GNU bug report logs - #17365
24.3; Visiting tags table in combination with fill column indicator causes Emacs to hang

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jon Dufresne <jon.dufresne <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3;
 Visiting tags table in combination with fill column indicator causes
 Emacs to hang
Date: Mon, 28 Apr 2014 13:55:57 -0700

The following recipe causes Emacs to hang 100%.

0. Start in a mercurial repository directory.
1. Run "emacs -Q -l /path/to/test.el"
2. M-x project-compile-and-visit-tags-table
3. Wait for completion.
4. M-x project-compile-and-visit-tags-table
5. Receive prompt: "Tags file /path/to/TAGS has changed, read new
contents? (yes or no)"
6. Type "yes"
7. Emacs hangs, must send kill signal to close.

The goal of test.el is to re-compile and visit the TAGS file while
coexisting with fci-mode. If there is a better way to accomplish the
same thing, I'd be interested to know.

It is possible that this is a bug in fci-mode, however, it seems to me
that a buggy third party script should not be capable of freezing the
entire Emacs process, so I am filing it here. Removing fci-mode removes
the freezing.

The test.el:

---
(require 'package)
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/"))
(package-initialize)
(package-refresh-contents)
(package-install 'fill-column-indicator)

(require 'fill-column-indicator)
(setq-default fci-rule-column 80)
(defun fci-mode-on ()
  "Turn fci-mode on."
  (fci-mode 1))
(define-globalized-minor-mode global-fci-mode
  fci-mode
  fci-mode-on)
(global-fci-mode 1)

(defun project-compile-and-visit-tags-table ()
  "Compile TAGS file at the project ROOT directory."
  (interactive)
  (let ((root (project-root)))
    (when root
      (add-hook 'compilation-finish-functions #'project-visit-tags-table)
      (compile (format "ctags -e -R --exclude=updates --languages=PHP -o %s %s"
                       (concat root "TAGS") root)))))

(defun project-visit-tags-table (buffer string)
  "Tell tags commands to use tags table at the project root."
  (when (string= string "finished\n")
    (visit-tags-table (concat (project-root) "TAGS")))
  (remove-hook 'compilation-finish-functions #'project-visit-tags-table))

(defun project-root ()
  "Return the project's root directory."
  (locate-dominating-file default-directory ".hg"))
---




In GNU Emacs 24.3.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.10.8)
 of 2014-04-18 on buildvm-19.phx2.fedoraproject.org
Windowing system distributor `Fedora Project', version 11.0.11404000
System Description:	Fedora release 20 (Heisenbug)

Configured using:
 `configure '--build=x86_64-redhat-linux-gnu'
 '--host=x86_64-redhat-linux-gnu' '--program-prefix='
 '--disable-dependency-tracking' '--prefix=/usr' '--exec-prefix=/usr'
 '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc'
 '--datadir=/usr/share' '--includedir=/usr/include'
 '--libdir=/usr/lib64' '--libexecdir=/usr/libexec'
 '--localstatedir=/var' '--sharedstatedir=/var/lib'
 '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--with-dbus'
 '--with-gif' '--with-jpeg' '--with-png' '--with-rsvg' '--with-tiff'
 '--with-xft' '--with-xpm' '--with-x-toolkit=gtk3' '--with-gpm=no'
 'build_alias=x86_64-redhat-linux-gnu'
 'host_alias=x86_64-redhat-linux-gnu' 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g
 -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
 -fstack-protector-strong --param=ssp-buffer-size=4
 -grecord-gcc-switches -m64 -mtune=generic' 'LDFLAGS=-Wl,-z,relro ''

Important settings:
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

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  transient-mark-mode: t

Recent input:
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multi-tty emacs)

Message #8 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Jon Dufresne <jon.dufresne <at> gmail.com>
Cc: 17365 <at> debbugs.gnu.org
Subject: Re: bug#17365: 24.3;
 Visiting tags table in combination with fill column indicator causes
 Emacs to hang
Date: Tue, 29 Apr 2014 10:09:01 -0400

Jon Dufresne wrote:

> It is possible that this is a bug in fci-mode, however, it seems to me
> that a buggy third party script should not be capable of freezing the
> entire Emacs process, so I am filing it here.

As a general comment, an external package can break Emacs in an infinite
number of ways, including making it freeze. That's just how it is.
(I haven't checked your specific issue.)

Message #11 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Jon Dufresne <jon.dufresne <at> gmail.com>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 17365 <at> debbugs.gnu.org
Subject: Re: bug#17365: 24.3; Visiting tags table in combination with fill
 column indicator causes Emacs to hang
Date: Tue, 29 Apr 2014 09:27:44 -0700

On Tue, Apr 29, 2014 at 7:09 AM, Glenn Morris <rgm <at> gnu.org> wrote:
> As a general comment, an external package can break Emacs in an infinite
> number of ways, including making it freeze. That's just how it is.

I see, and understand.

