The Tor Browser: xpcom/base/nsCycleCollector.cpp@6474c204b198 (annotated)

xpcom/base/nsCycleCollector.cpp@6474c204b198 (annotated)

xpcom/base/nsCycleCollector.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /* vim: set ts=8 sts=4 et sw=4 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/. */
 //
 // This file implements a garbage-cycle collector based on the paper
 //
 //   Concurrent Cycle Collection in Reference Counted Systems
 //   Bacon & Rajan (2001), ECOOP 2001 / Springer LNCS vol 2072
 //
 // We are not using the concurrent or acyclic cases of that paper; so
 // the green, red and orange colors are not used.
 //
 // The collector is based on tracking pointers of four colors:
 //
 // Black nodes are definitely live. If we ever determine a node is
 // black, it's ok to forget about, drop from our records.
 //
 // White nodes are definitely garbage cycles. Once we finish with our
 // scanning, we unlink all the white nodes and expect that by
 // unlinking them they will self-destruct (since a garbage cycle is
 // only keeping itself alive with internal links, by definition).
 //
 // Snow-white is an addition to the original algorithm. Snow-white object
 // has reference count zero and is just waiting for deletion.
 //
 // Grey nodes are being scanned. Nodes that turn grey will turn
 // either black if we determine that they're live, or white if we
 // determine that they're a garbage cycle. After the main collection
 // algorithm there should be no grey nodes.
 //
 // Purple nodes are *candidates* for being scanned. They are nodes we
 // haven't begun scanning yet because they're not old enough, or we're
 // still partway through the algorithm.
 //
 // XPCOM objects participating in garbage-cycle collection are obliged
 // to inform us when they ought to turn purple; that is, when their
 // refcount transitions from N+1 -> N, for nonzero N. Furthermore we
 // require that *after* an XPCOM object has informed us of turning
 // purple, they will tell us when they either transition back to being
 // black (incremented refcount) or are ultimately deleted.
 // Incremental cycle collection
 //
 // Beyond the simple state machine required to implement incremental
 // collection, the CC needs to be able to compensate for things the browser
 // is doing during the collection. There are two kinds of problems. For each
 // of these, there are two cases to deal with: purple-buffered C++ objects
 // and JS objects.
 // The first problem is that an object in the CC's graph can become garbage.
 // This is bad because the CC touches the objects in its graph at every
 // stage of its operation.
 //
 // All cycle collected C++ objects that die during a cycle collection
 // will end up actually getting deleted by the SnowWhiteKiller. Before
 // the SWK deletes an object, it checks if an ICC is running, and if so,
 // if the object is in the graph. If it is, the CC clears mPointer and
 // mParticipant so it does not point to the raw object any more. Because
 // objects could die any time the CC returns to the mutator, any time the CC
 // accesses a PtrInfo it must perform a null check on mParticipant to
 // ensure the object has not gone away.
 //
 // JS objects don't always run finalizers, so the CC can't remove them from
 // the graph when they die. Fortunately, JS objects can only die during a GC,
 // so if a GC is begun during an ICC, the browser synchronously finishes off
 // the ICC, which clears the entire CC graph. If the GC and CC are scheduled
 // properly, this should be rare.
 //
 // The second problem is that objects in the graph can be changed, say by
 // being addrefed or released, or by having a field updated, after the object
 // has been added to the graph. The problem is that ICC can miss a newly
 // created reference to an object, and end up unlinking an object that is
 // actually alive.
 //
 // The basic idea of the solution, from "An on-the-fly Reference Counting
 // Garbage Collector for Java" by Levanoni and Petrank, is to notice if an
 // object has had an additional reference to it created during the collection,
 // and if so, don't collect it during the current collection. This avoids having
 // to rerun the scan as in Bacon & Rajan 2001.
 //
 // For cycle collected C++ objects, we modify AddRef to place the object in
 // the purple buffer, in addition to Release. Then, in the CC, we treat any
 // objects in the purple buffer as being alive, after graph building has
 // completed. Because they are in the purple buffer, they will be suspected
 // in the next CC, so there's no danger of leaks. This is imprecise, because
 // we will treat as live an object that has been Released but not AddRefed
 // during graph building, but that's probably rare enough that the additional
 // bookkeeping overhead is not worthwhile.
 //
 // For JS objects, the cycle collector is only looking at gray objects. If a
 // gray object is touched during ICC, it will be made black by UnmarkGray.
 // Thus, if a JS object has become black during the ICC, we treat it as live.
 // Merged JS zones have to be handled specially: we scan all zone globals.
 // If any are black, we treat the zone as being black.
 // Safety
 //
 // An XPCOM object is either scan-safe or scan-unsafe, purple-safe or
 // purple-unsafe.
 //
 // An nsISupports object is scan-safe if:
 //
 //  - It can be QI'ed to |nsXPCOMCycleCollectionParticipant|, though
 //    this operation loses ISupports identity (like nsIClassInfo).
 //  - Additionally, the operation |traverse| on the resulting
 //    nsXPCOMCycleCollectionParticipant does not cause *any* refcount
 //    adjustment to occur (no AddRef / Release calls).
 //
 // A non-nsISupports ("native") object is scan-safe by explicitly
 // providing its nsCycleCollectionParticipant.
 //
 // An object is purple-safe if it satisfies the following properties:
 //
 //  - The object is scan-safe.
 //
 // When we receive a pointer |ptr| via
 // |nsCycleCollector::suspect(ptr)|, we assume it is purple-safe. We
 // can check the scan-safety, but have no way to ensure the
 // purple-safety; objects must obey, or else the entire system falls
 // apart. Don't involve an object in this scheme if you can't
 // guarantee its purple-safety. The easiest way to ensure that an
 // object is purple-safe is to use nsCycleCollectingAutoRefCnt.
 //
 // When we have a scannable set of purple nodes ready, we begin
 // our walks. During the walks, the nodes we |traverse| should only
 // feed us more scan-safe nodes, and should not adjust the refcounts
 // of those nodes.
 //
 // We do not |AddRef| or |Release| any objects during scanning. We
 // rely on the purple-safety of the roots that call |suspect| to
 // hold, such that we will clear the pointer from the purple buffer
 // entry to the object before it is destroyed. The pointers that are
 // merely scan-safe we hold only for the duration of scanning, and
 // there should be no objects released from the scan-safe set during
 // the scan.
 //
 // We *do* call |Root| and |Unroot| on every white object, on
 // either side of the calls to |Unlink|. This keeps the set of white
 // objects alive during the unlinking.
 //
 #if !defined(__MINGW32__)
 #ifdef WIN32
 #include <crtdbg.h>
 #include <errno.h>
 #endif
 #endif
 #include "base/process_util.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/AutoRestore.h"
 #include "mozilla/CycleCollectedJSRuntime.h"
 #include "mozilla/HoldDropJSObjects.h"
 /* This must occur *after* base/process_util.h to avoid typedefs conflicts. */
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/LinkedList.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsCycleCollectionNoteRootCallback.h"
 #include "nsDeque.h"
 #include "nsCycleCollector.h"
 #include "nsThreadUtils.h"
 #include "nsXULAppAPI.h"
 #include "prenv.h"
 #include "nsPrintfCString.h"
 #include "nsTArray.h"
 #include "nsIConsoleService.h"
 #include "mozilla/Attributes.h"
 #include "nsICycleCollectorListener.h"
 #include "nsIMemoryReporter.h"
 #include "nsIFile.h"
 #include "nsDumpUtils.h"
 #include "xpcpublic.h"
 #include "GeckoProfiler.h"
 #include "js/SliceBudget.h"
 #include <stdint.h>
 #include <stdio.h>
 #include "mozilla/Likely.h"
 #include "mozilla/PoisonIOInterposer.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/ThreadLocal.h"
 using namespace mozilla;
 //#define COLLECT_TIME_DEBUG
 // Enable assertions that are useful for diagnosing errors in graph construction.
 //#define DEBUG_CC_GRAPH
 #define DEFAULT_SHUTDOWN_COLLECTIONS 5
 // One to do the freeing, then another to detect there is no more work to do.
 #define NORMAL_SHUTDOWN_COLLECTIONS 2
 // Cycle collector environment variables
 //
 // MOZ_CC_LOG_ALL: If defined, always log cycle collector heaps.
 //
 // MOZ_CC_LOG_SHUTDOWN: If defined, log cycle collector heaps at shutdown.
 //
 // MOZ_CC_LOG_THREAD: If set to "main", only automatically log main thread
 // CCs. If set to "worker", only automatically log worker CCs. If set to "all",
 // log either. The default value is "all". This must be used with either
 // MOZ_CC_LOG_ALL or MOZ_CC_LOG_SHUTDOWN for it to do anything.
 //
 // MOZ_CC_LOG_PROCESS: If set to "main", only automatically log main process
 // CCs. If set to "content", only automatically log tab CCs. If set to
 // "plugins", only automatically log plugin CCs. If set to "all", log
 // everything. The default value is "all". This must be used with either
 // MOZ_CC_LOG_ALL or MOZ_CC_LOG_SHUTDOWN for it to do anything.
 //
 // MOZ_CC_ALL_TRACES: If set to "all", any cycle collector
 // logging done will be WantAllTraces, which disables
 // various cycle collector optimizations to give a fuller picture of
 // the heap. If set to "shutdown", only shutdown logging will be WantAllTraces.
 // The default is none.
 //
 // MOZ_CC_RUN_DURING_SHUTDOWN: In non-DEBUG or builds, if this is set,
 // run cycle collections at shutdown.
 //
 // MOZ_CC_LOG_DIRECTORY: The directory in which logs are placed (such as
 // logs from MOZ_CC_LOG_ALL and MOZ_CC_LOG_SHUTDOWN, or other uses
 // of nsICycleCollectorListener)
 // Various parameters of this collector can be tuned using environment
 // variables.
 struct nsCycleCollectorParams
 {
     bool mLogAll;
     bool mLogShutdown;
     bool mAllTracesAll;
     bool mAllTracesShutdown;
     bool mLogThisThread;
     nsCycleCollectorParams() :
         mLogAll      (PR_GetEnv("MOZ_CC_LOG_ALL") != nullptr),
         mLogShutdown (PR_GetEnv("MOZ_CC_LOG_SHUTDOWN") != nullptr),
         mAllTracesAll(false),
         mAllTracesShutdown(false)
     {
         const char* logThreadEnv = PR_GetEnv("MOZ_CC_LOG_THREAD");
         bool threadLogging = true;
         if (logThreadEnv && !!strcmp(logThreadEnv, "all")) {
             if (NS_IsMainThread()) {
                 threadLogging = !strcmp(logThreadEnv, "main");
             } else {
                 threadLogging = !strcmp(logThreadEnv, "worker");
             }
         }
         const char* logProcessEnv = PR_GetEnv("MOZ_CC_LOG_PROCESS");
         bool processLogging = true;
         if (logProcessEnv && !!strcmp(logProcessEnv, "all")) {
             switch (XRE_GetProcessType()) {
                 case GeckoProcessType_Default:
                     processLogging = !strcmp(logProcessEnv, "main");
                     break;
                 case GeckoProcessType_Plugin:
                     processLogging = !strcmp(logProcessEnv, "plugins");
                     break;
                 case GeckoProcessType_Content:
                     processLogging = !strcmp(logProcessEnv, "content");
                     break;
                 default:
                     processLogging = false;
                     break;
             }
         }
         mLogThisThread = threadLogging && processLogging;
         const char* allTracesEnv = PR_GetEnv("MOZ_CC_ALL_TRACES");
         if (allTracesEnv) {
             if (!strcmp(allTracesEnv, "all")) {
                 mAllTracesAll = true;
             } else if (!strcmp(allTracesEnv, "shutdown")) {
                 mAllTracesShutdown = true;
             }
         }
     }
     bool LogThisCC(bool aIsShutdown)
     {
         return (mLogAll || (aIsShutdown && mLogShutdown)) && mLogThisThread;
     }
     bool AllTracesThisCC(bool aIsShutdown)
     {
         return mAllTracesAll || (aIsShutdown && mAllTracesShutdown);
     }
 };
 #ifdef COLLECT_TIME_DEBUG
 class TimeLog
 {
 public:
     TimeLog() : mLastCheckpoint(TimeStamp::Now()) {}
     void
     Checkpoint(const char* aEvent)
     {
         TimeStamp now = TimeStamp::Now();
         uint32_t dur = (uint32_t) ((now - mLastCheckpoint).ToMilliseconds());
         if (dur > 0) {
             printf("cc: %s took %dms\n", aEvent, dur);
         }
         mLastCheckpoint = now;
     }
 private:
     TimeStamp mLastCheckpoint;
 };
 #else
 class TimeLog
 {
 public:
     TimeLog() {}
     void Checkpoint(const char* aEvent) {}
 };
 #endif
 ////////////////////////////////////////////////////////////////////////
 // Base types
 ////////////////////////////////////////////////////////////////////////
 struct PtrInfo;
 class EdgePool
 {
 public:
     // EdgePool allocates arrays of void*, primarily to hold PtrInfo*.
     // However, at the end of a block, the last two pointers are a null
     // and then a void** pointing to the next block.  This allows
     // EdgePool::Iterators to be a single word but still capable of crossing
     // block boundaries.
     EdgePool()
     {
         mSentinelAndBlocks[0].block = nullptr;
         mSentinelAndBlocks[1].block = nullptr;
     }
     ~EdgePool()
     {
         MOZ_ASSERT(!mSentinelAndBlocks[0].block &&
                    !mSentinelAndBlocks[1].block,
                    "Didn't call Clear()?");
     }
     void Clear()
     {
         Block *b = Blocks();
         while (b) {
             Block *next = b->Next();
             delete b;
             b = next;
         }
         mSentinelAndBlocks[0].block = nullptr;
         mSentinelAndBlocks[1].block = nullptr;
     }
 #ifdef DEBUG
     bool IsEmpty()
     {
         return !mSentinelAndBlocks[0].block &&
                !mSentinelAndBlocks[1].block;
     }
 #endif
 private:
     struct Block;
     union PtrInfoOrBlock {
         // Use a union to avoid reinterpret_cast and the ensuing
         // potential aliasing bugs.
         PtrInfo *ptrInfo;
         Block *block;
     };
     struct Block {
         enum { BlockSize = 16 * 1024 };
         PtrInfoOrBlock mPointers[BlockSize];
         Block() {
             mPointers[BlockSize - 2].block = nullptr; // sentinel
             mPointers[BlockSize - 1].block = nullptr; // next block pointer
         }
         Block*& Next()          { return mPointers[BlockSize - 1].block; }
         PtrInfoOrBlock* Start() { return &mPointers[0]; }
         PtrInfoOrBlock* End()   { return &mPointers[BlockSize - 2]; }
     };
     // Store the null sentinel so that we can have valid iterators
     // before adding any edges and without adding any blocks.
