Bug 1587378 - Remove TraceCallbacks method that takes raw JSObject pointers r=mccr8

This method turned out to only be used for tracing wrapper cached things. The wrapper cache has its own way of implementing barriers and contains a raw JSObject pointer. Changing this trace method to take an nsWrapperCache pointer (effectively a JSObjct**) enforces correct use of Heap<T> for other TraceCallbacks callers.

Differential Revision: https://phabricator.services.mozilla.com/D48693

--HG--
extra : moz-landing-system : lando

dom/base/nsWrapperCache.h

@@ -232,7 +232,7 @@ class nsWrapperCache {
 
   void TraceWrapper(const TraceCallbacks& aCallbacks, void* aClosure) {
     if (PreservingWrapper() && mWrapper) {
-      aCallbacks.Trace(&mWrapper, "Preserved wrapper", aClosure);
+      aCallbacks.Trace(this, "Preserved wrapper", aClosure);
     }
   }
 
@@ -304,13 +304,13 @@ class nsWrapperCache {
 
   void ReleaseWrapper(void* aScriptObjectHolder);
 
- protected:
   void TraceWrapper(JSTracer* aTrc, const char* name) {
     if (mWrapper) {
       js::UnsafeTraceManuallyBarrieredEdge(aTrc, &mWrapper, name);
     }
   }
 
+ protected:
   void PoisonWrapper() {
     if (mWrapper) {
       // Set the pointer to a value that will cause a crash if it is

xpcom/base/CycleCollectedJSRuntime.cpp

@@ -985,10 +985,9 @@ struct JsGcTracer : public TraceCallbacks {
                      void* aClosure) const override {
     JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
   }
-  virtual void Trace(JSObject** aPtr, const char* aName,
+  virtual void Trace(nsWrapperCache* aPtr, const char* aName,
                      void* aClosure) const override {
-    js::UnsafeTraceManuallyBarrieredEdge(static_cast<JSTracer*>(aClosure), aPtr,
-                                         aName);
+    aPtr->TraceWrapper(static_cast<JSTracer*>(aClosure), aName);
   }
   virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
                      void* aClosure) const override {
@@ -1055,9 +1054,9 @@ struct ClearJSHolder : public TraceCallbacks {
     *aPtr = nullptr;
   }
 
-  virtual void Trace(JSObject** aPtr, const char* aName,
+  virtual void Trace(nsWrapperCache* aPtr, const char* aName,
                      void* aClosure) const override {
-    *aPtr = nullptr;
+    aPtr->ClearWrapper();
   }
 
   virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char*,

xpcom/base/nsCycleCollectionParticipant.h

@@ -49,6 +49,8 @@ class nsCycleCollectionISupports {
 NS_DEFINE_STATIC_IID_ACCESSOR(nsCycleCollectionISupports,
                               NS_CYCLECOLLECTIONISUPPORTS_IID)
 
+class nsWrapperCache;
+
 namespace JS {
 template <class T>
 class Heap;
@@ -66,7 +68,7 @@ struct TraceCallbacks {
                      void* aClosure) const = 0;
   virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
                      void* aClosure) const = 0;
-  virtual void Trace(JSObject** aPtr, const char* aName,
+  virtual void Trace(nsWrapperCache* aPtr, const char* aName,
                      void* aClosure) const = 0;
   virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
                      void* aClosure) const = 0;
@@ -94,7 +96,7 @@ struct TraceCallbackFunc : public TraceCallbacks {
                      void* aClosure) const override;
   virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
                      void* aClosure) const override;
-  virtual void Trace(JSObject** aPtr, const char* aName,
+  virtual void Trace(nsWrapperCache* aPtr, const char* aName,
                      void* aClosure) const override;
   virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
                      void* aClosure) const override;

xpcom/base/nsCycleCollector.cpp

@@ -2490,9 +2490,9 @@ class SnowWhiteKiller : public TraceCallbacks {
     AppendJSObjectToPurpleBuffer(aObject->unbarrieredGet());
   }
 
-  virtual void Trace(JSObject** aObject, const char* aName,
+  virtual void Trace(nsWrapperCache* aWrapperCache, const char* aName,
                      void* aClosure) const override {
-    AppendJSObjectToPurpleBuffer(*aObject);
+    AppendJSObjectToPurpleBuffer(aWrapperCache->GetWrapperPreserveColor());
   }
 
   virtual void Trace(JS::TenuredHeap<JSObject*>* aObject, const char* aName,

xpcom/base/nsCycleCollectorTraceJSHelpers.cpp

@@ -50,10 +50,11 @@ void TraceCallbackFunc::Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
   }
 }
 
-void TraceCallbackFunc::Trace(JSObject** aPtr, const char* aName,
+void TraceCallbackFunc::Trace(nsWrapperCache* aPtr, const char* aName,
                               void* aClosure) const {
-  if (*aPtr) {
-    mCallback(JS::GCCellPtr(*aPtr), aName, aClosure);
+  JSObject* obj = aPtr->GetWrapperPreserveColor();
+  if (obj) {
+    mCallback(JS::GCCellPtr(obj), aName, aClosure);
   }
 }