Subject: Re: bug#7946: Referring to a marker changes Emacs' behaviour.
From: Stefan Monnier <[email-masked]>
To: Le Wang <[email-masked]>
Cc: [email-masked]
Date: Wed, 02 Feb 2011 10:54:56 -0500
List-Id: <debbugs-submit.debbugs.gnu.org>

> 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);