src/code/step.lisp

   1 ;;;; single stepper for SBCL
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 ;;;; Single stepping works by having compiler insert STEP-CONDITION
  13 ;;;; signalling forms into code compiled at high debug settings, and
  14 ;;;; having a handler for them at the toplevel.
  15
  16 (in-package "SB-IMPL") ; in warm SBCL
  17
  18 (defun step-form (form args)
  19   (restart-case
  20       (signal 'step-form-condition
  21               :form form
  22               :args args)
  23     (step-continue ()
  24       :report "Resume normal execution"
  25       (disable-stepping)
  26       (setf *step-out* nil))
  27     (step-out ()
  28       :report "Resume stepping after returning from this function"
  29       (ecase *step-out*
  30         ((nil)
  31          (error "Can't STEP-OUT: No STEP-IN on the call-stack"))
  32         ((t :maybe)
  33          (disable-stepping)
  34          (setf *step-out* t)))
  35       nil)
  36     (step-next ()
  37       :report "Step over call"
  38       nil)
  39     (step-into ()
  40       :report "Step into call"
  41       t)))
  42
  43 (defun step-values (form &rest values)
  44   (declare (dynamic-extent values))
  45   (signal 'step-values-condition :form form :result values)
  46   (values-list values))
  47
  48 (defun step-finished ()
  49   (restart-case
  50       (signal 'step-finished-condition)
  51     (continue ())))
  52
  53 (defgeneric single-step (condition))
  54
  55 (defmethod single-step ((condition step-values-condition))
  56   (let ((values (step-condition-result condition)))
  57     (format *debug-io* "; ~A => ~:[#<no value>~;~{~S~^, ~}~]~%"
  58             (step-condition-form condition)
  59             values values)))
  60
  61 (defmethod single-step ((condition step-form-condition))
  62   (let ((form (step-condition-form condition))
  63         (args (step-condition-args condition)))
  64     (let ((*print-circle* t)
  65           (*print-pretty* t)
  66           (*print-readably* nil))
  67       (format *debug-io*
  68               "; Evaluating call:~%~<; ~@;  ~A~:>~%~
  69                ; ~:[With arguments:~%~<; ~@;~{  ~S~^~%~}~:>~;With unknown arguments~]~%"
  70               (list form)
  71               (eq args :unknown)
  72               (list args)))
  73     (finish-output *debug-io*)
  74     (let ((*stack-top-hint* (sb-di::find-stepped-frame)))
  75       (invoke-debugger condition))))
  76
  77 ;;; In the TTY debugger we're not interested in STEP returning
  78 (defmethod single-step ((condition step-finished-condition))
  79   (values))
  80
  81 (defvar *stepper-hook* 'single-step
  82   #+sb-doc "Customization hook for alternative single-steppers.
  83 *STEPPER-HOOK* is bound to NIL prior to calling the bound function
  84 with the STEP-CONDITION as argument.")
  85
  86 (defun invoke-stepper (condition)
  87   (when (and (stepping-enabled-p)
  88              *stepper-hook*)
  89     (with-stepping-disabled
  90       (let ((hook *stepper-hook*)
  91             (*stepper-hook* nil))
  92         (funcall hook condition)))))
  93
  94 (defmacro step (form)
  95   #+sb-doc
  96   "The form is evaluated with single stepping enabled. Function calls
  97 outside the lexical scope of the form can be stepped into only if the
  98 functions in question have been compiled with sufficient DEBUG policy
  99 to be at least partially steppable."
 100   `(locally
 101     (declare (optimize debug (sb-c:insert-step-conditions 0)))
 102      ;; Allow stepping out of the STEP form.
 103      (let ((*step-out* :maybe))
 104        (unwind-protect
 105             (with-stepping-enabled
 106               (multiple-value-prog1
 107                   (locally (declare (optimize (sb-c:insert-step-conditions 3)))
 108                     ,form)
 109                 (step-finished)))))))
 110