mirror of
https://github.com/classilla/tenfourfox.git
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432 lines
16 KiB
C++
432 lines
16 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* vim: set ts=8 sts=4 et sw=4 tw=99:
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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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#ifndef js_TracingAPI_h
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#define js_TracingAPI_h
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#include "jsalloc.h"
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#include "js/HashTable.h"
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#include "js/HeapAPI.h"
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#include "js/TraceKind.h"
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class JS_PUBLIC_API(JSTracer);
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namespace JS {
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class JS_PUBLIC_API(CallbackTracer);
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template <typename T> class Heap;
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template <typename T> class TenuredHeap;
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/** Returns a static string equivalent of |kind|. */
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JS_FRIEND_API(const char*)
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GCTraceKindToAscii(JS::TraceKind kind);
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} // namespace JS
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enum WeakMapTraceKind {
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/** Do true ephemeron marking with an iterative weak marking phase. */
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DoNotTraceWeakMaps,
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/**
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* Do true ephemeron marking with a weak key lookup marking phase. This is
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* expected to be constant for the lifetime of a JSTracer; it does not
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* change when switching from "plain" marking to weak marking.
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*/
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ExpandWeakMaps,
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/**
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* Trace through to all values, irrespective of whether the keys are live
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* or not. Used for non-marking tracers.
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*/
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TraceWeakMapValues,
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/**
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* Trace through to all keys and values, irrespective of whether the keys
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* are live or not. Used for non-marking tracers.
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*/
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TraceWeakMapKeysValues
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};
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class JS_PUBLIC_API(JSTracer)
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{
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public:
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// Return the runtime set on the tracer.
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JSRuntime* runtime() const { return runtime_; }
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// Return the weak map tracing behavior currently set on this tracer.
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WeakMapTraceKind weakMapAction() const { return weakMapAction_; }
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// An intermediate state on the road from C to C++ style dispatch.
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enum class TracerKindTag {
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Marking,
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WeakMarking, // In weak marking phase: looking up every marked obj/script.
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Tenuring,
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Callback
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};
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bool isMarkingTracer() const { return tag_ == TracerKindTag::Marking || tag_ == TracerKindTag::WeakMarking; }
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bool isWeakMarkingTracer() const { return tag_ == TracerKindTag::WeakMarking; }
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bool isTenuringTracer() const { return tag_ == TracerKindTag::Tenuring; }
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bool isCallbackTracer() const { return tag_ == TracerKindTag::Callback; }
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inline JS::CallbackTracer* asCallbackTracer();
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protected:
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JSTracer(JSRuntime* rt, TracerKindTag tag,
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WeakMapTraceKind weakTraceKind = TraceWeakMapValues)
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: runtime_(rt), weakMapAction_(weakTraceKind), tag_(tag)
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{}
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private:
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JSRuntime* runtime_;
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WeakMapTraceKind weakMapAction_;
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protected:
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TracerKindTag tag_;
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};
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namespace JS {
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class AutoTracingName;
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class AutoTracingIndex;
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class AutoTracingCallback;
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class JS_PUBLIC_API(CallbackTracer) : public JSTracer
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{
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public:
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CallbackTracer(JSRuntime* rt, WeakMapTraceKind weakTraceKind = TraceWeakMapValues)
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: JSTracer(rt, JSTracer::TracerKindTag::Callback, weakTraceKind),
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contextName_(nullptr), contextIndex_(InvalidIndex), contextFunctor_(nullptr)
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{}
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// Override these methods to receive notification when an edge is visited
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// with the type contained in the callback. The default implementation
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// dispatches to the fully-generic onChild implementation, so for cases that
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// do not care about boxing overhead and do not need the actual edges,
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// just override the generic onChild.
