diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 3d5ae08dcca4..3518950e0c24 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -1467,7 +1467,7 @@ JS_ResolveStandardClass(JSContext *cx, JSObject *obj, jsval id,
          */
         if (stdnm->clasp &&
             (stdnm->clasp->flags & JSCLASS_IS_ANONYMOUS) &&
-            (OBJ_GET_CLASS(cx, obj)->flags & JSCLASS_IS_GLOBAL)) {
+            (obj->getClass()->flags & JSCLASS_IS_GLOBAL)) {
             return JS_TRUE;
         }
 
@@ -2633,7 +2633,7 @@ JS_InstanceOf(JSContext *cx, JSObject *obj, JSClass *clasp, jsval *argv)
     JSFunction *fun;
 
     CHECK_REQUEST(cx);
-    if (obj && OBJ_GET_CLASS(cx, obj) == clasp)
+    if (obj && obj->getClass() == clasp)
         return JS_TRUE;
     if (argv) {
         fun = js_ValueToFunction(cx, &argv[-2], 0);
@@ -2642,7 +2642,7 @@ JS_InstanceOf(JSContext *cx, JSObject *obj, JSClass *clasp, jsval *argv)
                                  JSMSG_INCOMPATIBLE_PROTO,
                                  clasp->name, JS_GetFunctionName(fun),
                                  obj
-                                 ? OBJ_GET_CLASS(cx, obj)->name
+                                 ? obj->getClass()->name
                                  : js_null_str);
         }
     }
@@ -2726,7 +2726,7 @@ JS_GetConstructor(JSContext *cx, JSObject *proto)
     }
     if (!VALUE_IS_FUNCTION(cx, cval)) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_NO_CONSTRUCTOR,
-                             OBJ_GET_CLASS(cx, proto)->name);
+                             proto->getClass()->name);
         return NULL;
     }
     return JSVAL_TO_OBJECT(cval);
@@ -2773,7 +2773,7 @@ JS_SealObject(JSContext *cx, JSObject *obj, JSBool deep)
     if (!obj->isNative()) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                              JSMSG_CANT_SEAL_OBJECT,
-                             OBJ_GET_CLASS(cx, obj)->name);
+                             obj->getClass()->name);
         return JS_FALSE;
     }
 
@@ -3048,7 +3048,7 @@ JS_AliasProperty(JSContext *cx, JSObject *obj, const char *name,
     if (obj2 != obj || !obj->isNative()) {
         obj2->dropProperty(cx, prop);
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_CANT_ALIAS,
-                             alias, name, OBJ_GET_CLASS(cx, obj2)->name);
+                             alias, name, obj2->getClass()->name);
         return JS_FALSE;
     }
     atom = js_Atomize(cx, alias, strlen(alias), 0);
@@ -3732,7 +3732,7 @@ JS_AliasElement(JSContext *cx, JSObject *obj, const char *name, jsint alias)
         obj2->dropProperty(cx, prop);
         JS_snprintf(numBuf, sizeof numBuf, "%ld", (long)alias);
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_CANT_ALIAS,
-                             numBuf, name, OBJ_GET_CLASS(cx, obj2)->name);
+                             numBuf, name, obj2->getClass()->name);
         return JS_FALSE;
     }
     sprop = (JSScopeProperty *)prop;
@@ -3827,7 +3827,7 @@ JS_ClearScope(JSContext *cx, JSObject *obj)
         obj->map->ops->clear(cx, obj);
 
     /* Clear cached class objects on the global object. */
-    if (OBJ_GET_CLASS(cx, obj)->flags & JSCLASS_IS_GLOBAL) {
+    if (obj->getClass()->flags & JSCLASS_IS_GLOBAL) {
         int key;
 
         for (key = JSProto_Null; key < JSProto_LIMIT; key++)
@@ -4134,7 +4134,7 @@ JS_CloneFunctionObject(JSContext *cx, JSObject *funobj, JSObject *parent)
         JS_ASSERT(parent);
     }
 
-    if (OBJ_GET_CLASS(cx, funobj) != &js_FunctionClass) {
+    if (funobj->getClass() != &js_FunctionClass) {
         /*
          * We cannot clone this object, so fail (we used to return funobj, bad
          * idea, but we changed incompatibly to teach any abusers a lesson!).
@@ -4238,7 +4238,7 @@ JS_GetFunctionArity(JSFunction *fun)
 JS_PUBLIC_API(JSBool)
 JS_ObjectIsFunction(JSContext *cx, JSObject *obj)
 {
-    return OBJ_GET_CLASS(cx, obj) == &js_FunctionClass;
+    return obj->getClass() == &js_FunctionClass;
 }
 
 JS_BEGIN_EXTERN_C
diff --git a/js/src/jsarray.cpp b/js/src/jsarray.cpp
index 9556a17242c2..82c09c70a4b7 100644
--- a/js/src/jsarray.cpp
+++ b/js/src/jsarray.cpp
@@ -128,7 +128,7 @@ INDEX_TOO_BIG(jsuint index)
 JS_STATIC_ASSERT(sizeof(JSScopeProperty) > 4 * sizeof(jsval));
 
 #define ENSURE_SLOW_ARRAY(cx, obj)                                             \
-    (OBJ_GET_CLASS(cx, obj) == &js_SlowArrayClass || js_MakeArraySlow(cx, obj))
+    (obj->getClass() == &js_SlowArrayClass || js_MakeArraySlow(cx, obj))
 
 /*
  * Determine if the id represents an array index or an XML property index.
@@ -298,7 +298,7 @@ BigIndexToId(JSContext *cx, JSObject *obj, jsuint index, JSBool createAtom,
      * in any case.
      */
     if (!createAtom &&
-        ((clasp = OBJ_GET_CLASS(cx, obj)) == &js_SlowArrayClass ||
+        ((clasp = obj->getClass()) == &js_SlowArrayClass ||
          clasp == &js_ArgumentsClass ||
          clasp == &js_ObjectClass)) {
         atom = js_GetExistingStringAtom(cx, start, JS_ARRAY_END(buf) - start);
@@ -1378,7 +1378,7 @@ array_toSource(JSContext *cx, uintN argc, jsval *vp)
 
     JSObject *obj = JS_THIS_OBJECT(cx, vp);
     if (!obj ||
-        (OBJ_GET_CLASS(cx, obj) != &js_SlowArrayClass &&
+        (obj->getClass() != &js_SlowArrayClass &&
          !JS_InstanceOf(cx, obj, &js_ArrayClass, vp + 2))) {
         return false;
     }
@@ -1584,7 +1584,7 @@ array_toString(JSContext *cx, uintN argc, jsval *vp)
 
     obj = JS_THIS_OBJECT(cx, vp);
     if (!obj ||
-        (OBJ_GET_CLASS(cx, obj) != &js_SlowArrayClass &&
+        (obj->getClass() != &js_SlowArrayClass &&
          !JS_InstanceOf(cx, obj, &js_ArrayClass, vp + 2))) {
         return JS_FALSE;
     }
@@ -1599,7 +1599,7 @@ array_toLocaleString(JSContext *cx, uintN argc, jsval *vp)
 
     obj = JS_THIS_OBJECT(cx, vp);
     if (!obj ||
-        (OBJ_GET_CLASS(cx, obj) != &js_SlowArrayClass &&
+        (obj->getClass() != &js_SlowArrayClass &&
          !JS_InstanceOf(cx, obj, &js_ArrayClass, vp + 2))) {
         return JS_FALSE;
     }
diff --git a/js/src/jsbuiltins.cpp b/js/src/jsbuiltins.cpp
index 4095a12e5fd2..f68ff5c57b3e 100644
--- a/js/src/jsbuiltins.cpp
+++ b/js/src/jsbuiltins.cpp
@@ -218,7 +218,7 @@ js_AddProperty(JSContext* cx, JSObject* obj, JSScopeProperty* sprop)
     }
 
     if (!scope->table) {
-        if (slot < obj->numSlots() && !OBJ_GET_CLASS(cx, obj)->reserveSlots) {
+        if (slot < obj->numSlots() && !obj->getClass()->reserveSlots) {
             JS_ASSERT(JSVAL_IS_VOID(obj->getSlot(scope->freeslot)));
             ++scope->freeslot;
         } else {
@@ -260,7 +260,7 @@ HasProperty(JSContext* cx, JSObject* obj, jsid id)
     for (JSObject* pobj = obj; pobj; pobj = pobj->getProto()) {
         if (pobj->map->ops->lookupProperty != js_LookupProperty)
             return JSVAL_TO_SPECIAL(JSVAL_VOID);
-        JSClass* clasp = OBJ_GET_CLASS(cx, pobj);
+        JSClass* clasp = pobj->getClass();
         if (clasp->resolve != JS_ResolveStub && clasp != &js_StringClass)
             return JSVAL_TO_SPECIAL(JSVAL_VOID);
     }
diff --git a/js/src/jsdate.cpp b/js/src/jsdate.cpp
index 994a5009bf1d..7755c82be036 100644
--- a/js/src/jsdate.cpp
+++ b/js/src/jsdate.cpp
@@ -1216,7 +1216,7 @@ GetUTCTime(JSContext *cx, JSObject *obj, jsval *vp, jsdouble *dp)
 static void
 SetDateToNaN(JSContext *cx, JSObject *obj, jsval *vp = NULL)
 {
-    JS_ASSERT(OBJ_GET_CLASS(cx, obj) == &js_DateClass);
+    JS_ASSERT(obj->getClass() == &js_DateClass);
 
