Bug 453432 - Checking for MaybeGC conditions when allocating GC things.

r=igor,mrbkap a191=blocker

dom/src/base/nsJSEnvironment.cpp

@@ -850,24 +850,8 @@ PrintWinCodebase(nsGlobalWindow *win)
 }
 #endif
 
-// The accumulated operation weight before we call MaybeGC
+// The accumulated operation weight for DOM callback.
-const PRUint32 MAYBE_GC_OPERATION_WEIGHT = 5000 * JS_OPERATION_WEIGHT_BASE;
+const PRUint32 DOM_CALLBACK_OPERATION_WEIGHT = 5000 * JS_OPERATION_WEIGHT_BASE;
-
-static void
-MaybeGC(JSContext *cx)
-{
-  size_t bytes = cx->runtime->gcBytes;
-  size_t lastBytes = cx->runtime->gcLastBytes;
-
-  if ((bytes > 8192 && bytes / 16 > lastBytes)
-#ifdef DEBUG
-      || cx->runtime->gcZeal > 0
-#endif
-      ) {
-    ++sGCCount;
-    JS_GC(cx);
-  }
-}
 
 static already_AddRefed<nsIPrompt>
 GetPromptFromContext(nsJSContext* ctx)
@@ -900,17 +884,8 @@ nsJSContext::DOMOperationCallback(JSContext *cx)
     return JS_TRUE;
   }
 
-  // XXX Save the operation callback time so we can restore it after the GC,
-  // because GCing can cause JS to run on our context, causing our
-  // ScriptEvaluated to be called, and clearing our operation callback time.
-  // See bug 302333.
   PRTime callbackTime = ctx->mOperationCallbackTime;
 
-  MaybeGC(cx);
-
-  // Now restore the callback time and count, in case they got reset.
-  ctx->mOperationCallbackTime = callbackTime;
-
   // Check to see if we are running OOM
   nsCOMPtr<nsIMemory> mem;
   NS_GetMemoryManager(getter_AddRefs(mem));
@@ -932,24 +907,24 @@ nsJSContext::DOMOperationCallback(JSContext *cx)
 
         if (nsContentUtils::GetBoolPref("dom.prevent_oom_dialog", PR_FALSE))
           return JS_FALSE;
-        
+
         nsCOMPtr<nsIPrompt> prompt = GetPromptFromContext(ctx);
-        
+
         nsXPIDLString title, msg;
         rv = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                                 "LowMemoryTitle",
                                                 title);
-        
+
         rv |= nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                                  "LowMemoryMessage",
                                                  msg);
-        
+
         //GetStringFromName can return NS_OK and still give NULL string
         if (NS_FAILED(rv) || !title || !msg) {
           NS_ERROR("Failed to get localized strings.");
           return JS_FALSE;
         }
-        
+
         prompt->Alert(title, msg);
         return JS_FALSE;
       }
@@ -1238,7 +1213,7 @@ nsJSContext::nsJSContext(JSRuntime *aRuntime) : mGCOnDestruction(PR_TRUE)
                                          this);
 
     ::JS_SetOperationCallback(mContext, DOMOperationCallback,
-                              MAYBE_GC_OPERATION_WEIGHT);
+                              DOM_CALLBACK_OPERATION_WEIGHT);
 
     static JSLocaleCallbacks localeCallbacks =
       {
@@ -1251,7 +1226,6 @@ nsJSContext::nsJSContext(JSRuntime *aRuntime) : mGCOnDestruction(PR_TRUE)
     ::JS_SetLocaleCallbacks(mContext, &localeCallbacks);
   }
   mIsInitialized = PR_FALSE;
-  mNumEvaluations = 0;
   mTerminations = nsnull;
   mScriptsEnabled = PR_TRUE;
   mOperationCallbackTime = LL_ZERO;
@@ -3294,21 +3268,7 @@ nsJSContext::ScriptEvaluated(PRBool aTerminated)
     delete start;
   }
 
