3 ;;;; This software is part of the SBCL system. See the README file for
6 ;;;; This software is derived from the CMU CL system, which was
7 ;;;; written at Carnegie Mellon University and released into the
8 ;;;; public domain. The software is in the public domain and is
9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
10 ;;;; files for more information.
12 (in-package "SB!DEBUG")
14 ;;;; variables and constants
16 ;;; things to consider when tweaking these values:
17 ;;; * We're afraid to just default them to NIL and NIL, in case the
18 ;;; user inadvertently causes a hairy data structure to be printed
19 ;;; when he inadvertently enters the debugger.
20 ;;; * We don't want to truncate output too much. These days anyone
21 ;;; can easily run their Lisp in a windowing system or under Emacs,
22 ;;; so it's not the end of the world even if the worst case is a
23 ;;; few thousand lines of output.
24 ;;; * As condition :REPORT methods are converted to use the pretty
25 ;;; printer, they acquire *PRINT-LEVEL* constraints, so e.g. under
26 ;;; sbcl-0.7.1.28's old value of *DEBUG-PRINT-LEVEL*=3, an
27 ;;; ARG-COUNT-ERROR printed as
28 ;;; error while parsing arguments to DESTRUCTURING-BIND:
29 ;;; invalid number of elements in
31 ;;; to satisfy lambda list
33 ;;; exactly 2 expected, but 5 found
34 (defvar *debug-print-variable-alist* nil
36 "an association list describing new bindings for special variables
37 to be used within the debugger. Eg.
39 ((*PRINT-LENGTH* . 10) (*PRINT-LEVEL* . 6) (*PRINT-PRETTY* . NIL))
41 The variables in the CAR positions are bound to the values in the CDR
42 during the execution of some debug commands. When evaluating arbitrary
43 expressions in the debugger, the normal values of the printer control
44 variables are in effect.
46 Initially empty, *DEBUG-PRINT-VARIABLE-ALIST* is typically used to
47 provide bindings for printer control variables.")
49 (defvar *debug-readtable*
50 ;; KLUDGE: This can't be initialized in a cold toplevel form,
51 ;; because the *STANDARD-READTABLE* isn't initialized until after
52 ;; cold toplevel forms have run. So instead we initialize it
53 ;; immediately after *STANDARD-READTABLE*. -- WHN 20000205
56 "*READTABLE* for the debugger")
58 (defvar *in-the-debugger* nil
60 "This is T while in the debugger.")
62 ;;; nestedness inside debugger command loops
63 (defvar *debug-command-level* 0)
65 ;;; If this is bound before the debugger is invoked, it is used as the
66 ;;; stack top by the debugger.
67 (defvar *stack-top-hint* nil)
69 (defvar *stack-top* nil)
70 (defvar *real-stack-top* nil)
72 (defvar *current-frame* nil)
74 ;;; Beginner-oriented help messages are important because you end up
75 ;;; in the debugger whenever something bad happens, or if you try to
76 ;;; get out of the system with Ctrl-C or (EXIT) or EXIT or whatever.
77 ;;; But after memorizing them the wasted screen space gets annoying..
78 (defvar *debug-beginner-help-p* t
79 "Should the debugger display beginner-oriented help messages?")
81 (defun debug-prompt (stream)
82 (sb!thread::get-foreground)
85 (sb!di:frame-number *current-frame*)
86 (> *debug-command-level* 1)
87 *debug-command-level*))
89 (defparameter *debug-help-string*
90 "The debug prompt is square brackets, with number(s) indicating the current
91 control stack level and, if you've entered the debugger recursively, how
92 deeply recursed you are.
93 Any command -- including the name of a restart -- may be uniquely abbreviated.
94 The debugger rebinds various special variables for controlling i/o, sometimes
95 to defaults (much like WITH-STANDARD-IO-SYNTAX does) and sometimes to
96 its own special values, based on SB-EXT:*DEBUG-PRINT-VARIBALE-ALIST*.
97 Debug commands do not affect *, //, and similar variables, but evaluation in
98 the debug loop does affect these variables.
99 SB-DEBUG:*FLUSH-DEBUG-ERRORS* controls whether errors at the debug prompt
100 drop you deeper into the debugger.
102 Getting in and out of the debugger:
103 RESTART invokes restart numbered as shown (prompt if not given).
104 ERROR prints the error condition and restart cases.
105 The number of any restart, or its name, or a unique abbreviation for its
106 name, is a valid command, and is the same as using RESTART to invoke
110 U up frame D down frame
111 B bottom frame F n frame n (n=0 for top frame)
114 BACKTRACE [n] shows n frames going down the stack.
115 LIST-LOCALS, L lists locals in current function.
116 PRINT, P displays current function call.
117 SOURCE [n] displays frame's source form with n levels of enclosing forms.
121 [EXPERIMENTAL] Selects the CONTINUE restart if one exists and starts
122 single-stepping. Single stepping affects only code compiled with
123 under high DEBUG optimization quality. See User Manul for details.
125 Function and macro commands:
127 Return the n'th argument in the current frame.
128 (SB-DEBUG:VAR string-or-symbol [id])
129 Returns the value of the specified variable in the current frame.
133 [EXPERIMENTAL] Return the values resulting from evaluation of expr
134 from the current frame, if this frame was compiled with a sufficiently
135 high DEBUG optimization quality.
137 Discard all pending input on *STANDARD-INPUT*. (This can be
138 useful when the debugger was invoked to handle an error in
139 deeply nested input syntax, and now the reader is confused.)")
142 ;;; If LOC is an unknown location, then try to find the block start
143 ;;; location. Used by source printing to some information instead of
144 ;;; none for the user.
145 (defun maybe-block-start-location (loc)
146 (if (sb!di:code-location-unknown-p loc)
147 (let* ((block (sb!di:code-location-debug-block loc))
148 (start (sb!di:do-debug-block-locations (loc block)
150 (cond ((and (not (sb!di:debug-block-elsewhere-p block))
152 ;; FIXME: Why output on T instead of *DEBUG-FOO* or something?
153 (format t "~%unknown location: using block start~%")
161 (defun backtrace (&optional (count most-positive-fixnum)
162 (*standard-output* *debug-io*))
164 "Show a listing of the call stack going down from the current frame. In the
165 debugger, the current frame is indicated by the prompt. COUNT is how many
167 (fresh-line *standard-output*)
168 (do ((frame (if *in-the-debugger* *current-frame* (sb!di:top-frame))
169 (sb!di:frame-down frame))
170 (count count (1- count)))
171 ((or (null frame) (zerop count)))
172 (print-frame-call frame :number t))
173 (fresh-line *standard-output*)
176 (defun backtrace-as-list (&optional (count most-positive-fixnum))
177 #!+sb-doc "Return a list representing the current BACKTRACE."