I filed a ticket with the package maintainer as well which contains a
bit more information:
<https://github.com/alpaker/Fill-Column-Indicator/issues/49>

I have since tried this on trunk using the git mirror and the bug
still persists. In the end, if this is a bug in fci-mode and not
strictly Emacs, the package maintainer is very cooperative.

Message #14 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Jon Dufresne <jon.dufresne <at> gmail.com>
Cc: 17365 <at> debbugs.gnu.org
Subject: Re: bug#17365: 24.3;
 Visiting tags table in combination with fill column indicator causes
 Emacs to hang
Date: Tue, 29 Apr 2014 12:29:48 -0400

Jon Dufresne wrote:

> The following recipe causes Emacs to hang 100%.
>
> 0. Start in a mercurial repository directory.
> 1. Run "emacs -Q -l /path/to/test.el"
> 2. M-x project-compile-and-visit-tags-table
> 3. Wait for completion.
> 4. M-x project-compile-and-visit-tags-table
> 5. Receive prompt: "Tags file /path/to/TAGS has changed, read new
> contents? (yes or no)"
> 6. Type "yes"
> 7. Emacs hangs, must send kill signal to close.

I followed the recipe, but it doesn't hang for me.

Message #19 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Jon Dufresne <jon.dufresne <at> gmail.com>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 17365 <at> debbugs.gnu.org
Subject: Re: bug#17365: 24.3; Visiting tags table in combination with fill
 column indicator causes Emacs to hang
Date: Tue, 29 Apr 2014 09:48:15 -0700

On Tue, Apr 29, 2014 at 9:29 AM, Glenn Morris <rgm <at> gnu.org> wrote:
> Jon Dufresne wrote:
>
>> The following recipe causes Emacs to hang 100%.
>>
>> 0. Start in a mercurial repository directory.
>> 1. Run "emacs -Q -l /path/to/test.el"
>> 2. M-x project-compile-and-visit-tags-table
>> 3. Wait for completion.
>> 4. M-x project-compile-and-visit-tags-table
>> 5. Receive prompt: "Tags file /path/to/TAGS has changed, read new
>> contents? (yes or no)"
>> 6. Type "yes"
>> 7. Emacs hangs, must send kill signal to close.
>
> I followed the recipe, but it doesn't hang for me.

Thanks for testing.

I have since done additional testing and the recipe, as stated is
insufficient. There is something specific in my working directory that
is causing this issue, and just any mercurial repository won't do. I
am currently trying to track down precisely what in the directory is
triggering the bug. When I have additional information I will report
it to this ticket. Unfortunately, I am unable to share the repository
required to trigger the issue.

Message #22 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Jon Dufresne <jon.dufresne <at> gmail.com>
Cc: Glenn Morris <rgm <at> gnu.org>, 17365 <at> debbugs.gnu.org
Subject: Re: bug#17365: 24.3;
 Visiting tags table in combination with fill column indicator causes
 Emacs to hang
Date: Tue, 29 Apr 2014 14:10:49 -0400

> I have since done additional testing and the recipe, as stated is
> insufficient. There is something specific in my working directory that
> is causing this issue, and just any mercurial repository won't do. I
> am currently trying to track down precisely what in the directory is
> triggering the bug. When I have additional information I will report
> it to this ticket. Unfortunately, I am unable to share the repository
> required to trigger the issue.

Please (setq debug-on-event 'sigusr2) and then use "kill -USR2 <pid>"
while Emacs is frozen, so as to try and get a backtrace, which will help
us figure out what Emacs is doing while "frozen",


        Stefan

Message #25 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Jon Dufresne <jon.dufresne <at> gmail.com>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: Glenn Morris <rgm <at> gnu.org>, 17365 <at> debbugs.gnu.org
Subject: Re: bug#17365: 24.3; Visiting tags table in combination with fill
 column indicator causes Emacs to hang
Date: Tue, 29 Apr 2014 11:31:32 -0700

On Tue, Apr 29, 2014 at 11:10 AM, Stefan Monnier
<monnier <at> iro.umontreal.ca> wrote:
> Please (setq debug-on-event 'sigusr2) and then use "kill -USR2 <pid>"
> while Emacs is frozen, so as to try and get a backtrace, which will help
> us figure out what Emacs is doing while "frozen",

Debugger entered--Lisp error: (quit)
  fci-put-overlays-region(2807 7574591)
  fci-redraw-region(2807 7574565 0)
  insert-file-contents("/home/jon/devel/erezlife/development/TAGS" t nil nil t)
  revert-buffer-insert-file-contents--default-function("/home/jon/devel/erezlife/development/TAGS"
nil)
  revert-buffer--default(t t)
  revert-buffer(t t)
  tags-verify-table("/home/jon/devel/erezlife/development/TAGS")
  visit-tags-table-buffer("~/devel/erezlife/development/TAGS")
  visit-tags-table("~/devel/erezlife/development/TAGS")
  (progn (visit-tags-table (concat (project-root) "TAGS")))
  (if (string= string "finished\n") (progn (visit-tags-table (concat
(project-root) "TAGS"))))
  project-visit-tags-table(#<buffer *compilation*> "finished\n")
  run-hook-with-args(project-visit-tags-table #<buffer *compilation*>
"finished\n")
  compilation-handle-exit(exit 0 "finished\n")
  compilation-sentinel(#<process compilation> "finished\n")

