fix (again) the handling of read errors in the debugger

[sbcl.git] / src / code / debug.lisp

diff --git a/src/code/debug.lisp b/src/code/debug.lisp
index 0e33618..76a87d8 100644 (file)
--- a/src/code/debug.lisp
+++ b/src/code/debug.lisp
@@ -24,19 +24,27 @@
 ;;;   * As condition :REPORT methods are converted to use the pretty
 ;;;     printer, they acquire *PRINT-LEVEL* constraints, so e.g. under
 ;;;     sbcl-0.7.1.28's old value of *DEBUG-PRINT-LEVEL*=3, an
 ;;;   * As condition :REPORT methods are converted to use the pretty
 ;;;     printer, they acquire *PRINT-LEVEL* constraints, so e.g. under
 ;;;     sbcl-0.7.1.28's old value of *DEBUG-PRINT-LEVEL*=3, an

-;;;     ARG-COUNT-ERROR printed as 
+;;;     ARG-COUNT-ERROR printed as

 ;;;       error while parsing arguments to DESTRUCTURING-BIND:
 ;;;         invalid number of elements in
 ;;;           #
 ;;;         to satisfy lambda list
 ;;;           #:
 ;;;         exactly 2 expected, but 5 found
 ;;;       error while parsing arguments to DESTRUCTURING-BIND:
 ;;;         invalid number of elements in
 ;;;           #
 ;;;         to satisfy lambda list
 ;;;           #:
 ;;;         exactly 2 expected, but 5 found

-(defvar *debug-print-level* 5
+(defvar *debug-print-variable-alist* nil

   #!+sb-doc
   #!+sb-doc

-  "*PRINT-LEVEL* for the debugger")
-(defvar *debug-print-length* 7
-  #!+sb-doc
-  "*PRINT-LENGTH* for the debugger")
+  "an association list describing new bindings for special variables
+to be used within the debugger. Eg.
+
+ ((*PRINT-LENGTH* . 10) (*PRINT-LEVEL* . 6) (*PRINT-PRETTY* . NIL))
+
+The variables in the CAR positions are bound to the values in the CDR
+during the execution of some debug commands. When evaluating arbitrary
+expressions in the debugger, the normal values of the printer control
+variables are in effect.
+
+Initially empty, *DEBUG-PRINT-VARIABLE-ALIST* is typically used to
+provide bindings for printer control variables.")

 
 (defvar *debug-readtable*
   ;; KLUDGE: This can't be initialized in a cold toplevel form,
 
 (defvar *debug-readtable*
   ;; KLUDGE: This can't be initialized in a cold toplevel form,

@@ -54,12 +62,13 @@
 ;;; nestedness inside debugger command loops
 (defvar *debug-command-level* 0)
 
 ;;; nestedness inside debugger command loops
 (defvar *debug-command-level* 0)
 

-;;; If this is bound before the debugger is invoked, it is used as the
-;;; stack top by the debugger.
+;;; If this is bound before the debugger is invoked, it is used as the stack
+;;; top by the debugger. It can either be the first interesting frame, or the
+;;; name of the last uninteresting frame.

 (defvar *stack-top-hint* nil)
 
 (defvar *stack-top-hint* nil)
 

-(defvar *stack-top* nil)

 (defvar *real-stack-top* nil)
 (defvar *real-stack-top* nil)

+(defvar *stack-top* nil)

 
 (defvar *current-frame* nil)
 
 
 (defvar *current-frame* nil)
 

@@ -71,55 +80,55 @@
   "Should the debugger display beginner-oriented help messages?")
 
 (defun debug-prompt (stream)
   "Should the debugger display beginner-oriented help messages?")
 
 (defun debug-prompt (stream)

+  (sb!thread::get-foreground)

   (format stream
   (format stream

-         "~%~W~:[~;[~W~]] "
-         (sb!di:frame-number *current-frame*)
-         (> *debug-command-level* 1)
-         *debug-command-level*))
-  
+          "~%~W~:[~;[~W~]] "
+          (sb!di:frame-number *current-frame*)
+          (> *debug-command-level* 1)
+          *debug-command-level*))
+

 (defparameter *debug-help-string*
 "The debug prompt is square brackets, with number(s) indicating the current
   control stack level and, if you've entered the debugger recursively, how
   deeply recursed you are.
 Any command -- including the name of a restart -- may be uniquely abbreviated.
 The debugger rebinds various special variables for controlling i/o, sometimes
 (defparameter *debug-help-string*
 "The debug prompt is square brackets, with number(s) indicating the current
   control stack level and, if you've entered the debugger recursively, how
   deeply recursed you are.
 Any command -- including the name of a restart -- may be uniquely abbreviated.
 The debugger rebinds various special variables for controlling i/o, sometimes

-  to defaults (much like WITH-STANDARD-IO-SYNTAX does) and sometimes to 
-  its own special values, e.g. SB-DEBUG:*DEBUG-PRINT-LEVEL*.
+  to defaults (much like WITH-STANDARD-IO-SYNTAX does) and sometimes to
+  its own special values, based on SB-EXT:*DEBUG-PRINT-VARIABLE-ALIST*.

 Debug commands do not affect *, //, and similar variables, but evaluation in
   the debug loop does affect these variables.
 SB-DEBUG:*FLUSH-DEBUG-ERRORS* controls whether errors at the debug prompt
 Debug commands do not affect *, //, and similar variables, but evaluation in
   the debug loop does affect these variables.
 SB-DEBUG:*FLUSH-DEBUG-ERRORS* controls whether errors at the debug prompt

-  drop you deeper into the debugger.
+  drop you deeper into the debugger. The default NIL allows recursive entry
+  to debugger.

 
 Getting in and out of the debugger:
 
 Getting in and out of the debugger:

-  RESTART  invokes restart numbered as shown (prompt if not given).
-  ERROR    prints the error condition and restart cases.
+  TOPLEVEL, TOP  exits debugger and returns to top level REPL
+  RESTART        invokes restart numbered as shown (prompt if not given).
+  ERROR          prints the error condition and restart cases.
+

   The number of any restart, or its name, or a unique abbreviation for its
   The number of any restart, or its name, or a unique abbreviation for its

-    name, is a valid command, and is the same as using RESTART to invoke
-    that restart.
+   name, is a valid command, and is the same as using RESTART to invoke
+   that restart.

 
 Changing frames:
 
 Changing frames:

-  U      up frame     D    down frame
-  B  bottom frame     F n  frame n (n=0 for top frame)
+  UP     up frame         DOWN     down frame
+  BOTTOM bottom frame     FRAME n  frame n (n=0 for top frame)

 
 Inspecting frames:
   BACKTRACE [n]  shows n frames going down the stack.
 
 Inspecting frames:
   BACKTRACE [n]  shows n frames going down the stack.

-  LIST-LOCALS, L lists locals in current function.
-  PRINT, P       displays current function call.
+  LIST-LOCALS, L lists locals in current frame.
+  PRINT, P       displays function call for current frame.

   SOURCE [n]     displays frame's source form with n levels of enclosing forms.
 
   SOURCE [n]     displays frame's source form with n levels of enclosing forms.
 

-Breakpoints and steps:
-  LIST-LOCATIONS [{function | :C}]   List the locations for breakpoints.
-                                     Specify :C for the current frame.
-    Abbreviation: LL
-  LIST-BREAKPOINTS                   List the active breakpoints.
-    Abbreviations: LB, LBP
-  DELETE-BREAKPOINT [n]              Remove breakpoint n or all breakpoints.
-    Abbreviations: DEL, DBP
-  BREAKPOINT {n | :end | :start} [:break form] [:function function]
-             [{:print form}*] [:condition form]
-                                     Set a breakpoint.
-    Abbreviations: BR, BP
-  STEP [n]                           Step to the next location or step n times.
+Stepping:
+  START Selects the CONTINUE restart if one exists and starts
+        single-stepping. Single stepping affects only code compiled with
+        under high DEBUG optimization quality. See User Manual for details.
+  STEP  Steps into the current form.
+  NEXT  Steps over the current form.
+  OUT   Stops stepping temporarily, but resumes it when the topmost frame that
+        was stepped into returns.
+  STOP  Stops single-stepping.

 
 Function and macro commands:
  (SB-DEBUG:ARG n)
 
 Function and macro commands:
  (SB-DEBUG:ARG n)

@@ -129,127 +138,20 @@ Function and macro commands:
 
 Other commands:
   RETURN expr
 
 Other commands:
   RETURN expr

-    [EXPERIMENTAL] Return the values resulting from evaluation of expr
-    from the current frame, if this frame was compiled with a sufficiently
-    high DEBUG optimization quality.
+    Return the values resulting from evaluation of expr from the
+    current frame, if this frame was compiled with a sufficiently high
+    DEBUG optimization quality.
+
+  RESTART-FRAME
+    Restart execution of the current frame, if this frame is for a
+    global function which was compiled with a sufficiently high
+    DEBUG optimization quality.
+

   SLURP
     Discard all pending input on *STANDARD-INPUT*. (This can be
     useful when the debugger was invoked to handle an error in
     deeply nested input syntax, and now the reader is confused.)")
 \f
   SLURP
     Discard all pending input on *STANDARD-INPUT*. (This can be
     useful when the debugger was invoked to handle an error in
     deeply nested input syntax, and now the reader is confused.)")
 \f

-;;; This is used to communicate to DEBUG-LOOP that we are at a step breakpoint.
-(define-condition step-condition (simple-condition) ())
-\f
-;;;; breakpoint state
-
-(defvar *only-block-start-locations* nil
-  #!+sb-doc
-  "When true, the LIST-LOCATIONS command only displays block start locations.
-   Otherwise, all locations are displayed.")
-
-(defvar *print-location-kind* nil
-  #!+sb-doc
-  "When true, list the code location type in the LIST-LOCATIONS command.")
-
-;;; a list of the types of code-locations that should not be stepped
-;;; to and should not be listed when listing breakpoints
-(defvar *bad-code-location-types* '(:call-site :internal-error))
-(declaim (type list *bad-code-location-types*))
-
-;;; code locations of the possible breakpoints
-(defvar *possible-breakpoints*)
-(declaim (type list *possible-breakpoints*))
-
-;;; a list of the made and active breakpoints, each is a
-;;; BREAKPOINT-INFO structure
-(defvar *breakpoints* nil)
-(declaim (type list *breakpoints*))
-
-;;; a list of BREAKPOINT-INFO structures of the made and active step
-;;; breakpoints
-(defvar *step-breakpoints* nil)
-(declaim (type list *step-breakpoints*))
-
-;;; the number of times left to step
-(defvar *number-of-steps* 1)
-(declaim (type integer *number-of-steps*))
-
-;;; This is used when listing and setting breakpoints.
-(defvar *default-breakpoint-debug-fun* nil)
-(declaim (type (or list sb!di:debug-fun) *default-breakpoint-debug-fun*))
-\f
-;;;; code location utilities
-
-;;; Return the first code-location in the passed debug block.
-(defun first-code-location (debug-block)
-  (let ((found nil)
-       (first-code-location nil))
-    (sb!di:do-debug-block-locations (code-location debug-block)
-      (unless found
-       (setf first-code-location code-location)
-       (setf found t)))
-    first-code-location))
-
-;;; Return a list of the next code-locations following the one passed.
-;;; One of the *BAD-CODE-LOCATION-TYPES* will not be returned.
-(defun next-code-locations (code-location)
-  (let ((debug-block (sb!di:code-location-debug-block code-location))
-       (block-code-locations nil))
-    (sb!di:do-debug-block-locations (block-code-location debug-block)
-      (unless (member (sb!di:code-location-kind block-code-location)
-                     *bad-code-location-types*)
-       (push block-code-location block-code-locations)))
-    (setf block-code-locations (nreverse block-code-locations))
-    (let* ((code-loc-list (rest (member code-location block-code-locations
-                                       :test #'sb!di:code-location=)))
-          (next-list (cond (code-loc-list
-                            (list (first code-loc-list)))
-                           ((map 'list #'first-code-location
-                                 (sb!di:debug-block-successors debug-block)))
-                           (t nil))))
-      (when (and (= (length next-list) 1)
-                (sb!di:code-location= (first next-list) code-location))
-       (setf next-list (next-code-locations (first next-list))))
-      next-list)))
-
-;;; Return a list of code-locations of the possible breakpoints of DEBUG-FUN.
-(defun possible-breakpoints (debug-fun)
-  (let ((possible-breakpoints nil))
-    (sb!di:do-debug-fun-blocks (debug-block debug-fun)
-      (unless (sb!di:debug-block-elsewhere-p debug-block)
-       (if *only-block-start-locations*
-           (push (first-code-location debug-block) possible-breakpoints)
-           (sb!di:do-debug-block-locations (code-location debug-block)
-             (when (not (member (sb!di:code-location-kind code-location)
-                                *bad-code-location-types*))
-               (push code-location possible-breakpoints))))))
-    (nreverse possible-breakpoints)))
-
-;;; Search the info-list for the item passed (CODE-LOCATION,
-;;; DEBUG-FUN, or BREAKPOINT-INFO). If the item passed is a debug
-;;; function then kind will be compared if it was specified. The kind
-;;; if also compared if a breakpoint-info is passed since it's in the
-;;; breakpoint. The info structure is returned if found.
-(defun location-in-list (place info-list &optional (kind nil))
-  (when (breakpoint-info-p place)
-    (setf kind (sb!di:breakpoint-kind (breakpoint-info-breakpoint place)))
-    (setf place (breakpoint-info-place place)))
-  (cond ((sb!di:code-location-p place)
-        (find place info-list
-              :key #'breakpoint-info-place
-              :test (lambda (x y) (and (sb!di:code-location-p y)
-                                       (sb!di:code-location= x y)))))
-       (t
-        (find place info-list
-              :test (lambda (x-debug-fun y-info)
-                      (let ((y-place (breakpoint-info-place y-info))
-                            (y-breakpoint (breakpoint-info-breakpoint
-                                           y-info)))
-                        (and (sb!di:debug-fun-p y-place)
-                             (eq x-debug-fun y-place)
-                             (or (not kind)
-                                 (eq kind (sb!di:breakpoint-kind
-                                           y-breakpoint))))))))))

 
 ;;; If LOC is an unknown location, then try to find the block start
 ;;; location. Used by source printing to some information instead of
 
 ;;; If LOC is an unknown location, then try to find the block start
 ;;; location. Used by source printing to some information instead of

@@ -257,230 +159,272 @@ Other commands:
 (defun maybe-block-start-location (loc)
   (if (sb!di:code-location-unknown-p loc)
       (let* ((block (sb!di:code-location-debug-block loc))
 (defun maybe-block-start-location (loc)
   (if (sb!di:code-location-unknown-p loc)
       (let* ((block (sb!di:code-location-debug-block loc))

