Why is `std::move` Called `std::move` if it Doesn't Actually Move Anything?

Why is std::move Named std::move?

The std::move function, despite its name, doesn't actually move anything at all. It merely converts an lvalue (an expression referring to an object) to an rvalue (an expression representing a temporary object). This conversion is performed through a cast to the xvalue category, which is distinct from lvalues and prvalues.

The reason for this naming choice goes back to the history of the concept. Originally, the move operation was introduced as a way to efficiently swap values without copying them. The early syntax for this involved casting lvalues to rvalues using static_cast. To improve readability and convey the intent of these casts, the move keyword was introduced as syntactic sugar for static_cast.

In the context of the time, using the term "move" was meant to indicate the purpose of these casts: to enable move semantics. The consequence is that the code conveys not the precise technical action (casting to an rvalue), but rather the desired outcome (moving the object).

Over the years, the concept of lvalues and rvalues has evolved into the value categories we have today, with xvalues representing objects that have been cast to rvalues. As a result, the move keyword could be seen as misleading, as it only implies an action that may or may not occur under the hood.

However, the choice of using the move keyword has been maintained to preserve readability and avoid the confusion that could arise from unfamiliar syntax like cast_to_xvalue. The std::move function remains a valuable utility that allows programmers to express move semantics concisely, even if its name may not perfectly capture the technical details of its operation.

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