src/pcl/slots.lisp

   1 ;;;; This software is part of the SBCL system. See the README file for
   2 ;;;; more information.
   3
   4 ;;;; This software is derived from software originally released by Xerox
   5 ;;;; Corporation. Copyright and release statements follow. Later modifications
   6 ;;;; to the software are in the public domain and are provided with
   7 ;;;; absolutely no warranty. See the COPYING and CREDITS files for more
   8 ;;;; information.
   9
  10 ;;;; copyright information from original PCL sources:
  11 ;;;;
  12 ;;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
  13 ;;;; All rights reserved.
  14 ;;;;
  15 ;;;; Use and copying of this software and preparation of derivative works based
  16 ;;;; upon this software are permitted. Any distribution of this software or
  17 ;;;; derivative works must comply with all applicable United States export
  18 ;;;; control laws.
  19 ;;;;
  20 ;;;; This software is made available AS IS, and Xerox Corporation makes no
  21 ;;;; warranty about the software, its performance or its conformity to any
  22 ;;;; specification.
  23
  24 (in-package "SB-PCL")
  25 \f
  26 ;;;; ANSI CL condition for unbound slots
  27
  28 (define-condition unbound-slot (cell-error)
  29   ((instance :reader unbound-slot-instance :initarg :instance))
  30   (:report (lambda (condition stream)
  31              (handler-case
  32                  (format stream "~@<The slot ~/sb-ext:print-symbol-with-prefix/ ~
  33                          is unbound in the object ~A.~@:>"
  34                          (cell-error-name condition)
  35                          (unbound-slot-instance condition))
  36                (serious-condition ()
  37                  ;; In case of an error try again avoiding custom PRINT-OBJECT's.
  38                  (format stream "~&Error during printing.~%~@<The slot ~
  39                          ~/sb-ext:print-symbol-with-prefix/ ~
  40                          is unbound in an instance of ~
  41                          ~/sb-ext:print-symbol-with-prefix/.~@:>"
  42                          (cell-error-name condition)
  43                          (type-of (unbound-slot-instance condition))))))))
  44
  45 (defmethod wrapper-fetcher ((class standard-class))
  46   '%instance-layout)
  47
  48 (defmethod slots-fetcher ((class standard-class))
  49   'std-instance-slots)
  50
  51 (defmethod raw-instance-allocator ((class standard-class))
  52   'allocate-standard-instance)
  53
  54 ;;; These three functions work on std-instances and fsc-instances. These are
  55 ;;; instances for which it is possible to change the wrapper and the slots.
  56 ;;;
  57 ;;; For these kinds of instances, most specified methods from the instance
  58 ;;; structure protocol are promoted to the implementation-specific class
  59 ;;; std-class. Many of these methods call these four functions.
  60
  61 (defun %swap-wrappers-and-slots (i1 i2) ; old -> new
  62   (cond ((std-instance-p i1)
  63          #+(and compact-instance-header x86-64)
  64          (let ((oslots (std-instance-slots i1))
  65                (nslots (std-instance-slots i2)))
  66            ;; The hash val is in the header of the slots. Copying is race-free
  67            ;; because it is immutable once memoized by STD-INSTANCE-HASH.
  68            (sb-vm::cas-header-data-high
  69             nslots 0 (sb-impl::%std-instance-hash oslots)))
  70          ;; FIXME: If a backend supports two-word primitive instances
  71          ;; and double-wide CAS, it's probably best to use that.
  72          ;; Maybe we're inside a mutex here anyway though?
  73          (let ((w1 (%instance-layout i1))
  74                (s1 (std-instance-slots i1)))
  75            (setf (%instance-layout i1) (%instance-layout i2))
  76            (setf (std-instance-slots i1) (std-instance-slots i2))
  77            (setf (%instance-layout i2) w1)
  78            (setf (std-instance-slots i2) s1)))
  79         ((fsc-instance-p i1)
  80          (let ((w1 (%funcallable-instance-layout i1))
  81                (w2 (%funcallable-instance-layout i2))
  82                (s1 (fsc-instance-slots i1)))
  83            (aver (= (layout-bitmap w1) (layout-bitmap w2)))
  84            (setf (%funcallable-instance-layout i1) w2)
  85            (setf (fsc-instance-slots i1) (fsc-instance-slots i2))
  86            (setf (%funcallable-instance-layout i2) w1)
  87            (setf (fsc-instance-slots i2) s1)))
  88         (t
  89          (error "unrecognized instance type"))))
  90 \f
  91 ;;;; STANDARD-INSTANCE-ACCESS
  92
  93 (declaim (inline standard-instance-access
  94                  (setf standard-instance-access)
  95                  (cas stadard-instance-access)
  96                  funcallable-standard-instance-access
  97                  (setf funcallable-standard-instance-access)
  98                  (cas funcallable-standard-instance-access)))
  99
 100 (defun standard-instance-access (instance location)
 101   (clos-slots-ref (std-instance-slots instance) location))
 102
 103 (defun (setf standard-instance-access) (new-value instance location)
 104   (setf (clos-slots-ref (std-instance-slots instance) location) new-value))
 105
 106 (defun (cas standard-instance-access) (old-value new-value instance location)
 107   ;; FIXME: Maybe get rid of CLOS-SLOTS-REF entirely?
