remove misplaced AVER

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

diff --git a/src/code/debug.lisp b/src/code/debug.lisp
index db912d1..d7b9a62 100644 (file)
--- a/src/code/debug.lisp
+++ b/src/code/debug.lisp
@@ -62,12 +62,13 @@ provide bindings for printer control variables.")
 ;;; 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)
 

@@ -120,9 +121,14 @@ Inspecting frames:
   SOURCE [n]     displays frame's source form with n levels of enclosing forms.
 
 Stepping:
   SOURCE [n]     displays frame's source form with n levels of enclosing forms.
 
 Stepping:

-  STEP  Selects the CONTINUE restart if one exists and starts
+  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.
         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)

@@ -136,11 +142,21 @@ Other commands:
     current frame, if this frame was compiled with a sufficiently high
     DEBUG optimization quality.
 
     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

+(defmacro with-debug-io-syntax (() &body body)
+  (let ((thunk (gensym "THUNK")))
+    `(dx-flet ((,thunk ()
+                       ,@body))
+       (funcall-with-debug-io-syntax #',thunk))))

 
 ;;; 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

@@ -160,33 +176,261 @@ Other commands:
 \f
 ;;;; BACKTRACE
 
 \f
 ;;;; BACKTRACE
 

-(defun backtrace (&optional (count most-positive-fixnum) (stream *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
   #!+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 stream)
-  (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 stream :number t))
-  (fresh-line stream)
-  (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)
-  (multiple-value-bind (name args) (frame-call frame)
-    (cons name args)))
+  "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 occurred, 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
+  "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."
+  (with-debug-io-syntax ()
+    (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)))
+
+(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
 

@@ -200,6 +444,7 @@ is how many frames to show."
                                               optional
                                               rest
                                               keyword
                                               optional
                                               rest
                                               keyword

+                                              more

                                               deleted)
   `(etypecase ,element
      (sb!di:debug-var
                                               deleted)
   `(etypecase ,element
      (sb!di:debug-var

@@ -208,7 +453,8 @@ is how many frames to show."
       (ecase (car ,element)
         (:optional ,@optional)
         (:rest ,@rest)
       (ecase (car ,element)
         (:optional ,@optional)
         (:rest ,@rest)

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

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

@@ -223,65 +469,87 @@ is how many frames to show."
 
 ) ; 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 map-frame-args (thunk frame)
+  (let ((debug-fun (sb!di:frame-debug-fun frame)))
+    (dolist (element (sb!di:debug-fun-lambda-list debug-fun))
+      (funcall thunk element))))
+

 (defun frame-args-as-list (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")))))
-(legal-fun-name-p '(lambda ()))
-(defvar *show-entry-point-details* nil)
-
-(defun clean-xep (name args)
+  (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 interrupted-frame-error (frame)
+  (when (and (sb!di::compiled-frame-p frame)
+             (sb!di::compiled-frame-escaped frame))
+    (let ((error-number (sb!vm:internal-error-args
+                         (sb!di::compiled-frame-escaped frame))))
+      (when (array-in-bounds-p sb!c:*backend-internal-errors* error-number)
+        (car (svref sb!c:*backend-internal-errors* error-number))))))
+
+(defun clean-xep (frame name args info)

   (values (second name)
           (if (consp args)
   (values (second name)
           (if (consp args)

-              (let ((count (first args))
-                    (real-args (rest args)))
-                (if (fixnump count)
-                    (subseq real-args 0
-                            (min count (length real-args)))
+              (let* ((count (first args))
+                     (real-args (rest args)))
+                (if (and (integerp count)
+                         (eq (interrupted-frame-error frame)
+                             'invalid-arg-count-error))
+                    ;; 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))
                     real-args))

-              args)))
+              args)
+          (if (eq (car name) 'sb!c::tl-xep)
+              (cons :tl info)
+              info)))

 
 

-(defun clean-&more-processor (name args)
+(defun clean-&more-processor (name args info)

   (values (second name)
           (if (consp args)
               (let* ((more (last args 2))
   (values (second name)
           (if (consp args)
               (let* ((more (last args 2))