     obj->fslots[JSSLOT_LOCAL_TIME] = cx->runtime->NaNValue;
     obj->fslots[JSSLOT_UTC_TIME] = cx->runtime->NaNValue;
@@ -1230,7 +1230,7 @@ SetDateToNaN(JSContext *cx, JSObject *obj, jsval *vp = NULL)
 static JSBool
 SetUTCTime(JSContext *cx, JSObject *obj, jsdouble t, jsval *vp = NULL)
 {
-    JS_ASSERT(OBJ_GET_CLASS(cx, obj) == &js_DateClass);
+    JS_ASSERT(obj->getClass() == &js_DateClass);
 
     obj->fslots[JSSLOT_LOCAL_TIME] = cx->runtime->NaNValue;
     if (!js_NewDoubleInRootedValue(cx, t, &obj->fslots[JSSLOT_UTC_TIME]))
diff --git a/js/src/jsdbgapi.cpp b/js/src/jsdbgapi.cpp
index f6ab235ce258..35be394d3492 100644
--- a/js/src/jsdbgapi.cpp
+++ b/js/src/jsdbgapi.cpp
@@ -658,7 +658,7 @@ js_watch_set(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
                 JSFrameRegs regs;
 
                 closure = wp->closure;
-                clasp = OBJ_GET_CLASS(cx, closure);
+                clasp = closure->getClass();
                 if (clasp == &js_FunctionClass) {
                     fun = GET_FUNCTION_PRIVATE(cx, closure);
                     script = FUN_SCRIPT(fun);
@@ -848,7 +848,7 @@ JS_SetWatchPoint(JSContext *cx, JSObject *obj, jsval idval,
 
     if (!obj->isNative()) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_CANT_WATCH,
-                             OBJ_GET_CLASS(cx, obj)->name);
+                             obj->getClass()->name);
         return JS_FALSE;
     }
 
@@ -1500,7 +1500,7 @@ JS_GetPropertyDescArray(JSContext *cx, JSObject *obj, JSPropertyDescArray *pda)
     JSPropertyDesc *pd;
     JSScopeProperty *sprop;
 
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
     if (!obj->isNative() || (clasp->flags & JSCLASS_NEW_ENUMERATE)) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                              JSMSG_CANT_DESCRIBE_PROPS, clasp->name);
diff --git a/js/src/jsexn.cpp b/js/src/jsexn.cpp
index 80daa9223a7e..26101bf4d5f4 100644
--- a/js/src/jsexn.cpp
+++ b/js/src/jsexn.cpp
@@ -260,7 +260,7 @@ InitExnPrivate(JSContext *cx, JSObject *exnObject, JSString *message,
     JSStackTraceElem *elem;
     jsval *values;
 
-    JS_ASSERT(OBJ_GET_CLASS(cx, exnObject) == &js_ErrorClass);
+    JS_ASSERT(exnObject->getClass() == &js_ErrorClass);
 
     /*
      * Prepare stack trace data.
@@ -511,7 +511,7 @@ js_ErrorFromException(JSContext *cx, jsval exn)
     if (JSVAL_IS_PRIMITIVE(exn))
         return NULL;
     obj = JSVAL_TO_OBJECT(exn);
-    if (OBJ_GET_CLASS(cx, obj) != &js_ErrorClass)
+    if (obj->getClass() != &js_ErrorClass)
         return NULL;
     priv = GetExnPrivate(cx, obj);
     if (!priv)
@@ -547,7 +547,7 @@ ValueToShortSource(JSContext *cx, jsval v)
          */
         char buf[100];
         JS_snprintf(buf, sizeof buf, "[object %s]",
-                    OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(v))->name);
+                    JSVAL_TO_OBJECT(v)->getClass()->name);
         str = JS_NewStringCopyZ(cx, buf);
     }
     return str;
@@ -713,7 +713,7 @@ Exception(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
      * If it's a new object of class Exception, then null out the private
      * data so that the finalizer doesn't attempt to free it.
      */
-    if (OBJ_GET_CLASS(cx, obj) == &js_ErrorClass)
+    if (obj->getClass() == &js_ErrorClass)
         obj->setPrivate(NULL);
 
     /* Set the 'message' property. */
@@ -755,7 +755,7 @@ Exception(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
         lineno = (fp && fp->regs) ? js_FramePCToLineNumber(cx, fp) : 0;
     }
 
-    return (OBJ_GET_CLASS(cx, obj) != &js_ErrorClass) ||
+    return (obj->getClass() != &js_ErrorClass) ||
             InitExnPrivate(cx, obj, message, filename, lineno, NULL);
 }
 
diff --git a/js/src/jsfun.cpp b/js/src/jsfun.cpp
index 3d3c1f54ecec..d2d09786d6ac 100644
--- a/js/src/jsfun.cpp
+++ b/js/src/jsfun.cpp
@@ -809,7 +809,7 @@ js_GetCallObject(JSContext *cx, JSStackFrame *fp)
 
 #ifdef DEBUG
     /* A call object should be a frame's outermost scope chain element.  */
-    JSClass *classp = OBJ_GET_CLASS(cx, fp->scopeChain);
+    JSClass *classp = fp->scopeChain->getClass();
     if (classp == &js_WithClass || classp == &js_BlockClass || classp == &js_CallClass)
         JS_ASSERT(fp->scopeChain->getPrivate() != fp);
 #endif
@@ -1914,8 +1914,7 @@ fun_toStringHelper(JSContext *cx, uint32 indent, uintN argc, jsval *vp)
          */
         if (!JSVAL_IS_PRIMITIVE(fval)) {
             obj = JSVAL_TO_OBJECT(fval);
-            if (!OBJ_GET_CLASS(cx, obj)->convert(cx, obj, JSTYPE_FUNCTION,
-                                                 &fval)) {
+            if (!obj->getClass()->convert(cx, obj, JSTYPE_FUNCTION, &fval)) {
                 return JS_FALSE;
             }
             vp[1] = fval;
@@ -2639,7 +2638,7 @@ js_ValueToFunction(JSContext *cx, jsval *vp, uintN flags)
     obj = NULL;
     if (JSVAL_IS_OBJECT(v)) {
         obj = JSVAL_TO_OBJECT(v);
-        if (obj && OBJ_GET_CLASS(cx, obj) != &js_FunctionClass) {
+        if (obj && obj->getClass() != &js_FunctionClass) {
             if (!obj->defaultValue(cx, JSTYPE_FUNCTION, &v))
                 return NULL;
             obj = VALUE_IS_FUNCTION(cx, v) ? JSVAL_TO_OBJECT(v) : NULL;
diff --git a/js/src/jsinterp.cpp b/js/src/jsinterp.cpp
index 6f9c5baf99a4..c429becf2dd6 100644
--- a/js/src/jsinterp.cpp
+++ b/js/src/jsinterp.cpp
@@ -260,7 +260,7 @@ js_GetScopeChain(JSContext *cx, JSStackFrame *fp)
      */
     JSObject *limitBlock, *limitClone;
     if (fp->fun && !fp->callobj) {
-        JS_ASSERT(OBJ_GET_CLASS(cx, fp->scopeChain) != &js_BlockClass ||
+        JS_ASSERT(fp->scopeChain->getClass() != &js_BlockClass ||
                   fp->scopeChain->getPrivate() != fp);
         if (!js_GetCallObject(cx, fp))
             return NULL;
@@ -275,7 +275,7 @@ js_GetScopeChain(JSContext *cx, JSStackFrame *fp)
          * to, but not including, that prototype.
          */
         limitClone = fp->scopeChain;
-        while (OBJ_GET_CLASS(cx, limitClone) == &js_WithClass)
+        while (limitClone->getClass() == &js_WithClass)
             limitClone = limitClone->getParent();
         JS_ASSERT(limitClone);
 
@@ -346,7 +346,7 @@ js_GetScopeChain(JSContext *cx, JSStackFrame *fp)
      * found it in blockChain.
      */
     JS_ASSERT_IF(limitBlock &&
-                 OBJ_GET_CLASS(cx, limitBlock) == &js_BlockClass &&
+                 limitBlock->getClass() == &js_BlockClass &&
                  limitClone->getPrivate() == fp,
                  sharedBlock);
 
