X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fpcl%2Fstd-class.lisp;h=975acc43bf1f12dd1be9cb5f869121e9e7aa13b6;hb=441dfe5655f1ec3ee96e7b17b7cb1c7a4a906117;hp=ab1406f027c53f7b703d72d81089b04a677b88e2;hpb=8fe977ca5d0d068f2641dd06d3743a4c218d5cc1;p=sbcl.git

diff --git a/src/pcl/std-class.lisp b/src/pcl/std-class.lisp
index ab1406f..975acc4 100644
--- a/src/pcl/std-class.lisp
+++ b/src/pcl/std-class.lisp
@@ -24,18 +24,20 @@
 (in-package "SB-PCL")
 
 (defmethod slot-accessor-function ((slotd effective-slot-definition) type)
-  (ecase type
-    (reader (slot-definition-reader-function slotd))
-    (writer (slot-definition-writer-function slotd))
-    (boundp (slot-definition-boundp-function slotd))))
+  (let ((info (slot-definition-info slotd)))
+    (ecase type
+      (reader (slot-info-reader info))
+      (writer (slot-info-writer info))
+      (boundp (slot-info-boundp info)))))
 
 (defmethod (setf slot-accessor-function) (function
                                           (slotd effective-slot-definition)
                                           type)
-  (ecase type
-    (reader (setf (slot-definition-reader-function slotd) function))
-    (writer (setf (slot-definition-writer-function slotd) function))
-    (boundp (setf (slot-definition-boundp-function slotd) function))))
+  (let ((info (slot-definition-info slotd)))
+    (ecase type
+      (reader (setf (slot-info-reader info) function))
+      (writer (setf (slot-info-writer info) function))
+      (boundp (setf (slot-info-boundp info) function)))))
 
 (defconstant +slotd-reader-function-std-p+ 1)
 (defconstant +slotd-writer-function-std-p+ 2)
@@ -69,8 +71,8 @@
               (the fixnum (logand (the fixnum (lognot mask)) flags)))))
   value)
 
-(defmethod initialize-internal-slot-functions ((slotd
-                                                effective-slot-definition))
+(defmethod initialize-internal-slot-functions
+    ((slotd effective-slot-definition))
   (let* ((name (slot-value slotd 'name))
          (class (slot-value slotd '%class)))
     (dolist (type '(reader writer boundp))
@@ -79,7 +81,34 @@
                               (writer '(setf slot-value-using-class))
                               (boundp 'slot-boundp-using-class)))
              (gf (gdefinition gf-name)))
-        (compute-slot-accessor-info slotd type gf)))))
+        ;; KLUDGE: this logic is cut'n'pasted from
+        ;; GET-ACCESSOR-METHOD-FUNCTION, which (for STD-CLASSes) is
+        ;; only called later, because it does things that can't be
+        ;; computed this early in class finalization; however, we need
+        ;; this bit as early as possible.  -- CSR, 2009-11-05
+        (setf (slot-accessor-std-p slotd type)
+              (let* ((std-method (standard-svuc-method type))
+                     (str-method (structure-svuc-method type))
+                     (types1 `((eql ,class) (class-eq ,class) (eql ,slotd)))
+                     (types (if (eq type 'writer) `(t ,@types1) types1))
+                     (methods (compute-applicable-methods-using-types gf types)))
+                (null (cdr methods))))
+        (setf (slot-accessor-function slotd type)
+              (lambda (&rest args)
+                (declare (dynamic-extent args))
+                ;; FIXME: a tiny amount of wasted SLOT-ACCESSOR-STD-P
+                ;; work here (see KLUDGE comment above).
+                (let ((fun (compute-slot-accessor-info slotd type gf)))
+                  (apply fun args))))))))
+
+(defmethod finalize-internal-slot-functions ((slotd effective-slot-definition))
+  (dolist (type '(reader writer boundp))
+    (let* ((gf-name (ecase type
+                      (reader 'slot-value-using-class)
+                      (writer '(setf slot-value-using-class))
+                      (boundp 'slot-boundp-using-class)))
+           (gf (gdefinition gf-name)))
+      (compute-slot-accessor-info slotd type gf))))
 
 ;;; CMUCL (Gerd PCL 2003-04-25) comment:
 ;;;
@@ -98,12 +127,9 @@
 (defmethod compute-slot-accessor-info ((slotd effective-slot-definition)
                                        type gf)
   (let* ((name (slot-value slotd 'name))
-         (class (slot-value slotd '%class))
-         (old-slotd (when (class-finalized-p class)
-                      (find-slot-definition class name)))
-         (old-std-p (and old-slotd (slot-accessor-std-p old-slotd 'all))))
+         (class (slot-value slotd '%class)))
     (multiple-value-bind (function std-p)
-        (if (eq *boot-state* 'complete)
+        (if (eq **boot-state** 'complete)
             (get-accessor-method-function gf type class slotd)
             (get-optimized-std-accessor-method-function class slotd type))
       (setf (slot-accessor-std-p slotd type) std-p)
@@ -176,18 +202,18 @@
 ;;; This needs to be used recursively, in case a non-trivial user
 ;;; defined ADD/REMOVE-DIRECT-METHOD method ends up calling another
 ;;; function using the same lock.
-(defvar *specializer-lock* (sb-thread::make-spinlock :name "Specializer lock"))
+(defvar *specializer-lock* (sb-thread:make-mutex :name "Specializer lock"))
 
 (defmethod add-direct-method :around ((specializer specializer) method)
   ;; All the actions done under this lock are done in an order
   ;; that is safe to unwind at any point.
-  (sb-thread::with-recursive-spinlock (*specializer-lock*)
+  (sb-thread::with-recursive-system-lock (*specializer-lock*)
     (call-next-method)))
 
 (defmethod remove-direct-method :around ((specializer specializer) method)
   ;; All the actions done under this lock are done in an order
   ;; that is safe to unwind at any point.
-  (sb-thread::with-recursive-spinlock (*specializer-lock*)
+  (sb-thread::with-recursive-system-lock (*specializer-lock*)
     (call-next-method)))
 
 (defmethod add-direct-method ((specializer class) (method method))
@@ -218,7 +244,7 @@
     ;; we behave as if we got just first or just after -- it's just
     ;; for update that we need to lock.
     (or (cdr cell)
-        (sb-thread::with-spinlock (*specializer-lock*)
+        (sb-thread:with-mutex (*specializer-lock*)
           (setf (cdr cell)
                 (let (collect)
                   (dolist (m (car cell))
@@ -277,7 +303,7 @@
          (entry (gethash object (specializer-method-table specializer))))
     (when entry
       (or (cdr entry)
-          (sb-thread::with-spinlock (*specializer-lock*)
+          (sb-thread:with-mutex (*specializer-lock*)
             (setf (cdr entry)
                   (let (collect)
                     (dolist (m (car entry))
@@ -336,33 +362,40 @@
 (setf (gdefinition 'load-defclass) #'real-load-defclass)
 
