js/src/jsobj.cpp
author Jason Orendorff <jorendorff@mozilla.com>
Thu, 28 Aug 2014 15:43:57 -0500
changeset 225813 043c91e3aaeb6f92ba72395e6c70b715a6be4603
parent 225511 75ebb70f8b3804639952219999574f8a0e4aafaf
child 225827 15bafc2978d8fb4487d81de9f65bcb621064984c
permissions -rw-r--r--
Bug 1042567 - Reflect JSPropertyOp properties more consistently as data properties. r=efaust, a=lmandel

/* -*- 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/. */

/*
 * JS object implementation.
 */

#include "jsobjinlines.h"

#include "mozilla/ArrayUtils.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/MathAlgorithms.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/TemplateLib.h"

#include <string.h>

#include "jsapi.h"
#include "jsarray.h"
#include "jsatom.h"
#include "jscntxt.h"
#include "jsfriendapi.h"
#include "jsfun.h"
#include "jsgc.h"
#include "jsiter.h"
#include "jsnum.h"
#include "jsopcode.h"
#include "jsprf.h"
#include "jsproxy.h"
#include "jsscript.h"
#include "jsstr.h"
#include "jstypes.h"
#include "jsutil.h"
#include "jswatchpoint.h"
#include "jswrapper.h"

#include "asmjs/AsmJSModule.h"
#include "builtin/Eval.h"
#include "builtin/Object.h"
#include "builtin/SymbolObject.h"
#include "frontend/BytecodeCompiler.h"
#include "gc/Marking.h"
#include "jit/BaselineJIT.h"
#include "js/MemoryMetrics.h"
#include "js/OldDebugAPI.h"
#include "vm/ArgumentsObject.h"
#include "vm/Interpreter.h"
#include "vm/ProxyObject.h"
#include "vm/RegExpStaticsObject.h"
#include "vm/Shape.h"

#include "jsatominlines.h"
#include "jsboolinlines.h"
#include "jscntxtinlines.h"
#include "jscompartmentinlines.h"

#include "vm/ArrayObject-inl.h"
#include "vm/BooleanObject-inl.h"
#include "vm/NumberObject-inl.h"
#include "vm/ObjectImpl-inl.h"
#include "vm/Runtime-inl.h"
#include "vm/Shape-inl.h"
#include "vm/StringObject-inl.h"

using namespace js;
using namespace js::gc;
using namespace js::types;

using mozilla::Maybe;
using mozilla::RoundUpPow2;

JS_STATIC_ASSERT(int32_t((JSObject::NELEMENTS_LIMIT - 1) * sizeof(Value)) == int64_t((JSObject::NELEMENTS_LIMIT - 1) * sizeof(Value)));

static JSObject *
CreateObjectConstructor(JSContext *cx, JSProtoKey key)
{
    Rooted<GlobalObject*> self(cx, cx->global());
    if (!GlobalObject::ensureConstructor(cx, self, JSProto_Function))
        return nullptr;

    RootedObject functionProto(cx, &self->getPrototype(JSProto_Function).toObject());

    /* Create the Object function now that we have a [[Prototype]] for it. */
    RootedObject ctor(cx, NewObjectWithGivenProto(cx, &JSFunction::class_, functionProto,
                                                  self, SingletonObject));
    if (!ctor)
        return nullptr;
    return NewFunction(cx, ctor, obj_construct, 1, JSFunction::NATIVE_CTOR, self,
                       HandlePropertyName(cx->names().Object));
}

static JSObject *
CreateObjectPrototype(JSContext *cx, JSProtoKey key)
{
    Rooted<GlobalObject*> self(cx, cx->global());

    JS_ASSERT(!cx->runtime()->isAtomsCompartment(cx->compartment()));
    JS_ASSERT(self->isNative());

    /*
     * Create |Object.prototype| first, mirroring CreateBlankProto but for the
     * prototype of the created object.
     */
    RootedObject objectProto(cx, NewObjectWithGivenProto(cx, &JSObject::class_, nullptr,
                                                         self, SingletonObject));
    if (!objectProto)
        return nullptr;

    /*
     * The default 'new' type of Object.prototype is required by type inference
     * to have unknown properties, to simplify handling of e.g. heterogenous
     * objects in JSON and script literals.
     */
    if (!JSObject::setNewTypeUnknown(cx, &JSObject::class_, objectProto))
        return nullptr;

    return objectProto;
}

static bool
FinishObjectClassInit(JSContext *cx, JS::HandleObject ctor, JS::HandleObject proto)
{
    Rooted<GlobalObject*> self(cx, cx->global());

    /* ES5 15.1.2.1. */
    RootedId evalId(cx, NameToId(cx->names().eval));
    JSObject *evalobj = DefineFunction(cx, self, evalId, IndirectEval, 1, JSFUN_STUB_GSOPS);
    if (!evalobj)
        return false;
    self->setOriginalEval(evalobj);

    RootedObject intrinsicsHolder(cx);
    if (cx->runtime()->isSelfHostingGlobal(self)) {
        intrinsicsHolder = self;
    } else {
        intrinsicsHolder = NewObjectWithGivenProto(cx, &JSObject::class_, proto, self,
                                                   TenuredObject);
        if (!intrinsicsHolder)
            return false;
    }
    self->setIntrinsicsHolder(intrinsicsHolder);
    /* Define a property 'global' with the current global as its value. */
    RootedValue global(cx, ObjectValue(*self));
    if (!JSObject::defineProperty(cx, intrinsicsHolder, cx->names().global,
                                  global, JS_PropertyStub, JS_StrictPropertyStub,
                                  JSPROP_PERMANENT | JSPROP_READONLY))
    {
        return false;
    }

    /*
     * Define self-hosted functions after setting the intrinsics holder
     * (which is needed to define self-hosted functions)
     */
    if (!JS_DefineFunctions(cx, ctor, object_static_selfhosted_methods))
        return false;

    /*
     * The global object should have |Object.prototype| as its [[Prototype]].
     * Eventually we'd like to have standard classes be there from the start,
     * and thus we would know we were always setting what had previously been a
     * null [[Prototype]], but right now some code assumes it can set the
     * [[Prototype]] before standard classes have been initialized.  For now,
     * only set the [[Prototype]] if it hasn't already been set.
     */
    Rooted<TaggedProto> tagged(cx, TaggedProto(proto));
    if (self->shouldSplicePrototype(cx) && !self->splicePrototype(cx, self->getClass(), tagged))
        return false;
    return true;
}


const Class JSObject::class_ = {
    js_Object_str,
    JSCLASS_HAS_CACHED_PROTO(JSProto_Object),
    JS_PropertyStub,         /* addProperty */
    JS_DeletePropertyStub,   /* delProperty */
    JS_PropertyStub,         /* getProperty */
    JS_StrictPropertyStub,   /* setProperty */
    JS_EnumerateStub,
    JS_ResolveStub,
    JS_ConvertStub,
    nullptr,                 /* finalize */
    nullptr,                 /* call */
    nullptr,                 /* hasInstance */
    nullptr,                 /* construct */
    nullptr,                 /* trace */
    {
        CreateObjectConstructor,
        CreateObjectPrototype,
        object_static_methods,
        object_methods,
        object_properties,
        FinishObjectClassInit
    }
};

const Class* const js::ObjectClassPtr = &JSObject::class_;

JS_FRIEND_API(JSObject *)
JS_ObjectToInnerObject(JSContext *cx, HandleObject obj)
{
    if (!obj) {
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_INACTIVE);
        return nullptr;
    }
    return GetInnerObject(obj);
}

JS_FRIEND_API(JSObject *)
JS_ObjectToOuterObject(JSContext *cx, HandleObject obj)
{
    assertSameCompartment(cx, obj);
    return GetOuterObject(cx, obj);
}

JSObject *
js::NonNullObject(JSContext *cx, const Value &v)
{
    if (v.isPrimitive()) {
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_NOT_NONNULL_OBJECT);
        return nullptr;
    }
    return &v.toObject();
}

const char *
js::InformalValueTypeName(const Value &v)
{
    if (v.isObject())
        return v.toObject().getClass()->name;
    if (v.isString())
        return "string";
    if (v.isSymbol())
        return "symbol";
    if (v.isNumber())
        return "number";
    if (v.isBoolean())
        return "boolean";
    if (v.isNull())
        return "null";
    if (v.isUndefined())
        return "undefined";
    return "value";
}

bool
js::NewPropertyDescriptorObject(JSContext *cx, Handle<PropertyDescriptor> desc,
                                MutableHandleValue vp)
{
    if (!desc.object()) {
        vp.setUndefined();
        return true;
    }

    Rooted<PropDesc> d(cx);

    d.initFromPropertyDescriptor(desc);
    RootedObject descObj(cx);
    if (!d.makeObject(cx, &descObj))
        return false;
    vp.setObject(*descObj);
    return true;
}

void
PropDesc::initFromPropertyDescriptor(Handle<PropertyDescriptor> desc)
{
    MOZ_ASSERT(isUndefined());

    if (!desc.object())
        return;

    isUndefined_ = false;
    attrs = uint8_t(desc.attributes());
    JS_ASSERT_IF(attrs & JSPROP_READONLY, !(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
    if (desc.hasGetterOrSetterObject()) {
        hasGet_ = true;
        get_ = desc.hasGetterObject() && desc.getterObject()
               ? ObjectValue(*desc.getterObject())
               : UndefinedValue();
        hasSet_ = true;
        set_ = desc.hasSetterObject() && desc.setterObject()
               ? ObjectValue(*desc.setterObject())
               : UndefinedValue();
        hasValue_ = false;
        value_.setUndefined();
        hasWritable_ = false;
    } else {
        hasGet_ = false;
        get_.setUndefined();
        hasSet_ = false;
        set_.setUndefined();
        hasValue_ = !(desc.attributes() & JSPROP_IGNORE_VALUE);
        value_ = hasValue_ ? desc.value() : UndefinedValue();
        hasWritable_ = !(desc.attributes() & JSPROP_IGNORE_READONLY);
    }
    hasEnumerable_ = !(desc.attributes() & JSPROP_IGNORE_ENUMERATE);
    hasConfigurable_ = !(desc.attributes() & JSPROP_IGNORE_PERMANENT);
}

void
PropDesc::populatePropertyDescriptor(HandleObject obj, MutableHandle<PropertyDescriptor> desc) const
{
    if (isUndefined()) {
        desc.object().set(nullptr);
        return;
    }

    desc.value().set(hasValue() ? value() : UndefinedValue());
    desc.setGetter(getter());
    desc.setSetter(setter());

    // Make sure we honor the "has" notions in some way.
    unsigned attrs = attributes();
    if (!hasEnumerable())
        attrs |= JSPROP_IGNORE_ENUMERATE;
    if (!hasWritable())
        attrs |= JSPROP_IGNORE_READONLY;
    if (!hasConfigurable())
        attrs |= JSPROP_IGNORE_PERMANENT;
    if (!hasValue())
        attrs |= JSPROP_IGNORE_VALUE;
    desc.setAttributes(attrs);

    desc.object().set(obj);
}

bool
PropDesc::makeObject(JSContext *cx, MutableHandleObject obj)
{
    MOZ_ASSERT(!isUndefined());

    obj.set(NewBuiltinClassInstance(cx, &JSObject::class_));
    if (!obj)
        return false;

    const JSAtomState &names = cx->names();
    RootedValue configurableVal(cx, BooleanValue((attrs & JSPROP_PERMANENT) == 0));
    RootedValue enumerableVal(cx, BooleanValue((attrs & JSPROP_ENUMERATE) != 0));
    RootedValue writableVal(cx, BooleanValue((attrs & JSPROP_READONLY) == 0));
    if ((hasConfigurable() &&
         !JSObject::defineProperty(cx, obj, names.configurable, configurableVal)) ||
        (hasEnumerable() &&
         !JSObject::defineProperty(cx, obj, names.enumerable, enumerableVal)) ||
        (hasGet() &&
         !JSObject::defineProperty(cx, obj, names.get, getterValue())) ||
        (hasSet() &&
         !JSObject::defineProperty(cx, obj, names.set, setterValue())) ||
        (hasValue() &&
         !JSObject::defineProperty(cx, obj, names.value, value())) ||
        (hasWritable() &&
         !JSObject::defineProperty(cx, obj, names.writable, writableVal)))
    {
        return false;
    }

    return true;
}

bool
js::GetOwnPropertyDescriptor(JSContext *cx, HandleObject obj, HandleId id,
                             MutableHandle<PropertyDescriptor> desc)
{
    if (obj->is<ProxyObject>())
        return Proxy::getOwnPropertyDescriptor(cx, obj, id, desc);

    RootedObject pobj(cx);
    RootedShape shape(cx);
    if (!HasOwnProperty<CanGC>(cx, obj->getOps()->lookupGeneric, obj, id, &pobj, &shape))
        return false;
    if (!shape) {
        desc.object().set(nullptr);
        return true;
    }

    bool doGet = true;
    if (pobj->isNative()) {
        desc.setAttributes(GetShapeAttributes(pobj, shape));
        if (desc.hasGetterOrSetterObject()) {
            MOZ_ASSERT(desc.isShared());
            doGet = false;
            if (desc.hasGetterObject())
                desc.setGetterObject(shape->getterObject());
            if (desc.hasSetterObject())
                desc.setSetterObject(shape->setterObject());
        } else {
            // This is either a straight-up data property or (rarely) a
            // property with a JSPropertyOp getter/setter. The latter must be
            // reported to the caller as a plain data property, so don't
            // populate desc.getter/setter, and mask away the SHARED bit.
            desc.attributesRef() &= ~JSPROP_SHARED;
        }
    } else {
        if (!JSObject::getGenericAttributes(cx, pobj, id, &desc.attributesRef()))
            return false;
    }

    RootedValue value(cx);
    if (doGet && !JSObject::getGeneric(cx, obj, obj, id, &value))
        return false;

    desc.value().set(value);
    desc.object().set(obj);
    return true;
}

bool
js::GetOwnPropertyDescriptor(JSContext *cx, HandleObject obj, HandleId id, MutableHandleValue vp)
{
    Rooted<PropertyDescriptor> desc(cx);
    return GetOwnPropertyDescriptor(cx, obj, id, &desc) &&
           NewPropertyDescriptorObject(cx, desc, vp);
}

bool
js::GetFirstArgumentAsObject(JSContext *cx, const CallArgs &args, const char *method,
                             MutableHandleObject objp)
{
    if (args.length() == 0) {
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
                             method, "0", "s");
        return false;
    }

    HandleValue v = args[0];
    if (!v.isObject()) {
        char *bytes = DecompileValueGenerator(cx, JSDVG_SEARCH_STACK, v, NullPtr());
        if (!bytes)
            return false;
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
                             bytes, "not an object");
        js_free(bytes);
        return false;
    }

    objp.set(&v.toObject());
    return true;
}

static bool
HasProperty(JSContext *cx, HandleObject obj, HandleId id, MutableHandleValue vp, bool *foundp)
{
    if (!JSObject::hasProperty(cx, obj, id, foundp))
        return false;
    if (!*foundp) {
        vp.setUndefined();
        return true;
    }

    /*
     * We must go through the method read barrier in case id is 'get' or 'set'.
     * There is no obvious way to defer cloning a joined function object whose
     * identity will be used by DefinePropertyOnObject, e.g., or reflected via
     * js::GetOwnPropertyDescriptor, as the getter or setter callable object.
     */
    return !!JSObject::getGeneric(cx, obj, obj, id, vp);
}

bool
PropDesc::initialize(JSContext *cx, const Value &origval, bool checkAccessors)
{
    MOZ_ASSERT(isUndefined());

    RootedValue v(cx, origval);

    /* 8.10.5 step 1 */
    if (v.isPrimitive()) {
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_NOT_NONNULL_OBJECT);
        return false;
    }
    RootedObject desc(cx, &v.toObject());

    isUndefined_ = false;

    /*
     * Start with the proper defaults.  XXX shouldn't be necessary when we get
     * rid of PropDesc::attributes()
     */
    attrs = JSPROP_PERMANENT | JSPROP_READONLY;

    bool found = false;
    RootedId id(cx);

    /* 8.10.5 step 3 */
    id = NameToId(cx->names().enumerable);
    if (!HasProperty(cx, desc, id, &v, &found))
        return false;
    if (found) {
        hasEnumerable_ = true;
        if (ToBoolean(v))
            attrs |= JSPROP_ENUMERATE;
    }

    /* 8.10.5 step 4 */
    id = NameToId(cx->names().configurable);
    if (!HasProperty(cx, desc, id, &v, &found))
        return false;
    if (found) {
        hasConfigurable_ = true;
        if (ToBoolean(v))
            attrs &= ~JSPROP_PERMANENT;
    }

    /* 8.10.5 step 5 */
    id = NameToId(cx->names().value);
    if (!HasProperty(cx, desc, id, &v, &found))
        return false;
    if (found) {
        hasValue_ = true;
        value_ = v;
    }

    /* 8.10.6 step 6 */
    id = NameToId(cx->names().writable);
    if (!HasProperty(cx, desc, id, &v, &found))
        return false;
    if (found) {
        hasWritable_ = true;
        if (ToBoolean(v))
            attrs &= ~JSPROP_READONLY;
    }

    /* 8.10.7 step 7 */
    id = NameToId(cx->names().get);
    if (!HasProperty(cx, desc, id, &v, &found))
        return false;
    if (found) {
        hasGet_ = true;
        get_ = v;
        attrs |= JSPROP_GETTER | JSPROP_SHARED;
        attrs &= ~JSPROP_READONLY;
        if (checkAccessors && !checkGetter(cx))
            return false;
    }

    /* 8.10.7 step 8 */
    id = NameToId(cx->names().set);
    if (!HasProperty(cx, desc, id, &v, &found))
        return false;
    if (found) {
        hasSet_ = true;
        set_ = v;
        attrs |= JSPROP_SETTER | JSPROP_SHARED;
        attrs &= ~JSPROP_READONLY;
        if (checkAccessors && !checkSetter(cx))
            return false;
    }

    /* 8.10.7 step 9 */
    if ((hasGet() || hasSet()) && (hasValue() || hasWritable())) {
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_INVALID_DESCRIPTOR);
        return false;
    }

    JS_ASSERT_IF(attrs & JSPROP_READONLY, !(attrs & (JSPROP_GETTER | JSPROP_SETTER)));

    return true;
}

void
PropDesc::complete()
{
    MOZ_ASSERT(!isUndefined());

    if (isGenericDescriptor() || isDataDescriptor()) {
        if (!hasValue_) {
            hasValue_ = true;
            value_.setUndefined();
        }
        if (!hasWritable_) {
            hasWritable_ = true;
            attrs |= JSPROP_READONLY;
        }
    } else {
        if (!hasGet_) {
            hasGet_ = true;
            get_.setUndefined();
        }
        if (!hasSet_) {
            hasSet_ = true;
            set_.setUndefined();
        }
    }
    if (!hasEnumerable_) {
        hasEnumerable_ = true;
        attrs &= ~JSPROP_ENUMERATE;
    }
    if (!hasConfigurable_) {
        hasConfigurable_ = true;
        attrs |= JSPROP_PERMANENT;
    }
}

bool
js::Throw(JSContext *cx, jsid id, unsigned errorNumber)
{
    JS_ASSERT(js_ErrorFormatString[errorNumber].argCount == 1);

    JSString *idstr = IdToString(cx, id);
    if (!idstr)
       return false;
    JSAutoByteString bytes(cx, idstr);
    if (!bytes)
        return false;
    JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, errorNumber, bytes.ptr());
    return false;
}

bool
js::Throw(JSContext *cx, JSObject *obj, unsigned errorNumber)
{
    if (js_ErrorFormatString[errorNumber].argCount == 1) {
        RootedValue val(cx, ObjectValue(*obj));
        js_ReportValueErrorFlags(cx, JSREPORT_ERROR, errorNumber,
                                 JSDVG_IGNORE_STACK, val, NullPtr(),
                                 nullptr, nullptr);
    } else {
        JS_ASSERT(js_ErrorFormatString[errorNumber].argCount == 0);
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, errorNumber);
    }
    return false;
}

static bool
Reject(JSContext *cx, unsigned errorNumber, bool throwError, jsid id, bool *rval)
{
    if (throwError)
        return Throw(cx, id, errorNumber);

    *rval = false;
    return true;
}

static bool
Reject(JSContext *cx, JSObject *obj, unsigned errorNumber, bool throwError, bool *rval)
{
    if (throwError)
        return Throw(cx, obj, errorNumber);

    *rval = false;
    return true;
}

static bool
Reject(JSContext *cx, HandleId id, unsigned errorNumber, bool throwError, bool *rval)
{
    if (throwError)
        return Throw(cx, id, errorNumber);

