Re: returning references

From:

=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 04 Jan 2008 01:43:32 GMT

Message-ID:

<8bgfj.2409$R_4.1987@newsb.telia.net>

On 2008-01-04 01:26, pauldepstein@att.net wrote:

Below is posted from a link for Stanford students in computer
science.

QUOTE BEGINS HERE
Because of the risk of misuse, some experts recommend never returning
a
reference from a function or method.
QUOTE ENDS HERE

I have never heard anyone else say that it is a problem for a function
to return a reference. Are there really experts who object, or is
this nothing other than the commonplace observation that reference-
returning is a somewhat difficult concept that needs to be learned
carefully? (I am just learning about this now.) Assuming programmers
have some degree of competence and are able to avoid returning
references to locals and so on, what (if anything) are the pitfalls?

As far as I know there is only one pitfall, and that is returning a
reference to a variable local to the function, like so:

int& foo(int i)
{
  int r = i+i;
  return r;
}

int main()
{
  int& twice = foo(5);
}

Since r is a local variable to foo() it will go out of scope as soon as
foo() is done executing, this means that the reference returned refers
to a variable that no longer exists.

On the other hand there are a number of valid reasons to return a
reference from a function, a function that returns an element from a
collection is a good example (look at the at() function in std::vector).

--
Erik Wikstr?m