From: Daniel Colascione <dancol@dancol.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: dmantipov@yandex.ru, 17168@debbugs.gnu.org
Subject: bug#17168: 24.3.50; Segfault at mark_object
Date: Sun, 06 Apr 2014 10:11:28 -0700 [thread overview]
Message-ID: <53418AC0.5010300@dancol.org> (raw)
In-Reply-To: <83y4zi75se.fsf@gnu.org>
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On 04/06/2014 09:59 AM, Eli Zaretskii wrote:
>> Date: Sun, 06 Apr 2014 09:37:23 -0700
>> From: Daniel Colascione <dancol@dancol.org>
>> CC: monnier@IRO.UMontreal.CA, dmantipov@yandex.ru, 17168@debbugs.gnu.org
>>
>>> Because Richard has been using that machine for years, and I very much
>>> doubt that he changed his usage patterns lately.
>>
>> Richard's not the only one who has seen this crash. Drew's also reported
>> GC crashes in odd, and different, places.
>
> Which seem unrelated, and started much later than Richard reported
> his.
With a bug like this, unpredictable, usage-pattern-dependent behavior is
expected.
>>>>>>> In http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15583#23, Richard
>>>>>>> provided the last good revno (113938) and the first bad one (114268);
>>>>>>> I looked at that range of revisions, and 114156 looks relevant. How
>>>>>>> about if we revert it and see if the problems go away?
>>>>>>
>>>>>> The bug would still be there, and we'd have no way to tell whether your
>>>>>> proposed change actually reduced its occurrence to a tolerable level.
>>>>>> Why would you want to do that instead of just fixing the bug?
>>>>>
>>>>> Because it's simpler,
>>>>
>>>> It's easy to make code that's simple and wrong.
>>>
>>> I didn't suggest any new code.
>>
>> No: you're just suggesting leaving incorrect code in Emacs.
>
> It's not incorrect, AFAIU. It might be less optimal.
The current code isn't just sub-optimal. It's wrong. If you get unlucky
and try to mark a dead symbol, you will crash.
>>>>> and because it just might be that the bug was
>>>>> caused by that other changeset.
>>>>
>>>> How might that changeset in particular have caused the problem reports?
>>>
>>> It is related to calling a function, and is in the same function from
>>> which all the recent crashes started.
>>
>> You haven't identified a causal mechanism. Any recent change could have
>> caused enough of a shift in code generation or stack layout to cause
>> this problem, and because it manifests so seldom, it'd be hard to verify
>> that reverting any particular change "fixed" the problem.
>
> I thought you had a test case. If not, how did you verify that your
> suggested changes do fix the problem?
There is a test. Your proposed change does not cause the test to pass.
Even if it did, I would argue against substituting a real fix with your
change.
>> Also, eval_sub does *everything*. It's no surprise that we saw the
>> crashes there. That's like saying "all crashes are associated with main,
>> this change affects main, and therefore this change is responsible."
>
> The change is related to calling a function whose symbol has certain
> properties. That sounds related to me, not just a random change
> somewhere in eval_sub.
It's a dangling pointer. Changing slightly the way we chase that
dangling pointer won't change the overall result.
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next prev parent reply other threads:[~2014-04-06 17:11 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-02 7:44 bug#17168: 24.3.50; Segfault at mark_object Nicolas Richard
2014-04-02 15:53 ` Daniel Colascione
2014-04-02 17:59 ` Nicolas Richard
2014-04-02 16:29 ` Dmitry Antipov
2014-04-02 19:46 ` Daniel Colascione
2014-04-02 20:33 ` Daniel Colascione
2014-04-02 20:57 ` Nicolas Richard
2014-04-02 21:50 ` Daniel Colascione
2014-04-02 23:24 ` Stefan Monnier
2014-04-03 0:28 ` Daniel Colascione
2014-04-02 20:37 ` Eli Zaretskii
2014-04-02 20:40 ` Daniel Colascione
2014-04-02 20:55 ` Eli Zaretskii
2014-04-03 6:59 ` Dmitry Antipov
2014-04-03 7:04 ` Dmitry Antipov
2014-04-03 7:55 ` Daniel Colascione
2014-04-03 9:08 ` Daniel Colascione
2014-04-03 14:03 ` Dmitry Antipov
2014-04-03 15:42 ` Stefan Monnier
2014-04-03 16:47 ` Daniel Colascione
2014-04-03 17:49 ` Dmitry Antipov
2014-04-03 17:51 ` Daniel Colascione
2014-04-03 19:21 ` Stefan Monnier
2014-04-03 19:22 ` Daniel Colascione
2014-04-05 22:37 ` Daniel Colascione
2014-04-06 5:05 ` Dmitry Antipov
2014-04-06 5:11 ` Daniel Colascione
2014-04-06 18:00 ` Richard Stallman
2014-04-06 18:10 ` Daniel Colascione
2014-04-06 19:06 ` Eli Zaretskii
2014-04-07 7:49 ` martin rudalics
2014-04-07 8:18 ` Dmitry Antipov
2014-04-07 9:20 ` martin rudalics
2014-04-06 12:36 ` Stefan Monnier
2014-04-06 15:06 ` Eli Zaretskii
2014-04-06 15:59 ` Daniel Colascione
2014-04-06 16:19 ` Eli Zaretskii
2014-04-06 16:24 ` Daniel Colascione
2014-04-06 16:29 ` Eli Zaretskii
2014-04-06 16:37 ` Daniel Colascione
2014-04-06 16:59 ` Eli Zaretskii
2014-04-06 17:11 ` Daniel Colascione [this message]
2014-04-06 19:44 ` Stefan Monnier
2014-04-06 19:42 ` Stefan Monnier
2014-04-06 15:46 ` Daniel Colascione
2014-04-06 19:58 ` Stefan Monnier
2014-04-06 20:13 ` Daniel Colascione
2014-04-06 20:53 ` Daniel Colascione
2014-04-06 21:08 ` Stefan Monnier
2014-04-06 21:37 ` Daniel Colascione
2014-04-07 16:28 ` Stefan Monnier
2014-04-07 19:06 ` Daniel Colascione
2014-04-07 20:42 ` Stefan Monnier
2014-04-08 7:14 ` martin rudalics
2014-04-08 8:47 ` Daniel Colascione
2014-04-06 18:01 ` Richard Stallman
2014-04-06 19:58 ` Stefan Monnier
2014-04-07 16:56 ` Richard Stallman
2014-04-02 20:49 ` Nicolas Richard
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