     PtrInfoOrBlock mSentinelAndBlocks[2];
     Block*& Blocks()       { return mSentinelAndBlocks[1].block; }
     Block*  Blocks() const { return mSentinelAndBlocks[1].block; }
 public:
     class Iterator
     {
     public:
         Iterator() : mPointer(nullptr) {}
         Iterator(PtrInfoOrBlock *aPointer) : mPointer(aPointer) {}
         Iterator(const Iterator& aOther) : mPointer(aOther.mPointer) {}
         Iterator& operator++()
         {
             if (mPointer->ptrInfo == nullptr) {
                 // Null pointer is a sentinel for link to the next block.
                 mPointer = (mPointer + 1)->block->mPointers;
             }
             ++mPointer;
             return *this;
         }
         PtrInfo* operator*() const
         {
             if (mPointer->ptrInfo == nullptr) {
                 // Null pointer is a sentinel for link to the next block.
                 return (mPointer + 1)->block->mPointers->ptrInfo;
             }
             return mPointer->ptrInfo;
         }
         bool operator==(const Iterator& aOther) const
             { return mPointer == aOther.mPointer; }
         bool operator!=(const Iterator& aOther) const
             { return mPointer != aOther.mPointer; }
 #ifdef DEBUG_CC_GRAPH
         bool Initialized() const
         {
             return mPointer != nullptr;
         }
 #endif
     private:
         PtrInfoOrBlock *mPointer;
     };
     class Builder;
     friend class Builder;
     class Builder {
     public:
         Builder(EdgePool &aPool)
             : mCurrent(&aPool.mSentinelAndBlocks[0]),
               mBlockEnd(&aPool.mSentinelAndBlocks[0]),
               mNextBlockPtr(&aPool.Blocks())
         {
         }
         Iterator Mark() { return Iterator(mCurrent); }
         void Add(PtrInfo* aEdge) {
             if (mCurrent == mBlockEnd) {
                 Block *b = new Block();
                 *mNextBlockPtr = b;
                 mCurrent = b->Start();
                 mBlockEnd = b->End();
                 mNextBlockPtr = &b->Next();
             }
             (mCurrent++)->ptrInfo = aEdge;
         }
     private:
         // mBlockEnd points to space for null sentinel
         PtrInfoOrBlock *mCurrent, *mBlockEnd;
         Block **mNextBlockPtr;
     };
     size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
         size_t n = 0;
         Block *b = Blocks();
         while (b) {
             n += aMallocSizeOf(b);
             b = b->Next();
         }
         return n;
     }
 };
 #ifdef DEBUG_CC_GRAPH
 #define CC_GRAPH_ASSERT(b) MOZ_ASSERT(b)
 #else
 #define CC_GRAPH_ASSERT(b)
 #endif
 #define CC_TELEMETRY(_name, _value)                                            \
     PR_BEGIN_MACRO                                                             \
     if (NS_IsMainThread()) {                                                   \
       Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR##_name, _value);        \
     } else {                                                                   \
       Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_WORKER##_name, _value); \
     }                                                                          \
     PR_END_MACRO
 enum NodeColor { black, white, grey };
 // This structure should be kept as small as possible; we may expect
 // hundreds of thousands of them to be allocated and touched
 // repeatedly during each cycle collection.
 struct PtrInfo
 {
     void *mPointer;
     nsCycleCollectionParticipant *mParticipant;
     uint32_t mColor : 2;
     uint32_t mInternalRefs : 30;
     uint32_t mRefCount;
 private:
     EdgePool::Iterator mFirstChild;
 public:
     PtrInfo(void *aPointer, nsCycleCollectionParticipant *aParticipant)
         : mPointer(aPointer),
           mParticipant(aParticipant),
           mColor(grey),
           mInternalRefs(0),
           mRefCount(UINT32_MAX - 1),
           mFirstChild()
     {
         // We initialize mRefCount to a large non-zero value so
         // that it doesn't look like a JS object to the cycle collector
         // in the case where the object dies before being traversed.
         MOZ_ASSERT(aParticipant);
     }
     // Allow NodePool::Block's constructor to compile.
     PtrInfo() {
         NS_NOTREACHED("should never be called");
     }
     EdgePool::Iterator FirstChild()
     {
         CC_GRAPH_ASSERT(mFirstChild.Initialized());
         return mFirstChild;
     }
     // this PtrInfo must be part of a NodePool
     EdgePool::Iterator LastChild()
     {
         CC_GRAPH_ASSERT((this + 1)->mFirstChild.Initialized());
         return (this + 1)->mFirstChild;
     }
     void SetFirstChild(EdgePool::Iterator aFirstChild)
     {
         CC_GRAPH_ASSERT(aFirstChild.Initialized());
         mFirstChild = aFirstChild;
     }
     // this PtrInfo must be part of a NodePool
     void SetLastChild(EdgePool::Iterator aLastChild)
     {
         CC_GRAPH_ASSERT(aLastChild.Initialized());
         (this + 1)->mFirstChild = aLastChild;
     }
 };
 /**
  * A structure designed to be used like a linked list of PtrInfo, except
  * that allocates the PtrInfo 32K-at-a-time.
  */
 class NodePool
 {
 private:
     enum { BlockSize = 8 * 1024 }; // could be int template parameter
     struct Block {
         // We create and destroy Block using NS_Alloc/NS_Free rather
         // than new and delete to avoid calling its constructor and
         // destructor.
         Block()  { NS_NOTREACHED("should never be called"); }
         ~Block() { NS_NOTREACHED("should never be called"); }
         Block* mNext;
         PtrInfo mEntries[BlockSize + 1]; // +1 to store last child of last node
     };
 public:
     NodePool()
         : mBlocks(nullptr),
           mLast(nullptr)
     {
     }
     ~NodePool()
     {
         MOZ_ASSERT(!mBlocks, "Didn't call Clear()?");
     }
     void Clear()
     {
         Block *b = mBlocks;
         while (b) {
             Block *n = b->mNext;
             NS_Free(b);
             b = n;
         }
         mBlocks = nullptr;
         mLast = nullptr;
     }
 #ifdef DEBUG
     bool IsEmpty()
     {
         return !mBlocks && !mLast;
     }
 #endif
     class Builder;
     friend class Builder;
     class Builder {
     public:
         Builder(NodePool& aPool)
             : mNextBlock(&aPool.mBlocks),
               mNext(aPool.mLast),
               mBlockEnd(nullptr)
         {
             MOZ_ASSERT(aPool.mBlocks == nullptr && aPool.mLast == nullptr,
                        "pool not empty");
         }
         PtrInfo *Add(void *aPointer, nsCycleCollectionParticipant *aParticipant)
         {
             if (mNext == mBlockEnd) {
                 Block *block = static_cast<Block*>(NS_Alloc(sizeof(Block)));
                 *mNextBlock = block;
                 mNext = block->mEntries;
                 mBlockEnd = block->mEntries + BlockSize;
                 block->mNext = nullptr;
                 mNextBlock = &block->mNext;
             }
             return new (mNext++) PtrInfo(aPointer, aParticipant);
         }
     private:
         Block **mNextBlock;
         PtrInfo *&mNext;
         PtrInfo *mBlockEnd;
     };
     class Enumerator;
     friend class Enumerator;
     class Enumerator {
     public:
         Enumerator(NodePool& aPool)
             : mFirstBlock(aPool.mBlocks),
               mCurBlock(nullptr),
               mNext(nullptr),
               mBlockEnd(nullptr),
               mLast(aPool.mLast)
         {
         }
         bool IsDone() const
         {
             return mNext == mLast;
         }
         bool AtBlockEnd() const
         {
             return mNext == mBlockEnd;
         }
         PtrInfo* GetNext()
         {
             MOZ_ASSERT(!IsDone(), "calling GetNext when done");
             if (mNext == mBlockEnd) {
                 Block *nextBlock = mCurBlock ? mCurBlock->mNext : mFirstBlock;
                 mNext = nextBlock->mEntries;
                 mBlockEnd = mNext + BlockSize;
                 mCurBlock = nextBlock;
             }
             return mNext++;
         }
     private:
         // mFirstBlock is a reference to allow an Enumerator to be constructed
         // for an empty graph.
         Block *&mFirstBlock;
         Block *mCurBlock;
         // mNext is the next value we want to return, unless mNext == mBlockEnd
         // NB: mLast is a reference to allow enumerating while building!
         PtrInfo *mNext, *mBlockEnd, *&mLast;
     };
     size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
         // We don't measure the things pointed to by mEntries[] because those
         // pointers are non-owning.
         size_t n = 0;
         Block *b = mBlocks;
         while (b) {
             n += aMallocSizeOf(b);
             b = b->mNext;
         }
         return n;
     }
 private:
     Block *mBlocks;
     PtrInfo *mLast;
 };
 // Declarations for mPtrToNodeMap.
 struct PtrToNodeEntry : public PLDHashEntryHdr
 {
     // The key is mNode->mPointer
     PtrInfo *mNode;
 };
 static bool
 PtrToNodeMatchEntry(PLDHashTable *table,
                     const PLDHashEntryHdr *entry,
                     const void *key)
 {
     const PtrToNodeEntry *n = static_cast<const PtrToNodeEntry*>(entry);
     return n->mNode->mPointer == key;
 }
 static PLDHashTableOps PtrNodeOps = {
     PL_DHashAllocTable,
     PL_DHashFreeTable,
     PL_DHashVoidPtrKeyStub,
     PtrToNodeMatchEntry,
     PL_DHashMoveEntryStub,
     PL_DHashClearEntryStub,
     PL_DHashFinalizeStub,
     nullptr
 };
 struct WeakMapping
 {
     // map and key will be null if the corresponding objects are GC marked
     PtrInfo *mMap;
     PtrInfo *mKey;
     PtrInfo *mKeyDelegate;
     PtrInfo *mVal;
 };
 class GCGraphBuilder;
 struct GCGraph
 {
     NodePool mNodes;
     EdgePool mEdges;
     nsTArray<WeakMapping> mWeakMaps;
     uint32_t mRootCount;
 private:
     PLDHashTable mPtrToNodeMap;
 public:
     GCGraph() : mRootCount(0)
     {
         mPtrToNodeMap.ops = nullptr;
     }
     ~GCGraph()
     {
         if (mPtrToNodeMap.ops) {
             PL_DHashTableFinish(&mPtrToNodeMap);
         }
     }
     void Init()
     {
         MOZ_ASSERT(IsEmpty(), "Failed to call GCGraph::Clear");
         PL_DHashTableInit(&mPtrToNodeMap, &PtrNodeOps, nullptr,
                           sizeof(PtrToNodeEntry), 32768);
     }
     void Clear()
     {
         mNodes.Clear();
         mEdges.Clear();
         mWeakMaps.Clear();
         mRootCount = 0;
         PL_DHashTableFinish(&mPtrToNodeMap);
         mPtrToNodeMap.ops = nullptr;
     }
 #ifdef DEBUG
     bool IsEmpty()
     {
         return mNodes.IsEmpty() && mEdges.IsEmpty() &&
             mWeakMaps.IsEmpty() && mRootCount == 0 &&
             !mPtrToNodeMap.ops;
     }
 #endif
     PtrInfo* FindNode(void *aPtr);
     PtrToNodeEntry* AddNodeToMap(void *aPtr);
     void RemoveNodeFromMap(void *aPtr);
     uint32_t MapCount() const
     {
         return mPtrToNodeMap.entryCount;
     }
     void SizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
                              size_t *aNodesSize, size_t *aEdgesSize,
                              size_t *aWeakMapsSize) const {
         *aNodesSize = mNodes.SizeOfExcludingThis(aMallocSizeOf);
         *aEdgesSize = mEdges.SizeOfExcludingThis(aMallocSizeOf);
         // We don't measure what the WeakMappings point to, because the
         // pointers are non-owning.
         *aWeakMapsSize = mWeakMaps.SizeOfExcludingThis(aMallocSizeOf);
     }
 };
 PtrInfo*
 GCGraph::FindNode(void *aPtr)
 {
     PtrToNodeEntry *e = static_cast<PtrToNodeEntry*>(PL_DHashTableOperate(&mPtrToNodeMap, aPtr, PL_DHASH_LOOKUP));
     if (!PL_DHASH_ENTRY_IS_BUSY(e)) {
         return nullptr;
     }
     return e->mNode;
 }
 PtrToNodeEntry*
 GCGraph::AddNodeToMap(void *aPtr)
 {
     PtrToNodeEntry *e = static_cast<PtrToNodeEntry*>(PL_DHashTableOperate(&mPtrToNodeMap, aPtr, PL_DHASH_ADD));
     if (!e) {
         // Caller should track OOMs
         return nullptr;
     }
     return e;
 }
 void
 GCGraph::RemoveNodeFromMap(void *aPtr)
 {
     PL_DHashTableOperate(&mPtrToNodeMap, aPtr, PL_DHASH_REMOVE);
 }
 static nsISupports *
 CanonicalizeXPCOMParticipant(nsISupports *in)
 {
     nsISupports* out;
     in->QueryInterface(NS_GET_IID(nsCycleCollectionISupports),
                        reinterpret_cast<void**>(&out));
     return out;
 }
 static inline void
 ToParticipant(nsISupports *s, nsXPCOMCycleCollectionParticipant **cp);
 static void
 CanonicalizeParticipant(void **parti, nsCycleCollectionParticipant **cp)
 {
     // If the participant is null, this is an nsISupports participant,
     // so we must QI to get the real participant.
     if (!*cp) {
         nsISupports *nsparti = static_cast<nsISupports*>(*parti);
         nsparti = CanonicalizeXPCOMParticipant(nsparti);
         NS_ASSERTION(nsparti,
                      "Don't add objects that don't participate in collection!");
         nsXPCOMCycleCollectionParticipant *xcp;
         ToParticipant(nsparti, &xcp);
         *parti = nsparti;
         *cp = xcp;
     }
 }
 struct nsPurpleBufferEntry {
   union {
     void *mObject;                        // when low bit unset
     nsPurpleBufferEntry *mNextInFreeList; // when low bit set
   };
   nsCycleCollectingAutoRefCnt *mRefCnt;
   nsCycleCollectionParticipant *mParticipant; // nullptr for nsISupports
 };
 class nsCycleCollector;
 struct nsPurpleBuffer
 {
 private:
     struct Block {
         Block *mNext;
         // Try to match the size of a jemalloc bucket, to minimize slop bytes.
         // - On 32-bit platforms sizeof(nsPurpleBufferEntry) is 12, so mEntries
         //   is 16,380 bytes, which leaves 4 bytes for mNext.
         // - On 64-bit platforms sizeof(nsPurpleBufferEntry) is 24, so mEntries
         //   is 32,544 bytes, which leaves 8 bytes for mNext.
         nsPurpleBufferEntry mEntries[1365];
         Block() : mNext(nullptr) {
             // Ensure Block is the right size (see above).
             static_assert(
                 sizeof(Block) == 16384 ||       // 32-bit
                 sizeof(Block) == 32768,         // 64-bit
                 "ill-sized nsPurpleBuffer::Block"
             );
         }
         template <class PurpleVisitor>
         void VisitEntries(nsPurpleBuffer &aBuffer, PurpleVisitor &aVisitor)
         {
             nsPurpleBufferEntry *eEnd = ArrayEnd(mEntries);
             for (nsPurpleBufferEntry *e = mEntries; e != eEnd; ++e) {
                 if (!(uintptr_t(e->mObject) & uintptr_t(1))) {
                     aVisitor.Visit(aBuffer, e);
                 }
             }
         }
     };
     // This class wraps a linked list of the elements in the purple
     // buffer.
     uint32_t mCount;
     Block mFirstBlock;
     nsPurpleBufferEntry *mFreeList;
 public:
     nsPurpleBuffer()
     {
         InitBlocks();
     }
     ~nsPurpleBuffer()
     {
         FreeBlocks();
     }
     template <class PurpleVisitor>
     void VisitEntries(PurpleVisitor &aVisitor)
     {
         for (Block *b = &mFirstBlock; b; b = b->mNext) {
             b->VisitEntries(*this, aVisitor);
         }
     }
     void InitBlocks()
     {
         mCount = 0;
         mFreeList = nullptr;
         StartBlock(&mFirstBlock);
     }
     void StartBlock(Block *aBlock)
     {
         NS_ABORT_IF_FALSE(!mFreeList, "should not have free list");
         // Put all the entries in the block on the free list.
         nsPurpleBufferEntry *entries = aBlock->mEntries;
         mFreeList = entries;
         for (uint32_t i = 1; i < ArrayLength(aBlock->mEntries); ++i) {
             entries[i - 1].mNextInFreeList =
                 (nsPurpleBufferEntry*)(uintptr_t(entries + i) | 1);
         }
         entries[ArrayLength(aBlock->mEntries) - 1].mNextInFreeList =
             (nsPurpleBufferEntry*)1;
     }
     void FreeBlocks()
     {
         if (mCount > 0)
             UnmarkRemainingPurple(&mFirstBlock);
         Block *b = mFirstBlock.mNext;
         while (b) {
             if (mCount > 0)
                 UnmarkRemainingPurple(b);
             Block *next = b->mNext;
             delete b;
             b = next;
         }
         mFirstBlock.mNext = nullptr;
     }
     struct UnmarkRemainingPurpleVisitor
     {
         void
         Visit(nsPurpleBuffer &aBuffer, nsPurpleBufferEntry *aEntry)
         {
             if (aEntry->mRefCnt) {
                 aEntry->mRefCnt->RemoveFromPurpleBuffer();
                 aEntry->mRefCnt = nullptr;
             }
             aEntry->mObject = nullptr;
             --aBuffer.mCount;
         }
     };
     void UnmarkRemainingPurple(Block *b)
     {
         UnmarkRemainingPurpleVisitor visitor;
         b->VisitEntries(*this, visitor);
     }
     void SelectPointers(GCGraphBuilder &builder);
     // RemoveSkippable removes entries from the purple buffer synchronously
     // (1) if aAsyncSnowWhiteFreeing is false and nsPurpleBufferEntry::mRefCnt is 0 or
     // (2) if the object's nsXPCOMCycleCollectionParticipant::CanSkip() returns true or
     // (3) if nsPurpleBufferEntry::mRefCnt->IsPurple() is false.
