bug#69358: 30.0.50; Segmentation fault: compare_overlays (v1=v1@entry=0x0, v2=v2@entry=0x7fffffffd510)

[Eli Zaretskii]

> From: Bruno Barbier <perso.bruno.barbier@free.fr>
> Date: Sat, 24 Feb 2024 12:07:31 +0100
> 
> 
> Running emacs from the current master, I'm getting the following
> segfault:
> 
>      Program received signal SIGSEGV, Segmentation fault.
>      0x00005555556e7c14 in compare_overlays (v1=v1@entry=0x0, 
>          v2=v2@entry=0x7fffffffd510) at buffer.c:3188
>      3188       if (s1->priority != s2->priority)
> 
> I didn't try to reproduce with "-Q" as it might be tricky to reproduce
> (Emacs is stable, works for hours, only one specific workflow is
> triggering the crash).
> 
> Find below the output of 'bt full' and 'xbacktrace' and other bug report
> infos.
> 
> Let me know if you need me to collect more information to help you solve
> this bug.
> 
> Thanks,
> 
> Bruno
> 
> 
> 
> ┌────
> │ bt full
> │ #0  0x00005555556e7c14 in compare_overlays (v1=v1@entry=0x0, 
> │     v2=v2@entry=0x7fffffffd510) at buffer.c:3188
> │         s1 = 0x0
> │         s2 = 0x7fffffffd510
> │ #1  0x000055555574159e in Fget_pos_property (position=position@entry=0x3d2, 
> │     prop=prop@entry=0xa3b0, object=object@entry=0x555559c2a1dd)
> │     at editfns.c:328
> │         ol = <optimized out>
> │         this = 0x7fffffffd510
> │         itree_local_iter_ = {
> │           node = 0x555558172440,
> │           begin = 243,
> │           end = 245,
> │           otick = 1,
> │           order = ITREE_ASCENDING
> │         }
> │         itree_iter_ = 0x7fffffffd4e0
> │         posn = 244
> │         obuf = 0x555559c2a1d8
> │         node = 0x55555a63ce40
> │         tem = 0x55555a9b61c3
> │         items = {{
> │             overlay = 0x55555a5f312d,
> │             beg = 217,
> │             end = 244,
> │             priority = 12,
> │             spriority = 0
> │           }, {
> │             overlay = 0x4000000006000000,
> │             beg = 4611686019484352512,
> │             end = 3,
> │             priority = 93825078009008,
> │             spriority = 93824994725839
> │           }}
> │         result = 0x0
> │         b = 0x555559c2a1d8
> │         res = 0x55555a9c1623

Adding Stefan, who made the changes there last.

Stefan, there's some kind of thinko in the code: result seems to stay
at its initial NULL value.  Or did I miss something?