    *rval = false;
    return true;
}

static unsigned
ApplyAttributes(unsigned attrs, bool enumerable, bool writable, bool configurable)
{
    /*
     * Respect the fact that some callers may want to preserve existing attributes as much as
     * possible, or install defaults otherwise.
     */
    if (attrs & JSPROP_IGNORE_ENUMERATE) {
        attrs &= ~JSPROP_IGNORE_ENUMERATE;
        if (enumerable)
            attrs |= JSPROP_ENUMERATE;
        else
            attrs &= ~JSPROP_ENUMERATE;
    }
    if (attrs & JSPROP_IGNORE_READONLY) {
        attrs &= ~JSPROP_IGNORE_READONLY;
        // Only update the writability if it's relevant
        if (!(attrs & (JSPROP_GETTER | JSPROP_SETTER))) {
            if (!writable)
                attrs |= JSPROP_READONLY;
            else
                attrs &= ~JSPROP_READONLY;
        }
    }
    if (attrs & JSPROP_IGNORE_PERMANENT) {
        attrs &= ~JSPROP_IGNORE_PERMANENT;
        if (!configurable)
            attrs |= JSPROP_PERMANENT;
        else
            attrs &= ~JSPROP_PERMANENT;
    }
    return attrs;
}

static unsigned
ApplyOrDefaultAttributes(unsigned attrs, const Shape *shape = nullptr)
{
    bool enumerable = shape ? shape->enumerable() : false;
    bool writable = shape ? shape->writable() : false;
    bool configurable = shape ? shape->configurable() : false;
    return ApplyAttributes(attrs, enumerable, writable, configurable);
}

static unsigned
ApplyOrDefaultAttributes(unsigned attrs, Handle<PropertyDescriptor> desc)
{
    bool present = !!desc.object();
    bool enumerable = present ? desc.isEnumerable() : false;
    bool writable = present ? !desc.isReadonly() : false;
    bool configurable = present ? !desc.isPermanent() : false;
    return ApplyAttributes(attrs, enumerable, writable, configurable);
}

// See comments on CheckDefineProperty in jsfriendapi.h.
//
// DefinePropertyOnObject has its own implementation of these checks.
//
JS_FRIEND_API(bool)
js::CheckDefineProperty(JSContext *cx, HandleObject obj, HandleId id, HandleValue value,
                        unsigned attrs, PropertyOp getter, StrictPropertyOp setter)
{
    if (!obj->isNative())
        return true;

    // ES5 8.12.9 Step 1. Even though we know obj is native, we use generic
    // APIs for shorter, more readable code.
    Rooted<PropertyDescriptor> desc(cx);
    if (!GetOwnPropertyDescriptor(cx, obj, id, &desc))
        return false;

    // Appropriately handle the potential for ignored attributes. Since the proxy code calls us
    // directly, these might flow in legitimately. Ensure that we compare against the values that
    // are intended.
    attrs = ApplyOrDefaultAttributes(attrs, desc) & ~JSPROP_IGNORE_VALUE;

    // This does not have to check obj's extensibility when !desc.obj (steps
    // 2-3) because the low-level methods JSObject::{add,put}Property check
    // for that.
    if (desc.object() && desc.isPermanent()) {
        // Steps 6-11, skipping step 10.a.ii. Prohibit redefining a permanent
        // property with different metadata, except to make a writable property
        // non-writable.
        if ((getter != desc.getter() && !(getter == JS_PropertyStub && !desc.getter())) ||
            (setter != desc.setter() && !(setter == JS_StrictPropertyStub && !desc.setter())) ||
            (attrs != desc.attributes() && attrs != (desc.attributes() | JSPROP_READONLY)))
        {
            return Throw(cx, id, JSMSG_CANT_REDEFINE_PROP);
        }

        // Step 10.a.ii. Prohibit changing the value of a non-configurable,
        // non-writable data property.
        if ((desc.attributes() & (JSPROP_GETTER | JSPROP_SETTER | JSPROP_READONLY)) == JSPROP_READONLY) {
            bool same;
            if (!SameValue(cx, value, desc.value(), &same))
                return false;
            if (!same)
                return JSObject::reportReadOnly(cx, id);
        }
    }
    return true;
}

static bool
DefinePropertyOnObject(JSContext *cx, HandleObject obj, HandleId id, const PropDesc &desc,
                       bool throwError, bool *rval)
{
    /* 8.12.9 step 1. */
    RootedShape shape(cx);
    RootedObject obj2(cx);
    JS_ASSERT(!obj->getOps()->lookupGeneric);
    if (!HasOwnProperty<CanGC>(cx, nullptr, obj, id, &obj2, &shape))
        return false;

    JS_ASSERT(!obj->getOps()->defineProperty);

    /* 8.12.9 steps 2-4. */
    if (!shape) {
        bool extensible;
        if (!JSObject::isExtensible(cx, obj, &extensible))
            return false;
        if (!extensible)
            return Reject(cx, obj, JSMSG_OBJECT_NOT_EXTENSIBLE, throwError, rval);

        *rval = true;

        if (desc.isGenericDescriptor() || desc.isDataDescriptor()) {
            JS_ASSERT(!obj->getOps()->defineProperty);
            RootedValue v(cx, desc.hasValue() ? desc.value() : UndefinedValue());
            return baseops::DefineGeneric(cx, obj, id, v,
                                          JS_PropertyStub, JS_StrictPropertyStub,
                                          desc.attributes());
        }

        JS_ASSERT(desc.isAccessorDescriptor());

        return baseops::DefineGeneric(cx, obj, id, UndefinedHandleValue,
                                      desc.getter(), desc.setter(), desc.attributes());
    }

    /* 8.12.9 steps 5-6 (note 5 is merely a special case of 6). */
    RootedValue v(cx);

    JS_ASSERT(obj == obj2);

    bool shapeDataDescriptor = true,
         shapeAccessorDescriptor = false,
         shapeWritable = true,
         shapeConfigurable = true,
         shapeEnumerable = true,
         shapeHasDefaultGetter = true,
         shapeHasDefaultSetter = true,
         shapeHasGetterValue = false,
         shapeHasSetterValue = false;
    uint8_t shapeAttributes = GetShapeAttributes(obj, shape);
    if (!IsImplicitDenseOrTypedArrayElement(shape)) {
        shapeDataDescriptor = shape->isDataDescriptor();
        shapeAccessorDescriptor = shape->isAccessorDescriptor();
        shapeWritable = shape->writable();
        shapeConfigurable = shape->configurable();
        shapeEnumerable = shape->enumerable();
        shapeHasDefaultGetter = shape->hasDefaultGetter();
        shapeHasDefaultSetter = shape->hasDefaultSetter();
        shapeHasGetterValue = shape->hasGetterValue();
        shapeHasSetterValue = shape->hasSetterValue();
        shapeAttributes = shape->attributes();
    }

    do {
        if (desc.isAccessorDescriptor()) {
            if (!shapeAccessorDescriptor)
                break;

            if (desc.hasGet()) {
                bool same;
                if (!SameValue(cx, desc.getterValue(), shape->getterOrUndefined(), &same))
                    return false;
                if (!same)
                    break;
            }

            if (desc.hasSet()) {
                bool same;
                if (!SameValue(cx, desc.setterValue(), shape->setterOrUndefined(), &same))
                    return false;
                if (!same)
                    break;
            }
        } else {
            /*
             * Determine the current value of the property once, if the current
             * value might actually need to be used or preserved later.  NB: we
             * guard on whether the current property is a data descriptor to
             * avoid calling a getter; we won't need the value if it's not a
             * data descriptor.
             */
            if (IsImplicitDenseOrTypedArrayElement(shape)) {
                v = obj->getDenseOrTypedArrayElement(JSID_TO_INT(id));
            } else if (shape->isDataDescriptor()) {
                /*
                 * We must rule out a non-configurable js::PropertyOp-guarded
                 * property becoming a writable unguarded data property, since
                 * such a property can have its value changed to one the getter
                 * and setter preclude.
                 *
                 * A desc lacking writable but with value is a data descriptor
                 * and we must reject it as if it had writable: true if current
                 * is writable.
                 */
                if (!shape->configurable() &&
                    (!shape->hasDefaultGetter() || !shape->hasDefaultSetter()) &&
                    desc.isDataDescriptor() &&
                    (desc.hasWritable() ? desc.writable() : shape->writable()))
                {
                    return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
                }

                if (!NativeGet(cx, obj, obj2, shape, &v))
                    return false;
            }

            if (desc.isDataDescriptor()) {
                if (!shapeDataDescriptor)
                    break;

                bool same;
                if (desc.hasValue()) {
                    if (!SameValue(cx, desc.value(), v, &same))
                        return false;
                    if (!same) {
                        /*
                         * Insist that a non-configurable js::PropertyOp data
                         * property is frozen at exactly the last-got value.
                         *
                         * Duplicate the first part of the big conjunction that
                         * we tested above, rather than add a local bool flag.
                         * Likewise, don't try to keep shape->writable() in a
                         * flag we veto from true to false for non-configurable
                         * PropertyOp-based data properties and test before the
                         * SameValue check later on in order to re-use that "if
                         * (!SameValue) Reject" logic.
                         *
                         * This function is large and complex enough that it
                         * seems best to repeat a small bit of code and return
                         * Reject(...) ASAP, instead of being clever.
                         */
                        if (!shapeConfigurable &&
                            (!shape->hasDefaultGetter() || !shape->hasDefaultSetter()))
                        {
                            return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
                        }
                        break;
                    }
                }
                if (desc.hasWritable() && desc.writable() != shapeWritable)
                    break;
            } else {
                /* The only fields in desc will be handled below. */
                JS_ASSERT(desc.isGenericDescriptor());
            }
        }

        if (desc.hasConfigurable() && desc.configurable() != shapeConfigurable)
            break;
        if (desc.hasEnumerable() && desc.enumerable() != shapeEnumerable)
            break;

        /* The conditions imposed by step 5 or step 6 apply. */
        *rval = true;
        return true;
    } while (0);

    /* 8.12.9 step 7. */
    if (!shapeConfigurable) {
        if ((desc.hasConfigurable() && desc.configurable()) ||
            (desc.hasEnumerable() && desc.enumerable() != shape->enumerable())) {
            return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
        }
    }

    bool callDelProperty = false;

    if (desc.isGenericDescriptor()) {
        /* 8.12.9 step 8, no validation required */
    } else if (desc.isDataDescriptor() != shapeDataDescriptor) {
        /* 8.12.9 step 9. */
        if (!shapeConfigurable)
            return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
    } else if (desc.isDataDescriptor()) {
        /* 8.12.9 step 10. */
        JS_ASSERT(shapeDataDescriptor);
        if (!shapeConfigurable && !shape->writable()) {
            if (desc.hasWritable() && desc.writable())
                return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
            if (desc.hasValue()) {
                bool same;
                if (!SameValue(cx, desc.value(), v, &same))
                    return false;
                if (!same)
                    return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
            }
        }

        callDelProperty = !shapeHasDefaultGetter || !shapeHasDefaultSetter;
    } else {
        /* 8.12.9 step 11. */
        JS_ASSERT(desc.isAccessorDescriptor() && shape->isAccessorDescriptor());
        if (!shape->configurable()) {
            if (desc.hasSet()) {
                bool same;
                if (!SameValue(cx, desc.setterValue(), shape->setterOrUndefined(), &same))
                    return false;
                if (!same)
                    return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
            }

            if (desc.hasGet()) {
                bool same;
                if (!SameValue(cx, desc.getterValue(), shape->getterOrUndefined(), &same))
                    return false;
                if (!same)
                    return Reject(cx, JSMSG_CANT_REDEFINE_PROP, throwError, id, rval);
            }
        }
    }

    /* 8.12.9 step 12. */
    unsigned attrs;
    PropertyOp getter;
    StrictPropertyOp setter;
    if (desc.isGenericDescriptor()) {
        unsigned changed = 0;
        if (desc.hasConfigurable())
            changed |= JSPROP_PERMANENT;
        if (desc.hasEnumerable())
            changed |= JSPROP_ENUMERATE;

        attrs = (shapeAttributes & ~changed) | (desc.attributes() & changed);
        getter = IsImplicitDenseOrTypedArrayElement(shape) ? JS_PropertyStub : shape->getter();
        setter = IsImplicitDenseOrTypedArrayElement(shape) ? JS_StrictPropertyStub : shape->setter();
    } else if (desc.isDataDescriptor()) {
        unsigned unchanged = 0;
        if (!desc.hasConfigurable())
            unchanged |= JSPROP_PERMANENT;
        if (!desc.hasEnumerable())
            unchanged |= JSPROP_ENUMERATE;
        /* Watch out for accessor -> data transformations here. */
        if (!desc.hasWritable() && shapeDataDescriptor)
            unchanged |= JSPROP_READONLY;

        if (desc.hasValue())
            v = desc.value();
        attrs = (desc.attributes() & ~unchanged) | (shapeAttributes & unchanged);
        getter = JS_PropertyStub;
        setter = JS_StrictPropertyStub;
    } else {
        JS_ASSERT(desc.isAccessorDescriptor());

        /* 8.12.9 step 12. */
        unsigned changed = 0;
        if (desc.hasConfigurable())
            changed |= JSPROP_PERMANENT;
        if (desc.hasEnumerable())
            changed |= JSPROP_ENUMERATE;
        if (desc.hasGet())
            changed |= JSPROP_GETTER | JSPROP_SHARED | JSPROP_READONLY;
        if (desc.hasSet())
            changed |= JSPROP_SETTER | JSPROP_SHARED | JSPROP_READONLY;

        attrs = (desc.attributes() & changed) | (shapeAttributes & ~changed);
        if (desc.hasGet()) {
            getter = desc.getter();
        } else {
            getter = (shapeHasDefaultGetter && !shapeHasGetterValue)
                     ? JS_PropertyStub
                     : shape->getter();
        }
        if (desc.hasSet()) {
            setter = desc.setter();
        } else {
            setter = (shapeHasDefaultSetter && !shapeHasSetterValue)
                     ? JS_StrictPropertyStub
                     : shape->setter();
        }
    }

    *rval = true;

    /*
     * Since "data" properties implemented using native C functions may rely on
     * side effects during setting, we must make them aware that they have been
     * "assigned"; deleting the property before redefining it does the trick.
     * See bug 539766, where we ran into problems when we redefined
     * arguments.length without making the property aware that its value had
     * been changed (which would have happened if we had deleted it before
     * redefining it or we had invoked its setter to change its value).
     */
    if (callDelProperty) {
        bool succeeded;
        if (!CallJSDeletePropertyOp(cx, obj2->getClass()->delProperty, obj2, id, &succeeded))
            return false;
    }

    return baseops::DefineGeneric(cx, obj, id, v, getter, setter, attrs);
}

/* ES6 20130308 draft 8.4.2.1 [[DefineOwnProperty]] */
static bool
DefinePropertyOnArray(JSContext *cx, Handle<ArrayObject*> arr, HandleId id, const PropDesc &desc,
                      bool throwError, bool *rval)
{
    /* Step 2. */
    if (id == NameToId(cx->names().length)) {
        // Canonicalize value, if necessary, before proceeding any further.  It
        // would be better if this were always/only done by ArraySetLength.
        // But canonicalization may throw a RangeError (or other exception, if
        // the value is an object with user-defined conversion semantics)
        // before other attributes are checked.  So as long as our internal
        // defineProperty hook doesn't match the ECMA one, this duplicate
        // checking can't be helped.
        RootedValue v(cx);
        if (desc.hasValue()) {
            uint32_t newLen;
            if (!CanonicalizeArrayLengthValue<SequentialExecution>(cx, desc.value(), &newLen))
                return false;
            v.setNumber(newLen);
        } else {
            v.setNumber(arr->length());
        }

        if (desc.hasConfigurable() && desc.configurable())
            return Reject(cx, id, JSMSG_CANT_REDEFINE_PROP, throwError, rval);
        if (desc.hasEnumerable() && desc.enumerable())
            return Reject(cx, id, JSMSG_CANT_REDEFINE_PROP, throwError, rval);

        if (desc.isAccessorDescriptor())
            return Reject(cx, id, JSMSG_CANT_REDEFINE_PROP, throwError, rval);

        unsigned attrs = arr->nativeLookup(cx, id)->attributes();
        if (!arr->lengthIsWritable()) {
            if (desc.hasWritable() && desc.writable())
                return Reject(cx, id, JSMSG_CANT_REDEFINE_PROP, throwError, rval);
        } else {
            if (desc.hasWritable() && !desc.writable())
                attrs = attrs | JSPROP_READONLY;
        }

        return ArraySetLength<SequentialExecution>(cx, arr, id, attrs, v, throwError);
    }

    /* Step 3. */
    uint32_t index;
    if (js_IdIsIndex(id, &index)) {
        /* Step 3b. */
        uint32_t oldLen = arr->length();

        /* Steps 3a, 3e. */
        if (index >= oldLen && !arr->lengthIsWritable())
            return Reject(cx, arr, JSMSG_CANT_APPEND_TO_ARRAY, throwError, rval);

        /* Steps 3f-j. */
        return DefinePropertyOnObject(cx, arr, id, desc, throwError, rval);
    }

    /* Step 4. */
    return DefinePropertyOnObject(cx, arr, id, desc, throwError, rval);
}

bool
js::DefineProperty(JSContext *cx, HandleObject obj, HandleId id, const PropDesc &desc,
                   bool throwError, bool *rval)
{
    if (obj->is<ArrayObject>()) {
        Rooted<ArrayObject*> arr(cx, &obj->as<ArrayObject>());
        return DefinePropertyOnArray(cx, arr, id, desc, throwError, rval);
    }

    if (obj->getOps()->lookupGeneric) {
        if (obj->is<ProxyObject>()) {
            Rooted<PropertyDescriptor> pd(cx);
            desc.populatePropertyDescriptor(obj, &pd);
            pd.object().set(obj);
            return Proxy::defineProperty(cx, obj, id, &pd);
        }
        return Reject(cx, obj, JSMSG_OBJECT_NOT_EXTENSIBLE, throwError, rval);
    }

    return DefinePropertyOnObject(cx, obj, id, desc, throwError, rval);
}

bool
js::DefineOwnProperty(JSContext *cx, HandleObject obj, HandleId id, HandleValue descriptor,
                      bool *bp)
{
    Rooted<PropDesc> desc(cx);
    if (!desc.initialize(cx, descriptor))
        return false;

    bool rval;
    if (!DefineProperty(cx, obj, id, desc, true, &rval))
        return false;
    *bp = !!rval;
    return true;
}

bool
js::DefineOwnProperty(JSContext *cx, HandleObject obj, HandleId id,
                      Handle<PropertyDescriptor> descriptor, bool *bp)
{
    Rooted<PropDesc> desc(cx);

    desc.initFromPropertyDescriptor(descriptor);

    bool rval;
    if (!DefineProperty(cx, obj, id, desc, true, &rval))
        return false;
    *bp = !!rval;
    return true;
}


bool
js::ReadPropertyDescriptors(JSContext *cx, HandleObject props, bool checkAccessors,
                            AutoIdVector *ids, AutoPropDescVector *descs)
{
    if (!GetPropertyNames(cx, props, JSITER_OWNONLY | JSITER_SYMBOLS, ids))
        return false;

    RootedId id(cx);
    for (size_t i = 0, len = ids->length(); i < len; i++) {
        id = (*ids)[i];
        Rooted<PropDesc> desc(cx);
        RootedValue v(cx);
        if (!JSObject::getGeneric(cx, props, props, id, &v) ||
            !desc.initialize(cx, v, checkAccessors) ||
            !descs->append(desc))
        {
            return false;
        }
    }
    return true;
}

bool
js::DefineProperties(JSContext *cx, HandleObject obj, HandleObject props)
{
    AutoIdVector ids(cx);
    AutoPropDescVector descs(cx);
    if (!ReadPropertyDescriptors(cx, props, true, &ids, &descs))
        return false;

    if (obj->is<ArrayObject>()) {
        bool dummy;
        Rooted<ArrayObject*> arr(cx, &obj->as<ArrayObject>());
        for (size_t i = 0, len = ids.length(); i < len; i++) {
            if (!DefinePropertyOnArray(cx, arr, ids[i], descs[i], true, &dummy))
                return false;
        }
        return true;
    }

    if (obj->getOps()->lookupGeneric) {
        if (obj->is<ProxyObject>()) {
            Rooted<PropertyDescriptor> pd(cx);
            for (size_t i = 0, len = ids.length(); i < len; i++) {
                descs[i].populatePropertyDescriptor(obj, &pd);
                if (!Proxy::defineProperty(cx, obj, ids[i], &pd))
                    return false;
            }
            return true;
        }
        bool dummy;
        return Reject(cx, obj, JSMSG_OBJECT_NOT_EXTENSIBLE, true, &dummy);
    }

    bool dummy;
    for (size_t i = 0, len = ids.length(); i < len; i++) {
        if (!DefinePropertyOnObject(cx, obj, ids[i], descs[i], true, &dummy))
            return false;
    }

    return true;
}

extern bool
js_PopulateObject(JSContext *cx, HandleObject newborn, HandleObject props)
{
    return DefineProperties(cx, newborn, props);
}

js::types::TypeObject*
JSObject::uninlinedGetType(JSContext *cx)
{
    return getType(cx);
}

void
JSObject::uninlinedSetType(js::types::TypeObject *newType)
{
    setType(newType);
}

/* static */ inline unsigned
JSObject::getSealedOrFrozenAttributes(unsigned attrs, ImmutabilityType it)
{
    /* Make all attributes permanent; if freezing, make data attributes read-only. */
    if (it == FREEZE && !(attrs & (JSPROP_GETTER | JSPROP_SETTER)))
        return JSPROP_PERMANENT | JSPROP_READONLY;
    return JSPROP_PERMANENT;
}

