X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fpcl%2Fstd-class.lisp;h=b077674b651c04e41100741b3a2e8afde63fed3c;hb=7ce5108fd5ec5b599d4ae9e8aedc1a0d458af102;hp=b07aa0c791d15e33dbe96c852f0caf920c1a985c;hpb=203b88cf40ed2e15ec0f36dc53ad188b091d9ab2;p=sbcl.git

diff --git a/src/pcl/std-class.lisp b/src/pcl/std-class.lisp
index b07aa0c..b077674 100644
--- a/src/pcl/std-class.lisp
+++ b/src/pcl/std-class.lisp
@@ -181,13 +181,13 @@
 (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-spinlock (*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-spinlock (*specializer-lock*)
     (call-next-method)))
 
 (defmethod add-direct-method ((specializer class) (method method))
@@ -336,33 +336,40 @@
 (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 +394,15 @@
                          (find-class metaclass)))
                     (t *the-class-standard-class*))
               (nreverse reversed-plist)))))
+
+(defun call-initfun (fun slotd safe)
+  (declare (function fun))
+  (let ((value (funcall fun)))
+    (when safe
+      (let ((typecheck (slot-definition-type-check-function slotd)))
+        (when typecheck
+          (funcall (the function typecheck) value))))
+    value))
 
 (defmethod shared-initialize :after
     ((class std-class) slot-names &key
@@ -406,8 +422,8 @@
                      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 +440,7 @@
             (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 +451,10 @@
                         (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 +479,25 @@
   (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)
@@ -609,51 +628,59 @@
 (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
@@ -797,16 +824,17 @@
 ;;; 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 +852,7 @@
              (find-class 'function)
              (cpl-protocol-violation-cpl c)))))
 
-(defun update-cpl (class cpl)
+(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 +866,11 @@
                                      :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)))
@@ -858,7 +886,7 @@
 (defun class-can-precede-p (class1 class2)
   (member class2 (class-can-precede-list class1) :test #'eq))
 
-(defun update-slots (class eslotds)
+(defun %update-slots (class eslotds)
   (let ((instance-slots ())
         (class-slots    ()))
     (dolist (eslotd eslotds)
@@ -897,7 +925,7 @@
                    (make-instances-obsolete class)
                    (class-wrapper class)))))
 
-      (update-lisp-class-layout class nwrapper)
+      (%update-lisp-class-layout class nwrapper)
       (setf (slot-value class 'slots) eslotds
             (wrapper-slot-table nwrapper) (make-slot-table class eslotds)
             (wrapper-instance-slots-layout nwrapper) nlayout
@@ -924,7 +952,7 @@
                      :test #'string= :key #'car))))
       (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)
@@ -935,6 +963,15 @@
         (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)
              (let ((cpl (class-precedence-list class)))
@@ -951,9 +988,6 @@
                    (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 +1039,8 @@
   (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 +1064,12 @@
                                   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)
@@ -1266,7 +1303,7 @@
 ;;;                    :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
@@ -1287,43 +1324,38 @@
               (wrapper-class-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-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))
+      (%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))
@@ -1371,12 +1403,12 @@
              "~@<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))
@@ -1424,7 +1456,7 @@
                       (assq nlocal oclass-slots))
             (push nlocal added)))
 
-        (swap-wrappers-and-slots instance copy)
+        (%swap-wrappers-and-slots instance copy)
 
         (update-instance-for-redefined-class instance
                                              added
@@ -1432,7 +1464,7 @@
                                              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))
@@ -1463,63 +1495,67 @@
 
     ;; 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)