178 (do ((reversed-result nil)
179 (frame (if *in-the-debugger* *current-frame* (sb!di:top-frame))
180 (sb!di:frame-down frame))
181 (count count (1- count)))
182 ((or (null frame) (zerop count))
183 (nreverse reversed-result))
184 (push (frame-call-as-list frame) reversed-result)))
186 (defun frame-call-as-list (frame)
187 (cons (sb!di:debug-fun-name (sb!di:frame-debug-fun frame))
188 (frame-args-as-list frame)))
192 (eval-when (:compile-toplevel :execute)
194 ;;; This is a convenient way to express what to do for each type of
195 ;;; lambda-list element.
196 (sb!xc:defmacro lambda-list-element-dispatch (element
207 (ecase (car ,element)
208 (:optional ,@optional)
210 (:keyword ,@keyword)))
212 (aver (eq ,element :deleted))
215 (sb!xc:defmacro lambda-var-dispatch (variable location deleted valid other)
216 (let ((var (gensym)))
217 `(let ((,var ,variable))
218 (cond ((eq ,var :deleted) ,deleted)
219 ((eq (sb!di:debug-var-validity ,var ,location) :valid)
225 ;;; This is used in constructing arg lists for debugger printing when
226 ;;; the arg list is unavailable, some arg is unavailable or unused, etc.
227 (defstruct (unprintable-object
228 (:constructor make-unprintable-object (string))
229 (:print-object (lambda (x s)
230 (print-unreadable-object (x s)
231 (write-string (unprintable-object-string x)
236 ;;; Extract the function argument values for a debug frame.
237 (defun frame-args-as-list (frame)
238 (let ((debug-fun (sb!di:frame-debug-fun frame))
239 (loc (sb!di:frame-code-location frame))
240 (reversed-result nil))
243 (dolist (ele (sb!di:debug-fun-lambda-list debug-fun))
244 (lambda-list-element-dispatch ele
245 :required ((push (frame-call-arg ele loc frame) reversed-result))
246 :optional ((push (frame-call-arg (second ele) loc frame)
248 :keyword ((push (second ele) reversed-result)
249 (push (frame-call-arg (third ele) loc frame)
251 :deleted ((push (frame-call-arg ele loc frame) reversed-result))
252 :rest ((lambda-var-dispatch (second ele) loc
255 (setf reversed-result
256 (append (reverse (sb!di:debug-var-value
260 (push (make-unprintable-object
261 "unavailable &REST argument")
263 ;; As long as we do an ordinary return (as opposed to SIGNALing
264 ;; a CONDITION) from the DOLIST above:
265 (nreverse reversed-result))
266 (sb!di:lambda-list-unavailable
268 (make-unprintable-object "unavailable lambda list")))))
270 ;;; Print FRAME with verbosity level 1. If we hit a &REST arg, then
271 ;;; print as many of the values as possible, punting the loop over
272 ;;; lambda-list variables since any other arguments will be in the
273 ;;; &REST arg's list of values.
274 (defun print-frame-call-1 (frame)
275 (let ((debug-fun (sb!di:frame-debug-fun frame)))
277 (pprint-logical-block (*standard-output* nil :prefix "(" :suffix ")")
278 (let ((args (ensure-printable-object (frame-args-as-list frame))))
279 ;; Since we go to some trouble to make nice informative function
280 ;; names like (PRINT-OBJECT :AROUND (CLOWN T)), let's make sure
281 ;; that they aren't truncated by *PRINT-LENGTH* and *PRINT-LEVEL*.
282 (let ((*print-length* nil)
284 (prin1 (ensure-printable-object (sb!di:debug-fun-name debug-fun))))
285 ;; For the function arguments, we can just print normally.
287 (format t "~{ ~_~S~}" args)
288 (format t " ~S" args))))
290 (when (sb!di:debug-fun-kind debug-fun)
292 (prin1 (sb!di:debug-fun-kind debug-fun))
295 (defun ensure-printable-object (object)
297 (with-open-stream (out (make-broadcast-stream))
301 (declare (ignore cond))
302 (make-unprintable-object "error printing object"))))
304 (defun frame-call-arg (var location frame)
305 (lambda-var-dispatch var location
306 (make-unprintable-object "unused argument")
307 (sb!di:debug-var-value var frame)
308 (make-unprintable-object "unavailable argument")))
310 ;;; Prints a representation of the function call causing FRAME to
311 ;;; exist. VERBOSITY indicates the level of information to output;
312 ;;; zero indicates just printing the DEBUG-FUN's name, and one
313 ;;; indicates displaying call-like, one-liner format with argument
315 (defun print-frame-call (frame &key (verbosity 1) (number nil))
319 (format t "~&~S: " (sb!di:frame-number frame)))
320 (format t "~S" frame))
323 (format t "~&~S: " (sb!di:frame-number frame)))
324 (print-frame-call-1 frame)))
325 (when (>= verbosity 2)
326 (let ((loc (sb!di:frame-code-location frame)))
329 (sb!di:code-location-debug-block loc)
330 (format t "~%source: ")
331 (print-code-location-source-form loc 0))
332 (sb!di:debug-condition (ignore) ignore)
333 (error (c) (format t "error finding source: ~A" c))))))
337 (defvar *debugger-hook* nil
339 "This is either NIL or a function of two arguments, a condition and the value
340 of *DEBUGGER-HOOK*. This function can either handle the condition or return
341 which causes the standard debugger to execute. The system passes the value
342 of this variable to the function because it binds *DEBUGGER-HOOK* to NIL
343 around the invocation.")
345 (defvar *invoke-debugger-hook* nil
347 "This is either NIL or a designator for a function of two arguments,
348 to be run when the debugger is about to be entered. The function is
349 run with *INVOKE-DEBUGGER-HOOK* bound to NIL to minimize recursive
350 errors, and receives as arguments the condition that triggered
351 debugger entry and the previous value of *INVOKE-DEBUGGER-HOOK*
353 This mechanism is an SBCL extension similar to the standard *DEBUGGER-HOOK*.
354 In contrast to *DEBUGGER-HOOK*, it is observed by INVOKE-DEBUGGER even when
357 ;;; These are bound on each invocation of INVOKE-DEBUGGER.
