Merge from trunk.

[gnu-emacs] / lisp / emacs-lisp / debug.el

diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index 12189862d6d5bfd0b67fae55406072bf30b1e60f..157749500e7f90ec6faef5d79bf9c5ac78f9f030 100644 (file)
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -1,7 +1,6 @@
 ;;; debug.el --- debuggers and related commands for Emacs
 
-;; Copyright (C) 1985, 1986, 1994, 2001, 2002, 2003, 2004,
-;;   2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
+;; Copyright (C) 1985-1986, 1994, 2001-2011 Free Software Foundation, Inc.
 
 ;; Maintainer: FSF
 ;; Keywords: lisp, tools, maint
@@ -103,7 +102,7 @@ and `debugger-reenable' to temporarily disable debug-on-entry.")
 (setq debugger 'debug)
 ;;;###autoload
 (defun debug (&rest debugger-args)
-  "Enter debugger.  To return, type \\<debugger-mode-map>`\\[debugger-continue]'.
+  "Enter debugger.  \\<debugger-mode-map>`\\[debugger-continue]' returns from the debugger.
 Arguments are mainly for use when this is called from the internals
 of the evaluator.
 
@@ -119,6 +118,10 @@ first will be printed into the backtrace buffer."
     (let (debugger-value
          (debug-on-error nil)
          (debug-on-quit nil)
+         (debugger-previous-state
+           (if (get-buffer "*Backtrace*")
+               (with-current-buffer (get-buffer "*Backtrace*")
+                 (list major-mode (buffer-string)))))
          (debugger-buffer (get-buffer-create "*Backtrace*"))
          (debugger-old-buffer (current-buffer))
          (debugger-step-after-exit nil)
@@ -215,8 +218,6 @@ first will be printed into the backtrace buffer."
              ;; recreate it every time the debugger stops, so instead we'll
              ;; erase it (and maybe hide it) but keep it alive.
              (with-current-buffer debugger-buffer
-               (erase-buffer)
-               (fundamental-mode)
                (with-selected-window (get-buffer-window debugger-buffer 0)
                   (when (and (window-dedicated-p (selected-window))
                              (not debugger-will-be-back))
@@ -233,7 +234,18 @@ first will be printed into the backtrace buffer."
                     ;; to be left at the top-level, still working on how
                     ;; best to do that.
                     (bury-buffer))))
-           (kill-buffer debugger-buffer))
+            (unless debugger-previous-state
+              (kill-buffer debugger-buffer)))
+          ;; Restore the previous state of the debugger-buffer, in case we were
+          ;; in a recursive invocation of the debugger.
+          (when (buffer-live-p debugger-buffer)
+            (with-current-buffer debugger-buffer
+              (let ((inhibit-read-only t))
+                (erase-buffer)
+                (if (null debugger-previous-state)
+                    (fundamental-mode)
+                  (insert (nth 1 debugger-previous-state))
+                  (funcall (nth 0 debugger-previous-state))))))
          (with-timeout-unsuspend debugger-with-timeout-suspend)
          (set-match-data debugger-outer-match-data)))
       ;; Put into effect the modified values of these variables
@@ -890,5 +902,4 @@ To specify a nil argument interactively, exit with an empty minibuffer."
 
 (provide 'debug)
 
-;; arch-tag: b6ec7047-f801-4103-9c63-d69322db9d3b
 ;;; debug.el ends here