/* static */ bool
JSObject::sealOrFreeze(JSContext *cx, HandleObject obj, ImmutabilityType it)
{
    assertSameCompartment(cx, obj);
    JS_ASSERT(it == SEAL || it == FREEZE);

    bool extensible;
    if (!JSObject::isExtensible(cx, obj, &extensible))
        return false;
    if (extensible && !JSObject::preventExtensions(cx, obj))
        return false;

    AutoIdVector props(cx);
    if (!GetPropertyNames(cx, obj, JSITER_HIDDEN | JSITER_OWNONLY | JSITER_SYMBOLS, &props))
        return false;

    /* preventExtensions must sparsify dense objects, so we can assign to holes without checks. */
    JS_ASSERT_IF(obj->isNative(), obj->getDenseCapacity() == 0);

    if (obj->isNative() && !obj->inDictionaryMode() && !obj->is<TypedArrayObject>()) {
        /*
         * Seal/freeze non-dictionary objects by constructing a new shape
         * hierarchy mirroring the original one, which can be shared if many
         * objects with the same structure are sealed/frozen. If we use the
         * generic path below then any non-empty object will be converted to
         * dictionary mode.
         */
        RootedShape last(cx, EmptyShape::getInitialShape(cx, obj->getClass(),
                                                         obj->getTaggedProto(),
                                                         obj->getParent(),
                                                         obj->getMetadata(),
                                                         obj->numFixedSlots(),
                                                         obj->lastProperty()->getObjectFlags()));
        if (!last)
            return false;

        /* Get an in order list of the shapes in this object. */
        AutoShapeVector shapes(cx);
        for (Shape::Range<NoGC> r(obj->lastProperty()); !r.empty(); r.popFront()) {
            if (!shapes.append(&r.front()))
                return false;
        }
        Reverse(shapes.begin(), shapes.end());

        for (size_t i = 0; i < shapes.length(); i++) {
            StackShape unrootedChild(shapes[i]);
            RootedGeneric<StackShape*> child(cx, &unrootedChild);
            child->attrs |= getSealedOrFrozenAttributes(child->attrs, it);

            if (!JSID_IS_EMPTY(child->propid) && it == FREEZE)
                MarkTypePropertyNonWritable(cx, obj, child->propid);

            last = cx->compartment()->propertyTree.getChild(cx, last, *child);
            if (!last)
                return false;
        }

        JS_ASSERT(obj->lastProperty()->slotSpan() == last->slotSpan());
        JS_ALWAYS_TRUE(setLastProperty(cx, obj, last));
    } else {
        RootedId id(cx);
        for (size_t i = 0; i < props.length(); i++) {
            id = props[i];

            unsigned attrs;
            if (!getGenericAttributes(cx, obj, id, &attrs))
                return false;

            unsigned new_attrs = getSealedOrFrozenAttributes(attrs, it);

            /* If we already have the attributes we need, skip the setAttributes call. */
            if ((attrs | new_attrs) == attrs)
                continue;

            attrs |= new_attrs;
            if (!setGenericAttributes(cx, obj, id, &attrs))
                return false;
        }
    }

    // Ordinarily ArraySetLength handles this, but we're going behind its back
    // right now, so we must do this manually.  Neither the custom property
    // tree mutations nor the setGenericAttributes call in the above code will
    // do this for us.
    //
    // ArraySetLength also implements the capacity <= length invariant for
    // arrays with non-writable length.  We don't need to do anything special
    // for that, because capacity was zeroed out by preventExtensions.  (See
    // the assertion before the if-else above.)
    if (it == FREEZE && obj->is<ArrayObject>()) {
        if (!obj->maybeCopyElementsForWrite(cx))
            return false;
        obj->getElementsHeader()->setNonwritableArrayLength();
    }

    return true;
}

/* static */ bool
JSObject::isSealedOrFrozen(JSContext *cx, HandleObject obj, ImmutabilityType it, bool *resultp)
{
    bool extensible;
    if (!JSObject::isExtensible(cx, obj, &extensible))
        return false;
    if (extensible) {
        *resultp = false;
        return true;
    }

    if (obj->is<TypedArrayObject>()) {
        if (it == SEAL) {
            // Typed arrays are always sealed.
            *resultp = true;
        } else {
            // Typed arrays cannot be frozen, but an empty typed array is
            // trivially frozen.
            *resultp = (obj->as<TypedArrayObject>().length() == 0);
        }
        return true;
    }

    AutoIdVector props(cx);
    if (!GetPropertyNames(cx, obj, JSITER_HIDDEN | JSITER_OWNONLY | JSITER_SYMBOLS, &props))
        return false;

    RootedId id(cx);
    for (size_t i = 0, len = props.length(); i < len; i++) {
        id = props[i];

        unsigned attrs;
        if (!getGenericAttributes(cx, obj, id, &attrs))
            return false;

        /*
         * If the property is configurable, this object is neither sealed nor
         * frozen. If the property is a writable data property, this object is
         * not frozen.
         */
        if (!(attrs & JSPROP_PERMANENT) ||
            (it == FREEZE && !(attrs & (JSPROP_READONLY | JSPROP_GETTER | JSPROP_SETTER))))
        {
            *resultp = false;
            return true;
        }
    }

    /* All properties checked out. This object is sealed/frozen. */
    *resultp = true;
    return true;
}

/* static */
const char *
JSObject::className(JSContext *cx, HandleObject obj)
{
    assertSameCompartment(cx, obj);

    if (obj->is<ProxyObject>())
        return Proxy::className(cx, obj);

    return obj->getClass()->name;
}

/*
 * Get the GC kind to use for scripted 'new' on the given class.
 * FIXME bug 547327: estimate the size from the allocation site.
 */
static inline gc::AllocKind
NewObjectGCKind(const js::Class *clasp)
{
    if (clasp == &ArrayObject::class_)
        return gc::FINALIZE_OBJECT8;
    if (clasp == &JSFunction::class_)
        return gc::FINALIZE_OBJECT2;
    return gc::FINALIZE_OBJECT4;
}

static inline JSObject *
NewObject(ExclusiveContext *cx, types::TypeObject *type_, JSObject *parent, gc::AllocKind kind,
          NewObjectKind newKind)
{
    const Class *clasp = type_->clasp();

    JS_ASSERT(clasp != &ArrayObject::class_);
    JS_ASSERT_IF(clasp == &JSFunction::class_,
                 kind == JSFunction::FinalizeKind || kind == JSFunction::ExtendedFinalizeKind);
    JS_ASSERT_IF(parent, &parent->global() == cx->global());

    RootedTypeObject type(cx, type_);

    JSObject *metadata = nullptr;
    if (!NewObjectMetadata(cx, &metadata))
        return nullptr;

    // For objects which can have fixed data following the object, only use
    // enough fixed slots to cover the number of reserved slots in the object,
    // regardless of the allocation kind specified.
    size_t nfixed = ClassCanHaveFixedData(clasp)
                    ? GetGCKindSlots(gc::GetGCObjectKind(clasp), clasp)
                    : GetGCKindSlots(kind, clasp);

    RootedShape shape(cx, EmptyShape::getInitialShape(cx, clasp, type->proto(),
                                                      parent, metadata, nfixed));
    if (!shape)
        return nullptr;

    gc::InitialHeap heap = GetInitialHeap(newKind, clasp);
    JSObject *obj = JSObject::create(cx, kind, heap, shape, type);
    if (!obj)
        return nullptr;

    if (newKind == SingletonObject) {
        RootedObject nobj(cx, obj);
        if (!JSObject::setSingletonType(cx, nobj))
            return nullptr;
        obj = nobj;
    }

    /*
     * This will cancel an already-running incremental GC from doing any more
     * slices, and it will prevent any future incremental GCs.
     */
    bool globalWithoutCustomTrace = clasp->trace == JS_GlobalObjectTraceHook &&
                                    !cx->compartment()->options().getTrace();
    if (clasp->trace &&
        !globalWithoutCustomTrace &&
        !(clasp->flags & JSCLASS_IMPLEMENTS_BARRIERS))
    {
        if (!cx->shouldBeJSContext())
            return nullptr;
        JSRuntime *rt = cx->asJSContext()->runtime();
        rt->gc.disallowIncrementalGC();

#ifdef DEBUG
        if (rt->gc.gcMode() == JSGC_MODE_INCREMENTAL) {
            fprintf(stderr,
                    "The class %s has a trace hook but does not declare the\n"
                    "JSCLASS_IMPLEMENTS_BARRIERS flag. Please ensure that it correctly\n"
                    "implements write barriers and then set the flag.\n",
                    clasp->name);
            MOZ_CRASH();
        }
#endif
    }

    probes::CreateObject(cx, obj);
    return obj;
}

void
NewObjectCache::fillProto(EntryIndex entry, const Class *clasp, js::TaggedProto proto,
                          gc::AllocKind kind, JSObject *obj)
{
    JS_ASSERT_IF(proto.isObject(), !proto.toObject()->is<GlobalObject>());
    JS_ASSERT(obj->getTaggedProto() == proto);
    return fill(entry, clasp, proto.raw(), kind, obj);
}

JSObject *
js::NewObjectWithGivenProto(ExclusiveContext *cxArg, const js::Class *clasp,
                            js::TaggedProto protoArg, JSObject *parentArg,
                            gc::AllocKind allocKind, NewObjectKind newKind)
{
    if (CanBeFinalizedInBackground(allocKind, clasp))
        allocKind = GetBackgroundAllocKind(allocKind);

    NewObjectCache::EntryIndex entry = -1;
    uint64_t gcNumber = 0;
    if (JSContext *cx = cxArg->maybeJSContext()) {
        JSRuntime *rt = cx->runtime();
        NewObjectCache &cache = rt->newObjectCache;
        if (protoArg.isObject() &&
            newKind == GenericObject &&
            !cx->compartment()->hasObjectMetadataCallback() &&
            (!parentArg || parentArg == protoArg.toObject()->getParent()) &&
            !protoArg.toObject()->is<GlobalObject>())
        {
            if (cache.lookupProto(clasp, protoArg.toObject(), allocKind, &entry)) {
                JSObject *obj = cache.newObjectFromHit<NoGC>(cx, entry, GetInitialHeap(newKind, clasp));
                if (obj) {
                    return obj;
                } else {
                    Rooted<TaggedProto> proto(cxArg, protoArg);
                    RootedObject parent(cxArg, parentArg);
                    obj = cache.newObjectFromHit<CanGC>(cx, entry, GetInitialHeap(newKind, clasp));
                    JS_ASSERT(!obj);
                    parentArg = parent;
                    protoArg = proto;
                }
            } else {
                gcNumber = rt->gc.gcNumber();
            }
        }
    }

    Rooted<TaggedProto> proto(cxArg, protoArg);
    RootedObject parent(cxArg, parentArg);

    types::TypeObject *type = cxArg->getNewType(clasp, proto, nullptr);
    if (!type)
        return nullptr;

    /*
     * Default parent to the parent of the prototype, which was set from
     * the parent of the prototype's constructor.
     */
    if (!parent && proto.isObject())
        parent = proto.toObject()->getParent();

    RootedObject obj(cxArg, NewObject(cxArg, type, parent, allocKind, newKind));
    if (!obj)
        return nullptr;

    if (entry != -1 && !obj->hasDynamicSlots() &&
        cxArg->asJSContext()->runtime()->gc.gcNumber() == gcNumber)
    {
        cxArg->asJSContext()->runtime()->newObjectCache.fillProto(entry, clasp,
                                                                  proto, allocKind, obj);
    }

    return obj;
}

static JSProtoKey
ClassProtoKeyOrAnonymousOrNull(const js::Class *clasp)
{
    JSProtoKey key = JSCLASS_CACHED_PROTO_KEY(clasp);
    if (key != JSProto_Null)
        return key;
    if (clasp->flags & JSCLASS_IS_ANONYMOUS)
        return JSProto_Object;
    return JSProto_Null;
}

JSObject *
js::NewObjectWithClassProtoCommon(ExclusiveContext *cxArg,
                                  const js::Class *clasp, JSObject *protoArg, JSObject *parentArg,
                                  gc::AllocKind allocKind, NewObjectKind newKind)
{
    if (protoArg)
        return NewObjectWithGivenProto(cxArg, clasp, TaggedProto(protoArg), parentArg, allocKind, newKind);

    if (CanBeFinalizedInBackground(allocKind, clasp))
        allocKind = GetBackgroundAllocKind(allocKind);

    if (!parentArg)
        parentArg = cxArg->global();

    /*
     * Use the object cache, except for classes without a cached proto key.
     * On these objects, FindProto will do a dynamic property lookup to get
     * global[className].prototype, where changes to either the className or
     * prototype property would render the cached lookup incorrect. For classes
     * with a proto key, the prototype created during class initialization is
     * stored in an immutable slot on the global (except for ClearScope, which
     * will flush the new object cache).
     */
    JSProtoKey protoKey = ClassProtoKeyOrAnonymousOrNull(clasp);

    NewObjectCache::EntryIndex entry = -1;
    if (JSContext *cx = cxArg->maybeJSContext()) {
        NewObjectCache &cache = cx->runtime()->newObjectCache;
        if (parentArg->is<GlobalObject>() &&
            protoKey != JSProto_Null &&
            newKind == GenericObject &&
            !cx->compartment()->hasObjectMetadataCallback())
        {
            if (cache.lookupGlobal(clasp, &parentArg->as<GlobalObject>(), allocKind, &entry)) {
                JSObject *obj = cache.newObjectFromHit<NoGC>(cx, entry, GetInitialHeap(newKind, clasp));
                if (obj) {
                    return obj;
                } else {
                    RootedObject parent(cxArg, parentArg);
                    RootedObject proto(cxArg, protoArg);
                    obj = cache.newObjectFromHit<CanGC>(cx, entry, GetInitialHeap(newKind, clasp));
                    JS_ASSERT(!obj);
                    protoArg = proto;
                    parentArg = parent;
                }
            }
        }
    }

    RootedObject parent(cxArg, parentArg);
    RootedObject proto(cxArg, protoArg);

    if (!FindProto(cxArg, clasp, &proto))
        return nullptr;

    Rooted<TaggedProto> taggedProto(cxArg, TaggedProto(proto));
    types::TypeObject *type = cxArg->getNewType(clasp, taggedProto);
    if (!type)
        return nullptr;

    JSObject *obj = NewObject(cxArg, type, parent, allocKind, newKind);
    if (!obj)
        return nullptr;

    if (entry != -1 && !obj->hasDynamicSlots()) {
        cxArg->asJSContext()->runtime()->newObjectCache.fillGlobal(entry, clasp,
                                                                   &parent->as<GlobalObject>(),
                                                                   allocKind, obj);
    }

    return obj;
}

/*
 * Create a plain object with the specified type. This bypasses getNewType to
 * avoid losing creation site information for objects made by scripted 'new'.
 */
JSObject *
js::NewObjectWithType(JSContext *cx, HandleTypeObject type, JSObject *parent, gc::AllocKind allocKind,
                      NewObjectKind newKind)
{
    JS_ASSERT(parent);

    JS_ASSERT(allocKind <= gc::FINALIZE_OBJECT_LAST);
    if (CanBeFinalizedInBackground(allocKind, type->clasp()))
        allocKind = GetBackgroundAllocKind(allocKind);

    NewObjectCache &cache = cx->runtime()->newObjectCache;

    NewObjectCache::EntryIndex entry = -1;
    if (parent == type->proto().toObject()->getParent() &&
        newKind == GenericObject &&
        !cx->compartment()->hasObjectMetadataCallback())
    {
        if (cache.lookupType(type, allocKind, &entry)) {
            JSObject *obj = cache.newObjectFromHit<NoGC>(cx, entry, GetInitialHeap(newKind, type->clasp()));
            if (obj) {
                return obj;
            } else {
                obj = cache.newObjectFromHit<CanGC>(cx, entry, GetInitialHeap(newKind, type->clasp()));
                parent = type->proto().toObject()->getParent();
            }
        }
    }

    JSObject *obj = NewObject(cx, type, parent, allocKind, newKind);
    if (!obj)
        return nullptr;

    if (entry != -1 && !obj->hasDynamicSlots())
        cache.fillType(entry, type, allocKind, obj);

    return obj;
}

bool
js::NewObjectScriptedCall(JSContext *cx, MutableHandleObject pobj)
{
    jsbytecode *pc;
    RootedScript script(cx, cx->currentScript(&pc));
    gc::AllocKind allocKind = NewObjectGCKind(&JSObject::class_);
    NewObjectKind newKind = script
                            ? UseNewTypeForInitializer(script, pc, &JSObject::class_)
                            : GenericObject;
    RootedObject obj(cx, NewBuiltinClassInstance(cx, &JSObject::class_, allocKind, newKind));
    if (!obj)
        return false;

    if (script) {
        /* Try to specialize the type of the object to the scripted call site. */
        if (!types::SetInitializerObjectType(cx, script, pc, obj, newKind))
            return false;
    }

    pobj.set(obj);
    return true;
}

JSObject*
js::CreateThis(JSContext *cx, const Class *newclasp, HandleObject callee)
{
    RootedValue protov(cx);
    if (!JSObject::getProperty(cx, callee, callee, cx->names().prototype, &protov))
        return nullptr;

    JSObject *proto = protov.isObjectOrNull() ? protov.toObjectOrNull() : nullptr;
    JSObject *parent = callee->getParent();
    gc::AllocKind kind = NewObjectGCKind(newclasp);
    return NewObjectWithClassProto(cx, newclasp, proto, parent, kind);
}

static inline JSObject *
CreateThisForFunctionWithType(JSContext *cx, HandleTypeObject type, JSObject *parent,
                              NewObjectKind newKind)
{
    if (type->newScript()) {
        /*
         * Make an object with the type's associated finalize kind and shape,
         * which reflects any properties that will definitely be added to the
         * object before it is read from.
         */
        RootedObject templateObject(cx, type->newScript()->templateObject);
        JS_ASSERT(templateObject->type() == type);

        RootedObject res(cx, CopyInitializerObject(cx, templateObject, newKind));
        if (!res)
            return nullptr;
        if (newKind == SingletonObject) {
            Rooted<TaggedProto> proto(cx, TaggedProto(templateObject->getProto()));
            if (!res->splicePrototype(cx, &JSObject::class_, proto))
                return nullptr;
        } else {
            res->setType(type);
        }
        return res;
    }

    gc::AllocKind allocKind = NewObjectGCKind(&JSObject::class_);
    return NewObjectWithType(cx, type, parent, allocKind, newKind);
}

JSObject *
js::CreateThisForFunctionWithProto(JSContext *cx, HandleObject callee, JSObject *proto,
                                   NewObjectKind newKind /* = GenericObject */)
{
    RootedObject res(cx);

    if (proto) {
        RootedTypeObject type(cx, cx->getNewType(&JSObject::class_, TaggedProto(proto), &callee->as<JSFunction>()));
        if (!type)
            return nullptr;
        res = CreateThisForFunctionWithType(cx, type, callee->getParent(), newKind);
    } else {
        gc::AllocKind allocKind = NewObjectGCKind(&JSObject::class_);
        res = NewObjectWithClassProto(cx, &JSObject::class_, proto, callee->getParent(), allocKind, newKind);
    }

    if (res) {
        JSScript *script = callee->as<JSFunction>().getOrCreateScript(cx);
        if (!script)
            return nullptr;
        TypeScript::SetThis(cx, script, types::Type::ObjectType(res));
    }

    return res;
}

JSObject *
js::CreateThisForFunction(JSContext *cx, HandleObject callee, NewObjectKind newKind)
{
    RootedValue protov(cx);
    if (!JSObject::getProperty(cx, callee, callee, cx->names().prototype, &protov))
        return nullptr;
    JSObject *proto;
    if (protov.isObject())
        proto = &protov.toObject();
    else
        proto = nullptr;
    JSObject *obj = CreateThisForFunctionWithProto(cx, callee, proto, newKind);

    if (obj && newKind == SingletonObject) {
        RootedObject nobj(cx, obj);

        /* Reshape the singleton before passing it as the 'this' value. */
        JSObject::clear(cx, nobj);

        JSScript *calleeScript = callee->as<JSFunction>().nonLazyScript();
        TypeScript::SetThis(cx, calleeScript, types::Type::ObjectType(nobj));

        return nobj;
    }

    return obj;
}

/*
 * Given pc pointing after a property accessing bytecode, return true if the
 * access is "object-detecting" in the sense used by web scripts, e.g., when
 * checking whether document.all is defined.
 */
static bool
Detecting(JSContext *cx, JSScript *script, jsbytecode *pc)
{
    JS_ASSERT(script->containsPC(pc));