@@ -427,7 +427,7 @@ ComputeThis(JSContext *cx, jsval *argv)
     } 
 
     thisp = JSVAL_TO_OBJECT(argv[-1]);
-    if (OBJ_GET_CLASS(cx, thisp) == &js_CallClass || OBJ_GET_CLASS(cx, thisp) == &js_BlockClass)
+    if (thisp->getClass() == &js_CallClass || thisp->getClass() == &js_BlockClass)
         return js_ComputeGlobalThis(cx, argv);
 
     return CallThisObjectHook(cx, thisp, argv);
@@ -1312,7 +1312,7 @@ js_InvokeConstructor(JSContext *cx, uintN argc, JSBool clampReturn, jsval *vp)
     if (!JSVAL_IS_OBJECT(lval) ||
         (obj2 = JSVAL_TO_OBJECT(lval)) == NULL ||
         /* XXX clean up to avoid special cases above ObjectOps layer */
-        OBJ_GET_CLASS(cx, obj2) == &js_FunctionClass ||
+        obj2->getClass() == &js_FunctionClass ||
         !obj2->map->ops->construct)
     {
         fun = js_ValueToFunction(cx, vp, JSV2F_CONSTRUCT);
@@ -1440,7 +1440,7 @@ js_LeaveWith(JSContext *cx)
     JSObject *withobj;
 
     withobj = cx->fp->scopeChain;
-    JS_ASSERT(OBJ_GET_CLASS(cx, withobj) == &js_WithClass);
+    JS_ASSERT(withobj->getClass() == &js_WithClass);
     JS_ASSERT(withobj->getPrivate() == cx->fp);
     JS_ASSERT(OBJ_BLOCK_DEPTH(cx, withobj) >= 0);
     cx->fp->scopeChain = withobj->getParent();
@@ -1452,7 +1452,7 @@ js_IsActiveWithOrBlock(JSContext *cx, JSObject *obj, int stackDepth)
 {
     JSClass *clasp;
 
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
     if ((clasp == &js_WithClass || clasp == &js_BlockClass) &&
         obj->getPrivate() == cx->fp &&
         OBJ_BLOCK_DEPTH(cx, obj) >= stackDepth) {
@@ -1476,7 +1476,7 @@ js_UnwindScope(JSContext *cx, JSStackFrame *fp, jsint stackDepth,
     JS_ASSERT(StackBase(fp) + stackDepth <= fp->regs->sp);
 
     for (obj = fp->blockChain; obj; obj = obj->getParent()) {
-        JS_ASSERT(OBJ_GET_CLASS(cx, obj) == &js_BlockClass);
+        JS_ASSERT(obj->getClass() == &js_BlockClass);
         if (OBJ_BLOCK_DEPTH(cx, obj) < stackDepth)
             break;
     }
diff --git a/js/src/jsiter.cpp b/js/src/jsiter.cpp
index 55688b0ced8e..9a7b03a0be11 100644
--- a/js/src/jsiter.cpp
+++ b/js/src/jsiter.cpp
@@ -327,7 +327,7 @@ static JSFunctionSpec iterator_methods[] = {
 uintN
 js_GetNativeIteratorFlags(JSContext *cx, JSObject *iterobj)
 {
-    if (OBJ_GET_CLASS(cx, iterobj) != &js_IteratorClass)
+    if (iterobj->getClass() != &js_IteratorClass)
         return 0;
     return JSVAL_TO_INT(iterobj->getSlot(JSSLOT_ITER_FLAGS));
 }
@@ -377,7 +377,7 @@ js_ValueToIterator(JSContext *cx, uintN flags, jsval *vp)
 
     tvr.setObject(obj);
 
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
     if ((clasp->flags & JSCLASS_IS_EXTENDED) &&
         (xclasp = (JSExtendedClass *) clasp)->iteratorObject) {
         iterobj = xclasp->iteratorObject(cx, obj, !(flags & JSITER_FOREACH));
@@ -430,7 +430,7 @@ js_CloseIterator(JSContext *cx, jsval v)
 
     JS_ASSERT(!JSVAL_IS_PRIMITIVE(v));
     obj = JSVAL_TO_OBJECT(v);
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
 
     if (clasp == &js_IteratorClass) {
         js_CloseNativeIterator(cx, obj);
@@ -539,7 +539,7 @@ CallEnumeratorNext(JSContext *cx, JSObject *iterobj, uintN flags, jsval *rval)
          */
         if (obj != obj2) {
             cond = JS_FALSE;
-            clasp = OBJ_GET_CLASS(cx, obj2);
+            clasp = obj2->getClass();
             if (clasp->flags & JSCLASS_IS_EXTENDED) {
                 xclasp = (JSExtendedClass *) clasp;
                 cond = xclasp->outerObject &&
@@ -582,7 +582,7 @@ js_CallIteratorNext(JSContext *cx, JSObject *iterobj, jsval *rval)
     uintN flags;
 
     /* Fast path for native iterators */
-    if (OBJ_GET_CLASS(cx, iterobj) == &js_IteratorClass) {
+    if (iterobj->getClass() == &js_IteratorClass) {
         flags = JSVAL_TO_INT(iterobj->getSlot(JSSLOT_ITER_FLAGS));
         if (flags & JSITER_ENUMERATE)
             return CallEnumeratorNext(cx, iterobj, flags, rval);
diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index be9e3b3ae065..06c1d9aba63e 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -182,7 +182,7 @@ obj_getSlot(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 
     pobj = JSVAL_TO_OBJECT(*vp);
     if (pobj) {
-        clasp = OBJ_GET_CLASS(cx, pobj);
+        clasp = pobj->getClass();
         if (clasp == &js_CallClass || clasp == &js_BlockClass) {
             /* Censor activations and lexical scopes per ECMA-262. */
             *vp = JSVAL_NULL;
@@ -1021,7 +1021,7 @@ obj_toString(JSContext *cx, uintN argc, jsval *vp)
     if (!obj)
         return JS_FALSE;
     obj = js_GetWrappedObject(cx, obj);
-    clazz = OBJ_GET_CLASS(cx, obj)->name;
+    clazz = obj->getClass()->name;
     nchars = 9 + strlen(clazz);         /* 9 for "[object ]" */
     chars = (jschar *) cx->malloc((nchars + 1) * sizeof(jschar));
     if (!chars)
@@ -1143,7 +1143,7 @@ js_CheckScopeChainValidity(JSContext *cx, JSObject *scopeobj, const char *caller
 
     /* XXX This is an awful gross hack. */
     while (scopeobj) {
-        clasp = OBJ_GET_CLASS(cx, scopeobj);
+        clasp = scopeobj->getClass();
         if (clasp->flags & JSCLASS_IS_EXTENDED) {
             xclasp = (JSExtendedClass*)clasp;
             if (xclasp->innerObject &&
@@ -2785,7 +2785,7 @@ InitScopeForObject(JSContext* cx, JSObject* obj, JSObject* proto, JSObjectOps* o
     JS_ASSERT(proto == obj->getProto());
 
     /* Share proto's emptyScope only if obj is similar to proto. */
-    JSClass *clasp = OBJ_GET_CLASS(cx, obj);
+    JSClass *clasp = obj->getClass();
     JSScope *scope = NULL;
 
     if (proto && proto->isNative()) {
@@ -3379,7 +3379,7 @@ js_PutBlockObject(JSContext *cx, JSBool normalUnwind)
 
     fp = cx->fp;
     obj = fp->scopeChain;
-    JS_ASSERT(OBJ_GET_CLASS(cx, obj) == &js_BlockClass);
+    JS_ASSERT(obj->getClass() == &js_BlockClass);
     JS_ASSERT(obj->getPrivate() == cx->fp);
     JS_ASSERT(OBJ_IS_CLONED_BLOCK(obj));
 
@@ -3703,7 +3703,7 @@ js_InitClass(JSContext *cx, JSObject *obj, JSObject *parent_proto,
          * and (c) key is not the null key.
          */
         if ((clasp->flags & JSCLASS_IS_ANONYMOUS) &&
-            (OBJ_GET_CLASS(cx, obj)->flags & JSCLASS_IS_GLOBAL) &&
+            (obj->getClass()->flags & JSCLASS_IS_GLOBAL) &&
             key != JSProto_Null) {
             named = JS_FALSE;
         } else {
@@ -3755,7 +3755,7 @@ js_InitClass(JSContext *cx, JSObject *obj, JSObject *parent_proto,
         }
 
         /* Bootstrap Function.prototype (see also JS_InitStandardClasses). */
-        if (OBJ_GET_CLASS(cx, ctor) == clasp)
+        if (ctor->getClass() == clasp)
             ctor->setProto(proto);
     }
 
