Re: return value optimization vs. returning a boost::shared_ptr of container

From:

"Bo Persson" <bop@gmb.dk>

Newsgroups:

comp.lang.c++.moderated

Date:

Wed, 16 Jun 2010 08:01:29 CST

Message-ID:

<87rinsFpgjU1@mid.individual.net>

{ note to moderators redacted. -mod }

Daniel Kr?gler wrote:

On 15 Jun., 21:59, Jeff Flinn <TriumphSprint2...@hotmail.com> wrote:

Goran wrote:

[..]

I think so, too, but you have swap method, which is efficient. So:

LibMapType map;
map.swap(LibFuncReturningMap(...));

IIRC, that won't compile on gcc 4.0.1 for me(but does with MSVC's
extensions). I need to:

LibMapType map;
LibFuncReturningMap(...).swap(map);

Yeah, this is the only correct way, because swap requires a
(mutable) lvalue, but above an rvalue was provided. It is a
shame, that accepting rvalues at these locations still belong
to the default settings of MSVC...

Who runs compilers with default settings? :-) Those are permissive
enough to minimize the number of support cases for the product. A
business optimization.

If we compile with the proper setting - highest warning level - the
compiler will tell us that "the type conversion is not allowed by the
C++ standard".

http://msdn.microsoft.com/en-us/library/186yxbac%28VS.80%29.aspx

Bo Persson

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