     // (4) If removeChildlessNodes is true, then any nodes in the purple buffer
     //     that will have no children in the cycle collector graph will also be
     //     removed. CanSkip() may be run on these children.
     void RemoveSkippable(nsCycleCollector* aCollector,
                          bool removeChildlessNodes,
                          bool aAsyncSnowWhiteFreeing,
                          CC_ForgetSkippableCallback aCb);
     MOZ_ALWAYS_INLINE nsPurpleBufferEntry* NewEntry()
     {
         if (MOZ_UNLIKELY(!mFreeList)) {
             Block *b = new Block;
             StartBlock(b);
             // Add the new block as the second block in the list.
             b->mNext = mFirstBlock.mNext;
             mFirstBlock.mNext = b;
         }
         nsPurpleBufferEntry *e = mFreeList;
         mFreeList = (nsPurpleBufferEntry*)
             (uintptr_t(mFreeList->mNextInFreeList) & ~uintptr_t(1));
         return e;
     }
     MOZ_ALWAYS_INLINE void Put(void *p, nsCycleCollectionParticipant *cp,
                                nsCycleCollectingAutoRefCnt *aRefCnt)
     {
         nsPurpleBufferEntry *e = NewEntry();
         ++mCount;
         e->mObject = p;
         e->mRefCnt = aRefCnt;
         e->mParticipant = cp;
     }
     void Remove(nsPurpleBufferEntry *e)
     {
         MOZ_ASSERT(mCount != 0, "must have entries");
         if (e->mRefCnt) {
             e->mRefCnt->RemoveFromPurpleBuffer();
             e->mRefCnt = nullptr;
         }
         e->mNextInFreeList =
             (nsPurpleBufferEntry*)(uintptr_t(mFreeList) | uintptr_t(1));
         mFreeList = e;
         --mCount;
     }
     uint32_t Count() const
     {
         return mCount;
     }
     size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
     {
         size_t n = 0;
         // Don't measure mFirstBlock because it's within |this|.
         const Block *block = mFirstBlock.mNext;
         while (block) {
             n += aMallocSizeOf(block);
             block = block->mNext;
         }
         // mFreeList is deliberately not measured because it points into
         // the purple buffer, which is within mFirstBlock and thus within |this|.
         //
         // We also don't measure the things pointed to by mEntries[] because
         // those pointers are non-owning.
         return n;
     }
 };
 static bool
 AddPurpleRoot(GCGraphBuilder &aBuilder, void *aRoot, nsCycleCollectionParticipant *aParti);
 struct SelectPointersVisitor
 {
     SelectPointersVisitor(GCGraphBuilder &aBuilder)
         : mBuilder(aBuilder)
     {}
     void
     Visit(nsPurpleBuffer &aBuffer, nsPurpleBufferEntry *aEntry)
     {
         MOZ_ASSERT(aEntry->mObject, "Null object in purple buffer");
         MOZ_ASSERT(aEntry->mRefCnt->get() != 0,
                    "SelectPointersVisitor: snow-white object in the purple buffer");
         if (!aEntry->mRefCnt->IsPurple() ||
             AddPurpleRoot(mBuilder, aEntry->mObject, aEntry->mParticipant)) {
             aBuffer.Remove(aEntry);
         }
     }
 private:
     GCGraphBuilder &mBuilder;
 };
 void
 nsPurpleBuffer::SelectPointers(GCGraphBuilder &aBuilder)
 {
     SelectPointersVisitor visitor(aBuilder);
     VisitEntries(visitor);
     NS_ASSERTION(mCount == 0, "AddPurpleRoot failed");
     if (mCount == 0) {
         FreeBlocks();
         InitBlocks();
     }
 }
 enum ccPhase {
     IdlePhase,
     GraphBuildingPhase,
     ScanAndCollectWhitePhase,
     CleanupPhase
 };
 enum ccType {
     SliceCC,     /* If a CC is in progress, continue it. Otherwise, start a new one. */
     ManualCC,    /* Explicitly triggered. */
     ShutdownCC   /* Shutdown CC, used for finding leaks. */
 };
 #ifdef MOZ_NUWA_PROCESS
 #include "ipc/Nuwa.h"
 #endif
 ////////////////////////////////////////////////////////////////////////
 // Top level structure for the cycle collector.
 ////////////////////////////////////////////////////////////////////////
 typedef js::SliceBudget SliceBudget;
 class JSPurpleBuffer;
 class nsCycleCollector : public nsIMemoryReporter
 {
     NS_DECL_ISUPPORTS
     NS_DECL_NSIMEMORYREPORTER
     bool mActivelyCollecting;
     bool mFreeingSnowWhite;
     // mScanInProgress should be false when we're collecting white objects.
     bool mScanInProgress;
     CycleCollectorResults mResults;
     TimeStamp mCollectionStart;
     CycleCollectedJSRuntime *mJSRuntime;
     ccPhase mIncrementalPhase;
     GCGraph mGraph;
     nsAutoPtr<GCGraphBuilder> mBuilder;
     nsAutoPtr<NodePool::Enumerator> mCurrNode;
     nsCOMPtr<nsICycleCollectorListener> mListener;
     nsIThread* mThread;
     nsCycleCollectorParams mParams;
     uint32_t mWhiteNodeCount;
     CC_BeforeUnlinkCallback mBeforeUnlinkCB;
     CC_ForgetSkippableCallback mForgetSkippableCB;
     nsPurpleBuffer mPurpleBuf;
     uint32_t mUnmergedNeeded;
     uint32_t mMergedInARow;
     JSPurpleBuffer* mJSPurpleBuffer;
 public:
     nsCycleCollector();
     virtual ~nsCycleCollector();
     void RegisterJSRuntime(CycleCollectedJSRuntime *aJSRuntime);
     void ForgetJSRuntime();
     void SetBeforeUnlinkCallback(CC_BeforeUnlinkCallback aBeforeUnlinkCB)
     {
         CheckThreadSafety();
         mBeforeUnlinkCB = aBeforeUnlinkCB;
     }
     void SetForgetSkippableCallback(CC_ForgetSkippableCallback aForgetSkippableCB)
     {
         CheckThreadSafety();
         mForgetSkippableCB = aForgetSkippableCB;
     }
     void Suspect(void *n, nsCycleCollectionParticipant *cp,
                  nsCycleCollectingAutoRefCnt *aRefCnt);
     uint32_t SuspectedCount();
     void ForgetSkippable(bool aRemoveChildlessNodes, bool aAsyncSnowWhiteFreeing);
     bool FreeSnowWhite(bool aUntilNoSWInPurpleBuffer);
     // This method assumes its argument is already canonicalized.
     void RemoveObjectFromGraph(void *aPtr);
     void PrepareForGarbageCollection();
     bool Collect(ccType aCCType,
                  SliceBudget &aBudget,
                  nsICycleCollectorListener *aManualListener);
     void Shutdown();
     void SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf,
                              size_t *aObjectSize,
                              size_t *aGraphNodesSize,
                              size_t *aGraphEdgesSize,
                              size_t *aWeakMapsSize,
                              size_t *aPurpleBufferSize) const;
     JSPurpleBuffer* GetJSPurpleBuffer();
 private:
     void CheckThreadSafety();
     void ShutdownCollect();
     void FixGrayBits(bool aForceGC);
     bool ShouldMergeZones(ccType aCCType);
     void BeginCollection(ccType aCCType, nsICycleCollectorListener *aManualListener);
     void MarkRoots(SliceBudget &aBudget);
     void ScanRoots(bool aFullySynchGraphBuild);
     void ScanIncrementalRoots();
     void ScanWeakMaps();
     // returns whether anything was collected
     bool CollectWhite();
     void CleanupAfterCollection();
 };
 NS_IMPL_ISUPPORTS(nsCycleCollector, nsIMemoryReporter)
 /**
  * GraphWalker is templatized over a Visitor class that must provide
  * the following two methods:
  *
  * bool ShouldVisitNode(PtrInfo const *pi);
  * void VisitNode(PtrInfo *pi);
  */
 template <class Visitor>
 class GraphWalker
 {
 private:
     Visitor mVisitor;
     void DoWalk(nsDeque &aQueue);
     void CheckedPush(nsDeque &aQueue, PtrInfo *pi)
     {
         if (!pi) {
             MOZ_CRASH();
         }
         if (!aQueue.Push(pi, fallible_t())) {
             mVisitor.Failed();
         }
     }
 public:
     void Walk(PtrInfo *s0);
     void WalkFromRoots(GCGraph &aGraph);
     // copy-constructing the visitor should be cheap, and less
     // indirection than using a reference
     GraphWalker(const Visitor aVisitor) : mVisitor(aVisitor) {}
 };
 ////////////////////////////////////////////////////////////////////////
 // The static collector struct
 ////////////////////////////////////////////////////////////////////////
 struct CollectorData {
   nsRefPtr<nsCycleCollector> mCollector;
   CycleCollectedJSRuntime* mRuntime;
 };
 static mozilla::ThreadLocal<CollectorData*> sCollectorData;
 ////////////////////////////////////////////////////////////////////////
 // Utility functions
 ////////////////////////////////////////////////////////////////////////
 MOZ_NEVER_INLINE static void
 Fault(const char *msg, const void *ptr=nullptr)
 {
     if (ptr)
         printf("Fault in cycle collector: %s (ptr: %p)\n", msg, ptr);
     else
         printf("Fault in cycle collector: %s\n", msg);
     NS_RUNTIMEABORT("cycle collector fault");
 }
 static void
 Fault(const char *msg, PtrInfo *pi)
 {
     Fault(msg, pi->mPointer);
 }
 static inline void
 ToParticipant(nsISupports *s, nsXPCOMCycleCollectionParticipant **cp)
 {
     // We use QI to move from an nsISupports to an
     // nsXPCOMCycleCollectionParticipant, which is a per-class singleton helper
     // object that implements traversal and unlinking logic for the nsISupports
     // in question.
     CallQueryInterface(s, cp);
 }
 template <class Visitor>
 MOZ_NEVER_INLINE void
 GraphWalker<Visitor>::Walk(PtrInfo *s0)
 {
     nsDeque queue;
     CheckedPush(queue, s0);
     DoWalk(queue);
 }
 template <class Visitor>
 MOZ_NEVER_INLINE void
 GraphWalker<Visitor>::WalkFromRoots(GCGraph& aGraph)
 {
     nsDeque queue;
     NodePool::Enumerator etor(aGraph.mNodes);
     for (uint32_t i = 0; i < aGraph.mRootCount; ++i) {
         CheckedPush(queue, etor.GetNext());
     }
     DoWalk(queue);
 }
 template <class Visitor>
 MOZ_NEVER_INLINE void
 GraphWalker<Visitor>::DoWalk(nsDeque &aQueue)
 {
     // Use a aQueue to match the breadth-first traversal used when we
     // built the graph, for hopefully-better locality.
     while (aQueue.GetSize() > 0) {
         PtrInfo *pi = static_cast<PtrInfo*>(aQueue.PopFront());
         if (pi->mParticipant && mVisitor.ShouldVisitNode(pi)) {
             mVisitor.VisitNode(pi);
             for (EdgePool::Iterator child = pi->FirstChild(),
                                 child_end = pi->LastChild();
                  child != child_end; ++child) {
                 CheckedPush(aQueue, *child);
             }
         }
     }
 }
 struct CCGraphDescriber : public LinkedListElement<CCGraphDescriber>
 {
   CCGraphDescriber()
   : mAddress("0x"), mCnt(0), mType(eUnknown) {}
   enum Type
   {
     eRefCountedObject,
     eGCedObject,
     eGCMarkedObject,
     eEdge,
     eRoot,
     eGarbage,
     eUnknown
   };
   nsCString mAddress;
   nsCString mName;
   nsCString mCompartmentOrToAddress;
   uint32_t mCnt;
   Type mType;
 };
 class nsCycleCollectorLogger MOZ_FINAL : public nsICycleCollectorListener
 {
 public:
     nsCycleCollectorLogger() :
       mStream(nullptr), mWantAllTraces(false),
       mDisableLog(false), mWantAfterProcessing(false)
     {
     }
     ~nsCycleCollectorLogger()
     {
         ClearDescribers();
         if (mStream) {
             MozillaUnRegisterDebugFILE(mStream);
             fclose(mStream);
         }
     }
     NS_DECL_ISUPPORTS
     void SetAllTraces()
     {
         mWantAllTraces = true;
     }
     NS_IMETHOD AllTraces(nsICycleCollectorListener** aListener)
     {
         SetAllTraces();
         NS_ADDREF(*aListener = this);
         return NS_OK;
     }
     NS_IMETHOD GetWantAllTraces(bool* aAllTraces)
     {
         *aAllTraces = mWantAllTraces;
         return NS_OK;
     }
     NS_IMETHOD GetDisableLog(bool* aDisableLog)
     {
         *aDisableLog = mDisableLog;
         return NS_OK;
     }
     NS_IMETHOD SetDisableLog(bool aDisableLog)
     {
         mDisableLog = aDisableLog;
         return NS_OK;
     }
     NS_IMETHOD GetWantAfterProcessing(bool* aWantAfterProcessing)
     {
         *aWantAfterProcessing = mWantAfterProcessing;
         return NS_OK;
     }
     NS_IMETHOD SetWantAfterProcessing(bool aWantAfterProcessing)
     {
         mWantAfterProcessing = aWantAfterProcessing;
         return NS_OK;
     }
     NS_IMETHOD GetFilenameIdentifier(nsAString& aIdentifier)
     {
         aIdentifier = mFilenameIdentifier;
         return NS_OK;
     }
     NS_IMETHOD SetFilenameIdentifier(const nsAString& aIdentifier)
     {
         mFilenameIdentifier = aIdentifier;
         return NS_OK;
     }
     NS_IMETHOD GetGcLogPath(nsAString &aPath)
     {
       aPath = mGCLogPath;
       return NS_OK;
     }
     NS_IMETHOD GetCcLogPath(nsAString &aPath)
     {
       aPath = mCCLogPath;
       return NS_OK;
     }
     NS_IMETHOD Begin()
     {
         mCurrentAddress.AssignLiteral("0x");
         ClearDescribers();
         if (mDisableLog) {
             return NS_OK;
         }
         // Initially create the log in a file starting with
         // "incomplete-gc-edges".  We'll move the file and strip off the
         // "incomplete-" once the dump completes.  (We do this because we don't
         // want scripts which poll the filesystem looking for gc/cc dumps to
         // grab a file before we're finished writing to it.)
         nsCOMPtr<nsIFile> gcLogFile = CreateTempFile("incomplete-gc-edges");
         if (NS_WARN_IF(!gcLogFile))
             return NS_ERROR_UNEXPECTED;
         // Dump the JS heap.