@@ -294,33 +562,72 @@ is how many frames to show."
                       (sb!c:%more-arg-values context 0 count))
                      (list
                       (make-unprintable-object "more unavailable arguments")))))
                       (sb!c:%more-arg-values context 0 count))
                      (list
                       (make-unprintable-object "more unavailable arguments")))))

-              args)))
-
-(defun frame-call (frame)
-  (labels ((clean-name-and-args (name args)
-             (if (and (consp name) (not *show-entry-point-details*))
-                 ;; FIXME: do we need to deal with
-                 ;; HAIRY-FUNCTION-ENTRY here? I can't make it or
-                 ;; &AUX-BINDINGS appear in backtraces, so they are
-                 ;; left alone for now. --NS 2005-02-28
-                 (case (first name)
-                   ((sb!c::xep sb!c::tl-xep)
-                    (clean-xep name args))
-                   ((sb!c::&more-processor)
-                    (clean-&more-processor name args))
-                   ((sb!c::hairy-arg-processor
-                     sb!c::varargs-entry sb!c::&optional-processor)
-                    (clean-name-and-args (second name) args))
-                   (t
-                    (values name args)))
-                 (values name args))))
-    (let ((debug-fun (sb!di:frame-debug-fun frame)))
-      (multiple-value-bind (name args)
-          (clean-name-and-args (sb!di:debug-fun-name debug-fun)
-                                (frame-args-as-list frame))
-        (values name args
-                (when *show-entry-point-details*
-                  (sb!di:debug-fun-kind debug-fun)))))))
+              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 (frame name method-frame-style info)
+  (let ((args (frame-args-as-list frame)))
+    (if (consp name)
+        (case (first name)
+          ((sb!c::xep sb!c::tl-xep)
+           (clean-xep frame name args info))
+          ((sb!c::&more-processor)
+           (clean-&more-processor name args info))
+          ((sb!c::&optional-processor)
+           (clean-frame-call frame (second name) 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 frame
+                          (sb!di:debug-fun-name debug-fun)
+                          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
 
 (defun ensure-printable-object (object)
   (handler-case

@@ -342,43 +649,50 @@ is how many frames to show."
 ;;; 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 stream &key (verbosity 1) (number nil))
+(defun print-frame-call (frame stream
+                         &key print-frame-source
+                              number
+                              (method-frame-style *method-frame-style*))

   (when number
   (when number

-    (format stream "~&~S: " (sb!di:frame-number frame)))
-  (if (zerop verbosity)
-      (let ((*print-readably* nil))
-        (prin1 frame stream))
-      (multiple-value-bind (name args kind) (frame-call frame)
-        (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))
-            (prin1 (ensure-printable-object name) stream))
-          ;; 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 kind
-          (format stream "[~S]" kind))))
-  (when (>= verbosity 2)
+    (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
-            ;; FIXME: Is this call really necessary here? If it is,
-            ;; then the reason for it should be unobscured.
-            (sb!di:code-location-debug-block loc)
-            (format stream "~%source: ")
-            (prin1 (code-location-source-form loc 0) stream))
-        (sb!di:debug-condition (ignore)
-          ignore)
+          (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)
         (error (c)

-          (format stream "~&error finding source: ~A" c))))))
+          (format stream "~&   error printing frame source: ~A" c))))))

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

@@ -471,44 +785,84 @@ is how many frames to show."
                 (nreverse (mapcar #'cdr *debug-print-variable-alist*))
               (apply fun rest)))))))
 
                 (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."
 

