At Fri, 28 May 2010 21:03:24 +0200, Thomas Klimpel wrote:
David Abrahams wrote:
You are claiming that some aspect of that signature causes RVO not to happen? What aspect?
I understand you want to comment on what could be FUD, but why do you ask about the "signature" then?
Because that's all you showed in the first message? There was no body.
A static member function is just a function to the compiler. AFAIK, the only compiler in recent memory that doesn't have NRVO (yet) is Clang. And they're working on it. What compiler are you talking about?
Same here, I appreciate it that you try to clarify my misconceptions, but I was talking about RVO here, not NRVO.
In the function you wrote in your previous message: X X::create() { X x; return x; // passing value form static memeber-fn } x is named. Its name is “x” :-). Optimizing away the copy requires the Named Return Value Optimization (NRVO), not the Unnamed Return Value Optimization (URVO). “RVO” by itself refers to both of them.
Please also understand my position that everybody is allowed to make mistakes, but he shouldn't blame Boost.Move or its documentation for it. The linker had complained about a missing symbol, and this means that it had indeed generated the corresponding constructor call. This might be related to compiling in debug mode with msvc-9.0. I don't know whether gcc-4.5 or msvc-10.0 implement NRVO even in debug mode. However, this should be easy to find out if it's important for this discussion.
Sorry, I haven't followed the rest of the discussion so the above doesn't mean much to me. -- Dave Abrahams Meet me at BoostCon: http://www.boostcon.com BoostPro Computing http://www.boostpro.com