bug#34631: 26.1; js-mode freeze

[Antonin Dudermel <antonin.dudermel@ens-lyon.fr>]

Emacs freezes in js-mode on some particular files
To trigger the bug

emacs -Q
C-x C-f bug.js
C-n C-n
TAB

bug.js:

var copy = '\
<a href="https://"></a>'
var x



In GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
of 2018-07-05 built on juergen
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
--localstatedir=/var --with-x-toolkit=gtk3 --with-xft --with-modules
'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong
-fno-plt' CPPFLAGS=-D_FORTIFY_SOURCE=2
LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'

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

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

Major mode: JavaScript

Minor modes in effect:
diff-auto-refine-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
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 dired dired-loaddefs
format-spec rfc822 mml 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 vc-git diff-mode easy-mmode js
advice sgml-mode dom json map seq byte-opt gv bytecomp byte-compile
cconv imenu thingatpt cc-mode cc-fonts easymenu cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs cl-loaddefs cl-lib
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 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 125833 6811)
(symbols 48 23965 1)
(miscs 40 47 115)
(strings 32 39458 1369)
(string-bytes 1 1153331)
(vectors 16 19256)
(vector-slots 8 547674 8424)
(floats 8 53 68)
(intervals 56 232 0)
(buffers 992 12))

-- 
Antonin Dudermel
M1 informatique
ENS Lyon