-            (start (sb!di:do-debug-block-locations (loc block)
-                     (return loc))))
-       (cond ((and (not (sb!di:debug-block-elsewhere-p block))
-                   start)
-              ;; FIXME: Why output on T instead of *DEBUG-FOO* or something?
-              (format t "~%unknown location: using block start~%")
-              start)
-             (t
-              loc)))
+             (start (sb!di:do-debug-block-locations (loc block)
+                      (return loc))))
+        (cond ((and (not (sb!di:debug-block-elsewhere-p block))
+                    start)
+               (format *debug-io* "~%unknown location: using block start~%")
+               start)
+              (t
+               loc)))

       loc))
 \f
       loc))
 \f

-;;;; the BREAKPOINT-INFO structure
-
-;;; info about a made breakpoint
-(defstruct (breakpoint-info (:copier nil)
-                           (:constructor %make-breakpoint-info))
-  ;; where we are going to stop
-  (place (missing-arg)
-        :type (or sb!di:code-location sb!di:debug-fun)
-        :read-only t)
-  ;; the breakpoint returned by SB!DI:MAKE-BREAKPOINT
-  (breakpoint (missing-arg) :type sb!di:breakpoint :read-only t)
-  ;; the function returned from SB!DI:PREPROCESS-FOR-EVAL. If result is
-  ;; non-NIL, drop into the debugger.
-  (break #'identity :type function :read-only t)
-  ;; the function returned from SB!DI:PREPROCESS-FOR-EVAL. If result is
-  ;; non-NIL, eval (each) print and print results.
-  (condition #'identity :type function :read-only t)
-  ;; the list of functions from SB!DI:PREPROCESS-FOR-EVAL to evaluate.
-  ;; Results are conditionally printed. CAR of each element is the
-  ;; function, CDR is the form it goes with.
-  (print nil :type list :read-only t)
-  ;; the number used when listing the possible breakpoints within a
-  ;; function; or could also be a symbol such as START or END
-  (code-location-selector (missing-arg) :type (or symbol integer) :read-only t)
-  ;; the number used when listing the active breakpoints, and when
-  ;; deleting breakpoints
-  (breakpoint-number (missing-arg) :type integer :read-only t))
-
-(defun create-breakpoint-info (place breakpoint code-location-selector
-                                    &key (break #'identity)
-                                    (condition #'identity) (print nil))
-  (setf *breakpoints*
-       (sort *breakpoints* #'< :key #'breakpoint-info-breakpoint-number))
-  (let ((breakpoint-number
-        (do ((i 1 (incf i)) (breakpoints *breakpoints* (rest breakpoints)))
-            ((or (> i (length *breakpoints*))
-                 (not (= i (breakpoint-info-breakpoint-number
-                            (first breakpoints)))))
-
-             i))))
-    (%make-breakpoint-info :place place
-                          :breakpoint breakpoint
-                          :code-location-selector code-location-selector
-                          :breakpoint-number breakpoint-number
-                          :break break
-                          :condition condition
-                          :print print)))
-
-(defun print-breakpoint-info (breakpoint-info)
-  (let ((place (breakpoint-info-place breakpoint-info))
-       (bp-number (breakpoint-info-breakpoint-number breakpoint-info)))
-    (case (sb!di:breakpoint-kind (breakpoint-info-breakpoint breakpoint-info))
-      (:code-location
-       (print-code-location-source-form place 0)
-       (format t
-              "~&~S: ~S in ~S"
-              bp-number
-              (breakpoint-info-code-location-selector breakpoint-info)
-              (sb!di:debug-fun-name (sb!di:code-location-debug-fun place))))
-      (:fun-start
-       (format t "~&~S: FUN-START in ~S" bp-number
-              (sb!di:debug-fun-name place)))
-      (:fun-end
-       (format t "~&~S: FUN-END in ~S" bp-number
-              (sb!di:debug-fun-name place))))))
-\f
-;;;; MAIN-HOOK-FUN for steps and breakpoints
-
-;;; This must be passed as the hook function. It keeps track of where
-;;; STEP breakpoints are.
-(defun main-hook-fun (current-frame breakpoint &optional return-vals
-                                   fun-end-cookie)
-  (setf *default-breakpoint-debug-fun*
-       (sb!di:frame-debug-fun current-frame))
-  (dolist (step-info *step-breakpoints*)
-    (sb!di:delete-breakpoint (breakpoint-info-breakpoint step-info))
-    (let ((bp-info (location-in-list step-info *breakpoints*)))
-      (when bp-info
-       (sb!di:activate-breakpoint (breakpoint-info-breakpoint bp-info)))))
-  (let ((*stack-top-hint* current-frame)
-       (step-hit-info
-        (location-in-list (sb!di:breakpoint-what breakpoint)
-                          *step-breakpoints*
-                          (sb!di:breakpoint-kind breakpoint)))
-       (bp-hit-info
-        (location-in-list (sb!di:breakpoint-what breakpoint)
-                          *breakpoints*
-                          (sb!di:breakpoint-kind breakpoint)))
-       (break)
-       (condition)
-       (string ""))
-    (setf *step-breakpoints* nil)
-    (labels ((build-string (str)
-              (setf string (concatenate 'string string str)))
-            (print-common-info ()
-              (build-string
-               (with-output-to-string (*standard-output*)
-                 (when fun-end-cookie
-                   (format t "~%Return values: ~S" return-vals))
-                 (when condition
-                   (when (breakpoint-info-print bp-hit-info)
-                     (format t "~%")
-                     (print-frame-call current-frame))
-                   (dolist (print (breakpoint-info-print bp-hit-info))
-                     (format t "~& ~S = ~S" (rest print)
-                             (funcall (first print) current-frame))))))))
-      (when bp-hit-info
-       (setf break (funcall (breakpoint-info-break bp-hit-info)
-                            current-frame))
-       (setf condition (funcall (breakpoint-info-condition bp-hit-info)
-                                current-frame)))
-      (cond ((and bp-hit-info step-hit-info (= 1 *number-of-steps*))
-            (build-string (format nil "~&*Step (to a breakpoint)*"))
-            (print-common-info)
-            (break string))
-           ((and bp-hit-info step-hit-info break)
-            (build-string (format nil "~&*Step (to a breakpoint)*"))
-            (print-common-info)
-            (break string))
-           ((and bp-hit-info step-hit-info)
-            (print-common-info)
-            (format t "~A" string)
-            (decf *number-of-steps*)
-            (set-step-breakpoint current-frame))
-           ((and step-hit-info (= 1 *number-of-steps*))
-            (build-string "*Step*")
-            (break (make-condition 'step-condition :format-control string)))
-           (step-hit-info
-            (decf *number-of-steps*)
-            (set-step-breakpoint current-frame))
-           (bp-hit-info
-            (when break
-              (build-string (format nil "~&*Breakpoint hit*")))
-            (print-common-info)
-            (if break
-                (break string)
-                (format t "~A" string)))
-           (t
-            (break "unknown breakpoint"))))))
-\f
-;;; Set breakpoints at the next possible code-locations. After calling
-;;; this, either (CONTINUE) if in the debugger or just let program flow
-;;; return if in a hook function.
-(defun set-step-breakpoint (frame)
-  (cond
-   ((sb!di:debug-block-elsewhere-p (sb!di:code-location-debug-block
-                                   (sb!di:frame-code-location frame)))
-    ;; FIXME: FORMAT T is used for error output here and elsewhere in
-    ;; the debug code.
-    (format t "cannot step, in elsewhere code~%"))
-   (t
-    (let* ((code-location (sb!di:frame-code-location frame))
-          (next-code-locations (next-code-locations code-location)))
-      (cond
-       (next-code-locations
-       (dolist (code-location next-code-locations)
-         (let ((bp-info (location-in-list code-location *breakpoints*)))
-           (when bp-info
-             (sb!di:deactivate-breakpoint (breakpoint-info-breakpoint
-                                           bp-info))))
-         (let ((bp (sb!di:make-breakpoint #'main-hook-fun code-location
-                                          :kind :code-location)))
-           (sb!di:activate-breakpoint bp)
-           (push (create-breakpoint-info code-location bp 0)
-                 *step-breakpoints*))))
-       (t
-       (let* ((debug-fun (sb!di:frame-debug-fun *current-frame*))
-              (bp (sb!di:make-breakpoint #'main-hook-fun debug-fun
-                                         :kind :fun-end)))
-         (sb!di:activate-breakpoint bp)
-         (push (create-breakpoint-info debug-fun bp 0)
-               *step-breakpoints*))))))))
-\f
-;;;; STEP
-
-;;; ANSI specifies that this macro shall exist, even if only as a
-;;; trivial placeholder like this.
-(defmacro step (form)
-  "a trivial placeholder implementation of the CL:STEP macro required by
-   the ANSI spec"
-  `(progn
-     ,form))
-\f

 ;;;; BACKTRACE
 
 ;;;; BACKTRACE
 

-(defun backtrace (&optional (count most-positive-fixnum)
-                           (*standard-output* *debug-io*))
+(declaim (unsigned-byte *backtrace-frame-count*))
+(defvar *backtrace-frame-count* 1000
+  "Default number of frames to backtrace. Defaults to 1000.")
+
+(declaim (type (member :minimal :normal :full) *method-frame-style*))
+(defvar *method-frame-style* :normal
+  "Determines how frames corresponding to method functions are represented in
+backtraces. Possible values are :MINIMAL, :NORMAL, and :FULL.
+
+  :MINIMAL represents them as
+
+    (<gf-name> ...args...)
+
+    if all arguments are available, and only a single method is applicable to
+    the arguments -- otherwise behaves as :NORMAL.
+
+  :NORMAL represents them as
+
+    ((:method <gf-name> [<qualifier>*] (<specializer>*)) ...args...)
+
+    The frame is then followed by either [fast-method] or [slow-method],
+    designating the kind of method function. (See below.)
+
+  :FULL represents them using the actual funcallable method function name:
+
+    ((sb-pcl:fast-method <gf-name> [<qualifier>*] (<specializer>*)) ...args...)
+
+   or
+
+    ((sb-pcl:slow-method <gf-name> [<qualifier>*] (<specializer>*)) ...args...)
+
+   In the this case arguments may include values internal to SBCL's method
+   dispatch machinery.")
+
+(define-deprecated-variable :early "1.1.4.9" *show-entry-point-details*
+  :value nil)
+
+(defun backtrace (&optional (count *backtrace-frame-count*) (stream *debug-io*))
+  "Replaced by PRINT-BACKTRACE, will eventually be deprecated."
+  (print-backtrace :count count :stream stream))
+
+(defun backtrace-as-list (&optional (count *backtrace-frame-count*))
+  "Replaced by LIST-BACKTRACE, will eventually be deprecated."
+  (list-backtrace :count count))
+
+(defun backtrace-start-frame (frame-designator)
+  (let ((here (sb!di:top-frame)))
+    (labels ((current-frame ()
+               (let ((frame here))
+                 ;; Our caller's caller.
+                 (loop repeat 2
+                       do (setf frame (or (sb!di:frame-down frame) frame)))
+                 frame))
+             (interrupted-frame ()
+               (or (nth-value 1 (find-interrupted-name-and-frame))
+                   (current-frame))))
+     (cond ((eq :current-frame frame-designator)
+            (current-frame))
+           ((eq :interrupted-frame frame-designator)
+            (interrupted-frame))
+           ((eq :debugger-frame frame-designator)
+            (if (and *in-the-debugger* *current-frame*)
+                *current-frame*
+                (interrupted-frame)))
+           ((sb!di:frame-p frame-designator)
+            frame-designator)
+           (t
+            (error "Invalid designator for initial backtrace frame: ~S"
+                   frame-designator))))))
+
+(defun map-backtrace (function &key
+                      (start 0)
+                      (from :debugger-frame)
+                      (count *backtrace-frame-count*))
+  #!+sb-doc
+  "Calls the designated FUNCTION with each frame on the call stack.
+Returns the last value returned by FUNCTION.
+
+COUNT is the number of frames to backtrace, defaulting to
+*BACKTRACE-FRAME-COUNT*.
+
+START is the number of the frame the backtrace should start from.
+
+FROM specifies the frame relative to which the frames are numbered. Possible
+values are an explicit SB-DI:FRAME object, and the
+keywords :CURRENT-FRAME, :INTERRUPTED-FRAME, and :DEBUGGER-FRAME. Default
+is :DEBUGGER-FRAME.
+
+  :CURRENT-FRAME
+    specifies the caller of MAP-BACKTRACE.
+
+  :INTERRUPTED-FRAME
+    specifies the first interrupted frame on the stack \(typically the frame
+    where the error occured, as opposed to error handling frames) if any,
+    otherwise behaving as :CURRENT-FRAME.
+
+  :DEBUGGER-FRAME
+    specifies the currently debugged frame when inside the debugger, and
+    behaves as :INTERRUPTED-FRAME outside the debugger.
+"
+  (loop with result = nil
+        for index upfrom 0
+        for frame = (backtrace-start-frame from)
+        then (sb!di:frame-down frame)
+        until (null frame)
+        when (<= start index) do
+        (if (minusp (decf count))
+            (return result)
+            (setf result (funcall function frame)))
+        finally (return result)))
+
+(defun print-backtrace (&key
+                        (stream *debug-io*)
+                        (start 0)
+                        (from :debugger-frame)
+                        (count *backtrace-frame-count*)
+                        (print-thread t)
+                        (print-frame-source nil)
+                        (method-frame-style *method-frame-style*))

   #!+sb-doc
   #!+sb-doc

-  "Show a listing of the call stack going down from the current frame. In the
-   debugger, the current frame is indicated by the prompt. COUNT is how many
-   frames to show."
-  (fresh-line *standard-output*)
-  (do ((frame (if *in-the-debugger* *current-frame* (sb!di:top-frame))
-             (sb!di:frame-down frame))
-       (count count (1- count)))
-      ((or (null frame) (zerop count)))
-    (print-frame-call frame :number t))
-  (fresh-line *standard-output*)
+  "Print a listing of the call stack to STREAM, defaulting to *DEBUG-IO*.
+
+COUNT is the number of frames to backtrace, defaulting to
+*BACKTRACE-FRAME-COUNT*.
+
+START is the number of the frame the backtrace should start from.
+
+FROM specifies the frame relative to which the frames are numbered. Possible
+values are an explicit SB-DI:FRAME object, and the
+keywords :CURRENT-FRAME, :INTERRUPTED-FRAME, and :DEBUGGER-FRAME. Default
+is :DEBUGGER-FRAME.
+
+  :CURRENT-FRAME
+    specifies the caller of PRINT-BACKTRACE.
+
+  :INTERRUPTED-FRAME
+    specifies the first interrupted frame on the stack \(typically the frame
+    where the error occured, as opposed to error handling frames) if any,
+    otherwise behaving as :CURRENT-FRAME.
+
+  :DEBUGGER-FRAME
+    specifies the currently debugged frame when inside the debugger, and
+    behaves as :INTERRUPTED-FRAME outside the debugger.
+
+If PRINT-THREAD is true (default), backtrace is preceded by printing the
+thread object the backtrace is from.
+
+If PRINT-FRAME-SOURCE is true (default is false), each frame is followed by
+printing the currently executing source form in the function responsible for
+that frame, when available. Requires the function to have been compiled at
+DEBUG 2 or higher. If PRINT-FRAME-SOURCE is :ALWAYS, it also reports \"no
+source available\" for frames for which were compiled at lower debug settings.
+
+METHOD-FRAME-STYLE (defaulting to *METHOD-FRAME-STYLE*), determines how frames
+corresponding to method functions are printed. Possible values
+are :MINIMAL, :NORMAL, and :FULL. See *METHOD-FRAME-STYLE* for more
+information."
+  (fresh-line stream)
+  (when print-thread
+    (format stream "Backtrace for: ~S~%" sb!thread:*current-thread*))
+  (let ((*suppress-print-errors* (if (subtypep 'serious-condition *suppress-print-errors*)
+                                     *suppress-print-errors*
+                                     'serious-condition))
+        (*print-circle* t)
+        (n start))
+    (handler-bind ((print-not-readable #'print-unreadably))
+        (map-backtrace (lambda (frame)
+                         (print-frame-call frame stream
+                                           :number n
+                                           :method-frame-style method-frame-style
+                                           :print-frame-source print-frame-source)
+                         (incf n))
+                       :from (backtrace-start-frame from)
+                       :start start
+                       :count count)))
+  (fresh-line stream)

   (values))
 
   (values))
 

-(defun backtrace-as-list (&optional (count most-positive-fixnum))
-  #!+sb-doc "Return a list representing the current BACKTRACE."
-  (do ((reversed-result nil)
-       (frame (if *in-the-debugger* *current-frame* (sb!di:top-frame))
-             (sb!di:frame-down frame))
-       (count count (1- count)))
-      ((or (null frame) (zerop count))
-       (nreverse reversed-result))
-    (push (frame-call-as-list frame) reversed-result)))
-
-(defun frame-call-as-list (frame)
-  (cons (sb!di:debug-fun-name (sb!di:frame-debug-fun frame))
-       (frame-args-as-list frame)))
+(defun list-backtrace (&key
+                       (count *backtrace-frame-count*)
+                       (start 0)
+                       (from :debugger-frame)
+                       (method-frame-style *method-frame-style*))
+  #!+sb-doc
+    "Returns a list describing the call stack. Each frame is represented
+by a sublist:
+
+  \(<name> ...args...)
+
+where the name describes the function responsible for the frame. The name
+might not be bound to the actual function object. Unavailable arguments are
+represented by dummy objects that print as #<unavailable argument>. Objects
+with dynamic-extent allocation by the current thread are represented by
+substitutes to avoid references to them from leaking outside their legal
+extent.
+
+COUNT is the number of frames to backtrace, defaulting to
+*BACKTRACE-FRAME-COUNT*.
+
+START is the number of the frame the backtrace should start from.
+
+FROM specifies the frame relative to which the frames are numbered. Possible
+values are an explicit SB-DI:FRAME object, and the
+keywords :CURRENT-FRAME, :INTERRUPTED-FRAME, and :DEBUGGER-FRAME. Default
+is :DEBUGGER-FRAME.
+
+  :CURRENT-FRAME
+    specifies the caller of LIST-BACKTRACE.
+
+  :INTERRUPTED-FRAME
+    specifies the first interrupted frame on the stack \(typically the frame
+    where the error occured, as opposed to error handling frames) if any,
+    otherwise behaving as :CURRENT-FRAME.
+
+  :DEBUGGER-FRAME
+    specifies the currently debugged frame when inside the debugger, and
+    behaves as :INTERRUPTED-FRAME outside the debugger.
+
+METHOD-FRAME-STYLE (defaulting to *METHOD-FRAME-STYLE*), determines how frames
+corresponding to method functions are printed. Possible values
+are :MINIMAL, :NORMAL, and :FULL. See *METHOD-FRAME-STYLE* for more
+information."
+  (let (rbacktrace)
+     (map-backtrace
+      (lambda (frame)
+        (push (frame-call-as-list frame :method-frame-style method-frame-style)
+              rbacktrace))
+      :count count
+      :start start
+      :from (backtrace-start-frame from))
+     (nreverse rbacktrace)))
+
+(defun frame-call-as-list (frame &key (method-frame-style *method-frame-style*))
+  (multiple-value-bind (name args info)
+      (frame-call frame :method-frame-style method-frame-style
+                        :replace-dynamic-extent-objects t)
+    (values (cons name args) info)))
+
+(defun replace-dynamic-extent-object (obj)
+  (if (stack-allocated-p obj)
+      (make-unprintable-object
+       (handler-case
+           (format nil "dynamic-extent: ~S" obj)
+         (error ()
+           "error printing dynamic-extent object")))
+      obj))
+
+(defun stack-allocated-p (obj)
+  "Returns T if OBJ is allocated on the stack of the current
+thread, NIL otherwise."
+  (with-pinned-objects (obj)
+    (let ((sap (int-sap (get-lisp-obj-address obj))))
+      (when (sb!vm:control-stack-pointer-valid-p sap nil)
+        t))))

