[Development] qMoveToConst helper for rvalue references to movable Qt containers?

[Giuseppe D'Angelo]

Il 28/10/18 11:22, Elvis Stansvik ha scritto:
> Though hmm, even if we'd lose move-construction, for the copy we'd get
> instead, wouldn't copy elision kick in and elide it? So we wouldn't
> have to pay for the ref count up/down?

GCE is one thing, and applies in a very specific case (returning a 
prvalue).

(N)RVO is another thing, and may or may not be applied depending on 
whether the compiler *can* apply it and *will* apply it.

In the general case, you won't have either, and thus having a move will 
be cheaper than a copy. Returning const objects for types which benefit 
from moves is a bad idea.

My 2 c,

-- 
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts

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