path: root/js/src/jsobjinlines.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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 jsobjinlines_h
#define jsobjinlines_h

#include "jsobj.h"

#include "mozilla/DebugOnly.h"

#include "jsfriendapi.h"
#include "jsfun.h"

#include "builtin/MapObject.h"
#include "builtin/TypedObject.h"
#include "gc/Allocator.h"
#include "vm/ArrayObject.h"
#include "vm/DateObject.h"
#include "vm/EnvironmentObject.h"
#include "vm/NumberObject.h"
#include "vm/Probes.h"
#include "vm/StringObject.h"
#include "vm/TypedArrayCommon.h"

#include "jsatominlines.h"
#include "jscompartmentinlines.h"
#include "jsgcinlines.h"

#include "vm/ShapedObject-inl.h"
#include "vm/TypeInference-inl.h"

namespace js {

// This is needed here for ensureShape() below.
inline bool
MaybeConvertUnboxedObjectToNative(ExclusiveContext* cx, JSObject* obj)
{
    if (obj->is<UnboxedPlainObject>())
        return UnboxedPlainObject::convertToNative(cx->asJSContext(), obj);
    return true;
}

} // namespace js

inline js::Shape*
JSObject::maybeShape() const
{
    if (!is<js::ShapedObject>())
        return nullptr;

    return as<js::ShapedObject>().shape();
}

inline js::Shape*
JSObject::ensureShape(js::ExclusiveContext* cx)
{
    if (!js::MaybeConvertUnboxedObjectToNative(cx, this))
        return nullptr;
    js::Shape* shape = maybeShape();
    MOZ_ASSERT(shape);
    return shape;
}

inline void
JSObject::finalize(js::FreeOp* fop)
{
    js::probes::FinalizeObject(this);

#ifdef DEBUG
    MOZ_ASSERT(isTenured());
    if (!IsBackgroundFinalized(asTenured().getAllocKind())) {
        /* Assert we're on the main thread. */
        MOZ_ASSERT(CurrentThreadCanAccessRuntime(fop->runtime()));
    }
#endif

    const js::Class* clasp = getClass();
    js::NativeObject* nobj = nullptr;
    if (clasp->isNative())
        nobj = &as<js::NativeObject>();
    if (clasp->hasFinalize())
        clasp->doFinalize(fop, this);

    if (!nobj)
        return;

    if (nobj->hasDynamicSlots())
        fop->free_(nobj->slots_);

    if (nobj->hasDynamicElements()) {
        js::ObjectElements* elements = nobj->getElementsHeader();
        if (elements->isCopyOnWrite()) {
            if (elements->ownerObject() == this) {
                // Don't free the elements until object finalization finishes,
                // so that other objects can access these elements while they
                // are themselves finalized.
                fop->freeLater(elements);
            }
        } else {
            fop->free_(elements);
        }
    }

    nobj->sweepDictionaryListPointer();
}

MOZ_ALWAYS_INLINE void
js::NativeObject::sweepDictionaryListPointer()
{
    // For dictionary objects (which must be native), it's possible that
    // unreachable shapes may be marked whose listp points into this object.  In
    // case this happens, null out the shape's pointer so that a moving GC will
    // not try to access the dead object.
    if (shape_->listp == &shape_)
        shape_->listp = nullptr;
}

/* static */ inline bool
JSObject::setSingleton(js::ExclusiveContext* cx, js::HandleObject obj)
{
    MOZ_ASSERT_IF(cx->isJSContext(), !IsInsideNursery(obj));

    js::ObjectGroup* group = js::ObjectGroup::lazySingletonGroup(cx, obj->getClass(),
                                                                 obj->taggedProto());
    if (!group)
        return false;

    obj->group_ = group;
    return true;
}

/* static */ inline js::ObjectGroup*
JSObject::getGroup(JSContext* cx, js::HandleObject obj)
{
    MOZ_ASSERT(cx->compartment() == obj->compartment());
    if (obj->hasLazyGroup()) {
        if (cx->compartment() != obj->compartment())
            MOZ_CRASH();
        return makeLazyGroup(cx, obj);
    }
    return obj->group_;
}

inline void
JSObject::setGroup(js::ObjectGroup* group)
{
    MOZ_RELEASE_ASSERT(group);
    MOZ_ASSERT(!isSingleton());
    group_ = group;
}


