From: storm@cua.dk (Kim F. Storm)
Cc: Luc Teirlinck <teirllm@dms.auburn.edu>, rms@gnu.org, emacs-devel@gnu.org
Subject: Re: Fix to long-standing crashes in GC
Date: 20 May 2004 00:04:34 +0200 [thread overview]
Message-ID: <m3u0yc845p.fsf@kfs-l.imdomain.dk> (raw)
In-Reply-To: <jwvfz9wwenj.fsf-monnier+emacs@gnu.org>
Stefan Monnier <monnier@iro.umontreal.ca> writes:
> >> Please try finding out *precisely* which stack slot
> >> mark_memory is currently examining. Which stack frame is it in?
> >> What variable is it?
> >>
>
> > Found another case where a stack pointer points to bogus data,
> > this time in Flet, variable *temps:
>
> What do you mean by "found"? Did you inspect the code looking for
> suspicious things, or did GDB lead you there?
I removed my hack to accept Lisp_Misc_Free objects (to better
understand where the problem originated), and then emacs crashed
there... so GDB lead me there.
>
> > Here we call Feval, which -- at some point in time will trigger GC --
> > and "temps" is filled with random data, some of which are bogus Lisp
> > object pointers.
>
> If gcpros are used, it seems safe: the gcpro2.nvars is initially set to 0 so
> none of the random values in the uninitialized `temps' array are considered
> and then as the array gets filled gcpro2.nvars is incremented accordingly.
> Looks fine.
Yes, that works fine.
>
> If gcpros are not used (i.e. we use conservative stack scanning), it
> shouldn't be a problem either because the conservative scan goes through
> some trouble to ensure that it ignores words pointing to non-GC-managed
> (or non-live) objects.
I have now found two different cases where a pointer on the stack
points to GC-managed memory (mem_find finds it), to a cons cell with a
Lisp_Misc_Free in the car and a bogus list in the cdr. I suspect there
are many more such cases.
I included one such list in my previous mail. So even if we accepted
the Lisp_Misc_Free object (as I said, I reverted that change locally to
understand the problem), following the cdr would lead to a bad Misc
object anyway.
>
> So I think w need to look further.
Looking for what?
More proff that current functionality is broken, or ways to fix it?
--
Kim F. Storm <storm@cua.dk> http://www.cua.dk
next prev parent reply other threads:[~2004-05-19 22:04 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-13 18:19 Fix to long-standing crashes in GC Lars Hansen
2004-05-13 19:09 ` Luc Teirlinck
2004-05-13 19:29 ` Luc Teirlinck
2004-05-13 19:30 ` Lars Hansen
2004-05-13 19:19 ` Stefan Monnier
2004-05-13 22:16 ` Luc Teirlinck
2004-05-13 23:04 ` Stefan Monnier
2004-05-14 11:42 ` Kai Grossjohann
2004-05-14 14:53 ` Luc Teirlinck
2004-05-14 20:48 ` Kai Grossjohann
2004-05-16 9:27 ` Kai Grossjohann
2004-05-14 18:39 ` Luc Teirlinck
2004-05-14 20:54 ` Kim F. Storm
2004-05-14 21:02 ` Richard Stallman
2004-05-22 18:09 ` Lars Hansen
2004-05-23 16:33 ` Eli Zaretskii
2004-05-23 16:32 ` Luc Teirlinck
2004-05-23 17:11 ` Lars Hansen
2004-05-24 5:30 ` Eli Zaretskii
2004-05-25 3:03 ` Luc Teirlinck
2004-05-25 7:07 ` Eli Zaretskii
2004-05-15 4:39 ` Robert Marshall
2004-05-17 14:39 ` Kim F. Storm
2004-05-17 17:42 ` Robert Marshall
2004-05-17 14:43 ` Kim F. Storm
2004-05-18 0:13 ` Luc Teirlinck
2004-05-19 1:26 ` Richard Stallman
2004-05-19 12:11 ` Kim F. Storm
2004-05-19 19:32 ` Stefan Monnier
2004-05-19 22:33 ` Kim F. Storm
2004-05-20 13:17 ` Richard Stallman
2004-05-19 12:52 ` Kim F. Storm
2004-05-19 16:48 ` Stefan Monnier
2004-05-19 22:04 ` Kim F. Storm [this message]
2004-05-19 22:25 ` Stefan Monnier
2004-05-19 22:37 ` Kim F. Storm
2004-05-19 22:50 ` Stefan Monnier
2004-05-20 0:44 ` Kim F. Storm
2004-05-21 23:43 ` Kim F. Storm
2004-05-23 1:14 ` Stefan Monnier
2004-05-23 18:28 ` Richard Stallman
2004-05-24 11:57 ` Kim F. Storm
2004-05-28 21:51 ` Stefan Monnier
2004-05-28 23:40 ` Kim F. Storm
2004-05-28 23:49 ` Stefan Monnier
2004-05-29 23:15 ` Kim F. Storm
2004-05-30 20:44 ` Stefan Monnier
2004-05-31 20:21 ` Kim F. Storm
2004-06-08 20:03 ` Lars Hansen
2004-05-20 7:08 ` Richard Stallman
2004-05-21 22:58 ` Stefan Monnier
-- strict thread matches above, loose matches on Subject: below --
2004-05-13 23:34 Robert Anderson
2004-05-12 13:19 Kim F. Storm
2004-05-13 13:06 ` Kenichi Handa
2004-05-13 15:45 ` Richard Stallman
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