dom/base/nsWrapperCache.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "nsWrapperCacheInlines.h"
   8
   9 #include "jsproxy.h"
  10 #include "mozilla/dom/DOMJSProxyHandler.h"
  11 #include "mozilla/HoldDropJSObjects.h"
  12 #include "nsCycleCollectionTraversalCallback.h"
  13 #include "nsCycleCollector.h"
  14
  15 using namespace mozilla;
  16 using namespace mozilla::dom;
  17
  18 /* static */ void
  19 nsWrapperCache::HoldJSObjects(void* aScriptObjectHolder,
  20                               nsScriptObjectTracer* aTracer)
  21 {
  22   cyclecollector::HoldJSObjectsImpl(aScriptObjectHolder, aTracer);
  23 }
  24
  25 void
  26 nsWrapperCache::ReleaseWrapper(void* aScriptObjectHolder)
  27 {
  28   if (PreservingWrapper()) {
  29     // PreserveWrapper puts new DOM bindings in the JS holders hash, but they
  30     // can also be in the DOM expando hash, so we need to try to remove them
  31     // from both here.
  32     JSObject* obj = GetWrapperPreserveColor();
  33     if (IsDOMBinding() && obj && js::IsProxy(obj)) {
  34       DOMProxyHandler::GetAndClearExpandoObject(obj);
  35     }
  36     SetPreservingWrapper(false);
  37     cyclecollector::DropJSObjectsImpl(aScriptObjectHolder);
  38   }
  39 }
  40
  41 #ifdef DEBUG
  42
  43 class DebugWrapperTraversalCallback : public nsCycleCollectionTraversalCallback
  44 {
  45 public:
  46   explicit DebugWrapperTraversalCallback(void* aWrapper)
  47     : mFound(false)
  48     , mWrapper(aWrapper)
  49   {
  50     mFlags = WANT_ALL_TRACES;
  51   }
  52
  53   NS_IMETHOD_(void) DescribeRefCountedNode(nsrefcnt aRefCount,
  54                                            const char* aObjName)
  55   {
  56   }
  57   NS_IMETHOD_(void) DescribeGCedNode(bool aIsMarked,
  58                                      const char* aObjName,
  59                                      uint64_t aCompartmentAddress)
  60   {
  61   }
  62
  63   NS_IMETHOD_(void) NoteJSChild(void* aChild)
  64   {
  65     if (aChild == mWrapper) {
  66       mFound = true;
  67     }
  68   }
  69   NS_IMETHOD_(void) NoteXPCOMChild(nsISupports* aChild)
  70   {
  71   }
  72   NS_IMETHOD_(void) NoteNativeChild(void* aChild,
  73                                     nsCycleCollectionParticipant* aHelper)
  74   {
  75   }
  76
  77   NS_IMETHOD_(void) NoteNextEdgeName(const char* aName)
  78   {
  79   }
  80
  81   bool mFound;
  82
  83 private:
  84   void* mWrapper;
  85 };
  86
  87 static void
  88 DebugWrapperTraceCallback(void* aP, const char* aName, void* aClosure)
  89 {
  90   DebugWrapperTraversalCallback* callback =
  91     static_cast<DebugWrapperTraversalCallback*>(aClosure);
  92   callback->NoteJSChild(aP);
  93 }
  94
  95 void
  96 nsWrapperCache::CheckCCWrapperTraversal(void* aScriptObjectHolder,
  97                                         nsScriptObjectTracer* aTracer)
  98 {
  99   JSObject* wrapper = GetWrapper();
 100   if (!wrapper) {
 101     return;
 102   }
 103
 104   DebugWrapperTraversalCallback callback(wrapper);
 105
 106   aTracer->Traverse(aScriptObjectHolder, callback);
 107   MOZ_ASSERT(callback.mFound,
 108              "Cycle collection participant didn't traverse to preserved "
 109              "wrapper! This will probably crash.");
 110
 111   callback.mFound = false;
 112   aTracer->Trace(aScriptObjectHolder,
 113                  TraceCallbackFunc(DebugWrapperTraceCallback), &callback);
 114   MOZ_ASSERT(callback.mFound,
 115              "Cycle collection participant didn't trace preserved wrapper! "
 116              "This will probably crash.");
 117 }
 118
 119 #endif // DEBUG