RVO vs. `std::move` in C 11: When Should I Use Each for Optimized Return Values?

Understanding Return Value Optimization and Move Semantics in C 11

When working with return values in C , developers may encounter a choice between return value optimization (RVO) and explicitly moving the value using std::move. Understanding the differences between these two techniques is crucial for optimizing code.

Return Value Optimization (RVO)

RVO is a compiler optimization technique that eliminates unnecessary object copying by returning an object by reference instead of value. It works when the following conditions are met:

• The return type is an object type.
• The object is created in the same function that returns it.
• The object is not moved or modified before it is returned.

std::move

std::move is a C 11 keyword used to explicitly move an object. Moving an object means transferring its ownership from one variable to another without copying it. This can be beneficial in cases where copying the object would be inefficient or not desired.

Choice between RVO and Move Semantics

When deciding whether to use RVO or std::move, it is important to consider the following guidelines:

• Always Use RVO When Possible: RVO is generally preferable to std::move because it allows the compiler to perform the optimization automatically.
• Use std::move to Prevent Copy: If you want to explicitly prevent copy elision, you should use std::move to force the compiler to move the object. This can be useful in cases where copy elision could lead to unexpected behavior.

In the example code provided, using RVO (the first method) is the recommended approach because it allows the compiler to optimize the return value. Explicitly using std::move (the second method) actively prevents copy elision, which is not necessary and could lead to performance issues.

The above is the detailed content of RVO vs. `std::move` in C 11: When Should I Use Each for Optimized Return Values?. For more information, please follow other related articles on the PHP Chinese website!