    /* General case: a branch or equality op follows the access. */
    JSOp op = JSOp(*pc);
    if (js_CodeSpec[op].format & JOF_DETECTING)
        return true;

    jsbytecode *endpc = script->codeEnd();

    if (op == JSOP_NULL) {
        /*
         * Special case #1: handle (document.all == null).  Don't sweat
         * about JS1.2's revision of the equality operators here.
         */
        if (++pc < endpc) {
            op = JSOp(*pc);
            return op == JSOP_EQ || op == JSOP_NE;
        }
        return false;
    }

    if (op == JSOP_GETGNAME || op == JSOP_NAME) {
        /*
         * Special case #2: handle (document.all == undefined).  Don't worry
         * about a local variable named |undefined| shadowing the immutable
         * global binding...because, really?
         */
        JSAtom *atom = script->getAtom(GET_UINT32_INDEX(pc));
        if (atom == cx->names().undefined &&
            (pc += js_CodeSpec[op].length) < endpc) {
            op = JSOp(*pc);
            return op == JSOP_EQ || op == JSOP_NE || op == JSOP_STRICTEQ || op == JSOP_STRICTNE;
        }
    }

    return false;
}

/* static */ bool
JSObject::nonNativeSetProperty(JSContext *cx, HandleObject obj,
                               HandleId id, MutableHandleValue vp, bool strict)
{
    if (MOZ_UNLIKELY(obj->watched())) {
        WatchpointMap *wpmap = cx->compartment()->watchpointMap;
        if (wpmap && !wpmap->triggerWatchpoint(cx, obj, id, vp))
            return false;
    }
    return obj->getOps()->setGeneric(cx, obj, id, vp, strict);
}

/* static */ bool
JSObject::nonNativeSetElement(JSContext *cx, HandleObject obj,
                              uint32_t index, MutableHandleValue vp, bool strict)
{
    if (MOZ_UNLIKELY(obj->watched())) {
        RootedId id(cx);
        if (!IndexToId(cx, index, &id))
            return false;

        WatchpointMap *wpmap = cx->compartment()->watchpointMap;
        if (wpmap && !wpmap->triggerWatchpoint(cx, obj, id, vp))
            return false;
    }
    return obj->getOps()->setElement(cx, obj, index, vp, strict);
}

JS_FRIEND_API(bool)
JS_CopyPropertyFrom(JSContext *cx, HandleId id, HandleObject target,
                    HandleObject obj)
{
    // |obj| and |cx| are generally not same-compartment with |target| here.
    assertSameCompartment(cx, obj, id);
    Rooted<JSPropertyDescriptor> desc(cx);

    if (!GetOwnPropertyDescriptor(cx, obj, id, &desc))
        return false;
    MOZ_ASSERT(desc.object());

    // Silently skip JSPropertyOp-implemented accessors.
    if (desc.getter() && !desc.hasGetterObject())
        return true;
    if (desc.setter() && !desc.hasSetterObject())
        return true;

    JSAutoCompartment ac(cx, target);
    RootedId wrappedId(cx, id);
    if (!cx->compartment()->wrap(cx, &desc))
        return false;

    bool ignored;
    return DefineOwnProperty(cx, target, wrappedId, desc, &ignored);
}

JS_FRIEND_API(bool)
JS_CopyPropertiesFrom(JSContext *cx, HandleObject target, HandleObject obj)
{
    JSAutoCompartment ac(cx, obj);

    AutoIdVector props(cx);
    if (!GetPropertyNames(cx, obj, JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS, &props))
        return false;

    for (size_t i = 0; i < props.length(); ++i) {
        if (!JS_CopyPropertyFrom(cx, props[i], target, obj))
            return false;
    }

    return true;
}

static bool
CopySlots(JSContext *cx, HandleObject from, HandleObject to)
{
    JS_ASSERT(!from->isNative() && !to->isNative());
    JS_ASSERT(from->getClass() == to->getClass());

    size_t n = 0;
    if (from->is<WrapperObject>() &&
        (Wrapper::wrapperHandler(from)->flags() &
         Wrapper::CROSS_COMPARTMENT)) {
        to->setSlot(0, from->getSlot(0));
        to->setSlot(1, from->getSlot(1));
        n = 2;
    }

    size_t span = JSCLASS_RESERVED_SLOTS(from->getClass());
    RootedValue v(cx);
    for (; n < span; ++n) {
        v = from->getSlot(n);
        if (!cx->compartment()->wrap(cx, &v))
            return false;
        to->setSlot(n, v);
    }
    return true;
}

JSObject *
js::CloneObject(JSContext *cx, HandleObject obj, Handle<js::TaggedProto> proto, HandleObject parent)
{
    if (!obj->isNative() && !obj->is<ProxyObject>()) {
        JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr,
                             JSMSG_CANT_CLONE_OBJECT);
        return nullptr;
    }

    RootedObject clone(cx, NewObjectWithGivenProto(cx, obj->getClass(), proto, parent));
    if (!clone)
        return nullptr;
    if (obj->isNative()) {
        if (clone->is<JSFunction>() && (obj->compartment() != clone->compartment())) {
            JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr,
                                 JSMSG_CANT_CLONE_OBJECT);
            return nullptr;
        }

        if (obj->hasPrivate())
            clone->setPrivate(obj->getPrivate());
    } else {
        JS_ASSERT(obj->is<ProxyObject>());
        if (!CopySlots(cx, obj, clone))
            return nullptr;
    }

    return clone;
}

JSObject *
js::DeepCloneObjectLiteral(JSContext *cx, HandleObject obj, NewObjectKind newKind)
{
    /* NB: Keep this in sync with XDRObjectLiteral. */
    JS_ASSERT_IF(obj->hasSingletonType(),
                 JS::CompartmentOptionsRef(cx).getSingletonsAsTemplates());
    JS_ASSERT(obj->is<JSObject>() || obj->is<ArrayObject>());

    // Result of the clone function.
    RootedObject clone(cx);

    // Temporary element/slot which would be stored in the cloned object.
    RootedValue v(cx);
    RootedObject deepObj(cx);

    if (obj->is<ArrayObject>()) {
        clone = NewDenseUnallocatedArray(cx, obj->as<ArrayObject>().length(), nullptr, newKind);
    } else {
        // Object literals are tenured by default as holded by the JSScript.
        JS_ASSERT(obj->isTenured());
        AllocKind kind = obj->tenuredGetAllocKind();
        Rooted<TypeObject*> typeObj(cx, obj->getType(cx));
        if (!typeObj)
            return nullptr;
        RootedObject parent(cx, obj->getParent());
        clone = NewObjectWithGivenProto(cx, &JSObject::class_, TaggedProto(typeObj->proto().toObject()),
                                        parent, kind, newKind);
    }

    // Allocate the same number of slots.
    if (!clone || !clone->ensureElements(cx, obj->getDenseCapacity()))
        return nullptr;

    // Copy the number of initialized elements.
    uint32_t initialized = obj->getDenseInitializedLength();
    if (initialized)
        clone->setDenseInitializedLength(initialized);

    // Recursive copy of dense element.
    for (uint32_t i = 0; i < initialized; ++i) {
        v = obj->getDenseElement(i);
        if (v.isObject()) {
            deepObj = &v.toObject();
            deepObj = js::DeepCloneObjectLiteral(cx, deepObj, newKind);
            if (!deepObj) {
                JS_ReportOutOfMemory(cx);
                return nullptr;
            }
            v.setObject(*deepObj);
        }
        clone->initDenseElement(i, v);
    }

    JS_ASSERT(obj->compartment() == clone->compartment());
    JS_ASSERT(!obj->hasPrivate());
    RootedShape shape(cx, obj->lastProperty());
    size_t span = shape->slotSpan();
    clone->setLastProperty(cx, clone, shape);
    for (size_t i = 0; i < span; i++) {
        v = obj->getSlot(i);
        if (v.isObject()) {
            deepObj = &v.toObject();
            deepObj = js::DeepCloneObjectLiteral(cx, deepObj, newKind);
            if (!deepObj)
                return nullptr;
            v.setObject(*deepObj);
        }
        clone->setSlot(i, v);
    }

    if (obj->hasSingletonType()) {
        if (!JSObject::setSingletonType(cx, clone))
            return nullptr;
    } else if (obj->getClass() == &ArrayObject::class_) {
        FixArrayType(cx, clone);
    } else {
        FixObjectType(cx, clone);
    }

    if (obj->is<ArrayObject>() && obj->denseElementsAreCopyOnWrite()) {
        if (!ObjectElements::MakeElementsCopyOnWrite(cx, clone))
            return nullptr;
    }

    return clone;
}

template<XDRMode mode>
bool
js::XDRObjectLiteral(XDRState<mode> *xdr, MutableHandleObject obj)
{
    /* NB: Keep this in sync with DeepCloneObjectLiteral. */

    JSContext *cx = xdr->cx();
    JS_ASSERT_IF(mode == XDR_ENCODE && obj->hasSingletonType(),
                 JS::CompartmentOptionsRef(cx).getSingletonsAsTemplates());

    // Distinguish between objects and array classes.
    uint32_t isArray = 0;
    {
        if (mode == XDR_ENCODE) {
            JS_ASSERT(obj->is<JSObject>() || obj->is<ArrayObject>());
            isArray = obj->getClass() == &ArrayObject::class_ ? 1 : 0;
        }

        if (!xdr->codeUint32(&isArray))
            return false;
    }

    if (isArray) {
        uint32_t length;

        if (mode == XDR_ENCODE)
            length = obj->as<ArrayObject>().length();

        if (!xdr->codeUint32(&length))
            return false;

        if (mode == XDR_DECODE)
            obj.set(NewDenseUnallocatedArray(cx, length, NULL, js::MaybeSingletonObject));

    } else {
        // Code the alloc kind of the object.
        AllocKind kind;
        {
            if (mode == XDR_ENCODE) {
                JS_ASSERT(obj->getClass() == &JSObject::class_);
                JS_ASSERT(obj->isTenured());
                kind = obj->tenuredGetAllocKind();
            }

            if (!xdr->codeEnum32(&kind))
                return false;

            if (mode == XDR_DECODE)
                obj.set(NewBuiltinClassInstance(cx, &JSObject::class_, kind, js::MaybeSingletonObject));
        }
    }

    {
        uint32_t capacity;
        if (mode == XDR_ENCODE)
            capacity = obj->getDenseCapacity();
        if (!xdr->codeUint32(&capacity))
            return false;
        if (mode == XDR_DECODE) {
            if (!obj->ensureElements(cx, capacity)) {
                JS_ReportOutOfMemory(cx);
                return false;
            }
        }
    }

    uint32_t initialized;
    {
        if (mode == XDR_ENCODE)
            initialized = obj->getDenseInitializedLength();
        if (!xdr->codeUint32(&initialized))
            return false;
        if (mode == XDR_DECODE) {
            if (initialized)
                obj->setDenseInitializedLength(initialized);
        }
    }

    RootedValue tmpValue(cx);

    // Recursively copy dense elements.
    {
        for (unsigned i = 0; i < initialized; i++) {
            if (mode == XDR_ENCODE)
                tmpValue = obj->getDenseElement(i);

            if (!xdr->codeConstValue(&tmpValue))
                return false;

            if (mode == XDR_DECODE)
                obj->initDenseElement(i, tmpValue);
        }
    }

    JS_ASSERT(!obj->hasPrivate());
    RootedShape shape(cx, obj->lastProperty());

    // Code the number of slots in the vector.
    unsigned nslot = 0;

    // Code ids of the object in order. As opposed to DeepCloneObjectLiteral we
    // cannot just re-use the shape of the original bytecode value and we have
    // to write down the shape as well as the corresponding values.  Ideally we
    // would have a mechanism to serialize the shape too.
    js::AutoIdVector ids(cx);
    {
        if (mode == XDR_ENCODE && !shape->isEmptyShape()) {
            nslot = shape->slotSpan();
            if (!ids.reserve(nslot))
                return false;

            for (unsigned i = 0; i < nslot; i++)
                ids.infallibleAppend(JSID_VOID);

            for (Shape::Range<NoGC> it(shape); !it.empty(); it.popFront()) {
                // If we have reached the native property of the array class, we
                // exit as the remaining would only be reserved slots.
                if (!it.front().hasSlot()) {
                    JS_ASSERT(isArray);
                    break;
                }

                JS_ASSERT(it.front().hasDefaultGetter());
                ids[it.front().slot()].set(it.front().propid());
            }
        }

        if (!xdr->codeUint32(&nslot))
            return false;

        RootedAtom atom(cx);
        RootedId id(cx);
        uint32_t idType = 0;
        for (unsigned i = 0; i < nslot; i++) {
            if (mode == XDR_ENCODE) {
                id = ids[i];
                if (JSID_IS_INT(id))
                    idType = JSID_TYPE_INT;
                else if (JSID_IS_ATOM(id))
                    idType = JSID_TYPE_STRING;
                else
                    MOZ_CRASH("Symbol property is not yet supported by XDR.");

                tmpValue = obj->getSlot(i);
            }

            if (!xdr->codeUint32(&idType))
                return false;

            if (idType == JSID_TYPE_STRING) {
                if (mode == XDR_ENCODE)
                    atom = JSID_TO_ATOM(id);
                if (!XDRAtom(xdr, &atom))
                    return false;
                if (mode == XDR_DECODE)
                    id = AtomToId(atom);
            } else {
                JS_ASSERT(idType == JSID_TYPE_INT);
                uint32_t indexVal;
                if (mode == XDR_ENCODE)
                    indexVal = uint32_t(JSID_TO_INT(id));
                if (!xdr->codeUint32(&indexVal))
                    return false;
                if (mode == XDR_DECODE)
                    id = INT_TO_JSID(int32_t(indexVal));
            }

            if (!xdr->codeConstValue(&tmpValue))
                return false;

            if (mode == XDR_DECODE) {
                if (!DefineNativeProperty(cx, obj, id, tmpValue, NULL, NULL, JSPROP_ENUMERATE))
                    return false;
            }
        }

        JS_ASSERT_IF(mode == XDR_DECODE, !obj->inDictionaryMode());
    }

    // Fix up types, distinguishing singleton-typed objects.
    uint32_t isSingletonTyped;
    if (mode == XDR_ENCODE)
        isSingletonTyped = obj->hasSingletonType() ? 1 : 0;
    if (!xdr->codeUint32(&isSingletonTyped))
        return false;

    if (mode == XDR_DECODE) {
        if (isSingletonTyped) {
            if (!JSObject::setSingletonType(cx, obj))
                return false;
        } else if (isArray) {
            FixArrayType(cx, obj);
        } else {
            FixObjectType(cx, obj);
        }
    }

    {
        uint32_t frozen;
        bool extensible;
        if (mode == XDR_ENCODE) {
            if (!JSObject::isExtensible(cx, obj, &extensible))
                return false;
            frozen = extensible ? 0 : 1;
        }
        if (!xdr->codeUint32(&frozen))
            return false;
        if (mode == XDR_DECODE && frozen == 1) {
            if (!JSObject::freeze(cx, obj))
                return false;
        }
    }

    if (isArray) {
        uint32_t copyOnWrite;
        if (mode == XDR_ENCODE)
            copyOnWrite = obj->denseElementsAreCopyOnWrite();
        if (!xdr->codeUint32(&copyOnWrite))
            return false;
        if (mode == XDR_DECODE && copyOnWrite) {
            if (!ObjectElements::MakeElementsCopyOnWrite(cx, obj))
                return false;
        }
    }

    return true;
}

template bool
js::XDRObjectLiteral(XDRState<XDR_ENCODE> *xdr, MutableHandleObject obj);

template bool
js::XDRObjectLiteral(XDRState<XDR_DECODE> *xdr, MutableHandleObject obj);

JSObject *
js::CloneObjectLiteral(JSContext *cx, HandleObject parent, HandleObject srcObj)
{
    if (srcObj->getClass() == &JSObject::class_) {
        AllocKind kind = GetBackgroundAllocKind(GuessObjectGCKind(srcObj->numFixedSlots()));
        JS_ASSERT_IF(srcObj->isTenured(), kind == srcObj->tenuredGetAllocKind());

        JSObject *proto = cx->global()->getOrCreateObjectPrototype(cx);
        if (!proto)
            return nullptr;
        Rooted<TypeObject*> typeObj(cx, cx->getNewType(&JSObject::class_, TaggedProto(proto)));
        if (!typeObj)
            return nullptr;

        RootedShape shape(cx, srcObj->lastProperty());
        return NewReshapedObject(cx, typeObj, parent, kind, shape);
    }

    JS_ASSERT(srcObj->is<ArrayObject>());
    JS_ASSERT(srcObj->denseElementsAreCopyOnWrite());
    JS_ASSERT(srcObj->getElementsHeader()->ownerObject() == srcObj);

    size_t length = srcObj->as<ArrayObject>().length();
    RootedObject res(cx, NewDenseAllocatedArray(cx, length, nullptr, MaybeSingletonObject));
    if (!res)
        return nullptr;

    RootedId id(cx);
    RootedValue value(cx);
    for (size_t i = 0; i < length; i++) {
        // The only markable values in copy on write arrays are atoms, which
        // can be freely copied between compartments.
        value = srcObj->getDenseElement(i);
        JS_ASSERT_IF(value.isMarkable(),
                     cx->runtime()->isAtomsZone(value.toGCThing()->tenuredZone()));

        id = INT_TO_JSID(i);
        if (!JSObject::defineGeneric(cx, res, id, value, nullptr, nullptr, JSPROP_ENUMERATE))
            return nullptr;
    }

    if (!ObjectElements::MakeElementsCopyOnWrite(cx, res))
        return nullptr;

    return res;
}

struct JSObject::TradeGutsReserved {
    Vector<Value> avals;
    Vector<Value> bvals;
    int newafixed;
    int newbfixed;
    RootedShape newashape;
    RootedShape newbshape;
    HeapSlot *newaslots;
    HeapSlot *newbslots;

    explicit TradeGutsReserved(JSContext *cx)
        : avals(cx), bvals(cx),
          newafixed(0), newbfixed(0),
          newashape(cx), newbshape(cx),
          newaslots(nullptr), newbslots(nullptr)
    {}

    ~TradeGutsReserved()
    {
        js_free(newaslots);
        js_free(newbslots);
    }
};

bool
JSObject::ReserveForTradeGuts(JSContext *cx, JSObject *aArg, JSObject *bArg,
                              TradeGutsReserved &reserved)
{
    /*
     * Avoid GC in here to avoid confusing the tracing code with our
     * intermediate state.
     */
    AutoSuppressGC suppress(cx);

    RootedObject a(cx, aArg);
    RootedObject b(cx, bArg);
    JS_ASSERT(a->compartment() == b->compartment());
    AutoCompartment ac(cx, a);

    /*
     * When performing multiple swaps between objects which may have different
     * numbers of fixed slots, we reserve all space ahead of time so that the
     * swaps can be performed infallibly.
     */

    /*
     * Swap prototypes and classes on the two objects, so that TradeGuts can
     * preserve the types of the two objects.
     */
    const Class *aClass = a->getClass();
    const Class *bClass = b->getClass();
    Rooted<TaggedProto> aProto(cx, a->getTaggedProto());
    Rooted<TaggedProto> bProto(cx, b->getTaggedProto());
    bool success;
    if (!SetClassAndProto(cx, a, bClass, bProto, &success) || !success)
        return false;
    if (!SetClassAndProto(cx, b, aClass, aProto, &success) || !success)
        return false;

    if (a->tenuredSizeOfThis() == b->tenuredSizeOfThis())
        return true;

    /*
     * If either object is native, it needs a new shape to preserve the
     * invariant that objects with the same shape have the same number of
     * inline slots. The fixed slots will be updated in place during TradeGuts.
     * Non-native objects need to be reshaped according to the new count.
     */
    if (a->isNative()) {
        if (!a->generateOwnShape(cx))
            return false;
    } else {
        reserved.newbshape = EmptyShape::getInitialShape(cx, aClass, aProto, a->getParent(), a->getMetadata(),
                                                         b->tenuredGetAllocKind());
        if (!reserved.newbshape)
            return false;
    }
    if (b->isNative()) {
        if (!b->generateOwnShape(cx))
            return false;
    } else {
        reserved.newashape = EmptyShape::getInitialShape(cx, bClass, bProto, b->getParent(), b->getMetadata(),
                                                         a->tenuredGetAllocKind());
        if (!reserved.newashape)
            return false;
    }

    /* The avals/bvals vectors hold all original values from the objects. */

    if (!reserved.avals.reserve(a->slotSpan()))
        return false;
    if (!reserved.bvals.reserve(b->slotSpan()))
        return false;

    /*
     * The newafixed/newbfixed hold the number of fixed slots in the objects
     * after the swap. Adjust these counts according to whether the objects
     * use their last fixed slot for storing private data.
     */

    reserved.newafixed = a->numFixedSlots();
    reserved.newbfixed = b->numFixedSlots();

    if (aClass->hasPrivate()) {
        reserved.newafixed++;
        reserved.newbfixed--;
    }
    if (bClass->hasPrivate()) {
        reserved.newbfixed++;
        reserved.newafixed--;
    }

    JS_ASSERT(reserved.newafixed >= 0);
    JS_ASSERT(reserved.newbfixed >= 0);

    /*
     * The newaslots/newbslots arrays hold any dynamic slots for the objects
     * if they do not have enough fixed slots to accomodate the slots in the
     * other object.
     */

    unsigned adynamic = dynamicSlotsCount(reserved.newafixed, b->slotSpan(), b->getClass());
    unsigned bdynamic = dynamicSlotsCount(reserved.newbfixed, a->slotSpan(), a->getClass());

    if (adynamic) {
        reserved.newaslots = a->pod_malloc<HeapSlot>(adynamic);
        if (!reserved.newaslots)
            return false;
        Debug_SetSlotRangeToCrashOnTouch(reserved.newaslots, adynamic);
    }
    if (bdynamic) {
        reserved.newbslots = b->pod_malloc<HeapSlot>(bdynamic);
        if (!reserved.newbslots)
            return false;
        Debug_SetSlotRangeToCrashOnTouch(reserved.newbslots, bdynamic);
    }

    return true;
}

void
JSObject::TradeGuts(JSContext *cx, JSObject *a, JSObject *b, TradeGutsReserved &reserved)
{
    JS_ASSERT(a->compartment() == b->compartment());
    JS_ASSERT(a->is<JSFunction>() == b->is<JSFunction>());