-  ;; call *INVOKE-DEBUGGER-HOOK* first, so that *DEBUGGER-HOOK* is not
-  ;; called when the debugger is disabled
-  (let ((old-hook *invoke-debugger-hook*))
-    (when old-hook
-      (let ((*invoke-debugger-hook* nil))
-        (funcall old-hook condition old-hook))))
-  (let ((old-hook *debugger-hook*))
-    (when old-hook
-      (let ((*debugger-hook* nil))
-        (funcall old-hook condition old-hook))))
-
-  ;; 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))
+  (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)
 
 (defun %invoke-debugger (condition)

-

   (let ((*debug-condition* condition)
         (*debug-restarts* (compute-restarts condition))
         (*nested-debug-condition* nil))
   (let ((*debug-condition* condition)
         (*debug-restarts* (compute-restarts condition))
         (*nested-debug-condition* nil))

@@ -518,13 +872,8 @@ reset to ~S."
         ;; when people redirect *ERROR-OUTPUT*, they could reasonably
         ;; expect to see error messages logged there, regardless of what
         ;; the debugger does afterwards.)
         ;; when people redirect *ERROR-OUTPUT*, they could reasonably
         ;; expect to see error messages logged there, regardless of what
         ;; the debugger does afterwards.)

-        (format *error-output*
-                "~2&~@<debugger invoked on a ~S~@[ in thread ~A~]: ~
-                    ~2I~_~A~:@>~%"
-                (type-of *debug-condition*)
-                #!+sb-thread sb!thread:*current-thread*
-                #!-sb-thread nil
-                *debug-condition*)
+        (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*)))
       (error (condition)
         (setf *nested-debug-condition* condition)
         (let ((ndc-type (type-of *nested-debug-condition*)))

@@ -571,7 +920,7 @@ reset to ~S."
                (when *debug-beginner-help-p*
                  (format *debug-io*
                          "~%~@<Type HELP for debugger help, or ~
                (when *debug-beginner-help-p*
                  (format *debug-io*
                          "~%~@<Type HELP for debugger help, or ~

-                               (SB-EXT:QUIT) to exit from SBCL.~:@>~2%"))
+                               (SB-EXT:EXIT) to exit from SBCL.~:@>~2%"))

                (show-restarts *debug-restarts* *debug-io*))
              (internal-debug))
         (when background-p
                (show-restarts *debug-restarts* *debug-io*))
              (internal-debug))
         (when background-p

@@ -580,82 +929,122 @@ reset to ~S."
 ;;; this function is for use in *INVOKE-DEBUGGER-HOOK* when ordinary
 ;;; ANSI behavior has been suppressed by the "--disable-debugger"
 ;;; command-line option
 ;;; 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))
+(defun debugger-disabled-hook (condition previous-hook)
+  (declare (ignore previous-hook))

   ;; There is no one there to interact with, so report the
   ;; condition and terminate the program.
   ;; There is no one there to interact with, so report the
   ;; condition and terminate the program.

-  (flet ((failure-quit (&key recklessly-p)
+  (let ((*suppress-print-errors* t)
+        (condition-error-message
+         #.(format nil "A nested error within --disable-debugger error ~
+            handling prevents displaying the original error. Attempting ~
+            to print a backtrace."))
+        (backtrace-error-message
+         #.(format nil "A nested error within --disable-debugger error ~
+            handling prevents printing the backtrace. Sorry, exiting.")))
+    (labels
+        ((failure-quit (&key abort)

            (/show0 "in FAILURE-QUIT (in --disable-debugger debugger hook)")
            (/show0 "in FAILURE-QUIT (in --disable-debugger debugger hook)")

