bug#47244: 28.0.50; SIGSEGV in long-runnning Emacs

[Michael Welsh Duggan]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Michael Welsh Duggan <mwd@cert.org>
>> Cc: Michael Welsh Duggan <mwd@md5i.com>,
>>         "schwab@linux-m68k.org"
>>  <schwab@linux-m68k.org>,
>>         "47244@debbugs.gnu.org" <47244@debbugs.gnu.org>
>> Date: Thu, 08 Apr 2021 13:11:34 -0400
>> 
>> I hit the breakpoint in quit.  It looks like Fnconc uses FOR_EACH_TAIL,
>> which uses FOR_EACH_TAIL_INTENAL, which calls maybe_quit.  The question
>> in my mind now is whether block/unblock_input belongs in window_list or
>> in Fnconc.
>
> IMO, the right solution is not block_input but unwind_protect.

Mayhap.  I look forward to a patch to try out.  (I'm not certain how it
should be used, myself.)

FWIW, it might be worth looking through all uses of FOR_EACH_TAIL to
find places that it is used in loops that do destructive updates, like
Fdelete, as it seems icky for C-g to leave one of these operations
partially completed.

-- 
Michael Welsh Duggan
(mwd@cert.org)