    /*
     * Neither object may be in the nursery, but ensure we update any embedded
     * nursery pointers in either object.
     */
#ifdef JSGC_GENERATIONAL
    JS_ASSERT(!IsInsideNursery(a) && !IsInsideNursery(b));
    cx->runtime()->gc.storeBuffer.putWholeCellFromMainThread(a);
    cx->runtime()->gc.storeBuffer.putWholeCellFromMainThread(b);
#endif
    JS::AutoCheckCannotGC nogc;

    /*
     * Swap the object's types, to restore their initial type information.
     * The prototypes and classes of the objects were swapped in ReserveForTradeGuts.
     */
    TypeObject *tmp = a->type_;
    a->type_ = b->type_;
    b->type_ = tmp;

    /* Don't try to swap a JSFunction for a plain function JSObject. */
    JS_ASSERT_IF(a->is<JSFunction>(), a->tenuredSizeOfThis() == b->tenuredSizeOfThis());

    /*
     * Regexp guts are more complicated -- we would need to migrate the
     * refcounted JIT code blob for them across compartments instead of just
     * swapping guts.
     */
    JS_ASSERT(!a->is<RegExpObject>() && !b->is<RegExpObject>());

    /* Arrays can use their fixed storage for elements. */
    JS_ASSERT(!a->is<ArrayObject>() && !b->is<ArrayObject>());

    /*
     * Callers should not try to swap ArrayBuffer objects,
     * these use a different slot representation from other objects.
     */
    JS_ASSERT(!a->is<ArrayBufferObject>() && !b->is<ArrayBufferObject>());

    /* Trade the guts of the objects. */
    const size_t size = a->tenuredSizeOfThis();
    if (size == b->tenuredSizeOfThis()) {
        /*
         * If the objects are the same size, then we make no assumptions about
         * whether they have dynamically allocated slots and instead just copy
         * them over wholesale.
         */
        char tmp[mozilla::tl::Max<sizeof(JSFunction), sizeof(JSObject_Slots16)>::value];
        JS_ASSERT(size <= sizeof(tmp));

        js_memcpy(tmp, a, size);
        js_memcpy(a, b, size);
        js_memcpy(b, tmp, size);
    } else {
        /*
         * If the objects are of differing sizes, use the space we reserved
         * earlier to save the slots from each object and then copy them into
         * the new layout for the other object.
         */

        uint32_t acap = a->slotSpan();
        uint32_t bcap = b->slotSpan();

        for (size_t i = 0; i < acap; i++)
            reserved.avals.infallibleAppend(a->getSlot(i));

        for (size_t i = 0; i < bcap; i++)
            reserved.bvals.infallibleAppend(b->getSlot(i));

        /* Done with the dynamic slots. */
        if (a->hasDynamicSlots())
            js_free(a->slots);
        if (b->hasDynamicSlots())
            js_free(b->slots);

        void *apriv = a->hasPrivate() ? a->getPrivate() : nullptr;
        void *bpriv = b->hasPrivate() ? b->getPrivate() : nullptr;

        char tmp[sizeof(JSObject)];
        js_memcpy(&tmp, a, sizeof tmp);
        js_memcpy(a, b, sizeof tmp);
        js_memcpy(b, &tmp, sizeof tmp);

        if (a->isNative())
            a->shape_->setNumFixedSlots(reserved.newafixed);
        else
            a->shape_ = reserved.newashape;

        a->slots = reserved.newaslots;
        a->initSlotRange(0, reserved.bvals.begin(), bcap);
        if (a->hasPrivate())
            a->initPrivate(bpriv);

        if (b->isNative())
            b->shape_->setNumFixedSlots(reserved.newbfixed);
        else
            b->shape_ = reserved.newbshape;

        b->slots = reserved.newbslots;
        b->initSlotRange(0, reserved.avals.begin(), acap);
        if (b->hasPrivate())
            b->initPrivate(apriv);

        /* Make sure the destructor for reserved doesn't free the slots. */
        reserved.newaslots = nullptr;
        reserved.newbslots = nullptr;
    }

    if (a->inDictionaryMode())
        a->lastProperty()->listp = &a->shape_;
    if (b->inDictionaryMode())
        b->lastProperty()->listp = &b->shape_;

#ifdef JSGC_INCREMENTAL
    /*
     * We need a write barrier here. If |a| was marked and |b| was not, then
     * after the swap, |b|'s guts would never be marked. The write barrier
     * solves this.
     *
     * Normally write barriers happen before the write. However, that's not
     * necessary here because nothing is being destroyed. We're just swapping.
     * We don't do the barrier before TradeGuts because ReserveForTradeGuts
     * makes changes to the objects that might confuse the tracing code.
     */
    JS::Zone *zone = a->zone();
    if (zone->needsIncrementalBarrier()) {
        MarkChildren(zone->barrierTracer(), a);
        MarkChildren(zone->barrierTracer(), b);
    }
#endif
}

/* Use this method with extreme caution. It trades the guts of two objects. */
bool
JSObject::swap(JSContext *cx, HandleObject a, HandleObject b)
{
    // Ensure swap doesn't cause a finalizer to not be run.
    JS_ASSERT(IsBackgroundFinalized(a->tenuredGetAllocKind()) ==
              IsBackgroundFinalized(b->tenuredGetAllocKind()));
    JS_ASSERT(a->compartment() == b->compartment());

    unsigned r = NotifyGCPreSwap(a, b);

    TradeGutsReserved reserved(cx);
    if (!ReserveForTradeGuts(cx, a, b, reserved)) {
        NotifyGCPostSwap(b, a, r);
        return false;
    }
    TradeGuts(cx, a, b, reserved);

    NotifyGCPostSwap(a, b, r);
    return true;
}

static bool
DefineStandardSlot(JSContext *cx, HandleObject obj, JSProtoKey key, JSAtom *atom,
                   HandleValue v, uint32_t attrs, bool &named)
{
    RootedId id(cx, AtomToId(atom));

    if (key != JSProto_Null) {
        /*
         * Initializing an actual standard class on a global object. If the
         * property is not yet present, force it into a new one bound to a
         * reserved slot. Otherwise, go through the normal property path.
         */
        JS_ASSERT(obj->is<GlobalObject>());
        JS_ASSERT(obj->isNative());

        if (!obj->nativeLookup(cx, id)) {
            obj->as<GlobalObject>().setConstructorPropertySlot(key, v);

            uint32_t slot = GlobalObject::constructorPropertySlot(key);
            if (!JSObject::addProperty(cx, obj, id, JS_PropertyStub, JS_StrictPropertyStub, slot, attrs, 0))
                return false;

            named = true;
            return true;
        }
    }

    named = JSObject::defineGeneric(cx, obj, id,
                                    v, JS_PropertyStub, JS_StrictPropertyStub, attrs);
    return named;
}

static void
SetClassObject(JSObject *obj, JSProtoKey key, JSObject *cobj, JSObject *proto)
{
    JS_ASSERT(!obj->getParent());
    if (!obj->is<GlobalObject>())
        return;

    obj->as<GlobalObject>().setConstructor(key, ObjectOrNullValue(cobj));
    obj->as<GlobalObject>().setPrototype(key, ObjectOrNullValue(proto));
}

static void
ClearClassObject(JSObject *obj, JSProtoKey key)
{
    JS_ASSERT(!obj->getParent());
    if (!obj->is<GlobalObject>())
        return;

    obj->as<GlobalObject>().setConstructor(key, UndefinedValue());
    obj->as<GlobalObject>().setPrototype(key, UndefinedValue());
}

static JSObject *
DefineConstructorAndPrototype(JSContext *cx, HandleObject obj, JSProtoKey key, HandleAtom atom,
                              JSObject *protoProto, const Class *clasp,
                              Native constructor, unsigned nargs,
                              const JSPropertySpec *ps, const JSFunctionSpec *fs,
                              const JSPropertySpec *static_ps, const JSFunctionSpec *static_fs,
                              JSObject **ctorp, AllocKind ctorKind)
{
    /*
     * Create a prototype object for this class.
     *
     * FIXME: lazy standard (built-in) class initialization and even older
     * eager boostrapping code rely on all of these properties:
     *
     * 1. NewObject attempting to compute a default prototype object when
     *    passed null for proto; and
     *
     * 2. NewObject tolerating no default prototype (null proto slot value)
     *    due to this js_InitClass call coming from js_InitFunctionClass on an
     *    otherwise-uninitialized global.
     *
     * 3. NewObject allocating a JSFunction-sized GC-thing when clasp is
     *    &JSFunction::class_, not a JSObject-sized (smaller) GC-thing.
     *
     * The JS_NewObjectForGivenProto and JS_NewObject APIs also allow clasp to
     * be &JSFunction::class_ (we could break compatibility easily). But
     * fixing (3) is not enough without addressing the bootstrapping dependency
     * on (1) and (2).
     */

    /*
     * Create the prototype object.  (GlobalObject::createBlankPrototype isn't
     * used because it parents the prototype object to the global and because
     * it uses WithProto::Given.  FIXME: Undo dependencies on this parentage
     * [which already needs to happen for bug 638316], figure out nicer
     * semantics for null-protoProto, and use createBlankPrototype.)
     */
    RootedObject proto(cx, NewObjectWithClassProto(cx, clasp, protoProto, obj, SingletonObject));
    if (!proto)
        return nullptr;

    /* After this point, control must exit via label bad or out. */
    RootedObject ctor(cx);
    bool named = false;
    bool cached = false;
    if (!constructor) {
        /*
         * Lacking a constructor, name the prototype (e.g., Math) unless this
         * class (a) is anonymous, i.e. for internal use only; (b) the class
         * of obj (the global object) is has a reserved slot indexed by key;
         * and (c) key is not the null key.
         */
        if (!(clasp->flags & JSCLASS_IS_ANONYMOUS) || !obj->is<GlobalObject>() ||
            key == JSProto_Null)
        {
            uint32_t attrs = (clasp->flags & JSCLASS_IS_ANONYMOUS)
                           ? JSPROP_READONLY | JSPROP_PERMANENT
                           : 0;
            RootedValue value(cx, ObjectValue(*proto));
            if (!DefineStandardSlot(cx, obj, key, atom, value, attrs, named))
                goto bad;
        }

        ctor = proto;
    } else {
        /*
         * Create the constructor, not using GlobalObject::createConstructor
         * because the constructor currently must have |obj| as its parent.
         * (FIXME: remove this dependency on the exact identity of the parent,
         * perhaps as part of bug 638316.)
         */
        RootedFunction fun(cx, NewFunction(cx, js::NullPtr(), constructor, nargs,
                                           JSFunction::NATIVE_CTOR, obj, atom, ctorKind));
        if (!fun)
            goto bad;

        /*
         * Set the class object early for standard class constructors. Type
         * inference may need to access these, and js::GetBuiltinPrototype will
         * fail if it tries to do a reentrant reconstruction of the class.
         */
        if (key != JSProto_Null) {
            SetClassObject(obj, key, fun, proto);
            cached = true;
        }

        RootedValue value(cx, ObjectValue(*fun));
        if (!DefineStandardSlot(cx, obj, key, atom, value, 0, named))
            goto bad;

        /*
         * Optionally construct the prototype object, before the class has
         * been fully initialized.  Allow the ctor to replace proto with a
         * different object, as is done for operator new.
         */
        ctor = fun;
        if (!LinkConstructorAndPrototype(cx, ctor, proto))
            goto bad;

        /* Bootstrap Function.prototype (see also JS_InitStandardClasses). */
        Rooted<TaggedProto> tagged(cx, TaggedProto(proto));
        if (ctor->getClass() == clasp && !ctor->splicePrototype(cx, clasp, tagged))
            goto bad;
    }

    if (!DefinePropertiesAndFunctions(cx, proto, ps, fs) ||
        (ctor != proto && !DefinePropertiesAndFunctions(cx, ctor, static_ps, static_fs)))
    {
        goto bad;
    }

    /* If this is a standard class, cache its prototype. */
    if (!cached && key != JSProto_Null)
        SetClassObject(obj, key, ctor, proto);

    if (ctorp)
        *ctorp = ctor;
    return proto;

bad:
    if (named) {
        bool succeeded;
        RootedId id(cx, AtomToId(atom));
        JSObject::deleteGeneric(cx, obj, id, &succeeded);
    }
    if (cached)
        ClearClassObject(obj, key);
    return nullptr;
}

JSObject *
js_InitClass(JSContext *cx, HandleObject obj, JSObject *protoProto_,
             const Class *clasp, Native constructor, unsigned nargs,
             const JSPropertySpec *ps, const JSFunctionSpec *fs,
             const JSPropertySpec *static_ps, const JSFunctionSpec *static_fs,
             JSObject **ctorp, AllocKind ctorKind)
{
    RootedObject protoProto(cx, protoProto_);

    /* Assert mandatory function pointer members. */
    JS_ASSERT(clasp->addProperty);
    JS_ASSERT(clasp->delProperty);
    JS_ASSERT(clasp->getProperty);
    JS_ASSERT(clasp->setProperty);
    JS_ASSERT(clasp->enumerate);
    JS_ASSERT(clasp->resolve);
    JS_ASSERT(clasp->convert);

    RootedAtom atom(cx, Atomize(cx, clasp->name, strlen(clasp->name)));
    if (!atom)
        return nullptr;

    /*
     * All instances of the class will inherit properties from the prototype
     * object we are about to create (in DefineConstructorAndPrototype), which
     * in turn will inherit from protoProto.
     *
     * When initializing a standard class (other than Object), if protoProto is
     * null, default to Object.prototype. The engine's internal uses of
     * js_InitClass depend on this nicety.
     */
    JSProtoKey key = JSCLASS_CACHED_PROTO_KEY(clasp);
    if (key != JSProto_Null &&
        !protoProto &&
        !GetBuiltinPrototype(cx, JSProto_Object, &protoProto))
    {
        return nullptr;
    }

    return DefineConstructorAndPrototype(cx, obj, key, atom, protoProto, clasp, constructor, nargs,
                                         ps, fs, static_ps, static_fs, ctorp, ctorKind);
}

/* static */ inline bool
JSObject::updateSlotsForSpan(ThreadSafeContext *cx,
                             HandleObject obj, size_t oldSpan, size_t newSpan)
{
    JS_ASSERT(cx->isThreadLocal(obj));
    JS_ASSERT(oldSpan != newSpan);

    size_t oldCount = dynamicSlotsCount(obj->numFixedSlots(), oldSpan, obj->getClass());
    size_t newCount = dynamicSlotsCount(obj->numFixedSlots(), newSpan, obj->getClass());

    if (oldSpan < newSpan) {
        if (oldCount < newCount && !JSObject::growSlots(cx, obj, oldCount, newCount))
            return false;

        if (newSpan == oldSpan + 1)
            obj->initSlotUnchecked(oldSpan, UndefinedValue());
        else
            obj->initializeSlotRange(oldSpan, newSpan - oldSpan);
    } else {
        /* Trigger write barriers on the old slots before reallocating. */
        obj->prepareSlotRangeForOverwrite(newSpan, oldSpan);
        obj->invalidateSlotRange(newSpan, oldSpan - newSpan);

        if (oldCount > newCount)
            JSObject::shrinkSlots(cx, obj, oldCount, newCount);
    }

    return true;
}

/* static */ bool
JSObject::setLastProperty(ThreadSafeContext *cx, HandleObject obj, HandleShape shape)
{
    JS_ASSERT(cx->isThreadLocal(obj));
    JS_ASSERT(!obj->inDictionaryMode());
    JS_ASSERT(!shape->inDictionary());
    JS_ASSERT(shape->compartment() == obj->compartment());
    JS_ASSERT(shape->numFixedSlots() == obj->numFixedSlots());

    size_t oldSpan = obj->lastProperty()->slotSpan();
    size_t newSpan = shape->slotSpan();

    if (oldSpan == newSpan) {
        obj->shape_ = shape;
        return true;
    }

    if (!updateSlotsForSpan(cx, obj, oldSpan, newSpan))
        return false;

    obj->shape_ = shape;
    return true;
}

/* static */ bool
JSObject::setSlotSpan(ThreadSafeContext *cx, HandleObject obj, uint32_t span)
{
    JS_ASSERT(cx->isThreadLocal(obj));
    JS_ASSERT(obj->inDictionaryMode());

    size_t oldSpan = obj->lastProperty()->base()->slotSpan();
    if (oldSpan == span)
        return true;

    if (!JSObject::updateSlotsForSpan(cx, obj, oldSpan, span))
        return false;

    obj->lastProperty()->base()->setSlotSpan(span);
    return true;
}

// This will not run the garbage collector.  If a nursery cannot accomodate the slot array
// an attempt will be made to place the array in the tenured area.
static HeapSlot *
AllocateSlots(ThreadSafeContext *cx, JSObject *obj, uint32_t nslots)
{
#ifdef JSGC_GENERATIONAL
    if (cx->isJSContext())
        return cx->asJSContext()->runtime()->gc.nursery.allocateSlots(obj, nslots);
#endif
#ifdef JSGC_FJGENERATIONAL
    if (cx->isForkJoinContext())
        return cx->asForkJoinContext()->nursery().allocateSlots(obj, nslots);
#endif
    return obj->pod_malloc<HeapSlot>(nslots);
}

// This will not run the garbage collector.  If a nursery cannot accomodate the slot array
// an attempt will be made to place the array in the tenured area.
//
// If this returns null then the old slots will be left alone.
static HeapSlot *
ReallocateSlots(ThreadSafeContext *cx, JSObject *obj, HeapSlot *oldSlots,
                uint32_t oldCount, uint32_t newCount)
{
#ifdef JSGC_GENERATIONAL
    if (cx->isJSContext()) {
        return cx->asJSContext()->runtime()->gc.nursery.reallocateSlots(obj, oldSlots,
                                                                        oldCount, newCount);
    }
#endif
#ifdef JSGC_FJGENERATIONAL
    if (cx->isForkJoinContext()) {
        return cx->asForkJoinContext()->nursery().reallocateSlots(obj, oldSlots,
                                                                  oldCount, newCount);
    }
#endif
    return obj->pod_realloc<HeapSlot>(oldSlots, oldCount, newCount);
}

/* static */ bool
JSObject::growSlots(ThreadSafeContext *cx, HandleObject obj, uint32_t oldCount, uint32_t newCount)
{
    JS_ASSERT(cx->isThreadLocal(obj));
    JS_ASSERT(newCount > oldCount);
    JS_ASSERT_IF(!obj->is<ArrayObject>(), newCount >= SLOT_CAPACITY_MIN);

    /*
     * Slot capacities are determined by the span of allocated objects. Due to
     * the limited number of bits to store shape slots, object growth is
     * throttled well before the slot capacity can overflow.
     */
    JS_ASSERT(newCount < NELEMENTS_LIMIT);

    /*
     * If we are allocating slots for an object whose type is always created
     * by calling 'new' on a particular script, bump the GC kind for that
     * type to give these objects a larger number of fixed slots when future
     * objects are constructed.
     */
    if (!obj->hasLazyType() && !oldCount && obj->type()->newScript()) {
        JSObject *oldTemplate = obj->type()->newScript()->templateObject;
        gc::AllocKind kind = gc::GetGCObjectFixedSlotsKind(oldTemplate->numFixedSlots());
        uint32_t newScriptSlots = gc::GetGCKindSlots(kind);
        if (newScriptSlots == obj->numFixedSlots() &&
            gc::TryIncrementAllocKind(&kind) &&
            cx->isJSContext())
        {
            JSContext *ncx = cx->asJSContext();
            AutoEnterAnalysis enter(ncx);

            Rooted<TypeObject*> typeObj(cx, obj->type());
            RootedShape shape(cx, oldTemplate->lastProperty());
            JSObject *reshapedObj = NewReshapedObject(ncx, typeObj, obj->getParent(), kind, shape,
                                                      MaybeSingletonObject);
            if (!reshapedObj)
                return false;

            typeObj->newScript()->templateObject = reshapedObj;
            typeObj->markStateChange(ncx);
        }
    }

    if (!oldCount) {
        obj->slots = AllocateSlots(cx, obj, newCount);
        if (!obj->slots)
            return false;
        Debug_SetSlotRangeToCrashOnTouch(obj->slots, newCount);
        return true;
    }

    HeapSlot *newslots = ReallocateSlots(cx, obj, obj->slots, oldCount, newCount);
    if (!newslots)
        return false;  /* Leave slots at its old size. */

    obj->slots = newslots;

