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Diffstat (limited to 'xpcom/base/CycleCollectedJSRuntime.cpp')
| -rw-r--r-- | xpcom/base/CycleCollectedJSRuntime.cpp | 2027 |
1 files changed, 2027 insertions, 0 deletions
diff --git a/xpcom/base/CycleCollectedJSRuntime.cpp b/xpcom/base/CycleCollectedJSRuntime.cpp new file mode 100644 index 0000000000..03af9e3074 --- /dev/null +++ b/xpcom/base/CycleCollectedJSRuntime.cpp @@ -0,0 +1,2027 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +// We're dividing JS objects into 3 categories: +// +// 1. "real" roots, held by the JS engine itself or rooted through the root +// and lock JS APIs. Roots from this category are considered black in the +// cycle collector, any cycle they participate in is uncollectable. +// +// 2. certain roots held by C++ objects that are guaranteed to be alive. +// Roots from this category are considered black in the cycle collector, +// and any cycle they participate in is uncollectable. These roots are +// traced from TraceNativeBlackRoots. +// +// 3. all other roots held by C++ objects that participate in cycle collection, +// held by us (see TraceNativeGrayRoots). Roots from this category are +// considered grey in the cycle collector; whether or not they are collected +// depends on the objects that hold them. +// +// Note that if a root is in multiple categories the fact that it is in +// category 1 or 2 that takes precedence, so it will be considered black. +// +// During garbage collection we switch to an additional mark color (gray) when +// tracing inside TraceNativeGrayRoots. This allows us to walk those roots later +// on and add all objects reachable only from them to the cycle collector. +// +// Phases: +// +// 1. marking of the roots in category 1 by having the JS GC do its marking +// 2. marking of the roots in category 2 by having the JS GC call us back +// (via JS_SetExtraGCRootsTracer) and running TraceNativeBlackRoots +// 3. marking of the roots in category 3 by +// TraceNativeGrayRootsInCollectingZones using an additional color (gray). +// 4. end of GC, GC can sweep its heap +// +// At some later point, when the cycle collector runs: +// +// 5. walk gray objects and add them to the cycle collector, cycle collect +// +// JS objects that are part of cycles the cycle collector breaks will be +// collected by the next JS GC. +// +// If WantAllTraces() is false the cycle collector will not traverse roots +// from category 1 or any JS objects held by them. Any JS objects they hold +// will already be marked by the JS GC and will thus be colored black +// themselves. Any C++ objects they hold will have a missing (untraversed) +// edge from the JS object to the C++ object and so it will be marked black +// too. This decreases the number of objects that the cycle collector has to +// deal with. +// To improve debugging, if WantAllTraces() is true all JS objects are +// traversed. + +#include "mozilla/CycleCollectedJSRuntime.h" + +#include <algorithm> +#include <utility> + +#include "js/Debug.h" +#include "js/RealmOptions.h" +#include "js/friend/DumpFunctions.h" // js::DumpHeap +#include "js/GCAPI.h" +#include "js/HeapAPI.h" +#include "js/Object.h" // JS::GetClass, JS::GetCompartment, JS::GetPrivate +#include "js/PropertyAndElement.h" // JS_DefineProperty +#include "js/Warnings.h" // JS::SetWarningReporter +#include "js/ShadowRealmCallbacks.h" +#include "js/SliceBudget.h" +#include "jsfriendapi.h" +#include "mozilla/ArrayUtils.h" +#include "mozilla/AutoRestore.h" +#include "mozilla/CycleCollectedJSContext.h" +#include "mozilla/DebuggerOnGCRunnable.h" +#include "mozilla/MemoryReporting.h" +#include "mozilla/PerfStats.h" +#include "mozilla/ProfilerLabels.h" +#include "mozilla/ProfilerMarkers.h" +#include "mozilla/Sprintf.h" +#include "mozilla/StaticPrefs_javascript.h" +#include "mozilla/Telemetry.h" +#include "mozilla/Unused.h" +#include "mozilla/dom/AutoEntryScript.h" +#include "mozilla/dom/DOMJSClass.h" +#include "mozilla/dom/JSExecutionManager.h" +#include "mozilla/dom/Promise.h" +#include "mozilla/dom/PromiseBinding.h" +#include "mozilla/dom/PromiseDebugging.h" +#include "mozilla/dom/ScriptSettings.h" +#include "mozilla/dom/ShadowRealmGlobalScope.h" +#include "mozilla/dom/RegisterShadowRealmBindings.h" +#include "nsContentUtils.h" +#include "nsCycleCollectionNoteRootCallback.h" +#include "nsCycleCollectionParticipant.h" +#include "nsCycleCollector.h" +#include "nsDOMJSUtils.h" +#include "nsExceptionHandler.h" +#include "nsJSUtils.h" +#include "nsStringBuffer.h" +#include "nsWrapperCache.h" +#include "prenv.h" + +#if defined(XP_MACOSX) +# include "nsMacUtilsImpl.h" +#endif + +#include "nsThread.h" +#include "nsThreadUtils.h" +#include "xpcpublic.h" + +#ifdef NIGHTLY_BUILD +// For performance reasons, we make the JS Dev Error Interceptor a Nightly-only +// feature. +# define MOZ_JS_DEV_ERROR_INTERCEPTOR = 1 +#endif // NIGHTLY_BUILD + +using namespace mozilla; +using namespace mozilla::dom; + +namespace mozilla { + +struct DeferredFinalizeFunctionHolder { + DeferredFinalizeFunction run; + void* data; +}; + +class IncrementalFinalizeRunnable : public DiscardableRunnable { + typedef AutoTArray<DeferredFinalizeFunctionHolder, 16> DeferredFinalizeArray; + typedef CycleCollectedJSRuntime::DeferredFinalizerTable + DeferredFinalizerTable; + + CycleCollectedJSRuntime* mRuntime; + DeferredFinalizeArray mDeferredFinalizeFunctions; + uint32_t mFinalizeFunctionToRun; + bool mReleasing; + + static const PRTime SliceMillis = 5; /* ms */ + + public: + IncrementalFinalizeRunnable(CycleCollectedJSRuntime* aRt, + DeferredFinalizerTable& aFinalizerTable); + virtual ~IncrementalFinalizeRunnable(); + + void ReleaseNow(bool aLimited); + + NS_DECL_NSIRUNNABLE +}; + +} // namespace mozilla + +struct NoteWeakMapChildrenTracer : public JS::CallbackTracer { + NoteWeakMapChildrenTracer(JSRuntime* aRt, + nsCycleCollectionNoteRootCallback& aCb) + : JS::CallbackTracer(aRt, JS::TracerKind::Callback), + mCb(aCb), + mTracedAny(false), + mMap(nullptr), + mKey(nullptr), + mKeyDelegate(nullptr) {} + void onChild(JS::GCCellPtr aThing, const char* name) override; + nsCycleCollectionNoteRootCallback& mCb; + bool mTracedAny; + JSObject* mMap; + JS::GCCellPtr mKey; + JSObject* mKeyDelegate; +}; + +void NoteWeakMapChildrenTracer::onChild(JS::GCCellPtr aThing, + const char* name) { + if (aThing.is<JSString>()) { + return; + } + + if (!JS::GCThingIsMarkedGrayInCC(aThing) && !mCb.WantAllTraces()) { + return; + } + + if (JS::IsCCTraceKind(aThing.kind())) { + mCb.NoteWeakMapping(mMap, mKey, mKeyDelegate, aThing); + mTracedAny = true; + } else { + JS::TraceChildren(this, aThing); + } +} + +struct NoteWeakMapsTracer : public js::WeakMapTracer { + NoteWeakMapsTracer(JSRuntime* aRt, nsCycleCollectionNoteRootCallback& aCccb) + : js::WeakMapTracer(aRt), mCb(aCccb), mChildTracer(aRt, aCccb) {} + void trace(JSObject* aMap, JS::GCCellPtr aKey, JS::GCCellPtr aValue) override; + nsCycleCollectionNoteRootCallback& mCb; + NoteWeakMapChildrenTracer mChildTracer; +}; + +void NoteWeakMapsTracer::trace(JSObject* aMap, JS::GCCellPtr aKey, + JS::GCCellPtr aValue) { + // If nothing that could be held alive by this entry is marked gray, return. + if ((!aKey || !JS::GCThingIsMarkedGrayInCC(aKey)) && + MOZ_LIKELY(!mCb.WantAllTraces())) { + if (!aValue || !JS::GCThingIsMarkedGrayInCC(aValue) || + aValue.is<JSString>()) { + return; + } + } + + // The cycle collector can only properly reason about weak maps if it can + // reason about the liveness of their keys, which in turn requires that + // the key can be represented in the cycle collector graph. All existing + // uses of weak maps use either objects or scripts as keys, which are okay. + MOZ_ASSERT(JS::IsCCTraceKind(aKey.kind())); + + // As an emergency fallback for non-debug builds, if the key is not + // representable in the cycle collector graph, we treat it as marked. This + // can cause leaks, but is preferable to ignoring the binding, which could + // cause the cycle collector to free live objects. + if (!JS::IsCCTraceKind(aKey.kind())) { + aKey = nullptr; + } + + JSObject* kdelegate = nullptr; + if (aKey.is<JSObject>()) { + kdelegate = js::UncheckedUnwrapWithoutExpose(&aKey.as<JSObject>()); + } + + if (JS::IsCCTraceKind(aValue.kind())) { + mCb.NoteWeakMapping(aMap, aKey, kdelegate, aValue); + } else { + mChildTracer.mTracedAny = false; + mChildTracer.mMap = aMap; + mChildTracer.mKey = aKey; + mChildTracer.mKeyDelegate = kdelegate; + + if (!aValue.is<JSString>()) { + JS::TraceChildren(&mChildTracer, aValue); + } + + // The delegate could hold alive the key, so report something to the CC + // if we haven't already. + if (!mChildTracer.mTracedAny && aKey && JS::GCThingIsMarkedGrayInCC(aKey) && + kdelegate) { + mCb.NoteWeakMapping(aMap, aKey, kdelegate, nullptr); + } + } +} + +// Report whether the key or value of a weak mapping entry are gray but need to +// be marked black. +static void ShouldWeakMappingEntryBeBlack(JSObject* aMap, JS::GCCellPtr aKey, + JS::GCCellPtr aValue, + bool* aKeyShouldBeBlack, + bool* aValueShouldBeBlack) { + *aKeyShouldBeBlack = false; + *aValueShouldBeBlack = false; + + // If nothing that could be held alive by this entry is marked gray, return. + bool keyMightNeedMarking = aKey && JS::GCThingIsMarkedGrayInCC(aKey); + bool valueMightNeedMarking = aValue && JS::GCThingIsMarkedGrayInCC(aValue) && + aValue.kind() != JS::TraceKind::String; + if (!keyMightNeedMarking && !valueMightNeedMarking) { + return; + } + + if (!JS::IsCCTraceKind(aKey.kind())) { + aKey = nullptr; + } + + if (keyMightNeedMarking && aKey.is<JSObject>()) { + JSObject* kdelegate = + js::UncheckedUnwrapWithoutExpose(&aKey.as<JSObject>()); + if (kdelegate && !JS::ObjectIsMarkedGray(kdelegate) && + (!aMap || !JS::ObjectIsMarkedGray(aMap))) { + *aKeyShouldBeBlack = true; + } + } + + if (aValue && JS::GCThingIsMarkedGrayInCC(aValue) && + (!aKey || !JS::GCThingIsMarkedGrayInCC(aKey)) && + (!aMap || !JS::ObjectIsMarkedGray(aMap)) && + aValue.kind() != JS::TraceKind::Shape) { + *aValueShouldBeBlack = true; + } +} + +struct FixWeakMappingGrayBitsTracer : public js::WeakMapTracer { + explicit FixWeakMappingGrayBitsTracer(JSRuntime* aRt) + : js::WeakMapTracer(aRt) {} + + void FixAll() { + do { + mAnyMarked = false; + js::TraceWeakMaps(this); + } while (mAnyMarked); + } + + void trace(JSObject* aMap, JS::GCCellPtr aKey, + JS::GCCellPtr aValue) override { + bool keyShouldBeBlack; + bool valueShouldBeBlack; + ShouldWeakMappingEntryBeBlack(aMap, aKey, aValue, &keyShouldBeBlack, + &valueShouldBeBlack); + if (keyShouldBeBlack && JS::UnmarkGrayGCThingRecursively(aKey)) { + mAnyMarked = true; + } + + if (valueShouldBeBlack && JS::UnmarkGrayGCThingRecursively(aValue)) { + mAnyMarked = true; + } + } + + MOZ_INIT_OUTSIDE_CTOR bool mAnyMarked; +}; + +#ifdef DEBUG +// Check whether weak maps are marked correctly according to the logic above. +struct CheckWeakMappingGrayBitsTracer : public js::WeakMapTracer { + explicit CheckWeakMappingGrayBitsTracer(JSRuntime* aRt) + : js::WeakMapTracer(aRt), mFailed(false) {} + + static bool Check(JSRuntime* aRt) { + CheckWeakMappingGrayBitsTracer tracer(aRt); + js::TraceWeakMaps(&tracer); + return !tracer.mFailed; + } + + void trace(JSObject* aMap, JS::GCCellPtr aKey, + JS::GCCellPtr aValue) override { + bool keyShouldBeBlack; + bool valueShouldBeBlack; + ShouldWeakMappingEntryBeBlack(aMap, aKey, aValue, &keyShouldBeBlack, + &valueShouldBeBlack); + + if (keyShouldBeBlack) { + fprintf(stderr, "Weak mapping key %p of map %p should be black\n", + aKey.asCell(), aMap); + mFailed = true; + } + + if (valueShouldBeBlack) { + fprintf(stderr, "Weak mapping value %p of map %p should be black\n", + aValue.asCell(), aMap); + mFailed = true; + } + } + + bool mFailed; +}; +#endif // DEBUG + +static void CheckParticipatesInCycleCollection(JS::GCCellPtr aThing, + const char* aName, + void* aClosure) { + bool* cycleCollectionEnabled = static_cast<bool*>(aClosure); + + if (*cycleCollectionEnabled) { + return; + } + + if (JS::IsCCTraceKind(aThing.kind()) && JS::GCThingIsMarkedGrayInCC(aThing)) { + *cycleCollectionEnabled = true; + } +} + +NS_IMETHODIMP +JSGCThingParticipant::TraverseNative(void* aPtr, + nsCycleCollectionTraversalCallback& aCb) { + auto runtime = reinterpret_cast<CycleCollectedJSRuntime*>( + reinterpret_cast<char*>(this) - + offsetof(CycleCollectedJSRuntime, mGCThingCycleCollectorGlobal)); + + JS::GCCellPtr cellPtr(aPtr, JS::GCThingTraceKind(aPtr)); + runtime->TraverseGCThing(CycleCollectedJSRuntime::TRAVERSE_FULL, cellPtr, + aCb); + return NS_OK; +} + +// NB: This is only used to initialize the participant in +// CycleCollectedJSRuntime. It should never be used directly. +static JSGCThingParticipant sGCThingCycleCollectorGlobal; + +NS_IMETHODIMP +JSZoneParticipant::TraverseNative(void* aPtr, + nsCycleCollectionTraversalCallback& aCb) { + auto runtime = reinterpret_cast<CycleCollectedJSRuntime*>( + reinterpret_cast<char*>(this) - + offsetof(CycleCollectedJSRuntime, mJSZoneCycleCollectorGlobal)); + + MOZ_ASSERT(!aCb.WantAllTraces()); + JS::Zone* zone = static_cast<JS::Zone*>(aPtr); + + runtime->TraverseZone(zone, aCb); + return NS_OK; +} + +struct TraversalTracer : public JS::CallbackTracer { + TraversalTracer(JSRuntime* aRt, nsCycleCollectionTraversalCallback& aCb) + : JS::CallbackTracer(aRt, JS::TracerKind::Callback, + JS::TraceOptions(JS::WeakMapTraceAction::Skip, + JS::WeakEdgeTraceAction::Trace)), + mCb(aCb) {} + void onChild(JS::GCCellPtr aThing, const char* name) override; + nsCycleCollectionTraversalCallback& mCb; +}; + +void TraversalTracer::onChild(JS::GCCellPtr aThing, const char* name) { + // Checking strings and symbols for being gray is rather slow, and we don't + // need either of them for the cycle collector. + if (aThing.is<JSString>() || aThing.is<JS::Symbol>()) { + return; + } + + // Don't traverse non-gray objects, unless we want all traces. + if (!JS::GCThingIsMarkedGrayInCC(aThing) && !mCb.WantAllTraces()) { + return; + } + + /* + * This function needs to be careful to avoid stack overflow. Normally, when + * IsCCTraceKind is true, the recursion terminates immediately as we just add + * |thing| to the CC graph. So overflow is only possible when there are long + * or cyclic chains of non-IsCCTraceKind GC things. Places where this can + * occur use special APIs to handle such chains iteratively. + */ + if (JS::IsCCTraceKind(aThing.kind())) { + if (MOZ_UNLIKELY(mCb.WantDebugInfo())) { + char buffer[200]; + context().getEdgeName(name, buffer, sizeof(buffer)); + mCb.NoteNextEdgeName(buffer); + } + mCb.NoteJSChild(aThing); + return; + } + + // Allow re-use of this tracer inside trace callback. + JS::AutoClearTracingContext actc(this); + + if (aThing.is<js::Shape>()) { + // The maximum depth of traversal when tracing a Shape is unbounded, due to + // the parent pointers on the shape. + JS_TraceShapeCycleCollectorChildren(this, aThing); + } else { + JS::TraceChildren(this, aThing); + } +} + +/* + * The cycle collection participant for a Zone is intended to produce the same + * results as if all of the gray GCthings in a zone were merged into a single + * node, except for self-edges. This avoids the overhead of representing all of + * the GCthings in the zone in the cycle collector graph, which should be much + * faster if many of the GCthings in the zone are gray. + * + * Zone merging should not always be used, because it is a conservative + * approximation of the true cycle collector graph that can incorrectly identify + * some garbage objects as being live. For instance, consider two cycles that + * pass through a zone, where one is garbage and the other is live. If we merge + * the entire zone, the cycle collector will think that both are alive. + * + * We don't have to worry about losing track of a garbage cycle, because any + * such garbage cycle incorrectly identified as live must contain at least one + * C++ to JS edge, and XPConnect will always add the C++ object to the CC graph. + * (This is in contrast to pure C++ garbage cycles, which must always be + * properly identified, because we clear the purple buffer during every CC, + * which may contain the last reference to a garbage cycle.) + */ + +// NB: This is only used to initialize the participant in +// CycleCollectedJSRuntime. It should never be used directly. +static const JSZoneParticipant sJSZoneCycleCollectorGlobal; + +static void JSObjectsTenuredCb(JSContext* aContext, void* aData) { + static_cast<CycleCollectedJSRuntime*>(aData)->JSObjectsTenured(); +} + +static