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debugger-toggle-locals
From: |
Helmut Eller |
Subject: |
debugger-toggle-locals |
Date: |
Sat, 23 Nov 2013 09:57:17 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3.50 (gnu/linux) |
I'd like to add a new debugger command `debugger-toggle-locals', that
displays the names and values of local variables of a stack frame.
This looks like so:
Debugger entered--Lisp error: (void-variable d)
foo(10 113)
foo(9 114)
x: 9
y: 114
z: (9 . 114)
foo(8 115)
The command inserts the lines with x:, y: and z:. Pressing t a second
time deletes those lines again.
To do this I needed a new primitive `backtrace-locals' which extracts
the names and values from the specpdl, similar to backtrace-eval. This
works for interpreted functions and compiled non-lexically-scoped
functions. Compiled lexically scoped functions would need compiler
support, in the form of stackmaps. Until somebody implements that, the
command only displays "no locals".
Helmut
diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index 6c7a0d2..d8596aa 100644
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -494,9 +494,13 @@ removes itself from that hook."
(forward-line 1)
(while (progn
(forward-char 2)
- (if (= (following-char) ?\()
- (forward-sexp 1)
- (forward-sexp 2))
+ (cond ((debugger--locals-visible-p)
+ (goto-char (next-single-char-property-change
+ (1+ (point)) 'debugger-locals-visible-p)))
+ ((= (following-char) ?\()
+ (forward-sexp 1))
+ (t
+ (forward-sexp 2)))
(forward-line 1)
(<= (point) opoint))
(if (looking-at " *;;;")
@@ -558,6 +562,89 @@ The environment used is the one when entering the
activation frame at point."
(prin1 val t)
(let ((str (eval-expression-print-format val)))
(if str (princ str t))))))))
+
+(defun debugger--backtrace-base ()
+ "Return the function name that marks the top of the backtrace.
+See `backtrace-frame'."
+ (cond ((eq 'debug--implement-debug-on-entry
+ (cadr (backtrace-frame 1 'debug)))
+ 'debug--implement-debug-on-entry)
+ (t 'debug)))
+
+(defun debugger--locals-visible-p ()
+ "Are the local variables of the current stack frame visible?"
+ (save-excursion
+ (move-to-column 2)
+ (get-text-property (point) 'debugger-locals-visible-p)))
+
+(defun debugger--insert-locals (locals)
+ "Insert the local variables LOCALS at point."
+ ;; A bit messy because we need to deal with lexical frames, i.e.
+ ;; the ones with the magic symbol 'internal-interpreter-environment.
+ (when (null locals)
+ (insert "\n [no locals]"))
+ (dolist (s+v locals)
+ (let ((symbol (car s+v))
+ (value (cdr s+v))
+ (print-escape-newlines t)
+ (insert (lambda (s v)
+ (insert "\n ")
+ (prin1 s (current-buffer))
+ (insert ": ")
+ (prin1 v (current-buffer)))))
+ (cond ((string= (symbol-name symbol) "internal-interpreter-environment")
+ (cond ((or (null value)
+ (and (null (cdr value))
+ (symbol (car value))))
+ (insert "\n [no locals]"))
+ (t
+ (dolist (s+v value)
+ (unless (symbolp s+v)
+ (let ((symbol (car s+v))
+ (value (cdr s+v)))
+ (funcall insert symbol value)))))))
+ (t
+ (funcall insert symbol value))))))
+
+(defun debugger--show-locals ()
+ "For the frame at point, insert locals and add text properties."
+ (let* ((nframe (debugger-frame-number 'skip-base))
+ (base (debugger--backtrace-base))
+ (locals (backtrace-locals nframe base))
+ (inhibit-read-only t))
+ (save-excursion
+ (let ((start (progn
+ (beginning-of-line)
+ (skip-chars-forward " ")
+ (point))))
+ (end-of-line)
+ (debugger--insert-locals locals)
+ (add-text-properties start (point) '(debugger-locals-visible-p t))))))
+
+(defun debugger--hide-locals ()
+ "Delete local variables and remove the text property."
+ (let* ((col (current-column))
+ (end (progn
+ (move-to-column 2)
+ (next-single-char-property-change
+ (point) 'debugger-locals-visible-p)))
+ (start (previous-single-char-property-change
+ end 'debugger-locals-visible-p))
+ (inhibit-read-only t))
+ (goto-char start)
+ (end-of-line)
+ (remove-text-properties start end '(debugger-locals-visible-p))
+ (delete-region (point) end)
+ (move-to-column col)))
+
+(defun debugger-toggle-locals ()
+ "Show or hide local variables of the current stack frame."
+ (interactive)
+ (cond ((debugger--locals-visible-p)
+ (debugger--hide-locals))
+ (t
+ (debugger--show-locals))))
+
(defvar debugger-mode-map
(let ((map (make-keymap))
@@ -575,6 +662,7 @@ The environment used is the one when entering the
activation frame at point."
(define-key map "h" 'describe-mode)
(define-key map "q" 'top-level)
(define-key map "e" 'debugger-eval-expression)
+ (define-key map "t" 'debugger-toggle-locals)
(define-key map " " 'next-line)
(define-key map "R" 'debugger-record-expression)
(define-key map "\C-m" 'debug-help-follow)
diff --git a/src/eval.c b/src/eval.c
index d3fcec5..a455d95 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3576,6 +3576,53 @@ NFRAMES and BASE specify the activation frame to use, as
in `backtrace-frame'.
from the debugger. */
return unbind_to (count, eval_sub (exp));
}
+
+DEFUN ("backtrace-locals", Fbacktrace_locals, Sbacktrace_locals, 1, 2, NULL,
+ doc: /* Return names and values of local variables of a stack frame.
+NFRAMES and BASE specify the activation frame to use, as in `backtrace-frame'.
+The result is an alist. */)
+ (Lisp_Object nframes, Lisp_Object base)
+{
+ union specbinding *frame = get_backtrace_frame (nframes, base);
+ union specbinding *olderframe =
+ get_backtrace_frame (make_number (XFASTINT (nframes) + 1), base);
+ ptrdiff_t distance = specpdl_ptr - olderframe;
+ Lisp_Object result = Qnil;
+ eassert (distance >= 0);
+
+ if (!backtrace_p (frame))
+ error ("Activation frame not found!");
+ if (!backtrace_p (olderframe))
+ error ("Activation frame not found!");
+
+ /* move values to specpdl */
+ backtrace_eval_unrewind (distance);
+
+ /* grab values */
+ {
+ union specbinding *tmp = frame;
+ for (; tmp > olderframe; tmp--)
+ {
+ switch (tmp->kind)
+ {
+ case SPECPDL_LET:
+ case SPECPDL_LET_DEFAULT:
+ case SPECPDL_LET_LOCAL:
+ {
+ Lisp_Object sym = specpdl_symbol (tmp);
+ Lisp_Object val = specpdl_old_value (tmp);
+ result = Fcons (Fcons (sym, val), result);
+ }
+ }
+ }
+ }
+
+ /* restore values from specpdl to orignal place */
+ backtrace_eval_unrewind (-distance);
+
+ return result;
+}
+
void
mark_specpdl (void)
@@ -3824,6 +3871,7 @@ alist of active lexical bindings. */);
defsubr (&Sbacktrace);
defsubr (&Sbacktrace_frame);
defsubr (&Sbacktrace_eval);
+ defsubr (&Sbacktrace_locals);
defsubr (&Sspecial_variable_p);
defsubr (&Sfunctionp);
}
- debugger-toggle-locals,
Helmut Eller <=