Visting the file trigger_bug_in_emacs.txt attached below causes emacs to
segfault.  The short version info: Debian/GNU Linux x86_64, unstable,
which provides Debian's Emacs package version 26.3+1-1.

The recipe is:

  emacs -Q trigger_bug_in_emacs.txt

To get debugging output, I ran it under gdb using the .gdbinit from the
Emacs git repo and logged the output of 'bt full' and 'xbacktrace'.
Their outputs are in the attached gdb.txt.  Warning: Visiting the
gdb.txt file will also crash emacs!

If you need more debugging info (e.g. lisp objects), let me know.  I
didn't have any luck using "pr" within gdb, but maybe I didn't "pr" the
right objects.  I have a make script that generates the debugging
output, so it's easy for me to modify it to get more info or to retest
with a simpler or with different input files.

Also, if this bug is a Debian issue only, please accept my apologies and
let me know so that I know to file a Debian bug.

The debugging symbols come from the Debian emacs-gtk-dbgsym package.

My locale is utf8:

  $ locale
  LANG=en_US.utf8
  LANGUAGE=
  LC_CTYPE=en_US.utf8
  LC_NUMERIC="en_US.utf8"
  LC_TIME="en_US.utf8"
  LC_COLLATE="en_US.utf8"
  LC_MONETARY="en_US.utf8"
  LC_MESSAGES="en_US.utf8"
  LC_PAPER="en_US.utf8"
  LC_NAME="en_US.utf8"
  LC_ADDRESS="en_US.utf8"
  LC_TELEPHONE="en_US.utf8"
  LC_MEASUREMENT="en_US.utf8"
  LC_IDENTIFICATION="en_US.utf8"
  LC_ALL=

Finally, here is the system/emacs version info (which I generated and
copied from within an "emacs -Q" instance):

In GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.11)
 of 2019-09-22, modified by Debian built on x86-csail-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description:	Debian GNU/Linux bullseye/sid

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 --enable-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --build
 x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --enable-libsystemd
 --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/26.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/26.3/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils --with-x=yes
 --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -fdebug-prefix-map=/build/emacs-n8pPyG/emacs-26.3+1=. -fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS GLIB
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS LIBSYSTEMD LCMS2

Important settings:
  value of $LC_CTYPE: en_US.utf8
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  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
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils elec-pair time-date
mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors 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 composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray 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 threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 95690 6669)
 (symbols 48 20473 1)
 (miscs 40 49 144)
 (strings 32 29147 1264)
 (string-bytes 1 763066)
 (vectors 16 13944)
 (vector-slots 8 503330 7410)
 (floats 8 49 68)
 (intervals 56 269 0)
 (buffers 992 12))

-- 
-Sanjoy

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Save Long Wharf Park in Boston Harbor!

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