-  mNumEvaluations++;
+  mOperationCallbackTime = LL_ZERO;
-
-#ifdef JS_GC_ZEAL
-  if (mContext->runtime->gcZeal >= 2) {
-    MaybeGC(mContext);
-  } else
-#endif
-  if (mNumEvaluations > 20) {
-    mNumEvaluations = 0;
-    MaybeGC(mContext);
-  }
-
-  if (aTerminated) {
-    mOperationCallbackTime = LL_ZERO;
-  }
 }
 
 nsresult
@@ -3392,19 +3352,29 @@ nsJSContext::CC()
 #endif
   sPreviousCCTime = PR_Now();
   sDelayedCCollectCount = 0;
-  sGCCount = 0;
+  sGCCount = JS_GetGCParameter(nsJSRuntime::sRuntime, JSGC_NUMBER);
   sCCSuspectChanges = 0;
   // nsCycleCollector_collect() will run a ::JS_GC() indirectly, so
   // we do not explicitly call ::JS_GC() here.
   sCollectedObjectsCounts = nsCycleCollector_collect();
   sCCSuspectedCount = nsCycleCollector_suspectedCount();
 #ifdef DEBUG_smaug
-  printf("Collected %u objects, %u suspected objects, took %lldms\n",
+  printf("Collected %u objects, %u suspected objects\n",
-         sCollectedObjectsCounts, sCCSuspectedCount,
+         sCollectedObjectsCounts, sCCSuspectedCount);
-         (PR_Now() - sPreviousCCTime) / PR_USEC_PER_MSEC);
 #endif
 }
 
+static inline uint32
+GetGCRunsCount()
+{
+    /*
+     * The result value may overflow if sGCCount is close to the uint32
+     * maximum. It may cause additional invocations of the CC, which may
+     * reduce performance but cannot breach security.
+     */
+    return JS_GetGCParameter(nsJSRuntime::sRuntime, JSGC_NUMBER) - sGCCount;
+}
+
 //static
 PRBool
 nsJSContext::MaybeCC(PRBool aHigherProbability)
@@ -3413,7 +3383,7 @@ nsJSContext::MaybeCC(PRBool aHigherProbability)
 
   // Don't check suspected count if CC will be called anyway.
   if (sCCSuspectChanges <= NS_MIN_SUSPECT_CHANGES ||
-      sGCCount <= NS_MAX_GC_COUNT) {
+      GetGCRunsCount() <= NS_MAX_GC_COUNT) {
 #ifdef DEBUG_smaug
     PRTime now = PR_Now();
 #endif
@@ -3431,7 +3401,8 @@ nsJSContext::MaybeCC(PRBool aHigherProbability)
   }
 #ifdef DEBUG_smaug
   printf("sCCSuspectChanges %u, sGCCount %u\n",
-         sCCSuspectChanges, sGCCount);
+         sCCSuspectChanges,
+         GetGCRunsCount());
 #endif
 
   // Increase the probability also if the previous call to cycle collector
@@ -3444,7 +3415,7 @@ nsJSContext::MaybeCC(PRBool aHigherProbability)
   if (!sGCTimer &&
       (sDelayedCCollectCount > NS_MAX_DELAYED_CCOLLECT) &&
       ((sCCSuspectChanges > NS_MIN_SUSPECT_CHANGES &&
-        sGCCount > NS_MAX_GC_COUNT) ||
+        GetGCRunsCount() > NS_MAX_GC_COUNT) ||
        (sCCSuspectChanges > NS_MAX_SUSPECT_CHANGES))) {
     if ((PR_Now() - sPreviousCCTime) >=
         PRTime(NS_MIN_CC_INTERVAL * PR_USEC_PER_MSEC)) {

dom/src/base/nsJSEnvironment.h

@@ -213,19 +213,18 @@ protected:
 
   // given an nsISupports object (presumably an event target or some other
   // DOM object), get (or create) the JSObject wrapping it.
-  nsresult JSObjectFromInterface(nsISupports *aSup, void *aScript, 
+  nsresult JSObjectFromInterface(nsISupports *aSup, void *aScript,
                                  JSObject **aRet);
 
 private:
   void Unlink();
 
   JSContext *mContext;
-  PRUint32 mNumEvaluations;
 
 protected:
   struct TerminationFuncHolder;
   friend struct TerminationFuncHolder;
-  
+
   struct TerminationFuncClosure
   {
     TerminationFuncClosure(nsScriptTerminationFunc aFunc,
@@ -240,7 +239,7 @@ protected:
     {
       delete mNext;
     }
-    
+
     nsScriptTerminationFunc mTerminationFunc;
     nsCOMPtr<nsISupports> mTerminationFuncArg;
     TerminationFuncClosure* mNext;
@@ -273,7 +272,7 @@ protected:
     nsJSContext* mContext;
     TerminationFuncClosure* mTerminations;
   };
-  
+
   TerminationFuncClosure* mTerminations;
 