 108   (cas (svref (std-instance-slots instance) location) old-value new-value))
 109
 110 (defun funcallable-standard-instance-access (instance location)
 111   (clos-slots-ref (fsc-instance-slots instance) location))
 112
 113 (defun (setf funcallable-standard-instance-access) (new-value instance location)
 114   (setf (clos-slots-ref (fsc-instance-slots instance) location) new-value))
 115
 116 (defun (cas funcallable-standard-instance-access) (old-value new-value instance location)
 117   ;; FIXME: Maybe get rid of CLOS-SLOTS-REF entirely?
 118   (cas (svref (fsc-instance-slots instance) location) old-value new-value))
 119 \f
 120 ;;;; SLOT-VALUE, (SETF SLOT-VALUE), SLOT-BOUNDP, SLOT-MAKUNBOUND
 121
 122 (declaim (ftype (sfunction (t symbol) t) slot-value))
 123 (defun slot-value (object slot-name)
 124   (let* ((wrapper (valid-wrapper-of object))
 125          (cell (find-slot-cell wrapper slot-name))
 126          (location (car cell))
 127          (value
 128           (cond ((fixnump location)
 129                  (if (std-instance-p object)
 130                      (standard-instance-access object location)
 131                      (funcallable-standard-instance-access object location)))
 132                 ((not location)
 133                  (return-from slot-value
 134                    (if cell
 135                        (funcall (slot-info-reader (cdr cell)) object)
 136                        (values (slot-missing (wrapper-class* wrapper) object
 137                                              slot-name 'slot-value)))))
 138                 ;; this next test means CONSP, but the transform that weakens
 139                 ;; CONSP to LISTP isn't working here for some reason.
 140                 ((listp location)
 141                  (cdr location))
 142                 (t
 143                  (bug "Bogus slot cell in SLOT-VALUE: ~S" cell)))))
 144     (if (unbound-marker-p value)
 145         (slot-unbound (wrapper-class* wrapper) object slot-name)
 146         value)))
 147
 148 (defun set-slot-value (object slot-name new-value)
 149   (let* ((wrapper (valid-wrapper-of object))
 150          (cell (or (find-slot-cell wrapper slot-name)
 151                    (return-from set-slot-value
 152                      (progn (slot-missing (wrapper-class* wrapper)
 153                                           object slot-name 'setf new-value)
 154                             new-value))))
 155          (location (car cell))
 156          (info (cdr cell))
 157          (typecheck (slot-info-typecheck info)))
 158     (when typecheck
 159       (funcall typecheck new-value))
 160     (cond ((fixnump location)
 161            (if (std-instance-p object)
 162                (setf (standard-instance-access object location) new-value)
 163                (setf (funcallable-standard-instance-access object location)
 164                      new-value)))
 165           ((not location)
 166            (funcall (slot-info-writer info) new-value object))
 167           ((listp location) ; forcibly transform CONSP to LISTP
 168            (setf (cdr location) new-value))
 169           (t
 170            (bug "Bogus slot-cell in SET-SLOT-VALUE: ~S" cell))))
 171   new-value)
 172
 173 ;;; A version of SET-SLOT-VALUE for use in safe code, where we want to
 174 ;;; check types when writing to slots:
 175 ;;;   * Doesn't have an optimizing compiler-macro
 176 ;;;   * Isn't special-cased in WALK-METHOD-LAMBDA
 177 (defun safe-set-slot-value (object slot-name new-value)
 178   (set-slot-value object slot-name new-value))
 179
 180 (defun (cas slot-value) (old-value new-value object slot-name)
 181   (let* ((wrapper (valid-wrapper-of object))
 182          (cell (or (find-slot-cell wrapper slot-name)
 183                    (return-from slot-value
 184                      (values (slot-missing (wrapper-class* wrapper) object slot-name
 185                                            'cas (list old-value new-value))))))
 186          (location (car cell))
 187          (info (cdr cell))
 188          (typecheck (slot-info-typecheck info)))
 189     (when typecheck
 190       (funcall typecheck new-value))
 191     (let ((old (cond ((fixnump location)
 192                       (if (std-instance-p object)
 193                           (cas (standard-instance-access object location) old-value new-value)
 194                           (cas (funcallable-standard-instance-access object location)
 195                                old-value new-value)))
 196                      ((not location)
 197                       ;; FIXME: (CAS SLOT-VALUE-USING-CLASS)...