    Debug_SetSlotRangeToCrashOnTouch(obj->slots + oldCount, newCount - oldCount);

    return true;
}

static void
FreeSlots(ThreadSafeContext *cx, HeapSlot *slots)
{
#ifdef JSGC_GENERATIONAL
    // Note: threads without a JSContext do not have access to GGC nursery allocated things.
    if (cx->isJSContext())
        return cx->asJSContext()->runtime()->gc.nursery.freeSlots(slots);
#endif
#ifdef JSGC_FJGENERATIONAL
    if (cx->isForkJoinContext())
        return cx->asForkJoinContext()->nursery().freeSlots(slots);
#endif
    js_free(slots);
}

/* static */ void
JSObject::shrinkSlots(ThreadSafeContext *cx, HandleObject obj, uint32_t oldCount, uint32_t newCount)
{
    JS_ASSERT(cx->isThreadLocal(obj));
    JS_ASSERT(newCount < oldCount);

    if (newCount == 0) {
        FreeSlots(cx, obj->slots);
        obj->slots = nullptr;
        return;
    }

    JS_ASSERT_IF(!obj->is<ArrayObject>(), newCount >= SLOT_CAPACITY_MIN);

    HeapSlot *newslots = ReallocateSlots(cx, obj, obj->slots, oldCount, newCount);
    if (!newslots)
        return;  /* Leave slots at its old size. */

    obj->slots = newslots;
}

/* static */ bool
JSObject::sparsifyDenseElement(ExclusiveContext *cx, HandleObject obj, uint32_t index)
{
    if (!obj->maybeCopyElementsForWrite(cx))
        return false;

    RootedValue value(cx, obj->getDenseElement(index));
    JS_ASSERT(!value.isMagic(JS_ELEMENTS_HOLE));

    JSObject::removeDenseElementForSparseIndex(cx, obj, index);

    uint32_t slot = obj->slotSpan();
    if (!obj->addDataProperty(cx, INT_TO_JSID(index), slot, JSPROP_ENUMERATE)) {
        obj->setDenseElement(index, value);
        return false;
    }

    JS_ASSERT(slot == obj->slotSpan() - 1);
    obj->initSlot(slot, value);

    return true;
}

/* static */ bool
JSObject::sparsifyDenseElements(js::ExclusiveContext *cx, HandleObject obj)
{
    if (!obj->maybeCopyElementsForWrite(cx))
        return false;

    uint32_t initialized = obj->getDenseInitializedLength();

    /* Create new properties with the value of non-hole dense elements. */
    for (uint32_t i = 0; i < initialized; i++) {
        if (obj->getDenseElement(i).isMagic(JS_ELEMENTS_HOLE))
            continue;

        if (!sparsifyDenseElement(cx, obj, i))
            return false;
    }

    if (initialized)
        obj->setDenseInitializedLength(0);

    /*
     * Reduce storage for dense elements which are now holes. Explicitly mark
     * the elements capacity as zero, so that any attempts to add dense
     * elements will be caught in ensureDenseElements.
     */
    if (obj->getDenseCapacity()) {
        obj->shrinkElements(cx, 0);
        obj->getElementsHeader()->capacity = 0;
    }

    return true;
}

bool
JSObject::willBeSparseElements(uint32_t requiredCapacity, uint32_t newElementsHint)
{
    JS_ASSERT(isNative());
    JS_ASSERT(requiredCapacity > MIN_SPARSE_INDEX);

    uint32_t cap = getDenseCapacity();
    JS_ASSERT(requiredCapacity >= cap);

    if (requiredCapacity >= NELEMENTS_LIMIT)
        return true;

    uint32_t minimalDenseCount = requiredCapacity / SPARSE_DENSITY_RATIO;
    if (newElementsHint >= minimalDenseCount)
        return false;
    minimalDenseCount -= newElementsHint;

    if (minimalDenseCount > cap)
        return true;

    uint32_t len = getDenseInitializedLength();
    const Value *elems = getDenseElements();
    for (uint32_t i = 0; i < len; i++) {
        if (!elems[i].isMagic(JS_ELEMENTS_HOLE) && !--minimalDenseCount)
            return false;
    }
    return true;
}

/* static */ JSObject::EnsureDenseResult
JSObject::maybeDensifySparseElements(js::ExclusiveContext *cx, HandleObject obj)
{
    /*
     * Wait until after the object goes into dictionary mode, which must happen
     * when sparsely packing any array with more than MIN_SPARSE_INDEX elements
     * (see PropertyTree::MAX_HEIGHT).
     */
    if (!obj->inDictionaryMode())
        return ED_SPARSE;

    /*
     * Only measure the number of indexed properties every log(n) times when
     * populating the object.
     */
    uint32_t slotSpan = obj->slotSpan();
    if (slotSpan != RoundUpPow2(slotSpan))
        return ED_SPARSE;

    /* Watch for conditions under which an object's elements cannot be dense. */
    if (!obj->nonProxyIsExtensible() || obj->watched())
        return ED_SPARSE;

    /*
     * The indexes in the object need to be sufficiently dense before they can
     * be converted to dense mode.
     */
    uint32_t numDenseElements = 0;
    uint32_t newInitializedLength = 0;

    RootedShape shape(cx, obj->lastProperty());
    while (!shape->isEmptyShape()) {
        uint32_t index;
        if (js_IdIsIndex(shape->propid(), &index)) {
            if (shape->attributes() == JSPROP_ENUMERATE &&
                shape->hasDefaultGetter() &&
                shape->hasDefaultSetter())
            {
                numDenseElements++;
                newInitializedLength = Max(newInitializedLength, index + 1);
            } else {
                /*
                 * For simplicity, only densify the object if all indexed
                 * properties can be converted to dense elements.
                 */
                return ED_SPARSE;
            }
        }
        shape = shape->previous();
    }

    if (numDenseElements * SPARSE_DENSITY_RATIO < newInitializedLength)
        return ED_SPARSE;

    if (newInitializedLength >= NELEMENTS_LIMIT)
        return ED_SPARSE;

    /*
     * This object meets all necessary restrictions, convert all indexed
     * properties into dense elements.
     */

    if (!obj->maybeCopyElementsForWrite(cx))
        return ED_FAILED;

    if (newInitializedLength > obj->getDenseCapacity()) {
        if (!obj->growElements(cx, newInitializedLength))
            return ED_FAILED;
    }

    obj->ensureDenseInitializedLength(cx, newInitializedLength, 0);

    RootedValue value(cx);

    shape = obj->lastProperty();
    while (!shape->isEmptyShape()) {
        jsid id = shape->propid();
        uint32_t index;
        if (js_IdIsIndex(id, &index)) {
            value = obj->getSlot(shape->slot());

            /*
             * When removing a property from a dictionary, the specified
             * property will be removed from the dictionary list and the
             * last property will then be changed due to reshaping the object.
             * Compute the next shape in the traverse, watching for such
             * removals from the list.
             */
            if (shape != obj->lastProperty()) {
                shape = shape->previous();
                if (!obj->removeProperty(cx, id))
                    return ED_FAILED;
            } else {
                if (!obj->removeProperty(cx, id))
                    return ED_FAILED;
                shape = obj->lastProperty();
            }

            obj->setDenseElement(index, value);
        } else {
            shape = shape->previous();
        }
    }

    /*
     * All indexed properties on the object are now dense, clear the indexed
     * flag so that we will not start using sparse indexes again if we need
     * to grow the object.
     */
    if (!obj->clearFlag(cx, BaseShape::INDEXED))
        return ED_FAILED;

    return ED_OK;
}

// This will not run the garbage collector.  If a nursery cannot accomodate the element array
// an attempt will be made to place the array in the tenured area.
static ObjectElements *
AllocateElements(ThreadSafeContext *cx, JSObject *obj, uint32_t nelems)
{
#ifdef JSGC_GENERATIONAL
    if (cx->isJSContext())
        return cx->asJSContext()->runtime()->gc.nursery.allocateElements(obj, nelems);
#endif
#ifdef JSGC_FJGENERATIONAL
    if (cx->isForkJoinContext())
        return cx->asForkJoinContext()->nursery().allocateElements(obj, nelems);
#endif

    return reinterpret_cast<js::ObjectElements *>(obj->pod_malloc<HeapSlot>(nelems));
}

// This will not run the garbage collector.  If a nursery cannot accomodate the element array
// an attempt will be made to place the array in the tenured area.
static ObjectElements *
ReallocateElements(ThreadSafeContext *cx, JSObject *obj, ObjectElements *oldHeader,
                   uint32_t oldCount, uint32_t newCount)
{
#ifdef JSGC_GENERATIONAL
    if (cx->isJSContext()) {
        return cx->asJSContext()->runtime()->gc.nursery.reallocateElements(obj, oldHeader,
                                                                           oldCount, newCount);
    }
#endif
#ifdef JSGC_FJGENERATIONAL
    if (cx->isForkJoinContext()) {
        return cx->asForkJoinContext()->nursery().reallocateElements(obj, oldHeader,
                                                                     oldCount, newCount);
    }
#endif

    return reinterpret_cast<js::ObjectElements *>(
            obj->pod_realloc<HeapSlot>(reinterpret_cast<HeapSlot *>(oldHeader),
                                       oldCount, newCount));
}

// Round up |reqAllocated| to a good size. Up to 1 Mebi (i.e. 1,048,576) the
// slot count is usually a power-of-two:
//
//   8, 16, 32, 64, ..., 256 Ki, 512 Ki, 1 Mi
//
// Beyond that, we use this formula:
//
//   count(n+1) = Math.ceil(count(n) * 1.125)
//
// where |count(n)| is the size of the nth bucket measured in MiSlots.
//
// These counts lets us add N elements to an array in amortized O(N) time.
// Having the second class means that for bigger arrays the constant factor is
// higher, but we waste less space.
//
// There is one exception to the above rule: for the power-of-two cases, if the
// chosen capacity would be 2/3 or more of the array's length, the chosen
// capacity is adjusted (up or down) to be equal to the array's length
// (assuming length is at least as large as the required capacity). This avoids
// the allocation of excess elements which are unlikely to be needed, either in
// this resizing or a subsequent one. The 2/3 factor is chosen so that
// exceptional resizings will at most triple the capacity, as opposed to the
// usual doubling.
//
/* static */ uint32_t
JSObject::goodAllocated(uint32_t reqAllocated, uint32_t length = 0)
{
    static const uint32_t Mebi = 1024 * 1024;

    // This table was generated with this JavaScript code and a small amount
    // subsequent reformatting:
    //
    //   for (let n = 1, i = 0; i < 57; i++) {
    //     print((n * 1024 * 1024) + ', ');
    //     n = Math.ceil(n * 1.125);
    //   }
    //   print('0');
    //
    // The final element is a sentinel value.
    static const uint32_t BigBuckets[] = {
        1048576, 2097152, 3145728, 4194304, 5242880, 6291456, 7340032, 8388608,
        9437184, 11534336, 13631488, 15728640, 17825792, 20971520, 24117248,
        27262976, 31457280, 35651584, 40894464, 46137344, 52428800, 59768832,
        68157440, 77594624, 88080384, 99614720, 112197632, 126877696,
        143654912, 162529280, 183500800, 206569472, 232783872, 262144000,
        295698432, 333447168, 375390208, 422576128, 476053504, 535822336,
        602931200, 678428672, 763363328, 858783744, 966787072, 1088421888,
        1224736768, 1377828864, 1550843904, 1744830464, 1962934272, 2208301056,
        2485125120, 2796552192, 3146776576, 3541041152, 3984588800, 0
    };

    // This code relies very much on |goodAllocated| being a uint32_t.
    uint32_t goodAllocated = reqAllocated;
    if (goodAllocated < Mebi) {
        goodAllocated = RoundUpPow2(goodAllocated);

        // Look for the abovementioned exception.
        uint32_t goodCapacity = goodAllocated - ObjectElements::VALUES_PER_HEADER;
        uint32_t reqCapacity = reqAllocated - ObjectElements::VALUES_PER_HEADER;
        if (length >= reqCapacity && goodCapacity > (length / 3) * 2)
            goodAllocated = length + ObjectElements::VALUES_PER_HEADER;

        if (goodAllocated < JSObject::SLOT_CAPACITY_MIN)
            goodAllocated = JSObject::SLOT_CAPACITY_MIN;

    } else {
        uint32_t i = 0;
        while (true) {
            uint32_t b = BigBuckets[i++];
            if (b >= goodAllocated) {
                // Found the first bucket greater than or equal to
                // |goodAllocated|.
                goodAllocated = b;
                break;
            } else if (b == 0) {
                // Hit the end; return the maximum possible goodAllocated.
                goodAllocated = 0xffffffff;
                break;
            }
        }
    }

    return goodAllocated;
}

bool
JSObject::growElements(ThreadSafeContext *cx, uint32_t reqCapacity)
{
    JS_ASSERT(nonProxyIsExtensible());
    JS_ASSERT(canHaveNonEmptyElements());
    if (denseElementsAreCopyOnWrite())
        MOZ_CRASH();

    uint32_t oldCapacity = getDenseCapacity();
    JS_ASSERT(oldCapacity < reqCapacity);

    using mozilla::CheckedInt;

    CheckedInt<uint32_t> checkedOldAllocated =
        CheckedInt<uint32_t>(oldCapacity) + ObjectElements::VALUES_PER_HEADER;
    CheckedInt<uint32_t> checkedReqAllocated =
        CheckedInt<uint32_t>(reqCapacity) + ObjectElements::VALUES_PER_HEADER;
    if (!checkedOldAllocated.isValid() || !checkedReqAllocated.isValid())
        return false;

    uint32_t reqAllocated = checkedReqAllocated.value();
    uint32_t oldAllocated = checkedOldAllocated.value();

    uint32_t newAllocated;
    if (is<ArrayObject>() && !as<ArrayObject>().lengthIsWritable()) {
        JS_ASSERT(reqCapacity <= as<ArrayObject>().length());
        // Preserve the |capacity <= length| invariant for arrays with
        // non-writable length.  See also js::ArraySetLength which initially
        // enforces this requirement.
        newAllocated = reqAllocated;
    } else {
        newAllocated = goodAllocated(reqAllocated, getElementsHeader()->length);
    }

    uint32_t newCapacity = newAllocated - ObjectElements::VALUES_PER_HEADER;
    JS_ASSERT(newCapacity > oldCapacity && newCapacity >= reqCapacity);

    // Don't let nelements get close to wrapping around uint32_t.
    if (newCapacity >= NELEMENTS_LIMIT)
        return false;

    uint32_t initlen = getDenseInitializedLength();

    ObjectElements *newheader;
    if (hasDynamicElements()) {
        newheader = ReallocateElements(cx, this, getElementsHeader(), oldAllocated, newAllocated);
        if (!newheader)
            return false;   // Leave elements at its old size.
    } else {
        newheader = AllocateElements(cx, this, newAllocated);
        if (!newheader)
            return false;   // Leave elements at its old size.
        js_memcpy(newheader, getElementsHeader(),
                  (ObjectElements::VALUES_PER_HEADER + initlen) * sizeof(Value));
    }

    newheader->capacity = newCapacity;
    elements = newheader->elements();

    Debug_SetSlotRangeToCrashOnTouch(elements + initlen, newCapacity - initlen);

    return true;
}

void
JSObject::shrinkElements(ThreadSafeContext *cx, uint32_t reqCapacity)
{
    JS_ASSERT(cx->isThreadLocal(this));
    JS_ASSERT(canHaveNonEmptyElements());
    if (denseElementsAreCopyOnWrite())
        MOZ_CRASH();

    if (!hasDynamicElements())
        return;

    uint32_t oldCapacity = getDenseCapacity();
    JS_ASSERT(reqCapacity < oldCapacity);

    uint32_t oldAllocated = oldCapacity + ObjectElements::VALUES_PER_HEADER;
    uint32_t reqAllocated = reqCapacity + ObjectElements::VALUES_PER_HEADER;
    uint32_t newAllocated = goodAllocated(reqAllocated);
    if (newAllocated == oldAllocated)
        return;  // Leave elements at its old size.

    MOZ_ASSERT(newAllocated > ObjectElements::VALUES_PER_HEADER);
    uint32_t newCapacity = newAllocated - ObjectElements::VALUES_PER_HEADER;

    ObjectElements *newheader = ReallocateElements(cx, this, getElementsHeader(),
                                                   oldAllocated, newAllocated);
    if (!newheader) {
        cx->recoverFromOutOfMemory();
        return;  // Leave elements at its old size.
    }

    newheader->capacity = newCapacity;
    elements = newheader->elements();
}

/* static */ bool
JSObject::CopyElementsForWrite(ThreadSafeContext *cx, JSObject *obj)
{
    JS_ASSERT(obj->denseElementsAreCopyOnWrite());

    // The original owner of a COW elements array should never be modified.
    JS_ASSERT(obj->getElementsHeader()->ownerObject() != obj);

    uint32_t initlen = obj->getDenseInitializedLength();
    uint32_t allocated = initlen + ObjectElements::VALUES_PER_HEADER;
    uint32_t newAllocated = goodAllocated(allocated);

    uint32_t newCapacity = newAllocated - ObjectElements::VALUES_PER_HEADER;

    if (newCapacity >= NELEMENTS_LIMIT)
        return false;

    JSObject::writeBarrierPre(obj->getElementsHeader()->ownerObject());

    ObjectElements *newheader = AllocateElements(cx, obj, newAllocated);
    if (!newheader)
        return false;
    js_memcpy(newheader, obj->getElementsHeader(),
              (ObjectElements::VALUES_PER_HEADER + initlen) * sizeof(Value));

    newheader->capacity = newCapacity;
    newheader->clearCopyOnWrite();
    obj->elements = newheader->elements();

    Debug_SetSlotRangeToCrashOnTouch(obj->elements + initlen, newCapacity - initlen);

    return true;
}

bool
js::SetClassAndProto(JSContext *cx, HandleObject obj,
                     const Class *clasp, Handle<js::TaggedProto> proto,
                     bool *succeeded)
{
    /*
     * Regenerate shapes for all of the scopes along the old prototype chain,
     * in case any entries were filled by looking up through obj. Stop when a
     * non-native object is found, prototype lookups will not be cached across
     * these.
     *
     * How this shape change is done is very delicate; the change can be made
     * either by marking the object's prototype as uncacheable (such that the
     * property cache and JIT'ed ICs cannot assume the shape determines the
     * prototype) or by just generating a new shape for the object. Choosing
     * the former is bad if the object is on the prototype chain of other
     * objects, as the uncacheable prototype can inhibit iterator caches on
     * those objects and slow down prototype accesses. Choosing the latter is
     * bad if there are many similar objects to this one which will have their
     * prototype mutated, as the generateOwnShape forces the object into
     * dictionary mode and similar property lineages will be repeatedly cloned.
     *
     * :XXX: bug 707717 make this code less brittle.
     */
    *succeeded = false;
    RootedObject oldproto(cx, obj);
    while (oldproto && oldproto->isNative()) {
        if (oldproto->hasSingletonType()) {
            if (!oldproto->generateOwnShape(cx))
                return false;
        } else {
            if (!oldproto->setUncacheableProto(cx))
                return false;
        }
        oldproto = oldproto->getProto();
    }

    if (obj->hasSingletonType()) {
        /*
         * Just splice the prototype, but mark the properties as unknown for
         * consistent behavior.
         */
        if (!obj->splicePrototype(cx, clasp, proto))
            return false;
        MarkTypeObjectUnknownProperties(cx, obj->type());
        *succeeded = true;
        return true;
    }

    if (proto.isObject()) {
        RootedObject protoObj(cx, proto.toObject());
        if (!JSObject::setNewTypeUnknown(cx, clasp, protoObj))
            return false;
    }

    TypeObject *type = cx->getNewType(clasp, proto);
    if (!type)
        return false;

    /*
     * Setting __proto__ on an object that has escaped and may be referenced by
     * other heap objects can only be done if the properties of both objects
     * are unknown. Type sets containing this object will contain the original
     * type but not the new type of the object, so we need to go and scan the
     * entire compartment for type sets which have these objects and mark them
     * as containing generic objects.
     */
    MarkTypeObjectUnknownProperties(cx, obj->type(), true);
    MarkTypeObjectUnknownProperties(cx, type, true);

    obj->setType(type);

    *succeeded = true;
    return true;
}

static bool
MaybeResolveConstructor(ExclusiveContext *cxArg, Handle<GlobalObject*> global, JSProtoKey key)
{
    if (global->isStandardClassResolved(key))
        return true;
    if (!cxArg->shouldBeJSContext())
        return false;

    JSContext *cx = cxArg->asJSContext();
    return GlobalObject::resolveConstructor(cx, global, key);
}

bool
js::GetBuiltinConstructor(ExclusiveContext *cx, JSProtoKey key, MutableHandleObject objp)
{
    MOZ_ASSERT(key != JSProto_Null);
    Rooted<GlobalObject*> global(cx, cx->global());
    if (!MaybeResolveConstructor(cx, global, key))
        return false;

    objp.set(&global->getConstructor(key).toObject());
    return true;
}

bool
js::GetBuiltinPrototype(ExclusiveContext *cx, JSProtoKey key, MutableHandleObject protop)
{
    MOZ_ASSERT(key != JSProto_Null);
    Rooted<GlobalObject*> global(cx, cx->global());
    if (!MaybeResolveConstructor(cx, global, key))
        return false;

    protop.set(&global->getPrototype(key).toObject());
    return true;
}

static bool
IsStandardPrototype(JSObject *obj, JSProtoKey key)
{
    GlobalObject &global = obj->global();
    Value v = global.getPrototype(key);
    return v.isObject() && obj == &v.toObject();
}

