Remove std::move to support copy elision #67
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
According to the standard, copy elision is allowed (before C++17) or required (since C++17) in the following situation: In the initialization of an object, when the source object is a nameless temporary and is of the same class type (ignoring cv-qualification) as the target object. When the nameless temporary is the operand of a return statement, this variant of copy elision is known as RVO, "return value optimization". Unfortunately, using std::move() will block this optimization when initializing an object, so it should not be used. Removing it allows the target object to be constructed in-place rather than being copied using the copy constructor.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
According to the standard, copy elision is allowed (before C++17) or required (since C++17) in the following situation:
In the initialization of an object, when the source object is a nameless temporary and is of the same class type (ignoring cv-qualification) as the target object. When the nameless temporary is the operand of a return statement, this variant of copy elision is known as RVO, "return value optimization".
Unfortunately, using std::move() will block this optimization when initializing an object, so it should not be used. Removing it allows the target object to be constructed in-place rather than being copied using the copy constructor.