GNU bug report logs - #6079
24.0.50; set-process-sentinel doesn't work inside sentinels

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 6079 in the body.
You can then email your comments to 6079 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

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

From: Helmut Eller <eller.helmut <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.0.50; set-process-sentinel doesn't work inside sentinels
Date: Sun, 02 May 2010 14:07:52 +0200

set-process-sentinel can't be used inside sentinels because
exec_sentinel_unwind always restores the old value.  This code 

(let* ((proc (start-process "foo" nil "/bin/bash" "-c" "sleep 100"))
       (a-called nil)
       (sentinel-a (lambda (proc msg)
                     (message "a: %s" msg)
                     (setq a-called t)))
       (b-called nil)
       (sentinel-b (lambda (proc msg)
                     (message "b: %s" msg)
                     (set-process-sentinel proc sentinel-a)
                     (setq b-called t))))
  (set-process-sentinel proc sentinel-b)
  (signal-process proc 'SIGSTOP)
  (message "waiting for b")
  (while (not b-called)
    (accept-process-output proc))
  (signal-process proc 'SIGKILL)
  (message "waiting for a")
  (while (not a-called)
    (accept-process-output proc)))

prints:

  waiting for b
  b: stopped (signal)
  waiting for a
  b: killed

which means that sentinel-b was called twice.  Since sentinel-b sets the
the process sentinel to sentinel-a I would expect that sentinel-b can
only be called once.

Message #8 received at 6079 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Helmut Eller <eller.helmut <at> gmail.com>
Cc: 6079 <at> debbugs.gnu.org
Subject: Re: bug#6079: 24.0.50; set-process-sentinel doesn't work inside
 sentinels
Date: Wed, 21 Aug 2019 16:58:21 -0700

Helmut Eller <eller.helmut <at> gmail.com> writes:

> set-process-sentinel can't be used inside sentinels because
> exec_sentinel_unwind always restores the old value.  This code 
>
> (let* ((proc (start-process "foo" nil "/bin/bash" "-c" "sleep 100"))
>        (a-called nil)
>        (sentinel-a (lambda (proc msg)
>                      (message "a: %s" msg)
>                      (setq a-called t)))
>        (b-called nil)
>        (sentinel-b (lambda (proc msg)
>                      (message "b: %s" msg)
>                      (set-process-sentinel proc sentinel-a)
>                      (setq b-called t))))
>   (set-process-sentinel proc sentinel-b)
>   (signal-process proc 'SIGSTOP)
>   (message "waiting for b")
>   (while (not b-called)
>     (accept-process-output proc))
>   (signal-process proc 'SIGKILL)
>   (message "waiting for a")
>   (while (not a-called)
>     (accept-process-output proc)))
>
> prints:
>
>   waiting for b
>   b: stopped (signal)
>   waiting for a
>   b: killed
>
> which means that sentinel-b was called twice.  Since sentinel-b sets the
> the process sentinel to sentinel-a I would expect that sentinel-b can
> only be called once.

(I'm going through old bug reports that have unfortunately gotten no
attention yet.)

I tried reproducing this bug in Emacs 27, but I get:

waiting for b
b: stopped (signal)

waiting for a
a: killed

The exec_sentinel_unwind function no longer exists in Emacs, so the code
in this area has changed in the nine years since you reported this bug.

Do you still see this bug in more modern Emacs versions?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #13 received at 6079 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Helmut Eller <eller.helmut <at> gmail.com>
Cc: 6079 <at> debbugs.gnu.org
Subject: Re: bug#6079: 24.0.50; set-process-sentinel doesn't work inside
 sentinels
Date: Mon, 14 Oct 2019 07:58:02 +0200

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> The exec_sentinel_unwind function no longer exists in Emacs, so the code
> in this area has changed in the nine years since you reported this bug.
>
> Do you still see this bug in more modern Emacs versions?

More information was requested some weeks back, but no response was
given, so I'm closing this bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.