 (defun ensure-class (name &rest args)
-  (apply #'ensure-class-using-class
-         (let ((class (find-class name nil)))
-           (when (and class (eq name (class-name class)))
-             ;; NAME is the proper name of CLASS, so redefine it
-             class))
-         name
-         args))
+  (with-world-lock ()
+    (apply #'ensure-class-using-class
+           (let ((class (find-class name nil)))
+             (when (and class (eq name (class-name class)))
+               ;; NAME is the proper name of CLASS, so redefine it
+               class))
+           name
+           args)))
 
 (defmethod ensure-class-using-class ((class null) name &rest args &key)
-  (multiple-value-bind (meta initargs)
-      (frob-ensure-class-args args)
-    (setf class (apply #'make-instance meta :name name initargs))
-    (without-package-locks
-      (setf (find-class name) class))
-    (set-class-type-translation class name)
-    class))
+  (with-world-lock ()
+    (multiple-value-bind (meta initargs)
+        (frob-ensure-class-args args)
+      (setf class (apply #'make-instance meta :name name initargs))
+      (without-package-locks
+        (setf (find-class name) class))))
+  ;; After boot (SETF FIND-CLASS) does this.
+  (unless (eq **boot-state** 'complete)
+    (%set-class-type-translation class name))
+  class)
 
 (defmethod ensure-class-using-class ((class pcl-class) name &rest args &key)
-  (multiple-value-bind (meta initargs)
-      (frob-ensure-class-args args)
-    (unless (eq (class-of class) meta)
-      (apply #'change-class class meta initargs))
-    (apply #'reinitialize-instance class initargs)
-    (without-package-locks
-      (setf (find-class name) class))
-    (set-class-type-translation class name)
-    class))
+  (with-world-lock ()
+    (multiple-value-bind (meta initargs)
+        (frob-ensure-class-args args)
+      (unless (eq (class-of class) meta)
+        (apply #'change-class class meta initargs))
+      (apply #'reinitialize-instance class initargs)
+      (without-package-locks
+        (setf (find-class name) class))))
+  ;; After boot (SETF FIND-CLASS) does this.
+  (unless (eq **boot-state** 'complete)
+    (%set-class-type-translation class name))
+  class)
 
 (defun frob-ensure-class-args (args)
   (let (metaclass metaclassp reversed-plist)
@@ -387,6 +420,17 @@
                          (find-class metaclass)))
                     (t *the-class-standard-class*))
               (nreverse reversed-plist)))))
+
+;;; This is used to call initfunctions of :allocation :class slots.
+(defun call-initfun (fun slotd safe)
+  (declare (function fun))
+  (let ((value (funcall fun)))
+    (when safe
+      (let ((type (slot-definition-type slotd)))
+        (unless (or (eq t type)
+                    (typep value type))
+          (error 'type-error :expected-type type :datum value))))
+    value))
 
 (defmethod shared-initialize :after
     ((class std-class) slot-names &key
@@ -406,8 +450,8 @@
                      super-class of the class ~S, ~
                      but the meta-classes ~S and ~S are incompatible.  ~
                      Define a method for ~S to avoid this error.~@:>"
-                     superclass class (class-of superclass) (class-of class)
-                     'validate-superclass)))
+                    superclass class (class-of superclass) (class-of class)
+                    'validate-superclass)))
          (setf (slot-value class 'direct-superclasses) direct-superclasses))
         (t
          (setq direct-superclasses (slot-value class 'direct-superclasses))))
@@ -424,6 +468,7 @@
             (plist-value class 'direct-default-initargs)))
   (setf (plist-value class 'class-slot-cells)
         (let ((old-class-slot-cells (plist-value class 'class-slot-cells))
+              (safe (safe-p class))
               (collect '()))
           (dolist (dslotd direct-slots)
             (when (eq :class (slot-definition-allocation dslotd))
@@ -434,9 +479,10 @@
                         (eq t slot-names)
                         (member name slot-names :test #'eq))
                     (let* ((initfunction (slot-definition-initfunction dslotd))
-                           (value (if initfunction
-                                      (funcall initfunction)
-                                      +slot-unbound+)))
+                           (value
+                            (if initfunction
+                                (call-initfun initfunction dslotd safe)
+                                +slot-unbound+)))
                       (push (cons name value) collect))
                     (push old collect)))))
           (nreverse collect)))
@@ -461,24 +507,25 @@
   (flet ((compute-preliminary-cpl (root)
            (let ((*allow-forward-referenced-classes-in-cpl-p* t))
              (compute-class-precedence-list root))))
-    (without-package-locks
-     (unless (class-finalized-p class)
-       (let ((name (class-name class)))
-         ;; KLUDGE: This is fairly horrible.  We need to make a
-         ;; full-fledged CLASSOID here, not just tell the compiler that
-         ;; some class is forthcoming, because there are legitimate
-         ;; questions one can ask of the type system, implemented in
-         ;; terms of CLASSOIDs, involving forward-referenced classes. So.
-         (let ((layout (make-wrapper 0 class)))
-           (setf (slot-value class 'wrapper) layout)
-           (let ((cpl (compute-preliminary-cpl class)))
-             (setf (layout-inherits layout)
-                   (order-layout-inherits
-                    (map 'simple-vector #'class-wrapper
-                         (reverse (rest cpl))))))
-           (register-layout layout :invalidate t)
-           (set-class-type-translation class (layout-classoid layout)))))
-     (mapc #'make-preliminary-layout (class-direct-subclasses class)))))
+    (with-world-lock ()
+      (without-package-locks
+        (unless (class-finalized-p class)
+          (let ((name (class-name class)))
+            ;; KLUDGE: This is fairly horrible.  We need to make a
+            ;; full-fledged CLASSOID here, not just tell the compiler that
+            ;; some class is forthcoming, because there are legitimate
+            ;; questions one can ask of the type system, implemented in
+            ;; terms of CLASSOIDs, involving forward-referenced classes. So.
+            (let ((layout (make-wrapper 0 class)))
+              (setf (slot-value class 'wrapper) layout)
+              (let ((cpl (compute-preliminary-cpl class)))
+                (setf (layout-inherits layout)
+                      (order-layout-inherits
+                       (map 'simple-vector #'class-wrapper
+                            (reverse (rest cpl))))))
+              (register-layout layout :invalidate t)
+              (%set-class-type-translation class (layout-classoid layout)))))
+        (mapc #'make-preliminary-layout (class-direct-subclasses class))))))
 
