lisp/emacs-lisp/debug.el

   1 ;;; debug.el --- debuggers and related commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1994, 2001 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: lisp, tools, maint
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; This is a major mode documented in the Emacs manual.
  28
  29 ;;; Code:
  30
  31 (require 'button)
  32
  33 (defgroup debugger nil
  34   "Debuggers and related commands for Emacs."
  35   :prefix "debugger-"
  36   :group 'debug)
  37
  38 (defcustom debugger-mode-hook nil
  39   "*Hooks run when `debugger-mode' is turned on."
  40   :type 'hook
  41   :group 'debugger
  42   :version "20.3")
  43
  44 (defcustom debugger-batch-max-lines 40
  45   "*Maximum lines to show in debugger buffer in a noninteractive Emacs.
  46 When the debugger is entered and Emacs is running in batch mode,
  47 if the backtrace text has more than this many lines,
  48 the middle is discarded, and just the beginning and end are displayed."
  49   :type 'integer
  50   :group 'debugger
  51   :version "21.1")
  52
  53 (defcustom debug-function-list nil
  54   "List of functions currently set for debug on entry."
  55   :type '(repeat function)
  56   :group 'debugger)
  57
  58 (defcustom debugger-step-after-exit nil
  59   "Non-nil means \"single-step\" after the debugger exits."
  60   :type 'boolean
  61   :group 'debugger)
  62
  63 (defvar debugger-value nil
  64   "This is the value for the debugger to return, when it returns.")
  65
  66 (defvar debugger-old-buffer nil
  67   "This is the buffer that was current when the debugger was entered.")
  68
  69 (defvar debugger-previous-backtrace nil
  70   "The contents of the previous backtrace (including text properties).
  71 This is to optimize `debugger-make-xrefs'.")
  72
  73 (defvar debugger-outer-match-data)
  74 (defvar debugger-outer-load-read-function)
  75 (defvar debugger-outer-overriding-local-map)
  76 (defvar debugger-outer-overriding-terminal-local-map)
  77 (defvar debugger-outer-track-mouse)
  78 (defvar debugger-outer-last-command)
  79 (defvar debugger-outer-this-command)
  80 ;; unread-command-char is obsolete,
  81 ;; but we still save and restore it
  82 ;; in case some user program still tries to set it.
  83 (defvar debugger-outer-unread-command-char)
  84 (defvar debugger-outer-unread-command-events)
  85 (defvar debugger-outer-unread-post-input-method-events)
  86 (defvar debugger-outer-last-input-event)
  87 (defvar debugger-outer-last-command-event)
  88 (defvar debugger-outer-last-nonmenu-event)
  89 (defvar debugger-outer-last-event-frame)
  90 (defvar debugger-outer-standard-input)
  91 (defvar debugger-outer-standard-output)
  92 (defvar debugger-outer-inhibit-redisplay)
  93 (defvar debugger-outer-cursor-in-echo-area)
  94
  95 ;;;###autoload
  96 (setq debugger 'debug)
  97 ;;;###autoload
  98 (defun debug (&rest debugger-args)
  99   "Enter debugger.  To return, type \\<debugger-mode-map>`\\[debugger-continue]'.
 100 Arguments are mainly for use when this is called from the internals
 101 of the evaluator.
 102
 103 You may call with no args, or you may pass nil as the first arg and
 104 any other args you like.  In that case, the list of args after the
 105 first will be printed into the backtrace buffer."
 106   (interactive)
 107   (if inhibit-redisplay
 108       ;; Don't really try to enter debugger within an eval from redisplay.
 109       debugger-value
 110     (unless noninteractive
 111       (message "Entering debugger..."))
 112     (let (debugger-value
 113           (debug-on-error nil)
 114           (debug-on-quit nil)
 115           (debugger-buffer (let ((default-major-mode 'fundamental-mode))
 116                              (get-buffer-create "*Backtrace*")))
 117           (debugger-old-buffer (current-buffer))
 118           (debugger-step-after-exit nil)
 119           ;; Don't keep reading from an executing kbd macro!
