From: Eli Zaretskii <eliz@gnu.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: Conservative GC isn't safe
Date: Sat, 26 Nov 2016 18:42:51 +0200 [thread overview]
Message-ID: <83oa1219bo.fsf@gnu.org> (raw)
In-Reply-To: <jwvbmx2ryxz.fsf-monnier+gmane.emacs.devel@gnu.org> (message from Stefan Monnier on Sat, 26 Nov 2016 11:29:06 -0500)
> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Sat, 26 Nov 2016 11:29:06 -0500
>
> > Documentation aspects aside, if by "manipulate struct interval" you
> > mean what we do in intervals.c between the call to make_interval and
> > the return value being plugged into some Lisp object, either a buffer
>
> Yes, basically, that kind of manipulation.
All of these cases are in intervals.c. There are no other calls to
make_interval anywhere in our sources.
So the question is: are those _the_only_ cases that you are talking
about, or do you see any others?
> > or a string, then we could set a variable during that time, which
> > would cause an abort in GC, if that happens somehow.
>
> Such a var would only catch some of the possible issues I think
> (there's also the issue of when we take an existing struct interval
> pointer, remove it from one lvalue and plug it into another, plus
> various other cases).
>
> IOW it sounds difficult to make such a test be "complete" (catch
> most/all cases).
That doesn't mean we shouldn't do what we can. Provided that we
consider this danger to be real, of course.
> I also think it could prove fiddly to avoid false positives.
How can this cause false positives? The current code doesn't allow
any GC in those functions I described above. This is purely a
defensive technique against possible changes in the future which will
mistakenly allow that.
next prev parent reply other threads:[~2016-11-26 16:42 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-26 8:11 Conservative GC isn't safe Daniel Colascione
2016-11-26 8:30 ` Paul Eggert
2016-11-26 8:33 ` Daniel Colascione
2016-11-26 9:01 ` Eli Zaretskii
2016-11-26 9:04 ` Daniel Colascione
2016-11-26 9:24 ` Eli Zaretskii
2016-11-26 15:05 ` Stefan Monnier
2016-11-26 15:21 ` Camm Maguire
2016-11-28 17:51 ` Daniel Colascione
2016-11-28 18:00 ` Eli Zaretskii
2016-11-28 18:03 ` Daniel Colascione
2016-11-28 18:50 ` Eli Zaretskii
2016-11-28 18:03 ` Stefan Monnier
2016-11-28 19:18 ` Daniel Colascione
2016-11-28 19:33 ` Stefan Monnier
2016-11-28 19:37 ` Eli Zaretskii
2016-11-28 19:40 ` Daniel Colascione
2016-11-28 20:03 ` Eli Zaretskii
2016-11-28 20:09 ` Daniel Colascione
2016-11-28 19:26 ` Andreas Schwab
2016-11-28 19:34 ` Stefan Monnier
2016-11-26 15:03 ` Stefan Monnier
2016-11-26 15:12 ` Eli Zaretskii
2016-11-26 16:29 ` Stefan Monnier
2016-11-26 16:42 ` Eli Zaretskii [this message]
2016-11-26 18:43 ` Stefan Monnier
2016-11-27 6:17 ` Ken Raeburn
2016-11-27 15:39 ` Eli Zaretskii
2016-11-28 9:50 ` Ken Raeburn
2016-11-28 15:55 ` Eli Zaretskii
2016-11-27 16:15 ` Paul Eggert
2016-11-28 9:36 ` Ken Raeburn
2016-11-28 15:55 ` Eli Zaretskii
2016-11-28 16:15 ` Stefan Monnier
2016-11-28 17:37 ` Eli Zaretskii
2016-11-28 17:49 ` Stefan Monnier
2016-11-28 17:57 ` Eli Zaretskii
2016-11-28 18:05 ` Stefan Monnier
2016-11-28 19:09 ` Ken Raeburn
2016-11-28 19:33 ` Eli Zaretskii
2016-11-29 8:49 ` Ken Raeburn
2016-11-28 17:03 ` Björn Lindqvist
2016-11-28 16:13 ` Paul Eggert
2016-11-27 16:52 ` Stefan Monnier
2016-11-26 19:08 ` Pip Cet
2016-11-27 0:24 ` Paul Eggert
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