@@ -3956,7 +3956,7 @@ js_GetClassObject(JSContext *cx, JSObject *obj, JSProtoKey key,
 
     while ((tmp = obj->getParent()) != NULL)
         obj = tmp;
-    if (!(OBJ_GET_CLASS(cx, obj)->flags & JSCLASS_IS_GLOBAL)) {
+    if (!(obj->getClass()->flags & JSCLASS_IS_GLOBAL)) {
         *objp = NULL;
         return JS_TRUE;
     }
@@ -4001,7 +4001,7 @@ JSBool
 js_SetClassObject(JSContext *cx, JSObject *obj, JSProtoKey key, JSObject *cobj)
 {
     JS_ASSERT(!obj->getParent());
-    if (!(OBJ_GET_CLASS(cx, obj)->flags & JSCLASS_IS_GLOBAL))
+    if (!(obj->getClass()->flags & JSCLASS_IS_GLOBAL))
         return JS_TRUE;
 
     return JS_SetReservedSlot(cx, obj, key, OBJECT_TO_JSVAL(cobj));
@@ -4138,7 +4138,7 @@ js_ConstructObject(JSContext *cx, JSClass *clasp, JSObject *proto,
      * we should throw a type error.
      */
     obj = JSVAL_TO_OBJECT(rval);
-    if (OBJ_GET_CLASS(cx, obj) != clasp ||
+    if (obj->getClass() != clasp ||
         (!(~clasp->flags & (JSCLASS_HAS_PRIVATE |
                             JSCLASS_CONSTRUCT_PROTOTYPE)) &&
          !obj->getPrivate())) {
@@ -4710,7 +4710,7 @@ js_LookupPropertyWithFlags(JSContext *cx, JSObject *obj, jsid id, uintN flags,
          * that is really just a memory-saving hack, safe because Blocks cannot
          * be on the prototype chain of other objects.
          */
-        JS_ASSERT_IF(OBJ_GET_CLASS(cx, obj) != &js_BlockClass,
+        JS_ASSERT_IF(obj->getClass() != &js_BlockClass,
                      OBJ_SCOPE(obj) != OBJ_SCOPE(proto));
 
         obj = proto;
@@ -4752,9 +4752,9 @@ js_FindPropertyHelper(JSContext *cx, jsid id, JSBool cacheResult,
         if (prop) {
 #ifdef DEBUG
             if (parent) {
-                JSClass *clasp = OBJ_GET_CLASS(cx, obj);
+                JSClass *clasp = obj->getClass();
                 JS_ASSERT(pobj->isNative());
-                JS_ASSERT(OBJ_GET_CLASS(cx, pobj) == clasp);
+                JS_ASSERT(pobj->getClass() == clasp);
                 if (clasp == &js_BlockClass) {
                     /*
                      * A block instance on the scope chain is immutable and
@@ -4854,7 +4854,7 @@ js_FindIdentifierBase(JSContext *cx, JSObject *scopeChain, jsid id)
         if (prop) {
             JS_ASSERT(pobj->isNative());
             JS_ASSERT(!obj->getParent() ||
-                      OBJ_GET_CLASS(cx, pobj) == OBJ_GET_CLASS(cx, obj));
+                      pobj->getClass() == obj->getClass());
 #ifdef DEBUG
             PropertyCacheEntry *entry =
 #endif
@@ -5028,7 +5028,7 @@ js_GetPropertyHelper(JSContext *cx, JSObject *obj, jsid id, uintN getHow,
     if (!prop) {
         *vp = JSVAL_VOID;
 
-        if (!OBJ_GET_CLASS(cx, obj)->getProperty(cx, obj, ID_TO_VALUE(id), vp))
+        if (!obj->getClass()->getProperty(cx, obj, ID_TO_VALUE(id), vp))
             return JS_FALSE;
 
         PCMETER(getHow & JSGET_CACHE_RESULT && JS_PROPERTY_CACHE(cx).nofills++);
@@ -5206,7 +5206,7 @@ js_SetPropertyHelper(JSContext *cx, JSObject *obj, jsid id, uintN defineHow,
         }
     } else {
         /* We should never add properties to lexical blocks.  */
-        JS_ASSERT(OBJ_GET_CLASS(cx, obj) != &js_BlockClass);
+        JS_ASSERT(obj->getClass() != &js_BlockClass);
 
         if (!obj->getParent() && !js_CheckUndeclaredVarAssignment(cx))
             return JS_FALSE;
@@ -5224,7 +5224,7 @@ js_SetPropertyHelper(JSContext *cx, JSObject *obj, jsid id, uintN defineHow,
     attrs = JSPROP_ENUMERATE;
     flags = 0;
     shortid = 0;
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
     getter = clasp->getProperty;
     setter = clasp->setProperty;
 
@@ -5501,8 +5501,7 @@ js_DeleteProperty(JSContext *cx, JSObject *obj, jsid id, jsval *rval)
          * a prototype, call the class's delProperty hook, passing rval as the
          * result parameter.
          */
-        return OBJ_GET_CLASS(cx, obj)->delProperty(cx, obj, ID_TO_VALUE(id),
-                                                   rval);
+        return obj->getClass()->delProperty(cx, obj, ID_TO_VALUE(id), rval);
     }
 
     sprop = (JSScopeProperty *)prop;
@@ -5541,7 +5540,7 @@ js_DefaultValue(JSContext *cx, JSObject *obj, JSType hint, jsval *vp)
          * new String(...) instances whether mutated to have their own scope or
          * not, as well as direct String.prototype references.
          */
-        if (OBJ_GET_CLASS(cx, obj) == &js_StringClass) {
+        if (obj->getClass() == &js_StringClass) {
             jsid toStringId = ATOM_TO_JSID(cx->runtime->atomState.toStringAtom);
 
             JS_LOCK_OBJ(cx, obj);
@@ -5552,7 +5551,7 @@ js_DefaultValue(JSContext *cx, JSObject *obj, JSType hint, jsval *vp)
             if (!sprop) {
                 pobj = obj->getProto();
 
-                if (pobj && OBJ_GET_CLASS(cx, pobj) == &js_StringClass) {
+                if (pobj && pobj->getClass() == &js_StringClass) {
                     JS_UNLOCK_SCOPE(cx, scope);
                     JS_LOCK_OBJ(cx, pobj);
                     scope = OBJ_SCOPE(pobj);
@@ -5587,13 +5586,13 @@ js_DefaultValue(JSContext *cx, JSObject *obj, JSType hint, jsval *vp)
         }
 
         if (!JSVAL_IS_PRIMITIVE(v)) {
-            if (!OBJ_GET_CLASS(cx, obj)->convert(cx, obj, hint, &v))
+            if (!obj->getClass()->convert(cx, obj, hint, &v))
                 return JS_FALSE;
         }
         break;
 
       default:
-        if (!OBJ_GET_CLASS(cx, obj)->convert(cx, obj, hint, &v))
+        if (!obj->getClass()->convert(cx, obj, hint, &v))
             return JS_FALSE;
         if (!JSVAL_IS_PRIMITIVE(v)) {
             JSType type = JS_TypeOfValue(cx, v);
@@ -5611,7 +5610,7 @@ js_DefaultValue(JSContext *cx, JSObject *obj, JSType hint, jsval *vp)
     if (!JSVAL_IS_PRIMITIVE(v)) {
         /* Avoid recursive death when decompiling in js_ReportValueError. */
         if (hint == JSTYPE_STRING) {
-            str = JS_InternString(cx, OBJ_GET_CLASS(cx, obj)->name);
+            str = JS_InternString(cx, obj->getClass()->name);
             if (!str)
                 return JS_FALSE;
         } else {
@@ -5962,7 +5961,7 @@ js_CheckAccess(JSContext *cx, JSObject *obj, jsid id, JSAccessMode mode,
      * checkObjectAccess hook.  This covers precompilation-based sharing and
      * (possibly unintended) runtime sharing across trust boundaries.
      */
-    clasp = OBJ_GET_CLASS(cx, pobj);
+    clasp = pobj->getClass();
     check = clasp->checkAccess;
     if (!check) {
         callbacks = JS_GetSecurityCallbacks(cx);
@@ -6043,7 +6042,7 @@ js_Call(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
 {
     JSClass *clasp;
 
-    clasp = OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(argv[-2]));
+    clasp = JSVAL_TO_OBJECT(argv[-2])->getClass();
     if (!clasp->call) {
 #ifdef NARCISSUS
         JSObject *callee, *args;
@@ -6082,7 +6081,7 @@ js_Construct(JSContext *cx, JSObject *obj, uintN argc, jsval *argv,
 {
     JSClass *clasp;
 
-    clasp = OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(argv[-2]));
+    clasp = JSVAL_TO_OBJECT(argv[-2])->getClass();
     if (!clasp->construct) {
 #ifdef NARCISSUS
         JSObject *callee, *args;
@@ -6121,7 +6120,7 @@ js_HasInstance(JSContext *cx, JSObject *obj, jsval v, JSBool *bp)
 {
     JSClass *clasp;
 
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
     if (clasp->hasInstance)
         return clasp->hasInstance(cx, obj, v, bp);
 #ifdef NARCISSUS
@@ -6409,7 +6408,7 @@ js_XDRObject(JSXDRState *xdr, JSObject **objp)
     cx = xdr->cx;
     atom = NULL;
     if (xdr->mode == JSXDR_ENCODE) {
-        clasp = OBJ_GET_CLASS(cx, *objp);
+        clasp = (*objp)->getClass();
         classId = JS_XDRFindClassIdByName(xdr, clasp->name);
         classDef = !classId;
         if (classDef) {
@@ -6451,7 +6450,7 @@ js_XDRObject(JSXDRState *xdr, JSObject **objp)
             protoKey = (JSProtoKey) (classDef >> 1);
             if (!js_GetClassPrototype(cx, NULL, protoKey, &proto, clasp))
                 return JS_FALSE;
-            clasp = OBJ_GET_CLASS(cx, proto);
+            clasp = proto->getClass();
             if (!JS_XDRRegisterClass(xdr, clasp, &classId))
                 return JS_FALSE;
         } else {
@@ -6693,7 +6692,7 @@ js_SetReservedSlot(JSContext *cx, JSObject *obj, uint32 index, jsval v)
     if (!obj->isNative())
         return true;
 