 \f
 ;;;; frame printing
 
 \f
 ;;;; frame printing
 

@@ -489,20 +433,22 @@ Other commands:
 ;;; This is a convenient way to express what to do for each type of
 ;;; lambda-list element.
 (sb!xc:defmacro lambda-list-element-dispatch (element
 ;;; This is a convenient way to express what to do for each type of
 ;;; lambda-list element.
 (sb!xc:defmacro lambda-list-element-dispatch (element

-                                             &key
-                                             required
-                                             optional
-                                             rest
-                                             keyword
-                                             deleted)
+                                              &key
+                                              required
+                                              optional
+                                              rest
+                                              keyword
+                                              more
+                                              deleted)

   `(etypecase ,element
      (sb!di:debug-var
       ,@required)
      (cons
       (ecase (car ,element)
   `(etypecase ,element
      (sb!di:debug-var
       ,@required)
      (cons
       (ecase (car ,element)

-       (:optional ,@optional)
-       (:rest ,@rest)
-       (:keyword ,@keyword)))
+        (:optional ,@optional)
+        (:rest ,@rest)
+        (:keyword ,@keyword)
+        (:more ,@more)))

      (symbol
       (aver (eq ,element :deleted))
       ,@deleted)))
      (symbol
       (aver (eq ,element :deleted))
       ,@deleted)))

@@ -511,87 +457,166 @@ Other commands:
   (let ((var (gensym)))
     `(let ((,var ,variable))
        (cond ((eq ,var :deleted) ,deleted)
   (let ((var (gensym)))
     `(let ((,var ,variable))
        (cond ((eq ,var :deleted) ,deleted)

-            ((eq (sb!di:debug-var-validity ,var ,location) :valid)
-             ,valid)
-            (t ,other)))))
+             ((eq (sb!di:debug-var-validity ,var ,location) :valid)
+              ,valid)
+             (t ,other)))))

 
 ) ; EVAL-WHEN
 
 
 ) ; EVAL-WHEN
 

-;;; This is used in constructing arg lists for debugger printing when
-;;; the arg list is unavailable, some arg is unavailable or unused, etc.
-(defstruct (unprintable-object
-           (:constructor make-unprintable-object (string))
-           (:print-object (lambda (x s)
-                            (print-unreadable-object (x s)
-                              (write-string (unprintable-object-string x)
-                                            s))))
-           (:copier nil))
-  string)
-

 ;;; Extract the function argument values for a debug frame.
 ;;; Extract the function argument values for a debug frame.

-(defun frame-args-as-list (frame)
-  (let ((debug-fun (sb!di:frame-debug-fun frame))
-       (loc (sb!di:frame-code-location frame))
-       (reversed-result nil))
-    (handler-case
-       (progn
-         (dolist (ele (sb!di:debug-fun-lambda-list debug-fun))
-           (lambda-list-element-dispatch ele
-            :required ((push (frame-call-arg ele loc frame) reversed-result))
-            :optional ((push (frame-call-arg (second ele) loc frame)
-                             reversed-result))
-            :keyword ((push (second ele) reversed-result)
-                      (push (frame-call-arg (third ele) loc frame)
-                            reversed-result))
-            :deleted ((push (frame-call-arg ele loc frame) reversed-result))
-            :rest ((lambda-var-dispatch (second ele) loc
-                    nil
-                    (progn
-                      (setf reversed-result
-                            (append (reverse (sb!di:debug-var-value
-                                              (second ele) frame))
-                                    reversed-result))
-                      (return))
-                    (push (make-unprintable-object
-                           "unavailable &REST argument")
-                    reversed-result)))))
-         ;; As long as we do an ordinary return (as opposed to SIGNALing
-         ;; a CONDITION) from the DOLIST above:
-         (nreverse reversed-result))
-      (sb!di:lambda-list-unavailable
-       ()
-       (make-unprintable-object "unavailable lambda list")))))
-
-;;; Print FRAME with verbosity level 1. If we hit a &REST arg, then
-;;; print as many of the values as possible, punting the loop over
-;;; lambda-list variables since any other arguments will be in the
-;;; &REST arg's list of values.
-(defun print-frame-call-1 (frame)
+(defun map-frame-args (thunk frame)

   (let ((debug-fun (sb!di:frame-debug-fun frame)))
   (let ((debug-fun (sb!di:frame-debug-fun frame)))

+    (dolist (element (sb!di:debug-fun-lambda-list debug-fun))
+      (funcall thunk element))))

 
 

-    (pprint-logical-block (*standard-output* nil :prefix "(" :suffix ")")
-      (let ((args (ensure-printable-object (frame-args-as-list frame))))
-       ;; Since we go to some trouble to make nice informative function
-       ;; names like (PRINT-OBJECT :AROUND (CLOWN T)), let's make sure
-       ;; that they aren't truncated by *PRINT-LENGTH* and *PRINT-LEVEL*.
-       (let ((*print-length* nil)
-             (*print-level* nil))
-         (prin1 (ensure-printable-object (sb!di:debug-fun-name debug-fun))))
-       ;; For the function arguments, we can just print normally.
-        (if (listp args)
-            (format t "~{ ~_~S~}" args)
-            (format t " ~S" args))))
-
-    (when (sb!di:debug-fun-kind debug-fun)
-      (write-char #\[)
-      (prin1 (sb!di:debug-fun-kind debug-fun))
-      (write-char #\]))))
+(defun frame-args-as-list (frame)
+  (handler-case
+      (let ((location (sb!di:frame-code-location frame))
+            (reversed-result nil))
+        (block enumerating
+          (map-frame-args
+           (lambda (element)
+             (lambda-list-element-dispatch element
+               :required ((push (frame-call-arg element location frame) reversed-result))
+               :optional ((push (frame-call-arg (second element) location frame)
+                                reversed-result))
+               :keyword ((push (second element) reversed-result)
+                         (push (frame-call-arg (third element) location frame)
+                               reversed-result))
+               :deleted ((push (frame-call-arg element location frame) reversed-result))
+               :rest ((lambda-var-dispatch (second element) location
+                        nil
+                        (let ((rest (sb!di:debug-var-value (second element) frame)))
+                          (if (listp rest)
+                              (setf reversed-result (append (reverse rest) reversed-result))
+                              (push (make-unprintable-object "unavailable &REST argument")
+                                    reversed-result))
+                          (return-from enumerating))
+                        (push (make-unprintable-object
+                               "unavailable &REST argument")
+                              reversed-result)))
+              :more ((lambda-var-dispatch (second element) location
+                         nil
+                         (let ((context (sb!di:debug-var-value (second element) frame))
+                               (count (sb!di:debug-var-value (third element) frame)))
+                           (setf reversed-result
+                                 (append (reverse
+                                          (multiple-value-list
+                                           (sb!c::%more-arg-values context 0 count)))
+                                         reversed-result))
+                           (return-from enumerating))
+                         (push (make-unprintable-object "unavailable &MORE argument")
+                               reversed-result)))))
+           frame))
+        (nreverse reversed-result))
+    (sb!di:lambda-list-unavailable ()
+      (make-unprintable-object "unavailable lambda list"))))
+
+(defun clean-xep (name args info)
+  (values (second name)
+          (if (consp args)
+              (let* ((count (first args))
+                     (real-args (rest args)))
+                (if (fixnump count)
+                    ;; So, this is a cheap trick -- but makes backtraces for
+                    ;; too-many-arguments-errors much, much easier to to
+                    ;; understand. FIXME: For :EXTERNAL frames at least we
+                    ;; should be able to get the actual arguments, really.
+                    (loop repeat count
+                          for arg = (if real-args
+                                        (pop real-args)
+                                        (make-unprintable-object "unknown"))
+                          collect arg)
+                    real-args))
+              args)
+          (if (eq (car name) 'sb!c::tl-xep)
+              (cons :tl info)
+              info)))
+
+(defun clean-&more-processor (name args info)
+  (values (second name)
+          (if (consp args)
+              (let* ((more (last args 2))
+                     (context (first more))
+                     (count (second more)))
+                (append
+                 (butlast args 2)
+                 (if (fixnump count)
+                     (multiple-value-list
+                      (sb!c:%more-arg-values context 0 count))
+                     (list
+                      (make-unprintable-object "more unavailable arguments")))))
+              args)
+          (cons :more info)))
+
+(defun clean-fast-method (name args style info)
+  (multiple-value-bind (cname cargs)
+      (ecase style
+        (:minimal
+         (let ((gf-name (second name))
+               (real-args (cddr args)))
+           (if (and (fboundp gf-name)
+                    (notany #'sb!impl::unprintable-object-p real-args)
+                    (let ((methods (compute-applicable-methods
+                                    (fdefinition gf-name) real-args)))
+                      (and methods (not (cdr methods)))))
+               (values gf-name real-args)
+               (values (cons :method (cdr name)) real-args))))
+        (:normal
+         (values (cons :method (cdr name)) (cddr args)))
+        (:full
+         (values name args)))
+    (values cname cargs (cons :fast-method info))))
+
+(defun clean-frame-call (name args method-frame-style info)
+  (if (consp name)
+      (case (first name)
+        ((sb!c::xep sb!c::tl-xep)
+         (clean-xep name args info))
+        ((sb!c::&more-processor)
+         (clean-&more-processor name args info))
+        ((sb!c::&optional-processor)
+         (clean-frame-call (second name) args method-frame-style
+                           info))
+        ((sb!pcl::fast-method)
+         (clean-fast-method name args method-frame-style info))
+        (t
+         (values name args info)))
+      (values name args info)))
+
+(defun frame-call (frame &key (method-frame-style *method-frame-style*)
+                              replace-dynamic-extent-objects)
+  "Returns as multiple values a descriptive name for the function responsible
+for FRAME, arguments that that function, and a list providing additional
+information about the frame.
+
+Unavailable arguments are represented using dummy-objects printing as
+#<unavailable argument>.
+
+METHOD-FRAME-STYLE (defaulting to *METHOD-FRAME-STYLE*), determines how frames
+corresponding to method functions are printed. Possible values
+are :MINIMAL, :NORMAL, and :FULL. See *METHOD-FRAME-STYLE* for more
+information.
+
+If REPLACE-DYNAMIC-EXTENT-OBJECTS is true, objects allocated on the stack of
+the current thread are replaced with dummy objects which can safely escape."
+  (let* ((debug-fun (sb!di:frame-debug-fun frame))
+         (kind (sb!di:debug-fun-kind debug-fun)))
+    (multiple-value-bind (name args info)
+        (clean-frame-call (sb!di:debug-fun-name debug-fun)
+                          (frame-args-as-list frame)
+                          method-frame-style
+                          (when kind (list kind)))
+      (let ((args (if (and (consp args) replace-dynamic-extent-objects)
+                      (mapcar #'replace-dynamic-extent-object args)
+                      args)))
+        (values name args info)))))

 
 (defun ensure-printable-object (object)
   (handler-case
       (with-open-stream (out (make-broadcast-stream))
 
 (defun ensure-printable-object (object)
   (handler-case
       (with-open-stream (out (make-broadcast-stream))

-       (prin1 object out)
-       object)
+        (prin1 object out)
+        object)

     (error (cond)
       (declare (ignore cond))
       (make-unprintable-object "error printing object"))))
     (error (cond)
       (declare (ignore cond))
       (make-unprintable-object "error printing object"))))

@@ -607,25 +632,50 @@ Other commands:
 ;;; zero indicates just printing the DEBUG-FUN's name, and one
 ;;; indicates displaying call-like, one-liner format with argument
 ;;; values.
 ;;; zero indicates just printing the DEBUG-FUN's name, and one
 ;;; indicates displaying call-like, one-liner format with argument
 ;;; values.

-(defun print-frame-call (frame &key (verbosity 1) (number nil))
-  (cond
-   ((zerop verbosity)
-    (when number
-      (format t "~&~S: " (sb!di:frame-number frame)))
-    (format t "~S" frame))
-   (t
-    (when number
-      (format t "~&~S: " (sb!di:frame-number frame)))
-    (print-frame-call-1 frame)))
-  (when (>= verbosity 2)
+(defun print-frame-call (frame stream
+                         &key print-frame-source
+                              number
+                              (method-frame-style *method-frame-style*))
+  (when number
+    (format stream "~&~S: " (if (integerp number)
+                                number
+                                (sb!di:frame-number frame))))
+  (multiple-value-bind (name args info)
+      (frame-call frame :method-frame-style method-frame-style)
+    (pprint-logical-block (stream nil :prefix "(" :suffix ")")
+      ;; Since we go to some trouble to make nice informative function
+      ;; names like (PRINT-OBJECT :AROUND (CLOWN T)), let's make sure
+      ;; that they aren't truncated by *PRINT-LENGTH* and *PRINT-LEVEL*.
+      ;; For the function arguments, we can just print normally.
+      (let ((*print-length* nil)
+            (*print-level* nil)
+            (*print-pretty* nil)
+            (*print-circle* t)
+            (name (ensure-printable-object name)))
+        (write name :stream stream :escape t :pretty (equal '(lambda ()) name))
+        ;; If we hit a &REST arg, then print as many of the values as
+        ;; possible, punting the loop over lambda-list variables since any
+        ;; other arguments will be in the &REST arg's list of values.
+        (let ((args (ensure-printable-object args)))
+          (if (listp args)
+              (format stream "~{ ~_~S~}" args)
+              (format stream " ~S" args)))))
+    (when info
+      (format stream " [~{~(~A~)~^,~}]" info)))
+  (when print-frame-source

     (let ((loc (sb!di:frame-code-location frame)))
       (handler-case
     (let ((loc (sb!di:frame-code-location frame)))
       (handler-case

-         (progn
-           (sb!di:code-location-debug-block loc)
-           (format t "~%source: ")
-           (print-code-location-source-form loc 0))
-       (sb!di:debug-condition (ignore) ignore)
-       (error (c) (format t "error finding source: ~A" c))))))
+          (let ((source (handler-case
+                            (code-location-source-form loc 0)
+                          (error (c)
+                            (format stream "~&   error finding frame source: ~A" c)))))
+            (format stream "~%   source: ~S" source))
+        (sb!di:debug-condition ()
+          ;; This is mostly noise.
+          (when (eq :always print-frame-source)
+            (format stream "~&   no source available for frame")))
+        (error (c)
+          (format stream "~&   error printing frame source: ~A" c))))))

 \f
 ;;;; INVOKE-DEBUGGER
 
 \f
 ;;;; INVOKE-DEBUGGER
 

@@ -637,171 +687,358 @@ Other commands:
    of this variable to the function because it binds *DEBUGGER-HOOK* to NIL
    around the invocation.")
 
    of this variable to the function because it binds *DEBUGGER-HOOK* to NIL
    around the invocation.")
 