 120           (executing-kbd-macro nil)
 121           ;; Save the outer values of these vars for the `e' command
 122           ;; before we replace the values.
 123           (debugger-outer-match-data (match-data))
 124           (debugger-outer-load-read-function load-read-function)
 125           (debugger-outer-overriding-local-map overriding-local-map)
 126           (debugger-outer-overriding-terminal-local-map
 127            overriding-terminal-local-map)
 128           (debugger-outer-track-mouse track-mouse)
 129           (debugger-outer-last-command last-command)
 130           (debugger-outer-this-command this-command)
 131           (debugger-outer-unread-command-char unread-command-char)
 132           (debugger-outer-unread-command-events unread-command-events)
 133           (debugger-outer-unread-post-input-method-events
 134            unread-post-input-method-events)
 135           (debugger-outer-last-input-event last-input-event)
 136           (debugger-outer-last-command-event last-command-event)
 137           (debugger-outer-last-nonmenu-event last-nonmenu-event)
 138           (debugger-outer-last-event-frame last-event-frame)
 139           (debugger-outer-standard-input standard-input)
 140           (debugger-outer-standard-output standard-output)
 141           (debugger-outer-inhibit-redisplay inhibit-redisplay)
 142           (debugger-outer-cursor-in-echo-area cursor-in-echo-area))
 143       ;; Set this instead of binding it, so that `q'
 144       ;; will not restore it.
 145       (setq overriding-terminal-local-map nil)
 146       ;; Don't let these magic variables affect the debugger itself.
 147       (let ((last-command nil) this-command track-mouse
 148             (unread-command-char -1) unread-command-events
 149             unread-post-input-method-events
 150             last-input-event last-command-event last-nonmenu-event
 151             last-event-frame
 152             overriding-local-map
 153             load-read-function
 154             ;; If we are inside a minibuffer, allow nesting
 155             ;; so that we don't get an error from the `e' command.
 156             (enable-recursive-minibuffers
 157              (or enable-recursive-minibuffers (> (minibuffer-depth) 0)))
 158             (standard-input t) (standard-output t)
 159             inhibit-redisplay
 160             (cursor-in-echo-area nil))
 161         (unwind-protect
 162             (save-excursion
 163               (save-window-excursion
 164                 (pop-to-buffer debugger-buffer)
 165                 (debugger-mode)
 166                 (debugger-setup-buffer debugger-args)
 167                 (when noninteractive
 168                   ;; If the backtrace is long, save the beginning
 169                   ;; and the end, but discard the middle.
 170                   (when (> (count-lines (point-min) (point-max))
 171                            debugger-batch-max-lines)
 172                     (goto-char (point-min))
 173                     (forward-line (/ 2 debugger-batch-max-lines))
 174                     (let ((middlestart (point)))
 175                       (goto-char (point-max))
 176                       (forward-line (- (/ 2 debugger-batch-max-lines)
 177                                        debugger-batch-max-lines))
 178                       (delete-region middlestart (point)))
 179                     (insert "...\n"))
 180                   (goto-char (point-min))
 181                   (message (buffer-string))
 182                   (kill-emacs))
 183                 (if (eq (car debugger-args) 'debug)
 184                     ;; Skip the frames for backtrace-debug, byte-code, and debug.
 185                     (backtrace-debug 3 t))
 186                 (debugger-reenable)
 187                 (message "")
 188                 (let ((inhibit-trace t)
 189                       (standard-output nil)
 190                       (buffer-read-only t))
 191                   (message "")
 192                   ;; Make sure we unbind buffer-read-only in the right buffer.
 193                   (save-excursion
 194                     (recursive-edit)))))
 195           ;; Kill or at least neuter the backtrace buffer, so that users
 196           ;; don't try to execute debugger commands in an invalid context.