-    JSClass *clasp = OBJ_GET_CLASS(cx, obj);
+    JSClass *clasp = obj->getClass();
     uint32 limit = JSCLASS_RESERVED_SLOTS(clasp);
 
     JS_LOCK_OBJ(cx, obj);
@@ -6740,7 +6739,7 @@ js_GetWrappedObject(JSContext *cx, JSObject *obj)
 {
     JSClass *clasp;
 
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
     if (clasp->flags & JSCLASS_IS_EXTENDED) {
         JSExtendedClass *xclasp;
         JSObject *obj2;
diff --git a/js/src/jsobj.h b/js/src/jsobj.h
index 48794691bd0d..66251bf85d8c 100644
--- a/js/src/jsobj.h
+++ b/js/src/jsobj.h
@@ -558,17 +558,11 @@ struct JSObject {
 
 #endif /* JS_THREADSAFE */
 
-/*
- * Class is invariant and comes from the fixed clasp member. Thus no locking
- * is necessary to read it. Same for the private slot.
- */
-#define OBJ_GET_CLASS(cx,obj)           (obj)->getClass()
-
 #ifdef __cplusplus
 inline void
 OBJ_TO_INNER_OBJECT(JSContext *cx, JSObject *&obj)
 {
-    JSClass *clasp = OBJ_GET_CLASS(cx, obj);
+    JSClass *clasp = obj->getClass();
     if (clasp->flags & JSCLASS_IS_EXTENDED) {
         JSExtendedClass *xclasp = (JSExtendedClass *) clasp;
         if (xclasp->innerObject)
@@ -583,7 +577,7 @@ OBJ_TO_INNER_OBJECT(JSContext *cx, JSObject *&obj)
 inline void
 OBJ_TO_OUTER_OBJECT(JSContext *cx, JSObject *&obj)
 {
-    JSClass *clasp = OBJ_GET_CLASS(cx, obj);
+    JSClass *clasp = obj->getClass();
     if (clasp->flags & JSCLASS_IS_EXTENDED) {
         JSExtendedClass *xclasp = (JSExtendedClass *) clasp;
         if (xclasp->outerObject)
diff --git a/js/src/json.cpp b/js/src/json.cpp
index cca3920cb7f7..cfd9dbab8ead 100644
--- a/js/src/json.cpp
+++ b/js/src/json.cpp
@@ -449,7 +449,7 @@ Str(JSContext *cx, jsid id, JSObject *holder, StringifyContext *scx, jsval *vp,
 
     // catches string and number objects with no toJSON
     if (!JSVAL_IS_PRIMITIVE(*vp)) {
-        JSClass *clasp = OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(*vp));
+        JSClass *clasp = JSVAL_TO_OBJECT(*vp)->getClass();
         if (clasp == &js_StringClass || clasp == &js_NumberClass)
             *vp = JSVAL_TO_OBJECT(*vp)->fslots[JSSLOT_PRIMITIVE_THIS];
     }
@@ -515,7 +515,7 @@ InitializeGap(JSContext *cx, jsval space, JSCharBuffer &cb)
 
     if (!JSVAL_IS_PRIMITIVE(space)) {
         JSObject *obj = JSVAL_TO_OBJECT(space);
-        JSClass *clasp = OBJ_GET_CLASS(cx, obj);
+        JSClass *clasp = obj->getClass();
         if (clasp == &js_NumberClass || clasp == &js_StringClass)
             *gap.addr() = obj->fslots[JSSLOT_PRIMITIVE_THIS];
     }
diff --git a/js/src/jsopcode.cpp b/js/src/jsopcode.cpp
index 638372c186ac..52c0f6632ddb 100644
--- a/js/src/jsopcode.cpp
+++ b/js/src/jsopcode.cpp
@@ -275,7 +275,7 @@ ToDisassemblySource(JSContext *cx, jsval v)
 {
     if (!JSVAL_IS_PRIMITIVE(v)) {
         JSObject *obj = JSVAL_TO_OBJECT(v);
-        JSClass *clasp = OBJ_GET_CLASS(cx, obj);
+        JSClass *clasp = obj->getClass();
 
         if (clasp == &js_BlockClass) {
             char *source = JS_sprintf_append(NULL, "depth %d {", OBJ_BLOCK_DEPTH(cx, obj));
@@ -1315,7 +1315,7 @@ GetLocal(SprintStack *ss, jsint i)
         if (j == n)
             return GetStr(ss, i);
         obj = script->getObject(j);
-        if (OBJ_GET_CLASS(cx, obj) == &js_BlockClass) {
+        if (obj->getClass() == &js_BlockClass) {
             depth = OBJ_BLOCK_DEPTH(cx, obj);
             count = OBJ_BLOCK_COUNT(cx, obj);
             if ((jsuint)(i - depth) < (jsuint)count)
@@ -4190,7 +4190,7 @@ Decompile(SprintStack *ss, jsbytecode *pc, intN nb, JSOp nextop)
 
               case JSOP_OBJECT:
                 LOAD_OBJECT(0);
-                LOCAL_ASSERT(OBJ_GET_CLASS(cx, obj) == &js_RegExpClass);
+                LOCAL_ASSERT(obj->getClass() == &js_RegExpClass);
                 goto do_regexp;
 
               case JSOP_REGEXP:
diff --git a/js/src/jsops.cpp b/js/src/jsops.cpp
index da5d22c6f5b5..a56c6e0d1c4b 100644
--- a/js/src/jsops.cpp
+++ b/js/src/jsops.cpp
@@ -145,7 +145,7 @@ BEGIN_CASE(JSOP_POPN)
                  OBJ_BLOCK_DEPTH(cx, obj) + OBJ_BLOCK_COUNT(cx, obj)
                  <= (size_t) (regs.sp - StackBase(fp)));
     for (obj = fp->scopeChain; obj; obj = obj->getParent()) {
-        clasp = OBJ_GET_CLASS(cx, obj);
+        clasp = obj->getClass();
         if (clasp != &js_BlockClass && clasp != &js_WithClass)
             continue;
         if (obj->getPrivate() != fp)
@@ -799,7 +799,7 @@ END_CASE(JSOP_BITAND)
 #define EXTENDED_EQUALITY_OP(OP)                                              \
     if (ltmp == JSVAL_OBJECT &&                                               \
         (obj2 = JSVAL_TO_OBJECT(lval)) &&                                     \
-        ((clasp = OBJ_GET_CLASS(cx, obj2))->flags & JSCLASS_IS_EXTENDED)) {   \
+        ((clasp = obj2->getClass())->flags & JSCLASS_IS_EXTENDED)) {          \
         JSExtendedClass *xclasp;                                              \
                                                                               \
         xclasp = (JSExtendedClass *) clasp;                                   \
@@ -1765,7 +1765,7 @@ BEGIN_CASE(JSOP_SETMETHOD)
                  * slots that may vary with obj.
                  */
                 if (slot < obj->numSlots() &&
-                    !OBJ_GET_CLASS(cx, obj)->reserveSlots) {
+                    !obj->getClass()->reserveSlots) {
                     ++scope->freeslot;
                 } else {
                     if (!js_AllocSlot(cx, obj, &slot))
@@ -2980,7 +2980,7 @@ BEGIN_CASE(JSOP_DEFFUN)
     JS_ASSERT_IF(doSet, fp->flags & JSFRAME_EVAL);
     if (prop) {
         if (parent == pobj &&
-            OBJ_GET_CLASS(cx, parent) == &js_CallClass &&
+            parent->getClass() == &js_CallClass &&
             (old = ((JSScopeProperty *) prop)->attributes(),
              !(old & (JSPROP_GETTER|JSPROP_SETTER)) &&
              (old & (JSPROP_ENUMERATE|JSPROP_PERMANENT)) == attrs)) {
@@ -3143,14 +3143,14 @@ BEGIN_CASE(JSOP_LAMBDA)
                     lval = FETCH_OPND(-1);
                     if (JSVAL_IS_OBJECT(lval) &&
                         (obj2 = JSVAL_TO_OBJECT(lval)) &&
-                        OBJ_GET_CLASS(cx, obj2) == &js_ObjectClass) {
+                        obj2->getClass() == &js_ObjectClass) {
                         break;
                     }
                 } else if (op == JSOP_INITMETHOD) {
                     lval = FETCH_OPND(-1);
                     JS_ASSERT(!JSVAL_IS_PRIMITIVE(lval));
                     obj2 = JSVAL_TO_OBJECT(lval);
-                    JS_ASSERT(OBJ_GET_CLASS(cx, obj2) == &js_ObjectClass);
+                    JS_ASSERT(obj2->getClass() == &js_ObjectClass);
                     JS_ASSERT(OBJ_SCOPE(obj2)->object == obj2);
                     break;
                 }
@@ -3361,7 +3361,7 @@ BEGIN_CASE(JSOP_INITMETHOD)
     lval = FETCH_OPND(-2);
     obj = JSVAL_TO_OBJECT(lval);
     JS_ASSERT(obj->isNative());
-    JS_ASSERT(!OBJ_GET_CLASS(cx, obj)->reserveSlots);
+    JS_ASSERT(!obj->getClass()->reserveSlots);
     JS_ASSERT(!(obj->getClass()->flags & JSCLASS_SHARE_ALL_PROPERTIES));
 
