(debug): Behave sensibly if pop-up-frames is set.

diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index 150686ce4ce61ba58e4d74d272b0355c48983f6e..68a26d8ebaba5bcd0ad3f72e23377a2df614567c 100644 (file)
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -60,7 +60,7 @@ first will be printed into the backtrace buffer."
        (debug-on-error nil)
        (debug-on-quit nil)
        (debugger-buffer (let ((default-major-mode 'fundamental-mode))
-                          (generate-new-buffer "*Backtrace*")))
+                          (get-buffer-create "*Backtrace*")))
        (debugger-old-buffer (current-buffer))
        (debugger-step-after-exit nil)
        ;; Don't keep reading from an executing kbd macro!
@@ -136,9 +136,18 @@ first will be printed into the backtrace buffer."
                    (buffer-read-only t))
                (message "")
                (recursive-edit))))
-       ;; So that users do not try to execute debugger commands
-       ;;  in an invalid context
-       (kill-buffer debugger-buffer)
+       ;; Kill or at least neuter the backtrace buffer, so that users
+       ;; don't try to execute debugger commands in an invalid context.
+       (if (get-buffer-window debugger-buffer 'visible)
+           ;; Still visible despite the save-window-excursion?  Maybe it
+           ;; it's in a pop-up frame.  It would be annoying to delete and
+           ;; recreate it every time the debugger stops, so instead we'll
+           ;; erase it but leave it visible.
+           (save-excursion
+             (set-buffer debugger-buffer)
+             (erase-buffer)
+             (fundamental-mode))
+         (kill-buffer debugger-buffer))
        (store-match-data debugger-match-data)))
     ;; Put into effect the modified values of these variables
     ;; in case the user set them with the `e' command.