 197           (if (get-buffer-window debugger-buffer 'visible)
 198               ;; Still visible despite the save-window-excursion?  Maybe it
 199               ;; it's in a pop-up frame.  It would be annoying to delete and
 200               ;; recreate it every time the debugger stops, so instead we'll
 201               ;; erase it but leave it visible.
 202               (save-excursion
 203                 (set-buffer debugger-buffer)
 204                 (erase-buffer)
 205                 (fundamental-mode))
 206             (kill-buffer debugger-buffer))
 207           (set-match-data debugger-outer-match-data)))
 208       ;; Put into effect the modified values of these variables
 209       ;; in case the user set them with the `e' command.
 210       (setq load-read-function debugger-outer-load-read-function)
 211       (setq overriding-local-map debugger-outer-overriding-local-map)
 212       (setq overriding-terminal-local-map
 213             debugger-outer-overriding-terminal-local-map)
 214       (setq track-mouse debugger-outer-track-mouse)
 215       (setq last-command debugger-outer-last-command)
 216       (setq this-command debugger-outer-this-command)
 217       (setq unread-command-char debugger-outer-unread-command-char)
 218       (setq unread-command-events debugger-outer-unread-command-events)
 219       (setq unread-post-input-method-events
 220             debugger-outer-unread-post-input-method-events)
 221       (setq last-input-event debugger-outer-last-input-event)
 222       (setq last-command-event debugger-outer-last-command-event)
 223       (setq last-nonmenu-event debugger-outer-last-nonmenu-event)
 224       (setq last-event-frame debugger-outer-last-event-frame)
 225       (setq standard-input debugger-outer-standard-input)
 226       (setq standard-output debugger-outer-standard-output)
 227       (setq inhibit-redisplay debugger-outer-inhibit-redisplay)
 228       (setq cursor-in-echo-area debugger-outer-cursor-in-echo-area)
 229       (setq debug-on-next-call debugger-step-after-exit)
 230       debugger-value)))
 231 \f
 232 (defun debugger-setup-buffer (debugger-args)
 233   "Initialize the `*Backtrace*' buffer for entry to the debugger.
 234 That buffer should be current already."
 235   (setq buffer-read-only nil)
 236   (erase-buffer)
 237   (set-buffer-multibyte nil)
 238   (let ((standard-output (current-buffer))
 239         (print-escape-newlines t)
 240         (print-level 8)
 241         (print-length 50))
 242     (backtrace))
 243   (goto-char (point-min))
 244   (delete-region (point)
 245                  (progn
 246                    (search-forward "\n  debug(")
 247                    (forward-line 1)
 248                    (point)))
 249   (insert "Debugger entered")
 250   ;; lambda is for debug-on-call when a function call is next.
 251   ;; debug is for debug-on-entry function called.
 252   (cond ((memq (car debugger-args) '(lambda debug))
 253          (insert "--entering a function:\n")
 254          (if (eq (car debugger-args) 'debug)
 255              (progn
 256                (delete-char 1)
 257                (insert ?*)
 258                (beginning-of-line))))
 259         ;; Exiting a function.
 260         ((eq (car debugger-args) 'exit)
 261          (insert "--returning value: ")
 262          (setq debugger-value (nth 1 debugger-args))
 263          (prin1 debugger-value (current-buffer))
 264          (insert ?\n)
 265          (delete-char 1)
 266          (insert ? )
 267          (beginning-of-line))
 268         ;; Debugger entered for an error.
 269         ((eq (car debugger-args) 'error)
 270          (insert "--Lisp error: ")
 271          (prin1 (nth 1 debugger-args) (current-buffer))
 272          (insert ?\n))
 273         ;; debug-on-call, when the next thing is an eval.
 274         ((eq (car debugger-args) t)
 275          (insert "--beginning evaluation of function call form:\n"))
 276         ;; User calls debug directly.
 277         (t
 278          (insert ": ")
 279          (prin1 (if (eq (car debugger-args) 'nil)
 280                     (cdr debugger-args) debugger-args)
 281                 (current-buffer))
 282          (insert ?\n)))
 283   ;; After any frame that uses eval-buffer,
 284   ;; insert a line that states the buffer position it's reading at.
