GNU bug report logs - #47244
28.0.50; SIGSEGV in long-runnning Emacs

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From: Michael Welsh Duggan <mwd <at> cert.org>
To: martin rudalics <rudalics <at> gmx.at>
Cc: Michael Welsh Duggan <mwd <at> md5i.com>, "47244 <at> debbugs.gnu.org" <47244 <at> debbugs.gnu.org>, "schwab <at> linux-m68k.org" <schwab <at> linux-m68k.org>
Subject: bug#47244: 28.0.50; SIGSEGV in long-runnning Emacs
Date: Wed, 07 Apr 2021 13:55:04 -0400

Michael Welsh Duggan <mwd <at> cert.org> writes:

> martin rudalics <rudalics <at> gmx.at> writes:
>
>>  > Don't know where to go from here, but I have a breakpoint set on
>>  >
>>  >        replace_buffer_in_windows_safely_count = 0;
>>  >
>>  > conditioned on count != 0.
>>
>> Good.  IIUC this
>>
>>  > (gdb) p list_length(Vwindow_list)
>>  > $2 = 2
>>
>> and this
>>
>>  > (gdb) xlist
>>  > $13 = 0x1a
>>  > Lisp_Int0
>>  > $14 = 6
>>
>> together indicate that Vwindow_list spontaneously shrinks from 6 to 2
>> elements (which is "impossible" as we know already).  Attaching the next
>> patch which should catch this situation automatically.  It will still be
>> of no help because we won't catch the one that apparently clobbers that
>> list but hopefully more useful than the previous diff.
>
> Triggered.  Here's the backtrace:

[...]

And, to be clear:

(gdb) up
#2  0x000055555564b3ea in window_list () at ../../master/src/window.c:2585
2585        eassert (window_list_length == list_length (Vwindow_list));
(gdb) p window_list_length
$1 = 6
(gdb) p list_length(Vwindow_list)
$2 = 2

-- 
Michael Welsh Duggan
(mwd <at> cert.org)

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