         FILE* gcLogANSIFile = nullptr;
         gcLogFile->OpenANSIFileDesc("w", &gcLogANSIFile);
         if (NS_WARN_IF(!gcLogANSIFile))
             return NS_ERROR_UNEXPECTED;
         MozillaRegisterDebugFILE(gcLogANSIFile);
         CollectorData *data = sCollectorData.get();
         if (data && data->mRuntime)
             data->mRuntime->DumpJSHeap(gcLogANSIFile);
         MozillaUnRegisterDebugFILE(gcLogANSIFile);
         fclose(gcLogANSIFile);
         // Strip off "incomplete-".
         nsCOMPtr<nsIFile> gcLogFileFinalDestination =
             CreateTempFile("gc-edges");
         if (NS_WARN_IF(!gcLogFileFinalDestination))
             return NS_ERROR_UNEXPECTED;
         nsAutoString gcLogFileFinalDestinationName;
         gcLogFileFinalDestination->GetLeafName(gcLogFileFinalDestinationName);
         if (NS_WARN_IF(gcLogFileFinalDestinationName.IsEmpty()))
             return NS_ERROR_UNEXPECTED;
         gcLogFile->MoveTo(/* directory */ nullptr, gcLogFileFinalDestinationName);
         // Log to the error console.
         nsCOMPtr<nsIConsoleService> cs =
             do_GetService(NS_CONSOLESERVICE_CONTRACTID);
         if (cs) {
             nsAutoString gcLogPath;
             gcLogFileFinalDestination->GetPath(gcLogPath);
             nsString msg = NS_LITERAL_STRING("Garbage Collector log dumped to ") +
                            gcLogPath;
             cs->LogStringMessage(msg.get());
             mGCLogPath = gcLogPath;
         }
         // Open a file for dumping the CC graph.  We again prefix with
         // "incomplete-".
         mOutFile = CreateTempFile("incomplete-cc-edges");
         if (NS_WARN_IF(!mOutFile))
             return NS_ERROR_UNEXPECTED;
         MOZ_ASSERT(!mStream);
         mOutFile->OpenANSIFileDesc("w", &mStream);
         if (NS_WARN_IF(!mStream))
             return NS_ERROR_UNEXPECTED;
         MozillaRegisterDebugFILE(mStream);
         fprintf(mStream, "# WantAllTraces=%s\n", mWantAllTraces ? "true" : "false");
         return NS_OK;
     }
     NS_IMETHOD NoteRefCountedObject(uint64_t aAddress, uint32_t refCount,
                                     const char *aObjectDescription)
     {
         if (!mDisableLog) {
             fprintf(mStream, "%p [rc=%u] %s\n", (void*)aAddress, refCount,
                     aObjectDescription);
         }
         if (mWantAfterProcessing) {
             CCGraphDescriber* d =  new CCGraphDescriber();
             mDescribers.insertBack(d);
             mCurrentAddress.AssignLiteral("0x");
             mCurrentAddress.AppendInt(aAddress, 16);
             d->mType = CCGraphDescriber::eRefCountedObject;
             d->mAddress = mCurrentAddress;
             d->mCnt = refCount;
             d->mName.Append(aObjectDescription);
         }
         return NS_OK;
     }
     NS_IMETHOD NoteGCedObject(uint64_t aAddress, bool aMarked,
                               const char *aObjectDescription,
                               uint64_t aCompartmentAddress)
     {
         if (!mDisableLog) {
             fprintf(mStream, "%p [gc%s] %s\n", (void*)aAddress,
                     aMarked ? ".marked" : "", aObjectDescription);
         }
         if (mWantAfterProcessing) {
             CCGraphDescriber* d =  new CCGraphDescriber();
             mDescribers.insertBack(d);
             mCurrentAddress.AssignLiteral("0x");
             mCurrentAddress.AppendInt(aAddress, 16);
             d->mType = aMarked ? CCGraphDescriber::eGCMarkedObject :
                                  CCGraphDescriber::eGCedObject;
             d->mAddress = mCurrentAddress;
             d->mName.Append(aObjectDescription);
             if (aCompartmentAddress) {
                 d->mCompartmentOrToAddress.AssignLiteral("0x");
                 d->mCompartmentOrToAddress.AppendInt(aCompartmentAddress, 16);
             } else {
                 d->mCompartmentOrToAddress.SetIsVoid(true);
             }
         }
         return NS_OK;
     }
     NS_IMETHOD NoteEdge(uint64_t aToAddress, const char *aEdgeName)
     {
         if (!mDisableLog) {
             fprintf(mStream, "> %p %s\n", (void*)aToAddress, aEdgeName);
         }
         if (mWantAfterProcessing) {
             CCGraphDescriber* d =  new CCGraphDescriber();
             mDescribers.insertBack(d);
             d->mType = CCGraphDescriber::eEdge;
             d->mAddress = mCurrentAddress;
             d->mCompartmentOrToAddress.AssignLiteral("0x");
             d->mCompartmentOrToAddress.AppendInt(aToAddress, 16);
             d->mName.Append(aEdgeName);
         }
         return NS_OK;
     }
     NS_IMETHOD NoteWeakMapEntry(uint64_t aMap, uint64_t aKey,
                                 uint64_t aKeyDelegate, uint64_t aValue)
     {
         if (!mDisableLog) {
             fprintf(mStream, "WeakMapEntry map=%p key=%p keyDelegate=%p value=%p\n",
                     (void*)aMap, (void*)aKey, (void*)aKeyDelegate, (void*)aValue);
         }
         // We don't support after-processing for weak map entries.
         return NS_OK;
     }
     NS_IMETHOD NoteIncrementalRoot(uint64_t aAddress)
     {
         if (!mDisableLog) {
             fprintf(mStream, "IncrementalRoot %p\n", (void*)aAddress);
         }
         // We don't support after-processing for incremental roots.
         return NS_OK;
     }
     NS_IMETHOD BeginResults()
     {
         if (!mDisableLog) {
             fputs("==========\n", mStream);
         }
         return NS_OK;
     }
     NS_IMETHOD DescribeRoot(uint64_t aAddress, uint32_t aKnownEdges)
     {
         if (!mDisableLog) {
             fprintf(mStream, "%p [known=%u]\n", (void*)aAddress, aKnownEdges);
         }
         if (mWantAfterProcessing) {
             CCGraphDescriber* d =  new CCGraphDescriber();
             mDescribers.insertBack(d);
             d->mType = CCGraphDescriber::eRoot;
             d->mAddress.AppendInt(aAddress, 16);
             d->mCnt = aKnownEdges;
         }
         return NS_OK;
     }
     NS_IMETHOD DescribeGarbage(uint64_t aAddress)
     {
         if (!mDisableLog) {
             fprintf(mStream, "%p [garbage]\n", (void*)aAddress);
         }
         if (mWantAfterProcessing) {
             CCGraphDescriber* d =  new CCGraphDescriber();
             mDescribers.insertBack(d);
             d->mType = CCGraphDescriber::eGarbage;
             d->mAddress.AppendInt(aAddress, 16);
         }
         return NS_OK;
     }
     NS_IMETHOD End()
     {
         if (!mDisableLog) {
             MOZ_ASSERT(mStream);
             MOZ_ASSERT(mOutFile);
             MozillaUnRegisterDebugFILE(mStream);
             fclose(mStream);
             mStream = nullptr;
             // Strip off "incomplete-" from the log file's name.
             nsCOMPtr<nsIFile> logFileFinalDestination =
                 CreateTempFile("cc-edges");
             if (NS_WARN_IF(!logFileFinalDestination))
                 return NS_ERROR_UNEXPECTED;
             nsAutoString logFileFinalDestinationName;
             logFileFinalDestination->GetLeafName(logFileFinalDestinationName);
             if (NS_WARN_IF(logFileFinalDestinationName.IsEmpty()))
                 return NS_ERROR_UNEXPECTED;
             mOutFile->MoveTo(/* directory = */ nullptr,
                              logFileFinalDestinationName);
             mOutFile = nullptr;
             // Log to the error console.
             nsCOMPtr<nsIConsoleService> cs =
                 do_GetService(NS_CONSOLESERVICE_CONTRACTID);
             if (cs) {
                 nsAutoString ccLogPath;
                 logFileFinalDestination->GetPath(ccLogPath);
                 nsString msg = NS_LITERAL_STRING("Cycle Collector log dumped to ") +
                                ccLogPath;
                 cs->LogStringMessage(msg.get());
                 mCCLogPath = ccLogPath;
             }
         }
         return NS_OK;
     }
     NS_IMETHOD ProcessNext(nsICycleCollectorHandler* aHandler,
                            bool* aCanContinue)
     {
         if (NS_WARN_IF(!aHandler) || NS_WARN_IF(!mWantAfterProcessing))
             return NS_ERROR_UNEXPECTED;
         CCGraphDescriber* d = mDescribers.popFirst();
         if (d) {
             switch (d->mType) {
                 case CCGraphDescriber::eRefCountedObject:
                     aHandler->NoteRefCountedObject(d->mAddress,
                                                    d->mCnt,
                                                    d->mName);
                     break;
                 case CCGraphDescriber::eGCedObject:
                 case CCGraphDescriber::eGCMarkedObject:
                     aHandler->NoteGCedObject(d->mAddress,
                                              d->mType ==
                                                CCGraphDescriber::eGCMarkedObject,
                                              d->mName,
                                              d->mCompartmentOrToAddress);
                     break;
                 case CCGraphDescriber::eEdge:
                     aHandler->NoteEdge(d->mAddress,
                                        d->mCompartmentOrToAddress,
                                        d->mName);
                     break;
                 case CCGraphDescriber::eRoot:
                     aHandler->DescribeRoot(d->mAddress,
                                            d->mCnt);
                     break;
                 case CCGraphDescriber::eGarbage:
                     aHandler->DescribeGarbage(d->mAddress);
                     break;
                 case CCGraphDescriber::eUnknown:
                     NS_NOTREACHED("CCGraphDescriber::eUnknown");
                     break;
             }
             delete d;
         }
         if (!(*aCanContinue = !mDescribers.isEmpty())) {
             mCurrentAddress.AssignLiteral("0x");
         }
         return NS_OK;
     }
 private:
     /**
      * Create a new file named something like aPrefix.$PID.$IDENTIFIER.log in
      * $MOZ_CC_LOG_DIRECTORY or in the system's temp directory.  No existing
      * file will be overwritten; if aPrefix.$PID.$IDENTIFIER.log exists, we'll
      * try a file named something like aPrefix.$PID.$IDENTIFIER-1.log, and so
      * on.
      */
     already_AddRefed<nsIFile>
     CreateTempFile(const char* aPrefix)
     {
         nsPrintfCString filename("%s.%d%s%s.log",
             aPrefix,
             base::GetCurrentProcId(),
             mFilenameIdentifier.IsEmpty() ? "" : ".",
             NS_ConvertUTF16toUTF8(mFilenameIdentifier).get());
         // Get the log directory either from $MOZ_CC_LOG_DIRECTORY or from
         // the fallback directories in OpenTempFile.  We don't use an nsCOMPtr
         // here because OpenTempFile uses an in/out param and getter_AddRefs
         // wouldn't work.
         nsIFile* logFile = nullptr;
         if (char* env = PR_GetEnv("MOZ_CC_LOG_DIRECTORY")) {
             NS_NewNativeLocalFile(nsCString(env), /* followLinks = */ true,
                                   &logFile);
         }
         // In Android case, this function will open a file named aFilename under
         // specific folder (/data/local/tmp/memory-reports). Otherwise, it will
         // open a file named aFilename under "NS_OS_TEMP_DIR".
         nsresult rv = nsDumpUtils::OpenTempFile(
                                      filename,
                                      &logFile,
                                      NS_LITERAL_CSTRING("memory-reports"));
         if (NS_FAILED(rv)) {
           NS_IF_RELEASE(logFile);
           return nullptr;
         }
         return dont_AddRef(logFile);
     }
     void ClearDescribers()
     {
       CCGraphDescriber* d;
       while((d = mDescribers.popFirst())) {
         delete d;
       }
     }
     FILE *mStream;
     nsCOMPtr<nsIFile> mOutFile;
     bool mWantAllTraces;
     bool mDisableLog;
     bool mWantAfterProcessing;
     nsString mFilenameIdentifier;
     nsString mGCLogPath;
     nsString mCCLogPath;
     nsCString mCurrentAddress;
     mozilla::LinkedList<CCGraphDescriber> mDescribers;
 };
 NS_IMPL_ISUPPORTS(nsCycleCollectorLogger, nsICycleCollectorListener)
 nsresult
 nsCycleCollectorLoggerConstructor(nsISupports* aOuter,
                                   const nsIID& aIID,
                                   void* *aInstancePtr)
 {
     if (NS_WARN_IF(aOuter))
         return NS_ERROR_NO_AGGREGATION;
     nsISupports *logger = new nsCycleCollectorLogger();
     return logger->QueryInterface(aIID, aInstancePtr);
 }
 ////////////////////////////////////////////////////////////////////////
 // Bacon & Rajan's |MarkRoots| routine.
 ////////////////////////////////////////////////////////////////////////
 class GCGraphBuilder : public nsCycleCollectionTraversalCallback,
                        public nsCycleCollectionNoteRootCallback
 {
 private:
     GCGraph &mGraph;
     CycleCollectorResults &mResults;
     NodePool::Builder mNodeBuilder;
     EdgePool::Builder mEdgeBuilder;
     PtrInfo *mCurrPi;
     nsCycleCollectionParticipant *mJSParticipant;
     nsCycleCollectionParticipant *mJSZoneParticipant;
     nsCString mNextEdgeName;
     nsICycleCollectorListener *mListener;
     bool mMergeZones;
     bool mRanOutOfMemory;
 public:
     GCGraphBuilder(GCGraph &aGraph,
                    CycleCollectorResults &aResults,
                    CycleCollectedJSRuntime *aJSRuntime,
                    nsICycleCollectorListener *aListener,
                    bool aMergeZones);
     virtual ~GCGraphBuilder();
     bool WantAllTraces() const
     {
         return nsCycleCollectionNoteRootCallback::WantAllTraces();
     }
     PtrInfo* AddNode(void *aPtr, nsCycleCollectionParticipant *aParticipant);
     PtrInfo* AddWeakMapNode(void* node);
     void Traverse(PtrInfo* aPtrInfo);
     void SetLastChild();
     bool RanOutOfMemory() const { return mRanOutOfMemory; }
 private:
     void DescribeNode(uint32_t refCount, const char *objName)
     {
         mCurrPi->mRefCount = refCount;
     }
 public:
     // nsCycleCollectionNoteRootCallback methods.
     NS_IMETHOD_(void) NoteXPCOMRoot(nsISupports *root);
     NS_IMETHOD_(void) NoteJSRoot(void *root);
     NS_IMETHOD_(void) NoteNativeRoot(void *root, nsCycleCollectionParticipant *participant);
     NS_IMETHOD_(void) NoteWeakMapping(void *map, void *key, void *kdelegate, void *val);
     // nsCycleCollectionTraversalCallback methods.
