Test t2;
        t2 = t1;
    }
}

这将导致以下输出(只需添加empy行,以使其更易于理解):

doronw@DW01:~$ ./test
This is the default ctor
This is the copy ctor
This is the dtor
This is the dtor

This is the default ctor
This is the copy ctor
This is the dtor
This is the dtor

This is the default ctor
This is the default ctor
This is the assignment operator
This is the dtor
This is the dtor

第二个和第三个集合的行为与预期一致,但在第一个集合中,即使使用了赋值运算符,也会调用复制构造函数。

这个行为是C++标准的一部分还是仅仅是一个聪明的编译器优化(我使用的是GCC 4.4.1)