Re: [O] Possible bug: Emacs hangs on (require 'org)

[Luke]

On 23/11/16 10:39, Eric Abrahamsen wrote:
> Luke <address@hidden> writes:
>
> > I have a strange situation on my laptop.
> >
> > I'm running Ubuntu 16.04, with Emacs 24.5.1. I'm also using the latest
> > development branch from the org-mode git repository (latest changes
> > pulled today).
> >
> > Recently, for some unknown reason, emacs suddenly started to hang on
> > startup. Placing some output messages in my .emacs file I was able to
> > narrow it down to this line:
> >
> >     (require 'org)
> >
> > Loading org-mode hangs Emacs for some reason. If I remove the above
> > line from .emacs then Emacs will start as normal (although without
> > org-mode, obviously).
> >
> > I tried creating a minimal-org.el file with the following contents:
> >
> >     ;; activate debugging
> >     (setq debug-on-error t
> >           debug-on-signal nil
> >           debug-on-quit nil)
> >
> >     ;; add latest org-mode to load path
> >     (add-to-list 'load-path (expand-file-name "~/elisp/org-mode/lisp"))
> >     (add-to-list 'load-path (expand-file-name
> > "~/elisp/org-mode/contrib/lisp" t))
> >
> > And then running:
> >
> >     $ emacs -Q -l minimal-org.el
> >
> > ...but I still get the same result (Emacs hangs when I run `M-x
> > (require 'org)`).
> >
> > Can anyone help tell me what's wrong, or suggest how I try and track
> > down the problem?
>
> You're setting debug-on-quit to nil, but it's likely that setting it to
> t is exactly what you need. Toggle it to t, eval (require 'org), then
> while it's hung hit C-g. You should get a backtrace showing you what
> Emacs was actually doing when you quit.
>
> Eric

Thanks to Eric for the debugging tip. Below is the backtrace that was 
produced. It looks like tramp is trying to make some connection to the 
host-name "host.does.not.exist" (which will obviously fail).

This makes sense, because when I disable networking then Emacs starts 
immediately and doesn't hang. I'm not sure how to fix this though.

