bug#27872: 26.0.50; freeze when opening file with emojis

[Nejc Vivod]

Emacs installed via homebrew (--with-cocoa enabled) freezes with 100%
CPU usage when opening a file that contains unicode emojis. Other
editors handle the file just fine (and default mac emacs opens it, but
doesn't display emojis).
Steps to reproduce:
1. emacs -Q
2. open a file that contains a unicode emoji (my test file has a burger icon in 
it - 🍔)
3. emacs will stop responding and keep the CPU at 100%

Is there a way to at least not display emojis (I’m fine with blocks)? Thank you 
in advance

In GNU Emacs 26.0.50 (build 2, x86_64-apple-darwin16.7.0, NS appkit-1504.83 
Version 10.12.6 (Build 16G29))
of 2017-07-30 built on helghan
Repository revision: 2c930d15f541761422a268cd2b5a7f5c11c9a00e
Windowing system distributor 'Apple', version 10.3.1504
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...

Configured using:
'configure --disable-dependency-tracking --disable-silent-rules
--enable-locallisppath=/usr/local/share/emacs/site-lisp
--infodir=/usr/local/Cellar/emacs/HEAD-2c930d1/share/info/emacs
--prefix=/usr/local/Cellar/emacs/HEAD-2c930d1 --without-x --with-xml2
--without-dbus --without-gnutls --without-imagemagick --with-ns
--disable-ns-self-contained'

Configured features:
JPEG NOTIFY ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

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

Major mode: Fundamental

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
  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

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message subr-x 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 time-date tooltip eldoc
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel term/ns-win
ns-win ucs-normalize mule-util term/common-win 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 kqueue cocoa ns multi-tty
make-network-process emacs)

Memory information:
((conses 16 203872 9206)
(symbols 48 19913 2)
(miscs 40 71 157)
(strings 32 29053 1358)
(string-bytes 1 777729)
(vectors 16 34926)
(vector-slots 8 705954 9076)
(floats 8 48 68)
(intervals 56 232 0)
(buffers 992 13))

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