JSProtoKey
JS::IdentifyStandardInstance(JSObject *obj)
{
    // Note: The prototype shares its JSClass with instances.
    JS_ASSERT(!obj->is<CrossCompartmentWrapperObject>());
    JSProtoKey key = StandardProtoKeyOrNull(obj);
    if (key != JSProto_Null && !IsStandardPrototype(obj, key))
        return key;
    return JSProto_Null;
}

JSProtoKey
JS::IdentifyStandardPrototype(JSObject *obj)
{
    // Note: The prototype shares its JSClass with instances.
    JS_ASSERT(!obj->is<CrossCompartmentWrapperObject>());
    JSProtoKey key = StandardProtoKeyOrNull(obj);
    if (key != JSProto_Null && IsStandardPrototype(obj, key))
        return key;
    return JSProto_Null;
}

JSProtoKey
JS::IdentifyStandardInstanceOrPrototype(JSObject *obj)
{
    return StandardProtoKeyOrNull(obj);
}

JSProtoKey
JS::IdentifyStandardConstructor(JSObject *obj)
{
    // Note that NATIVE_CTOR does not imply that we are a standard constructor,
    // but the converse is true (at least until we start having self-hosted
    // constructors for standard classes). This lets us avoid a costly loop for
    // many functions (which, depending on the call site, may be the common case).
    if (!obj->is<JSFunction>() || !(obj->as<JSFunction>().flags() & JSFunction::NATIVE_CTOR))
        return JSProto_Null;

    GlobalObject &global = obj->global();
    for (size_t k = 0; k < JSProto_LIMIT; ++k) {
        JSProtoKey key = static_cast<JSProtoKey>(k);
        if (global.getConstructor(key) == ObjectValue(*obj))
            return key;
    }

    return JSProto_Null;
}

bool
js::FindClassObject(ExclusiveContext *cx, MutableHandleObject protop, const Class *clasp)
{
    JSProtoKey protoKey = ClassProtoKeyOrAnonymousOrNull(clasp);
    if (protoKey != JSProto_Null) {
        JS_ASSERT(JSProto_Null < protoKey);
        JS_ASSERT(protoKey < JSProto_LIMIT);
        return GetBuiltinConstructor(cx, protoKey, protop);
    }

    JSAtom *atom = Atomize(cx, clasp->name, strlen(clasp->name));
    if (!atom)
        return false;
    RootedId id(cx, AtomToId(atom));

    RootedObject pobj(cx);
    RootedShape shape(cx);
    if (!LookupNativeProperty(cx, cx->global(), id, &pobj, &shape))
        return false;
    RootedValue v(cx);
    if (shape && pobj->isNative()) {
        if (shape->hasSlot())
            v = pobj->nativeGetSlot(shape->slot());
    }
    if (v.isObject())
        protop.set(&v.toObject());
    return true;
}

bool
JSObject::isConstructor() const
{
    if (is<JSFunction>()) {
        const JSFunction &fun = as<JSFunction>();
        return fun.isNativeConstructor() || fun.isInterpretedConstructor();
    }
    return getClass()->construct != nullptr;
}

/* static */ bool
JSObject::allocSlot(ThreadSafeContext *cx, HandleObject obj, uint32_t *slotp)
{
    JS_ASSERT(cx->isThreadLocal(obj));

    uint32_t slot = obj->slotSpan();
    JS_ASSERT(slot >= JSSLOT_FREE(obj->getClass()));

    /*
     * If this object is in dictionary mode, try to pull a free slot from the
     * shape table's slot-number freelist.
     */
    if (obj->inDictionaryMode()) {
        ShapeTable &table = obj->lastProperty()->table();
        uint32_t last = table.freelist;
        if (last != SHAPE_INVALID_SLOT) {
#ifdef DEBUG
            JS_ASSERT(last < slot);
            uint32_t next = obj->getSlot(last).toPrivateUint32();
            JS_ASSERT_IF(next != SHAPE_INVALID_SLOT, next < slot);
#endif

            *slotp = last;

            const Value &vref = obj->getSlot(last);
            table.freelist = vref.toPrivateUint32();
            obj->setSlot(last, UndefinedValue());
            return true;
        }
    }

    if (slot >= SHAPE_MAXIMUM_SLOT) {
        js_ReportOutOfMemory(cx);
        return false;
    }

    *slotp = slot;

    if (obj->inDictionaryMode() && !setSlotSpan(cx, obj, slot + 1))
        return false;

    return true;
}

void
JSObject::freeSlot(uint32_t slot)
{
    JS_ASSERT(slot < slotSpan());

    if (inDictionaryMode()) {
        uint32_t &last = lastProperty()->table().freelist;

        /* Can't afford to check the whole freelist, but let's check the head. */
        JS_ASSERT_IF(last != SHAPE_INVALID_SLOT, last < slotSpan() && last != slot);

        /*
         * Place all freed slots other than reserved slots (bug 595230) on the
         * dictionary's free list.
         */
        if (JSSLOT_FREE(getClass()) <= slot) {
            JS_ASSERT_IF(last != SHAPE_INVALID_SLOT, last < slotSpan());
            setSlot(slot, PrivateUint32Value(last));
            last = slot;
            return;
        }
    }
    setSlot(slot, UndefinedValue());
}

static bool
PurgeProtoChain(ExclusiveContext *cx, JSObject *objArg, HandleId id)
{
    /* Root locally so we can re-assign. */
    RootedObject obj(cx, objArg);

    RootedShape shape(cx);
    while (obj) {
        /* Lookups will not be cached through non-native protos. */
        if (!obj->isNative())
            break;

        shape = obj->nativeLookup(cx, id);
        if (shape) {
            if (!obj->shadowingShapeChange(cx, *shape))
                return false;

            obj->shadowingShapeChange(cx, *shape);
            return true;
        }
        obj = obj->getProto();
    }

    return true;
}

static bool
PurgeScopeChainHelper(ExclusiveContext *cx, HandleObject objArg, HandleId id)
{
    /* Re-root locally so we can re-assign. */
    RootedObject obj(cx, objArg);

    JS_ASSERT(obj->isNative());
    JS_ASSERT(obj->isDelegate());

    /* Lookups on integer ids cannot be cached through prototypes. */
    if (JSID_IS_INT(id))
        return true;

    PurgeProtoChain(cx, obj->getProto(), id);

    /*
     * We must purge the scope chain only for Call objects as they are the only
     * kind of cacheable non-global object that can gain properties after outer
     * properties with the same names have been cached or traced. Call objects
     * may gain such properties via eval introducing new vars; see bug 490364.
     */
    if (obj->is<CallObject>()) {
        while ((obj = obj->enclosingScope()) != nullptr) {
            if (!PurgeProtoChain(cx, obj, id))
                return false;
        }
    }

    return true;
}

/*
 * PurgeScopeChain does nothing if obj is not itself a prototype or parent
 * scope, else it reshapes the scope and prototype chains it links. It calls
 * PurgeScopeChainHelper, which asserts that obj is flagged as a delegate
 * (i.e., obj has ever been on a prototype or parent chain).
 */
static inline bool
PurgeScopeChain(ExclusiveContext *cx, JS::HandleObject obj, JS::HandleId id)
{
    if (obj->isDelegate())
        return PurgeScopeChainHelper(cx, obj, id);
    return true;
}

bool
baseops::DefineGeneric(ExclusiveContext *cx, HandleObject obj, HandleId id, HandleValue value,
                       PropertyOp getter, StrictPropertyOp setter, unsigned attrs)
{
    return DefineNativeProperty(cx, obj, id, value, getter, setter, attrs);
}

/* static */ bool
JSObject::defineGeneric(ExclusiveContext *cx, HandleObject obj,
                        HandleId id, HandleValue value,
                        JSPropertyOp getter, JSStrictPropertyOp setter, unsigned attrs)
{
    JS_ASSERT(!(attrs & JSPROP_NATIVE_ACCESSORS));
    js::DefineGenericOp op = obj->getOps()->defineGeneric;
    if (op) {
        if (!cx->shouldBeJSContext())
            return false;
        return op(cx->asJSContext(), obj, id, value, getter, setter, attrs);
    }
    return baseops::DefineGeneric(cx, obj, id, value, getter, setter, attrs);
}

/* static */ bool
JSObject::defineProperty(ExclusiveContext *cx, HandleObject obj,
                         PropertyName *name, HandleValue value,
                         JSPropertyOp getter, JSStrictPropertyOp setter, unsigned attrs)
{
    RootedId id(cx, NameToId(name));
    return defineGeneric(cx, obj, id, value, getter, setter, attrs);
}

bool
baseops::DefineElement(ExclusiveContext *cx, HandleObject obj, uint32_t index, HandleValue value,
                       PropertyOp getter, StrictPropertyOp setter, unsigned attrs)
{
    RootedId id(cx);
    if (index <= JSID_INT_MAX) {
        id = INT_TO_JSID(index);
        return DefineNativeProperty(cx, obj, id, value, getter, setter, attrs);
    }

    AutoRooterGetterSetter gsRoot(cx, attrs, &getter, &setter);

    if (!IndexToId(cx, index, &id))
        return false;

    return DefineNativeProperty(cx, obj, id, value, getter, setter, attrs);
}

/* static */ bool
JSObject::defineElement(ExclusiveContext *cx, HandleObject obj,
                        uint32_t index, HandleValue value,
                        JSPropertyOp getter, JSStrictPropertyOp setter, unsigned attrs)
{
    js::DefineElementOp op = obj->getOps()->defineElement;
    if (op) {
        if (!cx->shouldBeJSContext())
            return false;
        return op(cx->asJSContext(), obj, index, value, getter, setter, attrs);
    }
    return baseops::DefineElement(cx, obj, index, value, getter, setter, attrs);
}

Shape *
JSObject::addDataProperty(ExclusiveContext *cx, jsid idArg, uint32_t slot, unsigned attrs)
{
    JS_ASSERT(!(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
    RootedObject self(cx, this);
    RootedId id(cx, idArg);
    return addProperty(cx, self, id, nullptr, nullptr, slot, attrs, 0);
}

Shape *
JSObject::addDataProperty(ExclusiveContext *cx, HandlePropertyName name,
                          uint32_t slot, unsigned attrs)
{
    JS_ASSERT(!(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
    RootedObject self(cx, this);
    RootedId id(cx, NameToId(name));
    return addProperty(cx, self, id, nullptr, nullptr, slot, attrs, 0);
}

/*
 * Backward compatibility requires allowing addProperty hooks to mutate the
 * nominal initial value of a slotful property, while GC safety wants that
 * value to be stored before the call-out through the hook.  Optimize to do
 * both while saving cycles for classes that stub their addProperty hook.
 */
template <ExecutionMode mode>
static inline bool
CallAddPropertyHook(typename ExecutionModeTraits<mode>::ExclusiveContextType cxArg,
                    const Class *clasp, HandleObject obj, HandleShape shape,
                    HandleValue nominal)
{
    if (clasp->addProperty != JS_PropertyStub) {
        if (mode == ParallelExecution)
            return false;

        ExclusiveContext *cx = cxArg->asExclusiveContext();
        if (!cx->shouldBeJSContext())
            return false;

        /* Make a local copy of value so addProperty can mutate its inout parameter. */
        RootedValue value(cx, nominal);

        Rooted<jsid> id(cx, shape->propid());
        if (!CallJSPropertyOp(cx->asJSContext(), clasp->addProperty, obj, id, &value)) {
            obj->removeProperty(cx, shape->propid());
            return false;
        }
        if (value.get() != nominal) {
            if (shape->hasSlot())
                obj->nativeSetSlotWithType(cx, shape, value);
        }
    }
    return true;
}

template <ExecutionMode mode>
static inline bool
CallAddPropertyHookDense(typename ExecutionModeTraits<mode>::ExclusiveContextType cxArg,
                         const Class *clasp, HandleObject obj, uint32_t index,
                         HandleValue nominal)
{
    /* Inline addProperty for array objects. */
    if (obj->is<ArrayObject>()) {
        ArrayObject *arr = &obj->as<ArrayObject>();
        uint32_t length = arr->length();
        if (index >= length) {
            if (mode == ParallelExecution) {
                /* We cannot deal with overflows in parallel. */
                if (length > INT32_MAX)
                    return false;
                arr->setLengthInt32(index + 1);
            } else {
                arr->setLength(cxArg->asExclusiveContext(), index + 1);
            }
        }
        return true;
    }

    if (clasp->addProperty != JS_PropertyStub) {
        if (mode == ParallelExecution)
            return false;

        ExclusiveContext *cx = cxArg->asExclusiveContext();
        if (!cx->shouldBeJSContext())
            return false;

        if (!obj->maybeCopyElementsForWrite(cx))
            return false;

        /* Make a local copy of value so addProperty can mutate its inout parameter. */
        RootedValue value(cx, nominal);

        Rooted<jsid> id(cx, INT_TO_JSID(index));
        if (!CallJSPropertyOp(cx->asJSContext(), clasp->addProperty, obj, id, &value)) {
            obj->setDenseElementHole(cx, index);
            return false;
        }
        if (value.get() != nominal)
            obj->setDenseElementWithType(cx, index, value);
    }

    return true;
}

template <ExecutionMode mode>
static bool
UpdateShapeTypeAndValue(typename ExecutionModeTraits<mode>::ExclusiveContextType cx,
                        JSObject *obj, Shape *shape, const Value &value)
{
    jsid id = shape->propid();
    if (shape->hasSlot()) {
        if (mode == ParallelExecution) {
            if (!obj->nativeSetSlotIfHasType(shape, value, /* overwriting = */ false))
                return false;
        } else {
            obj->nativeSetSlotWithType(cx->asExclusiveContext(), shape, value, /* overwriting = */ false);
        }
    }
    if (!shape->hasSlot() || !shape->hasDefaultGetter() || !shape->hasDefaultSetter()) {
        if (mode == ParallelExecution) {
            if (!IsTypePropertyIdMarkedNonData(obj, id))
                return false;
        } else {
            MarkTypePropertyNonData(cx->asExclusiveContext(), obj, id);
        }
    }
    if (!shape->writable()) {
        if (mode == ParallelExecution) {
            if (!IsTypePropertyIdMarkedNonWritable(obj, id))
                return false;
        } else {
            MarkTypePropertyNonWritable(cx->asExclusiveContext(), obj, id);
        }
    }
    return true;
}

template <ExecutionMode mode>
static inline bool
DefinePropertyOrElement(typename ExecutionModeTraits<mode>::ExclusiveContextType cx,
                        HandleObject obj, HandleId id,
                        PropertyOp getter, StrictPropertyOp setter,
                        unsigned attrs, HandleValue value,
                        bool callSetterAfterwards, bool setterIsStrict)
{
    /* Use dense storage for new indexed properties where possible. */
    if (JSID_IS_INT(id) &&
        getter == JS_PropertyStub &&
        setter == JS_StrictPropertyStub &&
        attrs == JSPROP_ENUMERATE &&
        (!obj->isIndexed() || !obj->nativeContainsPure(id)) &&
        !obj->is<TypedArrayObject>())
    {
        uint32_t index = JSID_TO_INT(id);
        bool definesPast;
        if (!WouldDefinePastNonwritableLength(cx, obj, index, setterIsStrict, &definesPast))
            return false;
        if (definesPast)
            return true;

        JSObject::EnsureDenseResult result;
        if (mode == ParallelExecution) {
            if (obj->writeToIndexWouldMarkNotPacked(index))
                return false;
            result = obj->ensureDenseElementsPreservePackedFlag(cx, index, 1);
        } else {
            result = obj->ensureDenseElements(cx->asExclusiveContext(), index, 1);
        }

        if (result == JSObject::ED_FAILED)
            return false;
        if (result == JSObject::ED_OK) {
            if (mode == ParallelExecution) {
                if (!obj->setDenseElementIfHasType(index, value))
                    return false;
            } else {
                obj->setDenseElementWithType(cx->asExclusiveContext(), index, value);
            }
            return CallAddPropertyHookDense<mode>(cx, obj->getClass(), obj, index, value);
        }
    }

    if (obj->is<ArrayObject>()) {
        Rooted<ArrayObject*> arr(cx, &obj->as<ArrayObject>());
        if (id == NameToId(cx->names().length)) {
            if (mode == SequentialExecution && !cx->shouldBeJSContext())
                return false;
            return ArraySetLength<mode>(ExecutionModeTraits<mode>::toContextType(cx), arr, id,
                                        attrs, value, setterIsStrict);
        }

        uint32_t index;
        if (js_IdIsIndex(id, &index)) {
            bool definesPast;
            if (!WouldDefinePastNonwritableLength(cx, arr, index, setterIsStrict, &definesPast))
                return false;
            if (definesPast)
                return true;
        }
    }

    // Don't define new indexed properties on typed arrays.
    if (obj->is<TypedArrayObject>()) {
        uint64_t index;
        if (IsTypedArrayIndex(id, &index))
            return true;
    }

    AutoRooterGetterSetter gsRoot(cx, attrs, &getter, &setter);

    RootedShape shape(cx, JSObject::putProperty<mode>(cx, obj, id, getter, setter,
                                                      SHAPE_INVALID_SLOT, attrs, 0));
    if (!shape)
        return false;

    if (!UpdateShapeTypeAndValue<mode>(cx, obj, shape, value))
        return false;

    /*
     * Clear any existing dense index after adding a sparse indexed property,
     * and investigate converting the object to dense indexes.
     */
    if (JSID_IS_INT(id)) {
        if (mode == ParallelExecution)
            return false;

        if (!obj->maybeCopyElementsForWrite(cx))
            return false;

        ExclusiveContext *ncx = cx->asExclusiveContext();
        uint32_t index = JSID_TO_INT(id);
        JSObject::removeDenseElementForSparseIndex(ncx, obj, index);
        JSObject::EnsureDenseResult result = JSObject::maybeDensifySparseElements(ncx, obj);
        if (result == JSObject::ED_FAILED)
            return false;
        if (result == JSObject::ED_OK) {
            JS_ASSERT(setter == JS_StrictPropertyStub);
            return CallAddPropertyHookDense<mode>(cx, obj->getClass(), obj, index, value);
        }
    }

    if (!CallAddPropertyHook<mode>(cx, obj->getClass(), obj, shape, value))
        return false;

    if (callSetterAfterwards && setter != JS_StrictPropertyStub) {
        if (!cx->shouldBeJSContext())
            return false;
        RootedValue nvalue(cx, value);
        return NativeSet<mode>(ExecutionModeTraits<mode>::toContextType(cx),
                               obj, obj, shape, setterIsStrict, &nvalue);
    }
    return true;
}

static bool
NativeLookupOwnProperty(ExclusiveContext *cx, HandleObject obj, HandleId id,
                        MutableHandle<Shape*> shapep);

bool
js::DefineNativeProperty(ExclusiveContext *cx, HandleObject obj, HandleId id, HandleValue value,
                         PropertyOp getter, StrictPropertyOp setter, unsigned attrs)
{
    JS_ASSERT(!(attrs & JSPROP_NATIVE_ACCESSORS));

    AutoRooterGetterSetter gsRoot(cx, attrs, &getter, &setter);

    RootedShape shape(cx);
    RootedValue updateValue(cx, value);
    bool shouldDefine = true;

    /*
     * If defining a getter or setter, we must check for its counterpart and
     * update the attributes and property ops.  A getter or setter is really
     * only half of a property.
     */
    if (attrs & (JSPROP_GETTER | JSPROP_SETTER)) {
        if (!NativeLookupOwnProperty(cx, obj, id, &shape))
            return false;
        if (shape) {
            /*
             * If we are defining a getter whose setter was already defined, or
             * vice versa, finish the job via obj->changeProperty.
             */
            if (IsImplicitDenseOrTypedArrayElement(shape)) {
                if (obj->is<TypedArrayObject>()) {
                    /* Ignore getter/setter properties added to typed arrays. */
                    return true;
                }
                if (!JSObject::sparsifyDenseElement(cx, obj, JSID_TO_INT(id)))
                    return false;
                shape = obj->nativeLookup(cx, id);
            }
            if (shape->isAccessorDescriptor()) {
                attrs = ApplyOrDefaultAttributes(attrs, shape);
                shape = JSObject::changeProperty<SequentialExecution>(cx, obj, shape, attrs,
                                                                      JSPROP_GETTER | JSPROP_SETTER,
                                                                      (attrs & JSPROP_GETTER)
                                                                      ? getter
                                                                      : shape->getter(),
                                                                      (attrs & JSPROP_SETTER)
                                                                      ? setter
                                                                      : shape->setter());
                if (!shape)
                    return false;
                shouldDefine = false;
            }
        }
    } else if (!(attrs & JSPROP_IGNORE_VALUE)) {
        /*
         * We might still want to ignore redefining some of our attributes, if the
         * request came through a proxy after Object.defineProperty(), but only if we're redefining
         * a data property.
         * FIXME: All this logic should be removed when Proxies use PropDesc, but we need to
         *        remove JSPropertyOp getters and setters first.
         * FIXME: This is still wrong for various array types, and will set the wrong attributes
         *        by accident, but we can't use NativeLookupOwnProperty in this case, because of resolve
         *        loops.
         */
        shape = obj->nativeLookup(cx, id);
        if (shape && shape->isDataDescriptor())
            attrs = ApplyOrDefaultAttributes(attrs, shape);
    } else {
        /*
         * We have been asked merely to update some attributes by a caller of
         * Object.defineProperty, laundered through the proxy system, and returning here. We can
         * get away with just using JSObject::changeProperty here.
         */
        if (!NativeLookupOwnProperty(cx, obj, id, &shape))
            return false;

        if (shape) {
            // Don't forget about arrays.
            if (IsImplicitDenseOrTypedArrayElement(shape)) {
                if (obj->is<TypedArrayObject>()) {
                    /*
                     * Silently ignore attempts to change individial index attributes.
                     * FIXME: Uses the same broken behavior as for accessors. This should
                     *        probably throw.
                     */
                    return true;
                }
                if (!JSObject::sparsifyDenseElement(cx, obj, JSID_TO_INT(id)))
                    return false;
                shape = obj->nativeLookup(cx, id);
            }

            attrs = ApplyOrDefaultAttributes(attrs, shape);