 private:
@@ -319,7 +318,7 @@ public:
 
   virtual nsresult DropScriptObject(void *object);
   virtual nsresult HoldScriptObject(void *object);
-  
+
   static void Startup();
   static void Shutdown();
   // Setup all the statics etc - safe to call multiple times after Startup()

js/src/js.cpp

@@ -186,14 +186,8 @@ my_BranchCallback(JSContext *cx, JSScript *script)
         return JS_FALSE;
     }
 #ifdef JS_THREADSAFE
-    if ((gBranchCount & 0xff) == 1) {
+    if ((gBranchCount & 0xff) == 1)
-#endif
+        JS_YieldRequest(cx);
-        if ((gBranchCount & 0x3fff) == 1)
-            JS_MaybeGC(cx);
-#ifdef JS_THREADSAFE
-        else
-            JS_YieldRequest(cx);
-    }
 #endif
     return JS_TRUE;
 }
@@ -471,7 +465,7 @@ extern void js_InitJITStatsClass(JSContext *cx, JSObject *glob);
                             &jitstats_class, NULL, 0);
 #endif
             break;
-            
+
         case 'o':
             if (++i == argc)
                 return usage();
@@ -866,24 +860,49 @@ GCParameter(JSContext *cx, uintN argc, jsval *vp)
         param = JSGC_MAX_BYTES;
     } else if (strcmp(paramName, "maxMallocBytes") == 0) {
         param = JSGC_MAX_MALLOC_BYTES;
+    } else if (strcmp(paramName, "gcStackpoolLifespan") == 0) {
+        param = JSGC_STACKPOOL_LIFESPAN;
+    } else if (strcmp(paramName, "gcBytes") == 0) {
+        param = JSGC_BYTES;
+    } else if (strcmp(paramName, "gcNumber") == 0) {
+        param = JSGC_NUMBER;
+    } else if (strcmp(paramName, "gcTriggerFactor") == 0) {
+        param = JSGC_TRIGGER_FACTOR;
     } else {
         JS_ReportError(cx,
-                       "the first argument argument must be either maxBytes "
+                       "the first argument argument must be maxBytes, "
-                       "or maxMallocBytes");
+                       "maxMallocBytes, gcStackpoolLifespan, gcBytes, "
+                       "gcNumber or gcTriggerFactor");
         return JS_FALSE;
     }
 
-    if (!JS_ValueToECMAUint32(cx, argc < 2 ? JSVAL_VOID : vp[3], &value))
+    if (argc == 1) {
+        value = JS_GetGCParameter(cx->runtime, param);
+        return JS_NewNumberValue(cx, value, &vp[0]);
+    }
+
+    if (param == JSGC_NUMBER ||
+        param == JSGC_BYTES) {
+        JS_ReportError(cx, "Attempt to change read-only parameter %s",
+                       paramName);
         return JS_FALSE;
-    if (value == 0) {
+    }
+
+    if (!JS_ValueToECMAUint32(cx, vp[3], &value)) {
         JS_ReportError(cx,
-                       "the second argument must be convertable to uint32 with "
+                       "the second argument must be convertable to uint32 "
-                       "non-zero value");
+                       "with non-zero value");
+        return JS_FALSE;
+    }
+    if (param == JSGC_TRIGGER_FACTOR && value < 100) {
+        JS_ReportError(cx,
+                       "the gcTriggerFactor value must be >= 100");
         return JS_FALSE;
     }
     JS_SetGCParameter(cx->runtime, param, value);
     *vp = JSVAL_VOID;
     return JS_TRUE;
+
 }
 
 #ifdef JS_GC_ZEAL
@@ -1451,7 +1470,7 @@ DisassFile(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
     JSScript *script;
     JSBool ok;
     uint32 oldopts;
-    
+
     if (!argc)
         return JS_TRUE;
 
