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b6da7dc336
For nsXPCWrappedJS, we need to add an edge to the cycle collector graph from the JS object to its WJS, even though the JS object does not actually contain a pointer to the WJS object. We can (mis)use the weak mapping interface for this purpose. The only difference is that we need it during traversal instead of while adding roots. The API is fairly specialized to the specific use case we need. Differential Revision: https://phabricator.services.mozilla.com/D157529
147 lines
4.8 KiB
C++
147 lines
4.8 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsWrapperCacheInlines.h"
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#include "jsfriendapi.h"
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#include "js/Class.h"
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#include "js/Proxy.h"
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#include "mozilla/CycleCollectedJSRuntime.h"
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#include "mozilla/HoldDropJSObjects.h"
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#include "nsCycleCollectionTraversalCallback.h"
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#include "nsCycleCollector.h"
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using namespace mozilla;
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using namespace mozilla::dom;
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#ifdef DEBUG
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/* static */
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bool nsWrapperCache::HasJSObjectMovedOp(JSObject* aWrapper) {
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return js::HasObjectMovedOp(aWrapper);
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}
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#endif
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void nsWrapperCache::HoldJSObjects(void* aScriptObjectHolder,
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nsScriptObjectTracer* aTracer,
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JS::Zone* aWrapperZone) {
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cyclecollector::HoldJSObjectsImpl(aScriptObjectHolder, aTracer, aWrapperZone);
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if (mWrapper && !JS::ObjectIsTenured(mWrapper)) {
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JS::HeapObjectPostWriteBarrier(&mWrapper, nullptr, mWrapper);
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}
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}
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static inline bool IsNurseryWrapper(JSObject* aWrapper) {
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return aWrapper && !JS::ObjectIsTenured(aWrapper);
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}
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void nsWrapperCache::SetWrapperJSObject(JSObject* aNewWrapper) {
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JSObject* oldWrapper = mWrapper;
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mWrapper = aNewWrapper;
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UnsetWrapperFlags(kWrapperFlagsMask);
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if (IsNurseryWrapper(aNewWrapper) && !IsNurseryWrapper(oldWrapper)) {
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CycleCollectedJSRuntime::Get()->NurseryWrapperAdded(this);
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}
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}
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void nsWrapperCache::ReleaseWrapper(void* aScriptObjectHolder) {
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// If the behavior here changes in a substantive way, you may need
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// to update css::Rule::UnlinkDeclarationWrapper as well.
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if (PreservingWrapper()) {
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SetPreservingWrapper(false);
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cyclecollector::DropJSObjectsImpl(aScriptObjectHolder);
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JS::HeapObjectPostWriteBarrier(&mWrapper, mWrapper, nullptr);
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}
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}
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#ifdef DEBUG
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void nsWrapperCache::AssertUpdatedWrapperZone(const JSObject* aNewObject,
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const JSObject* aOldObject) {
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MOZ_ASSERT(js::GetObjectZoneFromAnyThread(aNewObject) ==
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js::GetObjectZoneFromAnyThread(aOldObject));
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}
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class DebugWrapperTraversalCallback
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: public nsCycleCollectionTraversalCallback {
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public:
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explicit DebugWrapperTraversalCallback(JSObject* aWrapper)
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: mFound(false), mWrapper(JS::GCCellPtr(aWrapper)) {
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mFlags = WANT_ALL_TRACES;
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}
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NS_IMETHOD_(void)
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DescribeRefCountedNode(nsrefcnt aRefCount, const char* aObjName) override {}
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NS_IMETHOD_(void)
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DescribeGCedNode(bool aIsMarked, const char* aObjName,
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uint64_t aCompartmentAddress) override {}
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NS_IMETHOD_(void) NoteJSChild(JS::GCCellPtr aChild) override {
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if (aChild == mWrapper) {
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mFound = true;
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}
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}
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NS_IMETHOD_(void) NoteXPCOMChild(nsISupports* aChild) override {}
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NS_IMETHOD_(void)
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NoteNativeChild(void* aChild,
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nsCycleCollectionParticipant* aHelper) override {}
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NS_IMETHOD_(void)
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NoteWeakMapping(JSObject* aKey, nsISupports* aVal,
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nsCycleCollectionParticipant* aValParticipant) override {}
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NS_IMETHOD_(void) NoteNextEdgeName(const char* aName) override {}
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bool mFound;
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private:
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JS::GCCellPtr mWrapper;
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};
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static void DebugWrapperTraceCallback(JS::GCCellPtr aPtr, const char* aName,
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void* aClosure) {
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DebugWrapperTraversalCallback* callback =
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static_cast<DebugWrapperTraversalCallback*>(aClosure);
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if (aPtr.is<JSObject>()) {
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callback->NoteJSChild(aPtr);
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}
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}
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void nsWrapperCache::CheckCCWrapperTraversal(void* aScriptObjectHolder,
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nsScriptObjectTracer* aTracer) {
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JSObject* wrapper = GetWrapperPreserveColor();
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if (!wrapper) {
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return;
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}
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// Temporarily make this a preserving wrapper so that TraceWrapper() traces
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// it.
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bool wasPreservingWrapper = PreservingWrapper();
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SetPreservingWrapper(true);
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DebugWrapperTraversalCallback callback(wrapper);
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// The CC traversal machinery cannot trigger GC; however, the analysis cannot
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// see through the COM layer, so we use a suppression to help it.
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JS::AutoSuppressGCAnalysis suppress;
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aTracer->TraverseNativeAndJS(aScriptObjectHolder, callback);
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MOZ_ASSERT(callback.mFound,
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"Cycle collection participant didn't traverse to preserved "
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"wrapper! This will probably crash.");
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callback.mFound = false;
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aTracer->Trace(aScriptObjectHolder,
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TraceCallbackFunc(DebugWrapperTraceCallback), &callback);
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MOZ_ASSERT(callback.mFound,
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"Cycle collection participant didn't trace preserved wrapper! "
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"This will probably crash.");
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SetPreservingWrapper(wasPreservingWrapper);
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}
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#endif // DEBUG
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