 285   (save-excursion
 286     (while (re-search-forward "^  eval-buffer(" nil t)
 287       (end-of-line)
 288       (insert (format "\n  ;;; Reading at buffer position %d"
 289                       (with-current-buffer (nth 2 (backtrace-frame (debugger-frame-number)))
 290                         (point))))))
 291   (debugger-make-xrefs))
 292
 293 (defun debugger-make-xrefs (&optional buffer)
 294   "Attach cross-references to symbol names in the `*Backtrace*' buffer."
 295   (interactive "b")
 296   (save-excursion
 297     (set-buffer (or buffer (current-buffer)))
 298     (setq buffer (current-buffer))
 299     (let ((buffer-read-only nil)
 300           (old-end (point-min)) (new-end (point-min)))
 301       ;; If we saved an old backtrace, find the common part
 302       ;; between the new and the old.
 303       ;; Compare line by line, starting from the end,
 304       ;; because that's the part that is likely to be unchanged.
 305       (if debugger-previous-backtrace
 306           (let (old-start new-start (all-match t))
 307             (goto-char (point-max))
 308             (with-temp-buffer
 309               (insert debugger-previous-backtrace)
 310               (while (and all-match (not (bobp)))
 311                 (setq old-end (point))
 312                 (forward-line -1)
 313                 (setq old-start (point))
 314                 (with-current-buffer buffer
 315                   (setq new-end (point))
 316                   (forward-line -1)
 317                   (setq new-start (point)))
 318                 (if (not (zerop
 319                           (compare-buffer-substrings
 320                            (current-buffer) old-start old-end
 321                            buffer new-start new-end)))
 322                     (setq all-match nil))))
 323             ;; Now new-end is the position of the start of the
 324             ;; unchanged part in the current buffer, and old-end is
 325             ;; the position of that same text in the saved old
 326             ;; backtrace.  But we must subtract (point-min) since strings are
 327             ;; indexed in origin 0.
 328
 329             ;; Replace the unchanged part of the backtrace
 330             ;; with the text from debugger-previous-backtrace,
 331             ;; since that already has the proper xrefs.
 332             ;; With this optimization, we only need to scan
 333             ;; the changed part of the backtrace.
 334             (delete-region new-end (point-max))
 335             (goto-char (point-max))
 336             (insert (substring debugger-previous-backtrace
 337                                (- old-end (point-min))))
 338             ;; Make the unchanged part of the backtrace inaccessible
 339             ;; so it won't be scanned.
 340             (narrow-to-region (point-min) new-end)))
 341
 342       ;; Scan the new part of the backtrace, inserting xrefs.
 343       (goto-char (point-min))
 344       (while (progn
 345                (skip-syntax-forward "^w_")
 346                (not (eobp)))
 347         (let* ((beg (point))
 348                (end (progn (skip-syntax-forward "w_") (point)))
 349                (sym (intern-soft (buffer-substring-no-properties
 350                                   beg end)))
 351                (file (and sym (symbol-file sym))))
 352           (when file
 353             (goto-char beg)
 354             ;; help-xref-button needs to operate on something matched
 355             ;; by a regexp, so set that up for it.
 356             (re-search-forward "\\(\\(\\sw\\|\\s_\\)+\\)")
 357             (help-xref-button 1 'help-function-def sym file)))
 358         (forward-line 1))
 359       (widen))
 360     (setq debugger-previous-backtrace (buffer-string))))
 361 \f
 362 (defun debugger-step-through ()
 363   "Proceed, stepping through subexpressions of this expression.
 364 Enter another debugger on next entry to eval, apply or funcall."
 365   (interactive)
 366   (setq debugger-step-after-exit t)
 367   (message "Proceeding, will debug on next eval or call.")
 368   (exit-recursive-edit))
 369
 370 (defun debugger-continue ()
 371   "Continue, evaluating this expression without stopping."
