bug#41321: 27.0.91; Emacs aborts due to invalid pseudovector objects

[Paul Eggert]

On 5/28/20 11:27 AM, Eli Zaretskii wrote:
>> Cc: pipcet@gmail.com, 41321@debbugs.gnu.org, monnier@iro.umontreal.ca
>> From: Paul Eggert <eggert@cs.ucla.edu>
>> Date: Wed, 27 May 2020 09:58:11 -0700
>>
>> we can then talk about what to do with emacs-27.
> 
> After thinking about this some, I think the only sensible thing to do
> on emacs-27 is to return to 8-byte alignment test in GC for 32-bit
> MinGW builds.  That is, replace max_align_t with just 8 in the
> definition of LISP_ALIGNMENT in that case.

Exactly the same problem can occur for other x86 platforms (e.g., GNU/Linux, GCC
7-and-later, glibc 2.25-and-earlier), because these other platforms also have
the bug that malloc can return a pointer that is 8 modulo 16 even though alignof
(max_align_t) is 16.  so I suggest doing the replacement for those platforms
too, as in the attached patch.

0001-Fix-aborts-due-to-GC-losing-pseudovectors.patch
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