GNU bug report logs - #77024
31.0.50; feature/igc: crash "switching to thread"

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Oliver Reiter <reiter <at> wiiw.ac.at>
Cc: 77024 <at> debbugs.gnu.org
Subject: bug#77024: 31.0.50; feature/igc: crash "switching to thread"
Date: Wed, 19 Mar 2025 16:14:48 +0200

> From: Oliver Reiter <reiter <at> wiiw.ac.at>
> Cc: 77024 <at> debbugs.gnu.org
> Date: Wed, 19 Mar 2025 09:08:44 +0100
> 
> > Can you show the contents of 'pdl' here?
> 
> I am not that proficient in debugging, do you mean like this?
> 
> >From 'bt full', I figured that 'pdl' is at 0x555556f67ea0:
> 
> #2  0x000055555579fa76 in fix_lisp_obj (ss=ss <at> entry=0x7fffb3bb81a8, pobj=pobj <at> entry=0x555556f67eb0) at /home/reitero/build/sources/emacs/emacs_debug/src/igc.c:1132
>         word = <optimized out>
>         p = 0x555556f67eb0
>         tag = 1
>         client = <optimized out>
>         base = <optimized out>
>         res = <optimized out>
>         _ss = 0x7fffb3bb81a8
>         _mps_zs = <optimized out>
>         _mps_ufs = 0
>         _mps_wt = <optimized out>
>         _mps_w = <optimized out>
> #3  0x00005555557a1040 in scan_specpdl (ss=0x7fffb3bb81a8, start=<optimized out>, end=0x555556f684e0, closure=<optimized out>) at /home/reitero/build/sources/emacs/emacs_debug/src/igc.c:1535
>         res = <optimized out>
>         pdl = 0x555556f67ea0
>         t = <optimized out>
>         _ss = 0x7fffb3bb81a8
>         _mps_zs = <optimized out>
>         _mps_ufs = 0
>         _mps_wt = <optimized out>
>         _mps_w = <optimized out>
> 
> So:
> 
> (gdb) p *(struct Lisp_String *)0x555556f67ea0
> $5 = {
>   gc_header = {
>     v = 1,
>     gcaligned = 1 '\001'
>   },
>   u = {
>     s = {
>       size = 1,
>       size_byte = 4294967297,
>       intervals = 0x1,
>       data = 0x0
>     },
>     next = 0x1,
>     gcaligned = 1 '\001'
>   }
> }
> 
> This should then be pdl->unwind.arg, I guess:
> 
> (gdb) p *(struct Lisp_String *)0x555556f67eb0
> $4 = {
>   gc_header = {
>     v = 4294967297,
>     gcaligned = 1 '\001'
>   },
>   u = {
>     s = {
>       size = 1,
>       size_byte = 0,
>       intervals = 0x0,
>       data = 0x1287 <error: Cannot access memory at address 0x1287>
>     },
>     next = 0x1,
>     gcaligned = 1 '\001'
>   }
> }
> 
> If you meant something else, happy to help.

Just "p *pdl" is what I had in mind.

Thanks.

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