 372   (interactive)
 373   (unless debugger-may-continue
 374     (error "Cannot continue"))
 375   (message "Continuing.")
 376   (exit-recursive-edit))
 377
 378 (defun debugger-return-value (val)
 379   "Continue, specifying value to return.
 380 This is only useful when the value returned from the debugger
 381 will be used, such as in a debug on exit from a frame."
 382   (interactive "XReturn value (evaluated): ")
 383   (setq debugger-value val)
 384   (princ "Returning " t)
 385   (prin1 debugger-value)
 386   (exit-recursive-edit))
 387
 388 (defun debugger-jump ()
 389   "Continue to exit from this frame, with all debug-on-entry suspended."
 390   (interactive)
 391   (debugger-frame)
 392   ;; Turn off all debug-on-entry functions
 393   ;; but leave them in the list.
 394   (let ((list debug-function-list))
 395     (while list
 396       (fset (car list)
 397             (debug-on-entry-1 (car list) (symbol-function (car list)) nil))
 398       (setq list (cdr list))))
 399   (message "Continuing through this frame")
 400   (exit-recursive-edit))
 401
 402 (defun debugger-reenable ()
 403   "Turn all debug-on-entry functions back on."
 404   (let ((list debug-function-list))
 405     (while list
 406       (or (consp (symbol-function (car list)))
 407           (debug-convert-byte-code (car list)))
 408       (fset (car list)
 409             (debug-on-entry-1 (car list) (symbol-function (car list)) t))
 410       (setq list (cdr list)))))
 411
 412 (defun debugger-frame-number ()
 413   "Return number of frames in backtrace before the one point points at."
 414   (save-excursion
 415     (beginning-of-line)
 416     (let ((opoint (point))
 417           (count 0))
 418       (while (not (eq (cadr (backtrace-frame count)) 'debug))
 419         (setq count (1+ count)))
 420       (goto-char (point-min))
 421       (if (or (equal (buffer-substring (point) (+ (point) 6))
 422                      "Signal")
 423               (equal (buffer-substring (point) (+ (point) 6))
 424                      "Return"))
 425           (progn
 426             (search-forward ":")
 427             (forward-sexp 1)))
 428       (forward-line 1)
 429       (while (progn
 430                (forward-char 2)
 431                (if (= (following-char) ?\()
 432                    (forward-sexp 1)
 433                  (forward-sexp 2))
 434                (forward-line 1)
 435                (<= (point) opoint))
 436         (if (looking-at " *;;;")
 437             (forward-line 1))
 438         (setq count (1+ count)))
 439       count)))
 440
 441 (defun debugger-frame ()
 442   "Request entry to debugger when this frame exits.
 443 Applies to the frame whose line point is on in the backtrace."
 444   (interactive)
 445   (save-excursion
 446     (beginning-of-line)
 447     (if (looking-at " *;;;\\|[a-z]")
 448         (error "This line is not a function call")))
 449   (beginning-of-line)
 450   (backtrace-debug (debugger-frame-number) t)
 451   (if (= (following-char) ? )
 452       (let ((buffer-read-only nil))
 453         (delete-char 1)
 454         (insert ?*)))
 455   (beginning-of-line))
 456
 457 (defun debugger-frame-clear ()
 458   "Do not enter debugger when this frame exits.
 459 Applies to the frame whose line point is on in the backtrace."
 460   (interactive)
 461   (save-excursion
 462     (beginning-of-line)
 463     (if (looking-at " *;;;\\|[a-z]")
 464         (error "This line is not a function call")))
 465   (beginning-of-line)
 466   (backtrace-debug (debugger-frame-number) nil)
 467   (if (= (following-char) ?*)
 468       (let ((buffer-read-only nil))
 469         (delete-char 1)
 470         (insert ? )))
 471   (beginning-of-line))
 472
 473
 474
 475 (put 'debugger-env-macro 'lisp-indent-function 0)
 476 (defmacro debugger-env-macro (&rest body)
 477   "Run BODY in original environment."