     JSScope *scope = OBJ_SCOPE(obj);
@@ -3987,7 +3987,7 @@ BEGIN_CASE(JSOP_LEAVEBLOCKEXPR)
 BEGIN_CASE(JSOP_LEAVEBLOCK)
 {
 #ifdef DEBUG
-    JS_ASSERT(OBJ_GET_CLASS(cx, fp->blockChain) == &js_BlockClass);
+    JS_ASSERT(fp->blockChain->getClass() == &js_BlockClass);
     uintN blockDepth = OBJ_BLOCK_DEPTH(cx, fp->blockChain);
 
     JS_ASSERT(blockDepth <= StackDepth(script));
@@ -3999,7 +3999,7 @@ BEGIN_CASE(JSOP_LEAVEBLOCK)
      */
     obj = fp->scopeChain;
     if (obj->getProto() == fp->blockChain) {
-        JS_ASSERT (OBJ_GET_CLASS(cx, obj) == &js_BlockClass);
+        JS_ASSERT(obj->getClass() == &js_BlockClass);
         if (!js_PutBlockObject(cx, JS_TRUE))
             goto error;
     }
diff --git a/js/src/jsregexp.cpp b/js/src/jsregexp.cpp
index 321f932aac9e..bb82ad1923c0 100644
--- a/js/src/jsregexp.cpp
+++ b/js/src/jsregexp.cpp
@@ -5108,7 +5108,7 @@ regexp_getProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
 
     if (!JSVAL_IS_INT(id))
         return JS_TRUE;
-    while (OBJ_GET_CLASS(cx, obj) != &js_RegExpClass) {
+    while (obj->getClass() != &js_RegExpClass) {
         obj = obj->getProto();
         if (!obj)
             return JS_TRUE;
@@ -5154,7 +5154,7 @@ regexp_setProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
     ok = JS_TRUE;
     if (!JSVAL_IS_INT(id))
         return ok;
-    while (OBJ_GET_CLASS(cx, obj) != &js_RegExpClass) {
+    while (obj->getClass() != &js_RegExpClass) {
         obj = obj->getProto();
         if (!obj)
             return JS_TRUE;
@@ -5569,7 +5569,7 @@ regexp_compile_sub(JSContext *cx, JSObject *obj, uintN argc, jsval *argv,
              * from the original RegExp also).
              */
             obj2 = JSVAL_TO_OBJECT(argv[0]);
-            if (obj2 && OBJ_GET_CLASS(cx, obj2) == &js_RegExpClass) {
+            if (obj2 && obj2->getClass() == &js_RegExpClass) {
                 if (argc >= 2 && !JSVAL_IS_VOID(argv[1])) { /* 'flags' passed */
                     JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                                          JSMSG_NEWREGEXP_FLAGGED);
@@ -5780,7 +5780,7 @@ RegExp(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
          */
         if ((argc < 2 || JSVAL_IS_VOID(argv[1])) &&
             !JSVAL_IS_PRIMITIVE(argv[0]) &&
-            OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(argv[0])) == &js_RegExpClass) {
+            JSVAL_TO_OBJECT(argv[0])->getClass() == &js_RegExpClass) {
             *rval = argv[0];
             return JS_TRUE;
         }
diff --git a/js/src/jsstr.cpp b/js/src/jsstr.cpp
index 67c64858f67d..9bac8ab8abcd 100644
--- a/js/src/jsstr.cpp
+++ b/js/src/jsstr.cpp
@@ -552,7 +552,7 @@ str_getProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
     JSString *str;
 
     if (id == ATOM_KEY(cx->runtime->atomState.lengthAtom)) {
-        if (OBJ_GET_CLASS(cx, obj) == &js_StringClass) {
+        if (obj->getClass() == &js_StringClass) {
             /* Follow ECMA-262 by fetching intrinsic length of our string. */
             v = obj->fslots[JSSLOT_PRIMITIVE_THIS];
             JS_ASSERT(JSVAL_IS_STRING(v));
diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index 0d4023c76259..aaa3c1304470 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -3120,7 +3120,7 @@ template<typename T>
 inline uint32
 GetFromClosure(JSContext* cx, JSObject* call, const ClosureVarInfo* cv, double* result)
 {
-    JS_ASSERT(OBJ_GET_CLASS(cx, call) == &js_CallClass);
+    JS_ASSERT(call->getClass() == &js_CallClass);
 
     InterpState* state = cx->interpState;
 
@@ -6435,7 +6435,7 @@ ScopeChainCheck(JSContext* cx, TreeFragment* f)
     }
     JS_ASSERT(child == f->globalObj);
 
-    if (!(OBJ_GET_CLASS(cx, f->globalObj)->flags & JSCLASS_IS_GLOBAL)) {
+    if (!(f->globalObj->getClass()->flags & JSCLASS_IS_GLOBAL)) {
         debug_only_print0(LC_TMTracer, "Blacklist: non-global at root of scope chain.\n");
         Blacklist((jsbytecode*) f->root->ip);
         return false;
@@ -7879,7 +7879,7 @@ TraceRecorder::scopeChainProp(JSObject* chainHead, jsval*& vp, LIns*& ins, NameR
         return ARECORD_CONTINUE;
     }
 
-    if (obj == obj2 && OBJ_GET_CLASS(cx, obj) == &js_CallClass) {
+    if (obj == obj2 && obj->getClass() == &js_CallClass) {
         AbortableRecordingStatus status =
             InjectStatus(callProp(obj, prop, ATOM_TO_JSID(atom), vp, ins, nr));
         obj->dropProperty(cx, prop);
@@ -8670,7 +8670,7 @@ TraceRecorder::equalityHelper(jsval l, jsval r, LIns* l_ins, LIns* r_ins,
             if (JSVAL_IS_NULL(l))
                 op = LIR_peq;
         } else if (JSVAL_IS_OBJECT(l)) {
-            JSClass *clasp = OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(l));
+            JSClass *clasp = JSVAL_TO_OBJECT(l)->getClass();
             if ((clasp->flags & JSCLASS_IS_EXTENDED) && ((JSExtendedClass*) clasp)->equality)
                 RETURN_STOP_A("Can't trace extended class equality operator");
             op = LIR_peq;
@@ -11097,7 +11097,7 @@ TraceRecorder::incName(jsint incr, bool pre)
         return ARECORD_CONTINUE;
     }
 
-    if (OBJ_GET_CLASS(cx, nr.obj) != &js_CallClass)
+    if (nr.obj->getClass() != &js_CallClass)
         RETURN_STOP_A("incName on unsupported object class");
 
     CHECK_STATUS_A(setCallProp(nr.obj, nr.obj_ins, nr.sprop, v_after, v));
@@ -11251,7 +11251,7 @@ TraceRecorder::setProp(jsval &l, PropertyCacheEntry* entry, JSScopeProperty* spr
 
     // Fast path for CallClass. This is about 20% faster than the general case.
     v_ins = get(&v);
-    if (OBJ_GET_CLASS(cx, obj) == &js_CallClass)
+    if (obj->getClass() == &js_CallClass)
         return setCallProp(obj, obj_ins, sprop, v_ins, v);
 
     // Find obj2. If entry->adding(), the TAG bits are all 0.
@@ -12825,11 +12825,11 @@ TraceRecorder::prop(JSObject* obj, LIns* obj_ins, uint32 *slotp, LIns** v_insp,
          * We could specialize to guard on just JSClass.getProperty, but a mere
          * class guard is simpler and slightly faster.
          */
-        if (OBJ_GET_CLASS(cx, obj)->getProperty != JS_PropertyStub) {
+        if (obj->getClass()->getProperty != JS_PropertyStub) {
             RETURN_STOP_A("can't trace through access to undefined property if "
                           "JSClass.getProperty hook isn't stubbed");
         }
-        guardClass(obj, obj_ins, OBJ_GET_CLASS(cx, obj), snapshot(MISMATCH_EXIT), ACC_OTHER);
+        guardClass(obj, obj_ins, obj->getClass(), snapshot(MISMATCH_EXIT), ACC_OTHER);
 