void MozCrashWarningReporter(JSContext*, JSErrorReport*) { + MOZ_CRASH("Why is someone touching JSAPI without an AutoJSAPI?"); +} + +JSHolderMap::Entry::Entry() : Entry(nullptr, nullptr, nullptr) {} + +JSHolderMap::Entry::Entry(void* aHolder, nsScriptObjectTracer* aTracer, + JS::Zone* aZone) + : mHolder(aHolder), + mTracer(aTracer) +#ifdef DEBUG + , + mZone(aZone) +#endif +{ +} + +void JSHolderMap::EntryVectorIter::Settle() { + if (Done()) { + return; + } + + Entry* entry = &mIter.Get(); + + // If the entry has been cleared, remove it and shrink the vector. + if (!entry->mHolder && !mHolderMap.RemoveEntry(mVector, entry)) { + // We removed the last entry, so reset the iterator to an empty one. + mIter = EntryVector().Iter(); + MOZ_ASSERT(Done()); + } +} + +JSHolderMap::Iter::Iter(JSHolderMap& aMap, WhichHolders aWhich) + : mHolderMap(aMap), mIter(aMap, aMap.mAnyZoneJSHolders) { + MOZ_RELEASE_ASSERT(!mHolderMap.mHasIterator); + mHolderMap.mHasIterator = true; + + // Populate vector of zones to iterate after the any-zone holders. + for (auto i = aMap.mPerZoneJSHolders.iter(); !i.done(); i.next()) { + JS::Zone* zone = i.get().key(); + if (aWhich == AllHolders || JS::NeedGrayRootsForZone(i.get().key())) { + MOZ_ALWAYS_TRUE(mZones.append(zone)); + } + } + + Settle(); +} + +void JSHolderMap::Iter::Settle() { + while (mIter.Done()) { + if (mZone && mIter.Vector().IsEmpty()) { + mHolderMap.mPerZoneJSHolders.remove(mZone); + } + + mZone = nullptr; + if (mZones.empty()) { + break; + } + + mZone = mZones.popCopy(); + EntryVector& vector = *mHolderMap.mPerZoneJSHolders.lookup(mZone)->value(); + new (&mIter) EntryVectorIter(mHolderMap, vector); + } +} + +void JSHolderMap::Iter::UpdateForRemovals() { + mIter.Settle(); + Settle(); +} + +JSHolderMap::JSHolderMap() : mJSHolderMap(256) {} + +bool JSHolderMap::RemoveEntry(EntryVector& aJSHolders, Entry* aEntry) { + MOZ_ASSERT(aEntry); + MOZ_ASSERT(!aEntry->mHolder); + + // Remove all dead entries from the end of the vector. + while (!aJSHolders.GetLast().mHolder && &aJSHolders.GetLast() != aEntry) { + aJSHolders.PopLast(); + } + + // Swap the element we want to remove with the last one and update the hash + // table. + Entry* lastEntry = &aJSHolders.GetLast(); + if (aEntry != lastEntry) { + MOZ_ASSERT(lastEntry->mHolder); + *aEntry = *lastEntry; + MOZ_ASSERT(mJSHolderMap.has(aEntry->mHolder)); + MOZ_ALWAYS_TRUE(mJSHolderMap.put(aEntry->mHolder, aEntry)); + } + + aJSHolders.PopLast(); + + // Return whether aEntry is still in the vector. + return aEntry != lastEntry; +} + +bool JSHolderMap::Has(void* aHolder) const { return mJSHolderMap.has(aHolder); } + +nsScriptObjectTracer* JSHolderMap::Get(void* aHolder) const { + auto ptr = mJSHolderMap.lookup(aHolder); + if (!ptr) { + return nullptr; + } + + Entry* entry = ptr->value(); + MOZ_ASSERT(entry->mHolder == aHolder); + return entry->mTracer; +} + +nsScriptObjectTracer* JSHolderMap::Extract(void* aHolder) { + MOZ_ASSERT(aHolder); + + auto ptr = mJSHolderMap.lookup(aHolder); + if (!ptr) { + return nullptr; + } + + Entry* entry = ptr->value(); + MOZ_ASSERT(entry->mHolder == aHolder); + nsScriptObjectTracer* tracer = entry->mTracer; + + // Clear the entry's contents. It will be removed the next time iteration + // visits this entry. + *entry = Entry(); + + mJSHolderMap.remove(ptr); + + return tracer; +} + +void JSHolderMap::Put(void* aHolder, nsScriptObjectTracer* aTracer, + JS::Zone* aZone) { + MOZ_ASSERT(aHolder); + MOZ_ASSERT(aTracer); + + // Don't associate multi-zone holders with a zone, even if one is supplied. + if (!aTracer->IsSingleZoneJSHolder()) { + aZone = nullptr; + } + + auto ptr = mJSHolderMap.lookupForAdd(aHolder); + if (ptr) { + Entry* entry = ptr->value(); +#ifdef DEBUG + MOZ_ASSERT(entry->mHolder == aHolder); + MOZ_ASSERT(entry->mTracer == aTracer, + "Don't call HoldJSObjects in superclass ctors"); + if (aZone) { + if (entry->mZone) { + MOZ_ASSERT(entry->mZone == aZone); + } else { + entry->mZone = aZone; + } + } +#endif + entry->mTracer = aTracer; + return; + } + + EntryVector* vector = &mAnyZoneJSHolders; + if (aZone) { + auto ptr = mPerZoneJSHolders.lookupForAdd(aZone); + if (!ptr) { + MOZ_ALWAYS_TRUE( + mPerZoneJSHolders.add(ptr, aZone, MakeUnique<EntryVector>())); + } + vector = ptr->value().get(); + } + + vector->InfallibleAppend(Entry{aHolder, aTracer, aZone}); + MOZ_ALWAYS_TRUE(mJSHolderMap.add(ptr, aHolder, &vector->GetLast())); +} + +size_t JSHolderMap::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const { + size_t n = 0; + + // We're deliberately not measuring anything hanging off the entries in + // mJSHolders. + n += mJSHolderMap.shallowSizeOfExcludingThis(aMallocSizeOf); + n += mAnyZoneJSHolders.SizeOfExcludingThis(aMallocSizeOf); + n += mPerZoneJSHolders.shallowSizeOfExcludingThis(aMallocSizeOf); + for (auto i = mPerZoneJSHolders.iter(); !i.done(); i.next()) { + n += i.get().value()->SizeOfExcludingThis(aMallocSizeOf); + } + + return n; +} + +static bool InitializeShadowRealm(JSContext* aCx, + JS::Handle<JSObject*> aGlobal) { + MOZ_ASSERT(StaticPrefs::javascript_options_experimental_shadow_realms()); + + JSAutoRealm ar(aCx, aGlobal); + return dom::RegisterShadowRealmBindings(aCx, aGlobal); +} + +CycleCollectedJSRuntime::CycleCollectedJSRuntime(JSContext* aCx) + : mContext(nullptr), + mGCThingCycleCollectorGlobal(sGCThingCycleCollectorGlobal), + mJSZoneCycleCollectorGlobal(sJSZoneCycleCollectorGlobal), + mJSRuntime(JS_GetRuntime(aCx)), + mHasPendingIdleGCTask(false), + mPrevGCSliceCallback(nullptr), + mOutOfMemoryState(OOMState::OK), + mLargeAllocationFailureState(OOMState::OK) +#ifdef DEBUG + , + mShutdownCalled(false) +#endif +{ + MOZ_COUNT_CTOR(CycleCollectedJSRuntime); + MOZ_ASSERT(aCx); + MOZ_ASSERT(mJSRuntime); + +#if defined(XP_MACOSX) + if (!XRE_IsParentProcess()) { + nsMacUtilsImpl::EnableTCSMIfAvailable(); + } +#endif + + if (!JS_AddExtraGCRootsTracer(aCx, TraceBlackJS, this)) { + MOZ_CRASH("JS_AddExtraGCRootsTracer failed"); + } + JS_SetGrayGCRootsTracer(aCx, TraceGrayJS, this); + JS_SetGCCallback(aCx, GCCallback, this); + mPrevGCSliceCallback = JS::SetGCSliceCallback(aCx, GCSliceCallback); + + if (NS_IsMainThread()) { + // We would like to support all threads here, but the way timeline consumers + // are set up currently, you can either add a marker for one specific + // docshell, or for every consumer globally. We would like to add a marker + // for every consumer observing anything on this thread, but that is not + // currently possible. For now, add global markers only when we are on the + // main thread, since the UI for this tracing data only displays data + // relevant to the main-thread. + JS::AddGCNurseryCollectionCallback(aCx, GCNurseryCollectionCallback, + nullptr); + } + + JS_SetObjectsTenuredCallback(aCx, JSObjectsTenuredCb, this); + JS::SetOutOfMemoryCallback(aCx, OutOfMemoryCallback, this); + JS::SetWaitCallback(mJSRuntime, BeforeWaitCallback, AfterWaitCallback, + sizeof(dom::AutoYieldJSThreadExecution)); + JS::SetWarningReporter(aCx, MozCrashWarningReporter); + JS::SetShadowRealmInitializeGlobalCallback(aCx, InitializeShadowRealm); + JS::SetShadowRealmGlobalCreationCallback(aCx, dom::NewShadowRealmGlobal); + + js::AutoEnterOOMUnsafeRegion::setAnnotateOOMAllocationSizeCallback( + CrashReporter::AnnotateOOMAllocationSize); + + static js::DOMCallbacks DOMcallbacks = {InstanceClassHasProtoAtDepth}; + SetDOMCallbacks(aCx, &DOMcallbacks); + js::SetScriptEnvironmentPreparer(aCx, &mEnvironmentPreparer); + + JS::dbg::SetDebuggerMallocSizeOf(aCx, moz_malloc_size_of); + +#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR + JS_SetErrorInterceptorCallback(mJSRuntime, &mErrorInterceptor); +#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR + + JS_SetDestroyZoneCallback(aCx, OnZoneDestroyed); +} + +#ifdef NS_BUILD_REFCNT_LOGGING +class JSLeakTracer : public JS::CallbackTracer { + public: + explicit JSLeakTracer(JSRuntime* aRuntime) + : JS::CallbackTracer(aRuntime, JS::TracerKind::Callback, + JS::WeakMapTraceAction::TraceKeysAndValues) {} + + private: + void onChild(JS::GCCellPtr thing, const char* name) override { + const char* kindName = JS::GCTraceKindToAscii(thing.kind()); + size_t