@@ -1471,7 +1490,7 @@ DisassFile(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
     obj = JS_NewScriptObject(cx, script);
     if (!obj)
         return JS_FALSE;
-    
+
     *rval = OBJECT_TO_JSVAL(obj); /* I like to root it, root it. */
     ok = Disassemble(cx, obj, 1, rval, rval); /* gross, but works! */
     *rval = JSVAL_VOID;

js/src/jsapi.cpp

@@ -2593,6 +2593,31 @@ JS_SetGCParameter(JSRuntime *rt, JSGCParamKey key, uint32 value)
       case JSGC_STACKPOOL_LIFESPAN:
         rt->gcEmptyArenaPoolLifespan = value;
         break;
+      default:
+        JS_ASSERT(key == JSGC_TRIGGER_FACTOR);
+        JS_ASSERT(value >= 100);
+        rt->gcTriggerFactor = value;
+        return;
+    }
+}
+
+JS_PUBLIC_API(uint32)
+JS_GetGCParameter(JSRuntime *rt, JSGCParamKey key)
+{
+    switch (key) {
+      case JSGC_MAX_BYTES:
+        return rt->gcMaxBytes;
+      case JSGC_MAX_MALLOC_BYTES:
+        return rt->gcMaxMallocBytes;
+      case JSGC_STACKPOOL_LIFESPAN:
+        return rt->gcEmptyArenaPoolLifespan;
+      case JSGC_TRIGGER_FACTOR:
+        return rt->gcTriggerFactor;
+      case JSGC_BYTES:
+        return rt->gcBytes;
+      default:
+        JS_ASSERT(key == JSGC_NUMBER);
+        return rt->gcNumber;
     }
 }
 
@@ -3807,7 +3832,7 @@ JS_HasUCProperty(JSContext *cx, JSObject *obj,
     JSProperty *prop;
 
     CHECK_REQUEST(cx);
-    ok = LookupUCProperty(cx, obj, name, namelen, 
+    ok = LookupUCProperty(cx, obj, name, namelen,
                           JSRESOLVE_QUALIFIED | JSRESOLVE_DETECTING,
                           &obj2, &prop);
     if (ok) {

js/src/jsapi.h

@@ -1134,12 +1134,31 @@ typedef enum JSGCParamKey {
     JSGC_MAX_MALLOC_BYTES   = 1,
 
     /* Hoard stackPools for this long, in ms, default is 30 seconds. */
-    JSGC_STACKPOOL_LIFESPAN = 2
+    JSGC_STACKPOOL_LIFESPAN = 2,
+
+    /*
+     * The factor that defines when the GC is invoked. The factor is a
+     * percent of the memory allocated by the GC after the last run of
+     * the GC. When the current memory allocated by the GC is more than
+     * this percent then the GC is invoked. The factor cannot be less
+     * than 100 since the current memory allocated by the GC cannot be less
+     * than the memory allocated after the last run of the GC.
+     */
+    JSGC_TRIGGER_FACTOR = 3,
+
+    /* Amount of bytes allocated by the GC. */
+    JSGC_BYTES = 4,
+
+    /* Number of times when GC was invoked. */
+    JSGC_NUMBER = 5
 } JSGCParamKey;
 
 extern JS_PUBLIC_API(void)
 JS_SetGCParameter(JSRuntime *rt, JSGCParamKey key, uint32 value);
 
+extern JS_PUBLIC_API(uint32)
+JS_GetGCParameter(JSRuntime *rt, JSGCParamKey key);
+
 /*
  * Add a finalizer for external strings created by JS_NewExternalString (see
  * below) using a type-code returned from this function, and that understands

js/src/jscntxt.h

@@ -253,6 +253,7 @@ struct JSRuntime {
     uint32              gcLevel;
     uint32              gcNumber;
     JSTracer            *gcMarkingTracer;
+    uint32              gcTriggerFactor;
 
     /*
      * NB: do not pack another flag here by claiming gcPadding unless the new

js/src/jsgc.cpp

@@ -1253,6 +1253,18 @@ js_InitGC(JSRuntime *rt, uint32 maxbytes)
     rt->gcMaxBytes = rt->gcMaxMallocBytes = maxbytes;
     rt->gcEmptyArenaPoolLifespan = 30000;
 
+    /*
+     * By default the trigger factor gets maximum possible value. This
+     * means that GC will not be triggered by growth of GC memory (gcBytes).
+     */
+    rt->gcTriggerFactor = (uint32) -1;
+
+    /*
+     * The assigned value prevents GC from running when GC memory is too low
+     * (during JS engine start).
+     */
+    rt->gcLastBytes = 8192;
+
     METER(memset(&rt->gcStats, 0, sizeof rt->gcStats));
     return JS_TRUE;
 }
@@ -1757,6 +1769,17 @@ EnsureLocalFreeList(JSContext *cx)
 