 
 (defmethod shared-initialize :before ((class class) slot-names &key name)
@@ -492,7 +539,7 @@
 (defmethod reinitialize-instance :before ((class slot-class) &key direct-superclasses)
   (dolist (old-super (set-difference (class-direct-superclasses class) direct-superclasses))
     (remove-direct-subclass old-super class))
-  (remove-slot-accessors    class (class-direct-slots class)))
+  (remove-slot-accessors class (class-direct-slots class)))
 
 (defmethod reinitialize-instance :after ((class slot-class)
                                          &rest initargs
@@ -520,18 +567,22 @@
                                      &key direct-slots direct-superclasses)
   (declare (ignore slot-names))
   (let ((classoid (find-classoid (slot-value class 'name))))
-    (with-slots (wrapper %class-precedence-list cpl-available-p
-                         prototype (direct-supers direct-superclasses))
+    (with-slots (wrapper
+                 %class-precedence-list cpl-available-p finalized-p
+                 prototype (direct-supers direct-superclasses)
+                 plist)
         class
       (setf (slot-value class 'direct-slots)
             (mapcar (lambda (pl) (make-direct-slotd class pl))
-                    direct-slots))
-      (setf (slot-value class 'finalized-p) t)
-      (setf (classoid-pcl-class classoid) class)
-      (setq direct-supers direct-superclasses)
-      (setq wrapper (classoid-layout classoid))
-      (setq %class-precedence-list (compute-class-precedence-list class))
-      (setq cpl-available-p t)
+                    direct-slots)
+            finalized-p t
+            (classoid-pcl-class classoid) class
+            direct-supers direct-superclasses
+            wrapper (classoid-layout classoid)
+            %class-precedence-list (compute-class-precedence-list class)
+            cpl-available-p t
+            (getf plist 'direct-default-initargs)
+            (sb-kernel::condition-classoid-direct-default-initargs classoid))
       (add-direct-subclasses class direct-superclasses)
       (let ((slots (compute-slots class)))
         (setf (slot-value class 'slots) slots)
@@ -567,18 +618,19 @@
 
 (defmethod compute-effective-slot-definition
     ((class condition-class) slot-name dslotds)
-  (let ((slotd (call-next-method)))
-    (setf (slot-definition-reader-function slotd)
+  (let* ((slotd (call-next-method))
+         (info (slot-definition-info slotd)))
+    (setf (slot-info-reader info)
           (lambda (x)
             (handler-case (condition-reader-function x slot-name)
               ;; FIXME: FIND-SLOT-DEFAULT throws an error if the slot
               ;; is unbound; maybe it should be a CELL-ERROR of some
               ;; sort?
               (error () (values (slot-unbound class x slot-name))))))
-    (setf (slot-definition-writer-function slotd)
+    (setf (slot-info-writer info)
           (lambda (v x)
             (condition-writer-function x v slot-name)))
-    (setf (slot-definition-boundp-function slotd)
+    (setf (slot-info-boundp info)
           (lambda (x)
             (multiple-value-bind (v c)
                 (ignore-errors (condition-reader-function x slot-name))
@@ -596,7 +648,7 @@
 
 (defmethod compute-slots :around ((class condition-class))
   (let ((eslotds (call-next-method)))
-    (mapc #'initialize-internal-slot-functions eslotds)
+    (mapc #'finalize-internal-slot-functions eslotds)
     eslotds))
 
 (defmethod shared-initialize :after
@@ -609,51 +661,59 @@
 (defun make-structure-class-defstruct-form (name direct-slots include)
   (let* ((conc-name (format-symbol *package* "~S structure class " name))
          (constructor (format-symbol *package* "~Aconstructor" conc-name))
-         (defstruct `(defstruct (,name
-                                 ,@(when include
-                                         `((:include ,(class-name include))))
-                                 (:predicate nil)
-                                 (:conc-name ,conc-name)
-                                 (:constructor ,constructor ())
-                                 (:copier nil))
-                      ,@(mapcar (lambda (slot)
-                                  `(,(slot-definition-name slot)
-                                    +slot-unbound+))
-                                direct-slots)))
-         (reader-names (mapcar (lambda (slotd)
-                                 (list 'slot-accessor name
-                                       (slot-definition-name slotd)
-                                       'reader))
-                               direct-slots))
-         (writer-names (mapcar (lambda (slotd)
-                                 (list 'slot-accessor name
-                                       (slot-definition-name slotd)
-                                       'writer))
-                               direct-slots))
-         (readers-init
-           (mapcar (lambda (slotd reader-name)
-                     (let ((accessor
+         (included-name (class-name include))
+         (included-slots
+          (when include
+            (mapcar #'dsd-name (dd-slots (find-defstruct-description included-name)))))
+         (old-slots nil)
+         (new-slots nil)
+         (reader-names nil)
+         (writer-names nil))
+    (dolist (slotd (reverse direct-slots))
+      (let* ((slot-name (slot-definition-name slotd))
+             (initform (slot-definition-initform slotd))
+             (type (slot-definition-type slotd))
+             (desc `(,slot-name ,initform :type ,type)))
+        (push `(slot-accessor ,name ,slot-name reader)
+              reader-names)
+        (push `(slot-accessor ,name ,slot-name writer)
+              writer-names)
+        (if (member slot-name included-slots :test #'eq)
+            (push desc old-slots)
+            (push desc new-slots))))
+    (let* ((defstruct `(defstruct (,name
+                                    ,@(when include
+                                            `((:include ,included-name
+                                                        ,@old-slots)))
+                                    (:constructor ,constructor ())
+                                    (:predicate nil)
+                                    (:conc-name ,conc-name)
+                                    (:copier nil))
+                         ,@new-slots))
+           (readers-init
+            (mapcar (lambda (slotd reader-name)
+                      (let ((accessor
                              (slot-definition-defstruct-accessor-symbol
                               slotd)))
-                       `(defun ,reader-name (obj)
-                         (declare (type ,name obj))
-                         (,accessor obj))))
-                   direct-slots reader-names))
-         (writers-init
-           (mapcar (lambda (slotd writer-name)
-                     (let ((accessor
+                        `(defun ,reader-name (obj)
+                           (declare (type ,name obj))
+                           (,accessor obj))))
+                    direct-slots reader-names))
+           (writers-init
+            (mapcar (lambda (slotd writer-name)
+                      (let ((accessor
                              (slot-definition-defstruct-accessor-symbol
                               slotd)))
-                       `(defun ,writer-name (nv obj)
-                         (declare (type ,name obj))
-                         (setf (,accessor obj) nv))))
-                   direct-slots writer-names))
-         (defstruct-form
-             `(progn
+                        `(defun ,writer-name (nv obj)
+                           (declare (type ,name obj))
+                           (setf (,accessor obj) nv))))
+                    direct-slots writer-names))
+           (defstruct-form
+            `(progn
                ,defstruct
                ,@readers-init ,@writers-init
                (cons nil nil))))
-    (values defstruct-form constructor reader-names writer-names)))
+      (values defstruct-form constructor reader-names writer-names))))
 
