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/* -*- 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 */
#ifndef mozilla_HoldDropJSObjects_h
#define mozilla_HoldDropJSObjects_h
#include <type_traits>
#include "nsCycleCollectionNoteChild.h"
class nsISupports;
class nsScriptObjectTracer;
namespace JS {
class Zone;
// Only HoldJSObjects and DropJSObjects should be called directly.
namespace mozilla {
namespace cyclecollector {
void HoldJSObjectsImpl(void* aHolder, nsScriptObjectTracer* aTracer,
JS::Zone* aZone = nullptr);
void HoldJSObjectsImpl(nsISupports* aHolder);
void DropJSObjectsImpl(void* aHolder);
void DropJSObjectsImpl(nsISupports* aHolder);
} // namespace cyclecollector
template <class T, bool isISupports = std::is_base_of<nsISupports, T>::value>
struct HoldDropJSObjectsHelper {
static void Hold(T* aHolder) {
static void Drop(T* aHolder) { cyclecollector::DropJSObjectsImpl(aHolder); }
template <class T>
struct HoldDropJSObjectsHelper<T, true> {
static void Hold(T* aHolder) {
static void Drop(T* aHolder) {
Classes that hold strong references to JS GC things such as `JSObjects` and
`JS::Values` (e.g. `JS::Heap<JSObject*> mFoo;`) must use these, generally by
calling `HoldJSObjects(this)` and `DropJSObjects(this)` in the ctor and dtor
For classes that are wrapper cached and hold no other strong references to JS
GC things, there's no need to call these; it will be taken care of
automatically by nsWrapperCache.
template <class T>
void HoldJSObjects(T* aHolder) {
template <class T>
void DropJSObjects(T* aHolder) {
} // namespace mozilla
#endif // mozilla_HoldDropJSObjects_h