 198                       (error "Cannot compare-and-swap slot ~S on: ~S" slot-name object))
 199                      ((listp location) ; forcibly transform CONSP to LISTP
 200                       (cas (cdr location) old-value new-value))
 201                      (t
 202                       (bug "Bogus slot-cell in (CAS SLOT-VALUE): ~S" cell)))))
 203       (if (and (unbound-marker-p old) (neq old old-value))
 204           (slot-unbound (wrapper-class* wrapper) object slot-name)
 205           old))))
 206
 207 (defun slot-boundp (object slot-name)
 208   (let* ((wrapper (valid-wrapper-of object))
 209          (cell (find-slot-cell wrapper slot-name))
 210          (location (car cell))
 211          (value
 212           (cond ((fixnump location)
 213                  (if (std-instance-p object)
 214                      (standard-instance-access object location)
 215                      (funcallable-standard-instance-access object location)))
 216                 ((not location)
 217                  (return-from slot-boundp
 218                    (if cell
 219                        (funcall (slot-info-boundp (cdr cell)) object)
 220                        (and (slot-missing (wrapper-class* wrapper) object
 221                                           slot-name 'slot-boundp)
 222                             t))))
 223                 ((listp location) ; forcibly transform CONSP to LISTP
 224                  (cdr location))
 225                 (t
 226                  (bug "Bogus slot cell in SLOT-VALUE: ~S" cell)))))
 227     (not (unbound-marker-p value))))
 228
 229 (defun slot-makunbound (object slot-name)
 230   (let* ((wrapper (valid-wrapper-of object))
 231          (cell (find-slot-cell wrapper slot-name))
 232          (location (car cell)))
 233     (cond ((fixnump location)
 234            (if (std-instance-p object)
 235                (setf (standard-instance-access object location) +slot-unbound+)
 236                (setf (funcallable-standard-instance-access object location)
 237                      +slot-unbound+)))
 238           ((not location)
 239            (if cell
 240                (let ((class (wrapper-class* wrapper)))
 241                  (slot-makunbound-using-class class object
 242                                               (find-slot-definition class slot-name)))
 243                (slot-missing (wrapper-class* wrapper) object slot-name
 244                              'slot-makunbound)))
 245           ((listp location) ; forcibly transform CONSP to LISTP
 246            (setf (cdr location) +slot-unbound+))
 247           (t
 248            (bug "Bogus slot-cell in SLOT-MAKUNBOUND: ~S" cell))))
 249   object)
 250
 251 ;; Note that CLHS "encourages" implementors to base this on
 252 ;; SLOT-EXISTS-P-USING-CLASS, whereas 88-002R made no such claim,
 253 ;; however Appendix D of AMOP sketches out such an implementation.
 254 (defun slot-exists-p (object slot-name)
 255   (not (null (find-slot-cell (valid-wrapper-of object) slot-name))))
 256
 257 (defun slot-value-for-printing (object slot-name)
 258   (if (slot-boundp object slot-name)
 259       (slot-value object slot-name)
 260       (load-time-value (make-unprintable-object "unbound slot") t)))
 261
 262 (defmethod slot-value-using-class ((class std-class)
 263                                    (object standard-object)
 264                                    (slotd standard-effective-slot-definition))
 265   ;; FIXME: Do we need this? SLOT-VALUE checks for obsolete
 266   ;; instances. Are users allowed to call this directly?
 267   (check-obsolete-instance object)
 268   (let* ((location (slot-definition-location slotd))
 269          (value
 270           (typecase location
 271             (fixnum
 272              (cond ((std-instance-p object)
 273                     (clos-slots-ref (std-instance-slots object)
 274                                     location))
 275                    ((fsc-instance-p object)
 276                     (clos-slots-ref (fsc-instance-slots object)
 277                                     location))
 278                    (t (bug "unrecognized instance type in ~S"
 279                            'slot-value-using-class))))
 280             (cons
 281              (cdr location))
 282             (t
 283              (instance-structure-protocol-error slotd
 284                                                 'slot-value-using-class)))))
 285     (if (unbound-marker-p value)
 286         (values (slot-unbound class object (slot-definition-name slotd)))
 287         value)))
 288
 289 (defmethod (setf slot-value-using-class)
 290            (new-value (class std-class)
 291                       (object standard-object)
 292                       (slotd standard-effective-slot-definition))
 293   ;; FIXME: Do we need this? SET-SLOT-VALUE checks for obsolete
 294   ;; instances. Are users allowed to call this directly?