 (defun make-defstruct-allocation-function (name)
   ;; FIXME: Why don't we go class->layout->info == dd
@@ -789,7 +849,8 @@
 
 
 (defun class-has-a-forward-referenced-superclass-p (class)
-  (or (forward-referenced-class-p class)
+  (or (when (forward-referenced-class-p class)
+        class)
       (some #'class-has-a-forward-referenced-superclass-p
             (class-direct-superclasses class))))
 
@@ -797,16 +858,17 @@
 ;;; or reinitialized. The class may or may not be finalized.
 (defun update-class (class finalizep)
   (without-package-locks
-    (when (or finalizep (class-finalized-p class))
-      (update-cpl class (compute-class-precedence-list class))
-      ;; This invocation of UPDATE-SLOTS, in practice, finalizes the
-      ;; class.
-      (update-slots class (compute-slots class))
-      (update-gfs-of-class class)
-      (update-initargs class (compute-default-initargs class))
-      (update-ctors 'finalize-inheritance :class class))
-    (dolist (sub (class-direct-subclasses class))
-      (update-class sub nil))))
+    (with-world-lock ()
+      (when (or finalizep (class-finalized-p class))
+        (%update-cpl class (compute-class-precedence-list class))
+        ;; This invocation of UPDATE-SLOTS, in practice, finalizes the
+        ;; class.
+        (%update-slots class (compute-slots class))
+        (update-gfs-of-class class)
+        (setf (plist-value class 'default-initargs) (compute-default-initargs class))
+        (update-ctors 'finalize-inheritance :class class))
+      (dolist (sub (class-direct-subclasses class))
+        (update-class sub nil)))))
 
 (define-condition cpl-protocol-violation (reference-condition error)
   ((class :initarg :class :reader cpl-protocol-violation-class)
@@ -824,7 +886,20 @@
              (find-class 'function)
              (cpl-protocol-violation-cpl c)))))
 
-(defun update-cpl (class cpl)
+(defun class-has-a-cpl-protocol-violation-p (class)
+  (labels ((find-in-superclasses (class classes)
+             (cond
+               ((null classes) nil)
+               ((eql class (car classes)) t)
+               (t (find-in-superclasses class (append (class-direct-superclasses (car classes)) (cdr classes)))))))
+    (let ((metaclass (class-of class)))
+      (cond
+        ((eql metaclass *the-class-standard-class*)
+         (find-in-superclasses (find-class 'function) (list class)))
+        ((eql metaclass *the-class-funcallable-standard-class*)
+         (not (find-in-superclasses (find-class 'function) (list class))))))))
+
+(defun %update-cpl (class cpl)
   (when (eq (class-of class) *the-class-standard-class*)
     (when (find (find-class 'function) cpl)
       (error 'cpl-protocol-violation :class class :cpl cpl)))
@@ -838,11 +913,11 @@
                                      :key #'slot-definition-allocation)
                        (return nil))))
         ;; comment from the old CMU CL sources:
-        ;;   Need to have the cpl setup before update-lisp-class-layout
+        ;;   Need to have the cpl setup before %update-lisp-class-layout
         ;;   is called on CMU CL.
         (setf (slot-value class '%class-precedence-list) cpl)
         (setf (slot-value class 'cpl-available-p) t)
-        (force-cache-flushes class))
+        (%force-cache-flushes class))
       (progn
         (setf (slot-value class '%class-precedence-list) cpl)
         (setf (slot-value class 'cpl-available-p) t)))
@@ -858,82 +933,111 @@
 (defun class-can-precede-p (class1 class2)
   (member class2 (class-can-precede-list class1) :test #'eq))
 