 #endif
 
+static JS_INLINE JSBool
+IsGCThresholdReached(JSRuntime *rt)
+{
+    /*
+     * Since the initial value of the gcLastBytes parameter is not equal to
+     * zero (see the js_InitGC function) the return value is false when
+     * the gcBytes value is close to zero at the JS engine start.
+     */
+    return rt->gcBytes / rt->gcTriggerFactor >= rt->gcLastBytes / 100;
+}
+
 void *
 js_NewGCThing(JSContext *cx, uintN flags, size_t nbytes)
 {
@@ -1823,7 +1846,8 @@ js_NewGCThing(JSContext *cx, uintN flags, size_t nbytes)
         return NULL;
     }
 
-    doGC = (rt->gcMallocBytes >= rt->gcMaxMallocBytes && rt->gcPoke);
+    doGC = (rt->gcMallocBytes >= rt->gcMaxMallocBytes && rt->gcPoke) ||
+           IsGCThresholdReached(rt);
 #ifdef JS_GC_ZEAL
     doGC = doGC || rt->gcZeal >= 2 || (rt->gcZeal >= 1 && rt->gcPoke);
 #endif
@@ -2033,9 +2057,10 @@ RefillDoubleFreeList(JSContext *cx)
         return NULL;
     }
 
-    if (rt->gcMallocBytes >= rt->gcMaxMallocBytes && rt->gcPoke
+    if ((rt->gcMallocBytes >= rt->gcMaxMallocBytes && rt->gcPoke) ||
+        IsGCThresholdReached(rt)
 #ifdef JS_GC_ZEAL
-        && (rt->gcZeal >= 2 || (rt->gcZeal >= 1 && rt->gcPoke))
+        || (rt->gcZeal >= 2 || (rt->gcZeal >= 1 && rt->gcPoke))
 #endif
         ) {
         goto do_gc;
@@ -2207,7 +2232,8 @@ js_AddAsGCBytes(JSContext *cx, size_t sz)
 
     rt = cx->runtime;
     if (rt->gcBytes >= rt->gcMaxBytes ||
-        sz > (size_t) (rt->gcMaxBytes - rt->gcBytes)
+        sz > (size_t) (rt->gcMaxBytes - rt->gcBytes) ||
+        IsGCThresholdReached(rt)
 #ifdef JS_GC_ZEAL
         || rt->gcZeal >= 2 || (rt->gcZeal >= 1 && rt->gcPoke)
 #endif

js/src/xpconnect/src/xpcjsruntime.cpp

@@ -216,7 +216,7 @@ static JSDHashOperator
 DetachedWrappedNativeProtoMarker(JSDHashTable *table, JSDHashEntryHdr *hdr,
                                  uint32 number, void *arg)
 {
-    XPCWrappedNativeProto* proto = 
+    XPCWrappedNativeProto* proto =
         (XPCWrappedNativeProto*)((JSDHashEntryStub*)hdr)->key;
 
     proto->Mark();
@@ -309,7 +309,7 @@ void XPCJSRuntime::TraceJS(JSTracer* trc, void* data)
     // them here.
     for(XPCRootSetElem *e = self->mObjectHolderRoots; e ; e = e->GetNextRoot())
         static_cast<XPCJSObjectHolder*>(e)->TraceJS(trc);
-        
+
     if(self->GetXPConnect()->ShouldTraceRoots())
     {
         // Only trace these if we're not cycle-collecting, the cycle collector
@@ -527,7 +527,7 @@ JSBool XPCJSRuntime::GCCallback(JSContext *cx, JSGCStatus status)
             case JSGC_MARK_END:
             {
                 NS_ASSERTION(!self->mDoingFinalization, "bad state");
-    
+
                 // mThreadRunningGC indicates that GC is running
                 { // scoped lock
                     XPCAutoLock lock(self->GetMapLock());
@@ -550,8 +550,8 @@ JSBool XPCJSRuntime::GCCallback(JSContext *cx, JSGCStatus status)
                         Enumerate(WrappedJSDyingJSObjectFinder, &data);
                 }
 
-                // Do cleanup in NativeInterfaces. This part just finds 
+                // Do cleanup in NativeInterfaces. This part just finds
-                // member cloned function objects that are about to be 
+                // member cloned function objects that are about to be
                 // collected. It does not deal with collection of interfaces or
                 // sets at this point.
                 CX_AND_XPCRT_Data data = {cx, self};
@@ -716,7 +716,7 @@ JSBool XPCJSRuntime::GCCallback(JSContext *cx, JSGCStatus status)
                     if(threadLock)
                     {
                         // Do the marking...
-                        
+
                         { // scoped lock
                             nsAutoLock lock(threadLock);
 
