bug#24640: Crashes in 25.1

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 11 Oct 2016 19:33:20 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 24640@debbugs.gnu.org
> 
> > ​Yes, the crashes appear to stop when I comment out (global-undo-tree-mode) in vars.el.
> 
> OK, so we have our prime suspect.  Can you tell where I can find the
> exact version of undo-tree-mode you are using?
> 
> Phillip, could you please look into that package and see if you can
> spot any potential problems with the Emacs 25 undo internals?  TIA.

Some functions in undo-tree refer to or manipulate Emacs undo
internals:

  undo-list-pop-changeset
  undo-list-transfer-to-tree
  undo-list-rebuild-from-tree
  undo-tree-pull-undo-in-region-branch
  undo-tree-pull-redo-in-region-branch
  undo-tree-adjust-elements-to-elt
  undo-tree-apply-deltas
  undo-tree-undo-1
  undo-tree-redo-1

Do they perhaps need some adjustments to Emacs 25's undo?

Another potential issue is the new undo timer we have in Emacs 25 (see
undo-auto--boundary-ensure-timer in simple.el).  One way of checking
whether this is related to the crashes is to modify that function to
use a much larger value for the 1st argument of run-at-time, say
10000, so that the undo timer never fires during the startup.  Reuben,
could you try that?