Re: Calling Lisp from undo.c's record_* functions

[Eli Zaretskii <eliz@gnu.org>]

> From: phillip.lord@russet.org.uk (Phillip Lord)
> Cc: Eli Zaretskii <eliz@gnu.org>,  <emacs-devel@gnu.org>
> Date: Tue, 17 Nov 2015 12:14:27 +0000
> 
> I've pushed an unfinished fix to fix/segfault-from-run-undoable-change

Thanks.

> I'm pretty sure my implementation in C could be simpler. I wasn't sure
> how to get from the current-buffer variable in C, to the Lisp_Object

See XSETBUFFER.

> The second part of the plan is to change simple.el to use a idle timer,
> as I suggested yesterday. I'll do that later today.

What does that timer do?

Would it work to have a non-idle timer that is started once at
startup, and then never shut down, and have its job be put on some
list that the timer will examine?

> At the moment, I can't replicate the problem, though.

The crash happened for me when the build ran this command in
admin/grammars/:

  EMACSLOADPATH= "../../src/emacs.exe" -batch --no-site-file --no-site-lisp -l semantic/wisent/grammar -f wisent-batch-make-parser -o "../../lisp/cedet/semantic/wisent/python-wy.el" python.wy

Try it, maybe it will happen to you as well.  The crash is elusive
(naturally, since it depends on how much consing was done before
that).  It happened to me in a 32-bit build with wide ints, but not
without wide ints.  Also, the build was optimized (-O2), so maybe
that, too, is a prerequisite for reproducing.