GNU bug report logs - #7946
Referring to a marker changes Emacs' behaviour.

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

From: Le Wang <l26wang <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Referring to a marker changes Emacs' behaviour.
Date: Mon, 31 Jan 2011 14:45:43 +0800

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

Hi,

I found an issue where evaluating this line or not causes Emacs behaviour
change:

(format "%s" marked-point)


"marked-point" is a marker.  The bug was found on NTEmacs 23.2.1, reproed on
CVS NTEmacs 20110111, and Stephen Berman confirmed it on GNU Emacs 24.0.50.1
(i686-pc-linux-gnu, GTK+ Version 2.20.1) of 2011-01-13 on escher

"rebox2_bug.el" is attached to this message.

Repro-steps:

   1. emacs -Q rebox2_bug.el
   2. M-x eval-current-buffer
   3. C-x b<enter> ;; switch to "*scratch*"
   4. M-x rebox-mode
   5. M-<
   6. SPC,SPC ;; space twice
   7. C-aC-aC-aC-a ;; notice that the point is stuck at 6
   8. C-xb<enter> ;; switch to "rebox2_bug.el
   9. M-g g 1714
   10. C-d ;; uncomment the hack workaround the bug
   11. C-M-x ;; reevaluated the function
   12. C-x b<enter> ;; switch to "*scratch*"
   13. C-aC-aC-aC-a ;; notice that the cursor switches between 1 and 6



-- 
Le

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

[rebox2_bug.el (application/octet-stream, attachment)]

Message #8 received at 7946 <at> debbugs.gnu.org (full text, mbox):

From: Deniz Dogan <deniz.a.m.dogan <at> gmail.com>
To: Le Wang <l26wang <at> gmail.com>
Cc: 7946 <at> debbugs.gnu.org
Subject: Re: bug#7946: Referring to a marker changes Emacs' behaviour.
Date: Wed, 2 Feb 2011 05:44:40 +0100

2011/1/31 Le Wang <l26wang <at> gmail.com>:
> Hi,
> I found an issue where evaluating this line or not causes Emacs behaviour
> change:
>
> (format "%s" marked-point)
>
> "marked-point" is a marker.  The bug was found on NTEmacs 23.2.1, reproed on
> CVS NTEmacs 20110111, and Stephen Berman confirmed it on GNU Emacs 24.0.50.1
> (i686-pc-linux-gnu, GTK+ Version 2.20.1) of 2011-01-13 on escher
> "rebox2_bug.el" is attached to this message.
> Repro-steps:
>
> emacs -Q rebox2_bug.el
> M-x eval-current-buffer
> C-x b<enter> ;; switch to "*scratch*"
> M-x rebox-mode
> M-<
> SPC,SPC ;; space twice
> C-aC-aC-aC-a ;; notice that the point is stuck at 6
> C-xb<enter> ;; switch to "rebox2_bug.el
> M-g g 1714
> C-d ;; uncomment the hack workaround the bug
> C-M-x ;; reevaluated the function
> C-x b<enter> ;; switch to "*scratch*"
> C-aC-aC-aC-a ;; notice that the cursor switches between 1 and 6
>
> --
> Le
>

I was unable to reproduce this. At both of the "C-a C-a C-a" steps, it
switches between 1 and 4 (or 0 and 3 rather).

-- 
Deniz Dogan

Message #11 received at 7946 <at> debbugs.gnu.org (full text, mbox):

From: Deniz Dogan <deniz.a.m.dogan <at> gmail.com>
To: Le Wang <l26wang <at> gmail.com>
Cc: 7946 <at> debbugs.gnu.org
Subject: Re: bug#7946: Referring to a marker changes Emacs' behaviour.
Date: Wed, 2 Feb 2011 06:08:50 +0100

2011/2/2 Le Wang <l26wang <at> gmail.com>:
> Thanks for trying, it should switch between columns 1 and 6 (I should have
> been more specific).  the "space twice" step should move the whole comment
> section over by 2 spaces, did this work for you?

Sorry, I read it as C-SPC twice, so I did it wrong.

I can reproduce the behavior that you described.

-- 
Deniz Dogan

Message #14 received at 7946 <at> debbugs.gnu.org (full text, mbox):

From: Le Wang <l26wang <at> gmail.com>
To: 7946 <at> debbugs.gnu.org
Subject: Fwd: bug#7946: Referring to a marker changes Emacs' behaviour.
Date: Wed, 2 Feb 2011 16:46:24 +0800

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

---------- Forwarded message ----------
From: Deniz Dogan <deniz.a.m.dogan <at> gmail.com>
Date: Wed, Feb 2, 2011 at 1:08 PM
Subject: Re: bug#7946: Referring to a marker changes Emacs' behaviour.
To: Le Wang <l26wang <at> gmail.com>
Cc: 7946 <at> debbugs.gnu.org


2011/2/2 Le Wang <l26wang <at> gmail.com>:
> Thanks for trying, it should switch between columns 1 and 6 (I should have
> been more specific).  the "space twice" step should move the whole comment
> section over by 2 spaces, did this work for you?

Sorry, I read it as C-SPC twice, so I did it wrong.

I can reproduce the behavior that you described.

--
Deniz Dogan



-- 
Le

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

Message #19 received at 7946-done <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Le Wang <l26wang <at> gmail.com>
Cc: 7946-done <at> debbugs.gnu.org
Subject: Re: bug#7946: Referring to a marker changes Emacs' behaviour.
Date: Wed, 02 Feb 2011 10:54:56 -0500

> I found an issue where evaluating this line or not causes Emacs behaviour
> change:

> (format "%s" marked-point)

The patch below appears to fix the problem for me.  I've installed it in
the emacs-23 branch.

The problem was that current-column uses a cache to try and speed up
some cases, and the cache was not flushed when exiting
a save-restriction.  The workaround you used works because `set-buffer'
flushes the cache and `format' uses set-buffer internally.


        Stefan


=== modified file 'src/editfns.c'
--- src/editfns.c	2011-01-02 23:50:46 +0000
+++ src/editfns.c	2011-02-02 15:45:27 +0000
@@ -3347,6 +3347,9 @@
 	}
     }
 
+  /* Changing the buffer bounds invalidates any recorded current column.  */
+  invalidate_current_column ();
+
   if (cur)
     set_buffer_internal (cur);
 

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