358 (defvar *debug-restarts*)
359 (defvar *debug-condition*)
360 (defvar *nested-debug-condition*)
362 ;;; Oh, what a tangled web we weave when we preserve backwards
363 ;;; compatibility with 1968-style use of global variables to control
364 ;;; per-stream i/o properties; there's really no way to get this
365 ;;; quite right, but we do what we can.
366 (defun funcall-with-debug-io-syntax (fun &rest rest)
367 (declare (type function fun))
368 ;; Try to force the other special variables into a useful state.
369 (let (;; Protect from WITH-STANDARD-IO-SYNTAX some variables where
370 ;; any default we might use is less useful than just reusing
371 ;; the global values.
372 (original-package *package*)
373 (original-print-pretty *print-pretty*))
374 (with-standard-io-syntax
376 (let (;; We want the printer and reader to be in a useful
377 ;; state, regardless of where the debugger was invoked
378 ;; in the program. WITH-STANDARD-IO-SYNTAX and
379 ;; WITH-SANE-IO-SYNTAX do much of what we want, but
380 ;; * It doesn't affect our internal special variables
381 ;; like *CURRENT-LEVEL-IN-PRINT*.
382 ;; * It isn't customizable.
383 ;; * It sets *PACKAGE* to COMMON-LISP-USER, which is not
384 ;; helpful behavior for a debugger.
385 ;; * There's no particularly good debugger default for
386 ;; *PRINT-PRETTY*, since T is usually what you want
387 ;; -- except absolutely not what you want when you're
388 ;; debugging failures in PRINT-OBJECT logic.
389 ;; We try to address all these issues with explicit
391 (sb!kernel:*current-level-in-print* 0)
392 (*package* original-package)
393 (*print-pretty* original-print-pretty)
394 ;; Clear the circularity machinery to try to to reduce the
395 ;; pain from sharing the circularity table across all
396 ;; streams; if these are not rebound here, then setting
397 ;; *PRINT-CIRCLE* within the debugger when debugging in a
398 ;; state where something circular was being printed (e.g.,
399 ;; because the debugger was entered on an error in a
400 ;; PRINT-OBJECT method) makes a hopeless mess. Binding them
401 ;; here does seem somewhat ugly because it makes it more
402 ;; difficult to debug the printing-of-circularities code
403 ;; itself; however, as far as I (WHN, 2004-05-29) can see,
404 ;; that's almost entirely academic as long as there's one
405 ;; shared *C-H-T* for all streams (i.e., it's already
406 ;; unreasonably difficult to debug print-circle machinery
407 ;; given the buggy crosstalk between the debugger streams
408 ;; and the stream you're trying to watch), and any fix for
409 ;; that buggy arrangement will likely let this hack go away
411 (sb!impl::*circularity-hash-table* . nil)
412 (sb!impl::*circularity-counter* . nil)
413 (*readtable* *debug-readtable*))
415 ;; (Why NREVERSE? PROGV makes the later entries have
416 ;; precedence over the earlier entries.
417 ;; *DEBUG-PRINT-VARIABLE-ALIST* is called an alist, so it's
418 ;; expected that its earlier entries have precedence. And
419 ;; the earlier-has-precedence behavior is mostly more
420 ;; convenient, so that programmers can use PUSH or LIST* to
421 ;; customize *DEBUG-PRINT-VARIABLE-ALIST*.)
422 (nreverse (mapcar #'car *debug-print-variable-alist*))
423 (nreverse (mapcar #'cdr *debug-print-variable-alist*))
424 (apply fun rest)))))))
426 ;;; the ordinary ANSI case of INVOKE-DEBUGGER, when not suppressed by
427 ;;; command-line --disable-debugger option
428 (defun invoke-debugger (condition)
430 "Enter the debugger."
432 (let ((old-hook *debugger-hook*))
434 (let ((*debugger-hook* nil))
435 (funcall old-hook condition old-hook))))
436 (let ((old-hook *invoke-debugger-hook*))
438 (let ((*invoke-debugger-hook* nil))
439 (funcall old-hook condition old-hook))))
441 ;; Note: CMU CL had (SB-UNIX:UNIX-SIGSETMASK 0) here, to reset the
442 ;; signal state in the case that we wind up in the debugger as a
443 ;; result of something done by a signal handler. It's not
444 ;; altogether obvious that this is necessary, and indeed SBCL has
445 ;; not been doing it since 0.7.8.5. But nobody seems altogether
447 ;; -- dan 2003.11.11, based on earlier comment of WHN 2002-09-28
449 ;; We definitely want *PACKAGE* to be of valid type.
451 ;; Elsewhere in the system, we use the SANE-PACKAGE function for
452 ;; this, but here causing an exception just as we're trying to handle
453 ;; an exception would be confusing, so instead we use a special hack.
454 (unless (and (packagep *package*)
455 (package-name *package*))
456 (setf *package* (find-package :cl-user))
457 (format *error-output*
458 "The value of ~S was not an undeleted PACKAGE. It has been
460 '*package* *package*))
462 ;; Before we start our own output, finish any pending output.
463 ;; Otherwise, if the user tried to track the progress of his program
464 ;; using PRINT statements, he'd tend to lose the last line of output
465 ;; or so, which'd be confusing.
466 (flush-standard-output-streams)
468 (funcall-with-debug-io-syntax #'%invoke-debugger condition))
470 (defun %invoke-debugger (condition)
472 (let ((*debug-condition* condition)
473 (*debug-restarts* (compute-restarts condition))
474 (*nested-debug-condition* nil))
476 ;; (The initial output here goes to *ERROR-OUTPUT*, because the
477 ;; initial output is not interactive, just an error message, and
478 ;; when people redirect *ERROR-OUTPUT*, they could reasonably
479 ;; expect to see error messages logged there, regardless of what
480 ;; the debugger does afterwards.)
