bug#47393: 27.2; hfy-invisible, hfy-face-to-style-i infinite loop due to circular list

bug#47393: 27.2; hfy-invisible, hfy-face-to-style-i infinite loop due to circular list

[Rajeev Narang via Bug reports for GNU Emacs, the Swiss army knife of text editors]

hfy-face-to-style-i goes into an infinite loop due to circular list when there is invisible text in the buffer.

This happens because of using ncons with static list returned from hfy-invisible. see bug#47391: 27.2; static list return from function and nconc


In GNU Emacs 27.2 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.24)
 of 2021-03-19 built on hp
Repository revision: deef5efafb70f4b171265b896505b92b6eef24e6
Repository branch: emacs-27
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Debian GNU/Linux bullseye/sid

Recent messages:
Hiding all blocks...done
nnimap read 0k from imap.sivalik.com
No more unseen articles
No more unread articles
Mark set [2 times]
Exiting summary buffer and applying spam rules
Expiring articles...done
Saving /home/rajeev/.newsrc.eld...
Wrote /home/rajeev/.newsrc.eld
Saving /home/rajeev/.newsrc.eld...done

Configured using:
 'configure --prefix=/home/rajeev/tmp/build/emacs'

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

Important settings:
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  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
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Major mode: Group

Minor modes in effect:
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  gnus-undo-mode: t
  tooltip-mode: t
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  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
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  auto-encryption-mode: t
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  buffer-read-only: t
  transient-mark-mode: t

Load-path shadows:
/home/rajeev/.config/emacs/elpa/map-3.0/map hides /home/rajeev/tmp/build/emacs/share/emacs/27.2/lisp/emacs-lisp/map

Features:
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dynamic-setting system-font-setting font-render-setting move-toolbar
gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 703957 106325)
 (symbols 48 40836 55)
 (strings 32 178512 19113)
 (string-bytes 1 5891050)
 (vectors 16 78748)
 (vector-slots 8 1541608 175354)
 (floats 8 1257 2058)
 (intervals 56 42345 615)
 (buffers 1000 122))