+(defvar *invoke-debugger-hook* nil
+  #!+sb-doc
+  "This is either NIL or a designator for a function of two arguments,
+   to be run when the debugger is about to be entered.  The function is
+   run with *INVOKE-DEBUGGER-HOOK* bound to NIL to minimize recursive
+   errors, and receives as arguments the condition that triggered
+   debugger entry and the previous value of *INVOKE-DEBUGGER-HOOK*
+
+   This mechanism is an SBCL extension similar to the standard *DEBUGGER-HOOK*.
+   In contrast to *DEBUGGER-HOOK*, it is observed by INVOKE-DEBUGGER even when
+   called by BREAK.")
+

 ;;; These are bound on each invocation of INVOKE-DEBUGGER.
 (defvar *debug-restarts*)
 (defvar *debug-condition*)
 (defvar *nested-debug-condition*)
 
 ;;; These are bound on each invocation of INVOKE-DEBUGGER.
 (defvar *debug-restarts*)
 (defvar *debug-condition*)
 (defvar *nested-debug-condition*)
 

+;;; Oh, what a tangled web we weave when we preserve backwards
+;;; compatibility with 1968-style use of global variables to control
+;;; per-stream i/o properties; there's really no way to get this
+;;; quite right, but we do what we can.
+(defun funcall-with-debug-io-syntax (fun &rest rest)
+  (declare (type function fun))
+  ;; Try to force the other special variables into a useful state.
+  (let (;; Protect from WITH-STANDARD-IO-SYNTAX some variables where
+        ;; any default we might use is less useful than just reusing
+        ;; the global values.
+        (original-package *package*)
+        (original-print-pretty *print-pretty*))
+    (with-standard-io-syntax
+      (with-sane-io-syntax
+          (let (;; We want the printer and reader to be in a useful
+                ;; state, regardless of where the debugger was invoked
+                ;; in the program. WITH-STANDARD-IO-SYNTAX and
+                ;; WITH-SANE-IO-SYNTAX do much of what we want, but
+                ;;   * It doesn't affect our internal special variables
+                ;;     like *CURRENT-LEVEL-IN-PRINT*.
+                ;;   * It isn't customizable.
+                ;;   * It sets *PACKAGE* to COMMON-LISP-USER, which is not
+                ;;     helpful behavior for a debugger.
+                ;;   * There's no particularly good debugger default for
+                ;;     *PRINT-PRETTY*, since T is usually what you want
+                ;;     -- except absolutely not what you want when you're
+                ;;     debugging failures in PRINT-OBJECT logic.
+                ;; We try to address all these issues with explicit
+                ;; rebindings here.
+                (sb!kernel:*current-level-in-print* 0)
+                (*package* original-package)
+                (*print-pretty* original-print-pretty)
+                ;; Clear the circularity machinery to try to to reduce the
+                ;; pain from sharing the circularity table across all
+                ;; streams; if these are not rebound here, then setting
+                ;; *PRINT-CIRCLE* within the debugger when debugging in a
+                ;; state where something circular was being printed (e.g.,
+                ;; because the debugger was entered on an error in a
+                ;; PRINT-OBJECT method) makes a hopeless mess. Binding them
+                ;; here does seem somewhat ugly because it makes it more
+                ;; difficult to debug the printing-of-circularities code
+                ;; itself; however, as far as I (WHN, 2004-05-29) can see,
+                ;; that's almost entirely academic as long as there's one
+                ;; shared *C-H-T* for all streams (i.e., it's already
+                ;; unreasonably difficult to debug print-circle machinery
+                ;; given the buggy crosstalk between the debugger streams
+                ;; and the stream you're trying to watch), and any fix for
+                ;; that buggy arrangement will likely let this hack go away
+                ;; naturally.
+                (sb!impl::*circularity-hash-table* . nil)
+                (sb!impl::*circularity-counter* . nil)
+                (*readtable* *debug-readtable*))
+            (progv
+                ;; (Why NREVERSE? PROGV makes the later entries have
+                ;; precedence over the earlier entries.
+                ;; *DEBUG-PRINT-VARIABLE-ALIST* is called an alist, so it's
+                ;; expected that its earlier entries have precedence. And
+                ;; the earlier-has-precedence behavior is mostly more
+                ;; convenient, so that programmers can use PUSH or LIST* to
+                ;; customize *DEBUG-PRINT-VARIABLE-ALIST*.)
+                (nreverse (mapcar #'car *debug-print-variable-alist*))
+                (nreverse (mapcar #'cdr *debug-print-variable-alist*))
+              (apply fun rest)))))))
+
+;;; This function is not inlined so it shows up in the backtrace; that
+;;; can be rather handy when one has to debug the interplay between
+;;; *INVOKE-DEBUGGER-HOOK* and *DEBUGGER-HOOK*.
+(declaim (notinline run-hook))
+(defun run-hook (variable condition)
+  (let ((old-hook (symbol-value variable)))
+    (when old-hook
+      (progv (list variable) (list nil)
+        (funcall old-hook condition old-hook)))))
+
+;;; We can bind *stack-top-hint* to a symbol, in which case this function will
+;;; resolve that hint lazily before we enter the debugger.
+(defun resolve-stack-top-hint ()
+  (let ((hint *stack-top-hint*)
+        (*stack-top-hint* nil))
+    (cond
+      ;; No hint, just keep the debugger guts out.
+      ((not hint)
+       (find-caller-name-and-frame))
+      ;; Interrupted. Look for the interrupted frame -- if we don't find one
+      ;; this falls back to the next case.
+      ((and (eq hint 'invoke-interruption)
+            (nth-value 1 (find-interrupted-name-and-frame))))
+      ;; Name of the first uninteresting frame.
+      ((symbolp hint)
+       (find-caller-of-named-frame hint))
+      ;; We already have a resolved hint.
+      (t
+       hint))))
+

 (defun invoke-debugger (condition)
   #!+sb-doc
   "Enter the debugger."
 (defun invoke-debugger (condition)
   #!+sb-doc
   "Enter the debugger."

-  (let ((old-hook *debugger-hook*))
-    (when old-hook
-      (let ((*debugger-hook* nil))
-       (funcall old-hook condition old-hook))))
-
-  ;; Note: CMU CL had (SB-UNIX:UNIX-SIGSETMASK 0) here. I deleted it
-  ;; around sbcl-0.7.8.5 (by which time it had mutated to have a
-  ;; #!-SUNOS prefix and a FIXME note observing that it wasn't needed
-  ;; on SunOS and no one knew why it was needed anywhere else either).
-  ;; So if something mysteriously breaks that has worked since the CMU
-  ;; CL days, that might be why. -- WHN 2002-09-28
-
-  ;; We definitely want *PACKAGE* to be of valid type.
-  ;;
-  ;; Elsewhere in the system, we use the SANE-PACKAGE function for
-  ;; this, but here causing an exception just as we're trying to handle
-  ;; an exception would be confusing, so instead we use a special hack.
-  (unless (and (packagep *package*)
-              (package-name *package*))
-    (setf *package* (find-package :cl-user))
-    (format *error-output*
-           "The value of ~S was not an undeleted PACKAGE. It has been
-reset to ~S."
-           '*package* *package*))

 
 

-  ;; Try to force the other special variables into a useful state.
-  (let (;; Protect from WITH-STANDARD-IO-SYNTAX some variables where
-       ;; any default we might use is less useful than just reusing
-       ;; the global values.
-       (original-package *package*)
-       (original-print-pretty *print-pretty*))
-    (with-standard-io-syntax
-     (let ((*debug-condition* condition)
-          (*debug-restarts* (compute-restarts condition))
-          (*nested-debug-condition* nil)
-          ;; We want the printer and reader to be in a useful state,
-          ;; regardless of where the debugger was invoked in the
-          ;; program. WITH-STANDARD-IO-SYNTAX did much of what we
-          ;; want, but
-          ;;   * It doesn't affect our internal special variables 
-          ;;     like *CURRENT-LEVEL-IN-PRINT*.
-          ;;   * It isn't customizable.
-          ;;   * It doesn't set *PRINT-READABLY* to the same value
-          ;;     as the toplevel default.
-          ;;   * It sets *PACKAGE* to COMMON-LISP-USER, which is not
-          ;;     helpful behavior for a debugger.
-          ;;   * There's no particularly good debugger default for
-          ;;     *PRINT-PRETTY*, since T is usually what you want
-          ;;     -- except absolutely not what you want when you're
-          ;;     debugging failures in PRINT-OBJECT logic.
-          ;; We try to address all these issues with explicit
-          ;; rebindings here.
-          (sb!kernel:*current-level-in-print* 0)
-          (*print-length* *debug-print-length*)
-          (*print-level* *debug-print-level*)
-          (*readtable* *debug-readtable*)
-          (*print-readably* nil)
-          (*package* original-package)
-          (*print-pretty* original-print-pretty))
-
-       ;; Before we start our own output, finish any pending output.
-       ;; Otherwise, if the user tried to track the progress of his
-       ;; program using PRINT statements, he'd tend to lose the last
-       ;; line of output or so, which'd be confusing.
-       (flush-standard-output-streams)
-
-       ;; (The initial output here goes to *ERROR-OUTPUT*, because the
-       ;; initial output is not interactive, just an error message,
-       ;; and when people redirect *ERROR-OUTPUT*, they could
-       ;; reasonably expect to see error messages logged there,
-       ;; regardless of what the debugger does afterwards.)
-       (handler-case
-          (format *error-output*
-                  "~2&~@<debugger invoked on condition of type ~S: ~
-                    ~2I~_~A~:>~%"
-                  (type-of *debug-condition*)
-                  *debug-condition*)
-        (error (condition)
-           (setf *nested-debug-condition* condition)
-          (let ((ndc-type (type-of *nested-debug-condition*)))
-            (format *error-output*
-                    "~&~@<(A ~S was caught when trying to print ~S when ~
+  (let ((*stack-top-hint* (resolve-stack-top-hint)))
+
+    ;; call *INVOKE-DEBUGGER-HOOK* first, so that *DEBUGGER-HOOK* is not
+    ;; called when the debugger is disabled
+    (run-hook '*invoke-debugger-hook* condition)
+    (run-hook '*debugger-hook* condition)
+
+    ;; We definitely want *PACKAGE* to be of valid type.
+    ;;
+    ;; Elsewhere in the system, we use the SANE-PACKAGE function for
+    ;; this, but here causing an exception just as we're trying to handle
+    ;; an exception would be confusing, so instead we use a special hack.
+    (unless (and (packagep *package*)
+                 (package-name *package*))
+      (setf *package* (find-package :cl-user))
+      (format *error-output*
+              "The value of ~S was not an undeleted PACKAGE. It has been
+reset to ~S."
+              '*package* *package*))
+
+    ;; Before we start our own output, finish any pending output.
+    ;; Otherwise, if the user tried to track the progress of his program
+    ;; using PRINT statements, he'd tend to lose the last line of output
+    ;; or so, which'd be confusing.
+    (flush-standard-output-streams)
+
+    (funcall-with-debug-io-syntax #'%invoke-debugger condition)))
+
+(defun %print-debugger-invocation-reason (condition stream)
+  (format stream "~2&")
+  ;; Note: Ordinarily it's only a matter of taste whether to use
+  ;; FORMAT "~<...~:>" or to use PPRINT-LOGICAL-BLOCK directly, but
+  ;; until bug 403 is fixed, PPRINT-LOGICAL-BLOCK (STREAM NIL) is
+  ;; definitely preferred, because the FORMAT alternative was acting odd.
+  (pprint-logical-block (stream nil)
+    (format stream
+            "debugger invoked on a ~S~@[ in thread ~_~A~]: ~2I~_~A"
+            (type-of condition)
+            #!+sb-thread sb!thread:*current-thread*
+            #!-sb-thread nil
+            condition))
+  (terpri stream))
+
+(defun %invoke-debugger (condition)
+  (let ((*debug-condition* condition)
+        (*debug-restarts* (compute-restarts condition))
+        (*nested-debug-condition* nil))
+    (handler-case
+        ;; (The initial output here goes to *ERROR-OUTPUT*, because the
+        ;; initial output is not interactive, just an error message, and
+        ;; when people redirect *ERROR-OUTPUT*, they could reasonably
+        ;; expect to see error messages logged there, regardless of what
+        ;; the debugger does afterwards.)
+        (unless (typep condition 'step-condition)
+          (%print-debugger-invocation-reason condition *error-output*))
+      (error (condition)
+        (setf *nested-debug-condition* condition)
+        (let ((ndc-type (type-of *nested-debug-condition*)))
+          (format *error-output*
+                  "~&~@<(A ~S was caught when trying to print ~S when ~

                       entering the debugger. Printing was aborted and the ~
                       ~S was stored in ~S.)~@:>~%"
                       entering the debugger. Printing was aborted and the ~
                       ~S was stored in ~S.)~@:>~%"

-                    ndc-type
-                    '*debug-condition*
-                    ndc-type
-                    '*nested-debug-condition*))
-          (when (typep condition 'cell-error)
-            ;; what we really want to know when it's e.g. an UNBOUND-VARIABLE:
-            (format *error-output*
-                    "~&(CELL-ERROR-NAME ~S) = ~S~%"
-                    '*debug-condition*
-                    (cell-error-name *debug-condition*)))))
-
-       ;; After the initial error/condition/whatever announcement to
-       ;; *ERROR-OUTPUT*, we become interactive, and should talk on
-       ;; *DEBUG-IO* from now on. (KLUDGE: This is a normative
-       ;; statement, not a description of reality.:-| There's a lot of
-       ;; older debugger code which was written to do i/o on whatever
-       ;; stream was in fashion at the time, and not all of it has
-       ;; been converted to behave this way. -- WHN 2000-11-16)
-       (let (;; FIXME: Rebinding *STANDARD-OUTPUT* here seems wrong,
-            ;; violating the principle of least surprise, and making
-            ;; it impossible for the user to do reasonable things
-            ;; like using PRINT at the debugger prompt to send output
-            ;; to the program's ordinary (possibly
-            ;; redirected-to-a-file) *STANDARD-OUTPUT*. (CMU CL
-            ;; used to rebind *STANDARD-INPUT* here too, but that's
-            ;; been fixed already.)
-            (*standard-output* *debug-io*)
-            ;; This seems reasonable: e.g. if the user has redirected
-            ;; *ERROR-OUTPUT* to some log file, it's probably wrong
-            ;; to send errors which occur in interactive debugging to
-            ;; that file, and right to send them to *DEBUG-IO*.
-            (*error-output* *debug-io*))
-        (unless (typep condition 'step-condition)
-          (when *debug-beginner-help-p*
-            (format *debug-io*
-                    "~%~@<Within the debugger, you can type HELP for help. ~
-                      At any command prompt (within the debugger or not) you ~
-                      can type (SB-EXT:QUIT) to terminate the SBCL ~
-                      executable. The condition which caused the debugger to ~
-                      be entered is bound to ~S. You can suppress this ~
-                      message by clearing ~S.~:@>~2%"
-                    '*debug-condition*
-                    '*debug-beginner-help-p*))
-          (show-restarts *debug-restarts* *debug-io*))
-        (internal-debug))))))
+                  ndc-type
+                  '*debug-condition*
+                  ndc-type
+                  '*nested-debug-condition*))
+        (when (typep *nested-debug-condition* 'cell-error)
+          ;; what we really want to know when it's e.g. an UNBOUND-VARIABLE:
+          (format *error-output*
+                  "~&(CELL-ERROR-NAME ~S) = ~S~%"
+                  '*nested-debug-condition*
+                  (cell-error-name *nested-debug-condition*)))))
+
+    (let ((background-p (sb!thread::debugger-wait-until-foreground-thread
+                         *debug-io*)))
+
+      ;; After the initial error/condition/whatever announcement to
+      ;; *ERROR-OUTPUT*, we become interactive, and should talk on
+      ;; *DEBUG-IO* from now on. (KLUDGE: This is a normative
+      ;; statement, not a description of reality.:-| There's a lot of
+      ;; older debugger code which was written to do i/o on whatever
+      ;; stream was in fashion at the time, and not all of it has
+      ;; been converted to behave this way. -- WHN 2000-11-16)
+
+      (unwind-protect
+           (let (;; We used to bind *STANDARD-OUTPUT* to *DEBUG-IO*
+                 ;; here as well, but that is probably bogus since it
+                 ;; removes the users ability to do output to a redirected
+                 ;; *S-O*. Now we just rebind it so that users can temporarily
+                 ;; frob it. FIXME: This and other "what gets bound when"
+                 ;; behaviour should be documented in the manual.
+                 (*standard-output* *standard-output*)
+                 ;; This seems reasonable: e.g. if the user has redirected
+                 ;; *ERROR-OUTPUT* to some log file, it's probably wrong
+                 ;; to send errors which occur in interactive debugging to
+                 ;; that file, and right to send them to *DEBUG-IO*.
+                 (*error-output* *debug-io*))
+             (unless (typep condition 'step-condition)
+               (when *debug-beginner-help-p*
+                 (format *debug-io*
+                         "~%~@<Type HELP for debugger help, or ~
+                               (SB-EXT:EXIT) to exit from SBCL.~:@>~2%"))
+               (show-restarts *debug-restarts* *debug-io*))
+             (internal-debug))
+        (when background-p
+          (sb!thread::release-foreground))))))
+
+;;; this function is for use in *INVOKE-DEBUGGER-HOOK* when ordinary
+;;; ANSI behavior has been suppressed by the "--disable-debugger"
+;;; command-line option
+(defun debugger-disabled-hook (condition me)
+  (declare (ignore me))
+  ;; There is no one there to interact with, so report the
+  ;; condition and terminate the program.
+  (flet ((failure-quit (&key abort)
+           (/show0 "in FAILURE-QUIT (in --disable-debugger debugger hook)")
+           (exit :code 1 :abort abort)))
+    ;; This HANDLER-CASE is here mostly to stop output immediately
+    ;; (and fall through to QUIT) when there's an I/O error. Thus,
+    ;; when we're run under a shell script or something, we can die
+    ;; cleanly when the script dies (and our pipes are cut), instead
+    ;; of falling into ldb or something messy like that. Similarly, we
+    ;; can terminate cleanly even if BACKTRACE dies because of bugs in
+    ;; user PRINT-OBJECT methods.
+    (handler-case
+        (progn
+          (format *error-output*
+                  "~&~@<unhandled ~S~@[ in thread ~S~]: ~2I~_~A~:>~2%"
+                  (type-of condition)
+                  #!+sb-thread sb!thread:*current-thread*
+                  #!-sb-thread nil
+                  condition)
+          ;; Flush *ERROR-OUTPUT* even before the BACKTRACE, so that
+          ;; even if we hit an error within BACKTRACE (e.g. a bug in
+          ;; the debugger's own frame-walking code, or a bug in a user
+          ;; PRINT-OBJECT method) we'll at least have the CONDITION
+          ;; printed out before we die.
+          (finish-output *error-output*)
+          ;; (Where to truncate the BACKTRACE is of course arbitrary, but
+          ;; it seems as though we should at least truncate it somewhere.)
+          (print-backtrace :count 128 :stream *error-output*
+                           :from :interrupted-frame)
+          (format
+           *error-output*
+           "~%unhandled condition in --disable-debugger mode, quitting~%")
+          (finish-output *error-output*)
+          (failure-quit))
+      (condition ()
+        ;; We IGNORE-ERRORS here because even %PRIMITIVE PRINT can
+        ;; fail when our output streams are blown away, as e.g. when
+        ;; we're running under a Unix shell script and it dies somehow
+        ;; (e.g. because of a SIGINT). In that case, we might as well
+        ;; just give it up for a bad job, and stop trying to notify
+        ;; the user of anything.
+        ;;
+        ;; Actually, the only way I've run across to exercise the
+        ;; problem is to have more than one layer of shell script.
+        ;; I have a shell script which does
+        ;;   time nice -10 sh make.sh "$1" 2>&1 | tee make.tmp
+        ;; and the problem occurs when I interrupt this with Ctrl-C
+        ;; under Linux 2.2.14-5.0 and GNU bash, version 1.14.7(1).
+        ;; I haven't figured out whether it's bash, time, tee, Linux, or
+        ;; what that is responsible, but that it's possible at all
+        ;; means that we should IGNORE-ERRORS here. -- WHN 2001-04-24
+        (ignore-errors
+         (%primitive print
+                     "Argh! error within --disable-debugger error handling"))
+        (failure-quit :abort t)))))
+
+(defvar *old-debugger-hook* nil)
+
+;;; halt-on-failures and prompt-on-failures modes, suitable for
+;;; noninteractive and interactive use respectively
+(defun disable-debugger ()
+  "When invoked, this function will turn off both the SBCL debugger
+and LDB (the low-level debugger).  See also ENABLE-DEBUGGER."
+  ;; *DEBUG-IO* used to be set here to *ERROR-OUTPUT* which is sort
+  ;; of unexpected but mostly harmless, but then ENABLE-DEBUGGER had
+  ;; to set it to a suitable value again and be very careful,
+  ;; especially if the user has also set it. -- MG 2005-07-15
+  (unless (eq *invoke-debugger-hook* 'debugger-disabled-hook)
+    (setf *old-debugger-hook* *invoke-debugger-hook*
+          *invoke-debugger-hook* 'debugger-disabled-hook))
+  ;; This is not inside the UNLESS to ensure that LDB is disabled
+  ;; regardless of what the old value of *INVOKE-DEBUGGER-HOOK* was.
+  ;; This might matter for example when restoring a core.
+  (sb!alien:alien-funcall (sb!alien:extern-alien "disable_lossage_handler"
+                                                 (function sb!alien:void))))
+
+(defun enable-debugger ()
+  "Restore the debugger if it has been turned off by DISABLE-DEBUGGER."
+  (when (eql *invoke-debugger-hook* 'debugger-disabled-hook)
+    (setf *invoke-debugger-hook* *old-debugger-hook*
+          *old-debugger-hook* nil))
+  (sb!alien:alien-funcall (sb!alien:extern-alien "enable_lossage_handler"
+                                                 (function sb!alien:void))))

