bug#20034: 25.0.50; [PATCH] gud never displays a source buffer over the gud window

[Dima Kogan]

Hi.

Sometime between emacs 23 and emacs 24 the behavior of display-buffer
changed to show the buffer in the current window at times (emacs 23
always used a different window). As a (presumably unwanted) side-effect
it is now possible for a gud user to lose the gud window as one
interacts with gud. I often encounter this when I open a core dump in
gud-gdb, then invoke "up" repeatedly to traverse the call stack.
Eventually a source buffer takes over the gud window and I have to
switch back to gud to keep navigating the stack.

Trivial recipe:

 1. Create any C program in /tmp/tst.c. Can be as simple as

  int main(void)
  {
      return 0;
  }

 2. gcc -g -o tst tst.c

 3. emacs -Q

 4. C-x 3 (split window horizontally)

 5. C-x C-f tst.c (open tst.c)

 6. M-x gud-gdb, 'gdb --fullname /tmp/tst' (start up gud in the same
    window that's currently showing tst.c)

 7. b main

 8. r

On my machine this switches to tst.c on top of the gud buffer, replacing
gud in its window. With the attached patch this does not happen.

This is similar, but not identical to bug

 http://debbugs.gnu.org/cgi/bugreport.cgi?bug=17675

The proposed fix in that bug does not handle the above recipe.


>From d3b42eb74be145969dd829aeedcb7ceac629de03 Mon Sep 17 00:00:00 2001
From: Dima Kogan <dima@secretsauce.net>
Date: Sat, 7 Mar 2015 17:37:20 -0800
Subject: [PATCH] gud never displays a source buffer over the gud window

---
 lisp/progmodes/gud.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/progmodes/gud.el b/lisp/progmodes/gud.el
index 42c5b20..ac830e7 100644
--- a/lisp/progmodes/gud.el
+++ b/lisp/progmodes/gud.el
@@ -2813,7 +2813,7 @@ Obeying it means displaying in another window the 
specified file and line."
            (gud-find-file true-file)))
         (window (and buffer
                      (or (get-buffer-window buffer)
-                         (display-buffer buffer))))
+                         (display-buffer buffer '(nil (inhibit-same-window . 
t))))))
         (pos))
     (when buffer
       (with-current-buffer buffer
-- 
2.1.4