-(defun update-slots (class eslotds)
-  (let ((instance-slots ())
-        (class-slots    ()))
-    (dolist (eslotd eslotds)
-      (let ((alloc (slot-definition-allocation eslotd)))
-        (case alloc
-          (:instance (push eslotd instance-slots))
-          (:class (push eslotd class-slots)))))
-
-    ;; If there is a change in the shape of the instances then the
-    ;; old class is now obsolete.
-    (let* ((nlayout (mapcar #'slot-definition-name
-                            (sort instance-slots #'<
-                                  :key #'slot-definition-location)))
-           (nslots (length nlayout))
-           (nwrapper-class-slots (compute-class-slots class-slots))
-           (owrapper (when (class-finalized-p class)
-                       (class-wrapper class)))
-           (olayout (when owrapper
-                      (wrapper-instance-slots-layout owrapper)))
-           (owrapper-class-slots (and owrapper (wrapper-class-slots owrapper)))
+;;; This is called from %UPDATE-SLOTS to check if slot layouts are compatible.
+;;;
+;;; In addition to slot locations (implicit in the ordering of the slots), we
+;;; must check classes: SLOT-INFO structures from old slotds may have been
+;;; cached in permutation vectors, but new slotds have had new ones allocated
+;;; to them. This is non-problematic for standard slotds, because we know the
+;;; structure is compatible, but if a slot definition class changes, this can
+;;; change the way SLOT-VALUE-USING-CLASS should dispatch.
+;;;
+;;; Also, if the slot has a non-standard allocation, we need to check that it
+;;; doesn't change.
+(defun slot-layouts-compatible-p
+    (oslotds new-instance-slotds new-class-slotds new-custom-slotds)
+  (multiple-value-bind (old-instance-slotds old-class-slotds old-custom-slotds)
+      (classify-slotds oslotds)
+    (and
+     ;; Instance slots: name, type, and class.
+     (dolist (o old-instance-slotds (not new-instance-slotds))
+       (let ((n (pop new-instance-slotds)))
+         (unless (and n
+                      (eq (slot-definition-name o) (slot-definition-name n))
+                      (eq (slot-definition-type o) (slot-definition-type n))
+                      (eq (class-of o) (class-of n)))
+           (return nil))))
+     ;; Class slots: name and class. (FIXME: class slots not typechecked?)
+     (dolist (o old-class-slotds (not new-class-slotds))
+       (let ((n (pop new-class-slotds)))
+         (unless (and n
+                      (eq (slot-definition-name o) (slot-definition-name n))
+                      (eq (class-of n) (class-of o)))
+           (return nil))))
+     ;; Custom slots: check name, type, allocation, and class. (FIXME: should we just punt?)
+     (dolist (o old-custom-slotds (not new-custom-slotds))
+       (let ((n (pop new-custom-slotds)))
+         (unless (and n
+                      (eq (slot-definition-name o) (slot-definition-name n))
+                      (eq (slot-definition-type o) (slot-definition-type n))
+                      (eq (slot-definition-allocation o) (slot-definition-allocation n))
+                      (eq (class-of o) (class-of n)))
+           (return nil)))))))
+
+(defun style-warn-about-duplicate-slots (class)
+  (do* ((slots (slot-value class 'slots) (cdr slots))
+        (dupes nil))
+       ((null slots)
+        (when dupes
+          (style-warn
+           "~@<slot names with the same SYMBOL-NAME but ~
+                  different SYMBOL-PACKAGE (possible package problem) ~
+                  for class ~S:~4I~@:_~<~@{~/sb-impl::print-symbol-with-prefix/~^~:@_~}~:>~@:>"
+           class dupes)))
+    (let* ((slot-name (slot-definition-name (car slots)))
+           (oslots (and (not (eq (symbol-package slot-name)
+                                 *pcl-package*))
+                        (remove-if
+                         (lambda (slot-name-2)
+                           (or (eq (symbol-package slot-name-2)
+                                   *pcl-package*)
+                               (string/= slot-name slot-name-2)))
+                         (cdr slots)
+                         :key #'slot-definition-name))))
+      (when oslots
+        (pushnew (cons slot-name
+                       (mapcar #'slot-definition-name oslots))
+                 dupes
+                 :test #'string= :key #'car)))))
+
+(defun %update-slots (class eslotds)
+  (multiple-value-bind (instance-slots class-slots custom-slots)
+      (classify-slotds eslotds)
+    (let* ((nslots (length instance-slots))
+           (owrapper (when (class-finalized-p class) (class-wrapper class)))
            (nwrapper
-            (cond ((null owrapper)
-                   (make-wrapper nslots class))
-                  ((and (equal nlayout olayout)
-                        (not
-                         (loop for o in owrapper-class-slots
-                               for n in nwrapper-class-slots
-                               do (unless (eq (car o) (car n)) (return t)))))
-                   owrapper)
-                  (t
-                   ;; This will initialize the new wrapper to have the
-                   ;; same state as the old wrapper. We will then have
-                   ;; to change that. This may seem like wasted work
-                   ;; (and it is), but the spec requires that we call
-                   ;; MAKE-INSTANCES-OBSOLETE.
-                   (make-instances-obsolete class)
-                   (class-wrapper class)))))
-
-      (update-lisp-class-layout class nwrapper)
+             (cond ((null owrapper)
+                    (make-wrapper nslots class))
+                   ((slot-layouts-compatible-p (wrapper-slots owrapper)
+                                               instance-slots class-slots custom-slots)
+                    owrapper)
+                   (t
+                    ;; This will initialize the new wrapper to have the
+                    ;; same state as the old wrapper. We will then have
+                    ;; to change that. This may seem like wasted work
+                    ;; (and it is), but the spec requires that we call
+                    ;; MAKE-INSTANCES-OBSOLETE.
+                    (make-instances-obsolete class)
+                    (class-wrapper class)))))
+      (%update-lisp-class-layout class nwrapper)
       (setf (slot-value class 'slots) eslotds
+            (wrapper-slots nwrapper) eslotds
             (wrapper-slot-table nwrapper) (make-slot-table class eslotds)
-            (wrapper-instance-slots-layout nwrapper) nlayout
-            (wrapper-class-slots nwrapper) nwrapper-class-slots
             (wrapper-length nwrapper) nslots
             (slot-value class 'wrapper) nwrapper)
-      (do* ((slots (slot-value class 'slots) (cdr slots))
-            (dupes nil))
-           ((null slots)
-            (when dupes
-              (style-warn
-               "~@<slot names with the same SYMBOL-NAME but ~
-                  different SYMBOL-PACKAGE (possible package problem) ~
-                  for class ~S:~4I~@:_~<~@{~S~^~:@_~}~:>~@:>"
-               class dupes)))
-        (let* ((slot (car slots))
-               (oslots (remove (slot-definition-name slot) (cdr slots)
-                               :test #'string/=
-                               :key #'slot-definition-name)))
-          (when oslots
-            (pushnew (cons (slot-definition-name slot)
-                           (mapcar #'slot-definition-name oslots))
-                     dupes
-                     :test #'string= :key #'car))))
+      (style-warn-about-duplicate-slots class)
       (setf (slot-value class 'finalized-p) t)
       (unless (eq owrapper nwrapper)
-        (maybe-update-standard-class-locations class)))))
+        (maybe-update-standard-slot-locations class)))))
 
-(defun compute-class-slots (eslotds)
-  (let (collect)
-    (dolist (eslotd eslotds (nreverse collect))
-      (let ((cell (assoc (slot-definition-name eslotd)
-                         (class-slot-cells
-                          (slot-definition-allocation-class eslotd)))))
-        (aver cell)
-        (push cell collect)))))
+(defun update-gf-dfun (class gf)
+  (let ((*new-class* class)
+        (arg-info (gf-arg-info gf)))
+    (cond
+      ((special-case-for-compute-discriminating-function-p gf))
+      ((gf-precompute-dfun-and-emf-p arg-info)
+       (multiple-value-bind (dfun cache info) (make-final-dfun-internal gf)
+         (update-dfun gf dfun cache info))))))
 
 (defun update-gfs-of-class (class)
   (when (and (class-finalized-p class)
@@ -951,9 +1055,6 @@
                    (declare (ignore ignore))
                    (update-gf-dfun class gf))
                  gf-table)))))
-
-(defun update-initargs (class inits)
-  (setf (plist-value class 'default-initargs) inits))
 
 (defmethod compute-default-initargs ((class slot-class))
   (let ((initargs (loop for c in (class-precedence-list class)
@@ -1005,7 +1106,8 @@
   (std-compute-slots class))
 
 (defun std-compute-slots-around (class eslotds)
-  (let ((location -1))
+  (let ((location -1)
+        (safe (safe-p class)))
     (dolist (eslotd eslotds eslotds)
       (setf (slot-definition-location eslotd)
             (case (slot-definition-allocation eslotd)
@@ -1029,10 +1131,12 @@
                                   c))))
                  (aver (consp cell))
                  (if (eq +slot-unbound+ (cdr cell))
-                     ;; We may have inherited an initfunction
+                     ;; We may have inherited an initfunction FIXME: Is this
+                     ;; really right? Is the initialization in
+                     ;; SHARED-INITIALIZE (STD-CLASS) not enough?
                      (let ((initfun (slot-definition-initfunction eslotd)))
                        (if initfun
-                           (rplacd cell (funcall initfun))
+                           (rplacd cell (call-initfun initfun eslotd safe))
                            cell))
                      cell)))))
       (unless (slot-definition-class eslotd)
@@ -1058,14 +1162,14 @@
 
