Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1107 insertions, 0 deletions

diff --git a/xpcom/base/nsCycleCollectionParticipant.h b/xpcom/base/nsCycleCollectionParticipant.h
new file mode 100644
index 0000000000..e4d293f42e
--- /dev/null
+++ b/xpcom/base/nsCycleCollectionParticipant.h
@@ -0,0 +1,1107 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsCycleCollectionParticipant_h__
+#define nsCycleCollectionParticipant_h__
+
+#include <type_traits>
+#include "js/HeapAPI.h"
+#include "js/TypeDecls.h"
+#include "mozilla/MacroForEach.h"
+#include "nsCycleCollectionNoteChild.h"
+#include "nsDebug.h"
+#include "nsID.h"
+#include "nscore.h"
+
+/**
+ * Note: the following two IIDs only differ in one bit in the last byte.  This
+ * is a hack and is intentional in order to speed up the comparison inside
+ * NS_INTERFACE_TABLE_HEAD_CYCLE_COLLECTION_INHERITED.
+ */
+#define NS_XPCOMCYCLECOLLECTIONPARTICIPANT_IID       \
+  {                                                  \
+    0xc61eac14, 0x5f7a, 0x4481, {                    \
+      0x96, 0x5e, 0x7e, 0xaa, 0x6e, 0xff, 0xa8, 0x5e \
+    }                                                \
+  }
+
+/**
+ * Special IID to get at the base nsISupports for a class. Usually this is the
+ * canonical nsISupports pointer, but in the case of tearoffs for example it is
+ * the base nsISupports pointer of the tearoff. This allow the cycle collector
+ * to have separate nsCycleCollectionParticipant's for tearoffs or aggregated
+ * classes.
+ */
+#define NS_CYCLECOLLECTIONISUPPORTS_IID              \
+  {                                                  \
+    0xc61eac14, 0x5f7a, 0x4481, {                    \
+      0x96, 0x5e, 0x7e, 0xaa, 0x6e, 0xff, 0xa8, 0x5f \
+    }                                                \
+  }
+
+namespace mozilla {
+enum class CCReason : uint8_t {
+  NO_REASON,
+
+  // Purple buffer "overflow": enough objects are suspected to be cycle
+  // collectable to trigger an immediate CC.
+  MANY_SUSPECTED,
+
+  // The previous collection was kCCForced ago, and there are at least
+  // kCCForcedPurpleLimit objects suspected of being cycle collectable.
+  TIMED,
+
+  // Run a CC after a GC has completed.
+  GC_FINISHED,
+
+  // Run a slice of a collection.
+  SLICE,
+
+  // Manual reasons are explicitly triggered with a custom listener (as opposed
+  // to exceeding some internal threshold.) If a CC is already in progress,
+  // continue it. Otherwise, start a new one.
+  FIRST_MANUAL_REASON = 128,
+
+  // We want to GC, but must finish any ongoing cycle collection first.
+  GC_WAITING = FIRST_MANUAL_REASON,
+
+  // CC requested via an API. Used by tests.
+  API,
+
+  // Collecting in order to dump the heap.
+  DUMP_HEAP,
+
+  // Low memory situation detected.
+  MEM_PRESSURE,
+
+  // IPC message to a content process to trigger a CC. The original reason is
+  // not tracked.
+  IPC_MESSAGE,
+
+  // Cycle collection on a worker. The triggering reason is not tracked.
+  WORKER,
+
+  // Used for finding leaks.
+  SHUTDOWN
+};
+
+#define FOR_EACH_CCREASON(MACRO) \
+  MACRO(NO_REASON)               \
+  MACRO(MANY_SUSPECTED)          \
+  MACRO(TIMED)                   \
+  MACRO(GC_FINISHED)             \
+  MACRO(SLICE)                   \
+  MACRO(GC_WAITING)              \
+  MACRO(API)                     \
+  MACRO(DUMP_HEAP)               \
+  MACRO(MEM_PRESSURE)            \
+  MACRO(IPC_MESSAGE)             \
+  MACRO(WORKER)                  \
+  MACRO(SHUTDOWN)
+
+static inline bool IsManualCCReason(CCReason reason) {
+  return reason >= CCReason::FIRST_MANUAL_REASON;
+}
+
+static inline const char* CCReasonToString(CCReason aReason) {
+  switch (aReason) {
+#define SET_REASON_STR(name) \
+  case CCReason::name:       \
+    return #name;            \
+    break;
+    FOR_EACH_CCREASON(SET_REASON_STR)
+#undef SET_REASON_STR
+    default:
+      return "<unknown-reason>";
+  }
+}
+
+}  // namespace mozilla
+
+/**
+ * Just holds the IID so NS_GET_IID works.
+ */
+class nsCycleCollectionISupports {
+ public:
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_CYCLECOLLECTIONISUPPORTS_IID)
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsCycleCollectionISupports,
+                              NS_CYCLECOLLECTIONISUPPORTS_IID)
+
+class nsCycleCollectionTraversalCallback;
+class nsISupports;
+class nsWrapperCache;
+
+namespace JS {
+template <class T>
+class Heap;
+template <typename T>
+class TenuredHeap;
+} /* namespace JS */
+
+/*
+ * A struct defining pure virtual methods which are called when tracing cycle
+ * collection paticipants.  The appropriate method is called depending on the
+ * type of JS GC thing.
+ */
+struct TraceCallbacks {
+  virtual void Trace(JS::Heap<JS::Value>* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+  virtual void Trace(JS::Heap<jsid>* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+  virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+  virtual void Trace(nsWrapperCache* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+  virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+  virtual void Trace(JS::Heap<JSString*>* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+  virtual void Trace(JS::Heap<JSScript*>* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+  virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char* aName,
+                     void* aClosure) const = 0;
+};
+
+/*
+ * An implementation of TraceCallbacks that calls a single function for all JS
+ * GC thing types encountered. Implemented in
+ * nsCycleCollectorTraceJSHelpers.cpp.