 
 (defun show-restarts (restarts s)
   (cond ((null restarts)
 
 (defun show-restarts (restarts s)
   (cond ((null restarts)

-        (format s
-                "~&(no restarts: If you didn't do this on purpose, ~
+         (format s
+                 "~&(no restarts: If you didn't do this on purpose, ~

                   please report it as a bug.)~%"))
                   please report it as a bug.)~%"))

-       (t
-        (format s "~&restarts:~%")
-        (let ((count 0)
-              (names-used '(nil))
-              (max-name-len 0))
-          (dolist (restart restarts)
-            (let ((name (restart-name restart)))
-              (when name
-                (let ((len (length (princ-to-string name))))
-                  (when (> len max-name-len)
-                    (setf max-name-len len))))))
-          (unless (zerop max-name-len)
-            (incf max-name-len 3))
-          (dolist (restart restarts)
-            (let ((name (restart-name restart)))
-              (cond ((member name names-used)
-                     (format s "~& ~2D: ~V@T~A~%" count max-name-len restart))
-                    (t
-                     (format s "~& ~2D: [~VA] ~A~%"
-                             count (- max-name-len 3) name restart)
-                     (push name names-used))))
-            (incf count))))))
+        (t
+         (format s "~&restarts (invokable by number or by ~
+                    possibly-abbreviated name):~%")
+         (let ((count 0)
+               (names-used '(nil))
+               (max-name-len 0))
+           (dolist (restart restarts)
+             (let ((name (restart-name restart)))
+               (when name
+                 (let ((len (length (princ-to-string name))))
+                   (when (> len max-name-len)
+                     (setf max-name-len len))))))
+           (unless (zerop max-name-len)
+             (incf max-name-len 3))
+           (dolist (restart restarts)
+             (let ((name (restart-name restart)))
+               ;; FIXME: maybe it would be better to display later names
+               ;; in parens instead of brakets, not just omit them fully.
+               ;; Call BREAK, call BREAK in the debugger, and tell me
+               ;; it's not confusing looking. --NS 20050310
+               (cond ((member name names-used)
+                      (format s "~& ~2D: ~V@T~A~%" count max-name-len restart))
+                     (t
+                      (format s "~& ~2D: [~VA] ~A~%"
+                              count (- max-name-len 3) name restart)
+                      (push name names-used))))
+             (incf count))))))
+
+(defvar *debug-loop-fun* #'debug-loop-fun
+  "a function taking no parameters that starts the low-level debug loop")
+
+;;; When the debugger is invoked due to a stepper condition, we don't
+;;; want to print the current frame before the first prompt for aesthetic
+;;; reasons.
+(defvar *suppress-frame-print* nil)

 
 ;;; This calls DEBUG-LOOP, performing some simple initializations
 ;;; before doing so. INVOKE-DEBUGGER calls this to actually get into
 
 ;;; This calls DEBUG-LOOP, performing some simple initializations
 ;;; before doing so. INVOKE-DEBUGGER calls this to actually get into

@@ -811,10 +1048,11 @@ reset to ~S."
 ;;; errors.
 (defun internal-debug ()
   (let ((*in-the-debugger* t)
 ;;; errors.
 (defun internal-debug ()
   (let ((*in-the-debugger* t)

-       (*read-suppress* nil))
+        (*read-suppress* nil))

     (unless (typep *debug-condition* 'step-condition)
       (clear-input *debug-io*))
     (unless (typep *debug-condition* 'step-condition)
       (clear-input *debug-io*))

-    (debug-loop)))
+    (let ((*suppress-frame-print* (typep *debug-condition* 'step-condition)))
+      (funcall *debug-loop-fun*))))

 \f
 ;;;; DEBUG-LOOP
 
 \f
 ;;;; DEBUG-LOOP
 

@@ -825,91 +1063,93 @@ reset to ~S."
   "When set, avoid calling INVOKE-DEBUGGER recursively when errors occur while
    executing in the debugger.")
 
   "When set, avoid calling INVOKE-DEBUGGER recursively when errors occur while
    executing in the debugger.")
 

-(defun debug-loop ()
+(defun debug-read (stream eof-restart)
+  (declare (type stream stream))
+  (let* ((eof-marker (cons nil nil))
+         (form (read stream nil eof-marker)))
+    (if (eq form eof-marker)
+        (invoke-restart eof-restart)
+        form)))
+
+(defun debug-loop-fun ()

   (let* ((*debug-command-level* (1+ *debug-command-level*))
   (let* ((*debug-command-level* (1+ *debug-command-level*))

-        (*real-stack-top* (sb!di:top-frame))
-        (*stack-top* (or *stack-top-hint* *real-stack-top*))
-        (*stack-top-hint* nil)
-        (*current-frame* *stack-top*))
+         (*real-stack-top* (sb!di:top-frame))
+         (*stack-top* (or *stack-top-hint* *real-stack-top*))
+         (*stack-top-hint* nil)
+         (*current-frame* *stack-top*))

     (handler-bind ((sb!di:debug-condition
     (handler-bind ((sb!di:debug-condition

-                   (lambda (condition)
-                     (princ condition *debug-io*)
-                     (/show0 "handling d-c by THROWing DEBUG-LOOP-CATCHER")
-                     (throw 'debug-loop-catcher nil))))
-      (fresh-line)
-      (print-frame-call *current-frame* :verbosity 2)
+                    (lambda (condition)
+                      (princ condition *debug-io*)
+                      (/show0 "handling d-c by THROWing DEBUG-LOOP-CATCHER")
+                      (throw 'debug-loop-catcher nil))))
+      (cond (*suppress-frame-print*
+             (setf *suppress-frame-print* nil))
+            (t
+             (terpri *debug-io*)
+             (print-frame-call *current-frame* *debug-io* :print-frame-source t)))

       (loop
       (loop

-       (catch 'debug-loop-catcher
-         (handler-bind ((error (lambda (condition)
-                                 (when *flush-debug-errors*
-                                   (clear-input *debug-io*)
-                                   (princ condition)
-                                   ;; FIXME: Doing input on *DEBUG-IO*
-                                   ;; and output on T seems broken.
-                                   (format t
-                                           "~&error flushed (because ~
-                                            ~S is set)"
-                                           '*flush-debug-errors*)
-                                   (/show0 "throwing DEBUG-LOOP-CATCHER")
-                                   (throw 'debug-loop-catcher nil)))))
-           ;; We have to bind LEVEL for the restart function created by
-           ;; WITH-SIMPLE-RESTART.
-           (let ((level *debug-command-level*)
-                 (restart-commands (make-restart-commands)))
-             (with-simple-restart (abort
-                                  "~@<Reduce debugger level (to debug level ~W).~@:>"
-                                   level)
-               (debug-prompt *debug-io*)
-               (force-output *debug-io*)
-               (let ((input (sb!int:get-stream-command *debug-io*)))
-                 (cond (input
-                        (let ((cmd-fun (debug-command-p
-                                        (sb!int:stream-command-name input)
-                                        restart-commands)))
-                          (cond
-                           ((not cmd-fun)
-                            (error "unknown stream-command: ~S" input))
-                           ((consp cmd-fun)
-                            (error "ambiguous debugger command: ~S" cmd-fun))
-                           (t
-                            (apply cmd-fun
-                                   (sb!int:stream-command-args input))))))
-                       (t
-                        (let* ((exp (read *debug-io*))
-                               (cmd-fun (debug-command-p exp
-                                                         restart-commands)))
-                          (cond ((not cmd-fun)
-                                 (debug-eval-print exp))
-                                ((consp cmd-fun)
-                                 (format t
-                                         "~&Your command, ~S, is ambiguous:~%"
-                                         exp)
-                                 (dolist (ele cmd-fun)
-                                   (format t "   ~A~%" ele)))
-                                (t
-                                 (funcall cmd-fun)))))))))))))))
-
-;;; FIXME: We could probably use INTERACTIVE-EVAL for much of this logic.
+       (catch 'debug-loop-catcher
+         (handler-bind ((error (lambda (condition)
+                                 (when *flush-debug-errors*
+                                   (clear-input *debug-io*)
+                                   (princ condition *debug-io*)
+                                   (format *debug-io*
+                                           "~&error flushed (because ~
+                                             ~S is set)"
+                                           '*flush-debug-errors*)
+                                   (/show0 "throwing DEBUG-LOOP-CATCHER")
+                                   (throw 'debug-loop-catcher nil)))))
+           ;; We have to bind LEVEL for the restart function created
+           ;; by WITH-SIMPLE-RESTART, and we need the explicit ABORT
+           ;; restart that exists now so that EOF from read can drop
+           ;; one debugger level.
+           (let ((level *debug-command-level*)
+                 (restart-commands (make-restart-commands))
+                 (abort-restart-for-eof (find-restart 'abort)))
+             (flush-standard-output-streams)
+             (debug-prompt *debug-io*)
+             (force-output *debug-io*)
+             (with-simple-restart (abort
+                                   "~@<Reduce debugger level (to debug level ~W).~@:>"
+                                   level)
+               (let* ((exp (debug-read *debug-io* abort-restart-for-eof))
+                      (cmd-fun (debug-command-p exp restart-commands)))
+                 (cond ((not cmd-fun)
+                        (debug-eval-print exp))
+                       ((consp cmd-fun)
+                        (format *debug-io*
+                                "~&Your command, ~S, is ambiguous:~%"
+                                exp)
+                        (dolist (ele cmd-fun)
+                          (format *debug-io* "   ~A~%" ele)))
+                       (t
+                        (funcall cmd-fun))))))))))))
+
+(defvar *auto-eval-in-frame* t
+  #!+sb-doc
+  "When set (the default), evaluations in the debugger's command loop occur
+   relative to the current frame's environment without the need of debugger
+   forms that explicitly control this kind of evaluation.")
+
+(defun debug-eval (expr)
+  (cond ((not (and (fboundp 'compile) *auto-eval-in-frame*))
+         (eval expr))
+        ((frame-has-debug-vars-p *current-frame*)
+         (sb!di:eval-in-frame *current-frame* expr))
+        (t
+         (format *debug-io* "; No debug variables for current frame: ~
+                               using EVAL instead of EVAL-IN-FRAME.~%")
+         (eval expr))))
+

 (defun debug-eval-print (expr)
   (/noshow "entering DEBUG-EVAL-PRINT" expr)
 (defun debug-eval-print (expr)
   (/noshow "entering DEBUG-EVAL-PRINT" expr)

-  (/noshow (fboundp 'compile))
-  (setq +++ ++ ++ + + - - expr)
-  (let* ((values (multiple-value-list (eval -)))
-        (*standard-output* *debug-io*))
+  (let ((values (multiple-value-list
+                 (interactive-eval expr :eval #'debug-eval))))

     (/noshow "done with EVAL in DEBUG-EVAL-PRINT")
     (/noshow "done with EVAL in DEBUG-EVAL-PRINT")

-    (fresh-line)
-    (if values (prin1 (car values)))
-    (dolist (x (cdr values))
-      (fresh-line)
-      (prin1 x))
-    (setq /// // // / / values)
-    (setq *** ** ** * * (car values))
-    ;; Make sure that nobody passes back an unbound marker.
-    (unless (boundp '*)
-      (setq * nil)
-      (fresh-line)
-      ;; FIXME: The way INTERACTIVE-EVAL does this seems better.
-      (princ "Setting * to NIL (was unbound marker)."))))
+    (dolist (value values)
+      (fresh-line *debug-io*)
+      (prin1 value *debug-io*)))
+  (force-output *debug-io*))

 \f
 ;;;; debug loop functions
 
 \f
 ;;;; debug loop functions
 

@@ -920,85 +1160,85 @@ reset to ~S."
 
 (sb!xc:defmacro define-var-operation (ref-or-set &optional value-var)
   `(let* ((temp (etypecase name
 
 (sb!xc:defmacro define-var-operation (ref-or-set &optional value-var)
   `(let* ((temp (etypecase name

-                 (symbol (sb!di:debug-fun-symbol-vars
-                          (sb!di:frame-debug-fun *current-frame*)
-                          name))
-                 (simple-string (sb!di:ambiguous-debug-vars
-                                 (sb!di:frame-debug-fun *current-frame*)
-                                 name))))
-         (location (sb!di:frame-code-location *current-frame*))
-         ;; Let's only deal with valid variables.
-         (vars (remove-if-not (lambda (v)
-                                (eq (sb!di:debug-var-validity v location)
-                                    :valid))
-                              temp)))
+                  (symbol (sb!di:debug-fun-symbol-vars
+                           (sb!di:frame-debug-fun *current-frame*)
+                           name))
+                  (simple-string (sb!di:ambiguous-debug-vars
+                                  (sb!di:frame-debug-fun *current-frame*)
+                                  name))))
+          (location (sb!di:frame-code-location *current-frame*))
+          ;; Let's only deal with valid variables.
+          (vars (remove-if-not (lambda (v)
+                                 (eq (sb!di:debug-var-validity v location)
+                                     :valid))
+                               temp)))

      (declare (list vars))
      (cond ((null vars)
      (declare (list vars))
      (cond ((null vars)

