Infinite loop with org-inlinetask and org-sticky-header [was Re: ANN: org-sticky-header]

[Adam Porter <adam@alphapapa.net>]

Hi Charles,

Thanks for reporting this.  This is bizarre.  I reproduced it with my
personal config, and with "emacs -q", but it only happens if
org-inlinetask is loaded with "(require 'org-inlinetask)".  This is with
Emacs 25.1 and the Org package distributed with it for "emacs -q", and
with Emacs 25.1 and Org 9.0.5 on my personal config.

I used "pkill -SIGUSR2 emacs" to interrupt the infinite loop and get a
backtrace, but it took many tries of running that command in rapid
succession, because each time, "Entering debugger..." would flash in the
minibuffer for a moment before the process would go back into the
infinite loop.  After enough tries, it would stop the loop and show the
backtrace, but it would go back into the loop as soon as I tried to
switch windows or paste the backtrace into another program.  I had to
kill the process to make it stop.

I'll paste below two backtraces I managed to get, but I'm afraid I don't
know where to go from here.  Since it only happens if org-inlinetask is
loaded, I guess it's not a bug in org-sticky-header per se, but a bug
that org-sticky-header exposes somehow.  Aaron Jensen actually uncovered
a bug in Emacs itself, and in org-sticky-header, a few days ago:

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26586

It was also an infinite loop.  It seems unlikely to me that it's the
same bug, but maybe they are related somehow.  It's all I have to go
on.  If you are interested and adventurous enough, you could try
building Emacs with the fix mentioned on that bug report, and see if you
can still reproduce it.

I can't be sure that it's actually a bug in Emacs, but since the
infinite loop is practically impossible to break out of without killing
the process, and since these backtraces don't mention anything related
to org-anything, it seems like it should be reported as an Emacs bug.

#+BEGIN_EXAMPLE
Debugger entered--entering a function:
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* current-bidi-paragraph-direction()
  line-move-visual(1 nil)
  line-move(1 nil nil 1)
  next-line(1 1)
  funcall-interactively(next-line 1 1)
  call-interactively(next-line nil nil)
  command-execute(next-line)
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* tooltip-hide()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* tooltip-hide()
#+END_EXAMPLE

#+BEGIN_EXAMPLE
Debugger entered--entering a function:
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  read-from-minibuffer("M-x " nil (keymap (10 . minibuffer-complete-and-exit) (13 . minibuffer-complete-and-exit) keymap (menu-bar keymap (minibuf "Minibuf" keymap (tab menu-item "Complete" minibuffer-complete :help "Complete as far as possible") (space menu-item "Complete Word" minibuffer-complete-word :help "Complete at most one word") (63 menu-item "List Completions" minibuffer-completion-help :help "Display all possible completions") "Minibuf")) (27 keymap (118 . switch-to-completions)) (prior . switch-to-completions) (63 . minibuffer-completion-help) (32 . minibuffer-complete-word) (9 . minibuffer-complete) keymap (menu-bar keymap (minibuf "Minibuf" keymap (previous menu-item "Previous History Item" previous-history-element :help "Put previous minibuffer history element in the minibuffer") (next menu-item "Next History Item" next-history-element :help "Put next minibuffer history element in the minibuffer") (isearch-backward menu-item "Isearch History Backward" isearch-backward :help "Incrementally search minibuffer history backward") (isearch-forward menu-item "Isearch History Forward" isearch-forward :help "Incrementally search minibuffer history forward") (return menu-item "Enter" exit-minibuffer :key-sequence "" :help "Terminate input and exit minibuffer") (quit menu-item "Quit" abort-recursive-edit :help "Abort input and exit minibuffer") "Minibuf")) (10 . exit-minibuffer) (13 . exit-minibuffer) (7 . abort-recursive-edit) (C-tab . file-cache-minibuffer-complete) (9 . self-insert-command) (XF86Back . previous-history-element) (up . previous-line-or-history-element) (prior . previous-history-element) (XF86Forward . next-history-element) (down . next-line-or-history-element) (next . next-history-element) (27 keymap (114 . previous-matching-history-element) (115 . next-matching-history-element) (112 . previous-history-element) (110 . next-history-element))) nil extended-command-history nil nil)
  completing-read-default("M-x " #[771 "\211\301>\203.\302\303\304\305\306\a\a\"\307\"\310\311%\202.\312\b.$\207" [obarray (nil t) make-byte-code 257 "\301!\205.\300\302!\232\206.\211\303N?\207" vconcat vector [symbol-name byte-obsolete-info] 4 "\n\n(fn SYM)" complete-with-action] 10 "\n\n(fn STRING PRED ACTION)"] commandp t nil extended-command-history nil nil)
  completing-read("M-x " #[771 "\211\301>\203.\302\303\304\305\306\a\a\"\307\"\310\311%\202.\312\b.$\207" [obarray (nil t) make-byte-code 257 "\301!\205.\300\302!\232\206.\211\303N?\207" vconcat vector [symbol-name byte-obsolete-info] 4 "\n\n(fn SYM)" complete-with-action] 10 "\n\n(fn STRING PRED ACTION)"] commandp t nil extended-command-history)
  read-extended-command()
  byte-code("\302	\303 \bE)\207" [execute-extended-command--last-typed current-prefix-arg nil read-extended-command] 3)
  call-interactively(execute-extended-command nil nil)
  command-execute(execute-extended-command)
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  message("")
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  message("Saved text until \"%s\"" "edit()\n  debug(lambda)\n* tooltip-hide()\n")
  indicate-copied-region()
  kill-ring-save(1401 1 1)
  funcall-interactively(kill-ring-save 1401 1 1)
  call-interactively(kill-ring-save nil nil)
  command-execute(kill-ring-save)
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* current-bidi-paragraph-direction()
  line-move-visual(1 nil)
  line-move(1 nil nil 1)
  next-line(1 1)
  funcall-interactively(next-line 1 1)
  call-interactively(next-line nil nil)
  command-execute(next-line)
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* tooltip-hide()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* eval((if (display-graphic-p) " " "-"))
  redisplay_internal\ \(C\ function\)()
  recursive-edit()
  debug(lambda)
* tooltip-hide()
#+END_EXAMPLE