Newsgroups: alt.lang.design,comp.lang.c,comp.lang.c++,comp.lang.lisp
Path: cantaloupe.srv.cs.cmu.edu!das-news2.harvard.edu!news2.near.net!howland.reston.ans.net!ix.netcom.com!netcom.com!hbaker
From: hbaker@netcom.com (Henry G. Baker)
Subject: Re: Reference Counting (was Re: Searching Method for Incremental Garbage Collection)
Message-ID: <hbakerD034p9.Hq8@netcom.com>
Organization: nil
References: <TFB.94Nov21091959@burns.cogsci.ed.ac.uk> <RFB.94Nov27213114@cfdevx1.lehman.com> <3be0mh$1p7@gamma.ois.com>
Date: Wed, 30 Nov 1994 14:39:09 GMT
Lines: 26
Xref: glinda.oz.cs.cmu.edu comp.lang.c:118455 comp.lang.c++:100987 comp.lang.lisp:15867

In article <3be0mh$1p7@gamma.ois.com> beckwb@ois.com (R. William Beckwith) writes:
>Rick Busdiecker (rfb@lehman.com) wrote:
>: In article <3b9gsg$hv8@nntp.crl.com> Richard Berman <sts@crl.com> writes:
>
>: The point is that reference counting does not solve it.  You have to
>: add some mechanism that is not reference counting to avoid making
>: circular data structures into memory leaks.
>
>RCing can work for circular data structures.
>
>You must define `weak' references.  Weak references are non-sustaining
>references.  When you build doubly-linked lists or tree structures,
>use strong references for the forward (down) references and weak
>references for the backward (up) references.

I think that I understand your 'weak reference' scheme.  However,
how does one know when tracing a 'weak reference' whether the target
still exists, or has been recycled for another purpose.

  -- Sleepless in Sepulveda

Henry Baker
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