Re: The best way to retrieve a returned value... by const reference?

From:
Pete Becker <pete@versatilecoding.com>
Newsgroups:
comp.lang.c++
Date:
Wed, 27 May 2009 16:26:50 -0400
Message-ID:
<l96dnWAPlN6WP4DXnZ2dnUVZ_h2dnZ2d@giganews.com>
Niels Dekker - no reply address wrote:

Suppose you're calling a function that returns an object "by value".
When const access to the returned value is sufficient, you have the
choice between binding the returned object to a const-reference, and
copying the object to a local (const) variable, using copy-initialization:

 class Foo { /* ... */ };
 Foo GetFoo(void);

 const Foo& constReference = GetFoo(); // Choice #1
 const Foo constValue = GetFoo(); // Choice #2

Personally, I have the habbit to bind such an object to a
const-reference (choice #1). Thereby I hope to avoid an expensive
copy-construction, which /might/ take place when you use
copy-initialization (choice #2).


I don't think that this avoids the copy. The returned value has to live
somewhere in the current stack frame, so it has to be copied into a
temporary object, where "copied" means the same things as in #2. The
only difference that I can see between #1 and #2 is that the resulting
object has a name.

--
   Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of
"The Standard C++ Library Extensions: a Tutorial and Reference"
(www.petebecker.com/tr1book)

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