Message #28 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Alp Aker <alptekin.aker <at> gmail.com>
To: Jon Dufresne <jon.dufresne <at> gmail.com>
Cc: 17365 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#17365: 24.3; Visiting tags table in combination with fill
 column indicator causes Emacs to hang
Date: Tue, 29 Apr 2014 15:10:17 -0400

[Message part 1 (text/plain, inline)]

> Debugger entered--Lisp error: (quit)
>
>      fci-put-overlays-region(2807 7574591)
>      fci-redraw-region(2807 7574565 0)
>      insert-file-contents("/home/jon/devel/erezlife/development/TAGS" t
nil nil t)
>
revert-buffer-insert-file-contents--default-function("/home/jon/devel/erezlife/development/TAGS"
>    nil)
>      revert-buffer--default(t t)
>      revert-buffer(t t)

I'm the author of the package in question.  This is, I think, a use case I
hadn't considered.

Jon, could you replace the definition of fci-redraw-region with the
following and try your recipe again?

(defun fci-redraw-region (start end _ignored)
  (when (fci-get-buffer-windows t)
    (save-match-data
      (save-excursion
        (let ((inhibit-point-motion-hooks t))
          (goto-char end)
          (setq end (line-beginning-position 2))
          (fci-delete-overlays-region start end)
          (fci-put-overlays-region start end))))))

[Message part 2 (text/html, inline)]

Message #31 received at 17365 <at> debbugs.gnu.org (full text, mbox):

From: Jon Dufresne <jon.dufresne <at> gmail.com>
To: Alp Aker <alptekin.aker <at> gmail.com>
Cc: 17365 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#17365: 24.3; Visiting tags table in combination with fill
 column indicator causes Emacs to hang
Date: Tue, 29 Apr 2014 12:16:30 -0700

On Tue, Apr 29, 2014 at 12:10 PM, Alp Aker <alptekin.aker <at> gmail.com> wrote:
> Jon, could you replace the definition of fci-redraw-region with the
> following and try your recipe again?
>
> (defun fci-redraw-region (start end _ignored)
>   (when (fci-get-buffer-windows t)
>     (save-match-data
>       (save-excursion
>         (let ((inhibit-point-motion-hooks t))
>           (goto-char end)
>           (setq end (line-beginning-position 2))
>           (fci-delete-overlays-region start end)
>           (fci-put-overlays-region start end))))))
>
>

This worked! After adding this function Emacs no longer hangs after
entering "yes".

Thank you very much for the prompt response.

The full working recipe now appears as follows:

---
(require 'package)
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/"))
(package-initialize)
(package-refresh-contents)
(package-install 'fill-column-indicator)

(setq debug-on-event 'sigusr2)

(require 'fill-column-indicator)
(setq-default fci-rule-column 80)
(defun fci-mode-on ()
  "Turn fci-mode on."
  (fci-mode 1))
(define-globalized-minor-mode global-fci-mode
  fci-mode
  fci-mode-on)
(global-fci-mode 1)

(defun fci-redraw-region (start end _ignored)
  (when (fci-get-buffer-windows t)
    (save-match-data
      (save-excursion
        (let ((inhibit-point-motion-hooks t))
          (goto-char end)
          (setq end (line-beginning-position 2))
          (fci-delete-overlays-region start end)
          (fci-put-overlays-region start end))))))

(defun project-compile-and-visit-tags-table ()
  "Compile TAGS file at the project ROOT directory."
  (interactive)
  (let ((root (project-root)))
    (when root
      (add-hook 'compilation-finish-functions #'project-visit-tags-table)
      (compile (format "ctags -e -R --languages=PHP -o %s %s"
                       (concat root "TAGS") root)))))

(defun project-visit-tags-table (buffer string)
  "Tell tags commands to use tags table at the project root."
  (when (string= string "finished\n")
    (visit-tags-table (concat (project-root) "TAGS")))
  (remove-hook 'compilation-finish-functions #'project-visit-tags-table))

(defun project-root ()
  "Return the project's root directory."
  (locate-dominating-file default-directory ".hg"))
---

Message #36 received at 17365-done <at> debbugs.gnu.org (full text, mbox):

From: Alp Aker <alptekin.aker <at> gmail.com>
To: Jon Dufresne <jon.dufresne <at> gmail.com>
Cc: Stefan Monnier <monnier <at> iro.umontreal.ca>, 17365-done <at> debbugs.gnu.org
Subject: Re: bug#17365: 24.3; Visiting tags table in combination with fill
 column indicator causes Emacs to hang
Date: Tue, 29 Apr 2014 16:38:08 -0400

[Message part 1 (text/plain, inline)]

> This worked! After adding this function Emacs no longer hangs after
> entering "yes".

Great.  I'll follow up later with a real fix on the package's buglist
(since this isn't an Emacs bug).

Closing this.

[Message part 2 (text/html, inline)]

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