/*** Standard internal methods *******************************************************************/

inline bool
js::GetPrototype(JSContext* cx, js::HandleObject obj, js::MutableHandleObject protop)
{
    if (obj->hasDynamicPrototype()) {
        MOZ_ASSERT(obj->is<js::ProxyObject>());
        return js::Proxy::getPrototype(cx, obj, protop);
    }

    protop.set(obj->taggedProto().toObjectOrNull());
    return true;
}

inline bool
js::IsExtensible(ExclusiveContext* cx, HandleObject obj, bool* extensible)
{
    if (obj->is<ProxyObject>()) {
        if (!cx->shouldBeJSContext())
            return false;
        return Proxy::isExtensible(cx->asJSContext(), obj, extensible);
    }

    *extensible = obj->nonProxyIsExtensible();
    return true;
}

inline bool
js::HasProperty(JSContext* cx, HandleObject obj, PropertyName* name, bool* found)
{
    RootedId id(cx, NameToId(name));
    return HasProperty(cx, obj, id, found);
}

inline bool
js::GetElement(JSContext* cx, HandleObject obj, HandleValue receiver, uint32_t index,
               MutableHandleValue vp)
{
    RootedId id(cx);
    if (!IndexToId(cx, index, &id))
        return false;
    return GetProperty(cx, obj, receiver, id, vp);
}

inline bool
js::GetElement(JSContext* cx, HandleObject obj, HandleObject receiver, uint32_t index,
               MutableHandleValue vp)
{
    RootedValue receiverValue(cx, ObjectValue(*receiver));
    return GetElement(cx, obj, receiverValue, index, vp);
}

inline bool
js::GetElementNoGC(JSContext* cx, JSObject* obj, const Value& receiver, uint32_t index, Value* vp)
{
    if (obj->getOpsGetProperty())
        return false;

    if (index > JSID_INT_MAX)
        return false;
    return GetPropertyNoGC(cx, obj, receiver, INT_TO_JSID(index), vp);
}

inline bool
js::GetElementNoGC(JSContext* cx, JSObject* obj, JSObject* receiver, uint32_t index, Value* vp)
{
    return GetElementNoGC(cx, obj, ObjectValue(*receiver), index, vp);
}

inline bool
js::DeleteProperty(JSContext* cx, HandleObject obj, HandleId id, ObjectOpResult& result)
{
    MarkTypePropertyNonData(cx, obj, id);
    if (DeletePropertyOp op = obj->getOpsDeleteProperty())
        return op(cx, obj, id, result);
    return NativeDeleteProperty(cx, obj.as<NativeObject>(), id, result);
}

inline bool
js::DeleteElement(JSContext* cx, HandleObject obj, uint32_t index, ObjectOpResult& result)
{
    RootedId id(cx);
    if (!IndexToId(cx, index, &id))
        return false;
    return DeleteProperty(cx, obj, id, result);
}


/* * */

inline bool
JSObject::isQualifiedVarObj() const
{
    if (is<js::DebugEnvironmentProxy>())
        return as<js::DebugEnvironmentProxy>().environment().isQualifiedVarObj();
    bool rv = hasAllFlags(js::BaseShape::QUALIFIED_VAROBJ);
    MOZ_ASSERT_IF(rv,
                  is<js::GlobalObject>() ||
                  is<js::CallObject>() ||
                  is<js::VarEnvironmentObject>() ||
                  is<js::ModuleEnvironmentObject>() ||
                  is<js::NonSyntacticVariablesObject>() ||
                  (is<js::WithEnvironmentObject>() &&
                   !as<js::WithEnvironmentObject>().isSyntactic()));
    return rv;
}

inline bool
JSObject::isUnqualifiedVarObj() const
{
    if (is<js::DebugEnvironmentProxy>())
        return as<js::DebugEnvironmentProxy>().environment().isUnqualifiedVarObj();
    return is<js::GlobalObject>() || is<js::NonSyntacticVariablesObject>();
}

namespace js {

inline bool
ClassCanHaveFixedData(const Class* clasp)
{
    // Normally, the number of fixed slots given an object is the maximum
    // permitted for its size class. For array buffers and non-shared typed
    // arrays we only use enough to cover the class reserved slots, so that
    // the remaining space in the object's allocation is available for the
    // buffer's data.
    return !clasp->isNative()
        || clasp == &js::ArrayBufferObject::class_
        || js::IsTypedArrayClass(clasp);
}