-           (quit :unix-status 1 :recklessly-p recklessly-p)))
-    ;; 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.)
-          (sb!debug:backtrace 128 *error-output*)
-          (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 :recklessly-p t)))))
+           (exit :code 1 :abort abort))
+         (display-condition ()
+           (handler-case
+               (handler-case
+                   (print-condition)
+                 (condition ()
+                   ;; printing failed, try to describe it
+                   (describe-condition)))
+             (condition ()
+               ;; ok, give up trying to display the error and inform the user about it
+               (finish-output *error-output*)
+               (%primitive print condition-error-message))))
+         (print-condition ()
+           (format *error-output*
+                   "~&~@<Unhandled ~S~@[ in thread ~S~]: ~2I~_~A~:>~2%"
+                   (type-of condition)
+                   #!+sb-thread sb!thread:*current-thread*
+                   #!-sb-thread nil
+                   condition)
+           (finish-output *error-output*))
+         (describe-condition ()
+           (format *error-output*
+                   "~&Unhandled ~S~@[ in thread ~S~]:~%"
+                   (type-of condition)
+                   #!+sb-thread sb!thread:*current-thread*
+                   #!-sb-thread nil)
+           (describe condition *error-output*)
+           (finish-output *error-output*))
+         (display-backtrace ()
+           (handler-case
+               (print-backtrace :stream *error-output*
+                                :from :interrupted-frame
+                                :print-thread t)
+             (condition ()
+               (values)))
+           (finish-output *error-output*)))
+      ;; 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. Separate the error handling of the
+      ;; two phases to maximize the chance of emitting some useful
+      ;; information.
+      (handler-case
+          (progn
+            (display-condition)
+            (display-backtrace)
+            (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 backtrace-error-message))
+          (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 ()
 
 ;;; halt-on-failures and prompt-on-failures modes, suitable for
 ;;; noninteractive and interactive use respectively
 (defun disable-debugger ()

-  ;; Why conditionally? Why not disable it even if user has frobbed
-  ;; this hook? We could just save the old value in case of a later
-  ;; ENABLE-DEBUGGER.
-  (when (eql *invoke-debugger-hook* nil)
-    ;; *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
-    (setf *invoke-debugger-hook* 'debugger-disabled-hook)
-    (sb!alien:alien-funcall (sb!alien:extern-alien "disable_lossage_handler" (function sb!alien:void)))))
+  "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 ()
 
 (defun enable-debugger ()

+  "Restore the debugger if it has been turned off by DISABLE-DEBUGGER."

   (when (eql *invoke-debugger-hook* 'debugger-disabled-hook)
   (when (eql *invoke-debugger-hook* 'debugger-disabled-hook)

-    (setf *invoke-debugger-hook* nil)
-    (sb!alien:alien-funcall (sb!alien:extern-alien "enable_lossage_handler" (function sb!alien:void)))))
+    (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)

@@ -693,6 +1082,11 @@ reset to ~S."
 (defvar *debug-loop-fun* #'debug-loop-fun
   "a function taking no parameters that starts the low-level debug loop")
 
 (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
 ;;; the debugger. SB!KERNEL::ERROR-ERROR calls this in emergencies
 ;;; This calls DEBUG-LOOP, performing some simple initializations
 ;;; before doing so. INVOKE-DEBUGGER calls this to actually get into
 ;;; the debugger. SB!KERNEL::ERROR-ERROR calls this in emergencies

@@ -704,7 +1098,8 @@ reset to ~S."
         (*read-suppress* nil))
     (unless (typep *debug-condition* 'step-condition)
       (clear-input *debug-io*))
         (*read-suppress* nil))
     (unless (typep *debug-condition* 'step-condition)
       (clear-input *debug-io*))

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

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

@@ -715,12 +1110,12 @@ 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-read (stream)
+(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)
   (declare (type stream stream))
   (let* ((eof-marker (cons nil nil))
          (form (read stream nil eof-marker)))
     (if (eq form eof-marker)

-        (abort)
+        (invoke-restart eof-restart)

         form)))
 
 (defun debug-loop-fun ()
         form)))
 
 (defun debug-loop-fun ()

@@ -734,8 +1129,11 @@ reset to ~S."
                       (princ condition *debug-io*)
                       (/show0 "handling d-c by THROWing DEBUG-LOOP-CATCHER")
                       (throw 'debug-loop-catcher nil))))
                       (princ condition *debug-io*)
                       (/show0 "handling d-c by THROWing DEBUG-LOOP-CATCHER")
                       (throw 'debug-loop-catcher nil))))

-      (terpri *debug-io*)
-      (print-frame-call *current-frame* *debug-io* :verbosity 2)
+      (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
        (catch 'debug-loop-catcher
          (handler-bind ((error (lambda (condition)
       (loop
        (catch 'debug-loop-catcher
          (handler-bind ((error (lambda (condition)