+ */
+struct TraceCallbackFunc : public TraceCallbacks {
+  typedef void (*Func)(JS::GCCellPtr aPtr, const char* aName, void* aClosure);
+
+  explicit TraceCallbackFunc(Func aCb) : mCallback(aCb) {}
+
+  virtual void Trace(JS::Heap<JS::Value>* aPtr, const char* aName,
+                     void* aClosure) const override;
+  virtual void Trace(JS::Heap<jsid>* aPtr, const char* aName,
+                     void* aClosure) const override;
+  virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
+                     void* aClosure) const override;
+  virtual void Trace(nsWrapperCache* aPtr, const char* aName,
+                     void* aClosure) const override;
+  virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
+                     void* aClosure) const override;
+  virtual void Trace(JS::Heap<JSString*>* aPtr, const char* aName,
+                     void* aClosure) const override;
+  virtual void Trace(JS::Heap<JSScript*>* aPtr, const char* aName,
+                     void* aClosure) const override;
+  virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char* aName,
+                     void* aClosure) const override;
+
+ private:
+  Func mCallback;
+};
+
+/**
+ * Participant implementation classes
+ */
+class NS_NO_VTABLE nsCycleCollectionParticipant {
+ public:
+  using Flags = uint8_t;
+  static constexpr Flags FlagMightSkip = 1u << 0;
+  static constexpr Flags FlagTraverseShouldTrace = 1u << 1;
+  // The object is a single zone js holder if FlagMaybeSingleZoneJSHolder is set
+  // and FlagMultiZoneJSHolder isn't set. This setup is needed so that
+  // inheriting classes can unset single zone behavior.
+  static constexpr Flags FlagMaybeSingleZoneJSHolder = 1u << 2;
+  static constexpr Flags FlagMultiZoneJSHolder = 1u << 3;
+  static constexpr Flags AllFlags = FlagMightSkip | FlagTraverseShouldTrace |
+                                    FlagMaybeSingleZoneJSHolder |
+                                    FlagMultiZoneJSHolder;
+
+  constexpr explicit nsCycleCollectionParticipant(Flags aFlags)
+      : mFlags(aFlags) {
+    MOZ_ASSERT((aFlags & ~AllFlags) == 0);
+  }
+
+  NS_IMETHOD TraverseNative(void* aPtr,
+                            nsCycleCollectionTraversalCallback& aCb) = 0;
+
+  nsresult TraverseNativeAndJS(void* aPtr,
+                               nsCycleCollectionTraversalCallback& aCb) {
+    nsresult rv = TraverseNative(aPtr, aCb);
+    if (TraverseShouldTrace()) {
+      // Note, we always call Trace, even if Traverse returned
+      // NS_SUCCESS_INTERRUPTED_TRAVERSE.
+      TraceCallbackFunc noteJsChild(&nsCycleCollectionParticipant::NoteJSChild);
+      Trace(aPtr, noteJsChild, &aCb);
+    }
+    return rv;
+  }
+
+  // Implemented in nsCycleCollectorTraceJSHelpers.cpp.
+  static void NoteJSChild(JS::GCCellPtr aGCThing, const char* aName,
+                          void* aClosure);
+
+  NS_IMETHOD_(void) Root(void* aPtr) = 0;
+  NS_IMETHOD_(void) Unlink(void* aPtr) = 0;
+  NS_IMETHOD_(void) Unroot(void* aPtr) = 0;
+  NS_IMETHOD_(const char*) ClassName() = 0;
+
+  NS_IMETHOD_(void)
+  Trace(void* aPtr, const TraceCallbacks& aCb, void* aClosure) {}
+
+  // CanSkip is called during nsCycleCollector_forgetSkippable.  If it returns
+  // true, aPtr is removed from the purple buffer and therefore might be left
+  // out from the cycle collector graph the next time that's constructed (unless
+  // it's reachable in some other way).
+  //
+  // CanSkip is allowed to expand the set of certainly-alive objects by removing
+  // other objects from the purple buffer, marking JS things black (in the GC
+  // sense), and so forth.  Furthermore, if aRemovingAllowed is true, this call
+  // is allowed to remove aPtr itself from the purple buffer.
+  //
+  // Things can return true from CanSkip if either they know they have no
+  // outgoing edges at all in the cycle collection graph (because then they
+  // can't be parts of a cycle) or they know for sure they're alive.
+  bool CanSkip(void* aPtr, bool aRemovingAllowed) {
+    return MightSkip() ? CanSkipReal(aPtr, aRemovingAllowed) : false;
+  }
+
+  // CanSkipInCC is called during construction of the initial set of roots for
+  // the cycle collector graph.  If it returns true, aPtr is left out of that
+  // set of roots.  Note that the set of roots includes whatever is in the
+  // purple buffer (after earlier CanSkip calls) plus various other sources of
+  // roots, so an object can end up having CanSkipInCC called on it even if it
+  // returned true from CanSkip.  One example of this would be an object that
+  // can potentially trace JS things.
+  //
+  // CanSkipInCC is allowed to remove other objects from the purple buffer but
+  // should not remove aPtr and should not mark JS things black.  It should also
+  // not modify any reference counts.
+  //
+  // Things can return true from CanSkipInCC if either they know they have no
+  // outgoing edges at all in the cycle collection graph or they know for sure
+  // they're alive _and_ none of their outgoing edges are to gray (in the GC
+  // sense) gcthings.  See also nsWrapperCache::HasNothingToTrace and
+  // nsWrapperCache::HasKnownLiveWrapperAndDoesNotNeedTracing. The restriction
+  // on not having outgoing edges to gray gcthings is because if we _do_ have
+  // them that means we have a "strong" edge to a JS thing and since we're alive
+  // we need to trace through it and mark keep them alive.  Outgoing edges to
+  // C++ things don't matter here, because the criteria for when a CC
+  // participant is considered alive are slightly different for JS and C++
+  // things: JS things are only considered alive when reachable via an edge from
+  // a live thing, while C++ things are also considered alive when their
+  // refcount exceeds the number of edges via which they are reachable.
+  bool CanSkipInCC(void* aPtr) {
+    return MightSkip() ? CanSkipInCCReal(aPtr) : false;
+  }
+
+  // CanSkipThis is called during construction of the cycle collector graph,
+  // when we traverse an edge to aPtr and consider adding it to the graph.  If
+  // it returns true, aPtr is not added to the graph.
+  //
+  // CanSkipThis is not allowed to change the liveness or reference count of any
+  // objects.
+  //
+  // Things can return true from CanSkipThis if either they know they have no
+  // outgoing edges at all in the cycle collection graph or they know for sure
+  // they're alive.
+  //
+  // Note that CanSkipThis doesn't have to worry about outgoing edges to gray GC
+  // things, because if this object could have those it already got added to the
+  // graph during root set construction.  An object should never have
+  // CanSkipThis called on it if it has outgoing strong references to JS things.