// This function is meant to be called from allocation fast paths.
//
// If we do have an allocation metadata builder, it can cause a GC, so the object
// must be rooted. The usual way to do this would be to make our callers pass a
// HandleObject, but that would require them to pay the cost of rooting the
// object unconditionally, even though collecting metadata is rare. Instead,
// SetNewObjectMetadata's contract is that the caller must use the pointer
// returned in place of the pointer passed. If a GC occurs, the returned pointer
// may be the passed pointer, relocated by GC. If no GC could occur, it's just
// passed through. We root nothing unless necessary.
static MOZ_ALWAYS_INLINE MOZ_MUST_USE JSObject*
SetNewObjectMetadata(ExclusiveContext* cxArg, JSObject* obj)
{
    MOZ_ASSERT(!cxArg->compartment()->hasObjectPendingMetadata());

    // The metadata builder is invoked for each object created on the main
    // thread, except when analysis/compilation is active, to avoid recursion.
    if (JSContext* cx = cxArg->maybeJSContext()) {
        if (MOZ_UNLIKELY((size_t)cx->compartment()->hasAllocationMetadataBuilder()) &&
            !cx->zone()->suppressAllocationMetadataBuilder)
        {
            // Don't collect metadata on objects that represent metadata.
            AutoSuppressAllocationMetadataBuilder suppressMetadata(cx);

            RootedObject rooted(cx, obj);
            cx->compartment()->setNewObjectMetadata(cx, rooted);
            return rooted;
        }
    }

    return obj;
}

} // namespace js

/* static */ inline JSObject*
JSObject::create(js::ExclusiveContext* cx, js::gc::AllocKind kind, js::gc::InitialHeap heap,
                 js::HandleShape shape, js::HandleObjectGroup group)
{
    const js::Class* clasp = group->clasp();

    MOZ_ASSERT(shape && group);
    MOZ_ASSERT(clasp == shape->getObjectClass());
    MOZ_ASSERT(clasp != &js::ArrayObject::class_);
    MOZ_ASSERT_IF(!js::ClassCanHaveFixedData(clasp),
                  js::gc::GetGCKindSlots(kind, clasp) == shape->numFixedSlots());

#ifdef DEBUG
    static const uint32_t FinalizeMask = JSCLASS_FOREGROUND_FINALIZE | JSCLASS_BACKGROUND_FINALIZE;
    uint32_t flags = clasp->flags;
    uint32_t finalizeFlags = flags & FinalizeMask;

    // Classes with a finalizer must specify whether instances will be finalized
    // on the main thread or in the background, except proxies whose behaviour
    // depends on the target object.
    if (clasp->hasFinalize() && !clasp->isProxy()) {
        MOZ_ASSERT(finalizeFlags == JSCLASS_FOREGROUND_FINALIZE ||
                   finalizeFlags == JSCLASS_BACKGROUND_FINALIZE);
        MOZ_ASSERT((finalizeFlags == JSCLASS_BACKGROUND_FINALIZE) == IsBackgroundFinalized(kind));
    } else {
        MOZ_ASSERT(finalizeFlags == 0);
    }

    MOZ_ASSERT_IF(clasp->hasFinalize(), heap == js::gc::TenuredHeap ||
                                        CanNurseryAllocateFinalizedClass(clasp) ||
                                        clasp->isProxy());
    MOZ_ASSERT_IF(group->hasUnanalyzedPreliminaryObjects(), heap == js::gc::TenuredHeap);
#endif

    MOZ_ASSERT(!cx->compartment()->hasObjectPendingMetadata());