@@ -735,7 +735,7 @@ JSBool XPCJSRuntime::GCCallback(JSContext *cx, JSGCStatus status)
                                     // possibly be valid.
                                     if(ccxp->CanGetTearOff())
                                     {
-                                        XPCWrappedNativeTearOff* to = 
+                                        XPCWrappedNativeTearOff* to =
                                             ccxp->GetTearOff();
                                         if(to)
                                             to->Mark();
@@ -744,7 +744,7 @@ JSBool XPCJSRuntime::GCCallback(JSContext *cx, JSGCStatus status)
                                 }
                             }
                         }
-    
+
                         // Do the sweeping...
                         XPCWrappedNativeScope::SweepAllWrappedNativeTearOffs();
                     }
@@ -850,7 +850,7 @@ static JSDHashOperator
 DetachedWrappedNativeProtoShutdownMarker(JSDHashTable *table, JSDHashEntryHdr *hdr,
                                          uint32 number, void *arg)
 {
-    XPCWrappedNativeProto* proto = 
+    XPCWrappedNativeProto* proto =
         (XPCWrappedNativeProto*)((JSDHashEntryStub*)hdr)->key;
 
     proto->SystemIsBeingShutDown((JSContext*)arg);
@@ -1084,6 +1084,9 @@ XPCJSRuntime::XPCJSRuntime(nsXPConnect* aXPConnect)
         JS_SetContextCallback(mJSRuntime, ContextCallback);
         JS_SetGCCallbackRT(mJSRuntime, GCCallback);
         JS_SetExtraGCRoots(mJSRuntime, TraceJS, this);
+
+        // GC will be called when gcBytes is 1600% of gcLastBytes.
+        JS_SetGCParameter(mJSRuntime, JSGC_TRIGGER_FACTOR, 1600);
     }
 
     if(!JS_DHashTableInit(&mJSHolders, JS_DHashGetStubOps(), nsnull,

js/src/xpconnect/src/xpcprivate.h

@@ -275,22 +275,22 @@ extern const char XPC_XPCONNECT_CONTRACTID[];
 
 typedef PRMonitor XPCLock;
 
-static inline void xpc_Wait(XPCLock* lock) 
+static inline void xpc_Wait(XPCLock* lock)
     {
         NS_ASSERTION(lock, "xpc_Wait called with null lock!");
 #ifdef DEBUG
-        PRStatus result = 
+        PRStatus result =
 #endif
         PR_Wait(lock, PR_INTERVAL_NO_TIMEOUT);
         NS_ASSERTION(PR_SUCCESS == result, "bad result from PR_Wait!");
     }
 
-static inline void xpc_NotifyAll(XPCLock* lock) 
+static inline void xpc_NotifyAll(XPCLock* lock)
     {
         NS_ASSERTION(lock, "xpc_NotifyAll called with null lock!");
 #ifdef DEBUG
-        PRStatus result = 
+        PRStatus result =
-#endif    
+#endif
         PR_NotifyAll(lock);
         NS_ASSERTION(PR_SUCCESS == result, "bad result from PR_NotifyAll!");
     }
@@ -510,7 +510,7 @@ public:
     NS_IMETHOD Unroot(void *p);
     NS_IMETHOD Traverse(void *p,
                         nsCycleCollectionTraversalCallback &cb);
-    
+
     // nsCycleCollectionLanguageRuntime
     virtual nsresult BeginCycleCollection(nsCycleCollectionTraversalCallback &cb);
     virtual nsresult FinishCycleCollection();
@@ -808,26 +808,26 @@ public:
     JSContext* GetJSContext() const {return mJSContext;}
 
