bug#24640: Crashes in 25.1

[Reuben Thomas]

On 9 October 2016 at 08:05, Eli Zaretskii <eliz@gnu.org> wrote:

> From: Reuben Thomas <rrt@sc3d.org>
> Date: Sat, 8 Oct 2016 23:08:51 +0100
> Cc: 24640@debbugs.gnu.org
>
> ​In frame #0, the code reads:
>
> if (XMISCANY (obj)->gcmarkbit)
> break;
>
> at this point obj is 33, XMISCANY(obj) is 20, and gdb tells me "Cannot access memory at address 0x20".

What do the following commands say in that frame #0:

 (gdb) p obj
 (gdb) xtype

(gdb) p obj
$3 = 33
(gdb) xtype
Lisp_Misc
Cannot access memory at address 0x20​

The only efficient way to speed up debugging (or rather to make sure
it succeeds at all) is for you to come up with a reproducible recipe
and post here all the files needed for reproducing the crashes.

​That would seem to require me to bisect my .desktop and potentially post dozens of personal files, so doesn't seem feasible.​ I thought it might be faster for you to drive a debugging session live than to engage in back-and-forth by email.

>From what I see in the backtraces, your setup fires a timer that runs
some complicated Lisp, and that Lisp somehow corrupts some Lisp
objects, which then cause crashes during GC.

​You make it sound as though this is some arcane personal setup, when in fact I am simply using desktop.el!

And the first step is
to stop using an optimized build, because it makes debugging much
harder if not impossible.

I'll see if, having rebuilt from source without optimisation, the bug still fires.​

If you are willing to try the debugging yourself, there's some advice
in etc/DEBUG (search for "Debugging problems which happen in GC").

​I'll have a look.​

 

Do I understand correctly that this worked for you with Emacs 24.5?

​Yes, the identical setup loads fine in 24.5. I've never seen this sort of crash before.​

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