    // Non-native classes cannot have reserved slots or private data, and the
    // objects can't have any fixed slots, for compatibility with
    // GetReservedOrProxyPrivateSlot.
    MOZ_ASSERT_IF(!clasp->isNative(), JSCLASS_RESERVED_SLOTS(clasp) == 0);
    MOZ_ASSERT_IF(!clasp->isNative(), !clasp->hasPrivate());
    MOZ_ASSERT_IF(!clasp->isNative(), shape->numFixedSlots() == 0);
    MOZ_ASSERT_IF(!clasp->isNative(), shape->slotSpan() == 0);

    size_t nDynamicSlots = 0;
    if (clasp->isNative()) {
        nDynamicSlots = js::NativeObject::dynamicSlotsCount(shape->numFixedSlots(),
                                                            shape->slotSpan(), clasp);
    } else if (clasp->isProxy()) {
        // Proxy objects overlay the |slots| field with a ProxyValueArray.
        MOZ_ASSERT(sizeof(js::detail::ProxyValueArray) % sizeof(js::HeapSlot) == 0);
        nDynamicSlots = sizeof(js::detail::ProxyValueArray) / sizeof(js::HeapSlot);
    }

    JSObject* obj = js::Allocate<JSObject>(cx, kind, nDynamicSlots, heap, clasp);
    if (!obj)
        return nullptr;

    obj->group_.init(group);

    // This function allocates normal objects and proxies and typed objects
    // (all with shapes), *and* it allocates objects without shapes (various
    // unboxed object classes).  Setting shape is naturally only valid for the
    // former class of objects.
    if (obj->is<js::ShapedObject>())
        obj->as<js::ShapedObject>().initShape(shape);

    // Note: slots are created and assigned internally by Allocate<JSObject>.
    obj->setInitialElementsMaybeNonNative(js::emptyObjectElements);

    if (clasp->hasPrivate())
        obj->as<js::NativeObject>().privateRef(shape->numFixedSlots()) = nullptr;

    if (size_t span = shape->slotSpan())
        obj->as<js::NativeObject>().initializeSlotRange(0, span);

    // JSFunction's fixed slots expect POD-style initialization.
    if (clasp->isJSFunction()) {
        MOZ_ASSERT(kind == js::gc::AllocKind::FUNCTION ||
                   kind == js::gc::AllocKind::FUNCTION_EXTENDED);
        size_t size =
            kind == js::gc::AllocKind::FUNCTION ? sizeof(JSFunction) : sizeof(js::FunctionExtended);
        memset(obj->as<JSFunction>().fixedSlots(), 0, size - sizeof(js::NativeObject));
        if (kind == js::gc::AllocKind::FUNCTION_EXTENDED) {
            // SetNewObjectMetadata may gc, which will be unhappy if flags &
            // EXTENDED doesn't match the arena's AllocKind.
            obj->as<JSFunction>().setFlags(JSFunction::EXTENDED);
        }
    }

    if (clasp->shouldDelayMetadataBuilder())
        cx->compartment()->setObjectPendingMetadata(cx, obj);
    else
        obj = SetNewObjectMetadata(cx, obj);

    js::gc::TraceCreateObject(obj);

    return obj;
}

inline void
JSObject::setInitialSlotsMaybeNonNative(js::HeapSlot* slots)
{
    static_cast<js::NativeObject*>(this)->slots_ = slots;
}

inline void
JSObject::setInitialElementsMaybeNonNative(js::HeapSlot* elements)
{
    static_cast<js::NativeObject*>(this)->elements_ = elements;
}

inline js::GlobalObject&
JSObject::global() const
{
    /*
     * The global is read-barriered so that it is kept live by access through
     * the JSCompartment. When accessed through a JSObject, however, the global
     * will be already be kept live by the black JSObject's parent pointer, so
     * does not need to be read-barriered.
     */
    return *compartment()->unsafeUnbarrieredMaybeGlobal();
}

inline js::GlobalObject*
JSObject::globalForTracing(JSTracer*) const
{
    return compartment()->unsafeUnbarrieredMaybeGlobal();
}

inline bool
JSObject::isOwnGlobal(JSTracer* trc) const
{
    return globalForTracing(trc) == this;
}

inline bool
JSObject::hasAllFlags(js::BaseShape::Flag flags) const
{
    MOZ_ASSERT(flags);
    if (js::Shape* shape = maybeShape())
        return shape->hasAllObjectFlags(flags);
    return false;
}

inline bool
JSObject::nonProxyIsExtensible() const
{
    MOZ_ASSERT(!uninlinedIsProxy());