     NS_IMETHOD_(void) DescribeRefCountedNode(nsrefcnt refCount,
                                              const char *objName);
     NS_IMETHOD_(void) DescribeGCedNode(bool isMarked, const char *objName,
                                        uint64_t aCompartmentAddress);
     NS_IMETHOD_(void) NoteXPCOMChild(nsISupports *child);
     NS_IMETHOD_(void) NoteJSChild(void *child);
     NS_IMETHOD_(void) NoteNativeChild(void *child,
                                       nsCycleCollectionParticipant *participant);
     NS_IMETHOD_(void) NoteNextEdgeName(const char* name);
 private:
     NS_IMETHOD_(void) NoteRoot(void *root,
                                nsCycleCollectionParticipant *participant)
     {
         MOZ_ASSERT(root);
         MOZ_ASSERT(participant);
         if (!participant->CanSkipInCC(root) || MOZ_UNLIKELY(WantAllTraces())) {
             AddNode(root, participant);
         }
     }
     NS_IMETHOD_(void) NoteChild(void *child, nsCycleCollectionParticipant *cp,
                                 nsCString edgeName)
     {
         PtrInfo *childPi = AddNode(child, cp);
         if (!childPi)
             return;
         mEdgeBuilder.Add(childPi);
         if (mListener) {
             mListener->NoteEdge((uint64_t)child, edgeName.get());
         }
         ++childPi->mInternalRefs;
     }
     JS::Zone *MergeZone(void *gcthing) {
         if (!mMergeZones) {
             return nullptr;
         }
         JS::Zone *zone = JS::GetGCThingZone(gcthing);
         if (js::IsSystemZone(zone)) {
             return nullptr;
         }
         return zone;
     }
 };
 GCGraphBuilder::GCGraphBuilder(GCGraph &aGraph,
                                CycleCollectorResults &aResults,
                                CycleCollectedJSRuntime *aJSRuntime,
                                nsICycleCollectorListener *aListener,
                                bool aMergeZones)
     : mGraph(aGraph),
       mResults(aResults),
       mNodeBuilder(aGraph.mNodes),
       mEdgeBuilder(aGraph.mEdges),
       mJSParticipant(nullptr),
       mJSZoneParticipant(nullptr),
       mListener(aListener),
       mMergeZones(aMergeZones),
       mRanOutOfMemory(false)
 {
     if (aJSRuntime) {
         mJSParticipant = aJSRuntime->GCThingParticipant();
         mJSZoneParticipant = aJSRuntime->ZoneParticipant();
     }
     uint32_t flags = 0;
     if (!flags && mListener) {
         flags = nsCycleCollectionTraversalCallback::WANT_DEBUG_INFO;
         bool all = false;
         mListener->GetWantAllTraces(&all);
         if (all) {
             flags |= nsCycleCollectionTraversalCallback::WANT_ALL_TRACES;
             mWantAllTraces = true; // for nsCycleCollectionNoteRootCallback
         }
     }
     mFlags |= flags;
     mMergeZones = mMergeZones && MOZ_LIKELY(!WantAllTraces());
     MOZ_ASSERT(nsCycleCollectionNoteRootCallback::WantAllTraces() ==
                nsCycleCollectionTraversalCallback::WantAllTraces());
 }
 GCGraphBuilder::~GCGraphBuilder()
 {
 }
 PtrInfo*
 GCGraphBuilder::AddNode(void *aPtr, nsCycleCollectionParticipant *aParticipant)
 {
     PtrToNodeEntry *e = mGraph.AddNodeToMap(aPtr);
     if (!e) {
         mRanOutOfMemory = true;
         return nullptr;
     }
     PtrInfo *result;
     if (!e->mNode) {
         // New entry.
         result = mNodeBuilder.Add(aPtr, aParticipant);
         e->mNode = result;
         NS_ASSERTION(result, "mNodeBuilder.Add returned null");
     } else {
         result = e->mNode;
         MOZ_ASSERT(result->mParticipant == aParticipant,
                    "nsCycleCollectionParticipant shouldn't change!");
     }
     return result;
 }
 MOZ_NEVER_INLINE void
 GCGraphBuilder::Traverse(PtrInfo* aPtrInfo)
 {
     mCurrPi = aPtrInfo;
     mCurrPi->SetFirstChild(mEdgeBuilder.Mark());
     if (!aPtrInfo->mParticipant) {
         return;
     }
     nsresult rv = aPtrInfo->mParticipant->Traverse(aPtrInfo->mPointer, *this);
     if (NS_FAILED(rv)) {
         Fault("script pointer traversal failed", aPtrInfo);
     }
 }
 void
 GCGraphBuilder::SetLastChild()
 {
     mCurrPi->SetLastChild(mEdgeBuilder.Mark());
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteXPCOMRoot(nsISupports *root)
 {
     root = CanonicalizeXPCOMParticipant(root);
     NS_ASSERTION(root,
                  "Don't add objects that don't participate in collection!");
     nsXPCOMCycleCollectionParticipant *cp;
     ToParticipant(root, &cp);
     NoteRoot(root, cp);
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteJSRoot(void *root)
 {
     if (JS::Zone *zone = MergeZone(root)) {
         NoteRoot(zone, mJSZoneParticipant);
     } else {
         NoteRoot(root, mJSParticipant);
     }
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteNativeRoot(void *root, nsCycleCollectionParticipant *participant)
 {
     NoteRoot(root, participant);
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::DescribeRefCountedNode(nsrefcnt refCount, const char *objName)
 {
     if (refCount == 0)
         Fault("zero refcount", mCurrPi);
     if (refCount == UINT32_MAX)
         Fault("overflowing refcount", mCurrPi);
     mResults.mVisitedRefCounted++;
     if (mListener) {
         mListener->NoteRefCountedObject((uint64_t)mCurrPi->mPointer, refCount,
                                         objName);
     }
     DescribeNode(refCount, objName);
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::DescribeGCedNode(bool isMarked, const char *objName,
                                  uint64_t aCompartmentAddress)
 {
     uint32_t refCount = isMarked ? UINT32_MAX : 0;
     mResults.mVisitedGCed++;
     if (mListener) {
         mListener->NoteGCedObject((uint64_t)mCurrPi->mPointer, isMarked,
                                   objName, aCompartmentAddress);
     }
     DescribeNode(refCount, objName);
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteXPCOMChild(nsISupports *child)
 {
     nsCString edgeName;
     if (WantDebugInfo()) {
         edgeName.Assign(mNextEdgeName);
         mNextEdgeName.Truncate();
     }
     if (!child || !(child = CanonicalizeXPCOMParticipant(child)))
         return;
     nsXPCOMCycleCollectionParticipant *cp;
     ToParticipant(child, &cp);
     if (cp && (!cp->CanSkipThis(child) || WantAllTraces())) {
         NoteChild(child, cp, edgeName);
     }
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteNativeChild(void *child,
                                 nsCycleCollectionParticipant *participant)
 {
     nsCString edgeName;
     if (WantDebugInfo()) {
         edgeName.Assign(mNextEdgeName);
         mNextEdgeName.Truncate();
     }
     if (!child)
         return;
     MOZ_ASSERT(participant, "Need a nsCycleCollectionParticipant!");
     NoteChild(child, participant, edgeName);
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteJSChild(void *child)
 {
     if (!child) {
         return;
     }
     nsCString edgeName;
     if (MOZ_UNLIKELY(WantDebugInfo())) {
         edgeName.Assign(mNextEdgeName);
         mNextEdgeName.Truncate();
     }
     if (xpc_GCThingIsGrayCCThing(child) || MOZ_UNLIKELY(WantAllTraces())) {
         if (JS::Zone *zone = MergeZone(child)) {
             NoteChild(zone, mJSZoneParticipant, edgeName);
         } else {
             NoteChild(child, mJSParticipant, edgeName);
         }
     }
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteNextEdgeName(const char* name)
 {
     if (WantDebugInfo()) {
         mNextEdgeName = name;
     }
 }
 PtrInfo*
 GCGraphBuilder::AddWeakMapNode(void *node)
 {
     MOZ_ASSERT(node, "Weak map node should be non-null.");
     if (!xpc_GCThingIsGrayCCThing(node) && !WantAllTraces())
         return nullptr;
     if (JS::Zone *zone = MergeZone(node)) {
         return AddNode(zone, mJSZoneParticipant);
     } else {
         return AddNode(node, mJSParticipant);
     }
 }
 NS_IMETHODIMP_(void)
 GCGraphBuilder::NoteWeakMapping(void *map, void *key, void *kdelegate, void *val)
 {
     // Don't try to optimize away the entry here, as we've already attempted to
     // do that in TraceWeakMapping in nsXPConnect.
     WeakMapping *mapping = mGraph.mWeakMaps.AppendElement();
     mapping->mMap = map ? AddWeakMapNode(map) : nullptr;
     mapping->mKey = key ? AddWeakMapNode(key) : nullptr;
     mapping->mKeyDelegate = kdelegate ? AddWeakMapNode(kdelegate) : mapping->mKey;
     mapping->mVal = val ? AddWeakMapNode(val) : nullptr;
     if (mListener) {
         mListener->NoteWeakMapEntry((uint64_t)map, (uint64_t)key,
                                     (uint64_t)kdelegate, (uint64_t)val);
     }
 }
 static bool
 AddPurpleRoot(GCGraphBuilder &aBuilder, void *aRoot, nsCycleCollectionParticipant *aParti)
 {
     CanonicalizeParticipant(&aRoot, &aParti);
     if (aBuilder.WantAllTraces() || !aParti->CanSkipInCC(aRoot)) {
         PtrInfo *pinfo = aBuilder.AddNode(aRoot, aParti);
         if (!pinfo) {
             return false;
         }
     }
     return true;
 }
 // MayHaveChild() will be false after a Traverse if the object does
 // not have any children the CC will visit.
 class ChildFinder : public nsCycleCollectionTraversalCallback
 {
 public:
     ChildFinder() : mMayHaveChild(false) {}
     // The logic of the Note*Child functions must mirror that of their
     // respective functions in GCGraphBuilder.
     NS_IMETHOD_(void) NoteXPCOMChild(nsISupports *child);
     NS_IMETHOD_(void) NoteNativeChild(void *child,
                                       nsCycleCollectionParticipant *helper);
     NS_IMETHOD_(void) NoteJSChild(void *child);
     NS_IMETHOD_(void) DescribeRefCountedNode(nsrefcnt refcount,
                                              const char *objname) {}
     NS_IMETHOD_(void) DescribeGCedNode(bool ismarked,
                                        const char *objname,
                                        uint64_t aCompartmentAddress) {}
     NS_IMETHOD_(void) NoteNextEdgeName(const char* name) {}
     bool MayHaveChild() {
         return mMayHaveChild;
     }
 private:
     bool mMayHaveChild;
 };
 NS_IMETHODIMP_(void)
 ChildFinder::NoteXPCOMChild(nsISupports *child)
 {
     if (!child || !(child = CanonicalizeXPCOMParticipant(child)))
         return;
     nsXPCOMCycleCollectionParticipant *cp;
     ToParticipant(child, &cp);
     if (cp && !cp->CanSkip(child, true))
         mMayHaveChild = true;
 }
 NS_IMETHODIMP_(void)
 ChildFinder::NoteNativeChild(void *child,
                              nsCycleCollectionParticipant *helper)
 {
     if (child)
         mMayHaveChild = true;
 }
 NS_IMETHODIMP_(void)
 ChildFinder::NoteJSChild(void *child)
 {
     if (child && xpc_GCThingIsGrayCCThing(child)) {
         mMayHaveChild = true;
     }
 }
 static bool
 MayHaveChild(void *o, nsCycleCollectionParticipant* cp)
 {
     ChildFinder cf;
     cp->Traverse(o, cf);
     return cf.MayHaveChild();
 }
 template<class T>
 class SegmentedArrayElement : public LinkedListElement<SegmentedArrayElement<T>>
                             , public AutoFallibleTArray<T, 60>
 {
 };
 template<class T>
 class SegmentedArray
 {
 public:
     ~SegmentedArray()
     {
         MOZ_ASSERT(IsEmpty());
     }
     void AppendElement(T& aElement)
     {
         SegmentedArrayElement<T>* last = mSegments.getLast();
         if (!last || last->Length() == last->Capacity()) {
             last = new SegmentedArrayElement<T>();
             mSegments.insertBack(last);
         }
         last->AppendElement(aElement);
     }
     void Clear()
     {
         SegmentedArrayElement<T>* first;
         while ((first = mSegments.popFirst())) {
             delete first;
         }
     }
     SegmentedArrayElement<T>* GetFirstSegment()
     {
         return mSegments.getFirst();
     }
     bool IsEmpty()
     {
         return !GetFirstSegment();
     }
 private:
     mozilla::LinkedList<SegmentedArrayElement<T>> mSegments;
 };
 // JSPurpleBuffer keeps references to GCThings which might affect the
 // next cycle collection. It is owned only by itself and during unlink its
 // self reference is broken down and the object ends up killing itself.
 // If GC happens before CC, references to GCthings and the self reference are
 // removed.
 class JSPurpleBuffer
 {
 public:
     JSPurpleBuffer(JSPurpleBuffer*& aReferenceToThis)
       : mReferenceToThis(aReferenceToThis)
     {
         mReferenceToThis = this;
         NS_ADDREF_THIS();
         mozilla::HoldJSObjects(this);
     }
     ~JSPurpleBuffer()
     {
         MOZ_ASSERT(mValues.IsEmpty());
         MOZ_ASSERT(mObjects.IsEmpty());
         MOZ_ASSERT(mTenuredObjects.IsEmpty());
     }
     void Destroy()
     {
         mReferenceToThis = nullptr;
         mValues.Clear();
         mObjects.Clear();
         mTenuredObjects.Clear();
         mozilla::DropJSObjects(this);
         NS_RELEASE_THIS();
     }
     NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(JSPurpleBuffer)
     NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(JSPurpleBuffer)
     JSPurpleBuffer*& mReferenceToThis;
     SegmentedArray<JS::Heap<JS::Value>> mValues;
     SegmentedArray<JS::Heap<JSObject*>> mObjects;
     SegmentedArray<JS::TenuredHeap<JSObject*>> mTenuredObjects;
 };
 NS_IMPL_CYCLE_COLLECTION_CLASS(JSPurpleBuffer)
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(JSPurpleBuffer)
     tmp->Destroy();
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(JSPurpleBuffer)
     CycleCollectionNoteChild(cb, tmp, "self");
     NS_IMPL_CYCLE_COLLECTION_TRAVERSE_SCRIPT_OBJECTS
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 #define NS_TRACE_SEGMENTED_ARRAY(_field)                                       \
     {                                                                          \
         auto segment = tmp->_field.GetFirstSegment();                          \
         while (segment) {                                                      \
             for (uint32_t i = segment->Length(); i > 0;) {                     \
                 aCallbacks.Trace(&segment->ElementAt(--i), #_field, aClosure); \
             }                                                                  \
             segment = segment->getNext();                                      \
         }                                                                      \
     }
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(JSPurpleBuffer)
     NS_TRACE_SEGMENTED_ARRAY(mValues)
     NS_TRACE_SEGMENTED_ARRAY(mObjects)
     NS_TRACE_SEGMENTED_ARRAY(mTenuredObjects)
 NS_IMPL_CYCLE_COLLECTION_TRACE_END
 NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(JSPurpleBuffer, AddRef)
 NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(JSPurpleBuffer, Release)
 struct SnowWhiteObject
 {
   void* mPointer;
   nsCycleCollectionParticipant* mParticipant;
   nsCycleCollectingAutoRefCnt* mRefCnt;
 };
 class SnowWhiteKiller : public TraceCallbacks
 {
 public:
     SnowWhiteKiller(nsCycleCollector *aCollector, uint32_t aMaxCount)
         : mCollector(aCollector)
     {
         MOZ_ASSERT(mCollector, "Calling SnowWhiteKiller after nsCC went away");
         while (true) {
             if (mObjects.SetCapacity(aMaxCount)) {
                 break;
             }
             if (aMaxCount == 1) {
                 NS_RUNTIMEABORT("Not enough memory to even delete objects!");
             }
             aMaxCount /= 2;
         }
     }
     ~SnowWhiteKiller()
     {
         for (uint32_t i = 0; i < mObjects.Length(); ++i) {
             SnowWhiteObject& o = mObjects[i];
             if (!o.mRefCnt->get() && !o.mRefCnt->IsInPurpleBuffer()) {
                 mCollector->RemoveObjectFromGraph(o.mPointer);
                 o.mRefCnt->stabilizeForDeletion();
                 o.mParticipant->Trace(o.mPointer, *this, nullptr);
                 o.mParticipant->DeleteCycleCollectable(o.mPointer);
             }
         }
     }
     void
     Visit(nsPurpleBuffer& aBuffer, nsPurpleBufferEntry* aEntry)
     {
         MOZ_ASSERT(aEntry->mObject, "Null object in purple buffer");
         if (!aEntry->mRefCnt->get()) {
             void *o = aEntry->mObject;
             nsCycleCollectionParticipant *cp = aEntry->mParticipant;
             CanonicalizeParticipant(&o, &cp);
             SnowWhiteObject swo = { o, cp, aEntry->mRefCnt };
             if (mObjects.AppendElement(swo)) {
                 aBuffer.Remove(aEntry);
             }
         }
     }
     bool HasSnowWhiteObjects() const
     {
       return mObjects.Length() > 0;
     }
     virtual void Trace(JS::Heap<JS::Value>* aValue, const char* aName,
                        void* aClosure) const
     {
         if (aValue->isMarkable()) {
             void* thing = aValue->toGCThing();
             if (thing && xpc_GCThingIsGrayCCThing(thing)) {
                 mCollector->GetJSPurpleBuffer()->mValues.AppendElement(*aValue);
             }
         }
     }
     virtual void Trace(JS::Heap<jsid>* aId, const char* aName,
                        void* aClosure) const
     {
     }
     virtual void Trace(JS::Heap<JSObject*>* aObject, const char* aName,
                        void* aClosure) const
     {
         if (*aObject && xpc_GCThingIsGrayCCThing(*aObject)) {
             mCollector->GetJSPurpleBuffer()->mObjects.AppendElement(*aObject);
         }
     }
     virtual void Trace(JS::TenuredHeap<JSObject*>* aObject, const char* aName,
                        void* aClosure) const
     {
         if (*aObject && xpc_GCThingIsGrayCCThing(*aObject)) {
             mCollector->GetJSPurpleBuffer()->mTenuredObjects.AppendElement(*aObject);
         }
     }
     virtual void Trace(JS::Heap<JSString*>* aString, const char* aName,
                        void* aClosure) const
     {
     }
     virtual void Trace(JS::Heap<JSScript*>* aScript, const char* aName,
                        void* aClosure) const
     {
     }
     virtual void Trace(JS::Heap<JSFunction*>* aFunction, const char* aName,
                        void* aClosure) const
     {
     }
 private:
     nsCycleCollector *mCollector;
     FallibleTArray<SnowWhiteObject> mObjects;
 };
 class RemoveSkippableVisitor : public SnowWhiteKiller
 {
 public:
     RemoveSkippableVisitor(nsCycleCollector* aCollector,
                            uint32_t aMaxCount, bool aRemoveChildlessNodes,
                            bool aAsyncSnowWhiteFreeing,
                            CC_ForgetSkippableCallback aCb)
         : SnowWhiteKiller(aCollector, aAsyncSnowWhiteFreeing ? 0 : aMaxCount),
           mRemoveChildlessNodes(aRemoveChildlessNodes),
           mAsyncSnowWhiteFreeing(aAsyncSnowWhiteFreeing),
           mDispatchedDeferredDeletion(false),
           mCallback(aCb)
     {}
     ~RemoveSkippableVisitor()
     {
         // Note, we must call the callback before SnowWhiteKiller calls
         // DeleteCycleCollectable!