481 (format *error-output*
482 "~2&~@<debugger invoked on a ~S in thread ~A: ~
484 (type-of *debug-condition*)
485 (sb!thread:current-thread-id)
488 (setf *nested-debug-condition* condition)
489 (let ((ndc-type (type-of *nested-debug-condition*)))
490 (format *error-output*
491 "~&~@<(A ~S was caught when trying to print ~S when ~
492 entering the debugger. Printing was aborted and the ~
493 ~S was stored in ~S.)~@:>~%"
497 '*nested-debug-condition*))
498 (when (typep condition 'cell-error)
499 ;; what we really want to know when it's e.g. an UNBOUND-VARIABLE:
500 (format *error-output*
501 "~&(CELL-ERROR-NAME ~S) = ~S~%"
503 (cell-error-name *debug-condition*)))))
505 (let ((background-p (sb!thread::debugger-wait-until-foreground-thread
508 ;; After the initial error/condition/whatever announcement to
509 ;; *ERROR-OUTPUT*, we become interactive, and should talk on
510 ;; *DEBUG-IO* from now on. (KLUDGE: This is a normative
511 ;; statement, not a description of reality.:-| There's a lot of
512 ;; older debugger code which was written to do i/o on whatever
513 ;; stream was in fashion at the time, and not all of it has
514 ;; been converted to behave this way. -- WHN 2000-11-16)
517 (let (;; FIXME: Rebinding *STANDARD-OUTPUT* here seems wrong,
518 ;; violating the principle of least surprise, and making
519 ;; it impossible for the user to do reasonable things
520 ;; like using PRINT at the debugger prompt to send output
521 ;; to the program's ordinary (possibly
522 ;; redirected-to-a-file) *STANDARD-OUTPUT*. (CMU CL
523 ;; used to rebind *STANDARD-INPUT* here too, but that's
524 ;; been fixed already.)
525 (*standard-output* *debug-io*)
526 ;; This seems reasonable: e.g. if the user has redirected
527 ;; *ERROR-OUTPUT* to some log file, it's probably wrong
528 ;; to send errors which occur in interactive debugging to
529 ;; that file, and right to send them to *DEBUG-IO*.
530 (*error-output* *debug-io*))
531 (unless (typep condition 'step-condition)
532 (when *debug-beginner-help-p*
534 "~%~@<You can type HELP for debugger help, or ~
535 (SB-EXT:QUIT) to exit from SBCL.~:@>~2%"))
536 (show-restarts *debug-restarts* *debug-io*))
539 (sb!thread::release-foreground))))))
541 ;;; this function is for use in *INVOKE-DEBUGGER-HOOK* when ordinary
542 ;;; ANSI behavior has been suppressed by the "--disable-debugger"
543 ;;; command-line option
544 (defun debugger-disabled-hook (condition me)
545 (declare (ignore me))
546 ;; There is no one there to interact with, so report the
547 ;; condition and terminate the program.
548 (flet ((failure-quit (&key recklessly-p)
549 (/show0 "in FAILURE-QUIT (in --disable-debugger debugger hook)")
550 (quit :unix-status 1 :recklessly-p recklessly-p)))
551 ;; This HANDLER-CASE is here mostly to stop output immediately
552 ;; (and fall through to QUIT) when there's an I/O error. Thus,
553 ;; when we're run under a shell script or something, we can die
554 ;; cleanly when the script dies (and our pipes are cut), instead
555 ;; of falling into ldb or something messy like that. Similarly, we
556 ;; can terminate cleanly even if BACKTRACE dies because of bugs in
557 ;; user PRINT-OBJECT methods.
560 (format *error-output*
561 "~&~@<unhandled ~S in thread ~S: ~2I~_~A~:>~2%"
563 (sb!thread:current-thread-id)
565 ;; Flush *ERROR-OUTPUT* even before the BACKTRACE, so that
566 ;; even if we hit an error within BACKTRACE (e.g. a bug in
567 ;; the debugger's own frame-walking code, or a bug in a user
568 ;; PRINT-OBJECT method) we'll at least have the CONDITION
569 ;; printed out before we die.
570 (finish-output *error-output*)
571 ;; (Where to truncate the BACKTRACE is of course arbitrary, but
572 ;; it seems as though we should at least truncate it somewhere.)
573 (sb!debug:backtrace 128 *error-output*)
576 "~%unhandled condition in --disable-debugger mode, quitting~%")
577 (finish-output *error-output*)
580 ;; We IGNORE-ERRORS here because even %PRIMITIVE PRINT can
581 ;; fail when our output streams are blown away, as e.g. when
582 ;; we're running under a Unix shell script and it dies somehow
583 ;; (e.g. because of a SIGINT). In that case, we might as well
584 ;; just give it up for a bad job, and stop trying to notify
585 ;; the user of anything.
587 ;; Actually, the only way I've run across to exercise the
588 ;; problem is to have more than one layer of shell script.
589 ;; I have a shell script which does
590 ;; time nice -10 sh make.sh "$1" 2>&1 | tee make.tmp
591 ;; and the problem occurs when I interrupt this with Ctrl-C
592 ;; under Linux 2.2.14-5.0 and GNU bash, version 1.14.7(1).
593 ;; I haven't figured out whether it's bash, time, tee, Linux, or
594 ;; what that is responsible, but that it's possible at all
595 ;; means that we should IGNORE-ERRORS here. -- WHN 2001-04-24
598 "Argh! error within --disable-debugger error handling"))
599 (failure-quit :recklessly-p t)))))
601 ;;; halt-on-failures and prompt-on-failures modes, suitable for
602 ;;; noninteractive and interactive use respectively
603 (defun disable-debugger ()
604 (when (eql *invoke-debugger-hook* nil)
605 (setf *debug-io* *error-output*
606 *invoke-debugger-hook* 'debugger-disabled-hook)))
608 (defun enable-debugger ()
609 (when (eql *invoke-debugger-hook* 'debugger-disabled-hook)
610 (setf *invoke-debugger-hook* nil)))
612 (setf *debug-io* *query-io*)
614 (defun show-restarts (restarts s)
615 (cond ((null restarts)
617 "~&(no restarts: If you didn't do this on purpose, ~
618 please report it as a bug.)~%"))
620 (format s "~&restarts (invokable by number or by ~
621 possibly-abbreviated name):~%")
625 (dolist (restart restarts)
626 (let ((name (restart-name restart)))
628 (let ((len (length (princ-to-string name))))
629 (when (> len max-name-len)
630 (setf max-name-len len))))))
631 (unless (zerop max-name-len)
632 (incf max-name-len 3))
633 (dolist (restart restarts)
634 (let ((name (restart-name restart)))
635 (cond ((member name names-used)
636 (format s "~& ~2D: ~V@T~A~%" count max-name-len restart))
638 (format s "~& ~2D: [~VA] ~A~%"
639 count (- max-name-len 3) name restart)
640 (push name names-used))))
643 (defvar *debug-loop-fun* #'debug-loop-fun
644 "a function taking no parameters that starts the low-level debug loop")
646 ;;; This calls DEBUG-LOOP, performing some simple initializations
647 ;;; before doing so. INVOKE-DEBUGGER calls this to actually get into
648 ;;; the debugger. SB!KERNEL::ERROR-ERROR calls this in emergencies
649 ;;; to get into a debug prompt as quickly as possible with as little
650 ;;; risk as possible for stepping on whatever is causing recursive
652 (defun internal-debug ()
653 (let ((*in-the-debugger* t)
654 (*read-suppress* nil))
655 (unless (typep *debug-condition* 'step-condition)
656 (clear-input *debug-io*))
657 (funcall *debug-loop-fun*)))
661 ;;; Note: This defaulted to T in CMU CL. The changed default in SBCL
662 ;;; was motivated by desire to play nicely with ILISP.