-           (error "No known valid variables match ~S." name))
-          ((= (length vars) 1)
-           ,(ecase ref-or-set
-              (:ref
-               '(sb!di:debug-var-value (car vars) *current-frame*))
-              (:set
-               `(setf (sb!di:debug-var-value (car vars) *current-frame*)
-                      ,value-var))))
-          (t
-           ;; Since we have more than one, first see whether we have
-           ;; any variables that exactly match the specification.
-           (let* ((name (etypecase name
-                          (symbol (symbol-name name))
-                          (simple-string name)))
-                  ;; FIXME: REMOVE-IF-NOT is deprecated, use STRING/=
-                  ;; instead.
-                  (exact (remove-if-not (lambda (v)
-                                          (string= (sb!di:debug-var-symbol-name v)
-                                                   name))
-                                        vars))
-                  (vars (or exact vars)))
-             (declare (simple-string name)
-                      (list exact vars))
-             (cond
-              ;; Check now for only having one variable.
-              ((= (length vars) 1)
-               ,(ecase ref-or-set
-                  (:ref
-                   '(sb!di:debug-var-value (car vars) *current-frame*))
-                  (:set
-                   `(setf (sb!di:debug-var-value (car vars) *current-frame*)
-                          ,value-var))))
-              ;; If there weren't any exact matches, flame about
-              ;; ambiguity unless all the variables have the same
-              ;; name.
-              ((and (not exact)
-                    (find-if-not
-                     (lambda (v)
-                       (string= (sb!di:debug-var-symbol-name v)
-                                (sb!di:debug-var-symbol-name (car vars))))
-                     (cdr vars)))
-               (error "specification ambiguous:~%~{   ~A~%~}"
-                      (mapcar #'sb!di:debug-var-symbol-name
-                              (delete-duplicates
-                               vars :test #'string=
-                               :key #'sb!di:debug-var-symbol-name))))
-              ;; All names are the same, so see whether the user
-              ;; ID'ed one of them.
-              (id-supplied
-               (let ((v (find id vars :key #'sb!di:debug-var-id)))
-                 (unless v
-                   (error
-                    "invalid variable ID, ~W: should have been one of ~S"
-                    id
-                    (mapcar #'sb!di:debug-var-id vars)))
-                 ,(ecase ref-or-set
-                    (:ref
-                     '(sb!di:debug-var-value v *current-frame*))
-                    (:set
-                     `(setf (sb!di:debug-var-value v *current-frame*)
-                            ,value-var)))))
-              (t
-               (error "Specify variable ID to disambiguate ~S. Use one of ~S."
-                      name
-                      (mapcar #'sb!di:debug-var-id vars)))))))))
+            (error "No known valid variables match ~S." name))
+           ((= (length vars) 1)
+            ,(ecase ref-or-set
+               (:ref
+                '(sb!di:debug-var-value (car vars) *current-frame*))
+               (:set
+                `(setf (sb!di:debug-var-value (car vars) *current-frame*)
+                       ,value-var))))
+           (t
+            ;; Since we have more than one, first see whether we have
+            ;; any variables that exactly match the specification.
+            (let* ((name (etypecase name
+                           (symbol (symbol-name name))
+                           (simple-string name)))
+                   ;; FIXME: REMOVE-IF-NOT is deprecated, use STRING/=
+                   ;; instead.
+                   (exact (remove-if-not (lambda (v)
+                                           (string= (sb!di:debug-var-symbol-name v)
+                                                    name))
+                                         vars))
+                   (vars (or exact vars)))
+              (declare (simple-string name)
+                       (list exact vars))
+              (cond
+               ;; Check now for only having one variable.
+               ((= (length vars) 1)
+                ,(ecase ref-or-set
+                   (:ref
+                    '(sb!di:debug-var-value (car vars) *current-frame*))
+                   (:set
+                    `(setf (sb!di:debug-var-value (car vars) *current-frame*)
+                           ,value-var))))
+               ;; If there weren't any exact matches, flame about
+               ;; ambiguity unless all the variables have the same
+               ;; name.
+               ((and (not exact)
+                     (find-if-not
+                      (lambda (v)
+                        (string= (sb!di:debug-var-symbol-name v)
+                                 (sb!di:debug-var-symbol-name (car vars))))
+                      (cdr vars)))
+                (error "specification ambiguous:~%~{   ~A~%~}"
+                       (mapcar #'sb!di:debug-var-symbol-name
+                               (delete-duplicates
+                                vars :test #'string=
+                                :key #'sb!di:debug-var-symbol-name))))
+               ;; All names are the same, so see whether the user
+               ;; ID'ed one of them.
+               (id-supplied
+                (let ((v (find id vars :key #'sb!di:debug-var-id)))
+                  (unless v
+                    (error
+                     "invalid variable ID, ~W: should have been one of ~S"
+                     id
+                     (mapcar #'sb!di:debug-var-id vars)))
+                  ,(ecase ref-or-set
+                     (:ref
+                      '(sb!di:debug-var-value v *current-frame*))
+                     (:set
+                      `(setf (sb!di:debug-var-value v *current-frame*)
+                             ,value-var)))))
+               (t
+                (error "Specify variable ID to disambiguate ~S. Use one of ~S."
+                       name
+                       (mapcar #'sb!di:debug-var-id vars)))))))))

 
 ) ; EVAL-WHEN
 
 
 ) ; EVAL-WHEN
 

@@ -1038,28 +1278,28 @@ reset to ~S."
 (defun nth-arg (count args)
   (let ((n count))
     (dolist (ele args (error "The argument specification ~S is out of range."
 (defun nth-arg (count args)
   (let ((n count))
     (dolist (ele args (error "The argument specification ~S is out of range."

-                            n))
+                             n))

       (lambda-list-element-dispatch ele
       (lambda-list-element-dispatch ele

-       :required ((if (zerop n) (return (values ele t))))
-       :optional ((if (zerop n) (return (values (second ele) t))))
-       :keyword ((cond ((zerop n)
-                        (return (values (second ele) nil)))
-                       ((zerop (decf n))
-                        (return (values (third ele) t)))))
-       :deleted ((if (zerop n) (return (values ele t))))
-       :rest ((let ((var (second ele)))
-                (lambda-var-dispatch var (sb!di:frame-code-location
-                                          *current-frame*)
-                  (error "unused &REST argument before n'th argument")
-                  (dolist (value
-                           (sb!di:debug-var-value var *current-frame*)
-                           (error
-                            "The argument specification ~S is out of range."
-                            n))
-                    (if (zerop n)
-                        (return-from nth-arg (values value nil))
-                        (decf n)))
-                  (error "invalid &REST argument before n'th argument")))))
+        :required ((if (zerop n) (return (values ele t))))
+        :optional ((if (zerop n) (return (values (second ele) t))))
+        :keyword ((cond ((zerop n)
+                         (return (values (second ele) nil)))
+                        ((zerop (decf n))
+                         (return (values (third ele) t)))))
+        :deleted ((if (zerop n) (return (values ele t))))
+        :rest ((let ((var (second ele)))
+                 (lambda-var-dispatch var (sb!di:frame-code-location
+                                           *current-frame*)
+                   (error "unused &REST argument before n'th argument")
+                   (dolist (value
+                            (sb!di:debug-var-value var *current-frame*)
+                            (error
+                             "The argument specification ~S is out of range."
+                             n))
+                     (if (zerop n)
+                         (return-from nth-arg (values value nil))
+                         (decf n)))
+                   (error "invalid &REST argument before n'th argument")))))

       (decf n))))
 
 (defun arg (n)
       (decf n))))
 
 (defun arg (n)

@@ -1069,15 +1309,15 @@ reset to ~S."
    pairs as separate arguments."
   (multiple-value-bind (var lambda-var-p)
       (nth-arg n (handler-case (sb!di:debug-fun-lambda-list
    pairs as separate arguments."
   (multiple-value-bind (var lambda-var-p)
       (nth-arg n (handler-case (sb!di:debug-fun-lambda-list

-                               (sb!di:frame-debug-fun *current-frame*))
-                  (sb!di:lambda-list-unavailable ()
-                    (error "No argument values are available."))))
+                                (sb!di:frame-debug-fun *current-frame*))
+                   (sb!di:lambda-list-unavailable ()
+                     (error "No argument values are available."))))

     (if lambda-var-p
     (if lambda-var-p

-       (lambda-var-dispatch var (sb!di:frame-code-location *current-frame*)
-         (error "Unused arguments have no values.")
-         (sb!di:debug-var-value var *current-frame*)
-         (error "invalid argument value"))
-       var)))
+        (lambda-var-dispatch var (sb!di:frame-code-location *current-frame*)
+          (error "Unused arguments have no values.")
+          (sb!di:debug-var-value var *current-frame*)
+          (error "invalid argument value"))
+        var)))

 \f
 ;;;; machinery for definition of debug loop commands
 
 \f
 ;;;; machinery for definition of debug loop commands
 

@@ -1089,11 +1329,11 @@ reset to ~S."
   (let ((fun-name (symbolicate name "-DEBUG-COMMAND")))
     `(progn
        (setf *debug-commands*
   (let ((fun-name (symbolicate name "-DEBUG-COMMAND")))
     `(progn
        (setf *debug-commands*

-            (remove ,name *debug-commands* :key #'car :test #'string=))
+             (remove ,name *debug-commands* :key #'car :test #'string=))

        (defun ,fun-name ,args
        (defun ,fun-name ,args

-        (unless *in-the-debugger*
-          (error "invoking debugger command while outside the debugger"))
-        ,@body)
+         (unless *in-the-debugger*
+           (error "invoking debugger command while outside the debugger"))
+         ,@body)

        (push (cons ,name #',fun-name) *debug-commands*)
        ',fun-name)))
 
        (push (cons ,name #',fun-name) *debug-commands*)
        ',fun-name)))
 

@@ -1113,38 +1353,38 @@ reset to ~S."
 (defun debug-command-p (form &optional other-commands)
   (if (or (symbolp form) (integerp form))
       (let* ((name
 (defun debug-command-p (form &optional other-commands)
   (if (or (symbolp form) (integerp form))
       (let* ((name

-             (if (symbolp form)
-                 (symbol-name form)
-                 (format nil "~W" form)))
-            (len (length name))
-            (res nil))
-       (declare (simple-string name)
-                (fixnum len)
-                (list res))
-
-       ;; Find matching commands, punting if exact match.
-       (flet ((match-command (ele)
-                (let* ((str (car ele))
-                       (str-len (length str)))
-                  (declare (simple-string str)
-                           (fixnum str-len))
-                  (cond ((< str-len len))
-                        ((= str-len len)
-                         (when (string= name str :end1 len :end2 len)
-                           (return-from debug-command-p (cdr ele))))
-                        ((string= name str :end1 len :end2 len)
-                         (push ele res))))))
-         (mapc #'match-command *debug-commands*)
-         (mapc #'match-command other-commands))
-
-       ;; Return the right value.
-       (cond ((not res) nil)
-             ((= (length res) 1)
-              (cdar res))
-             (t ; Just return the names.
-              (do ((cmds res (cdr cmds)))
-                  ((not cmds) res)
-                (setf (car cmds) (caar cmds))))))))
+              (if (symbolp form)
+                  (symbol-name form)
+                  (format nil "~W" form)))
+             (len (length name))
+             (res nil))
+        (declare (simple-string name)
+                 (fixnum len)
+                 (list res))
+
+        ;; Find matching commands, punting if exact match.
+        (flet ((match-command (ele)
+                 (let* ((str (car ele))
+                        (str-len (length str)))
+                   (declare (simple-string str)
+                            (fixnum str-len))
+                   (cond ((< str-len len))
+                         ((= str-len len)
+                          (when (string= name str :end1 len :end2 len)
+                            (return-from debug-command-p (cdr ele))))
+                         ((string= name str :end1 len :end2 len)
+                          (push ele res))))))
+          (mapc #'match-command *debug-commands*)
+          (mapc #'match-command other-commands))
+
+        ;; Return the right value.
+        (cond ((not res) nil)
+              ((= (length res) 1)
+               (cdar res))
+              (t ; Just return the names.
+               (do ((cmds res (cdr cmds)))
+                   ((not cmds) res)
+                 (setf (car cmds) (caar cmds))))))))

 
 ;;; Return a list of debug commands (in the same format as
 ;;; *DEBUG-COMMANDS*) that invoke each active restart.
 
 ;;; Return a list of debug commands (in the same format as
 ;;; *DEBUG-COMMANDS*) that invoke each active restart.

@@ -1154,15 +1394,15 @@ reset to ~S."
 ;;; restart of the same name, or it is NIL).
 (defun make-restart-commands (&optional (restarts *debug-restarts*))
   (let ((commands)
 ;;; restart of the same name, or it is NIL).
 (defun make-restart-commands (&optional (restarts *debug-restarts*))
   (let ((commands)

-       (num 0))                        ; better be the same as show-restarts!
+        (num 0))                        ; better be the same as show-restarts!

     (dolist (restart restarts)
       (let ((name (string (restart-name restart))))
         (let ((restart-fun
                 (lambda ()
     (dolist (restart restarts)
       (let ((name (string (restart-name restart))))
         (let ((restart-fun
                 (lambda ()

-                 (/show0 "in restart-command closure, about to i-r-i")
-                 (invoke-restart-interactively restart))))
+                  (/show0 "in restart-command closure, about to i-r-i")
+                  (invoke-restart-interactively restart))))

           (push (cons (prin1-to-string num) restart-fun) commands)
           (push (cons (prin1-to-string num) restart-fun) commands)

-          (unless (or (null (restart-name restart)) 
+          (unless (or (null (restart-name restart))

                       (find name commands :key #'car :test #'string=))
             (push (cons name restart-fun) commands))))
     (incf num))
                       (find name commands :key #'car :test #'string=))
             (push (cons name restart-fun) commands))))
     (incf num))

@@ -1173,107 +1413,84 @@ reset to ~S."
 (!def-debug-command "UP" ()
   (let ((next (sb!di:frame-up *current-frame*)))
     (cond (next
 (!def-debug-command "UP" ()
   (let ((next (sb!di:frame-up *current-frame*)))
     (cond (next

-          (setf *current-frame* next)
-          (print-frame-call next))
-         (t
-          (format t "~&Top of stack.")))))
+           (setf *current-frame* next)
+           (print-frame-call next *debug-io*))
+          (t
+           (format *debug-io* "~&Top of stack.")))))

 
 (!def-debug-command "DOWN" ()
   (let ((next (sb!di:frame-down *current-frame*)))
     (cond (next
 
 (!def-debug-command "DOWN" ()
   (let ((next (sb!di:frame-down *current-frame*)))
     (cond (next

-          (setf *current-frame* next)
-          (print-frame-call next))
-         (t
-          (format t "~&Bottom of stack.")))))
+           (setf *current-frame* next)
+           (print-frame-call next *debug-io*))
+          (t
+           (format *debug-io* "~&Bottom of stack.")))))

 
 (!def-debug-command-alias "D" "DOWN")
 
 
 (!def-debug-command-alias "D" "DOWN")
 

-;;; CMU CL had this command, but SBCL doesn't, since it's redundant
-;;; with "FRAME 0", and it interferes with abbreviations for the
-;;; TOPLEVEL restart.
-;;;(!def-debug-command "TOP" ()
-;;;  (do ((prev *current-frame* lead)
-;;;       (lead (sb!di:frame-up *current-frame*) (sb!di:frame-up lead)))
-;;;      ((null lead)
-;;;       (setf *current-frame* prev)
-;;;       (print-frame-call prev))))
-

 (!def-debug-command "BOTTOM" ()
   (do ((prev *current-frame* lead)
        (lead (sb!di:frame-down *current-frame*) (sb!di:frame-down lead)))
       ((null lead)
        (setf *current-frame* prev)
 (!def-debug-command "BOTTOM" ()
   (do ((prev *current-frame* lead)
        (lead (sb!di:frame-down *current-frame*) (sb!di:frame-down lead)))
       ((null lead)
        (setf *current-frame* prev)

-       (print-frame-call prev))))
+       (print-frame-call prev *debug-io*))))

 
 (!def-debug-command-alias "B" "BOTTOM")
 
 (!def-debug-command "FRAME" (&optional
 
 (!def-debug-command-alias "B" "BOTTOM")
 
 (!def-debug-command "FRAME" (&optional

-                            (n (read-prompting-maybe "frame number: ")))
+                             (n (read-prompting-maybe "frame number: ")))

   (setf *current-frame*
   (setf *current-frame*

-       (multiple-value-bind (next-frame-fun limit-string)
-           (if (< n (sb!di:frame-number *current-frame*))
-               (values #'sb!di:frame-up "top")
-             (values #'sb!di:frame-down "bottom"))
-         (do ((frame *current-frame*))
-             ((= n (sb!di:frame-number frame))
-              frame)
-           (let ((next-frame (funcall next-frame-fun frame)))
-             (cond (next-frame
-                    (setf frame next-frame))
-                   (t
-                    (format t
-                            "The ~A of the stack was encountered.~%"
-                            limit-string)
-                    (return frame)))))))
-  (print-frame-call *current-frame*))
+        (multiple-value-bind (next-frame-fun limit-string)
+            (if (< n (sb!di:frame-number *current-frame*))
+                (values #'sb!di:frame-up "top")
+              (values #'sb!di:frame-down "bottom"))
+          (do ((frame *current-frame*))
+              ((= n (sb!di:frame-number frame))
+               frame)
+            (let ((next-frame (funcall next-frame-fun frame)))
+              (cond (next-frame
+                     (setf frame next-frame))
+                    (t
+                     (format *debug-io*
+                             "The ~A of the stack was encountered.~%"
+                             limit-string)
+                     (return frame)))))))
+  (print-frame-call *current-frame* *debug-io*))

 
 (!def-debug-command-alias "F" "FRAME")
 \f
 ;;;; commands for entering and leaving the debugger
 
 
 (!def-debug-command-alias "F" "FRAME")
 \f
 ;;;; commands for entering and leaving the debugger
 

-;;; CMU CL supported this QUIT debug command, but SBCL provides this
-;;; functionality with a restart instead. (The QUIT debug command was
-;;; removed because it's confusing to have "quit" mean two different
-;;; things in the system, "restart the top level REPL" in the debugger
-;;; and "terminate the Lisp system" as the SB-EXT:QUIT function.)
-;;;
-;;;(!def-debug-command "QUIT" ()
-;;;  (throw 'sb!impl::toplevel-catcher nil))
+(!def-debug-command "TOPLEVEL" ()
+  (throw 'toplevel-catcher nil))

