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ProxyObject.cpp
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ProxyObject.cpp
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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 http://mozilla.org/MPL/2.0/. */
#include "vm/ProxyObject.h"
#include "gc/Allocator.h"
#include "gc/GCTrace.h"
#include "proxy/DeadObjectProxy.h"
#include "vm/Realm.h"
#include "gc/ObjectKind-inl.h"
#include "vm/JSObject-inl.h"
#include "vm/TypeInference-inl.h"
using namespace js;
static gc::AllocKind GetProxyGCObjectKind(const JSClass* clasp,
const BaseProxyHandler* handler,
const Value& priv) {
MOZ_ASSERT(clasp->isProxy());
uint32_t nreserved = JSCLASS_RESERVED_SLOTS(clasp);
// For now assert each Proxy Class has at least 1 reserved slot. This is
// not a hard requirement, but helps catch Classes that need an explicit
// JSCLASS_HAS_RESERVED_SLOTS since bug 1360523.
MOZ_ASSERT(nreserved > 0);
MOZ_ASSERT(
js::detail::ProxyValueArray::sizeOf(nreserved) % sizeof(Value) == 0,
"ProxyValueArray must be a multiple of Value");
uint32_t nslots =
js::detail::ProxyValueArray::sizeOf(nreserved) / sizeof(Value);
MOZ_ASSERT(nslots <= NativeObject::MAX_FIXED_SLOTS);
gc::AllocKind kind = gc::GetGCObjectKind(nslots);
if (handler->finalizeInBackground(priv)) {
kind = ForegroundToBackgroundAllocKind(kind);
}
return kind;
}
/* static */
ProxyObject* ProxyObject::New(JSContext* cx, const BaseProxyHandler* handler,
HandleValue priv, TaggedProto proto_,
const ProxyOptions& options) {
Rooted<TaggedProto> proto(cx, proto_);
const JSClass* clasp = options.clasp();
#ifdef DEBUG
MOZ_ASSERT(isValidProxyClass(clasp));
MOZ_ASSERT(clasp->shouldDelayMetadataBuilder());
MOZ_ASSERT_IF(proto.isObject(),
cx->compartment() == proto.toObject()->compartment());
MOZ_ASSERT(clasp->hasFinalize());
if (priv.isGCThing()) {
JS::AssertCellIsNotGray(priv.toGCThing());
}
#endif
/*
* Eagerly mark properties unknown for proxies, so we don't try to track
* their properties and so that we don't need to walk the compartment if
* their prototype changes later. But don't do this for DOM proxies,
* because we want to be able to keep track of them in typesets in useful
* ways.
*/
if (proto.isObject() && !options.singleton() && !clasp->isDOMClass()) {
ObjectGroupRealm& realm = ObjectGroupRealm::getForNewObject(cx);
RootedObject protoObj(cx, proto.toObject());
if (!JSObject::setNewGroupUnknown(cx, realm, clasp, protoObj)) {
return nullptr;
}
}
// Ensure that the wrapper has the same lifetime assumptions as the
// wrappee. Prefer to allocate in the nursery, when possible.
NewObjectKind newKind = NurseryAllocatedProxy;
if (options.singleton()) {
MOZ_ASSERT(priv.isNull() ||
(priv.isGCThing() && priv.toGCThing()->isTenured()));
newKind = SingletonObject;
} else if ((priv.isGCThing() && priv.toGCThing()->isTenured()) ||
!handler->canNurseryAllocate()) {
newKind = TenuredObject;
}
gc::AllocKind allocKind = GetProxyGCObjectKind(clasp, handler, priv);
AutoSetNewObjectMetadata metadata(cx);
// Note: this will initialize the object's |data| to strange values, but we
// will immediately overwrite those below.