     enum LangType {LANG_UNKNOWN, LANG_JS, LANG_NATIVE};
-    
+
     LangType GetCallingLangType() const
         {
             return mCallingLangType;
         }
     LangType SetCallingLangType(LangType lt)
         {
-            LangType tmp = mCallingLangType; 
+            LangType tmp = mCallingLangType;
-            mCallingLangType = lt; 
+            mCallingLangType = lt;
             return tmp;
         }
-    JSBool CallerTypeIsJavaScript() const 
+    JSBool CallerTypeIsJavaScript() const
         {
             return LANG_JS == mCallingLangType;
         }
-    JSBool CallerTypeIsNative() const 
+    JSBool CallerTypeIsNative() const
         {
             return LANG_NATIVE == mCallingLangType;
         }
-    JSBool CallerTypeIsKnown() const 
+    JSBool CallerTypeIsKnown() const
         {
             return LANG_UNKNOWN != mCallingLangType;
         }
@@ -1244,7 +1244,7 @@ public:
     {return mScriptObjectPrincipal ?
          mScriptObjectPrincipal->GetPrincipal() : nsnull;}
 #endif
-    
+
     JSObject*
     GetPrototypeJSFunction() const {return mPrototypeJSFunction;}
 
@@ -1977,7 +1977,7 @@ public:
 
     // Yes, we *do* need to mark the mScriptableInfo in both cases.
     void Mark() const
-        {mSet->Mark(); 
+        {mSet->Mark();
          if(mScriptableInfo) mScriptableInfo->Mark();}
 
 #ifdef DEBUG
@@ -2499,9 +2499,9 @@ public:
                                             JSObject* aJSObj,
                                             nsISimpleEnumerator** aEnumerate);
 
-    static nsresult GetNamedPropertyAsVariant(XPCCallContext& ccx, 
+    static nsresult GetNamedPropertyAsVariant(XPCCallContext& ccx,
                                               JSObject* aJSObj,
-                                              jsval aName, 
+                                              jsval aName,
                                               nsIVariant** aResult);
 
     virtual ~nsXPCWrappedJSClass();
@@ -2737,7 +2737,7 @@ public:
      * @param scope the default scope to put on the new JSObject's __parent__
      *        chain
      * @param pErr [out] relevant error code, if any.
-     */    
+     */
     static JSBool NativeData2JS(XPCCallContext& ccx, jsval* d, const void* s,
                                 const nsXPTType& type, const nsID* iid,
                                 JSObject* scope, nsresult* pErr);
@@ -2771,7 +2771,7 @@ public:
 
     static JSBool GetNativeInterfaceFromJSObject(XPCCallContext& ccx,
                                                  void** dest, JSObject* src,
-                                                 const nsID* iid, 
+                                                 const nsID* iid,
                                                  nsresult* pErr);
     static JSBool JSObject2NativeInterface(XPCCallContext& ccx,
                                            void** dest, JSObject* src,
@@ -2792,7 +2792,7 @@ public:
      * @param scope the default scope to put on the new JSObjects' __parent__
      *        chain
      * @param pErr [out] relevant error code, if any.
-     */    
+     */
     static JSBool NativeArray2JS(XPCCallContext& ccx,
                                  jsval* d, const void** s,
                                  const nsXPTType& type, const nsID* iid,
@@ -2880,7 +2880,7 @@ public:
     static void ThrowBadResult(nsresult rv, nsresult result, XPCCallContext& ccx);
     static void ThrowBadParam(nsresult rv, uintN paramNum, XPCCallContext& ccx);
 #ifdef XPC_IDISPATCH_SUPPORT
-    static void ThrowCOMError(JSContext* cx, unsigned long COMErrorCode, 
+    static void ThrowCOMError(JSContext* cx, unsigned long COMErrorCode,
                               nsresult rv = NS_ERROR_XPC_COM_ERROR,
                               const EXCEPINFO * exception = nsnull);
 #endif
@@ -3287,7 +3287,7 @@ private:
     static XPCPerThreadData* gThreads;
     static PRUintn           gTLSIndex;
 
-    // Cached value of cx->thread on the main thread. 
+    // Cached value of cx->thread on the main thread.
     static void *sMainJSThread;
 
     // Cached per thread data for the main thread. Only safe to access
@@ -3595,7 +3595,7 @@ private:
     JSContext *mCX;
     jsrefcount mDepth;
 };
-        
+
 
 /*****************************************/
 
@@ -3691,7 +3691,7 @@ public:
     ~AutoResolveName()
         {
 #ifdef DEBUG
-            jsval old = 
+            jsval old =
 #endif
             mTLS->SetResolveName(mOld);
             NS_ASSERTION(old == mCheck, "Bad Nesting!");
@@ -3717,17 +3717,17 @@ public:
     }
     void AutoTrace(JSTracer* trc) {}
 private:
-    XPCMarkableJSVal(); // not implemented    
+    XPCMarkableJSVal(); // not implemented
     jsval  mVal;
     jsval* mValPtr;
-}; 
+};
 