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virtual void onObjectEdge(JSObject** objp) { onChild(JS::GCCellPtr(*objp)); }
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virtual void onStringEdge(JSString** strp) { onChild(JS::GCCellPtr(*strp)); }
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virtual void onSymbolEdge(JS::Symbol** symp) { onChild(JS::GCCellPtr(*symp)); }
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virtual void onScriptEdge(JSScript** scriptp) { onChild(JS::GCCellPtr(*scriptp)); }
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virtual void onShapeEdge(js::Shape** shapep) {
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onChild(JS::GCCellPtr(*shapep, JS::TraceKind::Shape));
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}
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virtual void onObjectGroupEdge(js::ObjectGroup** groupp) {
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onChild(JS::GCCellPtr(*groupp, JS::TraceKind::ObjectGroup));
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}
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virtual void onBaseShapeEdge(js::BaseShape** basep) {
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onChild(JS::GCCellPtr(*basep, JS::TraceKind::BaseShape));
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}
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virtual void onJitCodeEdge(js::jit::JitCode** codep) {
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onChild(JS::GCCellPtr(*codep, JS::TraceKind::JitCode));
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}
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virtual void onLazyScriptEdge(js::LazyScript** lazyp) {
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onChild(JS::GCCellPtr(*lazyp, JS::TraceKind::LazyScript));
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}
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// Override this method to receive notification when a node in the GC
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// heap graph is visited.
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virtual void onChild(const JS::GCCellPtr& thing) = 0;
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// Access to the tracing context:
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// When tracing with a JS::CallbackTracer, we invoke the callback with the
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// edge location and the type of target. This is useful for operating on
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// the edge in the abstract or on the target thing, satisfying most common
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// use cases. However, some tracers need additional detail about the
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// specific edge that is being traced in order to be useful. Unfortunately,
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// the raw pointer to the edge that we provide is not enough information to
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// infer much of anything useful about that edge.
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//
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// In order to better support use cases that care in particular about edges
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// -- as opposed to the target thing -- tracing implementations are
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// responsible for providing extra context information about each edge they
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// trace, as it is traced. This contains, at a minimum, an edge name and,
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// when tracing an array, the index. Further specialization can be achived
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// (with some complexity), by associating a functor with the tracer so
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// that, when requested, the user can generate totally custom edge
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// descriptions.
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// Returns the current edge's name. It is only valid to call this when
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// inside the trace callback, however, the edge name will always be set.
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const char* contextName() const { MOZ_ASSERT(contextName_); return contextName_; }
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// Returns the current edge's index, if marked as part of an array of edges.
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// This must be called only inside the trace callback. When not tracing an
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// array, the value will be InvalidIndex.
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const static size_t InvalidIndex = size_t(-1);
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size_t contextIndex() const { return contextIndex_; }
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// Build a description of this edge in the heap graph. This call may invoke
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// the context functor, if set, which may inspect arbitrary areas of the
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// heap. On the other hand, the description provided by this method may be
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// substantially more accurate and useful than those provided by only the
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// contextName and contextIndex.
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void getTracingEdgeName(char* buffer, size_t bufferSize);
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// The trace implementation may associate a callback with one or more edges
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// using AutoTracingDetails. This functor is called by getTracingEdgeName
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// and is responsible for providing a textual representation of the
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// currently being traced edge. The callback has access to the full heap,
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// including the currently set tracing context.
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class ContextFunctor {
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public:
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virtual void operator()(CallbackTracer* trc, char* buf, size_t bufsize) = 0;
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};
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#ifdef DEBUG
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enum class TracerKind { DoNotCare, Moving, GrayBuffering, VerifyTraceProtoAndIface };
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virtual TracerKind getTracerKind() const { return TracerKind::DoNotCare; }
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#endif
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// In C++, overriding a method hides all methods in the base class with
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// that name, not just methods with that signature. Thus, the typed edge
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// methods have to have distinct names to allow us to override them
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// individually, which is freqently useful if, for example, we only want to
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// process only one type of edge.
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void dispatchToOnEdge(JSObject** objp) { onObjectEdge(objp); }
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void dispatchToOnEdge(JSString** strp) { onStringEdge(strp); }
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void dispatchToOnEdge(JS::Symbol** symp) { onSymbolEdge(symp); }
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void dispatchToOnEdge(JSScript** scriptp) { onScriptEdge(scriptp); }
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void dispatchToOnEdge(js::Shape** shapep) { onShapeEdge(shapep); }
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void dispatchToOnEdge(js::ObjectGroup** groupp) { onObjectGroupEdge(groupp); }
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void dispatchToOnEdge(js::BaseShape** basep) { onBaseShapeEdge(basep); }
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void dispatchToOnEdge(js::jit::JitCode** codep) { onJitCodeEdge(codep); }
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void dispatchToOnEdge(js::LazyScript** lazyp) { onLazyScriptEdge(lazyp); }
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private:
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friend class AutoTracingName;
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const char* contextName_;
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friend class AutoTracingIndex;
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size_t contextIndex_;
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friend class AutoTracingDetails;
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ContextFunctor* contextFunctor_;
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};
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// Set the name portion of the tracer's context for the current edge.