 295   (check-obsolete-instance object)
 296   (let* ((info (slot-definition-info slotd))
 297          (location (slot-definition-location slotd))
 298          (typecheck (slot-info-typecheck info))
 299          (new-value (if typecheck
 300                         (funcall (the function typecheck) new-value)
 301                         new-value)))
 302     (typecase location
 303       (fixnum
 304        (cond ((std-instance-p object)
 305               (setf (clos-slots-ref (std-instance-slots object) location)
 306                     new-value))
 307              ((fsc-instance-p object)
 308               (setf (clos-slots-ref (fsc-instance-slots object) location)
 309                     new-value))
 310              (t (bug "unrecognized instance type in ~S"
 311                      '(setf slot-value-using-class)))))
 312       (cons
 313        (setf (cdr location) new-value))
 314       (t
 315        (instance-structure-protocol-error
 316         slotd '(setf slot-value-using-class))))))
 317
 318 (defmethod slot-boundp-using-class
 319            ((class std-class)
 320             (object standard-object)
 321             (slotd standard-effective-slot-definition))
 322   ;; FIXME: Do we need this? SLOT-BOUNDP checks for obsolete
 323   ;; instances. Are users allowed to call this directly?
 324   (check-obsolete-instance object)
 325   (let* ((location (slot-definition-location slotd))
 326          (value
 327           (typecase location
 328             (fixnum
 329              (cond ((std-instance-p object)
 330                           (clos-slots-ref (std-instance-slots object)
 331                                           location))
 332                    ((fsc-instance-p object)
 333                     (clos-slots-ref (fsc-instance-slots object)
 334                                     location))
 335                    (t (bug "unrecognized instance type in ~S"
 336                            'slot-boundp-using-class))))
 337             (cons
 338              (cdr location))
 339             (t
 340              (instance-structure-protocol-error slotd
 341                                                 'slot-boundp-using-class)))))
 342     (not (unbound-marker-p value))))
 343
 344 (defmethod slot-makunbound-using-class
 345            ((class std-class)
 346             (object standard-object)
 347             (slotd standard-effective-slot-definition))
 348   (check-obsolete-instance object)
 349   (let ((location (slot-definition-location slotd)))
 350     (typecase location
 351       (fixnum
 352        (cond ((std-instance-p object)
 353               (setf (clos-slots-ref (std-instance-slots object) location)
 354                     +slot-unbound+))
 355              ((fsc-instance-p object)
 356               (setf (clos-slots-ref (fsc-instance-slots object) location)
 357                     +slot-unbound+))
 358              (t (bug "unrecognized instance type in ~S"
 359                      'slot-makunbound-using-class))))
 360       (cons
 361        (setf (cdr location) +slot-unbound+))
 362       (t
 363        (instance-structure-protocol-error slotd
 364                                           'slot-makunbound-using-class))))
 365   object)
 366
 367 (defmethod slot-value-using-class
 368     ((class condition-class)
 369      (object condition)
 370      (slotd condition-effective-slot-definition))
 371   (let ((fun (slot-info-reader (slot-definition-info slotd))))
 372     (funcall fun object)))
 373
 374 (defmethod (setf slot-value-using-class)
 375     (new-value
 376      (class condition-class)
 377      (object condition)
 378      (slotd condition-effective-slot-definition))
 379   (let ((fun (slot-info-writer (slot-definition-info slotd))))
 380     (funcall fun new-value object)))
 381
 382 (defmethod slot-boundp-using-class
 383     ((class condition-class)
 384      (object condition)
 385      (slotd condition-effective-slot-definition))
 386   (let ((fun (slot-info-boundp (slot-definition-info slotd))))
 387     (funcall fun object)))
 388
 389 (defmethod slot-makunbound-using-class ((class condition-class) object slot)
 390   (error "attempt to unbind slot ~S in condition object ~S."
 391          slot object))
 392
 393 (defmethod slot-value-using-class
 394     ((class structure-class)
 395      (object structure-object)
 396      (slotd structure-effective-slot-definition))
 397   (let* ((function (slot-definition-internal-reader-function slotd))
 398          (value (funcall function object)))
 399     (declare (type function function))
 400     ;; FIXME: Is this really necessary? Structure slots should surely
 401     ;; never be unbound!