 (defmethod compute-slots :around ((class structure-class))
   (let ((eslotds (call-next-method)))
-    (mapc #'initialize-internal-slot-functions eslotds)
+    (mapc #'finalize-internal-slot-functions eslotds)
     eslotds))
 
 (defmethod compute-effective-slot-definition ((class slot-class) name dslotds)
-  (declare (ignore name))
   (let* ((initargs (compute-effective-slot-definition-initargs class dslotds))
-         (class (apply #'effective-slot-definition-class class initargs)))
-    (apply #'make-instance class initargs)))
+         (class (apply #'effective-slot-definition-class class initargs))
+         (slotd (apply #'make-instance class initargs)))
+    slotd))
 
 (defmethod effective-slot-definition-class ((class std-class) &rest initargs)
   (declare (ignore initargs))
@@ -1084,7 +1188,6 @@
          (allocation nil)
          (allocation-class nil)
          (type t)
-         (type-check-function nil)
          (documentation nil)
          (documentationp nil)
          (namep  nil)
@@ -1097,28 +1200,19 @@
           (setq name (slot-definition-name slotd)
                 namep t))
         (unless initp
-          (when (slot-definition-initfunction slotd)
+          (awhen (slot-definition-initfunction slotd)
             (setq initform (slot-definition-initform slotd)
-                  initfunction (slot-definition-initfunction slotd)
+                  initfunction it
                   initp t)))
         (unless documentationp
-          (when (%slot-definition-documentation slotd)
-            (setq documentation (%slot-definition-documentation slotd)
+          (awhen (%slot-definition-documentation slotd)
+            (setq documentation it
                   documentationp t)))
         (unless allocp
           (setq allocation (slot-definition-allocation slotd)
                 allocation-class (slot-definition-class slotd)
                 allocp t))
         (setq initargs (append (slot-definition-initargs slotd) initargs))
-        (let ((fun (slot-definition-type-check-function slotd)))
-          (when fun
-            (setf type-check-function
-                  (if type-check-function
-                      (let ((old-function type-check-function))
-                        (lambda (value)
-                          (funcall old-function value)
-                          (funcall fun value)))
-                      fun))))
         (let ((slotd-type (slot-definition-type slotd)))
           (setq type (cond
                        ((eq type t) slotd-type)
@@ -1135,15 +1229,14 @@
           :allocation allocation
           :allocation-class allocation-class
           :type type
-          'type-check-function type-check-function
           :class class
           :documentation documentation)))
 
 (defmethod compute-effective-slot-definition-initargs :around
     ((class structure-class) direct-slotds)
-  (let ((slotd (car direct-slotds)))
-    (list* :defstruct-accessor-symbol
-           (slot-definition-defstruct-accessor-symbol slotd)
+  (let* ((slotd (car direct-slotds))
+         (accessor (slot-definition-defstruct-accessor-symbol slotd)))
+    (list* :defstruct-accessor-symbol accessor
            :internal-reader-function
            (slot-definition-internal-reader-function slotd)
            :internal-writer-function
@@ -1265,7 +1358,7 @@
 ;;;                    :UNINITIALIZED)))
 ;;;
 ;;; Thanks to Gerd Moellmann for the explanation.  -- CSR, 2002-10-29
-(defun force-cache-flushes (class)
+(defun %force-cache-flushes (class)
   (let* ((owrapper (class-wrapper class)))
     ;; We only need to do something if the wrapper is still valid. If
     ;; the wrapper isn't valid, state will be FLUSH or OBSOLETE, and
@@ -1280,49 +1373,40 @@
               (eq (layout-invalid owrapper) t))
       (let ((nwrapper (make-wrapper (layout-length owrapper)
                                     class)))
-        (setf (wrapper-instance-slots-layout nwrapper)
-              (wrapper-instance-slots-layout owrapper))
-        (setf (wrapper-class-slots nwrapper)
-              (wrapper-class-slots owrapper))
+        (setf (wrapper-slots nwrapper)
+              (wrapper-slots owrapper))
         (setf (wrapper-slot-table nwrapper)
               (wrapper-slot-table owrapper))
-        (with-pcl-lock
-          (update-lisp-class-layout class nwrapper)
-          (setf (slot-value class 'wrapper) nwrapper)
-          ;; Use :OBSOLETE instead of :FLUSH if any superclass has
-          ;; been obsoleted.
-          (if (find-if (lambda (x)
-                         (and (consp x) (eq :obsolete (car x))))
-                       (layout-inherits owrapper)
-                       :key #'layout-invalid)
-              (invalidate-wrapper owrapper :obsolete nwrapper)
-              (invalidate-wrapper owrapper :flush nwrapper)))))))
-
-(defun flush-cache-trap (owrapper nwrapper instance)
-  (declare (ignore owrapper))
-  (set-wrapper instance nwrapper))
+        (%update-lisp-class-layout class nwrapper)
+        (setf (slot-value class 'wrapper) nwrapper)
+        ;; Use :OBSOLETE instead of :FLUSH if any superclass has
+        ;; been obsoleted.
+        (if (find-if (lambda (x)
+                       (and (consp x) (eq :obsolete (car x))))
+                     (layout-inherits owrapper)
+                     :key #'layout-invalid)
+            (%invalidate-wrapper owrapper :obsolete nwrapper)
+            (%invalidate-wrapper owrapper :flush nwrapper))))))
 
 ;;; MAKE-INSTANCES-OBSOLETE can be called by user code. It will cause
 ;;; the next access to the instance (as defined in 88-002R) to trap
 ;;; through the UPDATE-INSTANCE-FOR-REDEFINED-CLASS mechanism.
 (defmethod make-instances-obsolete ((class std-class))
-  (let* ((owrapper (class-wrapper class))
-         (nwrapper (make-wrapper (layout-length owrapper)
-                                 class)))
-    (unless (class-finalized-p class)
-      (if (class-has-a-forward-referenced-superclass-p class)
-          (return-from make-instances-obsolete class)
-          (update-cpl class (compute-class-precedence-list class))))
-    (setf (wrapper-instance-slots-layout nwrapper)
-          (wrapper-instance-slots-layout owrapper))
-    (setf (wrapper-class-slots nwrapper)
-          (wrapper-class-slots owrapper))
-    (setf (wrapper-slot-table nwrapper)
-          (wrapper-slot-table owrapper))
-    (with-pcl-lock
-        (update-lisp-class-layout class nwrapper)
+  (with-world-lock ()
+    (let* ((owrapper (class-wrapper class))
+           (nwrapper (make-wrapper (layout-length owrapper)
+                                   class)))
+      (unless (class-finalized-p class)
+        (if (class-has-a-forward-referenced-superclass-p class)
+            (return-from make-instances-obsolete class)
+            (%update-cpl class (compute-class-precedence-list class))))
+      (setf (wrapper-slots nwrapper)
+            (wrapper-slots owrapper))
+      (setf (wrapper-slot-table nwrapper)
+            (wrapper-slot-table owrapper))
+      (%update-lisp-class-layout class nwrapper)
       (setf (slot-value class 'wrapper) nwrapper)
-      (invalidate-wrapper owrapper :obsolete nwrapper)
+      (%invalidate-wrapper owrapper :obsolete nwrapper)
       class)))
 