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class MOZ_RAII AutoTracingName
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{
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CallbackTracer* trc_;
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const char* prior_;
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public:
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AutoTracingName(CallbackTracer* trc, const char* name) : trc_(trc), prior_(trc->contextName_) {
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MOZ_ASSERT(name);
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trc->contextName_ = name;
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}
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~AutoTracingName() {
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MOZ_ASSERT(trc_->contextName_);
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trc_->contextName_ = prior_;
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}
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};
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// Set the index portion of the tracer's context for the current range.
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class MOZ_RAII AutoTracingIndex
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{
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CallbackTracer* trc_;
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public:
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explicit AutoTracingIndex(JSTracer* trc, size_t initial = 0) : trc_(nullptr) {
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if (trc->isCallbackTracer()) {
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trc_ = trc->asCallbackTracer();
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MOZ_ASSERT(trc_->contextIndex_ == CallbackTracer::InvalidIndex);
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trc_->contextIndex_ = initial;
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}
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}
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~AutoTracingIndex() {
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if (trc_) {
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MOZ_ASSERT(trc_->contextIndex_ != CallbackTracer::InvalidIndex);
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trc_->contextIndex_ = CallbackTracer::InvalidIndex;
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}
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}
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void operator++() {
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if (trc_) {
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MOZ_ASSERT(trc_->contextIndex_ != CallbackTracer::InvalidIndex);
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++trc_->contextIndex_;
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}
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}
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};
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// Set a context callback for the trace callback to use, if it needs a detailed
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// edge description.
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class MOZ_RAII AutoTracingDetails
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{
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CallbackTracer* trc_;
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public:
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AutoTracingDetails(JSTracer* trc, CallbackTracer::ContextFunctor& func) : trc_(nullptr) {
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if (trc->isCallbackTracer()) {
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trc_ = trc->asCallbackTracer();
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MOZ_ASSERT(trc_->contextFunctor_ == nullptr);
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trc_->contextFunctor_ = &func;
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}
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}
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~AutoTracingDetails() {
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if (trc_) {
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MOZ_ASSERT(trc_->contextFunctor_);
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trc_->contextFunctor_ = nullptr;
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}
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}
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};
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} // namespace JS
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JS::CallbackTracer*
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JSTracer::asCallbackTracer()
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{
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MOZ_ASSERT(isCallbackTracer());
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return static_cast<JS::CallbackTracer*>(this);
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}
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// The JS_Call*Tracer family of functions traces the given GC thing reference.
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// This performs the tracing action configured on the given JSTracer:
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// typically calling the JSTracer::callback or marking the thing as live.
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//
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// The argument to JS_Call*Tracer is an in-out param: when the function
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// returns, the garbage collector might have moved the GC thing. In this case,
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// the reference passed to JS_Call*Tracer will be updated to the object's new
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// location. Callers of this method are responsible for updating any state
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// that is dependent on the object's address. For example, if the object's
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// address is used as a key in a hashtable, then the object must be removed
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// and re-inserted with the correct hash.
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//
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extern JS_PUBLIC_API(void)
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JS_CallValueTracer(JSTracer* trc, JS::Heap<JS::Value>* valuep, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallIdTracer(JSTracer* trc, JS::Heap<jsid>* idp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallObjectTracer(JSTracer* trc, JS::Heap<JSObject*>* objp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallStringTracer(JSTracer* trc, JS::Heap<JSString*>* strp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallScriptTracer(JSTracer* trc, JS::Heap<JSScript*>* scriptp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallFunctionTracer(JSTracer* trc, JS::Heap<JSFunction*>* funp, const char* name);
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namespace JS {
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template <typename T>
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extern JS_PUBLIC_API(void)
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TraceEdge(JSTracer* trc, JS::Heap<T>* edgep, const char* name);
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} // namespace JS
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// The following JS_CallUnbarriered*Tracer functions should only be called where
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// you know for sure that a heap post barrier is not required. Use with extreme
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// caution!