    // [[Extensible]] for ordinary non-proxy objects is an object flag.
    return !hasAllFlags(js::BaseShape::NOT_EXTENSIBLE);
}

inline bool
JSObject::isBoundFunction() const
{
    return is<JSFunction>() && as<JSFunction>().isBoundFunction();
}

inline bool
JSObject::isDelegate() const
{
    return hasAllFlags(js::BaseShape::DELEGATE);
}

inline bool
JSObject::hasUncacheableProto() const
{
    return hasAllFlags(js::BaseShape::UNCACHEABLE_PROTO);
}

inline bool
JSObject::hadElementsAccess() const
{
    return hasAllFlags(js::BaseShape::HAD_ELEMENTS_ACCESS);
}

inline bool
JSObject::isIndexed() const
{
    return hasAllFlags(js::BaseShape::INDEXED);
}

inline bool
JSObject::staticPrototypeIsImmutable() const
{
    MOZ_ASSERT(hasStaticPrototype());
    return hasAllFlags(js::BaseShape::IMMUTABLE_PROTOTYPE);
}

inline bool
JSObject::isIteratedSingleton() const
{
    return hasAllFlags(js::BaseShape::ITERATED_SINGLETON);
}

inline bool
JSObject::isNewGroupUnknown() const
{
    return hasAllFlags(js::BaseShape::NEW_GROUP_UNKNOWN);
}

inline bool
JSObject::wasNewScriptCleared() const
{
    return hasAllFlags(js::BaseShape::NEW_SCRIPT_CLEARED);
}

namespace js {

static MOZ_ALWAYS_INLINE bool
IsFunctionObject(const js::Value& v)
{
    return v.isObject() && v.toObject().is<JSFunction>();
}

static MOZ_ALWAYS_INLINE bool
IsFunctionObject(const js::Value& v, JSFunction** fun)
{
    if (v.isObject() && v.toObject().is<JSFunction>()) {
        *fun = &v.toObject().as<JSFunction>();
        return true;
    }
    return false;
}

static MOZ_ALWAYS_INLINE bool
IsNativeFunction(const js::Value& v)
{
    JSFunction* fun;
    return IsFunctionObject(v, &fun) && fun->isNative();
}

static MOZ_ALWAYS_INLINE bool
IsNativeFunction(const js::Value& v, JSFunction** fun)
{
    return IsFunctionObject(v, fun) && (*fun)->isNative();
}

static MOZ_ALWAYS_INLINE bool
IsNativeFunction(const js::Value& v, JSNative native)
{
    JSFunction* fun;
    return IsFunctionObject(v, &fun) && fun->maybeNative() == native;
}

// Return whether looking up a method on 'obj' definitely resolves to the
// original specified native function. The method may conservatively return
// 'false' in the case of proxies or other non-native objects.
static MOZ_ALWAYS_INLINE bool
HasNativeMethodPure(JSObject* obj, PropertyName* name, JSNative native, JSContext* cx)
{
    Value v;
    if (!GetPropertyPure(cx, obj, NameToId(name), &v))
        return false;

    return IsNativeFunction(v, native);
}

// Return whether 'obj' definitely has no @@toPrimitive method.
static MOZ_ALWAYS_INLINE bool
HasNoToPrimitiveMethodPure(JSObject* obj, JSContext* cx)
{
    jsid id = SYMBOL_TO_JSID(cx->wellKnownSymbols().toPrimitive);
    JSObject* pobj;
    Shape* shape;
    if (!LookupPropertyPure(cx, obj, id, &pobj, &shape))
        return false;

    return !shape;
}

/* ES6 draft rev 28 (2014 Oct 14) 7.1.14 */
inline bool
ToPropertyKey(JSContext* cx, HandleValue argument, MutableHandleId result)
{
    // Steps 1-2.
    RootedValue key(cx, argument);
    if (!ToPrimitive(cx, JSTYPE_STRING, &key))
        return false;

    // Steps 3-4.
    return ValueToId<CanGC>(cx, key, result);
}

/*
 * Return true if this is a compiler-created internal function accessed by
 * its own object. Such a function object must not be accessible to script
 * or embedding code.
 */
inline bool
IsInternalFunctionObject(JSObject& funobj)
{
    JSFunction& fun = funobj.as<JSFunction>();
    return fun.isInterpreted() && !fun.environment();
}