+  bool CanSkipThis(void* aPtr) {
+    return MightSkip() ? CanSkipThisReal(aPtr) : false;
+  }
+
+  NS_IMETHOD_(void) DeleteCycleCollectable(void* aPtr) = 0;
+
+  bool IsSingleZoneJSHolder() const {
+    return (mFlags & FlagMaybeSingleZoneJSHolder) &&
+           !(mFlags & FlagMultiZoneJSHolder);
+  }
+
+ protected:
+  NS_IMETHOD_(bool) CanSkipReal(void* aPtr, bool aRemovingAllowed) {
+    NS_ASSERTION(false, "Forgot to implement CanSkipReal?");
+    return false;
+  }
+  NS_IMETHOD_(bool) CanSkipInCCReal(void* aPtr) {
+    NS_ASSERTION(false, "Forgot to implement CanSkipInCCReal?");
+    return false;
+  }
+  NS_IMETHOD_(bool) CanSkipThisReal(void* aPtr) {
+    NS_ASSERTION(false, "Forgot to implement CanSkipThisReal?");
+    return false;
+  }
+
+ private:
+  bool MightSkip() const { return mFlags & FlagMightSkip; }
+  bool TraverseShouldTrace() const { return mFlags & FlagTraverseShouldTrace; }
+
+  const Flags mFlags;
+};
+
+class NS_NO_VTABLE nsScriptObjectTracer : public nsCycleCollectionParticipant {
+ public:
+  constexpr explicit nsScriptObjectTracer(Flags aFlags)
+      : nsCycleCollectionParticipant(aFlags | FlagTraverseShouldTrace) {}
+
+  NS_IMETHOD_(void)
+  Trace(void* aPtr, const TraceCallbacks& aCb, void* aClosure) override = 0;
+};
+
+class NS_NO_VTABLE nsXPCOMCycleCollectionParticipant
+    : public nsScriptObjectTracer {
+ public:
+  constexpr explicit nsXPCOMCycleCollectionParticipant(Flags aFlags)
+      : nsScriptObjectTracer(aFlags) {}
+
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_XPCOMCYCLECOLLECTIONPARTICIPANT_IID)
+
+  NS_IMETHOD_(void) Root(void* aPtr) override;
+  NS_IMETHOD_(void) Unroot(void* aPtr) override;
+
+  NS_IMETHOD_(void)
+  Trace(void* aPtr, const TraceCallbacks& aCb, void* aClosure) override;
+
+  static bool CheckForRightISupports(nsISupports* aSupports);
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsXPCOMCycleCollectionParticipant,
+                              NS_XPCOMCYCLECOLLECTIONPARTICIPANT_IID)
+
+///////////////////////////////////////////////////////////////////////////////
+// Helpers for implementing a QI to nsXPCOMCycleCollectionParticipant
+///////////////////////////////////////////////////////////////////////////////
+
+#define NS_CYCLE_COLLECTION_CLASSNAME(_class) \
+  _class::NS_CYCLE_COLLECTION_INNERCLASS
+
+// The IIDs for nsXPCOMCycleCollectionParticipant and nsCycleCollectionISupports
+// are special in that they only differ in their last byte.  This allows for the
+// optimization below where we first check the first three words of the IID and
+// if we find a match we check the last word to decide which case we have to
+// deal with.
+#define NS_INTERFACE_MAP_ENTRIES_CYCLE_COLLECTION(_class)                      \
+  if (TopThreeWordsEquals(                                                     \
+          aIID, NS_GET_IID(nsXPCOMCycleCollectionParticipant),                 \
+          NS_GET_IID(                                                          \
+              nsCycleCollectionISupports)) && /* The calls to LowWordEquals    \
+                                                 here are repeated inside the  \
+                                                 if branch. This is due to the \
+                                                 fact that we need to maintain \
+                                                 the if/else chain for these   \
+                                                 macros, so that the control   \
+                                                 flow never enters the if      \
+                                                 branch unless if we're        \
+                                                 certain one of the            \
+                                                 LowWordEquals() branches will \
+                                                 get executed. */              \
+      (LowWordEquals(aIID, NS_GET_IID(nsXPCOMCycleCollectionParticipant)) ||   \
+       LowWordEquals(aIID, NS_GET_IID(nsCycleCollectionISupports)))) {         \
+    if (LowWordEquals(aIID, NS_GET_IID(nsXPCOMCycleCollectionParticipant))) {  \
+      *aInstancePtr = NS_CYCLE_COLLECTION_PARTICIPANT(_class);                 \
+      return NS_OK;                                                            \
+    }                                                                          \
+    if (LowWordEquals(aIID, NS_GET_IID(nsCycleCollectionISupports))) {         \
+      *aInstancePtr = NS_CYCLE_COLLECTION_CLASSNAME(_class)::Upcast(this);     \
+      return NS_OK;                                                            \
+    }                                                                          \
+    /* Avoid warnings about foundInterface being left uninitialized. */        \
+    foundInterface = nullptr;                                                  \
+  } else
+
+#define NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(_class) \
+  NS_INTERFACE_MAP_BEGIN(_class)                        \
+    NS_INTERFACE_MAP_ENTRIES_CYCLE_COLLECTION(_class)
+
+#define NS_INTERFACE_TABLE_TO_MAP_SEGUE_CYCLE_COLLECTION(_class) \
+  if (rv == NS_OK) return rv;                                    \
+  nsISupports* foundInterface;                                   \
+  NS_INTERFACE_MAP_ENTRIES_CYCLE_COLLECTION(_class)
+
+// The IIDs for nsXPCOMCycleCollectionParticipant and nsCycleCollectionISupports
+// are special in that they only differ in their last byte.  This allows for the
+// optimization below where we first check the first three words of the IID and
+// if we find a match we check the last word to decide which case we have to
+// deal with.
+#define NS_INTERFACE_TABLE_HEAD_CYCLE_COLLECTION_INHERITED(_class)           \
+  NS_IMETHODIMP _class::QueryInterface(REFNSIID aIID, void** aInstancePtr) { \
+    MOZ_ASSERT(aInstancePtr, "null out param");                              \
+                                                                             \
+    if (TopThreeWordsEquals(aIID,                                            \
+                            NS_GET_IID(nsXPCOMCycleCollectionParticipant),   \
+                            NS_GET_IID(nsCycleCollectionISupports))) {       \
+      if (LowWordEquals(aIID,                                                \
+                        NS_GET_IID(nsXPCOMCycleCollectionParticipant))) {    \
+        *aInstancePtr = NS_CYCLE_COLLECTION_PARTICIPANT(_class);             \
+        return NS_OK;                                                        \
+      }                                                                      \
+      if (LowWordEquals(aIID, NS_GET_IID(nsCycleCollectionISupports))) {     \
+        *aInstancePtr = NS_CYCLE_COLLECTION_CLASSNAME(_class)::Upcast(this); \
+        return NS_OK;                                                        \
+      }                                                                      \
+    }                                                                        \
+    nsresult rv = NS_ERROR_FAILURE;
+
+#define NS_CYCLE_COLLECTION_UPCAST(obj, clazz) \
+  NS_CYCLE_COLLECTION_CLASSNAME(clazz)::Upcast(obj)
+
+#ifdef DEBUG
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT(_ptr) _ptr->CheckForRightParticipant()
+#else
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT(_ptr)
+#endif
+
+// The default implementation of this class template is empty, because it
+// should never be used: see the partial specializations below.