 402     (if (unbound-marker-p value)
 403         (values (slot-unbound class object (slot-definition-name slotd)))
 404         value)))
 405
 406 (defmethod (setf slot-value-using-class)
 407     (new-value (class structure-class)
 408                (object structure-object)
 409                (slotd structure-effective-slot-definition))
 410   (let ((function (slot-definition-internal-writer-function slotd)))
 411     (declare (type function function))
 412     (funcall function new-value object)))
 413
 414 (defmethod slot-boundp-using-class
 415            ((class structure-class)
 416             (object structure-object)
 417             (slotd structure-effective-slot-definition))
 418   t)
 419
 420 (defmethod slot-makunbound-using-class
 421            ((class structure-class)
 422             (object structure-object)
 423             (slotd structure-effective-slot-definition))
 424   (error "Structure slots can't be unbound."))
 425 \f
 426 (defmethod slot-missing
 427            ((class t) instance slot-name operation &optional new-value)
 428   (error "~@<When attempting to ~A, the slot ~S is missing from the ~
 429           object ~S.~@:>"
 430          (ecase operation
 431            (slot-value "read the slot's value (slot-value)")
 432            (setf (format nil
 433                          "set the slot's value to ~S (SETF of SLOT-VALUE)"
 434                          new-value))
 435            (slot-boundp "test to see whether slot is bound (SLOT-BOUNDP)")
 436            (slot-makunbound "make the slot unbound (SLOT-MAKUNBOUND)"))
 437          slot-name
 438          instance))
 439
 440 (defmethod slot-unbound ((class t) instance slot-name)
 441   (restart-case
 442       (error 'unbound-slot :name slot-name :instance instance)
 443     (use-value (v)
 444       :report "Return a value as the slot-value."
 445       :interactive read-evaluated-form
 446       v)
 447     (store-value (v)
 448       :report "Store and return a value as the slot-value."
 449       :interactive read-evaluated-form
 450       (setf (slot-value instance slot-name) v))))
 451
 452 (defun slot-unbound-internal (instance position)
 453   (values
 454    (slot-unbound
 455     (class-of instance)
 456     instance
 457     (etypecase position
 458       (fixnum
 459        ;; In the vast majority of cases location corresponds to the position
 460        ;; in list. The only exceptions are when there are non-local slots
 461        ;; before the one we want.
 462        (slot-definition-name
 463         (find position (layout-slot-list (layout-of instance))
 464               :key #'slot-definition-location)))
 465       (cons
 466        (car position))))))
 467 \f
 468 ;;; FIXME: AMOP says that allocate-instance implies finalize-inheritance
 469 ;;; if the class is not yet finalized, but we don't seem to be taking
 470 ;;; care of this for non-standard-classes.
 471 (defmethod allocate-instance ((class standard-class) &rest initargs)
 472   (declare (ignore initargs)
 473            (inline ensure-class-finalized))
 474   (allocate-standard-instance
 475    (class-wrapper (ensure-class-finalized class))))
 476
 477 (defmethod allocate-instance ((class structure-class) &rest initargs)
 478   (declare (ignore initargs))
 479   (let ((constructor (class-defstruct-constructor class)))
 480     (if constructor
 481         (funcall constructor)
 482         (error "Don't know how to allocate ~S" class))))
 483
 484 (defmethod allocate-instance ((class condition-class) &rest initargs)
 485   (declare (ignore initargs))
 486   (values (allocate-condition (class-name class))))
 487
 488 (defmethod allocate-instance ((class system-class) &rest initargs)
 489   (declare (ignore initargs))
 490   (error "Cannot allocate an instance of ~S." class))
 491
 492 ;;; AMOP says that CLASS-SLOTS signals an error for unfinalized classes.
 493 (defmethod class-slots :before ((class slot-class))
 494   (unless (class-finalized-p class)
 495     (error 'simple-reference-error
 496            :format-control "~S called on ~S, which is not yet finalized."
 497            :format-arguments (list 'class-slots class)
 498            :references (list '(:amop :generic-function class-slots)))))
 499
 500 (defun %set-slots (object names &rest values)
 501   (mapc (lambda (name value)
 502           (if (unbound-marker-p value)
 503               ;; SLOT-MAKUNBOUND-USING-CLASS might do something nonstandard.
 504               (slot-makunbound object name)
 505               (setf (slot-value object name) value)))
 506         names values))