Subject: Re: bug#49261: 28.0.50; File Locking Breaks Presumptuous Toolchains

From: Lars Ingebrigtsen <[email-masked]>
Date: Sat, 10 Jul 2021 19:15:53 +0200

Eli Zaretskii <[email-masked]> writes:

> It would be good to try to understand byte code of which function is
> being run in frame #3 here:
>
>> Thread 1 "bootstrap-emacs" received signal SIGSEGV, Segmentation fault.
>> 0x00005555556f0549 in AREF (idx=6988131860, array=XIL(0x7ffff1bd901d))
>>     at lisp.h:731
>> 731	  return lisp_h_XLP (o);
>> (gdb) bt
>> #0  0x00005555556f0549 in AREF (idx=6988131860, array=XIL(0x7ffff1bd901d))
>>     at lisp.h:731
>> #1  HASH_KEY (idx=3494065930, h=0x7ffff1bd8f98) at lisp.h:2374
>> #2  hash_lookup
>>     (h=0x7ffff1bd8f98, key=XIL(0x555555c76c64), hash=hash@entry=0x0)
>>     at fns.c:4479

Well, the segfault is in this:

  for (i = HASH_INDEX (h, start_of_bucket); 0 <= i; i = HASH_NEXT (h, i))
    {

and you can see that idx (i.e., i here) is 3494065930, which is a very
unusual value for idx -- it's usually below 2K.  So it can't really be
anything other than a memory corruption issue, I think?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no