 478   `(save-excursion
 479     (if (null (buffer-name debugger-old-buffer))
 480         ;; old buffer deleted
 481         (setq debugger-old-buffer (current-buffer)))
 482     (set-buffer debugger-old-buffer)
 483     (let ((load-read-function debugger-outer-load-read-function)
 484           (overriding-terminal-local-map
 485            debugger-outer-overriding-terminal-local-map)
 486           (overriding-local-map debugger-outer-overriding-local-map)
 487           (track-mouse debugger-outer-track-mouse)
 488           (last-command debugger-outer-last-command)
 489           (this-command debugger-outer-this-command)
 490           (unread-command-char debugger-outer-unread-command-char)
 491           (unread-command-events debugger-outer-unread-command-events)
 492           (unread-post-input-method-events
 493            debugger-outer-unread-post-input-method-events)
 494           (last-input-event debugger-outer-last-input-event)
 495           (last-command-event debugger-outer-last-command-event)
 496           (last-nonmenu-event debugger-outer-last-nonmenu-event)
 497           (last-event-frame debugger-outer-last-event-frame)
 498           (standard-input debugger-outer-standard-input)
 499           (standard-output debugger-outer-standard-output)
 500           (inhibit-redisplay debugger-outer-inhibit-redisplay)
 501           (cursor-in-echo-area debugger-outer-cursor-in-echo-area))
 502       (set-match-data debugger-outer-match-data)
 503       (prog1 (progn ,@body)
 504         (setq debugger-outer-match-data (match-data))
 505         (setq debugger-outer-load-read-function load-read-function)
 506         (setq debugger-outer-overriding-terminal-local-map
 507               overriding-terminal-local-map)
 508         (setq debugger-outer-overriding-local-map overriding-local-map)
 509         (setq debugger-outer-track-mouse track-mouse)
 510         (setq debugger-outer-last-command last-command)
 511         (setq debugger-outer-this-command this-command)
 512         (setq debugger-outer-unread-command-char unread-command-char)
 513         (setq debugger-outer-unread-command-events unread-command-events)
 514         (setq debugger-outer-unread-post-input-method-events
 515               unread-post-input-method-events)
 516         (setq debugger-outer-last-input-event last-input-event)
 517         (setq debugger-outer-last-command-event last-command-event)
 518         (setq debugger-outer-last-nonmenu-event last-nonmenu-event)
 519         (setq debugger-outer-last-event-frame last-event-frame)
 520         (setq debugger-outer-standard-input standard-input)
 521         (setq debugger-outer-standard-output standard-output)
 522         (setq debugger-outer-inhibit-redisplay inhibit-redisplay)
 523         (setq debugger-outer-cursor-in-echo-area cursor-in-echo-area)
 524         ))))
 525
 526 (defun debugger-eval-expression (exp)
 527   "Eval an expression, in an environment like that outside the debugger."
 528   (interactive
 529    (list (read-from-minibuffer "Eval: "
 530                                nil read-expression-map t
 531                                'read-expression-history)))
 532   (debugger-env-macro (eval-expression exp)))
 533 \f
 534 (defvar debugger-mode-map nil)
 535 (unless debugger-mode-map
 536   (let ((loop ? ))
 537     (setq debugger-mode-map (make-keymap))
 538     (set-keymap-parent debugger-mode-map button-buffer-map)
 539     (suppress-keymap debugger-mode-map)
 540     (define-key debugger-mode-map "-" 'negative-argument)
 541     (define-key debugger-mode-map "b" 'debugger-frame)
 542     (define-key debugger-mode-map "c" 'debugger-continue)
 543     (define-key debugger-mode-map "j" 'debugger-jump)
 544     (define-key debugger-mode-map "r" 'debugger-return-value)
 545     (define-key debugger-mode-map "u" 'debugger-frame-clear)
 546     (define-key debugger-mode-map "d" 'debugger-step-through)
 547     (define-key debugger-mode-map "l" 'debugger-list-functions)
 548     (define-key debugger-mode-map "h" 'describe-mode)
 549     (define-key debugger-mode-map "q" 'top-level)
 550     (define-key debugger-mode-map "e" 'debugger-eval-expression)
 551     (define-key debugger-mode-map " " 'next-line)
 552     (define-key debugger-mode-map "R" 'debugger-record-expression)
 553     (define-key debugger-mode-map "\C-m" 'help-follow)
 554     (define-key debugger-mode-map [mouse-2] 'push-button)
 555     ))
 556
 557
 558 (defcustom debugger-record-buffer "*Debugger-record*"
 559   "*Buffer name for expression values, for \\[debugger-record-expression]."
