Subject: 26.0.50; Bad handling of unmounted directory
From: Philipp <[email-masked]>
To: [email-masked]
Date: Sat, 29 Jul 2017 23:06:32 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

Create a FUSE mount point, e.g.

cd /tmp
mkdir a a/a b
touch a/a/a
bindfs -f a b

While bindfs(1) is running, cd to the mounted directory in a second
shell:

cd /tmp/b/a

Now kill bindfs, e.g. by hitting ^C in the first shell.  The second
shell will now be in an unmounted directory.  From that directory, start
Emacs:

$ emacs -Q -batch a
Apparent cycle of symbolic links for (unreachable)

or, with stack trace

$ emacs -Q -batch -f toggle-debug-on-error a
Debug on Error enabled globally
...
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)/a/(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a/(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)/a/(unreachable)/a/(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a/(unreachable)/a/(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)/a/(unreachable)/a/(unreachable)/a/(unreachable)" (-1) (nil))
  file-truename("(unreachable)/a/(unreachable)/a/(unreachable)/a/(unreachable)/a" (-1) (nil))
  file-truename("(unreachable)/a/(unreachable)/a/(unreachable)/a/(unreachable)/a/a")
  find-file-noselect("(unreachable)/a/(unreachable)/a/a")
  #f(compiled-function (displayable-buffers dir line column name) #<bytecode>)((nil) "(unreachable)/a/" (0) (0) "a")
  command-line-1(("-f" "toggle-debug-on-error" "a"))
  command-line()
  normal-top-level()

It seems like the logic for `default-directory' and/or `file-truename'
should be improved for unmounted filesystems.

In GNU Emacs 26.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.10.8)
 of 2017-07-29 built on unknown
Repository revision: 2c930d15f541761422a268cd2b5a7f5c11c9a00e
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description:	Ubuntu 14.04.5 LTS

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --with-modules --without-pop --with-mailutils
 --enable-checking --enable-check-lisp-object-type --enable-gcc-warnings
 'CFLAGS=-ggdb3 -O0''

Configured features:
XPM JPEG TIFF GIF PNG SOUND GSETTINGS NOTIFY GNUTLS FREETYPE XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 MODULES

Important settings:
  value of $LANG: en_US.UTF-8
  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 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 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 inotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 94115 11926)
 (symbols 48 20077 1)
 (miscs 40 38 119)
 (strings 32 28435 1945)
 (string-bytes 1 754739)
 (vectors 16 13893)
 (vector-slots 8 487465 12899)
 (floats 8 48 97)
 (intervals 56 205 0)
 (buffers 992 11)
 (heap 1024 19129 984))