[boost] Re: change to linked_ptr release

From: Mark Borgerding (markab_at_[hidden])
Date: 2000-02-07 15:03:48

And as an added bonus; assignments, copy construction and default
construction all take less time.  The savings are between 7% and 20%
less, according to my initial findings.

As far as I can tell, this is because the 'released' bool no longer
needs to be constructed or passed along.

--Mark

"greg colvin" <gcolvi-_at_[hidden]> wrote: 
original article:http://www.egroups.com/group/boost/?start=2129
> I can live with this one.  Thanks.
> 
> From: Mark Borgerding <markab_at_[hidden]>
> > "greg colvin" <gcolvi-_at_[hidden]> wrote: 
> > original article:http://www.egroups.com/group/boost/?start=2125
> > > I still think linked_ptr::release is a dangerous invitation
> > > to dangling pointers.
> > > 
> > 
> > Yes, I tend to agree with you, but I think that release is
important to
> > have.
> > 
> > Maybe we can all be happy ...
> > 
> > I have an idea for defining the behavior of a ref-counted smart
> > pointer's release().  It would give the user the ability to claim
> > responsibility for deletion of the pointer, but only if no other
> > references share the object. i.e. unique() returns true.
> > 
> > so the definition for release becomes
> > 
> > T* linked_ptr::release()
> > {
> >   T * origPtr = 0;
> >   if ( unique() ) {
> >    origPtr = ptr;
> >    ptr = 0;// just give it up without deletion
> >   }else 
> >    reset(0);// take *this out of list, leaving 
> >    // responsibility for deletion to other nodes
> >   return origPtr;// null if not unique
> > }
> > 
> > This approach tends to err on the side of double deletion, as
opposed
> > to dangling pointers.  This should be much easier to catch in
> > debugging, and possibly less dangerous.
> > 
> > returning 0 if the object is not unique allows safe code of the
form 
> > delete mySmartPtr.release();
> > 
> > This approach could also be implemented for the existing shared_ptr.
> > 
> > And yet another bonus, this approach would get rid of the bool
> > "released" member that increases the size of linked_ptr.
> 
>