 /***************************************************************************/
-// AutoMarkingPtr is the base class for the various AutoMarking pointer types 
+// AutoMarkingPtr is the base class for the various AutoMarking pointer types
-// below. This system allows us to temporarily protect instances of our garbage 
+// below. This system allows us to temporarily protect instances of our garbage
-// collected types after they are constructed but before they are safely 
+// collected types after they are constructed but before they are safely
 // attached to other rooted objects.
-// This base class has pure virtual support for marking. 
+// This base class has pure virtual support for marking.
 
 class AutoMarkingPtr
 {
@@ -3736,15 +3736,15 @@ public:
         : mNext(nsnull), mTLS(ccx.GetThreadData()) {Link();}
 
     virtual ~AutoMarkingPtr() {Unlink();}
-    
+
-    void Link() 
+    void Link()
         {if(!mTLS) return;
-         AutoMarkingPtr** list = mTLS->GetAutoRootsAdr(); 
+         AutoMarkingPtr** list = mTLS->GetAutoRootsAdr();
          mNext = *list; *list = this;}
 
-    void Unlink() 
+    void Unlink()
         {if(!mTLS) return;
-         AutoMarkingPtr** cur = mTLS->GetAutoRootsAdr(); 
+         AutoMarkingPtr** cur = mTLS->GetAutoRootsAdr();
          while(*cur != this) {
             NS_ASSERTION(*cur, "This object not in list!");
             cur = &(*cur)->mNext;
@@ -3754,7 +3754,7 @@ public:
         }
 
     AutoMarkingPtr* GetNext() {return mNext;}
-    
+
     virtual void TraceJS(JSTracer* trc) = 0;
     virtual void MarkAfterJSFinalize() = 0;
 
@@ -3803,7 +3803,7 @@ DEFINE_AUTO_MARKING_PTR_TYPE(AutoMarkingWrappedNativePtr, XPCWrappedNative)
 DEFINE_AUTO_MARKING_PTR_TYPE(AutoMarkingWrappedNativeTearOffPtr, XPCWrappedNativeTearOff)
 DEFINE_AUTO_MARKING_PTR_TYPE(AutoMarkingWrappedNativeProtoPtr, XPCWrappedNativeProto)
 DEFINE_AUTO_MARKING_PTR_TYPE(AutoMarkingJSVal, XPCMarkableJSVal)
-                                    
+
 #define DEFINE_AUTO_MARKING_ARRAY_PTR_TYPE(class_, type_)                    \
 class class_ : public AutoMarkingPtr                                         \
 {                                                                            \
@@ -3858,9 +3858,9 @@ protected:                                                                   \
 
 DEFINE_AUTO_MARKING_ARRAY_PTR_TYPE(AutoMarkingNativeInterfacePtrArrayPtr,
                                    XPCNativeInterface)
-    
+
 // Note: It looked like I would need one of these AutoMarkingPtr types for
-// XPCNativeScriptableInfo in order to manage marking its 
+// XPCNativeScriptableInfo in order to manage marking its
 // XPCNativeScriptableShared member during construction. But AFAICT we build
 // these and bind them to rooted things so immediately that this just is not
 // needed.
@@ -3903,8 +3903,8 @@ public:
     // the case when mJSVal is JSVAL_STRING, since we don't own the data in
     // that case.
 
-    // We #define and iid so that out module local code can use QI to detect 
+    // We #define and iid so that out module local code can use QI to detect
-    // if a given nsIVariant is in fact an XPCVariant. 
+    // if a given nsIVariant is in fact an XPCVariant.
     NS_DECLARE_STATIC_IID_ACCESSOR(XPCVARIANT_IID)
 
     static XPCVariant* newVariant(XPCCallContext& ccx, jsval aJSVal);
@@ -3922,8 +3922,8 @@ public:
      *        chain
      * @param pErr [out] relevant error code, if any.
      * @param pJSVal [out] the resulting jsval.
-     */    
+     */
-    static JSBool VariantDataToJS(XPCCallContext& ccx, 
+    static JSBool VariantDataToJS(XPCCallContext& ccx,
                                   nsIVariant* variant,
                                   JSObject* scope, nsresult* pErr,
                                   jsval* pJSVal);