什么时候在`std :: move()`函数中调用move构造函数? [英] When is the move constructor called in the `std::move()` function?

问题描述

函数std::move()定义为

template<typename T>
typename std::remove_reference<T>::type&& move(T && t)
{ 
    return static_cast<typename std::remove_reference<T>::type&&>( t ); 
}

我可以想象在四个地方调用move构造函数:

There are four places where I can imagine the move constructor to be called:

1. 传递参​​数时.
2. 执行投射时.
3. 返回结果时.
4. 不在std::move()函数本身中，但可能位于返回的引用最终到达的位置.

1. When the parameter is passed.
2. When the cast is performed.
3. When the result is returned.
4. Not in the std::move() function itself but possibly at the place where the returned reference ultimately arrives.

我敢打赌第4位，但我不确定100％，因此请解释您的答案.

I would bet for number 4, but I'm not 100% sure, so please explain your answer.

推荐答案

没有进行任何移动构造. std::move()接受引用并返回引用. std::move()基本上只是强制转换.

There is no move construction going on. std::move() accepts a reference and returns a reference. std::move() is basically just a cast.

您的猜测4.是正确的(假设您实际上实际上是在最后调用move构造函数).

Your guess 4. is the right one (assuming that you are actually calling a move constructor in the end).

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