I have a rudimentary mud client in elisp I cobbled together and use
(since emacs23 or so): It's been stable since then. However since
upgrading to emacs25 I've seen 4 crashes of emacs itself - 3 yesterday
and 1 today.

At first I thought perhaps it was keyboard/input related as it seemed
to happen while I was typing, but today while running the client
to see if I could track down the problem emacs segfaulted while
I wasn't typing or using the mouse. I managed to get a backtrace
out of gdb, which I have attached. I can semi-reliably reproduce
the crash.

I haven't been able to run xbacktrace as it hasn't yet crashed while
gdb was attached.

Looking at the backtrace and examining the source, it looks like
it blows up in the maybe_gc inside funcall _just before_ the first
hook in window-scroll-functions is called.

In GNU Emacs 25.1.1 (x86_64-pc-linux-gnu, GTK+ Version 3.14.5)
  of 2017-04-27, modified by Debian built on noise
Windowing system distributor 'The X.Org Foundation', version 11.0.11604000
System Description:     Debian GNU/Linux 8.8 (jessie)

Configured using:
  'configure --build x86_64-linux-gnu --prefix=/usr
  --sharedstatedir=/var/lib --libexecdir=/usr/lib
  --localstatedir=/var/lib --infodir=/usr/share/info
  --mandir=/usr/share/man --with-pop=yes

--enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
  --with-sound=alsa --build x86_64-linux-gnu --prefix=/usr
  --sharedstatedir=/var/lib --libexecdir=/usr/lib
  --localstatedir=/var/lib --infodir=/usr/share/info
  --mandir=/usr/share/man --with-pop=yes

--enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
  --with-sound=alsa --with-x=yes --with-x-toolkit=gtk3
  --with-toolkit-scroll-bars 'CFLAGS=-g -O2 -fstack-protector-strong
  -Wformat -Werror=format-security -Wall' CPPFLAGS=-D_FORTIFY_SOURCE=2
  LDFLAGS=-Wl,-z,relro'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
   value of $LC_ALL: en_GB.UTF-8
   value of $LANG: en_GB.UTF-8
   locale-coding-system: utf-8-unix

Major mode: Dired by name

Minor modes in effect:
   which-function-mode: t
   diff-auto-refine-mode: t
   magit-auto-revert-mode: t
   global-git-commit-mode: t
   async-bytecomp-package-mode: t
   shell-dirtrack-mode: t
   auto-image-file-mode: t
   iswitchb-mode: t
   tooltip-mode: t
   global-eldoc-mode: t
   electric-indent-mode: t
   mouse-wheel-mode: t
   tool-bar-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t
   buffer-read-only: t
   column-number-mode: t
   line-number-mode: t

Recent messages:
<elided - this is not the copy that crashed>

Load-path shadows:
/usr/share/emacs/25.1/site-lisp/debian-startup hides /usr/share/emacs/site-lisp/debian-startup
/usr/share/emacs25/site-lisp/cmake-data/cmake-mode hides /usr/share/emacs/site-lisp/cmake-mode
/home/vivek/.emacs.d/lib/htmlfontify hides /usr/share/emacs/25.1/lisp/htmlfontify
/usr/share/emacs25/site-lisp/dictionaries-common/flyspell hides /usr/share/emacs/25.1/lisp/textmodes/flyspell
/usr/share/emacs/site-lisp/rst hides /usr/share/emacs/25.1/lisp/textmodes/rst
/usr/share/emacs25/site-lisp/dictionaries-common/ispell hides /usr/share/emacs/25.1/lisp/textmodes/ispell
/home/vivek/.emacs.d/lib/browse-url hides /usr/share/emacs/25.1/lisp/net/browse-url

Features:
(shadow sort mail-extr emacsbug sendmail make-mode pulse eieio-opt
speedbar sb-image ezimage dframe find-func etags xref project dired-aux
autoconf autoconf-mode git-rebase misearch multi-isearch esh-var esh-io
esh-cmd esh-opt esh-ext esh-proc esh-arg esh-groups eshell esh-module
esh-mode esh-util which-func imenu cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs dabbrev vc-git
sh-script smie executable magit-obsolete magit-blame magit-stash
magit-bisect magit-remote magit-commit magit-sequence magit-notes
magit-worktree magit-branch magit-files magit-refs magit-status magit
magit-repos magit-apply magit-wip magit-log magit-diff smerge-mode
diff-mode magit-core magit-autorevert autorevert filenotify
magit-process magit-margin magit-mode magit-git crm magit-section
magit-popup git-commit magit-utils log-edit message rfc822 mml mml-sec
epg mm-decode mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045
ietf-drums mailabbrev gmm-utils mailheader pcvs-util add-log with-editor
async-bytecomp async tramp-sh tramp tramp-compat tramp-loaddefs trampver
ucs-normalize shell pcomplete comint format-spec server dash dired gnus
gnus-ems nnheader mail-utils wid-edit image-file cus-start cus-load
ls-lisp iswitchb edmacro kmacro thingatpt browse-url cl jka-compr wiki
warnings advice url-auth url url-proxy url-privacy url-expand
url-methods url-history url-cookie url-domsuf url-util url-parse
auth-source cl-seq eieio eieio-core cl-macs gnus-util mm-util help-fns
mail-prsvr password-cache url-vars mailcap ediff-merg ediff-wind
ediff-diff ediff-mult ediff-help ediff-init ediff-util ediff diff wiki-+
ansi-color lui tracking flyspell ispell ring incomplete finder-inf
tex-site info package epg-config seq byte-opt gv bytecomp byte-compile
cl-extra help-mode easymenu cconv cl-loaddefs pcase cl-lib debian-el
debian-el-loaddefs emacs-goodies-el emacs-goodies-custom
emacs-goodies-loaddefs easy-mmode dpkg-dev-el dpkg-dev-el-loaddefs
devhelp time-date mule-util tooltip eldoc electric uniquify ediff-hook
vc-hooks lisp-float-type mwheel x-win term/common-win x-dnd tool-bar dnd
fontset image regexp-opt fringe tabulated-list newcomment elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core frame
cl-generic cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian
slovak czech european ethiopic indian cyrillic chinese charscript
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote dbusbind inotify
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 476270 67640)
  (symbols 48 37722 0)
  (miscs 40 599 1669)
  (strings 32 74597 9971)
  (string-bytes 1 19723175)
  (vectors 16 60643)
  (vector-slots 8 1688085 153273)
  (floats 8 386 972)
  (intervals 56 28462 2534)
  (buffers 976 114)
  (heap 1024 80470 3527))