size = JS::GCTraceKindSize(thing.kind()); + MOZ_LOG_CTOR(thing.asCell(), kindName, size); + } +}; +#endif + +void CycleCollectedJSRuntime::Shutdown(JSContext* aCx) { +#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR + mErrorInterceptor.Shutdown(mJSRuntime); +#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR + + // There should not be any roots left to trace at this point. Ensure any that + // remain are flagged as leaks. +#ifdef NS_BUILD_REFCNT_LOGGING + JSLeakTracer tracer(Runtime()); + TraceNativeBlackRoots(&tracer); + TraceAllNativeGrayRoots(&tracer); +#endif + +#ifdef DEBUG + mShutdownCalled = true; +#endif + + JS_SetDestroyZoneCallback(aCx, nullptr); + + if (NS_IsMainThread()) { + JS::RemoveGCNurseryCollectionCallback(aCx, GCNurseryCollectionCallback, + nullptr); + } +} + +CycleCollectedJSRuntime::~CycleCollectedJSRuntime() { + MOZ_COUNT_DTOR(CycleCollectedJSRuntime); + MOZ_ASSERT(!mDeferredFinalizerTable.Count()); + MOZ_ASSERT(!mFinalizeRunnable); + MOZ_ASSERT(mShutdownCalled); +} + +void CycleCollectedJSRuntime::SetContext(CycleCollectedJSContext* aContext) { + MOZ_ASSERT(!mContext || !aContext, "Don't replace the context!"); + mContext = aContext; +} + +size_t CycleCollectedJSRuntime::SizeOfExcludingThis( + MallocSizeOf aMallocSizeOf) const { + return mJSHolders.SizeOfExcludingThis(aMallocSizeOf); +} + +void CycleCollectedJSRuntime::UnmarkSkippableJSHolders() { + for (JSHolderMap::Iter entry(mJSHolders); !entry.Done(); entry.Next()) { + entry->mTracer->CanSkip(entry->mHolder, true); + } +} + +void CycleCollectedJSRuntime::DescribeGCThing( + bool aIsMarked, JS::GCCellPtr aThing, + nsCycleCollectionTraversalCallback& aCb) const { + if (!aCb.WantDebugInfo()) { + aCb.DescribeGCedNode(aIsMarked, "JS Object"); + return; + } + + char name[72]; + uint64_t compartmentAddress = 0; + if (aThing.is<JSObject>()) { + JSObject* obj = &aThing.as<JSObject>(); + compartmentAddress = (uint64_t)JS::GetCompartment(obj); + const JSClass* clasp = JS::GetClass(obj); + + // Give the subclass a chance to do something + if (DescribeCustomObjects(obj, clasp, name)) { + // Nothing else to do! + } else if (js::IsFunctionObject(obj)) { + JSFunction* fun = JS_GetObjectFunction(obj); + JSString* str = JS_GetMaybePartialFunctionDisplayId(fun); + if (str) { + JSLinearString* linear = JS_ASSERT_STRING_IS_LINEAR(str); + nsAutoString chars; + AssignJSLinearString(chars, linear); + NS_ConvertUTF16toUTF8 fname(chars); + SprintfLiteral(name, "JS Object (Function - %s)", fname.get()); + } else { + SprintfLiteral(name, "JS Object (Function)"); + } + } else { + SprintfLiteral(name, "JS Object (%s)", clasp->name); + } + } else { + SprintfLiteral(name, "%s", JS::GCTraceKindToAscii(aThing.kind())); + } + + // Disable printing global for objects while we figure out ObjShrink fallout. + aCb.DescribeGCedNode(aIsMarked, name, compartmentAddress); +} + +void CycleCollectedJSRuntime::NoteGCThingJSChildren( + JS::GCCellPtr aThing, nsCycleCollectionTraversalCallback& aCb) const { + TraversalTracer trc(mJSRuntime, aCb); + JS::TraceChildren(&trc, aThing); +} + +void CycleCollectedJSRuntime::NoteGCThingXPCOMChildren( + const JSClass* aClasp, JSObject* aObj, + nsCycleCollectionTraversalCallback& aCb) const { + MOZ_ASSERT(aClasp); + MOZ_ASSERT(aClasp == JS::GetClass(aObj)); + + JS::Rooted<JSObject*> obj(RootingCx(), aObj); + + if (NoteCustomGCThingXPCOMChildren(aClasp, obj, aCb)) { + // Nothing else to do! + return; + } + + // XXX This test does seem fragile, we should probably allowlist classes + // that do hold a strong reference, but that might not be possible. + if (aClasp->slot0IsISupports()) { + NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "JS::GetObjectISupports(obj)"); + aCb.NoteXPCOMChild(JS::GetObjectISupports<nsISupports>(obj)); + return; + } + + const DOMJSClass* domClass = GetDOMClass(aClasp); + if (domClass) { + NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "UnwrapDOMObject(obj)"); + // It's possible that our object is an unforgeable holder object, in + // which case it doesn't actually have a C++ DOM object associated with + // it. Use UnwrapPossiblyNotInitializedDOMObject, which produces null in + // that case, since NoteXPCOMChild/NoteNativeChild are null-safe. + if (domClass->mDOMObjectIsISupports) { + aCb.NoteXPCOMChild( + UnwrapPossiblyNotInitializedDOMObject<nsISupports>(obj)); + } else if (domClass->mParticipant) { + aCb.NoteNativeChild(UnwrapPossiblyNotInitializedDOMObject<void>(obj), + domClass->mParticipant); + } + return; + } + + if (IsRemoteObjectProxy(obj)) { + auto handler = + static_cast<const RemoteObjectProxyBase*>(js::GetProxyHandler(obj)); + return handler->NoteChildren(obj, aCb); + } + + JS::Value value = js::MaybeGetScriptPrivate(obj); + if (!value.isUndefined()) { + aCb.NoteXPCOMChild(static_cast<nsISupports*>(value.toPrivate())); + } +} + +void CycleCollectedJSRuntime::TraverseGCThing( + TraverseSelect aTs, JS::GCCellPtr aThing, + nsCycleCollectionTraversalCallback& aCb) { + bool isMarkedGray = JS::GCThingIsMarkedGrayInCC(aThing); + + if (aTs == TRAVERSE_FULL) { + DescribeGCThing(!isMarkedGray, aThing, aCb); + } + + // If this object is alive, then all of its children are alive. For JS + // objects, the black-gray invariant ensures the children are also marked + // black. For C++ objects, the ref count from this object will keep them + // alive. Thus we don't need to trace our children, unless we are debugging + // using WantAllTraces. + if (!isMarkedGray && !aCb.WantAllTraces()) { + return; + } + + if (aTs == TRAVERSE_FULL) { + NoteGCThingJSChildren(aThing, aCb); + } + + if (aThing.is<JSObject>()) { + JSObject* obj = &aThing.as<JSObject>(); + NoteGCThingXPCOMChildren(JS::GetClass(obj), obj, aCb); + } +} + +struct TraverseObjectShimClosure { + nsCycleCollectionTraversalCallback& cb; + CycleCollectedJSRuntime* self; +}; + +void CycleCollectedJSRuntime::TraverseZone( + JS::Zone* aZone, nsCycleCollectionTraversalCallback& aCb) { + /* + * We treat the zone as being gray. We handle non-gray GCthings in the + * zone by not reporting their children to the CC. The black-gray invariant + * ensures that any JS children will also be non-gray, and thus don't need to + * be added to the graph. For C++ children, not representing the edge from the + * non-gray JS GCthings to the C++ object will keep the child alive. + * + * We don't allow zone merging in a WantAllTraces CC, because then these + * assumptions don't hold. + */ + aCb.DescribeGCedNode(false, "JS Zone"); + + /* + * Every JS child of everything in the zone is either in the zone + * or is a cross-compartment wrapper. In the former case, we don't need to + * represent these edges in the CC graph because JS objects are not ref + * counted. In the latter case, the JS engine keeps a map of these wrappers, + * which we iterate over. Edges between compartments in the same zone will add + * unnecessary loop edges to the graph (bug 842137). + */ + TraversalTracer trc(mJSRuntime, aCb); + js::TraceGrayWrapperTargets(&trc, aZone); + + /* + * To find C++ children of things in the zone, we scan every JS Object in + * the zone. Only JS Objects can have C++ children. + */ + TraverseObjectShimClosure closure = {aCb, this}; + js::IterateGrayObjects(aZone, TraverseObjectShim, &closure); +} + +/* static */ +void CycleCollectedJSRuntime::TraverseObjectShim( + void* aData, JS::GCCellPtr aThing, const JS::AutoRequireNoGC& nogc) { + TraverseObjectShimClosure* closure = + static_cast<TraverseObjectShimClosure*>(aData); + + MOZ_ASSERT(aThing.is<JSObject>()); + closure->self->TraverseGCThing(CycleCollectedJSRuntime::TRAVERSE_CPP, aThing, + closure->cb); +} + +void CycleCollectedJSRuntime::TraverseNativeRoots( + nsCycleCollectionNoteRootCallback& aCb) { + // NB: This is here just to preserve the existing XPConnect order. I doubt it + // would hurt to do this after the JS holders. + TraverseAdditionalNativeRoots(aCb); + + for (JSHolderMap::Iter entry(mJSHolders); !entry.Done(); entry.Next()) { + void* holder = entry->mHolder; + nsScriptObjectTracer* tracer = entry->mTracer; + + bool noteRoot = false; + if (MOZ_UNLIKELY(aCb.WantAllTraces())) { + noteRoot = true; + } else { + tracer->Trace(holder, + TraceCallbackFunc(CheckParticipatesInCycleCollection), + ¬eRoot); + } + + if (noteRoot) { + aCb.NoteNativeRoot(holder, tracer); + } + } +} + +/* static */ +void CycleCollectedJSRuntime::TraceBlackJS(JSTracer* aTracer, void* aData) { + CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData); + + self->TraceNativeBlackRoots(aTracer); +} + +/* static */ +bool CycleCollectedJSRuntime::TraceGrayJS(JSTracer* aTracer, + js::SliceBudget& budget, + void* aData) { + CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData); + + // Mark these roots as gray so the CC can walk them later. + + JSHolderMap::WhichHolders which = JSHolderMap::AllHolders; + + // Only trace holders in collecting zones when marking, except if we are + // collecting the atoms zone since any holder may point into that zone. + if (aTracer->isMarkingTracer() && + !JS::AtomsZoneIsCollecting(self->Runtime())) { + which = JSHolderMap::HoldersRequiredForGrayMarking; + } + + return self->TraceNativeGrayRoots(aTracer, which, budget); +} + +/* static */ +void CycleCollectedJSRuntime::GCCallback(JSContext* aContext, + JSGCStatus aStatus, + JS::GCReason aReason, void* aData) { + CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData); + + MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext); + MOZ_ASSERT(CycleCollectedJSContext::Get()->Runtime() == self); + + self->OnGC(aContext, aStatus, aReason); +} + +struct GCMajorMarker : public BaseMarkerType<GCMajorMarker> { + static constexpr const char* Name = "GCMajor"; + static constexpr const char* Description = + "Summary data for an entire major GC, encompassing a set of " + "incremental slices. The main thread is not blocked for the " + "entire major GC interval, only for the individual slices."; + + using MS = MarkerSchema; + static constexpr MS::PayloadField PayloadFields[] = { + {"timings", MS::InputType::String, "GC timings"}}; + + static constexpr MS::Location Locations[] = {MS::Location::MarkerChart, + MS::Location::MarkerTable, + MS::Location::TimelineMemory}; + static constexpr MS::ETWMarkerGroup Group = MS::ETWMarkerGroup::Memory; + + static void StreamJSONMarkerData( + mozilla::baseprofiler::SpliceableJSONWriter& aWriter, + const mozilla::ProfilerString8View& aTimingJSON) { + if (aTimingJSON.Length() != 0) { + aWriter.SplicedJSONProperty("timings", aTimingJSON); + } else { + aWriter.NullProperty("timings"); + } + } +}; + +/* static */ +void CycleCollectedJSRuntime::GCSliceCallback(JSContext* aContext, + JS::GCProgress aProgress, + const JS::GCDescription& aDesc) { + CycleCollectedJSRuntime* self = CycleCollectedJSRuntime::Get(); + MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext); + + if (profiler_thread_is_being_profiled_for_markers()) { + if (aProgress == JS::GC_CYCLE_END) { + profiler_add_marker("GCMajor", baseprofiler::category::GCCC, + MarkerTiming::Interval(aDesc.startTime(aContext), + aDesc.endTime(aContext)), + GCMajorMarker{}, + ProfilerString8View::WrapNullTerminatedString( + aDesc.formatJSONProfiler(aContext).get())); + } else if (aProgress == JS::GC_SLICE_END) { + struct GCSliceMarker { + static constexpr mozilla::Span<const char> MarkerTypeName() { + return mozilla::MakeStringSpan("GCSlice"); + } + static void StreamJSONMarkerData( + mozilla::baseprofiler::SpliceableJSONWriter& aWriter, + const mozilla::ProfilerString8View& aTimingJSON) { + if (aTimingJSON.Length() != 0) { + aWriter.SplicedJSONProperty("timings", aTimingJSON); + } else { + aWriter.NullProperty("timings"); + } + } + static mozilla::MarkerSchema MarkerTypeDisplay() { + using MS = mozilla::MarkerSchema; + MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable, + MS::Location::TimelineMemory}; + schema.AddStaticLabelValue( + "Description", + "One slice of an incremental garbage collection (GC). The main " + "thread is blocked during this time."); + // No display instructions here, there is special handling in the + // front-end. + return schema; + } + }; + + profiler_add_marker("GCSlice", baseprofiler::category::GCCC, + MarkerTiming::Interval(aDesc.lastSliceStart(aContext), + aDesc.lastSliceEnd(aContext)), + GCSliceMarker{}, + ProfilerString8View::WrapNullTerminatedString( + aDesc.sliceToJSONProfiler(aContext).get())); + } + } + + if (aProgress == JS::GC_CYCLE_END && + JS::dbg::FireOnGarbageCollectionHookRequired(aContext)) { + JS::GCReason reason = aDesc.reason_; + Unused << NS_WARN_IF( + NS_FAILED(DebuggerOnGCRunnable::Enqueue(aContext, aDesc)) && + reason != JS::GCReason::SHUTDOWN_CC && + reason != JS::GCReason::DESTROY_RUNTIME && + reason != JS::GCReason::XPCONNECT_SHUTDOWN); + } + + if (self->mPrevGCSliceCallback) { + self->mPrevGCSliceCallback(aContext, aProgress, aDesc); + } +} + +/* static */ +void CycleCollectedJSRuntime::GCNurseryCollectionCallback( + JSContext* aContext, JS::GCNurseryProgress aProgress, JS::GCReason aReason, + void* data) { + CycleCollectedJSRuntime* self = CycleCollectedJSRuntime::Get(); + MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext); + MOZ_ASSERT(NS_IsMainThread()); + + TimeStamp now = TimeStamp::Now(); + if (aProgress == JS::GCNurseryProgress::GC_NURSERY_COLLECTION_START) { + self->mLatestNurseryCollectionStart = now; + } else if (aProgress == JS::GCNurseryProgress::GC_NURSERY_COLLECTION_END) { + PerfStats::RecordMeasurement(PerfStats::Metric::MinorGC, + now - self->mLatestNurseryCollectionStart); + } + + if (aProgress == JS::GCNurseryProgress::GC_NURSERY_COLLECTION_END && + profiler_thread_is_being_profiled_for_markers()) { + struct GCMinorMarker { + static constexpr mozilla::Span<const char> MarkerTypeName() { + return mozilla::MakeStringSpan("GCMinor"); + } + static void StreamJSONMarkerData( + mozilla::baseprofiler::SpliceableJSONWriter& aWriter, + const mozilla::ProfilerString8View& aTimingJSON) { + if (aTimingJSON.Length() != 0) { + aWriter.SplicedJSONProperty("nursery", aTimingJSON); + } else { + aWriter.NullProperty("nursery"); + } + } + static mozilla::MarkerSchema MarkerTypeDisplay() { + using MS = mozilla::MarkerSchema; + MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable, + MS::Location::TimelineMemory}; + schema.AddStaticLabelValue( + "Description", + "A minor GC (aka nursery collection) to clear out the buffer used " + "for recent allocations and move surviving data to the tenured " + "(long-lived) heap."); + // No display instructions here, there is special handling in the + // front-end. + return schema; + } + }; + + profiler_add_marker( + "GCMinor", baseprofiler::category::GCCC, + MarkerTiming::Interval(self->mLatestNurseryCollectionStart, now), + GCMinorMarker{}, + ProfilerString8View::WrapNullTerminatedString( + JS::MinorGcToJSON(aContext).get())); + } +} + +/* static */ +void CycleCollectedJSRuntime::OutOfMemoryCallback(JSContext* aContext, + void* aData) { + CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData); + + MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext); + MOZ_ASSERT(CycleCollectedJSContext::Get()->Runtime() == self); + + self->OnOutOfMemory(); +} + +/* static */ +void* CycleCollectedJSRuntime::BeforeWaitCallback(uint8_t* aMemory) { + MOZ_ASSERT(aMemory); + + // aMemory is stack allocated memory to contain our RAII object. This allows + // for us to avoid allocations on the heap during this callback. + return new (aMemory) dom::AutoYieldJSThreadExecution; +} + +/* static */ +void CycleCollectedJSRuntime::AfterWaitCallback(void* aCookie) { + MOZ_ASSERT(aCookie); + static_cast<dom::AutoYieldJSThreadExecution*>(aCookie) + ->~AutoYieldJSThreadExecution(); +} + +struct JsGcTracer : public TraceCallbacks { + virtual void Trace(JS::Heap<JS::Value>* aPtr, const char* aName, + void* aClosure) const override { + JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName); + } + virtual void Trace(JS::Heap<jsid>* aPtr, const char* aName, + void* aClosure) const override { + JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName); + } + virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName, + void* aClosure) const override { + JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName); + } + virtual void Trace(nsWrapperCache* aPtr, const char* aName, + void* aClosure) const override { + aPtr->TraceWrapper(static_cast<JSTracer*>(aClosure), aName); + } + virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName, + void* aClosure) const override { + JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName); + } + virtual void Trace(JS::Heap<JSString*>* aPtr, const char* aName, + void* aClosure) const override { + JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName); + } + virtual void Trace(JS::Heap<JSScript*>* aPtr, const char* aName, + void* aClosure) const override { + JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName); + } + virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char* aName, + void* aClosure) const override { + JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName); + } +}; + +void mozilla::TraceScriptHolder(nsISupports* aHolder, JSTracer* aTracer) { + nsXPCOMCycleCollectionParticipant* participant = nullptr; + CallQueryInterface(aHolder, &participant); + participant->Trace(aHolder, JsGcTracer(), aTracer); +} + +#if defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION) || defined(DEBUG) +# define CHECK_SINGLE_ZONE_JS_HOLDERS +#endif + +#ifdef CHECK_SINGLE_ZONE_JS_HOLDERS + +// A tracer that checks that a JS holder only holds JS GC things in a single +// JS::Zone. +struct CheckZoneTracer : public TraceCallbacks { + const char* mClassName; + mutable JS::Zone* mZone; + + explicit CheckZoneTracer(const char* aClassName, JS::Zone* aZone = nullptr) + : mClassName(aClassName), mZone(aZone) {} + + void checkZone(JS::Zone* aZone, const char* aName) const { + if (JS::IsAtomsZone(aZone)) { + // Any holder may contain pointers into the atoms zone. + return; + } + + if (!mZone) { + mZone = aZone; + return; + } + + if (aZone == mZone) { + return; + } + + // Most JS holders only contain pointers to GC things in a single zone. We + // group holders by referent zone where possible, allowing us to improve GC + // performance by only tracing holders for zones that are being collected. + // + // Additionally, pointers from any holder into the atoms zone are allowed + // since all holders are traced when we collect the atoms zone. + // + // If you added a holder that has pointers into multiple zones do not + // use NS_IMPL_CYCLE_COLLECTION_SINGLE_ZONE_SCRIPT_HOLDER_CLASS. + MOZ_CRASH_UNSAFE_PRINTF( + "JS holder %s contains pointers to GC things in more than one zone (" + "found in %s)\n", + mClassName, aName); + } + + virtual void Trace(JS::Heap<JS::Value>* aPtr, const char* aName, + void* aClosure) const override { + JS::Value value = aPtr->unbarrieredGet(); + if (value.isGCThing()) { + checkZone(JS::GetGCThingZone(value.toGCCellPtr()), aName); + } + } + virtual void Trace(JS::Heap<jsid>* aPtr, const char* aName, + void* aClosure) const override { + jsid id = aPtr->unbarrieredGet(); + if (id.isGCThing()) { + MOZ_ASSERT(JS::IsAtomsZone(JS::GetTenuredGCThingZone(id.toGCCellPtr()))); + } + } + virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName, + void* aClosure) const override { + JSObject* obj = aPtr->unbarrieredGet(); + if (obj) { + checkZone(js::GetObjectZoneFromAnyThread(obj), aName); + } + } + virtual void Trace(nsWrapperCache* aPtr, const char* aName, + void* aClosure) const override { + JSObject* obj = aPtr->GetWrapperPreserveColor(); + if (obj) { + checkZone(js::GetObjectZoneFromAnyThread(obj), aName); + } + } + virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName, + void* aClosure) const override { + JSObject* obj = aPtr->unbarrieredGetPtr(); + if (obj) { + checkZone(js::GetObjectZoneFromAnyThread(obj), aName); + } + } + virtual void Trace(JS::Heap<JSString*>* aPtr, const char* aName, + void* aClosure) const override { + JSString* str = aPtr->unbarrieredGet(); + if (str) { + checkZone(JS::GetStringZone(str), aName); + } + } + virtual void Trace(JS::Heap<JSScript*>* aPtr, const char* aName, + void* aClosure) const override { + JSScript* script = aPtr->unbarrieredGet(); + if (script) { + checkZone(JS::GetTenuredGCThingZone(JS::GCCellPtr(script)), aName); + } + } + virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char* aName, + void* aClosure) const override { + JSFunction* fun = aPtr->unbarrieredGet(); + if (fun) { + checkZone(js::GetObjectZoneFromAnyThread(JS_GetFunctionObject(fun)), + aName); + } + } +}; + +static inline void CheckHolderIsSingleZone( + void* aHolder, nsCycleCollectionParticipant* aParticipant, + JS::Zone* aZone) { + CheckZoneTracer tracer(aParticipant->ClassName(), aZone); + aParticipant->Trace(aHolder, tracer, nullptr); +} + +#endif + +static inline bool ShouldCheckSingleZoneHolders() { +#if defined(DEBUG) + return true; +#elif defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION) + // Don't check every time to avoid performance impact. + return rand() % 256 == 0; +#else + return false; +#endif +} + +#ifdef NS_BUILD_REFCNT_LOGGING +void CycleCollectedJSRuntime::TraceAllNativeGrayRoots(JSTracer* aTracer) { + MOZ_RELEASE_ASSERT(mHolderIter.isNothing()); + js::SliceBudget budget = js::SliceBudget::unlimited(); + MOZ_ALWAYS_TRUE( + TraceNativeGrayRoots(aTracer, JSHolderMap::AllHolders, budget)); +} +#endif + +bool CycleCollectedJSRuntime::TraceNativeGrayRoots( + JSTracer* aTracer, JSHolderMap::WhichHolders aWhich, + js::SliceBudget& aBudget) { + if (!mHolderIter) { + // NB: This is here just to preserve the existing XPConnect order. I doubt + // it would hurt to do this after the JS holders. + TraceAdditionalNativeGrayRoots(aTracer); + + mHolderIter.emplace(mJSHolders, aWhich); + aBudget.forceCheck(); + } else { + // Holders may have been removed between slices, so we may need to update + // the iterator. + mHolderIter->UpdateForRemovals(); + } + + bool finished = TraceJSHolders(aTracer, *mHolderIter, aBudget); + if (finished) { + mHolderIter.reset(); + } + + return finished; +} + +bool CycleCollectedJSRuntime::TraceJSHolders(JSTracer* aTracer, + JSHolderMap::Iter& aIter, + js::SliceBudget& aBudget) { + bool checkSingleZoneHolders = ShouldCheckSingleZoneHolders(); + + while (!aIter.Done() && !aBudget.isOverBudget()) { + void* holder = aIter->mHolder; + nsScriptObjectTracer* tracer = aIter->mTracer; + +#ifdef CHECK_SINGLE_ZONE_JS_HOLDERS + if (checkSingleZoneHolders && tracer->IsSingleZoneJSHolder()) { + CheckHolderIsSingleZone(holder, tracer, aIter.Zone()); + } +#else + Unused << checkSingleZoneHolders; +#endif + + tracer->Trace(holder, JsGcTracer(), aTracer); + + aIter.Next(); + aBudget.step(); + } + + return aIter.Done(); +} + +void CycleCollectedJSRuntime::AddJSHolder(void* aHolder, + nsScriptObjectTracer* aTracer, + JS::Zone* aZone) { + mJSHolders.Put(aHolder, aTracer, aZone); +} + +struct ClearJSHolder : public TraceCallbacks { + virtual void Trace(JS::Heap<JS::Value>* aPtr, const char*, + void*) const override { + aPtr->setUndefined(); + } + + virtual void Trace(JS::Heap<jsid>* aPtr, const char*, void*) const override { + *aPtr = JS::PropertyKey::Void(); + } + + virtual void Trace(JS::Heap<JSObject*>* aPtr, const char*, + void*) const override { + *aPtr = nullptr; + } + + virtual void Trace(nsWrapperCache* aPtr, const char* aName, + void* aClosure) const override { + aPtr->ClearWrapper(); + } + + virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char*, + void*) const override { + *aPtr = nullptr; + } + + virtual void Trace(JS::Heap<JSString*>* aPtr, const char*, + void*) const override { + *aPtr = nullptr; + } + + virtual void Trace(JS::Heap<JSScript*>* aPtr, const char*, + void*) const override { + *aPtr = nullptr; + } + + virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char*, + void*) const override { + *aPtr = nullptr; + } +}; + +void CycleCollectedJSRuntime::RemoveJSHolder(void* aHolder) { + nsScriptObjectTracer* tracer = mJSHolders.Extract(aHolder); + if (tracer) { + // Bug 1531951: The analysis can't see through the virtual call but we know + // that the ClearJSHolder tracer will never GC. + JS::AutoSuppressGCAnalysis nogc; + tracer->Trace(aHolder, ClearJSHolder(), nullptr); + } +} + +#ifdef DEBUG +static void AssertNoGcThing(JS::GCCellPtr aGCThing, const char* aName, + void* aClosure) { + MOZ_ASSERT(!aGCThing); +} + +void CycleCollectedJSRuntime::AssertNoObjectsToTrace(void* aPossibleJSHolder) { + nsScriptObjectTracer* tracer = mJSHolders.Get(aPossibleJSHolder); + if (tracer) { + tracer->Trace(aPossibleJSHolder, TraceCallbackFunc(AssertNoGcThing), + nullptr); + } +} +#endif + +nsCycleCollectionParticipant* CycleCollectedJSRuntime::GCThingParticipant() { + return &mGCThingCycleCollectorGlobal; +} + +nsCycleCollectionParticipant* CycleCollectedJSRuntime::ZoneParticipant() { + return &mJSZoneCycleCollectorGlobal; +} + +nsresult CycleCollectedJSRuntime::TraverseRoots( + nsCycleCollectionNoteRootCallback& aCb) { + TraverseNativeRoots(aCb); + + NoteWeakMapsTracer trc(mJSRuntime, aCb); + js::TraceWeakMaps(&trc); + + return NS_OK; +} + +bool CycleCollectedJSRuntime::UsefulToMergeZones() const { return false; } + +void CycleCollectedJSRuntime::FixWeakMappingGrayBits() const { + MOZ_ASSERT(!JS::IsIncrementalGCInProgress(mJSRuntime), + "Don't call FixWeakMappingGrayBits during a GC."); + FixWeakMappingGrayBitsTracer fixer(mJSRuntime); + fixer.FixAll(); +} + +void CycleCollectedJSRuntime::CheckGrayBits() const { + MOZ_ASSERT(!JS::IsIncrementalGCInProgress(mJSRuntime), + "Don't call CheckGrayBits during a GC."); + +#ifndef ANDROID + // Bug 1346874 - The gray state check is expensive. Android tests are already + // slow enough that this check can easily push them over the threshold to a + // timeout. + + MOZ_ASSERT(js::CheckGrayMarkingState(mJSRuntime)); + MOZ_ASSERT(CheckWeakMappingGrayBitsTracer::Check(mJSRuntime)); +#endif +} + +bool CycleCollectedJSRuntime::AreGCGrayBitsValid() const { + return js::AreGCGrayBitsValid(mJSRuntime); +} + +void CycleCollectedJSRuntime::GarbageCollect(JS::GCOptions aOptions, + JS::GCReason aReason) const { + JSContext* cx = CycleCollectedJSContext::Get()->Context(); + JS::PrepareForFullGC(cx); + JS::NonIncrementalGC(cx, aOptions, aReason); +} + +void CycleCollectedJSRuntime::JSObjectsTenured() { + JSContext* cx = CycleCollectedJSContext::Get()->Context(); + for (auto iter = mNurseryObjects.Iter(); !iter.Done(); iter.Next()) { + nsWrapperCache* cache = iter.Get(); + JSObject* wrapper = cache->GetWrapperMaybeDead(); + MOZ_DIAGNOSTIC_ASSERT(wrapper); + if (!JS::ObjectIsTenured(wrapper)) { + MOZ_ASSERT(!cache->PreservingWrapper()); + js::gc::FinalizeDeadNurseryObject(cx, wrapper); + } + } + + mNurseryObjects.Clear(); +} + +void CycleCollectedJSRuntime::NurseryWrapperAdded(nsWrapperCache* aCache) { + MOZ_ASSERT(aCache); + MOZ_ASSERT(aCache->GetWrapperMaybeDead()); + MOZ_ASSERT(!JS::ObjectIsTenured(aCache->GetWrapperMaybeDead())); + mNurseryObjects.InfallibleAppend(aCache); +} + +void CycleCollectedJSRuntime::DeferredFinalize( + DeferredFinalizeAppendFunction aAppendFunc, DeferredFinalizeFunction aFunc, + void* aThing) { + // Tell the analysis that the function pointers will not GC. + JS::AutoSuppressGCAnalysis suppress; + mDeferredFinalizerTable.WithEntryHandle(aFunc, [&](auto&& entry) { + if (entry) { + aAppendFunc(entry.Data(), aThing); + } else { + entry.Insert(aAppendFunc(nullptr, aThing)); + } + }); +} + +void CycleCollectedJSRuntime::DeferredFinalize(nsISupports* aSupports) { + typedef DeferredFinalizerImpl<nsISupports> Impl; + DeferredFinalize(Impl::AppendDeferredFinalizePointer, Impl::DeferredFinalize, + aSupports); +} + +void CycleCollectedJSRuntime::DumpJSHeap(FILE* aFile) { + JSContext* cx = CycleCollectedJSContext::Get()->Context(); + + mozilla::MallocSizeOf mallocSizeOf = + PR_GetEnv("MOZ_GC_LOG_SIZE") ? moz_malloc_size_of : nullptr; + js::DumpHeap(cx, aFile, js::CollectNurseryBeforeDump, mallocSizeOf); +} + +IncrementalFinalizeRunnable::IncrementalFinalizeRunnable( + CycleCollectedJSRuntime* aRt, DeferredFinalizerTable& aFinalizers) + : DiscardableRunnable("IncrementalFinalizeRunnable"), + mRuntime(aRt), + mFinalizeFunctionToRun(0), + mReleasing(false) { + for (auto iter = aFinalizers.Iter(); !iter.Done(); iter.Next()) { + DeferredFinalizeFunction& function = iter.Key(); + void*& data = iter.Data(); + + DeferredFinalizeFunctionHolder* holder = + mDeferredFinalizeFunctions.AppendElement(); + holder->run = function; + holder->data = data; + + iter.Remove(); + } + MOZ_ASSERT(mDeferredFinalizeFunctions.Length()); +} + +IncrementalFinalizeRunnable::~IncrementalFinalizeRunnable() { + MOZ_ASSERT(!mDeferredFinalizeFunctions.Length()); + MOZ_ASSERT(!mRuntime); +} + +void IncrementalFinalizeRunnable::ReleaseNow(bool aLimited) { + if (mReleasing) { + NS_WARNING("Re-entering ReleaseNow"); + return; + } + { + AUTO_PROFILER_LABEL("IncrementalFinalizeRunnable::ReleaseNow", + GCCC_Finalize); + + mozilla::AutoRestore<bool> ar(mReleasing); + mReleasing = true; + MOZ_ASSERT(mDeferredFinalizeFunctions.Length() != 0, + "We should have at least ReleaseSliceNow to run"); + MOZ_ASSERT(mFinalizeFunctionToRun < mDeferredFinalizeFunctions.Length(), + "No more finalizers to run?"); + + TimeDuration sliceTime = TimeDuration::FromMilliseconds(SliceMillis); + TimeStamp started = aLimited ? TimeStamp::Now() : TimeStamp(); + bool timeout = false; + do { + const DeferredFinalizeFunctionHolder& function = + mDeferredFinalizeFunctions[mFinalizeFunctionToRun]; + if (aLimited) { + bool done = false; + while (!timeout && !done) { + /* + * We don't want to read the clock too often, so we try to + * release slices of 100 items. + */ + done = function.run(100, function.data); + timeout = TimeStamp::Now() - started >= sliceTime; + } + if (done) { + ++mFinalizeFunctionToRun; + } + if (timeout) { + break; + } + } else { + while (!function.run(UINT32_MAX, function.data)) + ; + ++mFinalizeFunctionToRun; + } + } while (mFinalizeFunctionToRun < mDeferredFinalizeFunctions.Length()); + } + + if (mFinalizeFunctionToRun == mDeferredFinalizeFunctions.Length()) { + MOZ_ASSERT(mRuntime->mFinalizeRunnable == this); + mDeferredFinalizeFunctions.Clear(); + CycleCollectedJSRuntime* runtime = mRuntime; + mRuntime = nullptr; + // NB: This may delete this! + runtime->mFinalizeRunnable = nullptr; + } +} + +NS_IMETHODIMP +IncrementalFinalizeRunnable::Run() { + if (!mDeferredFinalizeFunctions.Length()) { + /* These items were already processed synchronously in JSGC_END. */ + MOZ_ASSERT(!mRuntime); + return NS_OK; + } + + MOZ_ASSERT(mRuntime->mFinalizeRunnable == this); + TimeStamp start = TimeStamp::Now(); + ReleaseNow(true); + + if (mDeferredFinalizeFunctions.Length()) { + nsresult rv = NS_DispatchToCurrentThread(this); + if (NS_FAILED(rv)) { + ReleaseNow(false); + } + } else { + MOZ_ASSERT(!mRuntime); + } + + uint32_t duration = (uint32_t)((TimeStamp::Now() - start).ToMilliseconds()); + Telemetry::Accumulate(Telemetry::DEFERRED_FINALIZE_ASYNC, duration); + + return NS_OK; +} + +void CycleCollectedJSRuntime::FinalizeDeferredThings( + DeferredFinalizeType aType) { + // If mFinalizeRunnable isn't null, we didn't finalize everything from the + // previous GC. + if (mFinalizeRunnable) { + if (aType == FinalizeLater) { + // We need to defer all finalization until we return to the event loop, + // so leave things alone. Any new objects to be finalized from the current + // GC will be handled by the existing mFinalizeRunnable. + return; + } + MOZ_ASSERT(aType == FinalizeIncrementally || aType == FinalizeNow); + // If we're finalizing incrementally, we don't want finalizers to build up, + // so try to finish them off now. + // If we're finalizing synchronously, also go ahead and clear them out, + // so we make sure as much as possible is freed. + mFinalizeRunnable->ReleaseNow(false); + if (mFinalizeRunnable) { + // If we re-entered ReleaseNow, we couldn't delete mFinalizeRunnable and + // we need to just continue processing it. + return; + } + } + + // If there's nothing to finalize, don't create a new runnable. + if (mDeferredFinalizerTable.Count() == 0) { + return; + } + + mFinalizeRunnable = + new IncrementalFinalizeRunnable(this, mDeferredFinalizerTable); + + // Everything should be gone now. + MOZ_ASSERT(mDeferredFinalizerTable.Count() == 0); + + if (aType == FinalizeNow) { + mFinalizeRunnable->ReleaseNow(false); + MOZ_ASSERT(!mFinalizeRunnable); + } else { + MOZ_ASSERT(aType == FinalizeIncrementally || aType == FinalizeLater); + NS_DispatchToCurrentThreadQueue(do_AddRef(mFinalizeRunnable), 2500, + EventQueuePriority::Idle); + } +} + +const char* CycleCollectedJSRuntime::OOMStateToString( + const OOMState aOomState) const { + switch (aOomState) { + case OOMState::OK: + return "OK"; + case OOMState::Reporting: + return "Reporting"; + case OOMState::Reported: + return "Reported"; + case OOMState::Recovered: + return "Recovered"; + default: + MOZ_ASSERT_UNREACHABLE("OOMState holds an invalid value"); + return "Unknown"; + } +} + +bool CycleCollectedJSRuntime::OOMReported() { + return mOutOfMemoryState == OOMState::Reported; +} + +void CycleCollectedJSRuntime::AnnotateAndSetOutOfMemory(OOMState* aStatePtr, + OOMState aNewState) { + *aStatePtr = aNewState; + CrashReporter::Annotation annotation = + (aStatePtr == &mOutOfMemoryState) + ? CrashReporter::Annotation::JSOutOfMemory + : CrashReporter::Annotation::JSLargeAllocationFailure; + + CrashReporter::AnnotateCrashReport( + annotation, nsDependentCString(OOMStateToString(aNewState))); +} + +void CycleCollectedJSRuntime::OnGC(JSContext* aContext, JSGCStatus aStatus, + JS::GCReason aReason) { + switch (aStatus) { + case JSGC_BEGIN: + MOZ_RELEASE_ASSERT(mHolderIter.isNothing()); + nsCycleCollector_prepareForGarbageCollection(); + PrepareWaitingZonesForGC(); + break; + case JSGC_END: { + MOZ_RELEASE_ASSERT(mHolderIter.isNothing()); + if (mOutOfMemoryState == OOMState::Reported) { + AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Recovered); + } + if (mLargeAllocationFailureState == OOMState::Reported) { + AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, + OOMState::Recovered); + } + + DeferredFinalizeType finalizeType; + if (JS_IsExceptionPending(aContext)) { + // There is a pending exception. The finalizers are not set up to run + // in that state, so don't run the finalizer until we've returned to the + // event loop. + finalizeType = FinalizeLater; + } else if (JS::InternalGCReason(aReason)) { + if (aReason == JS::GCReason::DESTROY_RUNTIME) { + // We're shutting down, so we need to destroy things immediately. + finalizeType = FinalizeNow; + } else { + // We may be in the middle of running some code that the JIT has + // assumed can't have certain kinds of side effects. Finalizers can do + // all sorts of things, such as run JS, so we want to run them later, + // after we've returned to the event loop. + finalizeType = FinalizeLater; + } + } else if (JS::WasIncrementalGC(mJSRuntime)) { + // The GC was incremental, so we probably care about pauses. Try to + // break up finalization, but it is okay if we do some now. + finalizeType = FinalizeIncrementally; + } else { + // If we're running a synchronous GC, we probably want to free things as + // quickly as possible. This can happen during testing or if memory is + // low. + finalizeType = FinalizeNow; + } + FinalizeDeferredThings(finalizeType); + + break; + } + default: + MOZ_CRASH(); + } + + CustomGCCallback(aStatus); +} + +void CycleCollectedJSRuntime::OnOutOfMemory() { + AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Reporting); + CustomOutOfMemoryCallback(); + AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Reported); +} + +void CycleCollectedJSRuntime::SetLargeAllocationFailure(OOMState aNewState) { + AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, aNewState); +} + +void CycleCollectedJSRuntime::PrepareWaitingZonesForGC() { + JSContext* cx = CycleCollectedJSContext::Get()->Context(); + if (mZonesWaitingForGC.Count() == 0) { + JS::PrepareForFullGC(cx); + } else { + for (const auto& key : mZonesWaitingForGC) { + JS::PrepareZoneForGC(cx, key); + } + mZonesWaitingForGC.Clear(); + } +} + +/* static */ +void CycleCollectedJSRuntime::OnZoneDestroyed(JS::GCContext* aGcx, + JS::Zone* aZone) { + // Remove the zone from the set of zones waiting for GC, if present. This can + // happen if a zone is added to the set during an incremental GC in which it + // is later destroyed. + CycleCollectedJSRuntime* runtime = Get(); + runtime->mZonesWaitingForGC.Remove(aZone); +} + +void CycleCollectedJSRuntime::EnvironmentPreparer::invoke( + JS::HandleObject global, js::ScriptEnvironmentPreparer::Closure& closure) { + MOZ_ASSERT(JS_IsGlobalObject(global)); + nsIGlobalObject* nativeGlobal = xpc::NativeGlobal(global); + + // Not much we can do if we simply don't have a usable global here... + NS_ENSURE_TRUE_VOID(nativeGlobal && nativeGlobal->HasJSGlobal()); + + AutoEntryScript aes(nativeGlobal, "JS-engine-initiated execution"); + + MOZ_ASSERT(!JS_IsExceptionPending(aes.cx())); + + DebugOnly<bool> ok = closure(aes.cx()); + + MOZ_ASSERT_IF(ok, !JS_IsExceptionPending(aes.cx())); + + // The AutoEntryScript will check for JS_IsExceptionPending on the + // JSContext and report it as needed as it comes off the stack. +} + +/* static */ +CycleCollectedJSRuntime* CycleCollectedJSRuntime::Get() { + auto context = CycleCollectedJSContext::Get(); + if (context) { + return context->Runtime(); + } + return nullptr; +} + +#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR + +namespace js { +extern void DumpValue(const JS::Value& val); +} + +void CycleCollectedJSRuntime::ErrorInterceptor::Shutdown(JSRuntime* rt) { + JS_SetErrorInterceptorCallback(rt, nullptr); + mThrownError.reset(); +} + +/* virtual */ +void CycleCollectedJSRuntime::ErrorInterceptor::interceptError( + JSContext* cx, JS::HandleValue exn) { + if (mThrownError) { + // We already have an error, we don't need anything more. + return; + } + + if (!nsContentUtils::ThreadsafeIsSystemCaller(cx)) { + // We are only interested in chrome code. + return; + } + + const auto type = JS_GetErrorType(exn); + if (!type) { + // This is not one of the primitive error types. + return; + } + + switch (*type) { + case JSExnType::JSEXN_REFERENCEERR: + case JSExnType::JSEXN_SYNTAXERR: + break; + default: + // Not one of the errors we are interested in. + // Note that we are not interested in instances of `TypeError` + // for the time being, as DOM (ab)uses this constructor to represent + // all sorts of errors that are not even remotely related to type + // errors (e.g. some network errors). + // If we ever have a mechanism to differentiate between DOM-thrown + // and SpiderMonkey-thrown instances of `TypeError`, we should + // consider watching for `TypeError` here. + return; + } + + // Now copy the details of the exception locally. + // While copying the details of an exception could be expensive, in most runs, + // this will be done at most once during the execution of the process, so the + // total cost should be reasonable. + + ErrorDetails details; + details.mType = *type; + // If `exn` isn't an exception object, `ExtractErrorValues` could end up + // calling `toString()`, which could in turn end up throwing an error. While + // this should work, we want to avoid that complex use case. Fortunately, we + // have already checked above that `exn` is an exception object, so nothing + // such should happen. + nsContentUtils::ExtractErrorValues(cx, exn, details.mFilename, &details.mLine, + &details.mColumn, details.mMessage); + + JS::UniqueChars buf = + JS::FormatStackDump(cx, /* showArgs = */ false, /* showLocals = */ false, + /* showThisProps = */ false); + CopyUTF8toUTF16(mozilla::MakeStringSpan(buf.get()), details.mStack); + + mThrownError.emplace(std::move(details)); +} + +void CycleCollectedJSRuntime::ClearRecentDevError() { + mErrorInterceptor.mThrownError.reset(); +} + +bool CycleCollectedJSRuntime::GetRecentDevError( + JSContext* cx, JS::MutableHandle<JS::Value> error) { + if (!mErrorInterceptor.mThrownError) { + return true; + } + + // Create a copy of the exception. + JS::RootedObject obj(cx, JS_NewPlainObject(cx)); + if (!obj) { + return false; + } + + JS::RootedValue message(cx); + JS::RootedValue filename(cx); + JS::RootedValue stack(cx); + if (!ToJSValue(cx, mErrorInterceptor.mThrownError->mMessage, &message) || + !ToJSValue(cx, mErrorInterceptor.mThrownError->mFilename, &filename) || + !ToJSValue(cx, mErrorInterceptor.mThrownError->mStack, &stack)) { + return false; + } + + // Build the object. + const auto FLAGS = JSPROP_READONLY | JSPROP_ENUMERATE | JSPROP_PERMANENT; + if (!JS_DefineProperty(cx, obj, "message", message, FLAGS) || + !JS_DefineProperty(cx, obj, "fileName", filename, FLAGS) || + !JS_DefineProperty(cx, obj, "lineNumber", + mErrorInterceptor.mThrownError->mLine, FLAGS) || + !JS_DefineProperty(cx, obj, "stack", stack, FLAGS)) { + return false; + } + + // Pass the result. + error.setObject(*obj); + return true; +} +#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR + +#undef MOZ_JS_DEV_ERROR_INTERCEPTOR |