 
 

-;;; CMU CL supported this GO debug command, but SBCL doesn't -- in
-;;; SBCL you just type the CONTINUE restart name instead (or "C" or
-;;; "RESTART CONTINUE", that's OK too).
-;;;(!def-debug-command "GO" ()
-;;;  (continue *debug-condition*)
-;;;  (error "There is no restart named CONTINUE."))
+;;; make T safe
+(!def-debug-command-alias "TOP" "TOPLEVEL")

 
 (!def-debug-command "RESTART" ()
   (/show0 "doing RESTART debug-command")
   (let ((num (read-if-available :prompt)))
     (when (eq num :prompt)
       (show-restarts *debug-restarts* *debug-io*)
 
 (!def-debug-command "RESTART" ()
   (/show0 "doing RESTART debug-command")
   (let ((num (read-if-available :prompt)))
     (when (eq num :prompt)
       (show-restarts *debug-restarts* *debug-io*)

-      (write-string "restart: ")
-      (force-output)
+      (write-string "restart: " *debug-io*)
+      (force-output *debug-io*)

       (setf num (read *debug-io*)))
     (let ((restart (typecase num
       (setf num (read *debug-io*)))
     (let ((restart (typecase num

-                    (unsigned-byte
-                     (nth num *debug-restarts*))
-                    (symbol
-                     (find num *debug-restarts* :key #'restart-name
-                           :test (lambda (sym1 sym2)
-                                   (string= (symbol-name sym1)
-                                            (symbol-name sym2)))))
-                    (t
-                     (format t "~S is invalid as a restart name.~%" num)
-                     (return-from restart-debug-command nil)))))
+                     (unsigned-byte
+                      (nth num *debug-restarts*))
+                     (symbol
+                      (find num *debug-restarts* :key #'restart-name
+                            :test (lambda (sym1 sym2)
+                                    (string= (symbol-name sym1)
+                                             (symbol-name sym2)))))
+                     (t
+                      (format *debug-io* "~S is invalid as a restart name.~%"
+                              num)
+                      (return-from restart-debug-command nil)))))

       (/show0 "got RESTART")
       (if restart
       (/show0 "got RESTART")
       (if restart

-         (invoke-restart-interactively restart)
-         ;; FIXME: Even if this isn't handled by WARN, it probably
-         ;; shouldn't go to *STANDARD-OUTPUT*, but *ERROR-OUTPUT* or
-         ;; *QUERY-IO* or something. Look through this file to
-         ;; straighten out stream usage.
-         (princ "There is no such restart.")))))
+          (invoke-restart-interactively restart)
+          (princ "There is no such restart." *debug-io*)))))

 \f
 ;;;; information commands
 
 \f
 ;;;; information commands
 

@@ -1284,9 +1501,9 @@ reset to ~S."
   ;; desperate holdout is running this on a dumb terminal somewhere,
   ;; we tell him where to find the message stored as a string.
   (format *debug-io*
   ;; desperate holdout is running this on a dumb terminal somewhere,
   ;; we tell him where to find the message stored as a string.
   (format *debug-io*

-         "~&~A~2%(The HELP string is stored in ~S.)~%"
-         *debug-help-string*
-         '*debug-help-string*))
+          "~&~A~2%(The HELP string is stored in ~S.)~%"
+          *debug-help-string*
+          '*debug-help-string*))

 
 (!def-debug-command-alias "?" "HELP")
 
 
 (!def-debug-command-alias "?" "HELP")
 

@@ -1295,408 +1512,305 @@ reset to ~S."
   (show-restarts *debug-restarts* *debug-io*))
 
 (!def-debug-command "BACKTRACE" ()
   (show-restarts *debug-restarts* *debug-io*))
 
 (!def-debug-command "BACKTRACE" ()

-  (backtrace (read-if-available most-positive-fixnum)))
+ (print-backtrace :count (read-if-available most-positive-fixnum)))

 
 (!def-debug-command "PRINT" ()
 
 (!def-debug-command "PRINT" ()

-  (print-frame-call *current-frame*))
+  (print-frame-call *current-frame* *debug-io*))

 
 (!def-debug-command-alias "P" "PRINT")
 
 (!def-debug-command "LIST-LOCALS" ()
   (let ((d-fun (sb!di:frame-debug-fun *current-frame*)))
     (if (sb!di:debug-var-info-available d-fun)
 
 (!def-debug-command-alias "P" "PRINT")
 
 (!def-debug-command "LIST-LOCALS" ()
   (let ((d-fun (sb!di:frame-debug-fun *current-frame*)))
     (if (sb!di:debug-var-info-available d-fun)

-       (let ((*standard-output* *debug-io*)
-             (location (sb!di:frame-code-location *current-frame*))
-             (prefix (read-if-available nil))
-             (any-p nil)
-             (any-valid-p nil))
-         (dolist (v (sb!di:ambiguous-debug-vars
-                       d-fun
-                       (if prefix (string prefix) "")))
-           (setf any-p t)
-           (when (eq (sb!di:debug-var-validity v location) :valid)
-             (setf any-valid-p t)
-             (format t "~S~:[#~W~;~*~]  =  ~S~%"
-                     (sb!di:debug-var-symbol v)
-                     (zerop (sb!di:debug-var-id v))
-                     (sb!di:debug-var-id v)
-                     (sb!di:debug-var-value v *current-frame*))))
-
-         (cond
-          ((not any-p)
-           (format t "There are no local variables ~@[starting with ~A ~]~
-                      in the function."
-                   prefix))
-          ((not any-valid-p)
-           (format t "All variables ~@[starting with ~A ~]currently ~
-                      have invalid values."
-                   prefix))))
-       (write-line "There is no variable information available."))))
+        (let ((*standard-output* *debug-io*)
+              (location (sb!di:frame-code-location *current-frame*))
+              (prefix (read-if-available nil))
+              (any-p nil)
+              (any-valid-p nil)
+              (more-context nil)
+              (more-count nil))
+          (dolist (v (sb!di:ambiguous-debug-vars
+                      d-fun
+                      (if prefix (string prefix) "")))
+            (setf any-p t)
+            (when (eq (sb!di:debug-var-validity v location) :valid)
+              (setf any-valid-p t)
+              (case (sb!di::debug-var-info v)
+                (:more-context
+                 (setf more-context (sb!di:debug-var-value v *current-frame*)))
+                (:more-count
+                 (setf more-count (sb!di:debug-var-value v *current-frame*))))
+              (format *debug-io* "~S~:[#~W~;~*~]  =  ~S~%"
+                      (sb!di:debug-var-symbol v)
+                      (zerop (sb!di:debug-var-id v))
+                      (sb!di:debug-var-id v)
+                      (sb!di:debug-var-value v *current-frame*))))
+          (when (and more-context more-count)
+            (format *debug-io* "~S  =  ~S~%"
+                    'more
+                    (multiple-value-list (sb!c:%more-arg-values more-context 0 more-count))))
+          (cond
+           ((not any-p)
+            (format *debug-io*
+                    "There are no local variables ~@[starting with ~A ~]~
+                    in the function."
+                    prefix))
+           ((not any-valid-p)
+            (format *debug-io*
+                    "All variables ~@[starting with ~A ~]currently ~
+                    have invalid values."
+                    prefix))))
+        (write-line "There is no variable information available."
+                    *debug-io*))))

 
 (!def-debug-command-alias "L" "LIST-LOCALS")
 
 (!def-debug-command "SOURCE" ()
 
 (!def-debug-command-alias "L" "LIST-LOCALS")
 
 (!def-debug-command "SOURCE" ()

-  (fresh-line)
-  (print-code-location-source-form (sb!di:frame-code-location *current-frame*)
-                                  (read-if-available 0)))
+  (print (code-location-source-form (sb!di:frame-code-location *current-frame*)
+                                    (read-if-available 0))
+         *debug-io*))

 \f
 ;;;; source location printing
 
 \f
 ;;;; source location printing
 

-;;; We cache a stream to the last valid file debug source so that we
-;;; won't have to repeatedly open the file.
-;;;
-;;; KLUDGE: This sounds like a bug, not a feature. Opening files is fast
-;;; in the 1990s, so the benefit is negligible, less important than the
-;;; potential of extra confusion if someone changes the source during
-;;; a debug session and the change doesn't show up. And removing this
-;;; would simplify the system, which I like. -- WHN 19990903
-(defvar *cached-debug-source* nil)
-(declaim (type (or sb!di:debug-source null) *cached-debug-source*))
-(defvar *cached-source-stream* nil)
-(declaim (type (or stream null) *cached-source-stream*))
-
-;;; To suppress the read-time evaluation #. macro during source read,
-;;; *READTABLE* is modified. *READTABLE* is cached to avoid
-;;; copying it each time, and invalidated when the
-;;; *CACHED-DEBUG-SOURCE* has changed.
-(defvar *cached-readtable* nil)
-(declaim (type (or readtable null) *cached-readtable*))
-
-(pushnew (lambda ()
-          (setq *cached-debug-source* nil *cached-source-stream* nil
-                *cached-readtable* nil))
-        *before-save-initializations*)
-
-;;; We also cache the last toplevel form that we printed a source for
-;;; so that we don't have to do repeated reads and calls to
-;;; FORM-NUMBER-TRANSLATIONS.
-(defvar *cached-toplevel-form-offset* nil)
-(declaim (type (or index null) *cached-toplevel-form-offset*))
-(defvar *cached-toplevel-form*)
-(defvar *cached-form-number-translations*)
-
-;;; Given a code location, return the associated form-number
-;;; translations and the actual top level form. We check our cache ---
-;;; if there is a miss, we dispatch on the kind of the debug source.
-(defun get-toplevel-form (location)
-  (let ((d-source (sb!di:code-location-debug-source location)))
-    (if (and (eq d-source *cached-debug-source*)
-            (eql (sb!di:code-location-toplevel-form-offset location)
-                 *cached-toplevel-form-offset*))
-       (values *cached-form-number-translations* *cached-toplevel-form*)
-       (let* ((offset (sb!di:code-location-toplevel-form-offset location))
-              (res
-               (ecase (sb!di:debug-source-from d-source)
-                 (:file (get-file-toplevel-form location))
-                 (:lisp (svref (sb!di:debug-source-name d-source) offset)))))
-         (setq *cached-toplevel-form-offset* offset)
-         (values (setq *cached-form-number-translations*
-                       (sb!di:form-number-translations res offset))
-                 (setq *cached-toplevel-form* res))))))
-
-;;; Locate the source file (if it still exists) and grab the top level
-;;; form. If the file is modified, we use the top level form offset
-;;; instead of the recorded character offset.
-(defun get-file-toplevel-form (location)
-  (let* ((d-source (sb!di:code-location-debug-source location))
-        (tlf-offset (sb!di:code-location-toplevel-form-offset location))
-        (local-tlf-offset (- tlf-offset
-                             (sb!di:debug-source-root-number d-source)))
-        (char-offset
-         (aref (or (sb!di:debug-source-start-positions d-source)
-                   (error "no start positions map"))
-               local-tlf-offset))
-        (name (sb!di:debug-source-name d-source)))
-    (unless (eq d-source *cached-debug-source*)
-      (unless (and *cached-source-stream*
-                  (equal (pathname *cached-source-stream*)
-                         (pathname name)))
-       (setq *cached-readtable* nil)
-       (when *cached-source-stream* (close *cached-source-stream*))
-       (setq *cached-source-stream* (open name :if-does-not-exist nil))
-       (unless *cached-source-stream*
-         (error "The source file no longer exists:~%  ~A" (namestring name)))
-       (format t "~%; file: ~A~%" (namestring name)))
-
-       (setq *cached-debug-source*
-             (if (= (sb!di:debug-source-created d-source)
-                    (file-write-date name))
-                 d-source nil)))
-
-    (cond
-     ((eq *cached-debug-source* d-source)
-      (file-position *cached-source-stream* char-offset))
-     (t
-      (format t "~%; File has been modified since compilation:~%;   ~A~@
-                ; Using form offset instead of character position.~%"
-             (namestring name))
-      (file-position *cached-source-stream* 0)
-      (let ((*read-suppress* t))
-       (dotimes (i local-tlf-offset)
-         (read *cached-source-stream*)))))
-    (unless *cached-readtable*
-      (setq *cached-readtable* (copy-readtable))
-      (set-dispatch-macro-character
-       #\# #\.
-       (lambda (stream sub-char &rest rest)
-        (declare (ignore rest sub-char))
-        (let ((token (read stream t nil t)))
-          (format nil "#.~S" token)))
-       *cached-readtable*))
-    (let ((*readtable* *cached-readtable*))
-      (read *cached-source-stream*))))
-
-(defun print-code-location-source-form (location context)
-  (let* ((location (maybe-block-start-location location))
-        (form-num (sb!di:code-location-form-number location)))
-    (multiple-value-bind (translations form) (get-toplevel-form location)
-      (unless (< form-num (length translations))
-       (error "The source path no longer exists."))
-      (prin1 (sb!di:source-path-context form
-                                       (svref translations form-num)
-                                       context)))))
-\f
-;;; breakpoint and step commands
-
-;;; Step to the next code-location.
-(!def-debug-command "STEP" ()
-  (setf *number-of-steps* (read-if-available 1))
-  (set-step-breakpoint *current-frame*)
-  (continue *debug-condition*)
-  (error "couldn't continue"))
-
-;;; List possible breakpoint locations, which ones are active, and
-;;; where the CONTINUE restart will transfer control. Set
-;;; *POSSIBLE-BREAKPOINTS* to the code-locations which can then be
-;;; used by sbreakpoint.
-(!def-debug-command "LIST-LOCATIONS" ()
-  (let ((df (read-if-available *default-breakpoint-debug-fun*)))
-    (cond ((consp df)
-          (setf df (sb!di:fun-debug-fun (eval df)))
-          (setf *default-breakpoint-debug-fun* df))
-         ((or (eq ':c df)
-              (not *default-breakpoint-debug-fun*))
-          (setf df (sb!di:frame-debug-fun *current-frame*))
-          (setf *default-breakpoint-debug-fun* df)))
-    (setf *possible-breakpoints* (possible-breakpoints df)))
-  (let ((continue-at (sb!di:frame-code-location *current-frame*)))
-    (let ((active (location-in-list *default-breakpoint-debug-fun*
-                                   *breakpoints* :fun-start))
-         (here (sb!di:code-location=
-                (sb!di:debug-fun-start-location
-                 *default-breakpoint-debug-fun*) continue-at)))
-      (when (or active here)
-       (format t "::FUN-START ")
-       (when active (format t " *Active*"))
-       (when here (format t " *Continue here*"))))
-
-    (let ((prev-location nil)
-         (prev-num 0)
-         (this-num 0))
-      (flet ((flush ()
-              (when prev-location
-                (let ((this-num (1- this-num)))
-                  (if (= prev-num this-num)
-                      (format t "~&~W: " prev-num)
-                      (format t "~&~W-~W: " prev-num this-num)))
-                (print-code-location-source-form prev-location 0)
-                (when *print-location-kind*
-                  (format t "~S " (sb!di:code-location-kind prev-location)))
-                (when (location-in-list prev-location *breakpoints*)
-                  (format t " *Active*"))
-                (when (sb!di:code-location= prev-location continue-at)
-                  (format t " *Continue here*")))))
-       
-       (dolist (code-location *possible-breakpoints*)
-         (when (or *print-location-kind*
-                   (location-in-list code-location *breakpoints*)
-                   (sb!di:code-location= code-location continue-at)
-                   (not prev-location)
-                   (not (eq (sb!di:code-location-debug-source code-location)
-                            (sb!di:code-location-debug-source prev-location)))
-                   (not (eq (sb!di:code-location-toplevel-form-offset
-                             code-location)
-                            (sb!di:code-location-toplevel-form-offset
-                             prev-location)))
-                   (not (eq (sb!di:code-location-form-number code-location)
-                            (sb!di:code-location-form-number prev-location))))
-           (flush)
-           (setq prev-location code-location  prev-num this-num))
-
-         (incf this-num))))
-
-    (when (location-in-list *default-breakpoint-debug-fun*
-                           *breakpoints*
-                           :fun-end)
-      (format t "~&::FUN-END *Active* "))))
-
-(!def-debug-command-alias "LL" "LIST-LOCATIONS")
-
-;;; Set breakpoint at the given number.
-(!def-debug-command "BREAKPOINT" ()
-  (let ((index (read-prompting-maybe "location number, :START, or :END: "))
-       (break t)
-       (condition t)
-       (print nil)
-       (print-functions nil)
-       (function nil)
-       (bp)
-       (place *default-breakpoint-debug-fun*))
-    (flet ((get-command-line ()
-            (let ((command-line nil)
-                  (unique '(nil)))
-              (loop
-                (let ((next-input (read-if-available unique)))
-                  (when (eq next-input unique) (return))
-                  (push next-input command-line)))
-              (nreverse command-line)))
-          (set-vars-from-command-line (command-line)
-            (do ((arg (pop command-line) (pop command-line)))
-                ((not arg))
-              (ecase arg
-                (:condition (setf condition (pop command-line)))
-                (:print (push (pop command-line) print))
-                (:break (setf break (pop command-line)))
-                (:function
-                 (setf function (eval (pop command-line)))
-                 (setf *default-breakpoint-debug-fun*
-                       (sb!di:fun-debug-fun function))
-                 (setf place *default-breakpoint-debug-fun*)
-                 (setf *possible-breakpoints*
-                       (possible-breakpoints
-                        *default-breakpoint-debug-fun*))))))
-          (setup-fun-start ()
-            (let ((code-loc (sb!di:debug-fun-start-location place)))
-              (setf bp (sb!di:make-breakpoint #'main-hook-fun
-                                              place
-                                              :kind :fun-start))
-              (setf break (sb!di:preprocess-for-eval break code-loc))
-              (setf condition (sb!di:preprocess-for-eval condition code-loc))
-              (dolist (form print)
-                (push (cons (sb!di:preprocess-for-eval form code-loc) form)
-                      print-functions))))
-          (setup-fun-end ()
-            (setf bp
-                  (sb!di:make-breakpoint #'main-hook-fun
-                                         place
-                                         :kind :fun-end))
-            (setf break
-                  ;; FIXME: These and any other old (COERCE `(LAMBDA ..) ..)
-                  ;; forms should be converted to shiny new (LAMBDA ..) forms.
-                  ;; (Search the sources for "coerce.*\(lambda".)
-                  (coerce `(lambda (dummy)
-                             (declare (ignore dummy)) ,break)
-                          'function))
-            (setf condition (coerce `(lambda (dummy)
-                                       (declare (ignore dummy)) ,condition)
-                                    'function))
-            (dolist (form print)
-              (push (cons
-                     (coerce `(lambda (dummy)
-                                (declare (ignore dummy)) ,form) 'function)
-                     form)
-                    print-functions)))
-          (setup-code-location ()
-            (setf place (nth index *possible-breakpoints*))
-            (setf bp (sb!di:make-breakpoint #'main-hook-fun place
-                                            :kind :code-location))
-            (dolist (form print)
-              (push (cons
-                     (sb!di:preprocess-for-eval form place)
-                     form)
-                    print-functions))
-            (setf break (sb!di:preprocess-for-eval break place))
-            (setf condition (sb!di:preprocess-for-eval condition place))))
-      (set-vars-from-command-line (get-command-line))
-      (cond
-       ((or (eq index :start) (eq index :s))
-       (setup-fun-start))
-       ((or (eq index :end) (eq index :e))
-       (setup-fun-end))
-       (t
-       (setup-code-location)))
-      (sb!di:activate-breakpoint bp)
-      (let* ((new-bp-info (create-breakpoint-info place bp index
-                                                 :break break
-                                                 :print print-functions
-                                                 :condition condition))
-            (old-bp-info (location-in-list new-bp-info *breakpoints*)))
-       (when old-bp-info
-         (sb!di:deactivate-breakpoint (breakpoint-info-breakpoint
-                                       old-bp-info))
-         (setf *breakpoints* (remove old-bp-info *breakpoints*))
-         (format t "previous breakpoint removed~%"))
-       (push new-bp-info *breakpoints*))
-      (print-breakpoint-info (first *breakpoints*))
-      (format t "~&added"))))
-
-(!def-debug-command-alias "BP" "BREAKPOINT")
-
-;;; List all breakpoints which are set.
-(!def-debug-command "LIST-BREAKPOINTS" ()
-  (setf *breakpoints*
-       (sort *breakpoints* #'< :key #'breakpoint-info-breakpoint-number))
-  (dolist (info *breakpoints*)
-    (print-breakpoint-info info)))
-
-(!def-debug-command-alias "LB" "LIST-BREAKPOINTS")
-(!def-debug-command-alias "LBP" "LIST-BREAKPOINTS")
-
-;;; Remove breakpoint N, or remove all breakpoints if no N given.
-(!def-debug-command "DELETE-BREAKPOINT" ()
-  (let* ((index (read-if-available nil))
-        (bp-info
-         (find index *breakpoints* :key #'breakpoint-info-breakpoint-number)))
-    (cond (bp-info
-          (sb!di:delete-breakpoint (breakpoint-info-breakpoint bp-info))
-          (setf *breakpoints* (remove bp-info *breakpoints*))
-          (format t "breakpoint ~S removed~%" index))
-         (index (format t "The breakpoint doesn't exist."))
-         (t
-          (dolist (ele *breakpoints*)
-            (sb!di:delete-breakpoint (breakpoint-info-breakpoint ele)))
-          (setf *breakpoints* nil)
-          (format t "all breakpoints deleted~%")))))
-
-(!def-debug-command-alias "DBP" "DELETE-BREAKPOINT")
+;;; Stuff to clean up before saving a core
+(defun debug-deinit ()
+  ;; Nothing to do right now. Once there was, maybe once there
+  ;; will be again.
+  )
+
+(defun code-location-source-form (location context &optional (errorp t))
+  (let* ((start-location (maybe-block-start-location location))
+         (form-num (sb!di:code-location-form-number start-location)))
+    (multiple-value-bind (translations form)
+        (sb!di:get-toplevel-form start-location)
+      (cond ((< form-num (length translations))
+             (sb!di:source-path-context form
+                                        (svref translations form-num)
+                                        context))
+            (t
+             (funcall (if errorp #'error #'warn)
+                      "~@<Bogus form-number: the source file has ~
+                          probably changed too much to cope with.~:@>"))))))