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extern JS_PUBLIC_API(void)
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JS_CallUnbarrieredValueTracer(JSTracer* trc, JS::Value* valuep, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallUnbarrieredIdTracer(JSTracer* trc, jsid* idp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallUnbarrieredObjectTracer(JSTracer* trc, JSObject** objp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallUnbarrieredStringTracer(JSTracer* trc, JSString** strp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_CallUnbarrieredScriptTracer(JSTracer* trc, JSScript** scriptp, const char* name);
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/**
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* Trace an object that is known to always be tenured. No post barriers are
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* required in this case.
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*/
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extern JS_PUBLIC_API(void)
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JS_CallTenuredObjectTracer(JSTracer* trc, JS::TenuredHeap<JSObject*>* objp, const char* name);
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extern JS_PUBLIC_API(void)
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JS_TraceRuntime(JSTracer* trc);
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namespace JS {
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extern JS_PUBLIC_API(void)
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TraceChildren(JSTracer* trc, GCCellPtr thing);
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typedef js::HashSet<Zone*, js::DefaultHasher<Zone*>, js::SystemAllocPolicy> ZoneSet;
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} // namespace JS
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/**
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* Trace every value within |zones| that is wrapped by a cross-compartment
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* wrapper from a zone that is not an element of |zones|.
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*/
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extern JS_PUBLIC_API(void)
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JS_TraceIncomingCCWs(JSTracer* trc, const JS::ZoneSet& zones);
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extern JS_PUBLIC_API(void)
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JS_GetTraceThingInfo(char* buf, size_t bufsize, JSTracer* trc,
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void* thing, JS::TraceKind kind, bool includeDetails);
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namespace js {
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namespace gc {
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template <typename T>
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extern JS_PUBLIC_API(bool)
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EdgeNeedsSweep(JS::Heap<T>* edgep);
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} // namespace gc
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// Automates static dispatch for GC interaction with TraceableContainers.
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template <typename>
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struct DefaultGCPolicy;
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// This policy dispatches GC methods to a method on the type.
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template <typename T>
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struct StructGCPolicy {
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static void trace(JSTracer* trc, T* t, const char* name) {
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// This is the default GC policy for storing GC things in containers.
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// If your build is failing here, it means you either need an
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// implementation of DefaultGCPolicy<T> for your type or, if this is
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// the right policy for you, your struct or container is missing a
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// trace method.
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t->trace(trc);
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}
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static bool needsSweep(T* t) {
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return t->needsSweep();
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}
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};
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// This policy ignores any GC interaction, e.g. for non-GC types.
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template <typename T>
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struct IgnoreGCPolicy {
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static void trace(JSTracer* trc, T* t, const char* name) {}
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static bool needsSweep(T* v) { return false; }
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};
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// The default policy when no other more specific policy fits (e.g. for a
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// direct GC pointer), is to assume a struct type that implements the needed
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// methods.
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template <typename T>
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struct DefaultGCPolicy : public StructGCPolicy<T> {};
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template <>
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struct DefaultGCPolicy<jsid>
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{
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static void trace(JSTracer* trc, jsid* id, const char* name) {
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JS_CallUnbarrieredIdTracer(trc, id, name);
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}
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};
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template <> struct DefaultGCPolicy<uint32_t> : public IgnoreGCPolicy<uint32_t> {};
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template <> struct DefaultGCPolicy<uint64_t> : public IgnoreGCPolicy<uint64_t> {};
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template <typename T>
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struct DefaultGCPolicy<JS::Heap<T>>
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{
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static void trace(JSTracer* trc, JS::Heap<T>* thingp, const char* name) {
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JS::TraceEdge(trc, thingp, name);
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}
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static bool needsSweep(JS::Heap<T>* thingp) {
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return gc::EdgeNeedsSweep(thingp);
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}
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};
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} // namespace js
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#endif /* js_TracingAPI_h */
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