Re: Re: [boost] Shared_ptr "mini garbage collector"

From: William E. Kempf (wekempf_at_[hidden])
Date: 2003-01-07 12:18:40

> From: David Abrahams <dave_at_[hidden]>
> "William E. Kempf" <wekempf_at_[hidden]> writes:
> > From: "Peter Dimov" <pdimov_at_[hidden]> 
> >> One possible approach is to return a list of references to the
> >> "offending" shared_ptr instances to the user, who can then reset()
> >> them as appropriate.  Actually it's not as simple as that since a
> >> reset() can invalidate some of the returned references; the
> >> shared_ptr instances would first need to be copied to a temporary
> >> container, the originals reset(), and the temporary container
> >> destroyed, but the general idea is the same.
> >
> > This just pushes the issue off on the end user... who may not be any
> > more capable of dealing with the problem either.  If he can't do a lot
> > of book keeping to handle the circular problem, then pushing it off on
> > him is not much help.  And if he can do the book keeping, there's
> > probably a solution he can code into the destructors themselves.
> 
> What Python does is to collect only the memory from cycles, without
> calling __del__ (the equivalent of a destructor).  It also provides a
> similar function which gets you a list of the objects that are in
> cycles.

A solution like this for C++ could easily result in memory leaks.  If the object in question did it's own internal memory allocations which would normally be cleaned up in the destructor, you've got a leak when the "collector" releases the object's memory with out calling its destructor.

William E. Kempf
wekempf_at_[hidden]