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From: ludo@gnu.org (Ludovic Courtès)
To: Andy Wingo <wingo@pobox.com>
Cc: guile-user@gnu.org
Subject: Re: smob mark functions in 2.0
Date: Fri, 25 Nov 2011 00:24:11 +0100	[thread overview]
Message-ID: <871usxgl44.fsf@gnu.org> (raw)
In-Reply-To: <8739ddeqlm.fsf@pobox.com> (Andy Wingo's message of "Thu, 24 Nov 2011 11:56:21 +0100")

Hi,

Andy Wingo <wingo@pobox.com> skribis:

> On Thu 24 Nov 2011 00:12, ludo@gnu.org (Ludovic Courtès) writes:
>
>>> So, your mark function might see freed objects.  This is terrible, but
>>> it is the way that it is.  The key is that, if you touch a Scheme object
>>> in your mark function, to first do a check on that object, to see that
>>> it is valid.  You can check the TC bits of the first word, or otherwise
>>> check that other words are non-NULL.
>>
>> What about making that check in libguile before invoking the user’s mark
>> function?
>
> Yes, we do that.  I think you wrote that code!

Yes, when I was young.  ;-)

> The problem was in a mark function, accessing *other* Scheme objects.

Oh, right.

Anyway, users are encouraged to #ifdef out mark functions when using
Guile 2.0.

Thanks,
Ludo’.



  reply	other threads:[~2011-11-24 23:24 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-11-23 21:20 smob mark functions in 2.0 Andy Wingo
2011-11-23 23:12 ` Ludovic Courtès
2011-11-24 10:56   ` Andy Wingo
2011-11-24 23:24     ` Ludovic Courtès [this message]
2011-11-30 15:29 ` Mark H Weaver
2014-09-26  4:50   ` Mark H Weaver
2014-09-27 15:29     ` Andy Wingo

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