bug#26915: 25.2; Strange malloc Emacs crash

[Live System User]

Hi,

        I experienced a strange Emacs crash that I don't have a
        precise recipe for but I thought I should report it anyway.

        I started Emacs via "emacs -Q" and proceeded to `ediff-buffers`
        two buffers with files I retrieved using `dired`.  Once
        finished, I typed "q" (ediff-quit) to exit ediff.  While still
        in the minibuffer with the prompt:

            Quit this Ediff session? (y or n)

        I tried to type "y" but was unable to -- the cursor was
        hollow (normally it is a solid black box) but Emacs was
        unresponsive even to a few C-g's.

        The Emacs frame then disappeared.

        Looking back at the gnome-terminal where I had invoked
        "emacs -Q" I saw a backtrace which I am including as an
        attachment.

        Thanks.

e-crash.txt
Description: Emacs malloc crash

In GNU Emacs 25.2.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.20.10)
 of 2017-05-02 built on buildvm-17.phx2.fedoraproject.org
Windowing system distributor 'Fedora Project', version 11.0.11803000
Configured using:
 'configure --build=x86_64-redhat-linux-gnu
 --host=x86_64-redhat-linux-gnu --program-prefix=
 --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
 --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
 --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
 --libexecdir=/usr/libexec --localstatedir=/var
 --sharedstatedir=/var/lib --mandir=/usr/share/man
 --infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
 --with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
 --with-gpm=no --with-xwidgets --with-modules
 build_alias=x86_64-redhat-linux-gnu host_alias=x86_64-redhat-linux-gnu
 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g -pipe -Wall -Werror=format-security
 -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong
 --param=ssp-buffer-size=4 -grecord-gcc-switches
 -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic'
 LDFLAGS=-Wl,-z,relro
 PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

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

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Summary

Minor modes in effect:
  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
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
<double-mouse-6> is undefined
<triple-mouse-6> is undefined [2 times]

Load-path shadows:
None found.

Features:
(shadow emacsbug sendmail gnus-dup shr dom subr-x browse-url sort
gnus-cite smiley ansi-color mail-extr gnus-async gnus-bcklg qp gnus-ml
disp-table cursor-sensor nndraft nnmh nndoc mm-archive jka-compr
timezone url-http url-gw url-cache url-auth url-handlers utf-7 rfc2104
nnfolder network-stream nsm starttls gnus-agent gnus-srvr gnus-score
score-mode nnvirtual gnus-msg nntp gnus-cache epa-file epa derived
nnreddit mm-url 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 url-vars json map seq byte-opt bytecomp
byte-compile cl-extra cconv gnus-art mm-uu mml2015 mm-view mml-smime
smime dig mailcap cl gv sieve sieve-mode sieve-manage nnir gnus-sum
gnus-group gnus-undo gnus-start gnus-cloud nnimap nnmail mail-source tls
gnutls utf7 netrc parse-time gnus-spec gnus-int gnus-range message dired
format-spec rfc822 mml mml-sec password-cache epg epg-config mm-decode
mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums
mailabbrev gmm-utils mailheader gnus-win gnus gnus-ems wid-edit nnoo
nnheader gnus-util mm-util help-fns help-mode easymenu cl-loaddefs pcase
cl-lib mail-prsvr mail-utils misearch multi-isearch 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 xwidget-internal move-toolbar
gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 298682 47504)
 (symbols 48 124596 0)
 (miscs 40 294 420)
 (strings 32 105659 6437)
 (string-bytes 1 3734793)
 (vectors 16 26818)
 (vector-slots 8 926259 57443)
 (floats 8 427 755)
 (intervals 56 5141 140)
 (buffers 976 50)
 (heap 1024 100601 21956))