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

From:

"Niels Dekker - no reply address" <noreply@this.is.invalid>

Newsgroups:

comp.lang.c++

Date:

Thu, 28 May 2009 12:32:26 +0200

Message-ID:

<4a1e683c$0$184$e4fe514c@news.xs4all.nl>

Balog Pal wrote:

"Niels Dekker - no reply address"

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).

I too, often use that. Looking around the web it seems not a
well-known feature of C++ (that the life of bound object is extended
to life of ref...) but there are no other problems I'm aware of.

IMO don't sweat it, inless you see some real point against using the
ref form, use that, it won't let you down. :)

Thanks, Balog. Unfortunately there is a real point against this form:
if you're calling a virtual function of Foo through a reference to a
temporary Foo object, it won't be inlined by the compiler. At least, not
by MSVC 2008 SP1, as I concluded from a little test of mine. See also
http://groups.google.com/group/microsoft.public.vc.language/msg/e28eb112ae9dc08c

Kind regards, Niels