 560   :type 'string
 561   :group 'debugger
 562   :version "20.3")
 563
 564 (defun debugger-record-expression  (exp)
 565   "Display a variable's value and record it in `*Backtrace-record*' buffer."
 566   (interactive
 567    (list (read-from-minibuffer
 568           "Record Eval: "
 569           nil
 570           read-expression-map t
 571           'read-expression-history)))
 572   (let* ((buffer (get-buffer-create debugger-record-buffer))
 573          (standard-output buffer))
 574     (princ (format "Debugger Eval (%s): " exp))
 575     (princ (debugger-eval-expression exp))
 576     (terpri))
 577
 578   (with-current-buffer (get-buffer debugger-record-buffer)
 579     (save-excursion
 580       (forward-line -1)
 581       (message
 582        (buffer-substring (point) (progn (end-of-line) (point)))))))
 583
 584 (put 'debugger-mode 'mode-class 'special)
 585
 586 (defun debugger-mode ()
 587   "Mode for backtrace buffers, selected in debugger.
 588 \\<debugger-mode-map>
 589 A line starts with `*' if exiting that frame will call the debugger.
 590 Type \\[debugger-frame] or \\[debugger-frame-clear] to set or remove the `*'.
 591
 592 When in debugger due to frame being exited,
 593 use the \\[debugger-return-value] command to override the value
 594 being returned from that frame.
 595
 596 Use \\[debug-on-entry] and \\[cancel-debug-on-entry] to control
 597 which functions will enter the debugger when called.
 598
 599 Complete list of commands:
 600 \\{debugger-mode-map}"
 601   (kill-all-local-variables)
 602   (setq major-mode 'debugger-mode)
 603   (setq mode-name "Debugger")
 604   (setq truncate-lines t)
 605   (set-syntax-table emacs-lisp-mode-syntax-table)
 606   (use-local-map debugger-mode-map)
 607   (run-hooks 'debugger-mode-hook))
 608 \f
 609 ;;;###autoload
 610 (defun debug-on-entry (function)
 611   "Request FUNCTION to invoke debugger each time it is called.
 612 If you tell the debugger to continue, FUNCTION's execution proceeds.
 613 This works by modifying the definition of FUNCTION,
 614 which must be written in Lisp, not predefined.
 615 Use \\[cancel-debug-on-entry] to cancel the effect of this command.
 616 Redefining FUNCTION also cancels it."
 617   (interactive "aDebug on entry (to function): ")
 618   (debugger-reenable)
 619   ;; Handle a function that has been aliased to some other function.
 620   (if (and (subrp (symbol-function function))
 621            (eq (cdr (subr-arity (symbol-function function))) 'unevalled))
 622       (error "Function %s is a special form" function))
 623   (if (or (symbolp (symbol-function function))
 624           (subrp (symbol-function function)))
 625       ;; Create a wrapper in which we can then add the necessary debug call.
 626       (fset function `(lambda (&rest debug-on-entry-args)
 627                         ,(interactive-form (symbol-function function))
 628                         (apply ',(symbol-function function)
 629                                debug-on-entry-args))))
 630   (or (consp (symbol-function function))
 631       (debug-convert-byte-code function))
 632   (or (consp (symbol-function function))
 633       (error "Definition of %s is not a list" function))
 634   (fset function (debug-on-entry-1 function (symbol-function function) t))
 635   (or (memq function debug-function-list)
 636       (push function debug-function-list))
 637   function)
 638
 639 ;;;###autoload
 640 (defun cancel-debug-on-entry (&optional function)
 641   "Undo effect of \\[debug-on-entry] on FUNCTION.