/*
 * Make an object with the specified prototype. If parent is null, it will
 * default to the prototype's global if the prototype is non-null.
 */
JSObject*
NewObjectWithGivenTaggedProto(ExclusiveContext* cx, const Class* clasp, Handle<TaggedProto> proto,
                              gc::AllocKind allocKind, NewObjectKind newKind,
                              uint32_t initialShapeFlags = 0);

inline JSObject*
NewObjectWithGivenTaggedProto(ExclusiveContext* cx, const Class* clasp, Handle<TaggedProto> proto,
                              NewObjectKind newKind = GenericObject,
                              uint32_t initialShapeFlags = 0)
{
    gc::AllocKind allocKind = gc::GetGCObjectKind(clasp);
    return NewObjectWithGivenTaggedProto(cx, clasp, proto, allocKind, newKind, initialShapeFlags);
}

template <typename T>
inline T*
NewObjectWithGivenTaggedProto(ExclusiveContext* cx, Handle<TaggedProto> proto,
                              NewObjectKind newKind = GenericObject,
                              uint32_t initialShapeFlags = 0)
{
    JSObject* obj = NewObjectWithGivenTaggedProto(cx, &T::class_, proto, newKind,
                                                  initialShapeFlags);
    return obj ? &obj->as<T>() : nullptr;
}

template <typename T>
inline T*
NewObjectWithNullTaggedProto(ExclusiveContext* cx, NewObjectKind newKind = GenericObject,
                             uint32_t initialShapeFlags = 0)
{
    Rooted<TaggedProto> nullProto(cx, TaggedProto(nullptr));
    return NewObjectWithGivenTaggedProto<T>(cx, nullProto, newKind, initialShapeFlags);
}

inline JSObject*
NewObjectWithGivenProto(ExclusiveContext* cx, const Class* clasp, HandleObject proto,
                        gc::AllocKind allocKind, NewObjectKind newKind)
{
    return NewObjectWithGivenTaggedProto(cx, clasp, AsTaggedProto(proto), allocKind,
                                         newKind);
}

inline JSObject*
NewObjectWithGivenProto(ExclusiveContext* cx, const Class* clasp, HandleObject proto,
                        NewObjectKind newKind = GenericObject)
{
    return NewObjectWithGivenTaggedProto(cx, clasp, AsTaggedProto(proto), newKind);
}

template <typename T>
inline T*
NewObjectWithGivenProto(ExclusiveContext* cx, HandleObject proto,
                        NewObjectKind newKind = GenericObject)
{
    return NewObjectWithGivenTaggedProto<T>(cx, AsTaggedProto(proto), newKind);
}

template <typename T>
inline T*
NewObjectWithGivenProto(ExclusiveContext* cx, HandleObject proto,
                        gc::AllocKind allocKind, NewObjectKind newKind = GenericObject)
{
    JSObject* obj = NewObjectWithGivenTaggedProto(cx, &T::class_, AsTaggedProto(proto),
                                                  allocKind, newKind);
    return obj ? &obj->as<T>() : nullptr;
}

// Make an object with the prototype set according to the cached prototype or
// Object.prototype.
JSObject*
NewObjectWithClassProtoCommon(ExclusiveContext* cx, const Class* clasp, HandleObject proto,
                              gc::AllocKind allocKind, NewObjectKind newKind);

inline JSObject*
NewObjectWithClassProto(ExclusiveContext* cx, const Class* clasp, HandleObject proto,
                        gc::AllocKind allocKind, NewObjectKind newKind = GenericObject)
{
    return NewObjectWithClassProtoCommon(cx, clasp, proto, allocKind, newKind);
}

inline JSObject*
NewObjectWithClassProto(ExclusiveContext* cx, const Class* clasp, HandleObject proto,
                        NewObjectKind newKind = GenericObject)
{
    gc::AllocKind allocKind = gc::GetGCObjectKind(clasp);
    return NewObjectWithClassProto(cx, clasp, proto, allocKind, newKind);
}

template<class T>
inline T*
NewObjectWithClassProto(ExclusiveContext* cx, HandleObject proto = nullptr,
                        NewObjectKind newKind = GenericObject)
{
    JSObject* obj = NewObjectWithClassProto(cx, &T::class_, proto, newKind);
    return obj ? &obj->as<T>() : nullptr;
}

template <class T>
inline T*
NewObjectWithClassProto(ExclusiveContext* cx, HandleObject proto, gc::AllocKind allocKind,
                        NewObjectKind newKind = GenericObject)
{
    JSObject* obj = NewObjectWithClassProto(cx, &T::class_, proto, allocKind, newKind);
    return obj ? &obj->as<T>() : nullptr;
}