         if (mCallback) {
             mCallback();
         }
         if (HasSnowWhiteObjects()) {
             // Effectively a continuation.
             nsCycleCollector_dispatchDeferredDeletion(true);
         }
     }
     void
     Visit(nsPurpleBuffer &aBuffer, nsPurpleBufferEntry *aEntry)
     {
         MOZ_ASSERT(aEntry->mObject, "null mObject in purple buffer");
         if (!aEntry->mRefCnt->get()) {
             if (!mAsyncSnowWhiteFreeing) {
                 SnowWhiteKiller::Visit(aBuffer, aEntry);
             } else if (!mDispatchedDeferredDeletion) {
                 mDispatchedDeferredDeletion = true;
                 nsCycleCollector_dispatchDeferredDeletion(false);
             }
             return;
         }
         void *o = aEntry->mObject;
         nsCycleCollectionParticipant *cp = aEntry->mParticipant;
         CanonicalizeParticipant(&o, &cp);
         if (aEntry->mRefCnt->IsPurple() && !cp->CanSkip(o, false) &&
             (!mRemoveChildlessNodes || MayHaveChild(o, cp))) {
             return;
         }
         aBuffer.Remove(aEntry);
     }
 private:
     bool mRemoveChildlessNodes;
     bool mAsyncSnowWhiteFreeing;
     bool mDispatchedDeferredDeletion;
     CC_ForgetSkippableCallback mCallback;
 };
 void
 nsPurpleBuffer::RemoveSkippable(nsCycleCollector* aCollector,
                                 bool aRemoveChildlessNodes,
                                 bool aAsyncSnowWhiteFreeing,
                                 CC_ForgetSkippableCallback aCb)
 {
     RemoveSkippableVisitor visitor(aCollector, Count(), aRemoveChildlessNodes,
                                    aAsyncSnowWhiteFreeing, aCb);
     VisitEntries(visitor);
 }
 bool
 nsCycleCollector::FreeSnowWhite(bool aUntilNoSWInPurpleBuffer)
 {
     CheckThreadSafety();
     if (mFreeingSnowWhite) {
         return false;
     }
     AutoRestore<bool> ar(mFreeingSnowWhite);
     mFreeingSnowWhite = true;
     bool hadSnowWhiteObjects = false;
     do {
         SnowWhiteKiller visitor(this, mPurpleBuf.Count());
         mPurpleBuf.VisitEntries(visitor);
         hadSnowWhiteObjects = hadSnowWhiteObjects ||
                               visitor.HasSnowWhiteObjects();
         if (!visitor.HasSnowWhiteObjects()) {
             break;
         }
     } while (aUntilNoSWInPurpleBuffer);
     return hadSnowWhiteObjects;
 }
 void
 nsCycleCollector::ForgetSkippable(bool aRemoveChildlessNodes,
                                   bool aAsyncSnowWhiteFreeing)
 {
     CheckThreadSafety();
     // If we remove things from the purple buffer during graph building, we may
     // lose track of an object that was mutated during graph building.
     MOZ_ASSERT(mIncrementalPhase == IdlePhase);
     if (mJSRuntime) {
         mJSRuntime->PrepareForForgetSkippable();
     }
     MOZ_ASSERT(!mScanInProgress, "Don't forget skippable or free snow-white while scan is in progress.");
     mPurpleBuf.RemoveSkippable(this, aRemoveChildlessNodes,
                                aAsyncSnowWhiteFreeing, mForgetSkippableCB);
 }
 MOZ_NEVER_INLINE void
 nsCycleCollector::MarkRoots(SliceBudget &aBudget)
 {
     const intptr_t kNumNodesBetweenTimeChecks = 1000;
     const intptr_t kStep = SliceBudget::CounterReset / kNumNodesBetweenTimeChecks;
     TimeLog timeLog;
     AutoRestore<bool> ar(mScanInProgress);
     MOZ_ASSERT(!mScanInProgress);
     mScanInProgress = true;
     MOZ_ASSERT(mIncrementalPhase == GraphBuildingPhase);
     MOZ_ASSERT(mCurrNode);
     while (!aBudget.isOverBudget() && !mCurrNode->IsDone()) {
         PtrInfo *pi = mCurrNode->GetNext();
         if (!pi) {
             MOZ_CRASH();
         }
         // We need to call the builder's Traverse() method on deleted nodes, to
         // set their firstChild() that may be read by a prior non-deleted
         // neighbor.
         mBuilder->Traverse(pi);
         if (mCurrNode->AtBlockEnd()) {
             mBuilder->SetLastChild();
         }
         aBudget.step(kStep);
     }
     if (!mCurrNode->IsDone()) {
         timeLog.Checkpoint("MarkRoots()");
         return;
     }
     if (mGraph.mRootCount > 0) {
         mBuilder->SetLastChild();
     }
     if (mBuilder->RanOutOfMemory()) {
         MOZ_ASSERT(false, "Ran out of memory while building cycle collector graph");
         CC_TELEMETRY(_OOM, true);
     }
     mBuilder = nullptr;
     mCurrNode = nullptr;
     mIncrementalPhase = ScanAndCollectWhitePhase;
     timeLog.Checkpoint("MarkRoots()");
 }
 ////////////////////////////////////////////////////////////////////////
 // Bacon & Rajan's |ScanRoots| routine.
 ////////////////////////////////////////////////////////////////////////
 struct ScanBlackVisitor
 {
     ScanBlackVisitor(uint32_t &aWhiteNodeCount, bool &aFailed)
         : mWhiteNodeCount(aWhiteNodeCount), mFailed(aFailed)
     {
     }
     bool ShouldVisitNode(PtrInfo const *pi)
     {
         return pi->mColor != black;
     }
     MOZ_NEVER_INLINE void VisitNode(PtrInfo *pi)
     {
         if (pi->mColor == white)
             --mWhiteNodeCount;
         pi->mColor = black;
     }
     void Failed()
     {
         mFailed = true;
     }
 private:
     uint32_t &mWhiteNodeCount;
     bool &mFailed;
 };
 struct scanVisitor
 {
     scanVisitor(uint32_t &aWhiteNodeCount, bool &aFailed, bool aWasIncremental)
         : mWhiteNodeCount(aWhiteNodeCount), mFailed(aFailed),
           mWasIncremental(aWasIncremental)
     {
     }
     bool ShouldVisitNode(PtrInfo const *pi)
     {
         return pi->mColor == grey;
     }
     MOZ_NEVER_INLINE void VisitNode(PtrInfo *pi)
     {
         if (pi->mInternalRefs > pi->mRefCount && pi->mRefCount > 0) {
             // If we found more references to an object than its ref count, then
             // the object should have already been marked as an incremental
             // root. Note that this is imprecise, because pi could have been
             // marked black for other reasons. Always fault if we weren't
             // incremental, as there were no incremental roots in that case.
             if (!mWasIncremental || pi->mColor != black) {
                 Fault("traversed refs exceed refcount", pi);
             }
         }
         if (pi->mInternalRefs == pi->mRefCount || pi->mRefCount == 0) {
             pi->mColor = white;
             ++mWhiteNodeCount;
         } else {
             GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount, mFailed)).Walk(pi);
             MOZ_ASSERT(pi->mColor == black,
                        "Why didn't ScanBlackVisitor make pi black?");
         }
     }
     void Failed() {
         mFailed = true;
     }
 private:
     uint32_t &mWhiteNodeCount;
     bool &mFailed;
     bool mWasIncremental;
 };
 // Iterate over the WeakMaps.  If we mark anything while iterating
 // over the WeakMaps, we must iterate over all of the WeakMaps again.
 void
 nsCycleCollector::ScanWeakMaps()
 {
     bool anyChanged;
     bool failed = false;
     do {
         anyChanged = false;
         for (uint32_t i = 0; i < mGraph.mWeakMaps.Length(); i++) {
             WeakMapping *wm = &mGraph.mWeakMaps[i];
             // If any of these are null, the original object was marked black.
             uint32_t mColor = wm->mMap ? wm->mMap->mColor : black;
             uint32_t kColor = wm->mKey ? wm->mKey->mColor : black;
             uint32_t kdColor = wm->mKeyDelegate ? wm->mKeyDelegate->mColor : black;
             uint32_t vColor = wm->mVal ? wm->mVal->mColor : black;
             // All non-null weak mapping maps, keys and values are
             // roots (in the sense of WalkFromRoots) in the cycle
             // collector graph, and thus should have been colored
             // either black or white in ScanRoots().
             MOZ_ASSERT(mColor != grey, "Uncolored weak map");
             MOZ_ASSERT(kColor != grey, "Uncolored weak map key");
             MOZ_ASSERT(kdColor != grey, "Uncolored weak map key delegate");
             MOZ_ASSERT(vColor != grey, "Uncolored weak map value");
             if (mColor == black && kColor != black && kdColor == black) {
                 GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount, failed)).Walk(wm->mKey);
                 anyChanged = true;
             }
             if (mColor == black && kColor == black && vColor != black) {
                 GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount, failed)).Walk(wm->mVal);
                 anyChanged = true;
             }
         }
     } while (anyChanged);
     if (failed) {
         MOZ_ASSERT(false, "Ran out of memory in ScanWeakMaps");
         CC_TELEMETRY(_OOM, true);
     }
 }
 // Flood black from any objects in the purple buffer that are in the CC graph.
 class PurpleScanBlackVisitor
 {
 public:
     PurpleScanBlackVisitor(GCGraph &aGraph, nsICycleCollectorListener *aListener,
                            uint32_t &aCount, bool &aFailed)
         : mGraph(aGraph), mListener(aListener), mCount(aCount), mFailed(aFailed)
     {
     }
     void
     Visit(nsPurpleBuffer &aBuffer, nsPurpleBufferEntry *aEntry)
     {
         MOZ_ASSERT(aEntry->mObject, "Entries with null mObject shouldn't be in the purple buffer.");
         MOZ_ASSERT(aEntry->mRefCnt->get() != 0, "Snow-white objects shouldn't be in the purple buffer.");
         void *obj = aEntry->mObject;
         if (!aEntry->mParticipant) {
             obj = CanonicalizeXPCOMParticipant(static_cast<nsISupports*>(obj));
             MOZ_ASSERT(obj, "Don't add objects that don't participate in collection!");
         }
         PtrInfo *pi = mGraph.FindNode(obj);
         if (!pi) {
             return;
         }
         MOZ_ASSERT(pi->mParticipant, "No dead objects should be in the purple buffer.");
         if (MOZ_UNLIKELY(mListener)) {
             mListener->NoteIncrementalRoot((uint64_t)pi->mPointer);
         }
         if (pi->mColor == black) {
             return;
         }
         GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mCount, mFailed)).Walk(pi);
     }
 private:
     GCGraph &mGraph;
     nsICycleCollectorListener *mListener;
     uint32_t &mCount;
     bool &mFailed;
 };
 // Objects that have been stored somewhere since the start of incremental graph building must
 // be treated as live for this cycle collection, because we may not have accurate information
 // about who holds references to them.
 void
 nsCycleCollector::ScanIncrementalRoots()
 {
     TimeLog timeLog;
     // Reference counted objects:
     // We cleared the purple buffer at the start of the current ICC, so if a
     // refcounted object is purple, it may have been AddRef'd during the current
     // ICC. (It may also have only been released.) If that is the case, we cannot
     // be sure that the set of things pointing to the object in the CC graph
     // is accurate. Therefore, for safety, we treat any purple objects as being
     // live during the current CC. We don't remove anything from the purple
     // buffer here, so these objects will be suspected and freed in the next CC
     // if they are garbage.
     bool failed = false;
     PurpleScanBlackVisitor purpleScanBlackVisitor(mGraph, mListener, mWhiteNodeCount, failed);
     mPurpleBuf.VisitEntries(purpleScanBlackVisitor);
     timeLog.Checkpoint("ScanIncrementalRoots::fix purple");
     // Garbage collected objects:
     // If a GCed object was added to the graph with a refcount of zero, and is
     // now marked black by the GC, it was probably gray before and was exposed
     // to active JS, so it may have been stored somewhere, so it needs to be
     // treated as live.
     if (mJSRuntime) {
         nsCycleCollectionParticipant *jsParticipant = mJSRuntime->GCThingParticipant();
         nsCycleCollectionParticipant *zoneParticipant = mJSRuntime->ZoneParticipant();
         NodePool::Enumerator etor(mGraph.mNodes);
         while (!etor.IsDone()) {
             PtrInfo *pi = etor.GetNext();
             // If the refcount is non-zero, pi can't have been a gray JS object.
             if (pi->mRefCount != 0) {
                 continue;
             }
             // As an optimization, if an object has already been determined to be live,
             // don't consider it further.  We can't do this if there is a listener,
             // because the listener wants to know the complete set of incremental roots.
             if (pi->mColor == black && MOZ_LIKELY(!mListener)) {
                 continue;
             }
             // If the object is still marked gray by the GC, nothing could have gotten
             // hold of it, so it isn't an incremental root.
             if (pi->mParticipant == jsParticipant) {
                 if (xpc_GCThingIsGrayCCThing(pi->mPointer)) {
                     continue;
                 }
             } else if (pi->mParticipant == zoneParticipant) {
                 JS::Zone *zone = static_cast<JS::Zone*>(pi->mPointer);
                 if (js::ZoneGlobalsAreAllGray(zone)) {
                     continue;
                 }
             } else {
                 MOZ_ASSERT(false, "Non-JS thing with 0 refcount? Treating as live.");
             }
             // At this point, pi must be an incremental root.
