Source code

Revision control

Copy as Markdown

Other Tools

/* -*- 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 js_SweepingAPI_h
#define js_SweepingAPI_h
#include "mozilla/LinkedList.h"
#include "mozilla/Maybe.h"
#include "jstypes.h"
#include "js/GCAnnotations.h"
#include "js/GCPolicyAPI.h"
#include "js/RootingAPI.h"
namespace js {
namespace gc {
class StoreBuffer;
JS_PUBLIC_API void LockStoreBuffer(StoreBuffer* sb);
JS_PUBLIC_API void UnlockStoreBuffer(StoreBuffer* sb);
class AutoLockStoreBuffer {
StoreBuffer* sb;
explicit AutoLockStoreBuffer(StoreBuffer* sb) : sb(sb) {
~AutoLockStoreBuffer() { UnlockStoreBuffer(sb); }
} // namespace gc
} // namespace js
namespace JS {
namespace detail {
class WeakCacheBase;
} // namespace detail
namespace shadow {
JS_PUBLIC_API void RegisterWeakCache(JS::Zone* zone,
JS::detail::WeakCacheBase* cachep);
JS_PUBLIC_API void RegisterWeakCache(JSRuntime* rt,
JS::detail::WeakCacheBase* cachep);
} // namespace shadow
namespace detail {
class WeakCacheBase : public mozilla::LinkedListElement<WeakCacheBase> {
WeakCacheBase() = delete;
explicit WeakCacheBase(const WeakCacheBase&) = delete;
explicit WeakCacheBase(Zone* zone) { shadow::RegisterWeakCache(zone, this); }
explicit WeakCacheBase(JSRuntime* rt) { shadow::RegisterWeakCache(rt, this); }
WeakCacheBase(WeakCacheBase&& other) = default;
virtual ~WeakCacheBase() = default;
virtual size_t traceWeak(JSTracer* trc, js::gc::StoreBuffer* sbToLock) = 0;
// Sweeping will be skipped if the cache is empty already.
virtual bool empty() = 0;
// Enable/disable read barrier during incremental sweeping and set the tracer
// to use.
virtual bool setIncrementalBarrierTracer(JSTracer* trc) {
// Derived classes do not support incremental barriers by default.
return false;
virtual bool needsIncrementalBarrier() const {
// Derived classes do not support incremental barriers by default.
return false;
} // namespace detail
// A WeakCache stores the given Sweepable container and links itself into a
// list of such caches that are swept during each GC. A WeakCache can be
// specific to a zone, or across a whole runtime, depending on which
// constructor is used.
template <typename T>
class WeakCache : protected detail::WeakCacheBase,
public js::MutableWrappedPtrOperations<T, WeakCache<T>> {
T cache;
using Type = T;
template <typename... Args>
explicit WeakCache(Zone* zone, Args&&... args)
: WeakCacheBase(zone), cache(std::forward<Args>(args)...) {}
template <typename... Args>
explicit WeakCache(JSRuntime* rt, Args&&... args)
: WeakCacheBase(rt), cache(std::forward<Args>(args)...) {}
const T& get() const { return cache; }
T& get() { return cache; }
size_t traceWeak(JSTracer* trc, js::gc::StoreBuffer* sbToLock) override {
// Take the store buffer lock in case sweeping triggers any generational
// post barriers. This is not always required and WeakCache specializations
// may delay or skip taking the lock as appropriate.
mozilla::Maybe<js::gc::AutoLockStoreBuffer> lock;
if (sbToLock) {
GCPolicy<T>::traceWeak(trc, &cache);
return 0;
bool empty() override { return cache.empty(); }
} // namespace JS
#endif // js_SweepingAPI_h