         /*
          * This trace will be valid as long as neither the object nor any object
@@ -13971,7 +13971,7 @@ TraceRecorder::record_JSOP_LAMBDA()
             jsval lval = stackval(-1);
 
             if (!JSVAL_IS_PRIMITIVE(lval) &&
-                OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(lval)) == &js_ObjectClass) {
+                JSVAL_TO_OBJECT(lval)->getClass() == &js_ObjectClass) {
                 stack(0, INS_CONSTOBJ(FUN_OBJECT(fun)));
                 return ARECORD_CONTINUE;
             }
diff --git a/js/src/jsxml.cpp b/js/src/jsxml.cpp
index 4bd4107ae892..ce3e6b994d4a 100644
--- a/js/src/jsxml.cpp
+++ b/js/src/jsxml.cpp
@@ -255,7 +255,7 @@ namespace_equality(JSContext *cx, JSObject *obj, jsval v, JSBool *bp)
 
     JS_ASSERT(JSVAL_IS_OBJECT(v));
     obj2 = JSVAL_TO_OBJECT(v);
-    *bp = (!obj2 || OBJ_GET_CLASS(cx, obj2) != &js_NamespaceClass.base)
+    *bp = (!obj2 || obj2->getClass() != &js_NamespaceClass.base)
           ? JS_FALSE
           : js_EqualStrings(GetURI(obj), GetURI(obj2));
     return JS_TRUE;
@@ -379,7 +379,7 @@ qname_equality(JSContext *cx, JSObject *qn, jsval v, JSBool *bp)
 
     JS_ASSERT(JSVAL_IS_OBJECT(v));
     obj2 = JSVAL_TO_OBJECT(v);
-    *bp = (!obj2 || OBJ_GET_CLASS(cx, obj2) != &js_QNameClass.base)
+    *bp = (!obj2 || obj2->getClass() != &js_QNameClass.base)
           ? JS_FALSE
           : qname_identity(qn, obj2);
     return JS_TRUE;
@@ -447,7 +447,7 @@ qname_toString(JSContext *cx, uintN argc, jsval *vp)
     obj = JS_THIS_OBJECT(cx, vp);
     if (!obj)
         return JS_FALSE;
-    clasp = OBJ_GET_CLASS(cx, obj);
+    clasp = obj->getClass();
     if (clasp != &js_AttributeNameClass &&
         clasp != &js_AnyNameClass &&
         !JS_InstanceOf(cx, obj, &js_QNameClass.base, vp + 2)) {
@@ -537,7 +537,7 @@ js_ConstructXMLQNameObject(JSContext *cx, jsval nsval, jsval lnval)
      * production, step 2.
      */
     if (!JSVAL_IS_PRIMITIVE(nsval) &&
-        OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(nsval)) == &js_AnyNameClass) {
+        JSVAL_TO_OBJECT(nsval)->getClass() == &js_AnyNameClass) {
         nsval = JSVAL_NULL;
     }
 
@@ -577,7 +577,7 @@ js_IsXMLName(JSContext *cx, jsval v)
      * See ECMA-357 13.1.2.1 step 1 and 13.3.2.
      */
     if (!JSVAL_IS_PRIMITIVE(v) &&
-        IsQNameClass(OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(v)))) {
+        IsQNameClass(JSVAL_TO_OBJECT(v)->getClass())) {
         name = GetLocalName(JSVAL_TO_OBJECT(v));
     } else {
         older = JS_SetErrorReporter(cx, NULL);
@@ -616,7 +616,7 @@ NamespaceHelper(JSContext *cx, JSObject *obj, intN argc, jsval *argv,
         urival = argv[argc > 1];
         if (!JSVAL_IS_PRIMITIVE(urival)) {
             uriobj = JSVAL_TO_OBJECT(urival);
-            clasp = OBJ_GET_CLASS(cx, uriobj);
+            clasp = uriobj->getClass();
             isNamespace = (clasp == &js_NamespaceClass.base);
             isQName = (clasp == &js_QNameClass.base);
         }
@@ -722,7 +722,7 @@ QNameHelper(JSContext *cx, JSObject *obj, JSClass *clasp, intN argc,
         nameval = argv[argc > 1];
         isQName =
             !JSVAL_IS_PRIMITIVE(nameval) &&
-            OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(nameval)) == &js_QNameClass.base;
+            JSVAL_TO_OBJECT(nameval)->getClass() == &js_QNameClass.base;
     }
 
     if (!obj) {
@@ -777,7 +777,7 @@ QNameHelper(JSContext *cx, JSObject *obj, JSClass *clasp, intN argc,
         if (!js_GetDefaultXMLNamespace(cx, &nsval))
             return JS_FALSE;
         JS_ASSERT(!JSVAL_IS_PRIMITIVE(nsval));
-        JS_ASSERT(OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(nsval)) ==
+        JS_ASSERT(JSVAL_TO_OBJECT(nsval)->getClass() ==
                   &js_NamespaceClass.base);
     }
 
@@ -795,7 +795,7 @@ QNameHelper(JSContext *cx, JSObject *obj, JSClass *clasp, intN argc,
         isNamespace = isQName = JS_FALSE;
         if (!JSVAL_IS_PRIMITIVE(nsval)) {
             obj2 = JSVAL_TO_OBJECT(nsval);
-            clasp = OBJ_GET_CLASS(cx, obj2);
+            clasp = obj2->getClass();
             isNamespace = (clasp == &js_NamespaceClass.base);
             isQName = (clasp == &js_QNameClass.base);
         }
@@ -1926,7 +1926,7 @@ ToXML(JSContext *cx, jsval v)
             return obj;
         }
 
-        clasp = OBJ_GET_CLASS(cx, obj);
+        clasp = obj->getClass();
         if (clasp->flags & JSCLASS_DOCUMENT_OBSERVER) {
             JS_ASSERT(0);
         }
@@ -2007,7 +2007,7 @@ ToXMLList(JSContext *cx, jsval v)
             return obj;
         }
 
-        clasp = OBJ_GET_CLASS(cx, obj);
+        clasp = obj->getClass();
         if (clasp->flags & JSCLASS_DOCUMENT_OBSERVER) {
             JS_ASSERT(0);
         }
@@ -2854,7 +2854,7 @@ ToAttributeName(JSContext *cx, jsval v)
         }
 
         obj = JSVAL_TO_OBJECT(v);
-        clasp = OBJ_GET_CLASS(cx, obj);
+        clasp = obj->getClass();
         if (clasp == &js_AttributeNameClass)
             return obj;
 
@@ -2907,7 +2907,7 @@ IsFunctionQName(JSContext *cx, JSObject *qn, jsid *funidp)
 JSBool
 js_IsFunctionQName(JSContext *cx, JSObject *obj, jsid *funidp)
 {
-    if (OBJ_GET_CLASS(cx, obj) == &js_QNameClass.base)
+    if (obj->getClass() == &js_QNameClass.base)
         return IsFunctionQName(cx, obj, funidp);
     *funidp = 0;
     return JS_TRUE;
@@ -2930,7 +2930,7 @@ ToXMLName(JSContext *cx, jsval v, jsid *funidp)
         }
 
         obj = JSVAL_TO_OBJECT(v);
-        clasp = OBJ_GET_CLASS(cx, obj);
+        clasp = obj->getClass();
         if (clasp == &js_AttributeNameClass || clasp == &js_QNameClass.base)
             goto out;
         if (clasp == &js_AnyNameClass) {
@@ -3286,7 +3286,7 @@ DescendantsHelper(JSContext *cx, JSXML *xml, JSObject *nameqn, JSXML *list)
     JS_CHECK_RECURSION(cx, return JS_FALSE);
 
     if (xml->xml_class == JSXML_CLASS_ELEMENT &&
-        OBJ_GET_CLASS(cx, nameqn) == &js_AttributeNameClass) {
+        nameqn->getClass() == &js_AttributeNameClass) {
         for (i = 0, n = xml->xml_attrs.length; i < n; i++) {
             attr = XMLARRAY_MEMBER(&xml->xml_attrs, i, JSXML);
             if (attr && MatchAttrName(nameqn, attr)) {
@@ -3300,7 +3300,7 @@ DescendantsHelper(JSContext *cx, JSXML *xml, JSObject *nameqn, JSXML *list)
         kid = XMLARRAY_MEMBER(&xml->xml_kids, i, JSXML);
         if (!kid)
             continue;
-        if (OBJ_GET_CLASS(cx, nameqn) != &js_AttributeNameClass &&
+        if (nameqn->getClass() != &js_AttributeNameClass &&
             MatchElemName(nameqn, kid)) {
             if (!Append(cx, list, kid))
                 return JS_FALSE;
@@ -3763,7 +3763,7 @@ GetNamedProperty(JSContext *cx, JSXML *xml, JSObject* nameqn, JSXML *list)
             }
         }
     } else if (xml->xml_class == JSXML_CLASS_ELEMENT) {
-        attrs = (OBJ_GET_CLASS(cx, nameqn) == &js_AttributeNameClass);
+        attrs = (nameqn->getClass() == &js_AttributeNameClass);
         if (attrs) {
             array = &xml->xml_attrs;
             matcher = MatchAttrName;
@@ -4011,7 +4011,7 @@ PutProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
                     goto bad;
             } else {
                 nameobj = targetprop;
-                if (OBJ_GET_CLASS(cx, nameobj) == &js_AttributeNameClass) {
+                if (nameobj->getClass() == &js_AttributeNameClass) {
                     /*
                      * 2(c)(iii)(1-3).
                      * Note that rxml can't be null here, because target
@@ -4107,7 +4107,7 @@ PutProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
         parent = kid->parent;
         if (kid->xml_class == JSXML_CLASS_ATTRIBUTE) {
             nameobj = kid->name;
-            if (OBJ_GET_CLASS(cx, nameobj) != &js_AttributeNameClass) {
+            if (nameobj->getClass() != &js_AttributeNameClass) {
                 nameobj = NewXMLQName(cx, GetURI(nameobj), GetPrefix(nameobj),
                                       GetLocalName(nameobj),
                                       &js_AttributeNameClass);
@@ -4315,7 +4315,7 @@ PutProperty(JSContext *cx, JSObject *obj, jsval id, jsval *vp)
         if (!ok)
             goto out;
 