+template <typename T, bool IsXPCOM = std::is_base_of<nsISupports, T>::value>
+struct DowncastCCParticipantImpl {};
+
+// Specialization for XPCOM CC participants
+template <typename T>
+struct DowncastCCParticipantImpl<T, true> {
+  static T* Run(void* aPtr) {
+    nsISupports* s = static_cast<nsISupports*>(aPtr);
+    MOZ_ASSERT(NS_CYCLE_COLLECTION_CLASSNAME(T)::CheckForRightISupports(s),
+               "not the nsISupports pointer we expect");
+    T* rval = NS_CYCLE_COLLECTION_CLASSNAME(T)::Downcast(s);
+    NS_CHECK_FOR_RIGHT_PARTICIPANT(rval);
+    return rval;
+  }
+};
+
+// Specialization for native CC participants
+template <typename T>
+struct DowncastCCParticipantImpl<T, false> {
+  static T* Run(void* aPtr) { return static_cast<T*>(aPtr); }
+};
+
+template <typename T>
+T* DowncastCCParticipant(void* aPtr) {
+  return DowncastCCParticipantImpl<T>::Run(aPtr);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Helpers for implementing CanSkip methods
+///////////////////////////////////////////////////////////////////////////////
+
+// See documentation for nsCycleCollectionParticipant::CanSkip for documentation
+// about this method.
+#define NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_BEGIN(_class)                       \
+  NS_IMETHODIMP_(bool)                                                        \
+  NS_CYCLE_COLLECTION_CLASSNAME(_class)::CanSkipReal(void* p,                 \
+                                                     bool aRemovingAllowed) { \
+    _class* tmp = DowncastCCParticipant<_class>(p);
+
+#define NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_END \
+  (void)tmp;                                  \
+  return false;                               \
+  }
+
+// See documentation for nsCycleCollectionParticipant::CanSkipInCC for
+// documentation about this method.
+#define NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_BEGIN(_class)       \
+  NS_IMETHODIMP_(bool)                                              \
+  NS_CYCLE_COLLECTION_CLASSNAME(_class)::CanSkipInCCReal(void* p) { \
+    _class* tmp = DowncastCCParticipant<_class>(p);
+
+#define NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_IN_CC_END \
+  (void)tmp;                                        \
+  return false;                                     \
+  }
+
+// See documentation for nsCycleCollectionParticipant::CanSkipThis for
+// documentation about this method.
+#define NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_BEGIN(_class)        \
+  NS_IMETHODIMP_(bool)                                              \
+  NS_CYCLE_COLLECTION_CLASSNAME(_class)::CanSkipThisReal(void* p) { \
+    _class* tmp = DowncastCCParticipant<_class>(p);
+
+#define NS_IMPL_CYCLE_COLLECTION_CAN_SKIP_THIS_END \
+  (void)tmp;                                       \
+  return false;                                    \
+  }
+
+///////////////////////////////////////////////////////////////////////////////
+// Helpers for implementing nsCycleCollectionParticipant::Unlink
+//
+// You need to use NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED if you want
+// the base class Unlink version to be called before your own implementation.
+// You can use NS_IMPL_CYCLE_COLLECTION_UNLINK_END_INHERITED if you want the
+// base class Unlink to get called after your own implementation.  You should
+// never use them together.
+///////////////////////////////////////////////////////////////////////////////
+
+#define NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(_class)      \
+  NS_IMETHODIMP_(void)                                     \
+  NS_CYCLE_COLLECTION_CLASSNAME(_class)::Unlink(void* p) { \
+    _class* tmp = DowncastCCParticipant<_class>(p);
+
+#define NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(_class, _base_class) \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(_class)                              \
+    nsISupports* s = static_cast<nsISupports*>(p);                           \
+    NS_CYCLE_COLLECTION_CLASSNAME(_base_class)::Unlink(s);
+
+#define NS_IMPL_CYCLE_COLLECTION_UNLINK_HELPER(_field) \
+  ImplCycleCollectionUnlink(tmp->_field);
+
+#define NS_IMPL_CYCLE_COLLECTION_UNLINK(...) \
+  MOZ_FOR_EACH(NS_IMPL_CYCLE_COLLECTION_UNLINK_HELPER, (), (__VA_ARGS__))
+
+#define NS_IMPL_CYCLE_COLLECTION_UNLINK_END \
+  (void)tmp;                                \
+  }
+
+#define NS_IMPL_CYCLE_COLLECTION_UNLINK_END_INHERITED(_base_class) \
+  nsISupports* s = static_cast<nsISupports*>(p);                   \
+  NS_CYCLE_COLLECTION_CLASSNAME(_base_class)::Unlink(s);           \
+  (void)tmp;                                                       \
+  }
+
+#define NS_IMPL_CYCLE_COLLECTION_UNLINK_0(_class) \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(_class)   \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+///////////////////////////////////////////////////////////////////////////////
+// Helpers for implementing nsCycleCollectionParticipant::Traverse
+///////////////////////////////////////////////////////////////////////////////
+
+#define NS_IMPL_CYCLE_COLLECTION_DESCRIBE(_class, _refcnt) \
+  cb.DescribeRefCountedNode(_refcnt, #_class);
+
+#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(_class) \
+  NS_IMETHODIMP                                                  \
+  NS_CYCLE_COLLECTION_CLASSNAME(_class)::TraverseNative(         \
+      void* p, nsCycleCollectionTraversalCallback& cb) {         \
+    _class* tmp = DowncastCCParticipant<_class>(p);
+
+#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(_class)    \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(_class) \
+    NS_IMPL_CYCLE_COLLECTION_DESCRIBE(_class, tmp->mRefCnt.get())
+
+// Base class' CC participant should return NS_SUCCESS_INTERRUPTED_TRAVERSE
+// from Traverse if it wants derived classes to not traverse anything from
+// their CC participant.
