The undo-tree package produces some files that appear to, when read, SIGSEGV
emacs. I've not been able to determine under which circumstances this happens.

You should be able to replicate the issue by reconstructing the original
directory structure, running 'emacs -Q', then loading the '.emacs' file
below and attempting to open the source file at
/home/psilva/src/pedrosilva/xs/src/xs.c (files attached.)

--8<---------------cut here---------------start------------->8---
/home/psilva/src/pedrosilva/xs/src/xs.c
/home/psilva/.emacs.d/undo-tree/.!home!psilva!src!pedrosilva.pt!xs!src!xs.c.~undo-tree~
--8<---------------cut here---------------end--------------->8---

Here's a minimal 'emacs -Q':

--8<---------------cut here---------------start------------->8---
(package-initialize)
(package-install 'undo-tree)
(global-undo-tree-mode)
(setq undo-tree-auto-save-history t
      undo-tree-history-directory-alist
      '(("." . "~/.emacs.d/undo-tree")))
--8<---------------cut here---------------end--------------->8---

Output from the below commands is attached:

--8<---------------cut here---------------start------------->8---
source .gdbinit
set logging on /home/psilva/emacs-undo-tree-segfault/gdb.log
run
backtrace full
xbacktrace
quit
--8<---------------cut here---------------end--------------->8---