=====================================================================
Debugger entered--Lisp error: (quit)
  call-process("ssh" nil t nil "-o" "ControlPath=%C" "host.does.not.exist")
  (progn (call-process "ssh" nil t nil "-o" "ControlPath=%C" 
"host.does.not.exist") (goto-char (point-min)) (if 
(search-forward-regexp "unknown.+key" nil t) (setq result (concat result 
" -o ControlPath='address@hidden:%%p'")) (setq result (concat result " -o 
ControlPath='tramp.%%C'"))))
  (unwind-protect (progn (call-process "ssh" nil t nil "-o" 
"ControlPath=%C" "host.does.not.exist") (goto-char (point-min)) (if 
(search-forward-regexp "unknown.+key" nil t) (setq result (concat result 
" -o ControlPath='address@hidden:%%p'")) (setq result (concat result " -o 
ControlPath='tramp.%%C'")))) (and (buffer-name temp-buffer) (kill-buffer 
temp-buffer)))
  (save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(call-process "ssh" nil t nil "-o" "ControlPath=%C" 
"host.does.not.exist") (goto-char (point-min)) (if 
(search-forward-regexp "unknown.+key" nil t) (setq result (concat result 
" -o ControlPath='address@hidden:%%p'")) (setq result (concat result " -o 
ControlPath='tramp.%%C'")))) (and (buffer-name temp-buffer) (kill-buffer 
temp-buffer))))
  (let ((temp-buffer (generate-new-buffer " *temp*"))) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(call-process "ssh" nil t nil "-o" "ControlPath=%C" 
"host.does.not.exist") (goto-char (point-min)) (if 
(search-forward-regexp "unknown.+key" nil t) (setq result (concat result 
" -o ControlPath='address@hidden:%%p'")) (setq result (concat result " -o 
ControlPath='tramp.%%C'")))) (and (buffer-name temp-buffer) (kill-buffer 
temp-buffer)))))
  (if (zerop (length result)) nil (let ((temp-buffer 
(generate-new-buffer " *temp*"))) (save-current-buffer (set-buffer 
temp-buffer) (unwind-protect (progn (call-process "ssh" nil t nil "-o" 
"ControlPath=%C" "host.does.not.exist") (goto-char (point-min)) (if 
(search-forward-regexp "unknown.+key" nil t) (setq result (concat result 
" -o ControlPath='address@hidden:%%p'")) (setq result (concat result " -o 
ControlPath='tramp.%%C'")))) (and (buffer-name temp-buffer) (kill-buffer 
temp-buffer))))) (let ((temp-buffer (generate-new-buffer " *temp*"))) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(call-process "ssh" nil t nil "-o" "ControlPersist") (goto-char 
(point-min)) (if (search-forward-regexp "missing.+argument" nil t) 
(progn (setq result ...)))) (and (buffer-name temp-buffer) (kill-buffer 
temp-buffer))))))
  (progn (let ((temp-buffer (generate-new-buffer " *temp*"))) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(call-process "ssh" nil t nil "-o" "ControlMaster") (goto-char 
(point-min)) (if (search-forward-regexp "missing.+argument" nil t) 
(progn (setq result "-o ControlMaster=auto")))) (and (buffer-name 
temp-buffer) (kill-buffer temp-buffer))))) (if (zerop (length result)) 
nil (let ((temp-buffer (generate-new-buffer " *temp*"))) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(call-process "ssh" nil t nil "-o" "ControlPath=%C" 
"host.does.not.exist") (goto-char (point-min)) (if 
(search-forward-regexp "unknown.+key" nil t) (setq result ...) (setq 
result ...))) (and (buffer-name temp-buffer) (kill-buffer 
temp-buffer))))) (let ((temp-buffer (generate-new-buffer " *temp*"))) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(call-process "ssh" nil t nil "-o" "ControlPersist") (goto-char 
(point-min)) (if (search-forward-regexp "missing.+argument" nil t) 
(progn ...))) (and (buffer-name temp-buffer) (kill-buffer temp-buffer)))))))
  (if (executable-find "ssh") (progn (let ((temp-buffer 
(generate-new-buffer " *temp*"))) (save-current-buffer (set-buffer 
temp-buffer) (unwind-protect (progn (call-process "ssh" nil t nil "-o" 
"ControlMaster") (goto-char (point-min)) (if (search-forward-regexp 
"missing.+argument" nil t) (progn ...))) (and (buffer-name temp-buffer) 
(kill-buffer temp-buffer))))) (if (zerop (length result)) nil (let 
((temp-buffer (generate-new-buffer " *temp*"))) (save-current-buffer 
(set-buffer temp-buffer) (unwind-protect (progn (call-process "ssh" nil 
t nil "-o" "ControlPath=%C" "host.does.not.exist") (goto-char ...) (if 
... ... ...)) (and (buffer-name temp-buffer) (kill-buffer 
temp-buffer))))) (let ((temp-buffer (generate-new-buffer " *temp*"))) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn 
(call-process "ssh" nil t nil "-o" "ControlPersist") (goto-char ...) (if 
... ...)) (and (buffer-name temp-buffer) (kill-buffer temp-buffer))))))))
  (progn (if (executable-find "ssh") (progn (let ((temp-buffer 
(generate-new-buffer " *temp*"))) (save-current-buffer (set-buffer 
temp-buffer) (unwind-protect (progn (call-process "ssh" nil t nil "-o" 
"ControlMaster") (goto-char ...) (if ... ...)) (and (buffer-name 
temp-buffer) (kill-buffer temp-buffer))))) (if (zerop (length result)) 
nil (let ((temp-buffer (generate-new-buffer " *temp*"))) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect (progn ... 
... ...) (and ... ...)))) (let ((temp-buffer (generate-new-buffer " 
*temp*"))) (save-current-buffer (set-buffer temp-buffer) (unwind-protect 
(progn ... ... ...) (and ... ...))))))))
  (condition-case nil (progn (if (executable-find "ssh") (progn (let 
((temp-buffer (generate-new-buffer " *temp*"))) (save-current-buffer 
(set-buffer temp-buffer) (unwind-protect (progn ... ... ...) (and ... 
...)))) (if (zerop (length result)) nil (let ((temp-buffer ...)) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect ... ...))) 
(let ((temp-buffer ...)) (save-current-buffer (set-buffer temp-buffer) 
(unwind-protect ... ...))))))) (error nil))
  (let ((result "") (case-fold-search t)) (condition-case nil (progn 
(if (executable-find "ssh") (progn (let ((temp-buffer ...)) 
(save-current-buffer (set-buffer temp-buffer) (unwind-protect ... ...))) 
(if (zerop (length result)) nil (let (...) (save-current-buffer ... 
...)) (let (...) (save-current-buffer ... ...)))))) (error nil)) result)
  (defvar tramp-ssh-controlmaster-options (let ((result "") 
(case-fold-search t)) (condition-case nil (progn (if (executable-find 
"ssh") (progn (let (...) (save-current-buffer ... ...)) (if (zerop ...) 
nil (let ... ...) (let ... ...))))) (error nil)) result) "Call ssh to 
detect whether it supports the Control* arguments.\nReturn a string to 
be used in `tramp-methods'.")
  eval-buffer(#<buffer  *load*> nil 
"/usr/share/emacs/24.5/lisp/net/tramp-loaddefs.el" nil t)  ; Reading at 
buffer position 7072

load-with-code-conversion("/usr/share/emacs/24.5/lisp/net/tramp-loaddefs.el" 
"/usr/share/emacs/24.5/lisp/net/tramp-loaddefs.el" nil t)
  require(tramp-loaddefs)
  byte-code("\300\301!\207" [require tramp-loaddefs] 2)

byte-code("\300\301\302\303#\210\300\304\305\306#\210\300\304\307\306#\210\300\304\310\306#\210\300\304\311\306#\210\300\304\312\306#\210\300\304\313\306#\210\300\314\315\316#\210\300\317\320\316#\210\300\304\321\306#\210\300\322\323\306#\210\300\324\325\306#\210\300\322\326\306#\210\300\327\330\316#\210\300\331\332\303#\210\300\331\333\303#\210\300\331\334\303#\210\300\331\335\303#\210\300\331\336\303#\210\300\337\340\341#\210\342\343!\203\206
=====================================================================