Re: Returning a reference to a temporary object

From:

"Catalin Pitis" <cata.pitis@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

1 Jun 2006 07:23:09 -0400

Message-ID:

<1149139834.035895.160860@u72g2000cwu.googlegroups.com>

Thanks

I wouldn't use the code that I presented (holding reference to the
returned object), but I would use your code instead (copying the
returned object). However, I encountered this code in some third party
library that I have to use and which has some "strange" behavior from
time to time, so I wanted to eliminate one possible source.

Regards,
Catalin

Victor Bazarov a scris:

Catalin Pitis wrote:

I have a piece of code looking like this:

#include <iostream>
#include <string>

using namespace std;

string foo()
{
   return "Something";
}

int main( int, char*[])
{
   const std::string& value = foo(); // This is the interest point
   /// do something here....
   return 0;
}

I've tested the code with MS VC 8.0 and it seems that allows me to
hold a const reference to a temporary object without crashing (both
debug and release targets).

However, is this allowed, according to the standard? Can I use it like
this?

Yes, it is allowed. Yes, you can. You should know, however, that with
return value optimization (RVO) the compiler can forgo creation of extra
temporary objects if you write

std::string value = foo(); // not a reference

the benefit here is that 'value' can be reused.
V

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