Improve reasoning and examples for F.48 #2100
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cubbimew
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Jun 24, 2023
CppCoreGuidelines.md
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| { | ||
| S result; | ||
| return std::move(result); | ||
| } | ||
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| ##### Example, good | ||
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| S f() | ||
| // RVO: guaranteed move elision when a temporary is returned |
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language lawyers will argue that C++17 prvalue return is not an optimization and so not "RVO"
Perhaps omit it and just focus on returning local variables?
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You're right, the standard doesn't call it RVO or NRVO, it only says that returning is copy-initialization of the returned object. Nested prvalue initializations like T(T(T(T(...))))) are just elided to one T().
I think it would be best to remove the explicit mention of RVO and NRVO from the diff, but keep the rest of the comment.
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Editors call: Thanks! We like the PR with Sergey's suggested change, Sergey please make it and merge. |
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The reasoning in F.48 is misleading because it only refers to guaranteed copy elision, but the example listed underneath shows NRVO, for which this elision is not guaranteed.
I think it the reasoning is much better if it is made clear to the reader that a return statement will always move local variables. It is also helpful to distinguish between RVO and NRVO in the example, as the two have optimization differences.