Re: Just want to make sure...

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 29 Apr 2009 02:07:46 -0700 (PDT)

Message-ID:

<2df71e5e-6f1c-439b-afb7-22b92dfeb310@v23g2000pro.googlegroups.com>

On Apr 28, 9:20 pm, Noah Roberts <n...@nowhere.com> wrote:

Drew Lawson wrote:

In article <49f75393$0$2709$cc2e3...@news.uslec.net>
Noah Roberts <n...@nowhere.com> writes:

#include <iostream>

#include <memory>

struct T {};

std::auto_ptr<T> f() { return new T; }

int main()
{
  std::auto_ptr<T> at = f();

  std::cout << "test\n";
  std::cin.get();
}

The above code should compile and work fine, no? I should
not be getting a crash due to doubly deleted memory
segments...right?

I've used auto_ptr, but never as a return type. I think you
really want to return a T* and store it in auto_ptr.
Otherwise 'at' may be a copy of a temporary auto_ptr.

And that would be bad.

It shouldn't be. The temporary should be assigned to at,
which then holds the ptr while the original temp holds 0.

That's the way VC++ implements it, and that corresponds
literally to what the standard says to do. Practically,
however... is there a possibility of the auto_ptr_ref outliving
the original auto_ptr used to create it? If so, there could be
a serious problem. G++ avoids this by dropping ownership when
the auto_ptr_ref is created. Which of course, will cause a
memory leak if the auto_ptr_ref isn't ultimately used to craete
an auto_ptr.

--
James Kanze (GABI Software) email:james.kanze@gmail.com
Conseils en informatique orient=E9e objet/
Beratung in objektorientierter Datenverarbeitung
9 place S=E9mard, 78210 St.-Cyr-l'=C9cole, France, +33 (0)1 30 23 00 34