             // If there's a listener, tell it about this root. We don't bother with the
             // optimization of skipping the Walk() if pi is black: it will just return
             // without doing anything and there's no need to make this case faster.
             if (MOZ_UNLIKELY(mListener)) {
                 mListener->NoteIncrementalRoot((uint64_t)pi->mPointer);
             }
             GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount, failed)).Walk(pi);
         }
         timeLog.Checkpoint("ScanIncrementalRoots::fix JS");
     }
     if (failed) {
         NS_ASSERTION(false, "Ran out of memory in ScanIncrementalRoots");
         CC_TELEMETRY(_OOM, true);
     }
 }
 void
 nsCycleCollector::ScanRoots(bool aFullySynchGraphBuild)
 {
     AutoRestore<bool> ar(mScanInProgress);
     MOZ_ASSERT(!mScanInProgress);
     mScanInProgress = true;
     mWhiteNodeCount = 0;
     MOZ_ASSERT(mIncrementalPhase == ScanAndCollectWhitePhase);
     if (!aFullySynchGraphBuild) {
         ScanIncrementalRoots();
     }
     TimeLog timeLog;
     // On the assumption that most nodes will be black, it's
     // probably faster to use a GraphWalker than a
     // NodePool::Enumerator.
     bool failed = false;
     scanVisitor sv(mWhiteNodeCount, failed, !aFullySynchGraphBuild);
     GraphWalker<scanVisitor>(sv).WalkFromRoots(mGraph);
     timeLog.Checkpoint("ScanRoots::WalkFromRoots");
     if (failed) {
         NS_ASSERTION(false, "Ran out of memory in ScanRoots");
         CC_TELEMETRY(_OOM, true);
     }
     // Scanning weak maps must be done last.
     ScanWeakMaps();
     timeLog.Checkpoint("ScanRoots::ScanWeakMaps");
     if (mListener) {
         mListener->BeginResults();
         NodePool::Enumerator etor(mGraph.mNodes);
         while (!etor.IsDone()) {
             PtrInfo *pi = etor.GetNext();
             if (!pi->mParticipant) {
                 continue;
             }
             switch (pi->mColor) {
             case black:
                 if (pi->mRefCount > 0 && pi->mRefCount < UINT32_MAX &&
                     pi->mInternalRefs != pi->mRefCount) {
                     mListener->DescribeRoot((uint64_t)pi->mPointer,
                                             pi->mInternalRefs);
                 }
                 break;
             case white:
                 mListener->DescribeGarbage((uint64_t)pi->mPointer);
                 break;
             case grey:
                 // With incremental CC, we can end up with a grey object after
                 // scanning if it is only reachable from an object that gets freed.
                 break;
             }
         }
         mListener->End();
         mListener = nullptr;
         timeLog.Checkpoint("ScanRoots::listener");
     }
 }
 ////////////////////////////////////////////////////////////////////////
 // Bacon & Rajan's |CollectWhite| routine, somewhat modified.
 ////////////////////////////////////////////////////////////////////////
 bool
 nsCycleCollector::CollectWhite()
 {
     // Explanation of "somewhat modified": we have no way to collect the
     // set of whites "all at once", we have to ask each of them to drop
     // their outgoing links and assume this will cause the garbage cycle
     // to *mostly* self-destruct (except for the reference we continue
     // to hold).
     //
     // To do this "safely" we must make sure that the white nodes we're
     // operating on are stable for the duration of our operation. So we
     // make 3 sets of calls to language runtimes:
     //
     //   - Root(whites), which should pin the whites in memory.
     //   - Unlink(whites), which drops outgoing links on each white.
     //   - Unroot(whites), which returns the whites to normal GC.
     TimeLog timeLog;
     nsAutoTArray<PtrInfo*, 4000> whiteNodes;
     MOZ_ASSERT(mIncrementalPhase == ScanAndCollectWhitePhase);
     whiteNodes.SetCapacity(mWhiteNodeCount);
     uint32_t numWhiteGCed = 0;
     NodePool::Enumerator etor(mGraph.mNodes);
     while (!etor.IsDone())
     {
         PtrInfo *pinfo = etor.GetNext();
         if (pinfo->mColor == white && pinfo->mParticipant) {
             whiteNodes.AppendElement(pinfo);
             pinfo->mParticipant->Root(pinfo->mPointer);
             if (pinfo->mRefCount == 0) {
                 // only JS objects have a refcount of 0
                 ++numWhiteGCed;
             }
         }
     }
     uint32_t count = whiteNodes.Length();
     MOZ_ASSERT(numWhiteGCed <= count,
                "More freed GCed nodes than total freed nodes.");
     mResults.mFreedRefCounted += count - numWhiteGCed;
     mResults.mFreedGCed += numWhiteGCed;
     timeLog.Checkpoint("CollectWhite::Root");
     if (mBeforeUnlinkCB) {
         mBeforeUnlinkCB();
         timeLog.Checkpoint("CollectWhite::BeforeUnlinkCB");
     }
     for (uint32_t i = 0; i < count; ++i) {
         PtrInfo *pinfo = whiteNodes.ElementAt(i);
         MOZ_ASSERT(pinfo->mParticipant, "Unlink shouldn't see objects removed from graph.");
         pinfo->mParticipant->Unlink(pinfo->mPointer);
 #ifdef DEBUG
         if (mJSRuntime) {
             mJSRuntime->AssertNoObjectsToTrace(pinfo->mPointer);
         }
 #endif
     }
     timeLog.Checkpoint("CollectWhite::Unlink");
     for (uint32_t i = 0; i < count; ++i) {
         PtrInfo *pinfo = whiteNodes.ElementAt(i);
         MOZ_ASSERT(pinfo->mParticipant, "Unroot shouldn't see objects removed from graph.");
         pinfo->mParticipant->Unroot(pinfo->mPointer);
     }
     timeLog.Checkpoint("CollectWhite::Unroot");
     nsCycleCollector_dispatchDeferredDeletion(false);
     mIncrementalPhase = CleanupPhase;
     return count > 0;
 }
 ////////////////////////
 // Memory reporting
 ////////////////////////
 MOZ_DEFINE_MALLOC_SIZE_OF(CycleCollectorMallocSizeOf)
 NS_IMETHODIMP
 nsCycleCollector::CollectReports(nsIHandleReportCallback* aHandleReport,
                                  nsISupports* aData)
 {
     size_t objectSize, graphNodesSize, graphEdgesSize, weakMapsSize,
            purpleBufferSize;
     SizeOfIncludingThis(CycleCollectorMallocSizeOf,
                         &objectSize,
                         &graphNodesSize, &graphEdgesSize,
                         &weakMapsSize,
                         &purpleBufferSize);
 #define REPORT(_path, _amount, _desc)                                     \
     do {                                                                  \
         size_t amount = _amount;  /* evaluate |_amount| only once */      \
         if (amount > 0) {                                                 \
             nsresult rv;                                                  \
             rv = aHandleReport->Callback(EmptyCString(),                  \
                                          NS_LITERAL_CSTRING(_path),       \
                                          KIND_HEAP, UNITS_BYTES, _amount, \
                                          NS_LITERAL_CSTRING(_desc),       \
                                          aData);                          \
             if (NS_WARN_IF(NS_FAILED(rv)))                                \
                 return rv;                                                \
         }                                                                 \
     } while (0)
     REPORT("explicit/cycle-collector/collector-object", objectSize,
            "Memory used for the cycle collector object itself.");
     REPORT("explicit/cycle-collector/graph-nodes", graphNodesSize,
            "Memory used for the nodes of the cycle collector's graph. "
            "This should be zero when the collector is idle.");
     REPORT("explicit/cycle-collector/graph-edges", graphEdgesSize,
            "Memory used for the edges of the cycle collector's graph. "
            "This should be zero when the collector is idle.");
     REPORT("explicit/cycle-collector/weak-maps", weakMapsSize,
            "Memory used for the representation of weak maps in the "
            "cycle collector's graph. "
            "This should be zero when the collector is idle.");
     REPORT("explicit/cycle-collector/purple-buffer", purpleBufferSize,
            "Memory used for the cycle collector's purple buffer.");
 #undef REPORT
     return NS_OK;
 };
 ////////////////////////////////////////////////////////////////////////
 // Collector implementation
 ////////////////////////////////////////////////////////////////////////
 nsCycleCollector::nsCycleCollector() :
     mActivelyCollecting(false),
     mFreeingSnowWhite(false),
     mScanInProgress(false),
     mJSRuntime(nullptr),
     mIncrementalPhase(IdlePhase),
     mThread(NS_GetCurrentThread()),
     mWhiteNodeCount(0),
     mBeforeUnlinkCB(nullptr),
     mForgetSkippableCB(nullptr),
     mUnmergedNeeded(0),
     mMergedInARow(0),
     mJSPurpleBuffer(nullptr)
 {
 }
 nsCycleCollector::~nsCycleCollector()
 {
     UnregisterWeakMemoryReporter(this);
 }
 void
 nsCycleCollector::RegisterJSRuntime(CycleCollectedJSRuntime *aJSRuntime)
 {
     if (mJSRuntime)
         Fault("multiple registrations of cycle collector JS runtime", aJSRuntime);
     mJSRuntime = aJSRuntime;
     // We can't register as a reporter in nsCycleCollector() because that runs
     // before the memory reporter manager is initialized.  So we do it here
     // instead.
     static bool registered = false;
     if (!registered) {
         RegisterWeakMemoryReporter(this);
         registered = true;
     }
 }
 void
 nsCycleCollector::ForgetJSRuntime()
 {
     if (!mJSRuntime)
         Fault("forgetting non-registered cycle collector JS runtime");
     mJSRuntime = nullptr;
 }
 #ifdef DEBUG
 static bool
 HasParticipant(void *aPtr, nsCycleCollectionParticipant *aParti)
 {
     if (aParti) {
         return true;
     }
     nsXPCOMCycleCollectionParticipant *xcp;
     ToParticipant(static_cast<nsISupports*>(aPtr), &xcp);
     return xcp != nullptr;
 }
 #endif
 MOZ_ALWAYS_INLINE void
 nsCycleCollector::Suspect(void *aPtr, nsCycleCollectionParticipant *aParti,
                           nsCycleCollectingAutoRefCnt *aRefCnt)
 {
     CheckThreadSafety();
     // Re-entering ::Suspect during collection used to be a fault, but
     // we are canonicalizing nsISupports pointers using QI, so we will
     // see some spurious refcount traffic here.
     if (MOZ_UNLIKELY(mScanInProgress)) {
         return;
     }
     MOZ_ASSERT(aPtr, "Don't suspect null pointers");
     MOZ_ASSERT(HasParticipant(aPtr, aParti),
                "Suspected nsISupports pointer must QI to nsXPCOMCycleCollectionParticipant");
     mPurpleBuf.Put(aPtr, aParti, aRefCnt);
 }
 void
 nsCycleCollector::CheckThreadSafety()
 {
 #ifdef DEBUG
     nsIThread* currentThread = NS_GetCurrentThread();
     // XXXkhuey we can be called so late in shutdown that NS_GetCurrentThread
     // returns null (after the thread manager has shut down)
     MOZ_ASSERT(mThread == currentThread || !currentThread);
 #endif
 }
 // The cycle collector uses the mark bitmap to discover what JS objects
 // were reachable only from XPConnect roots that might participate in
 // cycles. We ask the JS runtime whether we need to force a GC before
 // this CC. It returns true on startup (before the mark bits have been set),
 // and also when UnmarkGray has run out of stack.  We also force GCs on shut
 // down to collect cycles involving both DOM and JS.
 void
 nsCycleCollector::FixGrayBits(bool aForceGC)
 {
     CheckThreadSafety();
     if (!mJSRuntime)
         return;
     if (!aForceGC) {
         mJSRuntime->FixWeakMappingGrayBits();
         bool needGC = mJSRuntime->NeedCollect();
         // Only do a telemetry ping for non-shutdown CCs.
         CC_TELEMETRY(_NEED_GC, needGC);
         if (!needGC)
             return;
         mResults.mForcedGC = true;
     }
     TimeLog timeLog;
     mJSRuntime->Collect(aForceGC ? JS::gcreason::SHUTDOWN_CC : JS::gcreason::CC_FORCED);
     timeLog.Checkpoint("GC()");
 }
 void
 nsCycleCollector::CleanupAfterCollection()
 {
     MOZ_ASSERT(mIncrementalPhase == CleanupPhase);
     mGraph.Clear();
     uint32_t interval = (uint32_t) ((TimeStamp::Now() - mCollectionStart).ToMilliseconds());
 #ifdef COLLECT_TIME_DEBUG
     printf("cc: total cycle collector time was %ums\n", interval);
     printf("cc: visited %u ref counted and %u GCed objects, freed %d ref counted and %d GCed objects",
            mResults.mVisitedRefCounted, mResults.mVisitedGCed,
            mResults.mFreedRefCounted, mResults.mFreedGCed);
     uint32_t numVisited = mResults.mVisitedRefCounted + mResults.mVisitedGCed;
     if (numVisited > 1000) {
         uint32_t numFreed = mResults.mFreedRefCounted + mResults.mFreedGCed;
         printf(" (%d%%)", 100 * numFreed / numVisited);
     }
     printf(".\ncc: \n");
 #endif
     CC_TELEMETRY( , interval);
     CC_TELEMETRY(_VISITED_REF_COUNTED, mResults.mVisitedRefCounted);
     CC_TELEMETRY(_VISITED_GCED, mResults.mVisitedGCed);
     CC_TELEMETRY(_COLLECTED, mWhiteNodeCount);
     if (mJSRuntime) {
         mJSRuntime->EndCycleCollectionCallback(mResults);
     }
     mIncrementalPhase = IdlePhase;
 }
 void
 nsCycleCollector::ShutdownCollect()
 {
     SliceBudget unlimitedBudget;
     uint32_t i;
     for (i = 0; i < DEFAULT_SHUTDOWN_COLLECTIONS; ++i) {
         if (!Collect(ShutdownCC, unlimitedBudget, nullptr)) {
             break;
         }
     }
     NS_WARN_IF_FALSE(i < NORMAL_SHUTDOWN_COLLECTIONS, "Extra shutdown CC");
 }
 static void
 PrintPhase(const char *aPhase)
 {
 #ifdef DEBUG_PHASES
     printf("cc: begin %s on %s\n", aPhase,
            NS_IsMainThread() ? "mainthread" : "worker");
 #endif
 }
 bool
 nsCycleCollector::Collect(ccType aCCType,
                           SliceBudget &aBudget,
                           nsICycleCollectorListener *aManualListener)
 {
     CheckThreadSafety();
     // This can legitimately happen in a few cases. See bug 383651.
     if (mActivelyCollecting || mFreeingSnowWhite) {
         return false;
     }
     mActivelyCollecting = true;
     bool startedIdle = (mIncrementalPhase == IdlePhase);
     bool collectedAny = false;
     // If the CC started idle, it will call BeginCollection, which
     // will do FreeSnowWhite, so it doesn't need to be done here.
     if (!startedIdle) {
         FreeSnowWhite(true);
     }
     bool finished = false;
     do {
         switch (mIncrementalPhase) {
         case IdlePhase:
             PrintPhase("BeginCollection");
             BeginCollection(aCCType, aManualListener);
             break;
         case GraphBuildingPhase:
             PrintPhase("MarkRoots");
             MarkRoots(aBudget);
             break;
         case ScanAndCollectWhitePhase:
             // We do ScanRoots and CollectWhite in a single slice to ensure
             // that we won't unlink a live object if a weak reference is
             // promoted to a strong reference after ScanRoots has finished.
             // See bug 926533.
             PrintPhase("ScanRoots");
             ScanRoots(startedIdle);
             PrintPhase("CollectWhite");
             collectedAny = CollectWhite();
             break;
         case CleanupPhase:
             PrintPhase("CleanupAfterCollection");
             CleanupAfterCollection();
             finished = true;
             break;
         }
     } while (!aBudget.checkOverBudget() && !finished);
     // Clear mActivelyCollecting here to ensure that a recursive call to
     // Collect() does something.
     mActivelyCollecting = false;
     if (aCCType != SliceCC && !startedIdle) {
         // We were in the middle of an incremental CC (using its own listener).