+
+#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(_class, _base_class) \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(_class)                     \
+    nsISupports* s = static_cast<nsISupports*>(p);                             \
+    if (NS_CYCLE_COLLECTION_CLASSNAME(_base_class)::TraverseNative(s, cb) ==   \
+        NS_SUCCESS_INTERRUPTED_TRAVERSE) {                                     \
+      return NS_SUCCESS_INTERRUPTED_TRAVERSE;                                  \
+    }
+
+#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE_HELPER(_field) \
+  ImplCycleCollectionTraverse(cb, tmp->_field, #_field, 0);
+
+#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE(...) \
+  MOZ_FOR_EACH(NS_IMPL_CYCLE_COLLECTION_TRAVERSE_HELPER, (), (__VA_ARGS__))
+
+#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE_RAWPTR(_field) \
+  CycleCollectionNoteChild(cb, tmp->_field, #_field);
+
+#define NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END \
+  (void)tmp;                                  \
+  return NS_OK;                               \
+  }
+
+///////////////////////////////////////////////////////////////////////////////
+// Helpers for implementing nsScriptObjectTracer::Trace
+///////////////////////////////////////////////////////////////////////////////
+
+#define NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(_class)               \
+  void NS_CYCLE_COLLECTION_CLASSNAME(_class)::Trace(               \
+      void* p, const TraceCallbacks& aCallbacks, void* aClosure) { \
+    _class* tmp = DowncastCCParticipant<_class>(p);
+
+#define NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(_class, _base_class) \
+  NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(_class)                              \
+    nsISupports* s = static_cast<nsISupports*>(p);                          \
+    NS_CYCLE_COLLECTION_CLASSNAME(_base_class)::Trace(s, aCallbacks, aClosure);
+
+#define NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(_field) \
+  aCallbacks.Trace(&tmp->_field, #_field, aClosure);
+
+// NB: The (void)tmp; hack in the TRACE_END macro exists to support
+// implementations that don't need to do anything in their Trace method.
+// Without this hack, some compilers warn about the unused tmp local.
+#define NS_IMPL_CYCLE_COLLECTION_TRACE_END \
+  (void)tmp;                               \
+  }
+
+///////////////////////////////////////////////////////////////////////////////
+// Helpers for implementing a concrete nsCycleCollectionParticipant
+///////////////////////////////////////////////////////////////////////////////
+
+// If a class defines a participant, then QIing an instance of that class to
+// nsXPCOMCycleCollectionParticipant should produce that participant.
+#ifdef DEBUG
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT_BASE \
+    virtual void CheckForRightParticipant()
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT_DERIVED \
+    virtual void CheckForRightParticipant() override
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT_BODY(_class)             \
+    {                                                             \
+      nsXPCOMCycleCollectionParticipant* p;                       \
+      CallQueryInterface(this, &p);                               \
+      MOZ_ASSERT(p == &NS_CYCLE_COLLECTION_INNERNAME,             \
+                 #_class " should QI to its own CC participant"); \
+    }
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL(_class) \
+    NS_CHECK_FOR_RIGHT_PARTICIPANT_BASE               \
+    NS_CHECK_FOR_RIGHT_PARTICIPANT_BODY(_class)
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL_INHERITED(_class) \
+    NS_CHECK_FOR_RIGHT_PARTICIPANT_DERIVED                      \
+    NS_CHECK_FOR_RIGHT_PARTICIPANT_BODY(_class)
+#else
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL(_class)
+#  define NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL_INHERITED(_class)
+#endif
+
+#define NS_DECL_CYCLE_COLLECTION_CLASS_NAME_METHOD(_class) \
+  NS_IMETHOD_(const char*) ClassName() override { return #_class; };
+
+#define NS_DECL_CYCLE_COLLECTION_CLASS_BODY(_class, _base)                     \
+ public:                                                                       \
+  NS_IMETHOD TraverseNative(void* p, nsCycleCollectionTraversalCallback& cb)   \
+      override;                                                                \
+  NS_DECL_CYCLE_COLLECTION_CLASS_NAME_METHOD(_class)                           \
+  NS_IMETHOD_(void) DeleteCycleCollectable(void* p) override {                 \
+    DowncastCCParticipant<_class>(p)->DeleteCycleCollectable();                \
+  }                                                                            \
+  static _class* Downcast(nsISupports* s) {                                    \
+    return static_cast<_class*>(static_cast<_base*>(s));                       \
+  }                                                                            \
+  static nsISupports* Upcast(_class* p) {                                      \
+    return NS_ISUPPORTS_CAST(_base*, p);                                       \
+  }                                                                            \
+  template <typename T>                                                        \
+  friend nsISupports* ToSupports(T* p, NS_CYCLE_COLLECTION_INNERCLASS* dummy); \
+  NS_IMETHOD_(void) Unlink(void* p) override;
+
+#define NS_PARTICIPANT_AS(type, participant) \
+  const_cast<type*>(reinterpret_cast<const type*>(participant))
+
+#define NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)           \
+  static constexpr nsXPCOMCycleCollectionParticipant* GetParticipant() { \
+    return &_class::NS_CYCLE_COLLECTION_INNERNAME;                       \
+  }
+
+/**
+ * We use this macro to force that classes that inherit from a ccable class and
+ * declare their own participant declare themselves as inherited cc classes.
+ * To avoid possibly unnecessary vtables we only do this checking in debug
+ * builds.
+ */
+#ifdef DEBUG
+#  define NOT_INHERITED_CANT_OVERRIDE \
+    virtual void BaseCycleCollectable() final {}
+#else
+#  define NOT_INHERITED_CANT_OVERRIDE
+#endif
+
+#define NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(_class, _base)         \
+  class NS_CYCLE_COLLECTION_INNERCLASS                                  \
+      : public nsXPCOMCycleCollectionParticipant {                      \
+   public:                                                              \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(Flags aFlags = 0) \
+        : nsXPCOMCycleCollectionParticipant(aFlags) {}                  \
+                                                                        \
+   private:                                                             \
+    NS_DECL_CYCLE_COLLECTION_CLASS_BODY(_class, _base)                  \
+    NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)              \
+  };                                                                    \
+  NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL(_class)                           \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;  \
+  NOT_INHERITED_CANT_OVERRIDE
+
+#define NS_DECL_CYCLE_COLLECTION_CLASS(_class) \
+  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(_class, _class)
+
+// Cycle collector helper for ambiguous classes that can sometimes be skipped.