 (defmethod make-instances-obsolete ((class symbol))
@@ -1370,60 +1454,96 @@
              "~@<obsolete structure error for a structure of type ~2I~_~S~:>"
              (type-of (obsolete-structure-datum condition))))))
 
-(defun obsolete-instance-trap (owrapper nwrapper instance)
+(defun %obsolete-instance-trap (owrapper nwrapper instance)
   (if (not (layout-for-std-class-p owrapper))
       (if *in-obsolete-instance-trap*
           *the-wrapper-of-structure-object*
-           (let ((*in-obsolete-instance-trap* t))
-             (error 'obsolete-structure :datum instance)))
+          (let ((*in-obsolete-instance-trap* t))
+            (error 'obsolete-structure :datum instance)))
       (let* ((class (wrapper-class* nwrapper))
              (copy (allocate-instance class)) ;??? allocate-instance ???
-             (olayout (wrapper-instance-slots-layout owrapper))
-             (nlayout (wrapper-instance-slots-layout nwrapper))
              (oslots (get-slots instance))
              (nslots (get-slots copy))
-             (oclass-slots (wrapper-class-slots owrapper))
              (added ())
              (discarded ())
-             (plist ()))
+             (plist ())
+             (safe (safe-p class)))
 
-        ;; local  --> local     transfer value
+        ;; local  --> local     transfer value, check type
         ;; local  --> shared    discard value, discard slot
         ;; local  -->  --       discard slot
-        ;; shared --> local     transfer value
+        ;; local  --> custom    XXX
+
+        ;; shared --> local     transfer value, check type
         ;; shared --> shared    -- (cf SHARED-INITIALIZE :AFTER STD-CLASS)
         ;; shared -->  --       discard value
+        ;; shared --> custom    XXX
+
         ;;  --    --> local     add slot
         ;;  --    --> shared    --
-
-        ;; Go through all the old local slots.
-        (let ((opos 0))
-          (dolist (name olayout)
-            (let ((npos (posq name nlayout)))
-              (if npos
-                  (setf (clos-slots-ref nslots npos)
-                        (clos-slots-ref oslots opos))
-                  (progn
-                    (push name discarded)
-                    (unless (eq (clos-slots-ref oslots opos) +slot-unbound+)
-                      (setf (getf plist name) (clos-slots-ref oslots opos))))))
-            (incf opos)))
-
-        ;; Go through all the old shared slots.
-        (dolist (oclass-slot-and-val oclass-slots)
-          (let ((name (car oclass-slot-and-val))
-                (val (cdr oclass-slot-and-val)))
-            (let ((npos (posq name nlayout)))
-              (when npos
-                (setf (clos-slots-ref nslots npos) val)))))
-
-        ;; Go through all the new local slots to compute the added slots.
-        (dolist (nlocal nlayout)
-          (unless (or (memq nlocal olayout)
-                      (assq nlocal oclass-slots))
-            (push nlocal added)))
-
-        (swap-wrappers-and-slots instance copy)
+        ;;  --    --> custom    XXX
+
+        (multiple-value-bind (new-instance-slots new-class-slots new-custom-slots)
+            (classify-slotds (wrapper-slots nwrapper))
+          (declare (ignore new-class-slots))
+          (multiple-value-bind (old-instance-slots old-class-slots old-custom-slots)
+              (classify-slotds (wrapper-slots owrapper))
+
+            (let ((layout (mapcar (lambda (slotd)
+                                    ;; Get the names only once.
+                                    (cons (slot-definition-name slotd) slotd))
+                                  new-instance-slots)))
+
+              (flet ((set-value (value cell)
+                       (let ((name (car cell))
+                             (slotd (cdr cell)))
+                         (when (and safe (neq value +slot-unbound+))
+                           (let ((type (slot-definition-type slotd)))
+                             (assert
+                              (typep value type) (value)
+                              "~@<Error updating obsolete instance. Current value in slot ~
+                               ~S of an instance of ~S is ~S, which does not match the new ~
+                               slot type ~S.~:@>"
+                              name class value type)))
+                         (setf (clos-slots-ref nslots (slot-definition-location slotd)) value
+                               ;; Prune from the list now that it's been dealt with.
+                               layout (remove cell layout)))))
+
+                ;; Go through all the old local slots.
+                (dolist (old old-instance-slots)
+                  (let* ((name (slot-definition-name old))
+                         (value (clos-slots-ref oslots (slot-definition-location old))))
+                    (unless (eq value +slot-unbound+)
+                      (let ((new (assq name layout)))
+                        (cond (new
+                               (set-value value new))
+                              (t
+                               (push name discarded)
+                               (setf (getf plist name) value)))))))
+
+                ;; Go through all the old shared slots.
+                (dolist (old old-class-slots)
+                  (let* ((cell (slot-definition-location old))
+                         (name (car cell))
+                         (new (assq name layout)))
+                    (when new
+                      (set-value (cdr cell) new))))
+
+                ;; Go through all custom slots to find added ones. CLHS
+                ;; doesn't specify what to do about them, and neither does
+                ;; AMOP. We do want them to get initialized, though, so we
+                ;; list them in ADDED for the benefit of SHARED-INITIALIZE.
+                (dolist (new new-custom-slots)
+                  (let* ((name (slot-definition-name new))
+                         (old (find name old-custom-slots :key #'slot-definition-name)))
+                    (unless old
+                      (push name added))))
+
+                ;; Go through all the remaining new local slots to compute the added slots.
+                (dolist (cell layout)
+                  (push (car cell) added))))))
+
+        (%swap-wrappers-and-slots instance copy)
 
         (update-instance-for-redefined-class instance
                                              added
@@ -1431,94 +1551,111 @@
                                              plist)
         nwrapper)))
 
