C移动赋值触发器首先移动构造函数

#include <iostream>    

class C {

public:

  ~C() { std::cout << this << " destructorn"; }

  C() { std::cout << this << " constructorn"; }

  C(C&& rhs) {
    std::cout << &rhs << " rhsn";
    std::cout << this << " move constructorn";
  }

  C& operator=(C&& rhs) {
    std::cout << &rhs << " rhsn";
    std::cout << this << " move assignmentn";
    return *this;
  }

};

C make_one() {
  C tmp;
  return tmp;
}

int main() {

  std::cout << "move constructor:n";
  C c1(make_one());
  std::cout << &c1 << " &c1nn";

  std::cout << "move assignment:n";
  C c2;
  c2 = make_one();
  ...
}

输出：

move constructor:
000000000021F9B4 constructor         // tmp constructed in make_one()
000000000021F9B4 rhs                 // return triggers tmp being passed to ...
000000000021FA04 move constructor    // ... c1's move constructor (see below)
000000000021F9B4 destructor          // tmp destructs on going out of scope
000000000021FA04 &c1                 // (confirmed c1's address)

move assignment:
000000000021FA24 constructor         // c2 constructed
000000000021F9B4 constructor         // tmp constructed in make_one() again
000000000021F9B4 rhs                 // tmp passed to ...
000000000021FA34 move constructor    // ... a new object's move constructor
000000000021F9B4 destructor          // tmp destructs on going out of scope
000000000021FA34 rhs                 // new object passed to ...
000000000021FA24 move assignment     // .. c2's move assignment operator
000000000021FA34 destructor          // new object destructs
...

移动分配似乎首先触发移动构造函数并创建一个额外的对象.这是正常的吗？我希望(通过类比复制赋值)将tmp直接传递给c2的移动赋值.

[Visual Studio Express 2013]