 \f
 \f

+
+;;; start single-stepping
+(!def-debug-command "START" ()
+  (if (typep *debug-condition* 'step-condition)
+      (format *debug-io* "~&Already single-stepping.~%")
+      (let ((restart (find-restart 'continue *debug-condition*)))
+        (cond (restart
+               (sb!impl::enable-stepping)
+               (invoke-restart restart))
+              (t
+               (format *debug-io* "~&Non-continuable error, cannot start stepping.~%"))))))
+
+(defmacro def-step-command (command-name restart-name)
+  `(!def-debug-command ,command-name ()
+     (if (typep *debug-condition* 'step-condition)
+         (let ((restart (find-restart ',restart-name *debug-condition*)))
+           (aver restart)
+           (invoke-restart restart))
+         (format *debug-io* "~&Not currently single-stepping. (Use START to activate the single-stepper)~%"))))
+
+(def-step-command "STEP" step-into)
+(def-step-command "NEXT" step-next)
+(def-step-command "STOP" step-continue)
+
+(!def-debug-command-alias "S" "STEP")
+(!def-debug-command-alias "N" "NEXT")
+
+(!def-debug-command "OUT" ()
+  (if (typep *debug-condition* 'step-condition)
+      (if sb!impl::*step-out*
+          (let ((restart (find-restart 'step-out *debug-condition*)))
+            (aver restart)
+            (invoke-restart restart))
+          (format *debug-io* "~&OUT can only be used step out of frames that were originally stepped into with STEP.~%"))
+      (format *debug-io* "~&Not currently single-stepping. (Use START to activate the single-stepper)~%")))
+

 ;;; miscellaneous commands
 
 (!def-debug-command "DESCRIBE" ()
   (let* ((curloc (sb!di:frame-code-location *current-frame*))
 ;;; miscellaneous commands
 
 (!def-debug-command "DESCRIBE" ()
   (let* ((curloc (sb!di:frame-code-location *current-frame*))

-        (debug-fun (sb!di:code-location-debug-fun curloc))
-        (function (sb!di:debug-fun-fun debug-fun)))
+         (debug-fun (sb!di:code-location-debug-fun curloc))
+         (function (sb!di:debug-fun-fun debug-fun)))

     (if function
     (if function

-       (describe function)
-       (format t "can't figure out the function for this frame"))))
+        (describe function)
+        (format *debug-io* "can't figure out the function for this frame"))))

 
 (!def-debug-command "SLURP" ()
   (loop while (read-char-no-hang *standard-input*)))
 
 
 (!def-debug-command "SLURP" ()
   (loop while (read-char-no-hang *standard-input*)))
 

+;;; RETURN-FROM-FRAME and RESTART-FRAME
+
+(defun unwind-to-frame-and-call (frame thunk)
+  #!+unwind-to-frame-and-call-vop
+  (flet ((sap-int/fixnum (sap)
+           ;; On unithreaded X86 *BINDING-STACK-POINTER* and
+           ;; *CURRENT-CATCH-BLOCK* are negative, so we need to jump through
+           ;; some hoops to make these calculated values negative too.
+           (ash (truly-the (signed-byte #.sb!vm:n-word-bits)
+                           (sap-int sap))
+                (- sb!vm::n-fixnum-tag-bits))))
+    ;; To properly unwind the stack, we need three pieces of information:
+    ;;   * The unwind block that should be active after the unwind
+    ;;   * The catch block that should be active after the unwind
+    ;;   * The values that the binding stack pointer should have after the
+    ;;     unwind.
+    (let* ((block (sap-int/fixnum (find-enclosing-catch-block frame)))
+           (unbind-to (sap-int/fixnum (find-binding-stack-pointer frame))))
+      ;; This VOP will run the neccessary cleanup forms, reset the fp, and
+      ;; then call the supplied function.
+      (sb!vm::%primitive sb!vm::unwind-to-frame-and-call
+                         (sb!di::frame-pointer frame)
+                         (find-enclosing-uwp frame)
+                         (lambda ()
+                           ;; Before calling the user-specified
+                           ;; function, we need to restore the binding
+                           ;; stack and the catch block. The unwind block
+                           ;; is taken care of by the VOP.
+                           (sb!vm::%primitive sb!vm::unbind-to-here
+                                              unbind-to)
+                           (setf sb!vm::*current-catch-block* block)
+                           (funcall thunk)))))
+  #!-unwind-to-frame-and-call-vop
+  (let ((tag (gensym)))
+    (sb!di:replace-frame-catch-tag frame
+                                   'sb!c:debug-catch-tag
+                                   tag)
+    (throw tag thunk)))
+
+(defun find-binding-stack-pointer (frame)
+  #!-stack-grows-downward-not-upward
+  (declare (ignore frame))
+  #!-stack-grows-downward-not-upward
+  (error "Not implemented on this architecture")
+  #!+stack-grows-downward-not-upward
+  (let ((bsp (sb!vm::binding-stack-pointer-sap))
+        (unbind-to nil)
+        (fp (sb!di::frame-pointer frame))
+        (start (int-sap (ldb (byte #.sb!vm:n-word-bits 0)
+                             (ash sb!vm:*binding-stack-start*
+                                  sb!vm:n-fixnum-tag-bits)))))
+    ;; Walk the binding stack looking for an entry where the symbol is
+    ;; an unbound-symbol marker and the value is equal to the frame
+    ;; pointer.  These entries are inserted into the stack by the
+    ;; BIND-SENTINEL VOP and removed by UNBIND-SENTINEL (inserted into
+    ;; the function during IR2). If an entry wasn't found, the
+    ;; function that the frame corresponds to wasn't compiled with a
+    ;; high enough debug setting, and can't be restarted / returned
+    ;; from.
+    (loop until (sap= bsp start)
+          do (progn
+               (setf bsp (sap+ bsp
+                               (- (* sb!vm:binding-size sb!vm:n-word-bytes))))
+               (let ((symbol (sap-ref-word bsp (* sb!vm:binding-symbol-slot
+                                                  sb!vm:n-word-bytes)))
+                     (value (sap-ref-sap bsp (* sb!vm:binding-value-slot
+                                                sb!vm:n-word-bytes))))
+                 (when (eql symbol sb!vm:unbound-marker-widetag)
+                   (when (sap= value fp)
+                     (setf unbind-to bsp))))))
+    unbind-to))
+
+(defun find-enclosing-catch-block (frame)
+  ;; Walk the catch block chain looking for the first entry with an address
+  ;; higher than the pointer for FRAME or a null pointer.
+  (let* ((frame-pointer (sb!di::frame-pointer frame))
+         (current-block (int-sap (ldb (byte #.sb!vm:n-word-bits 0)
+                                      (ash sb!vm::*current-catch-block*
+                                           sb!vm:n-fixnum-tag-bits))))
+         (enclosing-block (loop for block = current-block
+                                then (sap-ref-sap block
+                                                  (* sb!vm:catch-block-previous-catch-slot
+                                                     sb!vm::n-word-bytes))
+                                when (or (zerop (sap-int block))
+                                         (sap> block frame-pointer))
+                                return block)))
+    enclosing-block))
+
+(defun find-enclosing-uwp (frame)
+  ;; Walk the UWP chain looking for the first entry with an address
+  ;; higher than the pointer for FRAME or a null pointer.
+  (let* ((frame-pointer (sb!di::frame-pointer frame))
+         (current-uwp (int-sap (ldb (byte #.sb!vm:n-word-bits 0)
+                                    (ash sb!vm::*current-unwind-protect-block*
+                                         sb!vm:n-fixnum-tag-bits))))
+         (enclosing-uwp (loop for uwp-block = current-uwp
+                              then (sap-ref-sap uwp-block
+                                                sb!vm:unwind-block-current-uwp-slot)
+                              when (or (zerop (sap-int uwp-block))
+                                       (sap> uwp-block frame-pointer))
+                              return uwp-block)))
+    enclosing-uwp))
+

 (!def-debug-command "RETURN" (&optional
 (!def-debug-command "RETURN" (&optional

-                             (return (read-prompting-maybe
-                                      "return: ")))
-  (let ((tag (find-if (lambda (x)
-                       (and (typep (car x) 'symbol)
-                            (not (symbol-package (car x)))
-                            (string= (car x) "SB-DEBUG-CATCH-TAG")))
-                     (sb!di::frame-catches *current-frame*))))
-    (if tag
-       (throw (car tag)
-         (funcall (sb!di:preprocess-for-eval
-                   return
-                   (sb!di:frame-code-location *current-frame*))
-                  *current-frame*))
-       (format t "~@<can't find a tag for this frame ~
-                   ~2I~_(hint: try increasing the DEBUG optimization quality ~
-                   and recompiling)~:@>"))))
+                              (return (read-prompting-maybe
+                                       "return: ")))
+   (if (frame-has-debug-tag-p *current-frame*)
+       (let* ((code-location (sb!di:frame-code-location *current-frame*))
+              (values (multiple-value-list
+                       (funcall (sb!di:preprocess-for-eval return code-location)
+                                *current-frame*))))
+         (unwind-to-frame-and-call *current-frame* (lambda ()
+                                                     (values-list values))))
+       (format *debug-io*
+               "~@<can't find a tag for this frame ~
+                 ~2I~_(hint: try increasing the DEBUG optimization quality ~
+                 and recompiling)~:@>")))
+
+(!def-debug-command "RESTART-FRAME" ()
+  (if (frame-has-debug-tag-p *current-frame*)
+      (multiple-value-bind (fname args) (frame-call *current-frame*)
+        (multiple-value-bind (fun arglist ok)
+            (if (and (legal-fun-name-p fname) (fboundp fname))
+                (values (fdefinition fname) args t)
+                (values (sb!di:debug-fun-fun (sb!di:frame-debug-fun *current-frame*))
+                        (frame-args-as-list *current-frame*)
+                        nil))
+          (when (and fun
+                     (or ok
+                         (y-or-n-p "~@<No global function for the frame, but we ~
+                                    do have access to a function object that we ~
+                                    can try to call -- but if it is normally part ~
+                                    of a closure, then this is NOT going to end well.~_~_~
+                                    Try it anyways?~:@>")))
+            (unwind-to-frame-and-call *current-frame*
+                                      (lambda ()
+                                        ;; Ensure TCO.
+                                        (declare (optimize (debug 0)))
+                                        (apply fun arglist))))
+          (format *debug-io*
+              "Can't restart ~S: no function for frame."
+              *current-frame*)))
+      (format *debug-io*
+              "~@<Can't restart ~S: tag not found. ~
+               ~2I~_(hint: try increasing the DEBUG optimization quality ~
+               and recompiling)~:@>"
+              *current-frame*)))
+
+(defun frame-has-debug-tag-p (frame)
+  #!+unwind-to-frame-and-call-vop
+  (not (null (find-binding-stack-pointer frame)))
+  #!-unwind-to-frame-and-call-vop
+  (find 'sb!c:debug-catch-tag (sb!di::frame-catches frame) :key #'car))
+
+(defun frame-has-debug-vars-p (frame)
+  (sb!di:debug-var-info-available
+   (sb!di:code-location-debug-fun
+    (sb!di:frame-code-location frame))))
+
+;; Hack: ensure that *U-T-F-F* has a tls index.
+#!+unwind-to-frame-and-call-vop
+(let ((sb!vm::*unwind-to-frame-function* (lambda ()))))
+

 \f
 ;;;; debug loop command utilities
 
 (defun read-prompting-maybe (prompt)
   (unless (sb!int:listen-skip-whitespace *debug-io*)
 \f
 ;;;; debug loop command utilities
 
 (defun read-prompting-maybe (prompt)
   (unless (sb!int:listen-skip-whitespace *debug-io*)

-    (princ prompt)
-    (force-output))
+    (princ prompt *debug-io*)
+    (force-output *debug-io*))

   (read *debug-io*))
 
 (defun read-if-available (default)
   (read *debug-io*))
 
 (defun read-if-available (default)