ProxyObject* proxy;
JS_TRY_VAR_OR_RETURN_NULL(cx, proxy,
create(cx, clasp, proto, allocKind, newKind));
proxy->setInlineValueArray();
detail::ProxyValueArray* values = detail::GetProxyDataLayout(proxy)->values();
values->init(proxy->numReservedSlots());
proxy->data.handler = handler;
if (IsCrossCompartmentWrapper(proxy)) {
MOZ_ASSERT(cx->global() == &cx->compartment()->globalForNewCCW());
proxy->setCrossCompartmentPrivate(priv);
} else {
proxy->setSameCompartmentPrivate(priv);
}
if (newKind == SingletonObject) {
Rooted<ProxyObject*> rootedProxy(cx, proxy);
if (!JSObject::setSingleton(cx, rootedProxy)) {
return nullptr;
}
return rootedProxy;
}
/* Don't track types of properties of non-DOM and non-singleton proxies. */
if (!clasp->isDOMClass()) {
MarkObjectGroupUnknownProperties(cx, proxy->group());
}
return proxy;
}
gc::AllocKind ProxyObject::allocKindForTenure() const {
MOZ_ASSERT(usingInlineValueArray());
Value priv = private_();
return GetProxyGCObjectKind(getClass(), data.handler, priv);
}
void ProxyObject::setCrossCompartmentPrivate(const Value& priv) {
setPrivate(priv);
}
void ProxyObject::setSameCompartmentPrivate(const Value& priv) {
MOZ_ASSERT(IsObjectValueInCompartment(priv, compartment()));
setPrivate(priv);
}
inline void ProxyObject::setPrivate(const Value& priv) {
MOZ_ASSERT_IF(IsMarkedBlack(this) && priv.isGCThing(),
!JS::GCThingIsMarkedGray(JS::GCCellPtr(priv)));
*slotOfPrivate() = priv;
}
void ProxyObject::nuke() {
// Clear the target reference and replaced it with a value that encodes
// various information about the original target.
setSameCompartmentPrivate(DeadProxyTargetValue(this));
// Update the handler to make this a DeadObjectProxy.
setHandler(&DeadObjectProxy::singleton);
// The proxy's reserved slots are not cleared and will continue to be
// traced. This avoids the possibility of triggering write barriers while
// nuking proxies in dead compartments which could otherwise cause those
// compartments to be kept alive. Note that these are slots cannot hold
// cross compartment pointers, so this cannot cause the target compartment
// to leak.
}
/* static */ JS::Result<ProxyObject*, JS::OOM&> ProxyObject::create(
JSContext* cx, const JSClass* clasp, Handle<TaggedProto> proto,
gc::AllocKind allocKind, NewObjectKind newKind) {
MOZ_ASSERT(clasp->isProxy());
Realm* realm = cx->realm();
RootedObjectGroup group(cx);
RootedShape shape(cx);
// Try to look up the group and shape in the NewProxyCache.
if (!realm->newProxyCache.lookup(clasp, proto, group.address(),
shape.address())) {
group = ObjectGroup::defaultNewGroup(cx, clasp, proto, nullptr);
if (!group) {
return cx->alreadyReportedOOM();
}
shape = EmptyShape::getInitialShape(cx, clasp, proto, /* nfixed = */ 0);
if (!shape) {
return cx->alreadyReportedOOM();
}
realm->newProxyCache.add(group, shape);
}
MOZ_ASSERT(group->realm() == realm);
MOZ_ASSERT(shape->zone() == cx->zone());
MOZ_ASSERT(!IsAboutToBeFinalizedUnbarriered(group.address()));
MOZ_ASSERT(!IsAboutToBeFinalizedUnbarriered(shape.address()));
gc::InitialHeap heap = GetInitialHeap(newKind, group);
debugCheckNewObject(group, shape, allocKind, heap);
JSObject* obj =
js::AllocateObject(cx, allocKind, /* nDynamicSlots = */ 0, heap, clasp);
if (!obj) {
return cx->alreadyReportedOOM();
}
ProxyObject* pobj = static_cast<ProxyObject*>(obj);
pobj->initGroup(group);
pobj->initShape(shape);
MOZ_ASSERT(clasp->shouldDelayMetadataBuilder());
cx->realm()->setObjectPendingMetadata(cx, pobj);
js::gc::gcTracer.traceCreateObject(pobj);
return pobj;
}
JS_FRIEND_API void js::detail::SetValueInProxy(Value* slot,
const Value& value) {
// Slots in proxies are not GCPtrValues, so do a cast whenever assigning
// values to them which might trigger a barrier.
*reinterpret_cast<GCPtrValue*>(slot) = value;
}