bug#28176: 26.0.50; Emacs hangs on entering a specific article in gnus

[Sam Steingold]

Emacs hangs with a yellow triangle in the middle of the frame
(indicating ding) but C-g and C-] do not interrupt.
CPU usage is at 90%.
The only way out is "force quit" in activity monitor.
"sample" is attached
I seem to be able to reproduce the hang by trying to enter a specific
article in an nntp group.
Thanks.

Sample of Emacs.txt.gz
Description: activity monitor sample

In GNU Emacs 26.0.50 (build 1, x86_64-apple-darwin16.7.0, NS appkit-1504.83 
Version 10.12.6 (Build 16G29))
 of 2017-08-21 built on Clr-Sam.local
Repository revision: 9840499564c90c43b1d269154593ebe57a7cb9b0
Windowing system distributor 'Apple', version 10.3.1504
Recent messages:
Shell native completion is enabled.
Flymake mode disabled in current buffer
Can’t guess python-indent-offset, using defaults: 4
Sent: ## poor man's notebook...
Quit
mouse-2: visit this file in other window [3 times]
View mode: type C-h for help, h for commands, q to quit.
scroll-up-command: End of buffer [7 times]
Mark set
mouse-2: visit this file in other window

Configured using:
 'configure --with-mailutils --with-ns
 
PKG_CONFIG_PATH=/usr/local/opt/libxml2/lib/pkgconfig:/usr/local/opt/imagemagick/lib/pkgconfig/
 --without-makeinfo'

Configured features:
JPEG NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  value of $LANG: C
  locale-coding-system: utf-8-unix

Major mode: Dired by name

Minor modes in effect:
  diff-auto-refine-mode: t
  shell-dirtrack-mode: t
  rcirc-track-minor-mode: t
  pyvenv-mode: t
  global-edit-server-edit-mode: t
  global-semanticdb-minor-mode: t
  global-semantic-idle-scheduler-mode: t
  which-function-mode: t
  url-handler-mode: t
  semantic-mode: t
  show-paren-mode: t
  desktop-save-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-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
  column-number-mode: t
  line-number-mode: t

Load-path shadows:
None found.

Features:
(shadow sort bbdb-message mailalias cookie1 mail-extr gnus-msg gnus-art
mm-uu mml2015 mm-view mml-smime smime dig gnus-sum gnus-group gnus-undo
gnus-start gnus-cloud nnimap nnmail mail-source tls gnutls utf7 netrc
nnoo gnus-spec gnus-int gnus-range gnus-win emacsbug message subr-x
rfc822 mml mml-sec epa epg epg-config mm-decode mm-bodies mm-encode
mail-parse rfc2231 gmm-utils mailheader sendmail add-log view cl-print
remember conf-mode score-mode dired-aux dired dired-loaddefs
semantic/html cursor-sensor mhtml-mode css-mode smie color eww puny
mm-url url-queue url url-proxy url-privacy url-expand url-methods
url-history url-cookie url-domsuf url-util mailcap shr svg xml
browse-url js cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles
cc-align cc-engine cc-vars cc-defs sgml-mode dom flyspell ispell
company-capf company-semantic vc-dir ewoc vc semantic/tag-file
semantic/imenu semantic/sort vc-git semantic/db-file data-debug
cedet-files semantic/wisent/python semantic/decorate/include
semantic/db-find semantic/db-ref semantic/decorate/mode
semantic/decorate pulse semantic/dep semantic/wisent/python-wy
semantic/wisent semantic/wisent/wisent rx company-oddmuse
company-keywords company-etags company-gtags company-dabbrev-code
company-dabbrev company-files company-cmake company-xcode company-clang
company-eclim company-template company-css company-nxml company-bbdb
cl-extra yasnippet flymake flymake-proc flymake-ui company pcase
help-fns radix-tree help-mode elpy find-file-in-project ivy delsel
ivy-overlay ffap thingatpt diff-mode elpy-profile elpy-django easy-mmode
s elpy-refactor derived edmacro kmacro ido grep compile files-x etags
xref project cus-edit python tramp-sh tramp tramp-compat tramp-loaddefs
trampver shell pcomplete parse-time format-spec comint ansi-color
elec-pair rcirc ring vc-dispatcher vc-hg warnings midnight ein-loaddefs
pyvenv json map gnus nnheader gnus-util rmail rmail-loaddefs rfc2047
rfc2045 ietf-drums mail-utils mm-util mail-prsvr wid-edit bbdb-mua
bbdb-com crm mailabbrev bbdb-loaddefs bbdb bbdb-site timezone
edit-server advice server finder-inf info package seq semantic/db-mode
semantic/db eieio-base semantic/idle semantic/format ezimage
semantic/tag-ls semantic/find semantic/ctxt which-func imenu
url-handlers url-parse auth-source cl-seq password-cache url-vars
semantic/util-modes easymenu semantic/util semantic semantic/tag
semantic/lex semantic/fw eieio byte-opt bytecomp byte-compile cconv
eieio-core cl-macs eieio-loaddefs mode-local find-func cedet paren
help-at-pt desktop frameset cus-start cus-load cl gv cl-loaddefs cl-lib
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 634668 35070)
 (symbols 48 45010 1)
 (miscs 40 13275 52)
 (strings 32 220769 13312)
 (string-bytes 1 5560902)
 (vectors 16 90188)
 (vector-slots 8 1891734 7590)
 (floats 8 467 735)
 (intervals 56 6832 0)
 (buffers 992 60))

-- 
Sam Steingold (http://sds.podval.org/) on darwin Ns 10.3.1504
http://steingoldpsychology.com http://www.childpsy.net http://think-israel.org
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My suicidal thoughts are killing me.