         // Somebody has forced a CC, so after having finished out the current CC,
         // run the CC again using the new listener.
         MOZ_ASSERT(mIncrementalPhase == IdlePhase);
         if (Collect(aCCType, aBudget, aManualListener)) {
             collectedAny = true;
         }
     }
     MOZ_ASSERT_IF(aCCType != SliceCC, mIncrementalPhase == IdlePhase);
     return collectedAny;
 }
 // Any JS objects we have in the graph could die when we GC, but we
 // don't want to abandon the current CC, because the graph contains
 // information about purple roots. So we synchronously finish off
 // the current CC.
 void
 nsCycleCollector::PrepareForGarbageCollection()
 {
     if (mIncrementalPhase == IdlePhase) {
         MOZ_ASSERT(mGraph.IsEmpty(), "Non-empty graph when idle");
         MOZ_ASSERT(!mBuilder, "Non-null builder when idle");
         if (mJSPurpleBuffer) {
             mJSPurpleBuffer->Destroy();
         }
         return;
     }
     SliceBudget unlimitedBudget;
     PrintPhase("PrepareForGarbageCollection");
     // Use SliceCC because we only want to finish the CC in progress.
     Collect(SliceCC, unlimitedBudget, nullptr);
     MOZ_ASSERT(mIncrementalPhase == IdlePhase);
 }
 // Don't merge too many times in a row, and do at least a minimum
 // number of unmerged CCs in a row.
 static const uint32_t kMinConsecutiveUnmerged = 3;
 static const uint32_t kMaxConsecutiveMerged = 3;
 bool
 nsCycleCollector::ShouldMergeZones(ccType aCCType)
 {
     if (!mJSRuntime) {
         return false;
     }
     MOZ_ASSERT(mUnmergedNeeded <= kMinConsecutiveUnmerged);
     MOZ_ASSERT(mMergedInARow <= kMaxConsecutiveMerged);
     if (mMergedInARow == kMaxConsecutiveMerged) {
         MOZ_ASSERT(mUnmergedNeeded == 0);
         mUnmergedNeeded = kMinConsecutiveUnmerged;
     }
     if (mUnmergedNeeded > 0) {
         mUnmergedNeeded--;
         mMergedInARow = 0;
         return false;
     }
     if (aCCType == SliceCC && mJSRuntime->UsefulToMergeZones()) {
         mMergedInARow++;
         return true;
     } else {
         mMergedInARow = 0;
         return false;
     }
 }
 void
 nsCycleCollector::BeginCollection(ccType aCCType,
                                   nsICycleCollectorListener *aManualListener)
 {
     TimeLog timeLog;
     MOZ_ASSERT(mIncrementalPhase == IdlePhase);
     mCollectionStart = TimeStamp::Now();
     if (mJSRuntime) {
         mJSRuntime->BeginCycleCollectionCallback();
         timeLog.Checkpoint("BeginCycleCollectionCallback()");
     }
     bool isShutdown = (aCCType == ShutdownCC);
     // Set up the listener for this CC.
     MOZ_ASSERT_IF(isShutdown, !aManualListener);
     MOZ_ASSERT(!mListener, "Forgot to clear a previous listener?");
     mListener = aManualListener;
     aManualListener = nullptr;
     if (!mListener && mParams.LogThisCC(isShutdown)) {
         nsRefPtr<nsCycleCollectorLogger> logger = new nsCycleCollectorLogger();
         if (mParams.AllTracesThisCC(isShutdown)) {
             logger->SetAllTraces();
         }
         mListener = logger.forget();
     }
     bool forceGC = isShutdown;
     if (!forceGC && mListener) {
         // On a WantAllTraces CC, force a synchronous global GC to prevent
         // hijinks from ForgetSkippable and compartmental GCs.
         mListener->GetWantAllTraces(&forceGC);
     }
     FixGrayBits(forceGC);
     FreeSnowWhite(true);
     if (mListener && NS_FAILED(mListener->Begin())) {
         mListener = nullptr;
     }
     // Set up the data structures for building the graph.
     mGraph.Init();
     mResults.Init();
     bool mergeZones = ShouldMergeZones(aCCType);
     mResults.mMergedZones = mergeZones;
     MOZ_ASSERT(!mBuilder, "Forgot to clear mBuilder");
     mBuilder = new GCGraphBuilder(mGraph, mResults, mJSRuntime, mListener, mergeZones);
     if (mJSRuntime) {
         mJSRuntime->TraverseRoots(*mBuilder);
         timeLog.Checkpoint("mJSRuntime->TraverseRoots()");
     }
     AutoRestore<bool> ar(mScanInProgress);
     MOZ_ASSERT(!mScanInProgress);
     mScanInProgress = true;
     mPurpleBuf.SelectPointers(*mBuilder);
     timeLog.Checkpoint("SelectPointers()");
     // We've finished adding roots, and everything in the graph is a root.
     mGraph.mRootCount = mGraph.MapCount();
     mCurrNode = new NodePool::Enumerator(mGraph.mNodes);
     mIncrementalPhase = GraphBuildingPhase;
 }
 uint32_t
 nsCycleCollector::SuspectedCount()
 {
     CheckThreadSafety();
     return mPurpleBuf.Count();
 }
 void
 nsCycleCollector::Shutdown()
 {
     CheckThreadSafety();
     // Always delete snow white objects.
     FreeSnowWhite(true);
 #ifndef DEBUG
     if (PR_GetEnv("MOZ_CC_RUN_DURING_SHUTDOWN"))
 #endif
     {
         ShutdownCollect();
     }
 }
 void
 nsCycleCollector::RemoveObjectFromGraph(void *aObj)
 {
     if (mIncrementalPhase == IdlePhase) {
         return;
     }
     if (PtrInfo *pinfo = mGraph.FindNode(aObj)) {
         mGraph.RemoveNodeFromMap(aObj);
         pinfo->mPointer = nullptr;
         pinfo->mParticipant = nullptr;
     }
 }
 void
 nsCycleCollector::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf,
                                       size_t *aObjectSize,
                                       size_t *aGraphNodesSize,
                                       size_t *aGraphEdgesSize,
                                       size_t *aWeakMapsSize,
                                       size_t *aPurpleBufferSize) const
 {
     *aObjectSize = aMallocSizeOf(this);
     mGraph.SizeOfExcludingThis(aMallocSizeOf, aGraphNodesSize, aGraphEdgesSize,
                                aWeakMapsSize);
     *aPurpleBufferSize = mPurpleBuf.SizeOfExcludingThis(aMallocSizeOf);
     // These fields are deliberately not measured:
     // - mJSRuntime: because it's non-owning and measured by JS reporters.
     // - mParams: because it only contains scalars.
 }
 JSPurpleBuffer*
 nsCycleCollector::GetJSPurpleBuffer()
 {
   if (!mJSPurpleBuffer) {
     // JSPurpleBuffer keeps itself alive, but we need to create it in such way
     // that it ends up in the normal purple buffer. That happens when
     // nsRefPtr goes out of the scope and calls Release.
     nsRefPtr<JSPurpleBuffer> pb = new JSPurpleBuffer(mJSPurpleBuffer);
   }
   return mJSPurpleBuffer;
 }
 ////////////////////////////////////////////////////////////////////////
 // Module public API (exported in nsCycleCollector.h)
 // Just functions that redirect into the singleton, once it's built.
 ////////////////////////////////////////////////////////////////////////
 void
 nsCycleCollector_registerJSRuntime(CycleCollectedJSRuntime *rt)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     // But we shouldn't already have a runtime.
     MOZ_ASSERT(!data->mRuntime);
     data->mRuntime = rt;
     data->mCollector->RegisterJSRuntime(rt);
 }
 void
 nsCycleCollector_forgetJSRuntime()
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     // And we shouldn't have already forgotten our runtime.
     MOZ_ASSERT(data->mRuntime);
     // But it may have shutdown already.
     if (data->mCollector) {
         data->mCollector->ForgetJSRuntime();
         data->mRuntime = nullptr;
     } else {
         data->mRuntime = nullptr;
         delete data;
         sCollectorData.set(nullptr);
     }
 }
 /* static */ CycleCollectedJSRuntime*
 CycleCollectedJSRuntime::Get()
 {
     CollectorData* data = sCollectorData.get();
     if (data) {
         return data->mRuntime;
     }
     return nullptr;
 }
 namespace mozilla {
 namespace cyclecollector {
 void
 HoldJSObjectsImpl(void* aHolder, nsScriptObjectTracer* aTracer)
 {
     CollectorData* data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     // And we should have a runtime.
     MOZ_ASSERT(data->mRuntime);
     data->mRuntime->AddJSHolder(aHolder, aTracer);
 }
 void
 HoldJSObjectsImpl(nsISupports* aHolder)
 {
     nsXPCOMCycleCollectionParticipant* participant;
     CallQueryInterface(aHolder, &participant);
     MOZ_ASSERT(participant, "Failed to QI to nsXPCOMCycleCollectionParticipant!");
     MOZ_ASSERT(participant->CheckForRightISupports(aHolder),
                "The result of QIing a JS holder should be the same as ToSupports");
     HoldJSObjectsImpl(aHolder, participant);
 }
 void
 DropJSObjectsImpl(void* aHolder)
 {
     CollectorData* data = sCollectorData.get();
     // We should have started the cycle collector by now, and not completely
     // shut down.
     MOZ_ASSERT(data);
     // And we should have a runtime.
     MOZ_ASSERT(data->mRuntime);
     data->mRuntime->RemoveJSHolder(aHolder);
 }
 void
 DropJSObjectsImpl(nsISupports* aHolder)
 {
 #ifdef DEBUG
     nsXPCOMCycleCollectionParticipant* participant;
     CallQueryInterface(aHolder, &participant);
     MOZ_ASSERT(participant, "Failed to QI to nsXPCOMCycleCollectionParticipant!");
     MOZ_ASSERT(participant->CheckForRightISupports(aHolder),
                "The result of QIing a JS holder should be the same as ToSupports");
 #endif
     DropJSObjectsImpl(static_cast<void*>(aHolder));
 }
 #ifdef DEBUG
 bool
 IsJSHolder(void* aHolder)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now, and not completely
     // shut down.
     MOZ_ASSERT(data);
     // And we should have a runtime.
     MOZ_ASSERT(data->mRuntime);
     return data->mRuntime->IsJSHolder(aHolder);
 }
 #endif
 void
 DeferredFinalize(nsISupports* aSupports)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now, and not completely
     // shut down.
     MOZ_ASSERT(data);
     // And we should have a runtime.
     MOZ_ASSERT(data->mRuntime);
     data->mRuntime->DeferredFinalize(aSupports);
 }
 void
 DeferredFinalize(DeferredFinalizeAppendFunction aAppendFunc,
                  DeferredFinalizeFunction aFunc,
                  void* aThing)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now, and not completely
     // shut down.
     MOZ_ASSERT(data);
     // And we should have a runtime.
     MOZ_ASSERT(data->mRuntime);
     data->mRuntime->DeferredFinalize(aAppendFunc, aFunc, aThing);
 }
 } // namespace cyclecollector
 } // namespace mozilla
 MOZ_NEVER_INLINE static void
 SuspectAfterShutdown(void* n, nsCycleCollectionParticipant* cp,
                      nsCycleCollectingAutoRefCnt* aRefCnt,
                      bool* aShouldDelete)
 {
     if (aRefCnt->get() == 0) {
         if (!aShouldDelete) {
             // The CC is shut down, so we can't be in the middle of an ICC.
             CanonicalizeParticipant(&n, &cp);
             aRefCnt->stabilizeForDeletion();
             cp->DeleteCycleCollectable(n);
         } else {
             *aShouldDelete = true;
         }
     } else {
         // Make sure we'll get called again.
         aRefCnt->RemoveFromPurpleBuffer();
     }
 }
 void
 NS_CycleCollectorSuspect3(void *n, nsCycleCollectionParticipant *cp,
                           nsCycleCollectingAutoRefCnt *aRefCnt,
                           bool* aShouldDelete)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     if (MOZ_LIKELY(data->mCollector)) {
         data->mCollector->Suspect(n, cp, aRefCnt);
         return;
     }
     SuspectAfterShutdown(n, cp, aRefCnt, aShouldDelete);
 }
 uint32_t
 nsCycleCollector_suspectedCount()
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     if (!data->mCollector) {
         return 0;
     }
     return data->mCollector->SuspectedCount();
 }
 bool
 nsCycleCollector_init()
 {
     MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
     MOZ_ASSERT(!sCollectorData.initialized(), "Called twice!?");
     return sCollectorData.init();
 }
 void
 nsCycleCollector_startup()
 {
     MOZ_ASSERT(sCollectorData.initialized(),
                "Forgot to call nsCycleCollector_init!");
     if (sCollectorData.get()) {
         MOZ_CRASH();
     }
     CollectorData* data = new CollectorData;
     data->mCollector = new nsCycleCollector();
     data->mRuntime = nullptr;
     sCollectorData.set(data);
 }
 void
 nsCycleCollector_setBeforeUnlinkCallback(CC_BeforeUnlinkCallback aCB)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     data->mCollector->SetBeforeUnlinkCallback(aCB);
 }
 void
 nsCycleCollector_setForgetSkippableCallback(CC_ForgetSkippableCallback aCB)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     data->mCollector->SetForgetSkippableCallback(aCB);
 }
 void
 nsCycleCollector_forgetSkippable(bool aRemoveChildlessNodes,
                                  bool aAsyncSnowWhiteFreeing)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     PROFILER_LABEL("CC", "nsCycleCollector_forgetSkippable");
     TimeLog timeLog;
     data->mCollector->ForgetSkippable(aRemoveChildlessNodes,
                                       aAsyncSnowWhiteFreeing);
     timeLog.Checkpoint("ForgetSkippable()");
 }
 void
 nsCycleCollector_dispatchDeferredDeletion(bool aContinuation)
 {
     CollectorData *data = sCollectorData.get();
     if (!data || !data->mRuntime) {
         return;
     }
     data->mRuntime->DispatchDeferredDeletion(aContinuation);
 }
 bool
 nsCycleCollector_doDeferredDeletion()
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     MOZ_ASSERT(data->mRuntime);
     return data->mCollector->FreeSnowWhite(false);
 }
 void
 nsCycleCollector_collect(nsICycleCollectorListener *aManualListener)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     PROFILER_LABEL("CC", "nsCycleCollector_collect");
     SliceBudget unlimitedBudget;
     data->mCollector->Collect(ManualCC, unlimitedBudget, aManualListener);
 }
 void
 nsCycleCollector_collectSlice(int64_t aSliceTime)
 {
     CollectorData *data = sCollectorData.get();
     // We should have started the cycle collector by now.
     MOZ_ASSERT(data);
     MOZ_ASSERT(data->mCollector);
     PROFILER_LABEL("CC", "nsCycleCollector_collectSlice");
     SliceBudget budget;
     if (aSliceTime > 0) {
         budget = SliceBudget::TimeBudget(aSliceTime);
     } else if (aSliceTime == 0) {
         budget = SliceBudget::WorkBudget(1);
     }
     data->mCollector->Collect(SliceCC, budget, nullptr);
 }
 void
 nsCycleCollector_prepareForGarbageCollection()
 {
     CollectorData *data = sCollectorData.get();
     MOZ_ASSERT(data);
     if (!data->mCollector) {
         return;
     }
     data->mCollector->PrepareForGarbageCollection();
 }
 void
 nsCycleCollector_shutdown()
 {
     CollectorData *data = sCollectorData.get();
     if (data) {
         MOZ_ASSERT(data->mCollector);
         PROFILER_LABEL("CC", "nsCycleCollector_shutdown");
         data->mCollector->Shutdown();
         data->mCollector = nullptr;
         if (!data->mRuntime) {
           delete data;
           sCollectorData.set(nullptr);
         }
     }
 }

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xpcom/base/nsCycleCollector.cpp@6474c204b198 (annotated)

xpcom/base/nsCycleCollector.cpp