-        if (OBJ_GET_CLASS(cx, nameobj) == &js_AttributeNameClass) {
+        if (nameobj->getClass() == &js_AttributeNameClass) {
             /* 7(a). */
             if (!js_IsXMLName(cx, OBJECT_TO_JSVAL(nameobj)))
                 goto out;
@@ -4566,7 +4566,7 @@ ResolveValue(JSContext *cx, JSXML *list, JSXML **result)
         return JS_TRUE;
     }
 
-    if (OBJ_GET_CLASS(cx, targetprop) == &js_AttributeNameClass) {
+    if (targetprop->getClass() == &js_AttributeNameClass) {
         *result = NULL;
         return JS_TRUE;
     }
@@ -4622,7 +4622,7 @@ HasNamedProperty(JSXML *xml, JSObject *nameqn)
     }
 
     if (xml->xml_class == JSXML_CLASS_ELEMENT) {
-        if (OBJ_GET_CLASS(cx, nameqn) == &js_AttributeNameClass) {
+        if (nameqn->getClass() == &js_AttributeNameClass) {
             array = &xml->xml_attrs;
             matcher = MatchAttrName;
         } else {
@@ -4661,7 +4661,7 @@ HasFunctionProperty(JSContext *cx, JSObject *obj, jsid funid, JSBool *found)
     JSProperty *prop;
     JSXML *xml;
 
-    JS_ASSERT(OBJ_GET_CLASS(cx, obj) == &js_XMLClass);
+    JS_ASSERT(obj->getClass() == &js_XMLClass);
 
     if (!js_LookupProperty(cx, obj, funid, &pobj, &prop))
         return false;
@@ -4902,8 +4902,7 @@ xml_deleteProperty(JSContext *cx, JSObject *obj, jsid id, jsval *rval)
             return js_DeleteProperty(cx, obj, funid, rval);
 
         DeleteNamedProperty(cx, xml, nameqn,
-                            OBJ_GET_CLASS(cx, nameqn) ==
-                            &js_AttributeNameClass);
+                            nameqn->getClass() == &js_AttributeNameClass);
     }
 
     /*
@@ -6521,7 +6520,7 @@ xml_setLocalName(JSContext *cx, uintN argc, jsval *vp)
     } else {
         name = vp[2];
         if (!JSVAL_IS_PRIMITIVE(name) &&
-            OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(name)) == &js_QNameClass.base) {
+            JSVAL_TO_OBJECT(name)->getClass() == &js_QNameClass.base) {
             nameqn = JSVAL_TO_OBJECT(name);
             namestr = GetLocalName(nameqn);
         } else {
@@ -6561,7 +6560,7 @@ xml_setName(JSContext *cx, uintN argc, jsval *vp)
     } else {
         name = vp[2];
         if (!JSVAL_IS_PRIMITIVE(name) &&
-            OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(name)) == &js_QNameClass.base &&
+            JSVAL_TO_OBJECT(name)->getClass() == &js_QNameClass.base &&
             !GetURI(nameqn = JSVAL_TO_OBJECT(name))) {
             name = vp[2] = nameqn->fslots[JSSLOT_LOCAL_NAME];
         }
@@ -7004,7 +7003,7 @@ XML(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
 
     if (cx->isConstructing() && !JSVAL_IS_PRIMITIVE(v)) {
         vobj = JSVAL_TO_OBJECT(v);
-        clasp = OBJ_GET_CLASS(cx, vobj);
+        clasp = vobj->getClass();
         if (clasp == &js_XMLClass ||
             (clasp->flags & JSCLASS_DOCUMENT_OBSERVER)) {
             /* No need to lock obj, it's newly constructed and thread local. */
@@ -7406,7 +7405,7 @@ js_GetDefaultXMLNamespace(JSContext *cx, jsval *vp)
 
     obj = NULL;
     for (tmp = fp->scopeChain; tmp; tmp = tmp->getParent()) {
-        JSClass *clasp = OBJ_GET_CLASS(cx, tmp);
+        JSClass *clasp = tmp->getClass();
         if (clasp == &js_BlockClass || clasp == &js_WithClass)
             continue;
         if (!tmp->getProperty(cx, JS_DEFAULT_XML_NAMESPACE_ID, &v))
@@ -7619,15 +7618,15 @@ js_FindXMLProperty(JSContext *cx, jsval nameval, JSObject **objp, jsid *idp)
 
     JS_ASSERT(!JSVAL_IS_PRIMITIVE(nameval));
     nameobj = JSVAL_TO_OBJECT(nameval);
-    if (OBJ_GET_CLASS(cx, nameobj) == &js_AnyNameClass) {
+    if (nameobj->getClass() == &js_AnyNameClass) {
         v = STRING_TO_JSVAL(ATOM_TO_STRING(cx->runtime->atomState.starAtom));
         nameobj = js_ConstructObject(cx, &js_QNameClass.base, NULL, NULL, 1,
                                      &v);
         if (!nameobj)
             return JS_FALSE;
     } else {
-        JS_ASSERT(OBJ_GET_CLASS(cx, nameobj) == &js_AttributeNameClass ||
-                  OBJ_GET_CLASS(cx, nameobj) == &js_QNameClass.base);
+        JS_ASSERT(nameobj->getClass() == &js_AttributeNameClass ||
+                  nameobj->getClass() == &js_QNameClass.base);
     }
 
     qn = nameobj;
@@ -7638,7 +7637,7 @@ js_FindXMLProperty(JSContext *cx, jsval nameval, JSObject **objp, jsid *idp)
     do {
         /* Skip any With object that can wrap XML. */
         target = obj;
-        while (OBJ_GET_CLASS(cx, target) == &js_WithClass) {
+        while (target->getClass() == &js_WithClass) {
              proto = target->getProto();
              if (!proto)
                  break;
@@ -7722,7 +7721,7 @@ GetPrivate(JSContext *cx, JSObject *obj, const char *method)
     if (!xml) {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL,
                              JSMSG_INCOMPATIBLE_METHOD,
-                             js_XML_str, method, OBJ_GET_CLASS(cx, obj)->name);
+                             js_XML_str, method, obj->getClass()->name);
     }
     return xml;
 }
@@ -7872,8 +7871,7 @@ js_StepXMLListFilter(JSContext *cx, JSBool initialized)
     } else {
         /* We have iterated at least once. */
         JS_ASSERT(!JSVAL_IS_PRIMITIVE(sp[-2]));
-        JS_ASSERT(OBJ_GET_CLASS(cx, JSVAL_TO_OBJECT(sp[-2])) ==
-                                &js_XMLFilterClass);
+        JS_ASSERT(JSVAL_TO_OBJECT(sp[-2])->getClass() == &js_XMLFilterClass);
         filter = (JSXMLFilter *) JSVAL_TO_OBJECT(sp[-2])->getPrivate();
         JS_ASSERT(filter->kid);
 
diff --git a/js/src/xpconnect/src/nsXPConnect.cpp b/js/src/xpconnect/src/nsXPConnect.cpp
index f8f14e652c77..ad1977f12d6c 100644
--- a/js/src/xpconnect/src/nsXPConnect.cpp
+++ b/js/src/xpconnect/src/nsXPConnect.cpp
@@ -727,7 +727,7 @@ nsXPConnect::Traverse(void *p, nsCycleCollectionTraversalCallback &cb)
     if(traceKind == JSTRACE_OBJECT)
     {
         obj = static_cast<JSObject*>(p);
-        clazz = OBJ_GET_CLASS(cx, obj);
+        clazz = obj->getClass();
 
         if(clazz == &XPC_WN_Tearoff_JSClass)
         {
@@ -777,7 +777,7 @@ nsXPConnect::Traverse(void *p, nsCycleCollectionTraversalCallback &cb)
         if(traceKind == JSTRACE_OBJECT)
         {
             JSObject *obj = static_cast<JSObject*>(p);
-            JSClass *clazz = OBJ_GET_CLASS(cx, obj);
+            JSClass *clazz = obj->getClass();
             if(XPCNativeWrapper::IsNativeWrapperClass(clazz))
             {
                 XPCWrappedNative* wn;