+#define NS_DECL_CYCLE_COLLECTION_SKIPPABLE_CLASS_AMBIGUOUS(_class, _base)   \
+  class NS_CYCLE_COLLECTION_INNERCLASS                                      \
+      : public nsXPCOMCycleCollectionParticipant {                          \
+   public:                                                                  \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(                      \
+        Flags aFlags = FlagMightSkip) /* We always want skippability. */    \
+        : nsXPCOMCycleCollectionParticipant(aFlags | FlagMightSkip) {}      \
+                                                                            \
+   private:                                                                 \
+    NS_DECL_CYCLE_COLLECTION_CLASS_BODY(_class, _base)                      \
+    NS_IMETHOD_(bool) CanSkipReal(void* p, bool aRemovingAllowed) override; \
+    NS_IMETHOD_(bool) CanSkipInCCReal(void* p) override;                    \
+    NS_IMETHOD_(bool) CanSkipThisReal(void* p) override;                    \
+    NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)                  \
+  };                                                                        \
+  NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL(_class)                               \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;      \
+  NOT_INHERITED_CANT_OVERRIDE
+
+#define NS_DECL_CYCLE_COLLECTION_SKIPPABLE_CLASS(_class) \
+  NS_DECL_CYCLE_COLLECTION_SKIPPABLE_CLASS_AMBIGUOUS(_class, _class)
+
+#define NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(_class, _base) \
+  class NS_CYCLE_COLLECTION_INNERCLASS                                        \
+      : public nsXPCOMCycleCollectionParticipant {                            \
+   public:                                                                    \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(Flags aFlags = 0)       \
+        : nsXPCOMCycleCollectionParticipant(aFlags) {}                        \
+                                                                              \
+   private:                                                                   \
+    NS_DECL_CYCLE_COLLECTION_CLASS_BODY(_class, _base)                        \
+    NS_IMETHOD_(void)                                                         \
+    Trace(void* p, const TraceCallbacks& cb, void* closure) override;         \
+    NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)                    \
+  };                                                                          \
+  NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL(_class)                                 \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;        \
+  NOT_INHERITED_CANT_OVERRIDE
+
+#define NS_DECL_CYCLE_COLLECTION_SKIPPABLE_SCRIPT_HOLDER_CLASS_AMBIGUOUS(   \
+    _class, _base)                                                          \
+  class NS_CYCLE_COLLECTION_INNERCLASS                                      \
+      : public nsXPCOMCycleCollectionParticipant {                          \
+   public:                                                                  \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(                      \
+        Flags aFlags = FlagMightSkip) /* We always want skippability. */    \
+        : nsXPCOMCycleCollectionParticipant(aFlags | FlagMightSkip) {}      \
+                                                                            \
+   private:                                                                 \
+    NS_DECL_CYCLE_COLLECTION_CLASS_BODY(_class, _base)                      \
+    NS_IMETHOD_(void)                                                       \
+    Trace(void* p, const TraceCallbacks& cb, void* closure) override;       \
+    NS_IMETHOD_(bool) CanSkipReal(void* p, bool aRemovingAllowed) override; \
+    NS_IMETHOD_(bool) CanSkipInCCReal(void* p) override;                    \
+    NS_IMETHOD_(bool) CanSkipThisReal(void* p) override;                    \
+    NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)                  \
+  };                                                                        \
+  NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL(_class)                               \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;      \
+  NOT_INHERITED_CANT_OVERRIDE
+
+#define NS_DECL_CYCLE_COLLECTION_SKIPPABLE_SCRIPT_HOLDER_CLASS(_class)     \
+  NS_DECL_CYCLE_COLLECTION_SKIPPABLE_SCRIPT_HOLDER_CLASS_AMBIGUOUS(_class, \
+                                                                   _class)
+
+#define NS_DECL_CYCLE_COLLECTION_SKIPPABLE_SCRIPT_HOLDER_CLASS_INHERITED(      \
+    _class, _base_class)                                                       \
+  class NS_CYCLE_COLLECTION_INNERCLASS                                         \
+      : public NS_CYCLE_COLLECTION_CLASSNAME(_base_class) {                    \
+   public:                                                                     \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(                         \
+        Flags aFlags = FlagMightSkip | /* We always want skippability. */      \
+                       FlagMultiZoneJSHolder)                                  \
+        : NS_CYCLE_COLLECTION_CLASSNAME(_base_class)(aFlags | FlagMightSkip) { \
+    }                                                                          \
+                                                                               \
+   private:                                                                    \
+    NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED_BODY(_class, _base_class)         \
+    NS_IMETHOD_(void)                                                          \
+    Trace(void* p, const TraceCallbacks& cb, void* closure) override;          \
+    NS_IMETHOD_(bool) CanSkipReal(void* p, bool aRemovingAllowed) override;    \
+    NS_IMETHOD_(bool) CanSkipInCCReal(void* p) override;                       \
+    NS_IMETHOD_(bool) CanSkipThisReal(void* p) override;                       \
+    NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)                     \
+  };                                                                           \
+  NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL_INHERITED(_class)                        \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
+
+#define NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(_class) \
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(_class, _class)
+
+#define NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED_BODY(_class, _base_class)   \
+ public:                                                                     \
+  NS_IMETHOD TraverseNative(void* p, nsCycleCollectionTraversalCallback& cb) \
+      override;                                                              \
+  NS_DECL_CYCLE_COLLECTION_CLASS_NAME_METHOD(_class)                         \
+  static _class* Downcast(nsISupports* s) {                                  \
+    return static_cast<_class*>(static_cast<_base_class*>(                   \
+        NS_CYCLE_COLLECTION_CLASSNAME(_base_class)::Downcast(s)));           \
+  }                                                                          \
+  NS_IMETHOD_(void) Unlink(void* p) override;
+
+#define NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(_class, _base_class)   \
+  class NS_CYCLE_COLLECTION_INNERCLASS                                  \
+      : public NS_CYCLE_COLLECTION_CLASSNAME(_base_class) {             \
+   public:                                                              \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(Flags aFlags = 0) \
+        : NS_CYCLE_COLLECTION_CLASSNAME(_base_class)(aFlags) {}         \
+                                                                        \
+   private:                                                             \
+    NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED_BODY(_class, _base_class)  \
+    NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)              \
+  };                                                                    \
+  NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL_INHERITED(_class)                 \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
+
+#define NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(_class,         \
+                                                               _base_class)    \
+  class NS_CYCLE_COLLECTION_INNERCLASS                                         \
+      : public NS_CYCLE_COLLECTION_CLASSNAME(_base_class) {                    \
+   public:                                                                     \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(Flags aFlags = 0)        \
+        : NS_CYCLE_COLLECTION_CLASSNAME(_base_class)(aFlags |                  \
+                                                     FlagMultiZoneJSHolder) {} \
+                                                                               \
+   private:                                                                    \
+    NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED_BODY(_class, _base_class)         \
+    NS_IMETHOD_(void)                                                          \
+    Trace(void* p, const TraceCallbacks& cb, void* closure) override;          \
+    NS_IMPL_GET_XPCOM_CYCLE_COLLECTION_PARTICIPANT(_class)                     \
+  };                                                                           \
+  NS_CHECK_FOR_RIGHT_PARTICIPANT_IMPL_INHERITED(_class)                        \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
+
+// Cycle collector participant declarations.
