GNU bug report logs - #9462
24.0.50; Initial point in debugger

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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; Initial point in debugger
Date: Thu, 08 Sep 2011 11:03:33 +0200

When entering the debugger, point is placed at seemingly random
positions.  E.g. executing this file

(progn
  (defun foo (n)
    (cond ((zerop n) (debug))
	  (t (foo (1- n)))))
  (foo 100))

with emacs -Q -l foo.el opens a *Backtrace* buffer but the cursor is
somewhere near the end of the buffer.  When debugging other code, it's
often somewhere in the middle sometimes at the beginning.

In the old days, point was consistently placed at the first line of the
backtrace (top-of-stack).  That was more useful: it was easier to see
the error message; using d was more convenient as the first line is
almost always the most interesting one.




In GNU Emacs 24.0.50.4 (i686-pc-linux-gnu, GTK+ Version 2.20.1)
 of 2011-09-05 on ix
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
configured using `configure  '--enable-asserts' '--enable-checking' '--with-gif=no' '--with-gnutls=no' 'CFLAGS=-g3 -O0''

Message #10 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: Re: bug#9462: 24.0.50; Initial point in debugger
Date: Sat, 10 Sep 2011 20:13:14 +0200

* Helmut Eller [2011-09-08 09:03] writes:

> When entering the debugger, point is placed at seemingly random
> positions.

I think this would fix the problem:

=== modified file 'lisp/emacs-lisp/debug.el'
--- lisp/emacs-lisp/debug.el	2011-08-22 21:16:46 +0000
+++ lisp/emacs-lisp/debug.el	2011-09-10 18:10:29 +0000
@@ -336,7 +336,8 @@
 			(with-current-buffer (car tem)
 			  (point))))
 	(pop tem))))
-  (debugger-make-xrefs))
+  (save-excursion
+    (debugger-make-xrefs)))
 
 (defun debugger-make-xrefs (&optional buffer)
   "Attach cross-references to function names in the `*Backtrace*' buffer."

Message #15 received at 9462-done <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 9462-done <at> debbugs.gnu.org
Subject: Re: bug#9462: 24.0.50; Initial point in debugger
Date: Tue, 13 Sep 2011 17:04:22 -0400

Version: 24.1

Helmut Eller wrote:

> -  (debugger-make-xrefs))
> +  (save-excursion
> +    (debugger-make-xrefs)))

Thanks for the diagnosis, I installed a similar fix.

This looks like more fallout from "save-excursion + set-buffer ->
with-current-buffer".

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