 642 If argument is nil or an empty string, cancel for all functions."
 643   (interactive
 644    (list (let ((name
 645                 (completing-read "Cancel debug on entry (to function): "
 646                                  (mapcar 'symbol-name debug-function-list)
 647                                  nil t nil)))
 648            (if name (intern name)))))
 649   (debugger-reenable)
 650   (if (and function (not (string= function "")))
 651       (progn
 652         (let ((f (debug-on-entry-1 function (symbol-function function) nil)))
 653           (condition-case nil
 654               (if (and (equal (nth 1 f) '(&rest debug-on-entry-args))
 655                        (eq (car (nth 3 f)) 'apply))
 656                   ;; `f' is a wrapper introduced in debug-on-entry.
 657                   ;; Get rid of it since we don't need it any more.
 658                   (setq f (nth 1 (nth 1 (nth 3 f)))))
 659             (error nil))
 660           (fset function f))
 661         (setq debug-function-list (delq function debug-function-list))
 662         function)
 663     (message "Cancelling debug-on-entry for all functions")
 664     (mapcar 'cancel-debug-on-entry debug-function-list)))
 665
 666 (defun debug-convert-byte-code (function)
 667   (let ((defn (symbol-function function)))
 668     (if (not (consp defn))
 669         ;; Assume a compiled code object.
 670         (let* ((contents (append defn nil))
 671                (body
 672                 (list (list 'byte-code (nth 1 contents)
 673                             (nth 2 contents) (nth 3 contents)))))
 674           (if (nthcdr 5 contents)
 675               (setq body (cons (list 'interactive (nth 5 contents)) body)))
 676           (if (nth 4 contents)
 677               ;; Use `documentation' here, to get the actual string,
 678               ;; in case the compiled function has a reference
 679               ;; to the .elc file.
 680               (setq body (cons (documentation function) body)))
 681           (fset function (cons 'lambda (cons (car contents) body)))))))
 682
 683 (defun debug-on-entry-1 (function defn flag)
 684   (if (subrp defn)
 685       (error "%s is a built-in function" function)
 686     (if (eq (car defn) 'macro)
 687         (debug-on-entry-1 function (cdr defn) flag)
 688       (or (eq (car defn) 'lambda)
 689           (error "%s not user-defined Lisp function" function))
 690       (let ((tail (cddr defn)))
 691         ;; Skip the docstring.
 692         (if (stringp (car tail)) (setq tail (cdr tail)))
 693         ;; Skip the interactive form.
 694         (if (eq 'interactive (car-safe (car tail))) (setq tail (cdr tail)))
 695         (unless (eq flag (equal (car tail) '(debug 'debug)))
 696           ;; Add/remove debug statement as needed.
 697           (if (not flag)
 698               (progn (setcar tail (cadr tail))
 699                      (setcdr tail (cddr tail)))
 700             (setcdr tail (cons (car tail) (cdr tail)))
 701             (setcar tail '(debug 'debug))))
 702         defn))))
 703
 704 (defun debugger-list-functions ()
 705   "Display a list of all the functions now set to debug on entry."
 706   (interactive)
 707   (with-output-to-temp-buffer "*Help*"
 708     (if (null debug-function-list)
 709         (princ "No debug-on-entry functions now\n")
 710       (princ "Functions set to debug on entry:\n\n")
 711       (let ((list debug-function-list))
 712         (while list
 713           (prin1 (car list))
 714           (terpri)
 715           (setq list (cdr list))))
 716       (princ "Note: if you have redefined a function, then it may no longer\n")
 717       (princ "be set to debug on entry, even if it is in the list."))
 718     (save-excursion
 719       (set-buffer standard-output)
 720       (help-mode))))
 721
 722 (provide 'debug)
 723
 724 ;;; debug.el ends here