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@ -8,20 +8,24 @@
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#define gc_WeakMap_h
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#include "mozilla/LinkedList.h"
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#include "mozilla/Move.h"
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#include "jsfriendapi.h"
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#include "gc/Barrier.h"
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#include "gc/DeletePolicy.h"
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#include "gc/StoreBuffer.h"
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#include "js/HashTable.h"
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#include "vm/JSObject.h"
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#include "vm/Realm.h"
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namespace JS {
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class Zone;
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} // namespace JS
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namespace js {
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class GCMarker;
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class WeakMapBase;
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struct WeakMapTracer;
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namespace gc {
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struct WeakMarkable;
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} // namespace gc
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// A subclass template of js::HashMap whose keys and values may be garbage-collected. When
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// a key is collected, the table entry disappears, dropping its reference to the value.
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@ -49,7 +53,7 @@ class WeakMapBase : public mozilla::LinkedListElement<WeakMapBase>
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WeakMapBase(JSObject* memOf, JS::Zone* zone);
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virtual ~WeakMapBase();
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Zone* zone() const { return zone_; }
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JS::Zone* zone() const { return zone_; }
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// Garbage collector entry points.
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@ -107,17 +111,6 @@ class WeakMapBase : public mozilla::LinkedListElement<WeakMapBase>
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bool marked;
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};
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template <typename T>
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static T extractUnbarriered(const WriteBarrieredBase<T>& v)
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{
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return v.get();
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}
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template <typename T>
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static T* extractUnbarriered(T* v)
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{
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return v;
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}
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template <class Key, class Value,
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class HashPolicy = DefaultHasher<Key> >
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class WeakMap : public HashMap<Key, Value, HashPolicy, ZoneAllocPolicy>,
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@ -132,16 +125,9 @@ class WeakMap : public HashMap<Key, Value, HashPolicy, ZoneAllocPolicy>,
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typedef typename Base::Ptr Ptr;
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typedef typename Base::AddPtr AddPtr;
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explicit WeakMap(JSContext* cx, JSObject* memOf = nullptr)
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: Base(cx->zone()), WeakMapBase(memOf, cx->zone()) { }
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explicit WeakMap(JSContext* cx, JSObject* memOf = nullptr);
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bool init(uint32_t len = 16) {
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if (!Base::init(len))
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return false;
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zone()->gcWeakMapList().insertFront(this);
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marked = JS::IsIncrementalGCInProgress(TlsContext.get());
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return true;
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}
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bool init(uint32_t len = 16);
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// Overwritten to add a read barrier to prevent an incorrectly gray value
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// from escaping the weak map. See the UnmarkGrayTracer::onChild comment in
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@ -170,204 +156,46 @@ class WeakMap : public HashMap<Key, Value, HashPolicy, ZoneAllocPolicy>,
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// Resolve ambiguity with LinkedListElement<>::remove.
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using Base::remove;
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// Trace a WeakMap entry based on 'markedCell' getting marked, where
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// 'origKey' is the key in the weakmap. These will probably be the same,
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// but can be different eg when markedCell is a delegate for origKey.
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//
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// This implementation does not use 'markedCell'; it looks up origKey and
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// checks the mark bits on everything it cares about, one of which will be
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// markedCell. But a subclass might use it to optimize the liveness check.
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void markEntry(GCMarker* marker, gc::Cell* markedCell, JS::GCCellPtr origKey) override
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{
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MOZ_ASSERT(marked);
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void markEntry(GCMarker* marker, gc::Cell* markedCell, JS::GCCellPtr origKey) override;
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// If this cast fails, then you're instantiating the WeakMap with a
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// Lookup that can't be constructed from a Cell*. The WeakKeyTable
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// mechanism is indexed with a GCCellPtr, so that won't work.
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Ptr p = Base::lookup(static_cast<Lookup>(origKey.asCell()));
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MOZ_ASSERT(p.found());
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Key key(p->key());
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MOZ_ASSERT((markedCell == extractUnbarriered(key)) || (markedCell == getDelegate(key)));
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if (gc::IsMarked(marker->runtime(), &key)) {
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TraceEdge(marker, &p->value(), "ephemeron value");
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} else if (keyNeedsMark(key)) {
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TraceEdge(marker, &p->value(), "WeakMap ephemeron value");
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TraceEdge(marker, &key, "proxy-preserved WeakMap ephemeron key");
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MOZ_ASSERT(key == p->key()); // No moving
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}
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key.unsafeSet(nullptr); // Prevent destructor from running barriers.
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}
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void trace(JSTracer* trc) override {
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MOZ_ASSERT_IF(JS::RuntimeHeapIsBusy(), isInList());
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TraceNullableEdge(trc, &memberOf, "WeakMap owner");
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if (!Base::initialized())
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return;
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if (trc->isMarkingTracer()) {
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MOZ_ASSERT(trc->weakMapAction() == ExpandWeakMaps);
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marked = true;
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(void) markIteratively(GCMarker::fromTracer(trc));
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return;
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}
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if (trc->weakMapAction() == DoNotTraceWeakMaps)
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return;
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// Trace keys only if weakMapAction() says to.
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if (trc->weakMapAction() == TraceWeakMapKeysValues) {
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for (Enum e(*this); !e.empty(); e.popFront())
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TraceEdge(trc, &e.front().mutableKey(), "WeakMap entry key");
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}
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// Always trace all values (unless weakMapAction() is
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// DoNotTraceWeakMaps).