663 (defvar *flush-debug-errors* nil
665 "When set, avoid calling INVOKE-DEBUGGER recursively when errors occur while
666 executing in the debugger.")
668 (defun debug-loop-fun ()
669 (let* ((*debug-command-level* (1+ *debug-command-level*))
670 (*real-stack-top* (sb!di:top-frame))
671 (*stack-top* (or *stack-top-hint* *real-stack-top*))
672 (*stack-top-hint* nil)
673 (*current-frame* *stack-top*))
674 (handler-bind ((sb!di:debug-condition
676 (princ condition *debug-io*)
677 (/show0 "handling d-c by THROWing DEBUG-LOOP-CATCHER")
678 (throw 'debug-loop-catcher nil))))
680 (print-frame-call *current-frame* :verbosity 2)
682 (catch 'debug-loop-catcher
683 (handler-bind ((error (lambda (condition)
684 (when *flush-debug-errors*
685 (clear-input *debug-io*)
687 ;; FIXME: Doing input on *DEBUG-IO*
688 ;; and output on T seems broken.
690 "~&error flushed (because ~
692 '*flush-debug-errors*)
693 (/show0 "throwing DEBUG-LOOP-CATCHER")
694 (throw 'debug-loop-catcher nil)))))
695 ;; We have to bind LEVEL for the restart function created by
696 ;; WITH-SIMPLE-RESTART.
697 (let ((level *debug-command-level*)
698 (restart-commands (make-restart-commands)))
699 (with-simple-restart (abort
700 "~@<Reduce debugger level (to debug level ~W).~@:>"
702 (debug-prompt *debug-io*)
703 (force-output *debug-io*)
704 (let* ((exp (read *debug-io*))
705 (cmd-fun (debug-command-p exp restart-commands)))
707 (debug-eval-print exp))
709 (format t "~&Your command, ~S, is ambiguous:~%"
711 (dolist (ele cmd-fun)
712 (format t " ~A~%" ele)))
714 (funcall cmd-fun))))))))))))
716 ;;; FIXME: We could probably use INTERACTIVE-EVAL for much of this logic.
717 (defun debug-eval-print (expr)
718 (/noshow "entering DEBUG-EVAL-PRINT" expr)
719 (/noshow (fboundp 'compile))
720 (setq +++ ++ ++ + + - - expr)
721 (let* ((values (multiple-value-list (eval -)))
722 (*standard-output* *debug-io*))
723 (/noshow "done with EVAL in DEBUG-EVAL-PRINT")
725 (if values (prin1 (car values)))
726 (dolist (x (cdr values))
729 (setq /// // // / / values)
730 (setq *** ** ** * * (car values))
731 ;; Make sure that nobody passes back an unbound marker.
735 ;; FIXME: The way INTERACTIVE-EVAL does this seems better.
736 (princ "Setting * to NIL (was unbound marker)."))))
738 ;;;; debug loop functions
740 ;;; These commands are functions, not really commands, so that users
741 ;;; can get their hands on the values returned.
743 (eval-when (:execute :compile-toplevel)
745 (sb!xc:defmacro define-var-operation (ref-or-set &optional value-var)
746 `(let* ((temp (etypecase name
747 (symbol (sb!di:debug-fun-symbol-vars
748 (sb!di:frame-debug-fun *current-frame*)
750 (simple-string (sb!di:ambiguous-debug-vars
751 (sb!di:frame-debug-fun *current-frame*)
753 (location (sb!di:frame-code-location *current-frame*))
754 ;; Let's only deal with valid variables.
755 (vars (remove-if-not (lambda (v)
756 (eq (sb!di:debug-var-validity v location)
759 (declare (list vars))
761 (error "No known valid variables match ~S." name))
765 '(sb!di:debug-var-value (car vars) *current-frame*))
767 `(setf (sb!di:debug-var-value (car vars) *current-frame*)
770 ;; Since we have more than one, first see whether we have
771 ;; any variables that exactly match the specification.
772 (let* ((name (etypecase name
773 (symbol (symbol-name name))
774 (simple-string name)))
775 ;; FIXME: REMOVE-IF-NOT is deprecated, use STRING/=
777 (exact (remove-if-not (lambda (v)
778 (string= (sb!di:debug-var-symbol-name v)
781 (vars (or exact vars)))
782 (declare (simple-string name)
785 ;; Check now for only having one variable.
789 '(sb!di:debug-var-value (car vars) *current-frame*))
791 `(setf (sb!di:debug-var-value (car vars) *current-frame*)
793 ;; If there weren't any exact matches, flame about
794 ;; ambiguity unless all the variables have the same
799 (string= (sb!di:debug-var-symbol-name v)
800 (sb!di:debug-var-symbol-name (car vars))))
802 (error "specification ambiguous:~%~{ ~A~%~}"
803 (mapcar #'sb!di:debug-var-symbol-name
806 :key #'sb!di:debug-var-symbol-name))))
807 ;; All names are the same, so see whether the user
808 ;; ID'ed one of them.
810 (let ((v (find id vars :key #'sb!di:debug-var-id)))
813 "invalid variable ID, ~W: should have been one of ~S"
815 (mapcar #'sb!di:debug-var-id vars)))
818 '(sb!di:debug-var-value v *current-frame*))
820 `(setf (sb!di:debug-var-value v *current-frame*)
823 (error "Specify variable ID to disambiguate ~S. Use one of ~S."
825 (mapcar #'sb!di:debug-var-id vars)))))))))
829 ;;; FIXME: This doesn't work. It would be real nice we could make it
830 ;;; work! Alas, it doesn't seem to work in CMU CL X86 either..
831 (defun var (name &optional (id 0 id-supplied))
833 "Return a variable's value if possible. NAME is a simple-string or symbol.
834 If it is a simple-string, it is an initial substring of the variable's name.
835 If name is a symbol, it has the same name and package as the variable whose
836 value this function returns. If the symbol is uninterned, then the variable
837 has the same name as the symbol, but it has no package.
