GNU bug report logs - #29040
emacs-26 crash due to misaligned longjmp buffer in 64-bit MSYS2/MinGW-W64 build

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Richard Copley <rcopley <at> gmail.com>
Cc: 29040 <at> debbugs.gnu.org
Subject: bug#29040: Emacs 25 hangs on windows arbitrarily during search of a unicode file
Date: Sat, 28 Oct 2017 17:14:14 +0300

> From: Richard Copley <rcopley <at> gmail.com>
> Date: Sat, 28 Oct 2017 14:56:15 +0100
> Cc: "help-gnu-emacs <at> gnu.org" <help-gnu-emacs <at> gnu.org>, 29040 <at> debbugs.gnu.org
> 
> > So my guess was correct, and we should ask the MinGW64 developers for
> > advice about using longjmp.  Most probably, something in that area has
> > changed in recent releases of their runtime, because otherwise I
> > cannot explain to myself why these issues pop up only now.
> 
> I thought Paul was of a differing opinion (see
> <http://lists.gnu.org/archive/html/emacs-devel/2017-10/msg00482.html>)
> but perhaps I'm mixing up different issues.

I'm not saying that this is a GCC bug.  But maybe you are right, and
the changes in d7038020 exposed this problem.  I would have thought it
was the other way around: the mis-alignment should have been fixed by
those changes, but the fact that the pretest doesn't have this problem
tells otherwise.

> Do I take it we don't get to allocate the jmp_buf ourselves?

It is a member of struct thread_state, and the struct itself should be
correctly aligned on the emacs-26 branch, AFAIU.

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