+
+#define NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS_BODY(_class)                   \
+ public:                                                                     \
+  NS_IMETHOD_(void) Root(void* p) override {                                 \
+    static_cast<_class*>(p)->AddRef();                                       \
+  }                                                                          \
+  NS_IMETHOD_(void) Unlink(void* n) override;                                \
+  NS_IMETHOD_(void) Unroot(void* p) override {                               \
+    static_cast<_class*>(p)->Release();                                      \
+  }                                                                          \
+  NS_IMETHOD TraverseNative(void* n, nsCycleCollectionTraversalCallback& cb) \
+      override;                                                              \
+  NS_DECL_CYCLE_COLLECTION_CLASS_NAME_METHOD(_class)                         \
+  NS_IMETHOD_(void) DeleteCycleCollectable(void* n) override {               \
+    DowncastCCParticipant<_class>(n)->DeleteCycleCollectable();              \
+  }                                                                          \
+  static _class* Downcast(void* s) {                                         \
+    return DowncastCCParticipant<_class>(s);                                 \
+  }                                                                          \
+  static void* Upcast(_class* p) { return static_cast<void*>(p); }
+
+#define NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(_class)                          \
+  void DeleteCycleCollectable(void) { delete this; }                           \
+  class NS_CYCLE_COLLECTION_INNERCLASS : public nsCycleCollectionParticipant { \
+   public:                                                                     \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(Flags aFlags = 0)        \
+        : nsCycleCollectionParticipant(aFlags) {}                              \
+                                                                               \
+   private:                                                                    \
+    NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS_BODY(_class)                         \
+    static constexpr nsCycleCollectionParticipant* GetParticipant() {          \
+      return &_class::NS_CYCLE_COLLECTION_INNERNAME;                           \
+    }                                                                          \
+  };                                                                           \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
+
+#define NS_DECL_CYCLE_COLLECTION_SKIPPABLE_NATIVE_CLASS(_class)                \
+  void DeleteCycleCollectable(void) { delete this; }                           \
+  class NS_CYCLE_COLLECTION_INNERCLASS : public nsCycleCollectionParticipant { \
+   public:                                                                     \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(                         \
+        Flags aFlags = FlagMightSkip) /* We always want skippability. */       \
+        : nsCycleCollectionParticipant(aFlags | FlagMightSkip) {}              \
+                                                                               \
+   private:                                                                    \
+    NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS_BODY(_class)                         \
+    NS_IMETHOD_(bool) CanSkipReal(void* p, bool aRemovingAllowed) override;    \
+    NS_IMETHOD_(bool) CanSkipInCCReal(void* p) override;                       \
+    NS_IMETHOD_(bool) CanSkipThisReal(void* p) override;                       \
+    static nsCycleCollectionParticipant* GetParticipant() {                    \
+      return &_class::NS_CYCLE_COLLECTION_INNERNAME;                           \
+    }                                                                          \
+  };                                                                           \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
+
+#define NS_DECL_CYCLE_COLLECTION_SKIPPABLE_NATIVE_CLASS_WITH_CUSTOM_DELETE(    \
+    _class)                                                                    \
+  class NS_CYCLE_COLLECTION_INNERCLASS : public nsCycleCollectionParticipant { \
+   public:                                                                     \
+    constexpr NS_CYCLE_COLLECTION_INNERCLASS()                                 \
+        : nsCycleCollectionParticipant(true) {}                                \
+                                                                               \
+   private:                                                                    \
+    NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS_BODY(_class)                         \
+    NS_IMETHOD_(bool) CanSkipReal(void* p, bool aRemovingAllowed) override;    \
+    NS_IMETHOD_(bool) CanSkipInCCReal(void* p) override;                       \
+    NS_IMETHOD_(bool) CanSkipThisReal(void* p) override;                       \
+    static nsCycleCollectionParticipant* GetParticipant() {                    \
+      return &_class::NS_CYCLE_COLLECTION_INNERNAME;                           \
+    }                                                                          \
+  };                                                                           \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
+
+#define NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(_class)     \
+  void DeleteCycleCollectable(void) { delete this; }                    \
+  class NS_CYCLE_COLLECTION_INNERCLASS : public nsScriptObjectTracer {  \
+   public:                                                              \
+    constexpr explicit NS_CYCLE_COLLECTION_INNERCLASS(Flags aFlags = 0) \
+        : nsScriptObjectTracer(aFlags) {}                               \
+                                                                        \
+   private:                                                             \
+    NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS_BODY(_class)                  \
+    NS_IMETHOD_(void)                                                   \
+    Trace(void* p, const TraceCallbacks& cb, void* closure) override;   \
+    static constexpr nsScriptObjectTracer* GetParticipant() {           \
+      return &_class::NS_CYCLE_COLLECTION_INNERNAME;                    \
+    }                                                                   \
+  };                                                                    \
+  static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
+
+#define NS_IMPL_CYCLE_COLLECTION_CLASS(_class) \
+  _class::NS_CYCLE_COLLECTION_INNERCLASS _class::NS_CYCLE_COLLECTION_INNERNAME;
+
+// By default JS holders are treated as if they may store pointers to multiple
+// zones, but one may optimize GC handling by using single zone holders.
+#define NS_IMPL_CYCLE_COLLECTION_SINGLE_ZONE_SCRIPT_HOLDER_CLASS(_class) \
+  _class::NS_CYCLE_COLLECTION_INNERCLASS                                 \
+      _class::NS_CYCLE_COLLECTION_INNERNAME(                             \
+          nsCycleCollectionParticipant::FlagMaybeSingleZoneJSHolder);
+
+// NB: This is not something you usually want to use.  It is here to allow
+// adding things to the CC graph to help debugging via CC logs, but it does not
+// traverse or unlink anything, so it is useless for anything else.
+#define NS_IMPL_CYCLE_COLLECTION_0(_class)        \
+  NS_IMPL_CYCLE_COLLECTION_CLASS(_class)          \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(_class)   \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_END             \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(_class) \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+#define NS_IMPL_CYCLE_COLLECTION(_class, ...)      \
+  NS_IMPL_CYCLE_COLLECTION_CLASS(_class)           \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(_class)    \
+    NS_IMPL_CYCLE_COLLECTION_UNLINK(__VA_ARGS__)   \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_END              \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(_class)  \
+    NS_IMPL_CYCLE_COLLECTION_TRAVERSE(__VA_ARGS__) \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+// If you are looking for NS_IMPL_CYCLE_COLLECTION_INHERITED_0(_class, _base)
+// you should instead not declare any cycle collected stuff in _class, so it
+// will just inherit the CC declarations from _base.