839 If name is the initial substring of variables with different names, then
840 this return no values after displaying the ambiguous names. If name
841 determines multiple variables with the same name, then you must use the
842 optional id argument to specify which one you want. If you left id
843 unspecified, then this returns no values after displaying the distinguishing
846 The result of this function is limited to the availability of variable
847 information. This is SETF'able."
848 (define-var-operation :ref))
849 (defun (setf var) (value name &optional (id 0 id-supplied))
850 (define-var-operation :set value))
852 ;;; This returns the COUNT'th arg as the user sees it from args, the
853 ;;; result of SB!DI:DEBUG-FUN-LAMBDA-LIST. If this returns a
854 ;;; potential DEBUG-VAR from the lambda-list, then the second value is
855 ;;; T. If this returns a keyword symbol or a value from a rest arg,
856 ;;; then the second value is NIL.
858 ;;; FIXME: There's probably some way to merge the code here with
859 ;;; FRAME-ARGS-AS-LIST. (A fair amount of logic is already shared
860 ;;; through LAMBDA-LIST-ELEMENT-DISPATCH, but I suspect more could be.)
861 (declaim (ftype (function (index list)) nth-arg))
862 (defun nth-arg (count args)
864 (dolist (ele args (error "The argument specification ~S is out of range."
866 (lambda-list-element-dispatch ele
867 :required ((if (zerop n) (return (values ele t))))
868 :optional ((if (zerop n) (return (values (second ele) t))))
869 :keyword ((cond ((zerop n)
870 (return (values (second ele) nil)))
872 (return (values (third ele) t)))))
873 :deleted ((if (zerop n) (return (values ele t))))
874 :rest ((let ((var (second ele)))
875 (lambda-var-dispatch var (sb!di:frame-code-location
877 (error "unused &REST argument before n'th argument")
879 (sb!di:debug-var-value var *current-frame*)
881 "The argument specification ~S is out of range."
884 (return-from nth-arg (values value nil))
886 (error "invalid &REST argument before n'th argument")))))
891 "Return the N'th argument's value if possible. Argument zero is the first
892 argument in a frame's default printed representation. Count keyword/value
893 pairs as separate arguments."
894 (multiple-value-bind (var lambda-var-p)
895 (nth-arg n (handler-case (sb!di:debug-fun-lambda-list
896 (sb!di:frame-debug-fun *current-frame*))
897 (sb!di:lambda-list-unavailable ()
898 (error "No argument values are available."))))
900 (lambda-var-dispatch var (sb!di:frame-code-location *current-frame*)
901 (error "Unused arguments have no values.")
902 (sb!di:debug-var-value var *current-frame*)
903 (error "invalid argument value"))
906 ;;;; machinery for definition of debug loop commands
908 (defvar *debug-commands* nil)
910 ;;; Interface to *DEBUG-COMMANDS*. No required arguments in args are
912 (defmacro !def-debug-command (name args &rest body)
913 (let ((fun-name (symbolicate name "-DEBUG-COMMAND")))
915 (setf *debug-commands*
916 (remove ,name *debug-commands* :key #'car :test #'string=))
917 (defun ,fun-name ,args
918 (unless *in-the-debugger*
919 (error "invoking debugger command while outside the debugger"))
921 (push (cons ,name #',fun-name) *debug-commands*)
924 (defun !def-debug-command-alias (new-name existing-name)
925 (let ((pair (assoc existing-name *debug-commands* :test #'string=)))
926 (unless pair (error "unknown debug command name: ~S" existing-name))
927 (push (cons new-name (cdr pair)) *debug-commands*))
930 ;;; This takes a symbol and uses its name to find a debugger command,
931 ;;; using initial substring matching. It returns the command function
932 ;;; if form identifies only one command, but if form is ambiguous,
933 ;;; this returns a list of the command names. If there are no matches,
934 ;;; this returns nil. Whenever the loop that looks for a set of
935 ;;; possibilities encounters an exact name match, we return that
936 ;;; command function immediately.
937 (defun debug-command-p (form &optional other-commands)
938 (if (or (symbolp form) (integerp form))
942 (format nil "~W" form)))
945 (declare (simple-string name)
949 ;; Find matching commands, punting if exact match.
950 (flet ((match-command (ele)
951 (let* ((str (car ele))
952 (str-len (length str)))
953 (declare (simple-string str)
955 (cond ((< str-len len))
957 (when (string= name str :end1 len :end2 len)
958 (return-from debug-command-p (cdr ele))))
959 ((string= name str :end1 len :end2 len)
961 (mapc #'match-command *debug-commands*)
962 (mapc #'match-command other-commands))
964 ;; Return the right value.
965 (cond ((not res) nil)
968 (t ; Just return the names.
969 (do ((cmds res (cdr cmds)))
971 (setf (car cmds) (caar cmds))))))))
973 ;;; Return a list of debug commands (in the same format as
974 ;;; *DEBUG-COMMANDS*) that invoke each active restart.
976 ;;; Two commands are made for each restart: one for the number, and
977 ;;; one for the restart name (unless it's been shadowed by an earlier
978 ;;; restart of the same name, or it is NIL).
979 (defun make-restart-commands (&optional (restarts *debug-restarts*))
981 (num 0)) ; better be the same as show-restarts!
982 (dolist (restart restarts)
983 (let ((name (string (restart-name restart))))
986 (/show0 "in restart-command closure, about to i-r-i")
987 (invoke-restart-interactively restart))))
988 (push (cons (prin1-to-string num) restart-fun) commands)
989 (unless (or (null (restart-name restart))
990 (find name commands :key #'car :test #'string=))
991 (push (cons name restart-fun) commands))))
995 ;;;; frame-changing commands
997 (!def-debug-command "UP" ()
998 (let ((next (sb!di:frame-up *current-frame*)))
1000 (setf *current-frame* next)
1001 (print-frame-call next))
1003 (format t "~&Top of stack.")))))
1005 (!def-debug-command "DOWN" ()
1006 (let ((next (sb!di:frame-down *current-frame*)))
1008 (setf *current-frame* next)
1009 (print-frame-call next))
1011 (format t "~&Bottom of stack.")))))
1013 (!def-debug-command-alias "D" "DOWN")
1015 ;;; CMU CL had this command, but SBCL doesn't, since it's redundant
1016 ;;; with "FRAME 0", and it interferes with abbreviations for the
1017 ;;; TOPLEVEL restart.