-(defun change-class-internal (instance new-class initargs)
+(defun %change-class (instance new-class initargs)
   (let* ((old-class (class-of instance))
          (copy (allocate-instance new-class))
          (new-wrapper (get-wrapper copy))
          (old-wrapper (class-wrapper old-class))
-         (old-layout (wrapper-instance-slots-layout old-wrapper))
-         (new-layout (wrapper-instance-slots-layout new-wrapper))
          (old-slots (get-slots instance))
          (new-slots (get-slots copy))
-         (old-class-slots (wrapper-class-slots old-wrapper)))
-
-    ;; "The values of local slots specified by both the class CTO and
-    ;; CFROM are retained. If such a local slot was unbound, it
-    ;; remains unbound."
-    (let ((new-position 0))
-      (dolist (new-slot new-layout)
-        (let ((old-position (posq new-slot old-layout)))
-          (when old-position
-            (setf (clos-slots-ref new-slots new-position)
-                  (clos-slots-ref old-slots old-position))))
-        (incf new-position)))
-
-    ;; "The values of slots specified as shared in the class CFROM and
-    ;; as local in the class CTO are retained."
-    (dolist (slot-and-val old-class-slots)
-      (let ((position (posq (car slot-and-val) new-layout)))
-        (when position
-          (setf (clos-slots-ref new-slots position) (cdr slot-and-val)))))
+         (safe (safe-p new-class)))
+    (multiple-value-bind (new-instance-slots new-class-slots)
+        (classify-slotds (wrapper-slots new-wrapper))
+      (multiple-value-bind (old-instance-slots old-class-slots)
+          (classify-slotds (wrapper-slots old-wrapper))
+
+        (flet ((set-value (value slotd)
+                 (when safe
+                   (assert (typep value (slot-definition-type slotd)) (value)
+                           "~@<Error changing class. Current value in slot ~S ~
+                            of an instance of ~S is ~S, which does not match the new ~
+                            slot type ~S in class ~S.~:@>"
+                           (slot-definition-name slotd) old-class value
+                           (slot-definition-type slotd) new-class))
+                 (setf (clos-slots-ref new-slots (slot-definition-location slotd)) value)))
+
+          ;; "The values of local slots specified by both the class CTO and
+          ;; CFROM are retained. If such a local slot was unbound, it
+          ;; remains unbound."
+          (dolist (new new-instance-slots)
+            (let* ((name (slot-definition-name new))
+                   (old (find name old-instance-slots :key #'slot-definition-name)))
+              (when old
+                (set-value (clos-slots-ref old-slots (slot-definition-location old))
+                           new))))
+
+          ;; "The values of slots specified as shared in the class CFROM and
+          ;; as local in the class CTO are retained."
+          (dolist (old old-class-slots)
+            (let* ((slot-and-val (slot-definition-location old))
+                   (new (find (car slot-and-val) new-instance-slots
+                              :key #'slot-definition-name)))
+              (when new
+                (set-value (cdr slot-and-val) new)))))))
 
     ;; Make the copy point to the old instance's storage, and make the
     ;; old instance point to the new storage.
-    (swap-wrappers-and-slots instance copy)
+    (%swap-wrappers-and-slots instance copy)
 
     (apply #'update-instance-for-different-class copy instance initargs)
+
     instance))
 
 (defmethod change-class ((instance standard-object) (new-class standard-class)
                          &rest initargs)
-  (unless (class-finalized-p new-class)
-    (finalize-inheritance new-class))
-  (let ((cpl (class-precedence-list new-class)))
-    (dolist (class cpl)
-      (macrolet
-          ((frob (class-name)
-             `(when (eq class (find-class ',class-name))
-               (error 'metaobject-initialization-violation
-                :format-control "~@<Cannot ~S objects into ~S metaobjects.~@:>"
-                :format-arguments (list 'change-class ',class-name)
-                :references (list '(:amop :initialization ,class-name))))))
-        (frob class)
-        (frob generic-function)
-        (frob method)
-        (frob slot-definition))))
-  (change-class-internal instance new-class initargs))
+  (with-world-lock ()
+    (unless (class-finalized-p new-class)
+      (finalize-inheritance new-class))
+    (let ((cpl (class-precedence-list new-class)))
+      (dolist (class cpl)
+        (macrolet
+            ((frob (class-name)
+               `(when (eq class (find-class ',class-name))
+                  (error 'metaobject-initialization-violation
+                         :format-control "~@<Cannot ~S objects into ~S metaobjects.~@:>"
+                         :format-arguments (list 'change-class ',class-name)
+                         :references (list '(:amop :initialization ,class-name))))))
+          (frob class)
+          (frob generic-function)
+          (frob method)
+          (frob slot-definition))))
+    (%change-class instance new-class initargs)))
 
 (defmethod change-class ((instance forward-referenced-class)
                          (new-class standard-class) &rest initargs)
-  (let ((cpl (class-precedence-list new-class)))
-    (dolist (class cpl
-             (error 'metaobject-initialization-violation
-                    :format-control
-                    "~@<Cannot ~S ~S objects into non-~S objects.~@:>"
-                    :format-arguments
-                    (list 'change-class 'forward-referenced-class 'class)
-                    :references
-                    (list '(:amop :generic-function ensure-class-using-class)
-                          '(:amop :initialization class))))
-      (when (eq class (find-class 'class))
-        (return nil))))
-  (change-class-internal instance new-class initargs))
+  (with-world-lock ()
+    (let ((cpl (class-precedence-list new-class)))
+      (dolist (class cpl
+               (error 'metaobject-initialization-violation
+                      :format-control
+                      "~@<Cannot ~S ~S objects into non-~S objects.~@:>"
+                      :format-arguments
+                      (list 'change-class 'forward-referenced-class 'class)
+                      :references
+                      (list '(:amop :generic-function ensure-class-using-class)
+                            '(:amop :initialization class))))
+        (when (eq class (find-class 'class))
+          (return nil))))
+    (%change-class instance new-class initargs)))
 
 (defmethod change-class ((instance funcallable-standard-object)
                          (new-class funcallable-standard-class)
                          &rest initargs)
-  (let ((cpl (class-precedence-list new-class)))
-    (dolist (class cpl)
-      (macrolet
-          ((frob (class-name)
-             `(when (eq class (find-class ',class-name))
-               (error 'metaobject-initialization-violation
-                :format-control "~@<Cannot ~S objects into ~S metaobjects.~@:>"
-                :format-arguments (list 'change-class ',class-name)
-                :references (list '(:amop :initialization ,class-name))))))
-        (frob class)
-        (frob generic-function)
-        (frob method)
-        (frob slot-definition))))
-  (change-class-internal instance new-class initargs))
+  (with-world-lock ()
+    (let ((cpl (class-precedence-list new-class)))
+      (dolist (class cpl)
+        (macrolet
+            ((frob (class-name)
+               `(when (eq class (find-class ',class-name))
+                  (error 'metaobject-initialization-violation
+                         :format-control "~@<Cannot ~S objects into ~S metaobjects.~@:>"
+                         :format-arguments (list 'change-class ',class-name)
+                         :references (list '(:amop :initialization ,class-name))))))
+          (frob class)
+          (frob generic-function)
+          (frob method)
+          (frob slot-definition))))
+    (%change-class instance new-class initargs)))
 
 (defmethod change-class ((instance standard-object)
                          (new-class funcallable-standard-class)