From: ludovic.courtes@laas.fr (Ludovic Courtès)
Cc: guile-devel@gnu.org
Subject: Re: [PATCH] Marking weak alist vectors
Date: Wed, 09 Nov 2005 10:03:15 +0100 [thread overview]
Message-ID: <87lkzyyyzw.fsf@laas.fr> (raw)
In-Reply-To: <874q6m7l6d.fsf@zagadka.de> (Marius Vollmer's message of "Wed, 09 Nov 2005 01:51:38 +0200")
Hi Marius,
Marius Vollmer <mvo@zagadka.de> writes:
> I still have to read your patch carefully, but just from your
> description of the problem, I would say that nothing is actually
> wrong. We don't make any guarantees about the sequence in which
> objects are 'freed' that are unreachable.
>
> This should only matter for smobs with their user written FREE
> procedures. The manual says:
[About SMOBs' being freed]
The relevant part of the manual with respect to this issue is the
following (in node `Weak References'):
Weak references let you attach bookkeeping information to data so
that the additional information automatically disappears when the
original data is no longer in use and gets garbage collected. In a weak
key hash, the hash entry for that key disappears as soon as the key is
no longer referenced from anywhere else.
Likewise (in `Object Properties'):
Internally, object properties are implemented using a weak key hash
table. This means that, as long as a Scheme value with property values
is protected from garbage collection, its property values are also
protected. When the Scheme value is collected, its entry in the
property table is removed and so the (ex-) property values are no longer
protected by the table.
IOW, property values are to be "collected" _after_ the Scheme value to
which they are attached has been collected. Admittedly, the manual is
quite fuzzy as to whether "after" means "during the next round of
mark/sweep" or "maybe during the same round of mark/sweep but at least
property values are swept after the Scheme value has been swept".
In any case, if a value P is attached as a property of some object O,
then O should be "collected" _before_ P. In practice, if both O and P
are SMOBs, then this means that O should be "freed" before P.
Please, have a look at the `test-weaks.c' file I posted. It attaches
SMOBs as properties of other SMOBs. And it's maybe clearer than long
explanations. ;-)
Thanks,
Ludovic.
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next prev parent reply other threads:[~2005-11-09 9:03 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-08 17:22 [PATCH] Marking weak alist vectors Ludovic Courtès
2005-11-08 23:51 ` Marius Vollmer
2005-11-09 9:03 ` Ludovic Courtès [this message]
2005-12-06 23:55 ` Marius Vollmer
2005-12-07 10:33 ` Ludovic Courtès
2005-12-13 23:45 ` Marius Vollmer
2005-12-14 9:30 ` Ludovic Courtès
2005-11-09 10:28 ` Han-Wen Nienhuys
2005-11-09 16:28 ` Ludovic Courtès
2005-11-09 18:36 ` Han-Wen Nienhuys
2005-11-09 21:11 ` Kevin Ryde
2005-11-09 22:45 ` Marius Vollmer
2005-11-10 12:11 ` Han-Wen Nienhuys
2005-11-10 9:47 ` [PATCH] Reference leak in `iprin1 ()' Ludovic Courtès
2005-11-12 9:23 ` Neil Jerram
2005-11-14 9:58 ` Ludovic Courtès
2005-11-16 21:18 ` Neil Jerram
2005-11-17 9:54 ` Ludovic Courtès
2005-11-17 18:52 ` Neil Jerram
2005-11-23 10:19 ` [PATCH] Marking weak alist vectors, #2 Ludovic Courtès
2005-11-24 0:59 ` Han-Wen Nienhuys
2005-11-24 9:01 ` Ludovic Courtès
2005-11-26 0:49 ` Kevin Ryde
2006-01-09 14:51 ` [PATCH] Marking weak alist vectors, epilogue Ludovic Courtès
2006-01-09 19:29 ` Neil Jerram
2006-01-10 8:21 ` Ludovic Courtès
2006-01-10 9:33 ` Neil Jerram
2006-01-10 15:43 ` Ludovic Courtès
2005-11-17 13:21 ` [PATCH] Fixing `gc-live-object-stats' Ludovic Courtès
2005-11-17 14:12 ` Han-Wen Nienhuys
2005-11-30 8:54 ` Ludovic Courtès
2005-11-30 23:45 ` Han-Wen Nienhuys
2005-12-03 19:31 ` Neil Jerram
2005-12-05 8:50 ` Ludovic Courtès
2005-12-06 19:14 ` Neil Jerram
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