/*
 * Create a native instance of the given class with parent and proto set
 * according to the context's active global.
 */
inline JSObject*
NewBuiltinClassInstance(ExclusiveContext* cx, const Class* clasp, gc::AllocKind allocKind,
                        NewObjectKind newKind = GenericObject)
{
    return NewObjectWithClassProto(cx, clasp, nullptr, allocKind, newKind);
}

inline JSObject*
NewBuiltinClassInstance(ExclusiveContext* cx, const Class* clasp, NewObjectKind newKind = GenericObject)
{
    gc::AllocKind allocKind = gc::GetGCObjectKind(clasp);
    return NewBuiltinClassInstance(cx, clasp, allocKind, newKind);
}

template<typename T>
inline T*
NewBuiltinClassInstance(ExclusiveContext* cx, NewObjectKind newKind = GenericObject)
{
    JSObject* obj = NewBuiltinClassInstance(cx, &T::class_, newKind);
    return obj ? &obj->as<T>() : nullptr;
}

template<typename T>
inline T*
NewBuiltinClassInstance(ExclusiveContext* cx, gc::AllocKind allocKind, NewObjectKind newKind = GenericObject)
{
    JSObject* obj = NewBuiltinClassInstance(cx, &T::class_, allocKind, newKind);
    return obj ? &obj->as<T>() : nullptr;
}

// Used to optimize calls to (new Object())
bool
NewObjectScriptedCall(JSContext* cx, MutableHandleObject obj);

JSObject*
NewObjectWithGroupCommon(ExclusiveContext* cx, HandleObjectGroup group,
                         gc::AllocKind allocKind, NewObjectKind newKind);

template <typename T>
inline T*
NewObjectWithGroup(ExclusiveContext* cx, HandleObjectGroup group,
                   gc::AllocKind allocKind, NewObjectKind newKind = GenericObject)
{
    JSObject* obj = NewObjectWithGroupCommon(cx, group, allocKind, newKind);
    return obj ? &obj->as<T>() : nullptr;
}

template <typename T>
inline T*
NewObjectWithGroup(ExclusiveContext* cx, HandleObjectGroup group,
                   NewObjectKind newKind = GenericObject)
{
    gc::AllocKind allocKind = gc::GetGCObjectKind(group->clasp());
    return NewObjectWithGroup<T>(cx, group, allocKind, newKind);
}

/*
 * As for gc::GetGCObjectKind, where numElements is a guess at the final size of
 * the object, zero if the final size is unknown. This should only be used for
 * objects that do not require any fixed slots.
 */
static inline gc::AllocKind
GuessObjectGCKind(size_t numElements)
{
    if (numElements)
        return gc::GetGCObjectKind(numElements);
    return gc::AllocKind::OBJECT4;
}

static inline gc::AllocKind
GuessArrayGCKind(size_t numElements)
{
    if (numElements)
        return gc::GetGCArrayKind(numElements);
    return gc::AllocKind::OBJECT8;
}

// Returns ESClass::Other if the value isn't an object, or if the object
// isn't of one of the enumerated classes.  Otherwise returns the appropriate
// class.
inline bool
GetClassOfValue(JSContext* cx, HandleValue v, ESClass* cls)
{
    if (!v.isObject()) {
        *cls = ESClass::Other;
        return true;
    }

    RootedObject obj(cx, &v.toObject());
    return GetBuiltinClass(cx, obj, cls);
}

extern NativeObject*
InitClass(JSContext* cx, HandleObject obj, HandleObject parent_proto,
          const Class* clasp, JSNative constructor, unsigned nargs,
          const JSPropertySpec* ps, const JSFunctionSpec* fs,
          const JSPropertySpec* static_ps, const JSFunctionSpec* static_fs,
          NativeObject** ctorp = nullptr,
          gc::AllocKind ctorKind = gc::AllocKind::FUNCTION);

} /* namespace js */

#endif /* jsobjinlines_h */