GNU bug report logs - #640
Forward: Buffer being killed not current in kill-buffer-hook

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From: Max Mikhanosha <max <at> openchat.com>
To: emacs-pretest-bug <at> gnu.org
Subject: bug#640: Forward: Buffer being killed not current in kill-buffer-hook 
Date: Fri, 01 Aug 2008 12:22:52 -0400

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

I posted this to emacs-dev, but there was no response. This is still
happenning to me with latest CVS build.

[Message part 2 (message/rfc822, inline)]

From: Max Mikhanosha <max <at> openchat.com>
To: emacs-devel <at> gnu.org
Subject: Buffer being killed not current in kill-buffer-hook 
Date: Sat, 19 Jul 2008 16:29:25 -0400

When using multi-tty emacsclient, the following piece of code demostrates the problem:

DISPLAY is unset, CVS Emacs started with --no-init-file

(require 'server)
(progn (setq server-name "test")
       (server-start))
(defun print-current-buffer ()
  (message "current-buffer=%s" (current-buffer)))
(add-hook 'kill-buffer-hook 'print-current-buffer)

Now from a different screen session, connect with emacsclient like so:
"lib-src/emacsclient -c -s test foo". New tty frame will be created. 
Immeditely kill the buffer, it will ask "Buffer has existing clients"
say "yes". emacsclient will disconnect from a server.

In the *Messages* buffer on the server frame:

When done with a buffer, type C-x #
(No files need saving)
current-buffer=*scratch*

All the code that uses kill-buffer-hook rightfully assumes that the
buffer being killed will be current buffer when called, as that is
what is stated in the kill-buffer-hook documentation. For example
saveplace does not work because of this.. ERC leaves a channel if 
unrelated buffer is killed on a different terminal, etc.

I had fixed this with the following patch, altho I don't know enough
about server.el logic to figure out if what it does is ok? Seems to
have fixed the bug and not broke anything else:

Index: lisp/server.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/server.el,v
retrieving revision 1.166
diff -u -b -r1.166 server.el
--- lisp/server.el	6 May 2008 07:57:49 -0000	1.166
+++ lisp/server.el	19 Jul 2008 20:28:26 -0000
@@ -1084,7 +1084,8 @@
 	  ;; tell it that it is done, and forget it entirely.
 	  (unless buffers
 	    (server-log "Close" proc)
-	    (server-delete-client proc)))))
+            (save-current-buffer 
+              (server-delete-client proc))))))
     (when (and (bufferp buffer) (buffer-name buffer))
       ;; We may or may not kill this buffer;
       ;; if we do, do not call server-buffer-done recursively

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