@@ -748,18 +1146,21 @@ reset to ~S."
                                            '*flush-debug-errors*)
                                    (/show0 "throwing DEBUG-LOOP-CATCHER")
                                    (throw 'debug-loop-catcher nil)))))
                                            '*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.
+           ;; 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*)
            (let ((level *debug-command-level*)

-                 (restart-commands (make-restart-commands)))
+                 (restart-commands (make-restart-commands))
+                 (abort-restart-for-eof (find-restart 'abort)))

              (flush-standard-output-streams)
              (debug-prompt *debug-io*)
              (force-output *debug-io*)
              (flush-standard-output-streams)
              (debug-prompt *debug-io*)
              (force-output *debug-io*)

-             (let* ((exp (debug-read *debug-io*))
-                    (cmd-fun (debug-command-p exp restart-commands)))
-               (with-simple-restart (abort
-                                     "~@<Reduce debugger level (to debug level ~W).~@:>"
-                                     level)
+             (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)
                  (cond ((not cmd-fun)
                         (debug-eval-print exp))
                        ((consp cmd-fun)

@@ -771,9 +1172,26 @@ reset to ~S."
                        (t
                         (funcall cmd-fun))))))))))))
 
                        (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)

-  (let ((values (multiple-value-list (interactive-eval expr))))
+  (let ((values (multiple-value-list
+                 (interactive-eval expr :eval #'debug-eval))))

     (/noshow "done with EVAL in DEBUG-EVAL-PRINT")
     (dolist (value values)
       (fresh-line *debug-io*)
     (/noshow "done with EVAL in DEBUG-EVAL-PRINT")
     (dolist (value values)
       (fresh-line *debug-io*)

@@ -1141,7 +1559,7 @@ 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" ()
   (print-frame-call *current-frame* *debug-io*))
 
 (!def-debug-command "PRINT" ()
   (print-frame-call *current-frame* *debug-io*))

@@ -1155,19 +1573,29 @@ reset to ~S."
               (location (sb!di:frame-code-location *current-frame*))
               (prefix (read-if-available nil))
               (any-p nil)
               (location (sb!di:frame-code-location *current-frame*))
               (prefix (read-if-available nil))
               (any-p nil)

-              (any-valid-p nil))
+              (any-valid-p nil)
+              (more-context nil)
+              (more-count nil))

           (dolist (v (sb!di:ambiguous-debug-vars
           (dolist (v (sb!di:ambiguous-debug-vars

-                        d-fun
-                        (if prefix (string prefix) "")))
+                      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)
             (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*))))
               (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*
           (cond
            ((not any-p)
             (format *debug-io*

@@ -1191,131 +1619,55 @@ reset to ~S."
 \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*))
-
-;;; Stuff to clean up before saving a core
-(defun debug-deinit ()
-  (setf *cached-debug-source* nil
-        *cached-source-stream* nil
-        *cached-readtable* nil))
-
-;;; 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 *debug-io* "~%; 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 *debug-io*
-              "~%; 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 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."))
-      (sb!di:source-path-context form
-                                 (svref translations form-num)
-                                 context))))
+(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

-;;; step to the next steppable form
-(!def-debug-command "STEP" ()
-  (let ((restart (find-restart 'continue *debug-condition*)))
-    (cond (restart
-           (setf *stepping* t
-                 *step* t)
+
+;;; 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))
            (invoke-restart restart))

-          (t
-           (format *debug-io* "~&Non-continuable error, cannot step.~%")))))
+         (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
 
 
 ;;; miscellaneous commands
 

@@ -1330,24 +1682,164 @@ reset to ~S."
 (!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
                               (return (read-prompting-maybe
                                        "return: ")))
 (!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 *debug-io*
-                "~@<can't find a tag for this frame ~
+   (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 ~
                  ~2I~_(hint: try increasing the DEBUG optimization quality ~

-                 and recompiling)~:@>"))))
+                 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))))

 \f
 ;;;; debug loop command utilities
 
 \f
 ;;;; debug loop command utilities