+
+#define NS_IMPL_CYCLE_COLLECTION_INHERITED(_class, _base, ...)     \
+  NS_IMPL_CYCLE_COLLECTION_CLASS(_class)                           \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(_class, _base)   \
+    NS_IMPL_CYCLE_COLLECTION_UNLINK(__VA_ARGS__)                   \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_END                              \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(_class, _base) \
+    NS_IMPL_CYCLE_COLLECTION_TRAVERSE(__VA_ARGS__)                 \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+#define NS_CYCLE_COLLECTION_NOTE_EDGE_NAME CycleCollectionNoteEdgeName
+
+/**
+ * Convenience macros for defining nISupports methods in a cycle collected
+ * class.
+ */
+
+#define NS_IMPL_QUERY_INTERFACE_CYCLE_COLLECTION_INHERITED(aClass, aSuper, \
+                                                           ...)            \
+  NS_INTERFACE_TABLE_HEAD_CYCLE_COLLECTION_INHERITED(aClass)               \
+    NS_INTERFACE_TABLE_INHERITED(aClass, __VA_ARGS__)                      \
+  NS_INTERFACE_TABLE_TAIL_INHERITING(aSuper)
+
+#define NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED(aClass, aSuper, ...) \
+  NS_IMPL_QUERY_INTERFACE_CYCLE_COLLECTION_INHERITED(aClass, aSuper,      \
+                                                     __VA_ARGS__)         \
+  NS_IMPL_ADDREF_INHERITED(aClass, aSuper)                                \
+  NS_IMPL_RELEASE_INHERITED(aClass, aSuper)
+
+#define NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(aClass, aSuper) \
+  NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(aClass)                      \
+  NS_INTERFACE_MAP_END_INHERITING(aSuper)                              \
+  NS_IMPL_ADDREF_INHERITED(aClass, aSuper)                             \
+  NS_IMPL_RELEASE_INHERITED(aClass, aSuper)
+
+/**
+ * Equivalency of the high three words where two IIDs have the same
+ * top three words but not the same low word.
+ */
+inline bool TopThreeWordsEquals(const nsID& aID, const nsID& aOther1,
+                                const nsID& aOther2) {
+  MOZ_ASSERT((((uint32_t*)&aOther1.m0)[0] == ((uint32_t*)&aOther2.m0)[0]) &&
+             (((uint32_t*)&aOther1.m0)[1] == ((uint32_t*)&aOther2.m0)[1]) &&
+             (((uint32_t*)&aOther1.m0)[2] == ((uint32_t*)&aOther2.m0)[2]) &&
+             (((uint32_t*)&aOther1.m0)[3] != ((uint32_t*)&aOther2.m0)[3]));
+
+  return ((((uint32_t*)&aID.m0)[0] == ((uint32_t*)&aOther1.m0)[0]) &&
+          (((uint32_t*)&aID.m0)[1] == ((uint32_t*)&aOther1.m0)[1]) &&
+          (((uint32_t*)&aID.m0)[2] == ((uint32_t*)&aOther1.m0)[2]));
+}
+
+/**
+ * Equivalency of the fourth word where the two IIDs have the same
+ * top three words but not the same low word.
+ */
+inline bool LowWordEquals(const nsID& aID, const nsID& aOther) {
+  return (((uint32_t*)&aID.m0)[3] == ((uint32_t*)&aOther.m0)[3]);
+}
+
+// Template magic to modify JS::Heap without including relevant headers, to
+// prevent excessive header dependency.
+template <typename T>
+inline void ImplCycleCollectionUnlink(JS::Heap<T>& aField) {
+  aField.setNull();
+}
+template <typename T>
+inline void ImplCycleCollectionUnlink(JS::Heap<T*>& aField) {
+  aField = nullptr;
+}
+
+#define NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBERS(...)                \
+  MOZ_ASSERT(!IsSingleZoneJSHolder());                                \
+  MOZ_FOR_EACH(NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK, (), \
+               (__VA_ARGS__))
+
+#define NS_IMPL_CYCLE_COLLECTION_WITH_JS_MEMBERS(class_, native_members_,   \
+                                                 js_members_)               \
+  NS_IMPL_CYCLE_COLLECTION_CLASS(class_)                                    \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(class_)                             \
+    using ::ImplCycleCollectionUnlink;                                      \
+    NS_IMPL_CYCLE_COLLECTION_UNLINK(                                        \
+        MOZ_FOR_EACH_EXPAND_HELPER native_members_)                         \
+    NS_IMPL_CYCLE_COLLECTION_UNLINK(MOZ_FOR_EACH_EXPAND_HELPER js_members_) \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_END                                       \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(class_)                           \
+    NS_IMPL_CYCLE_COLLECTION_TRAVERSE(                                      \
+        MOZ_FOR_EACH_EXPAND_HELPER native_members_)                         \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END                                     \
+  NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(class_)                              \
+    NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBERS(                              \
+        MOZ_FOR_EACH_EXPAND_HELPER js_members_)                             \
+  NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+#define NS_IMPL_CYCLE_COLLECTION_INHERITED_WITH_JS_MEMBERS(                 \
+    class_, _base, native_members_, js_members_)                            \
+  NS_IMPL_CYCLE_COLLECTION_CLASS(class_)                                    \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(class_, _base)            \
+    using ::ImplCycleCollectionUnlink;                                      \
+    NS_IMPL_CYCLE_COLLECTION_UNLINK(                                        \
+        MOZ_FOR_EACH_EXPAND_HELPER native_members_)                         \
+    NS_IMPL_CYCLE_COLLECTION_UNLINK(MOZ_FOR_EACH_EXPAND_HELPER js_members_) \
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_END                                       \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(class_, _base)          \
+    NS_IMPL_CYCLE_COLLECTION_TRAVERSE(                                      \
+        MOZ_FOR_EACH_EXPAND_HELPER native_members_)                         \
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END                                     \
+  NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(class_, _base)             \
+    NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBERS(                              \
+        MOZ_FOR_EACH_EXPAND_HELPER js_members_)                             \
+  NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+template <typename... Elements>
+inline void ImplCycleCollectionUnlink(std::tuple<Elements...>& aField) {
+  std::apply([](auto&&... aArgs) { (ImplCycleCollectionUnlink(aArgs), ...); },
+             aField);
+}
+template <typename... Elements>
+inline void ImplCycleCollectionTraverse(
+    nsCycleCollectionTraversalCallback& aCallback,
+    std::tuple<Elements...>& aField, const char* aName, uint32_t aFlags) {
+  aFlags |= CycleCollectionEdgeNameArrayFlag;
+  std::apply(
+      [&](auto&&... aArgs) {
+        (ImplCycleCollectionTraverse(aCallback, aArgs, aName, aFlags), ...);
+      },
+      aField);
+}
+
+#endif  // nsCycleCollectionParticipant_h__