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for (Range r = Base::all(); !r.empty(); r.popFront())
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TraceEdge(trc, &r.front().value(), "WeakMap entry value");
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}
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void trace(JSTracer* trc) override;
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protected:
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static void addWeakEntry(GCMarker* marker, JS::GCCellPtr key, gc::WeakMarkable markable)
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{
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Zone* zone = key.asCell()->asTenured().zone();
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static void addWeakEntry(GCMarker* marker, JS::GCCellPtr key,
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const gc::WeakMarkable& markable);
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auto p = zone->gcWeakKeys().get(key);
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if (p) {
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gc::WeakEntryVector& weakEntries = p->value;
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if (!weakEntries.append(std::move(markable)))
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marker->abortLinearWeakMarking();
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} else {
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gc::WeakEntryVector weakEntries;
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MOZ_ALWAYS_TRUE(weakEntries.append(std::move(markable)));
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if (!zone->gcWeakKeys().put(JS::GCCellPtr(key), std::move(weakEntries)))
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marker->abortLinearWeakMarking();
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}
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}
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bool markIteratively(GCMarker* marker) override;
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bool markIteratively(GCMarker* marker) override {
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MOZ_ASSERT(marked);
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bool markedAny = false;
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for (Enum e(*this); !e.empty(); e.popFront()) {
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// If the entry is live, ensure its key and value are marked.
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bool keyIsMarked = gc::IsMarked(marker->runtime(), &e.front().mutableKey());
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if (!keyIsMarked && keyNeedsMark(e.front().key())) {
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TraceEdge(marker, &e.front().mutableKey(), "proxy-preserved WeakMap entry key");
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keyIsMarked = true;
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markedAny = true;
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}
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if (keyIsMarked) {
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if (!gc::IsMarked(marker->runtime(), &e.front().value())) {
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TraceEdge(marker, &e.front().value(), "WeakMap entry value");
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markedAny = true;
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}
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} else if (marker->isWeakMarkingTracer()) {
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// Entry is not yet known to be live. Record this weakmap and
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// the lookup key in the list of weak keys. Also record the
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// delegate, if any, because marking the delegate also marks
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// the entry.
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JS::GCCellPtr weakKey(extractUnbarriered(e.front().key()));
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gc::WeakMarkable markable(this, weakKey);
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addWeakEntry(marker, weakKey, markable);
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if (JSObject* delegate = getDelegate(e.front().key()))
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addWeakEntry(marker, JS::GCCellPtr(delegate), markable);
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}
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}
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return markedAny;
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}
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JSObject* getDelegate(JSObject* key) const {
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JSWeakmapKeyDelegateOp op = key->getClass()->extWeakmapKeyDelegateOp();
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if (!op)
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return nullptr;
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JSObject* obj = op(key);
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if (!obj)
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return nullptr;
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MOZ_ASSERT(obj->runtimeFromMainThread() == zone()->runtimeFromMainThread());
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return obj;
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}
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JSObject* getDelegate(JSScript* script) const {
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return nullptr;
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}
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JSObject* getDelegate(LazyScript* script) const {
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return nullptr;
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}
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JSObject* getDelegate(JSObject* key) const;
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JSObject* getDelegate(JSScript* script) const;
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JSObject* getDelegate(LazyScript* script) const;
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private:
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void exposeGCThingToActiveJS(const JS::Value& v) const { JS::ExposeValueToActiveJS(v); }
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void exposeGCThingToActiveJS(JSObject* obj) const { JS::ExposeObjectToActiveJS(obj); }
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bool keyNeedsMark(JSObject* key) const {
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JSObject* delegate = getDelegate(key);
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/*
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* Check if the delegate is marked with any color to properly handle
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* gray marking when the key's delegate is black and the map is gray.
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*/
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return delegate && gc::IsMarkedUnbarriered(zone()->runtimeFromMainThread(), &delegate);
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}
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bool keyNeedsMark(JSScript* script) const {
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return false;
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}
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bool keyNeedsMark(LazyScript* script) const {
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return false;
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}
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bool keyNeedsMark(JSObject* key) const;
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bool keyNeedsMark(JSScript* script) const;
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bool keyNeedsMark(LazyScript* script) const;
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bool findZoneEdges() override {
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// This is overridden by ObjectValueMap.
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return true;
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}
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void sweep() override {
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/* Remove all entries whose keys remain unmarked. */
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for (Enum e(*this); !e.empty(); e.popFront()) {
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if (gc::IsAboutToBeFinalized(&e.front().mutableKey()))
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e.removeFront();
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}
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/*
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* Once we've swept, all remaining edges should stay within the
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* known-live part of the graph.
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*/
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assertEntriesNotAboutToBeFinalized();
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}
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void sweep() override;
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void finish() override {
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Base::finish();
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}
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/* memberOf can be nullptr, which means that the map is not part of a JSObject. */
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void traceMappings(WeakMapTracer* tracer) override {
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for (Range r = Base::all(); !r.empty(); r.popFront()) {
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gc::Cell* key = gc::ToMarkable(r.front().key());
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gc::Cell* value = gc::ToMarkable(r.front().value());
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if (key && value) {
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tracer->trace(memberOf,
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JS::GCCellPtr(r.front().key().get()),
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JS::GCCellPtr(r.front().value().get()));
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}
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}
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}
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void traceMappings(WeakMapTracer* tracer) override;
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protected:
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void assertEntriesNotAboutToBeFinalized() {
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#if DEBUG
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for (Range r = Base::all(); !r.empty(); r.popFront()) {
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Key k(r.front().key());
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MOZ_ASSERT(!gc::IsAboutToBeFinalized(&k));
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MOZ_ASSERT(!gc::IsAboutToBeFinalized(&r.front().value()));
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MOZ_ASSERT(k == r.front().key());
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}
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void assertEntriesNotAboutToBeFinalized();
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#endif
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}
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};
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