1018 ;;;(!def-debug-command "TOP" ()
1019 ;;; (do ((prev *current-frame* lead)
1020 ;;; (lead (sb!di:frame-up *current-frame*) (sb!di:frame-up lead)))
1022 ;;; (setf *current-frame* prev)
1023 ;;; (print-frame-call prev))))
1025 (!def-debug-command "BOTTOM" ()
1026 (do ((prev *current-frame* lead)
1027 (lead (sb!di:frame-down *current-frame*) (sb!di:frame-down lead)))
1029 (setf *current-frame* prev)
1030 (print-frame-call prev))))
1032 (!def-debug-command-alias "B" "BOTTOM")
1034 (!def-debug-command "FRAME" (&optional
1035 (n (read-prompting-maybe "frame number: ")))
1036 (setf *current-frame*
1037 (multiple-value-bind (next-frame-fun limit-string)
1038 (if (< n (sb!di:frame-number *current-frame*))
1039 (values #'sb!di:frame-up "top")
1040 (values #'sb!di:frame-down "bottom"))
1041 (do ((frame *current-frame*))
1042 ((= n (sb!di:frame-number frame))
1044 (let ((next-frame (funcall next-frame-fun frame)))
1046 (setf frame next-frame))
1049 "The ~A of the stack was encountered.~%"
1051 (return frame)))))))
1052 (print-frame-call *current-frame*))
1054 (!def-debug-command-alias "F" "FRAME")
1056 ;;;; commands for entering and leaving the debugger
1058 ;;; CMU CL supported this QUIT debug command, but SBCL provides this
1059 ;;; functionality with a restart instead. (The QUIT debug command was
1060 ;;; removed because it's confusing to have "quit" mean two different
1061 ;;; things in the system, "restart the top level REPL" in the debugger
1062 ;;; and "terminate the Lisp system" as the SB-EXT:QUIT function.)
1064 ;;;(!def-debug-command "QUIT" ()
1065 ;;; (throw 'sb!impl::toplevel-catcher nil))
1067 ;;; CMU CL supported this GO debug command, but SBCL doesn't -- in
1068 ;;; SBCL you just type the CONTINUE restart name instead (or "C" or
1069 ;;; "RESTART CONTINUE", that's OK too).
1070 ;;;(!def-debug-command "GO" ()
1071 ;;; (continue *debug-condition*)
1072 ;;; (error "There is no restart named CONTINUE."))
1074 (!def-debug-command "RESTART" ()
1075 (/show0 "doing RESTART debug-command")
1076 (let ((num (read-if-available :prompt)))
1077 (when (eq num :prompt)
1078 (show-restarts *debug-restarts* *debug-io*)
1079 (write-string "restart: ")
1081 (setf num (read *debug-io*)))
1082 (let ((restart (typecase num
1084 (nth num *debug-restarts*))
1086 (find num *debug-restarts* :key #'restart-name
1087 :test (lambda (sym1 sym2)
1088 (string= (symbol-name sym1)
1089 (symbol-name sym2)))))
1091 (format t "~S is invalid as a restart name.~%" num)
1092 (return-from restart-debug-command nil)))))
1093 (/show0 "got RESTART")
1095 (invoke-restart-interactively restart)
1096 ;; FIXME: Even if this isn't handled by WARN, it probably
1097 ;; shouldn't go to *STANDARD-OUTPUT*, but *ERROR-OUTPUT* or
1098 ;; *QUERY-IO* or something. Look through this file to
1099 ;; straighten out stream usage.
1100 (princ "There is no such restart.")))))
1102 ;;;; information commands
1104 (!def-debug-command "HELP" ()
1105 ;; CMU CL had a little toy pager here, but "if you aren't running
1106 ;; ILISP (or a smart windowing system, or something) you deserve to
1107 ;; lose", so we've dropped it in SBCL. However, in case some
1108 ;; desperate holdout is running this on a dumb terminal somewhere,
1109 ;; we tell him where to find the message stored as a string.
1111 "~&~A~2%(The HELP string is stored in ~S.)~%"
1113 '*debug-help-string*))
1115 (!def-debug-command-alias "?" "HELP")
1117 (!def-debug-command "ERROR" ()
1118 (format *debug-io* "~A~%" *debug-condition*)
1119 (show-restarts *debug-restarts* *debug-io*))
1121 (!def-debug-command "BACKTRACE" ()
1122 (backtrace (read-if-available most-positive-fixnum)))
1124 (!def-debug-command "PRINT" ()
1125 (print-frame-call *current-frame*))
1127 (!def-debug-command-alias "P" "PRINT")
1129 (!def-debug-command "LIST-LOCALS" ()
1130 (let ((d-fun (sb!di:frame-debug-fun *current-frame*)))
1131 (if (sb!di:debug-var-info-available d-fun)
1132 (let ((*standard-output* *debug-io*)
1133 (location (sb!di:frame-code-location *current-frame*))
1134 (prefix (read-if-available nil))
1137 (dolist (v (sb!di:ambiguous-debug-vars
1139 (if prefix (string prefix) "")))
1141 (when (eq (sb!di:debug-var-validity v location) :valid)
1142 (setf any-valid-p t)
1143 (format t "~S~:[#~W~;~*~] = ~S~%"
1144 (sb!di:debug-var-symbol v)
1145 (zerop (sb!di:debug-var-id v))
1146 (sb!di:debug-var-id v)
1147 (sb!di:debug-var-value v *current-frame*))))
1151 (format t "There are no local variables ~@[starting with ~A ~]~
1155 (format t "All variables ~@[starting with ~A ~]currently ~
1156 have invalid values."
1158 (write-line "There is no variable information available."))))
1160 (!def-debug-command-alias "L" "LIST-LOCALS")
1162 (!def-debug-command "SOURCE" ()
1164 (print-code-location-source-form (sb!di:frame-code-location *current-frame*)
1165 (read-if-available 0)))
1167 ;;;; source location printing
1169 ;;; We cache a stream to the last valid file debug source so that we
1170 ;;; won't have to repeatedly open the file.
1172 ;;; KLUDGE: This sounds like a bug, not a feature. Opening files is fast
1173 ;;; in the 1990s, so the benefit is negligible, less important than the
1174 ;;; potential of extra confusion if someone changes the source during
1175 ;;; a debug session and the change doesn't show up. And removing this
1176 ;;; would simplify the system, which I like. -- WHN 19990903
1177 (defvar *cached-debug-source* nil)
1178 (declaim (type (or sb!di:debug-source null) *cached-debug-source*))
1179 (defvar *cached-source-stream* nil)
1180 (declaim (type (or stream null) *cached-source-stream*))
1182 ;;; To suppress the read-time evaluation #. macro during source read,
1183 ;;; *READTABLE* is modified. *READTABLE* is cached to avoid
1184 ;;; copying it each time, and invalidated when the
1185 ;;; *CACHED-DEBUG-SOURCE* has changed.
