Re: Debugging functions with lexical-binding

[Helmut Eller <eller.helmut@gmail.com>]

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* Stefan Monnier [2011-05-30 04:13] writes:

>> What are the commands to inspect local variables of lexical functions?
>
> M-x esp RET

That's too cryptic for me.  What do you mean?

>> Pressing C-M-c reduces one level of recursive edit but puts the
>> *Backtrace* buffer in fundamental-mode which is IMO also wrong.]
>
> Yup, the *Backtrace* buffer's content and major-mode are not properly
> saved&restored upon entry to and exit from the debugger.  Patch welcome,

Below is a simple patch.  It only restores the content but not buffer
local variables.

Helmut


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=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog	2011-05-30 12:23:56 +0000
+++ lisp/ChangeLog	2011-05-31 07:08:41 +0000
@@ -1,3 +1,11 @@
+2011-05-31  Helmut Eller  <eller.helmut@gmail.com>
+
+	Try to deal with recursive debuggers and C-M-c.
+
+	* debug.el (debug): Restore the previous content of the
+	*Backtrace* buffer when we exit with C-M-c.  Restoring buffer
+	local variables would be annoyingly difficult.
+
 2011-05-30  Leo Liu  <sdl.web@gmail.com>
 
 	* net/rcirc.el (rcirc-debug-buffer): Use visible buffer name.

=== modified file 'lisp/emacs-lisp/debug.el'
--- lisp/emacs-lisp/debug.el	2011-03-20 03:53:45 +0000
+++ lisp/emacs-lisp/debug.el	2011-05-31 06:45:28 +0000
@@ -120,6 +120,7 @@
 	  (debug-on-quit nil)
 	  (debugger-buffer (get-buffer-create "*Backtrace*"))
 	  (debugger-old-buffer (current-buffer))
+	  (debugger-previous-contents nil)
 	  (debugger-step-after-exit nil)
           (debugger-will-be-back nil)
 	  ;; Don't keep reading from an executing kbd macro!
@@ -181,6 +182,7 @@
 		  (when (eq 'lambda (car-safe (cadr (backtrace-frame 4))))
 		    (backtrace-debug 5 t)))
                 (pop-to-buffer debugger-buffer)
+		(setq debugger-previous-contents (buffer-string))
 		(debugger-mode)
 		(debugger-setup-buffer debugger-args)
 		(when noninteractive
@@ -215,7 +217,7 @@
 	      ;; erase it (and maybe hide it) but keep it alive.
 	      (with-current-buffer debugger-buffer
 		(erase-buffer)
-		(fundamental-mode)
+		(insert debugger-previous-contents)
 		(with-selected-window (get-buffer-window debugger-buffer 0)
                   (when (and (window-dedicated-p (selected-window))
                              (not debugger-will-be-back))