1186 (defvar *cached-readtable* nil)
1187 (declaim (type (or readtable null) *cached-readtable*))
1189 ;;; Stuff to clean up before saving a core
1190 (defun debug-deinit ()
1191 (setf *cached-debug-source* nil
1192 *cached-source-stream* nil
1193 *cached-readtable* nil))
1195 ;;; We also cache the last toplevel form that we printed a source for
1196 ;;; so that we don't have to do repeated reads and calls to
1197 ;;; FORM-NUMBER-TRANSLATIONS.
1198 (defvar *cached-toplevel-form-offset* nil)
1199 (declaim (type (or index null) *cached-toplevel-form-offset*))
1200 (defvar *cached-toplevel-form*)
1201 (defvar *cached-form-number-translations*)
1203 ;;; Given a code location, return the associated form-number
1204 ;;; translations and the actual top level form. We check our cache ---
1205 ;;; if there is a miss, we dispatch on the kind of the debug source.
1206 (defun get-toplevel-form (location)
1207 (let ((d-source (sb!di:code-location-debug-source location)))
1208 (if (and (eq d-source *cached-debug-source*)
1209 (eql (sb!di:code-location-toplevel-form-offset location)
1210 *cached-toplevel-form-offset*))
1211 (values *cached-form-number-translations* *cached-toplevel-form*)
1212 (let* ((offset (sb!di:code-location-toplevel-form-offset location))
1214 (ecase (sb!di:debug-source-from d-source)
1215 (:file (get-file-toplevel-form location))
1216 (:lisp (svref (sb!di:debug-source-name d-source) offset)))))
1217 (setq *cached-toplevel-form-offset* offset)
1218 (values (setq *cached-form-number-translations*
1219 (sb!di:form-number-translations res offset))
1220 (setq *cached-toplevel-form* res))))))
1222 ;;; Locate the source file (if it still exists) and grab the top level
1223 ;;; form. If the file is modified, we use the top level form offset
1224 ;;; instead of the recorded character offset.
1225 (defun get-file-toplevel-form (location)
1226 (let* ((d-source (sb!di:code-location-debug-source location))
1227 (tlf-offset (sb!di:code-location-toplevel-form-offset location))
1228 (local-tlf-offset (- tlf-offset
1229 (sb!di:debug-source-root-number d-source)))
1231 (aref (or (sb!di:debug-source-start-positions d-source)
1232 (error "no start positions map"))
1234 (name (sb!di:debug-source-name d-source)))
1235 (unless (eq d-source *cached-debug-source*)
1236 (unless (and *cached-source-stream*
1237 (equal (pathname *cached-source-stream*)
1239 (setq *cached-readtable* nil)
1240 (when *cached-source-stream* (close *cached-source-stream*))
1241 (setq *cached-source-stream* (open name :if-does-not-exist nil))
1242 (unless *cached-source-stream*
1243 (error "The source file no longer exists:~% ~A" (namestring name)))
1244 (format t "~%; file: ~A~%" (namestring name)))
1246 (setq *cached-debug-source*
1247 (if (= (sb!di:debug-source-created d-source)
1248 (file-write-date name))
1252 ((eq *cached-debug-source* d-source)
1253 (file-position *cached-source-stream* char-offset))
1255 (format t "~%; File has been modified since compilation:~%; ~A~@
1256 ; Using form offset instead of character position.~%"
1258 (file-position *cached-source-stream* 0)
1259 (let ((*read-suppress* t))
1260 (dotimes (i local-tlf-offset)
1261 (read *cached-source-stream*)))))
1262 (unless *cached-readtable*
1263 (setq *cached-readtable* (copy-readtable))
1264 (set-dispatch-macro-character
1266 (lambda (stream sub-char &rest rest)
1267 (declare (ignore rest sub-char))
1268 (let ((token (read stream t nil t)))
1269 (format nil "#.~S" token)))
1270 *cached-readtable*))
1271 (let ((*readtable* *cached-readtable*))
1272 (read *cached-source-stream*))))
1274 (defun print-code-location-source-form (location context)
1275 (let* ((location (maybe-block-start-location location))
1276 (form-num (sb!di:code-location-form-number location)))
1277 (multiple-value-bind (translations form) (get-toplevel-form location)
1278 (unless (< form-num (length translations))
1279 (error "The source path no longer exists."))
1280 (prin1 (sb!di:source-path-context form
1281 (svref translations form-num)
1284 ;;; step to the next steppable form
1285 (!def-debug-command "STEP" ()
1286 (let ((restart (find-restart 'continue *debug-condition*)))
1290 (invoke-restart restart))
1292 (format *debug-io* "~&Non-continuable error, cannot step.~%")))))
1294 ;;; miscellaneous commands
1296 (!def-debug-command "DESCRIBE" ()
1297 (let* ((curloc (sb!di:frame-code-location *current-frame*))
1298 (debug-fun (sb!di:code-location-debug-fun curloc))
1299 (function (sb!di:debug-fun-fun debug-fun)))
1302 (format t "can't figure out the function for this frame"))))
1304 (!def-debug-command "SLURP" ()
1305 (loop while (read-char-no-hang *standard-input*)))
1307 (!def-debug-command "RETURN" (&optional
1308 (return (read-prompting-maybe
1310 (let ((tag (find-if (lambda (x)
1311 (and (typep (car x) 'symbol)
1312 (not (symbol-package (car x)))
1313 (string= (car x) "SB-DEBUG-CATCH-TAG")))
1314 (sb!di::frame-catches *current-frame*))))
1317 (funcall (sb!di:preprocess-for-eval
1319 (sb!di:frame-code-location *current-frame*))
1321 (format t "~@<can't find a tag for this frame ~
1322 ~2I~_(hint: try increasing the DEBUG optimization quality ~
1323 and recompiling)~:@>"))))
1325 ;;;; debug loop command utilities
1327 (defun read-prompting-maybe (prompt)
1328 (unless (sb!int:listen-skip-whitespace *debug-io*)
1333 (defun read-if-available (default)
1334 (if (sb!int:listen-skip-whitespace *debug-io*)