            /* Keep everything from the shape that isn't the things we're changing */
            unsigned attrMask = ~(JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT);
            shape = JSObject::changeProperty<SequentialExecution>(cx, obj, shape, attrs, attrMask,
                                                                  shape->getter(), shape->setter());
            if (!shape)
                return false;
            if (shape->hasSlot())
                updateValue = obj->getSlot(shape->slot());
            shouldDefine = false;
        }
    }

    /*
     * Purge the property cache of any properties named by id that are about
     * to be shadowed in obj's scope chain.
     */
    if (!PurgeScopeChain(cx, obj, id))
        return false;

    /* Use the object's class getter and setter by default. */
    const Class *clasp = obj->getClass();
    if (!getter && !(attrs & JSPROP_GETTER))
        getter = clasp->getProperty;
    if (!setter && !(attrs & JSPROP_SETTER))
        setter = clasp->setProperty;

    if (shouldDefine) {
        // Handle the default cases here. Anyone that wanted to set non-default attributes has
        // cleared the IGNORE flags by now. Since we can never get here with JSPROP_IGNORE_VALUE
        // relevant, just clear it.
        attrs = ApplyOrDefaultAttributes(attrs) & ~JSPROP_IGNORE_VALUE;
        return DefinePropertyOrElement<SequentialExecution>(cx, obj, id, getter, setter,
                                                            attrs, value, false, false);
    }

    MOZ_ASSERT(shape);

    JS_ALWAYS_TRUE(UpdateShapeTypeAndValue<SequentialExecution>(cx, obj, shape, updateValue));

    return CallAddPropertyHook<SequentialExecution>(cx, clasp, obj, shape, updateValue);
}

/*
 * Call obj's resolve hook.
 *
 * cx, id, and flags are the parameters initially passed to the ongoing lookup;
 * objp and propp are its out parameters. obj is an object along the prototype
 * chain from where the lookup started.
 *
 * There are four possible outcomes:
 *
 *   - On failure, report an error or exception and return false.
 *
 *   - If we are already resolving a property of *curobjp, set *recursedp = true,
 *     and return true.
 *
 *   - If the resolve hook finds or defines the sought property, set *objp and
 *     *propp appropriately, set *recursedp = false, and return true.
 *
 *   - Otherwise no property was resolved. Set *propp = nullptr and
 *     *recursedp = false and return true.
 */
static MOZ_ALWAYS_INLINE bool
CallResolveOp(JSContext *cx, HandleObject obj, HandleId id, MutableHandleObject objp,
              MutableHandleShape propp, bool *recursedp)
{
    const Class *clasp = obj->getClass();
    JSResolveOp resolve = clasp->resolve;

    /*
     * Avoid recursion on (obj, id) already being resolved on cx.
     *
     * Once we have successfully added an entry for (obj, key) to
     * cx->resolvingTable, control must go through cleanup: before
     * returning.  But note that JS_DHASH_ADD may find an existing
     * entry, in which case we bail to suppress runaway recursion.
     */
    AutoResolving resolving(cx, obj, id);
    if (resolving.alreadyStarted()) {
        /* Already resolving id in obj -- suppress recursion. */
        *recursedp = true;
        return true;
    }
    *recursedp = false;

    propp.set(nullptr);

    if (clasp->flags & JSCLASS_NEW_RESOLVE) {
        JSNewResolveOp newresolve = reinterpret_cast<JSNewResolveOp>(resolve);
        RootedObject obj2(cx, nullptr);
        if (!newresolve(cx, obj, id, &obj2))
            return false;

        /*
         * We trust the new style resolve hook to set obj2 to nullptr when
         * the id cannot be resolved. But, when obj2 is not null, we do
         * not assume that id must exist and do full nativeLookup for
         * compatibility.
         */
        if (!obj2)
            return true;

        if (!obj2->isNative()) {
            /* Whoops, newresolve handed back a foreign obj2. */
            JS_ASSERT(obj2 != obj);
            return JSObject::lookupGeneric(cx, obj2, id, objp, propp);
        }

        objp.set(obj2);
    } else {
        if (!resolve(cx, obj, id))
            return false;

        objp.set(obj);
    }

    if (JSID_IS_INT(id) && objp->containsDenseElement(JSID_TO_INT(id))) {
        MarkDenseOrTypedArrayElementFound<CanGC>(propp);
        return true;
    }

    Shape *shape;
    if (!objp->nativeEmpty() && (shape = objp->nativeLookup(cx, id)))
        propp.set(shape);
    else
        objp.set(nullptr);

    return true;
}

template <AllowGC allowGC>
static MOZ_ALWAYS_INLINE bool
LookupOwnPropertyInline(ExclusiveContext *cx,
                        typename MaybeRooted<JSObject*, allowGC>::HandleType obj,
                        typename MaybeRooted<jsid, allowGC>::HandleType id,
                        typename MaybeRooted<JSObject*, allowGC>::MutableHandleType objp,
                        typename MaybeRooted<Shape*, allowGC>::MutableHandleType propp,
                        bool *donep)
{
    // Check for a native dense element.
    if (JSID_IS_INT(id) && obj->containsDenseElement(JSID_TO_INT(id))) {
        objp.set(obj);
        MarkDenseOrTypedArrayElementFound<allowGC>(propp);
        *donep = true;
        return true;
    }

    // Check for a typed array element. Integer lookups always finish here
    // so that integer properties on the prototype are ignored even for out
    // of bounds accesses.
    if (obj->template is<TypedArrayObject>()) {
        uint64_t index;
        if (IsTypedArrayIndex(id, &index)) {
            if (index < obj->template as<TypedArrayObject>().length()) {
                objp.set(obj);
                MarkDenseOrTypedArrayElementFound<allowGC>(propp);
            } else {
                objp.set(nullptr);
                propp.set(nullptr);
            }
            *donep = true;
            return true;
        }
    }

    // Check for a native property.
    if (Shape *shape = obj->nativeLookup(cx, id)) {
        objp.set(obj);
        propp.set(shape);
        *donep = true;
        return true;
    }

    // id was not found in obj. Try obj's resolve hook, if any.
    if (obj->getClass()->resolve != JS_ResolveStub) {
        if (!cx->shouldBeJSContext() || !allowGC)
            return false;

        bool recursed;
        if (!CallResolveOp(cx->asJSContext(),
                           MaybeRooted<JSObject*, allowGC>::toHandle(obj),
                           MaybeRooted<jsid, allowGC>::toHandle(id),
                           MaybeRooted<JSObject*, allowGC>::toMutableHandle(objp),
                           MaybeRooted<Shape*, allowGC>::toMutableHandle(propp),
                           &recursed))
        {
            return false;
        }

        if (recursed) {
            objp.set(nullptr);
            propp.set(nullptr);
            *donep = true;
            return true;
        }

        if (propp) {
            *donep = true;
            return true;
        }
    }

    *donep = false;
    return true;
}

static bool
NativeLookupOwnProperty(ExclusiveContext *cx, HandleObject obj, HandleId id,
                        MutableHandle<Shape*> shapep)
{
    RootedObject pobj(cx);
    bool done;

    if (!LookupOwnPropertyInline<CanGC>(cx, obj, id, &pobj, shapep, &done))
        return false;
    if (!done || pobj != obj)
        shapep.set(nullptr);
    return true;
}

template <AllowGC allowGC>
static MOZ_ALWAYS_INLINE bool
LookupPropertyInline(ExclusiveContext *cx,
                     typename MaybeRooted<JSObject*, allowGC>::HandleType obj,
                     typename MaybeRooted<jsid, allowGC>::HandleType id,
                     typename MaybeRooted<JSObject*, allowGC>::MutableHandleType objp,
                     typename MaybeRooted<Shape*, allowGC>::MutableHandleType propp)
{
    /* NB: The logic of this procedure is implicitly reflected in
     *     BaselineIC.cpp's |EffectlesslyLookupProperty| logic.
     *     If this changes, please remember to update the logic there as well.
     */

    /* Search scopes starting with obj and following the prototype link. */
    typename MaybeRooted<JSObject*, allowGC>::RootType current(cx, obj);

    while (true) {
        bool done;
        if (!LookupOwnPropertyInline<allowGC>(cx, current, id, objp, propp, &done))
            return false;
        if (done)
            return true;

        typename MaybeRooted<JSObject*, allowGC>::RootType proto(cx, current->getProto());

        if (!proto)
            break;
        if (!proto->isNative()) {
            if (!cx->shouldBeJSContext() || !allowGC)
                return false;
            return JSObject::lookupGeneric(cx->asJSContext(),
                                           MaybeRooted<JSObject*, allowGC>::toHandle(proto),
                                           MaybeRooted<jsid, allowGC>::toHandle(id),
                                           MaybeRooted<JSObject*, allowGC>::toMutableHandle(objp),
                                           MaybeRooted<Shape*, allowGC>::toMutableHandle(propp));
        }

        current = proto;
    }

    objp.set(nullptr);
    propp.set(nullptr);
    return true;
}

template <AllowGC allowGC>
bool
baseops::LookupProperty(ExclusiveContext *cx,
                        typename MaybeRooted<JSObject*, allowGC>::HandleType obj,
                        typename MaybeRooted<jsid, allowGC>::HandleType id,
                        typename MaybeRooted<JSObject*, allowGC>::MutableHandleType objp,
                        typename MaybeRooted<Shape*, allowGC>::MutableHandleType propp)
{
    return LookupPropertyInline<allowGC>(cx, obj, id, objp, propp);
}

template bool
baseops::LookupProperty<CanGC>(ExclusiveContext *cx, HandleObject obj, HandleId id,
                               MutableHandleObject objp, MutableHandleShape propp);

template bool
baseops::LookupProperty<NoGC>(ExclusiveContext *cx, JSObject *obj, jsid id,
                              FakeMutableHandle<JSObject*> objp,
                              FakeMutableHandle<Shape*> propp);

/* static */ bool
JSObject::lookupGeneric(JSContext *cx, HandleObject obj, js::HandleId id,
                        MutableHandleObject objp, MutableHandleShape propp)
{
    /* NB: The logic of lookupGeneric is implicitly reflected in
     *     BaselineIC.cpp's |EffectlesslyLookupProperty| logic.
     *     If this changes, please remember to update the logic there as well.
     */
    LookupGenericOp op = obj->getOps()->lookupGeneric;
    if (op)
        return op(cx, obj, id, objp, propp);
    return baseops::LookupProperty<js::CanGC>(cx, obj, id, objp, propp);
}

bool
baseops::LookupElement(JSContext *cx, HandleObject obj, uint32_t index,
                       MutableHandleObject objp, MutableHandleShape propp)
{
    RootedId id(cx);
    if (!IndexToId(cx, index, &id))
        return false;

    return LookupPropertyInline<CanGC>(cx, obj, id, objp, propp);
}

bool
js::LookupNativeProperty(ExclusiveContext *cx, HandleObject obj, HandleId id,
                         MutableHandleObject objp, MutableHandleShape propp)
{
    return LookupPropertyInline<CanGC>(cx, obj, id, objp, propp);
}

bool
js::LookupName(JSContext *cx, HandlePropertyName name, HandleObject scopeChain,
               MutableHandleObject objp, MutableHandleObject pobjp, MutableHandleShape propp)
{
    RootedId id(cx, NameToId(name));

    for (RootedObject scope(cx, scopeChain); scope; scope = scope->enclosingScope()) {
        if (!JSObject::lookupGeneric(cx, scope, id, pobjp, propp))
            return false;
        if (propp) {
            objp.set(scope);
            return true;
        }
    }

    objp.set(nullptr);
    pobjp.set(nullptr);
    propp.set(nullptr);
    return true;
}

bool
js::LookupNameNoGC(JSContext *cx, PropertyName *name, JSObject *scopeChain,
                   JSObject **objp, JSObject **pobjp, Shape **propp)
{
    AutoAssertNoException nogc(cx);

    JS_ASSERT(!*objp && !*pobjp && !*propp);

    for (JSObject *scope = scopeChain; scope; scope = scope->enclosingScope()) {
        if (scope->getOps()->lookupGeneric)
            return false;
        if (!LookupPropertyInline<NoGC>(cx, scope, NameToId(name), pobjp, propp))
            return false;
        if (*propp) {
            *objp = scope;
            return true;
        }
    }

    return true;
}

bool
js::LookupNameWithGlobalDefault(JSContext *cx, HandlePropertyName name, HandleObject scopeChain,
                                MutableHandleObject objp)
{
    RootedId id(cx, NameToId(name));

    RootedObject pobj(cx);
    RootedShape prop(cx);

    RootedObject scope(cx, scopeChain);
    for (; !scope->is<GlobalObject>(); scope = scope->enclosingScope()) {
        if (!JSObject::lookupGeneric(cx, scope, id, &pobj, &prop))
            return false;
        if (prop)
            break;
    }

    objp.set(scope);
    return true;
}

bool
js::LookupNameUnqualified(JSContext *cx, HandlePropertyName name, HandleObject scopeChain,
                          MutableHandleObject objp)
{
    RootedId id(cx, NameToId(name));

    RootedObject pobj(cx);
    RootedShape prop(cx);

    RootedObject scope(cx, scopeChain);
    for (; !scope->isUnqualifiedVarObj(); scope = scope->enclosingScope()) {
        if (!JSObject::lookupGeneric(cx, scope, id, &pobj, &prop))
            return false;
        if (prop)
            break;
    }

    objp.set(scope);
    return true;
}

template <AllowGC allowGC>
bool
js::HasOwnProperty(JSContext *cx, LookupGenericOp lookup,
                   typename MaybeRooted<JSObject*, allowGC>::HandleType obj,
                   typename MaybeRooted<jsid, allowGC>::HandleType id,
                   typename MaybeRooted<JSObject*, allowGC>::MutableHandleType objp,
                   typename MaybeRooted<Shape*, allowGC>::MutableHandleType propp)
{
    if (lookup) {
        if (!allowGC)
            return false;
        if (!lookup(cx,
                    MaybeRooted<JSObject*, allowGC>::toHandle(obj),
                    MaybeRooted<jsid, allowGC>::toHandle(id),
                    MaybeRooted<JSObject*, allowGC>::toMutableHandle(objp),
                    MaybeRooted<Shape*, allowGC>::toMutableHandle(propp)))
        {
            return false;
        }
    } else {
        bool done;
        if (!LookupOwnPropertyInline<allowGC>(cx, obj, id, objp, propp, &done))
            return false;
        if (!done) {
            objp.set(nullptr);
            propp.set(nullptr);
            return true;
        }
    }

    if (!propp)
        return true;

    if (objp == obj)
        return true;

    JSObject *outer = nullptr;
    if (js::ObjectOp op = objp->getClass()->ext.outerObject) {
        if (!allowGC)
            return false;
        RootedObject inner(cx, objp);
        outer = op(cx, inner);
        if (!outer)
            return false;
    }

    if (outer != objp)
        propp.set(nullptr);
    return true;
}

template bool
js::HasOwnProperty<CanGC>(JSContext *cx, LookupGenericOp lookup,
                          HandleObject obj, HandleId id,
                          MutableHandleObject objp, MutableHandleShape propp);

template bool
js::HasOwnProperty<NoGC>(JSContext *cx, LookupGenericOp lookup,
                         JSObject *obj, jsid id,
                         FakeMutableHandle<JSObject*> objp, FakeMutableHandle<Shape*> propp);

bool
js::HasOwnProperty(JSContext *cx, HandleObject obj, HandleId id, bool *resultp)
{
    RootedObject pobj(cx);
    RootedShape shape(cx);
    if (!HasOwnProperty<CanGC>(cx, obj->getOps()->lookupGeneric, obj, id, &pobj, &shape))
        return false;
    *resultp = (shape != nullptr);
    return true;
}

template <AllowGC allowGC>
static MOZ_ALWAYS_INLINE bool
NativeGetInline(JSContext *cx,
                typename MaybeRooted<JSObject*, allowGC>::HandleType obj,
                typename MaybeRooted<JSObject*, allowGC>::HandleType receiver,
                typename MaybeRooted<JSObject*, allowGC>::HandleType pobj,
                typename MaybeRooted<Shape*, allowGC>::HandleType shape,
                typename MaybeRooted<Value, allowGC>::MutableHandleType vp)
{
    JS_ASSERT(pobj->isNative());

    if (shape->hasSlot()) {
        vp.set(pobj->nativeGetSlot(shape->slot()));
        JS_ASSERT(!vp.isMagic());
        JS_ASSERT_IF(!pobj->hasSingletonType() &&
                     !pobj->template is<ScopeObject>() &&
                     shape->hasDefaultGetter(),
                     js::types::TypeHasProperty(cx, pobj->type(), shape->propid(), vp));
    } else {
        vp.setUndefined();
    }
    if (shape->hasDefaultGetter())
        return true;

    {
        jsbytecode *pc;
        JSScript *script = cx->currentScript(&pc);
        if (script && script->hasBaselineScript()) {
            switch (JSOp(*pc)) {
              case JSOP_GETPROP:
              case JSOP_CALLPROP:
              case JSOP_LENGTH:
                script->baselineScript()->noteAccessedGetter(script->pcToOffset(pc));
                break;
              default:
                break;
            }
        }
    }

    if (!allowGC)
        return false;

    if (!shape->get(cx,
                    MaybeRooted<JSObject*, allowGC>::toHandle(receiver),
                    MaybeRooted<JSObject*, allowGC>::toHandle(obj),
                    MaybeRooted<JSObject*, allowGC>::toHandle(pobj),
                    MaybeRooted<Value, allowGC>::toMutableHandle(vp)))
    {
        return false;
    }

    /* Update slotful shapes according to the value produced by the getter. */
    if (shape->hasSlot() && pobj->nativeContains(cx, shape))
        pobj->nativeSetSlot(shape->slot(), vp);

    return true;
}

bool
js::NativeGet(JSContext *cx, Handle<JSObject*> obj, Handle<JSObject*> pobj, Handle<Shape*> shape,
              MutableHandle<Value> vp)
{
    return NativeGetInline<CanGC>(cx, obj, obj, pobj, shape, vp);
}

template <ExecutionMode mode>
bool
js::NativeSet(typename ExecutionModeTraits<mode>::ContextType cxArg,
              Handle<JSObject*> obj, Handle<JSObject*> receiver,
              HandleShape shape, bool strict, MutableHandleValue vp)
{
    JS_ASSERT(cxArg->isThreadLocal(obj));
    JS_ASSERT(obj->isNative());

    if (shape->hasSlot()) {
        /* If shape has a stub setter, just store vp. */
        if (shape->hasDefaultSetter()) {
            if (mode == ParallelExecution) {
                if (!obj->nativeSetSlotIfHasType(shape, vp))
                    return false;
            } else {
                obj->nativeSetSlotWithType(cxArg->asExclusiveContext(), shape, vp);
            }

            return true;
        }
    }

    if (mode == ParallelExecution)
        return false;
    JSContext *cx = cxArg->asJSContext();

    if (!shape->hasSlot()) {
        /*
         * Allow API consumers to create shared properties with stub setters.
         * Such properties effectively function as data descriptors which are
         * not writable, so attempting to set such a property should do nothing
         * or throw if we're in strict mode.
         */
        if (!shape->hasGetterValue() && shape->hasDefaultSetter())
            return js_ReportGetterOnlyAssignment(cx, strict);
    }

    RootedValue ovp(cx, vp);

    uint32_t sample = cx->runtime()->propertyRemovals;
    if (!shape->set(cx, obj, receiver, strict, vp))
        return false;

    /*
     * Update any slot for the shape with the value produced by the setter,
     * unless the setter deleted the shape.
     */
    if (shape->hasSlot() &&
        (MOZ_LIKELY(cx->runtime()->propertyRemovals == sample) ||
         obj->nativeContains(cx, shape)))
    {
        obj->setSlot(shape->slot(), vp);
    }

    return true;
}

template bool
js::NativeSet<SequentialExecution>(JSContext *cx,
                                   Handle<JSObject*> obj, Handle<JSObject*> receiver,
                                   HandleShape shape, bool strict, MutableHandleValue vp);
template bool
js::NativeSet<ParallelExecution>(ForkJoinContext *cx,
                                 Handle<JSObject*> obj, Handle<JSObject*> receiver,
                                 HandleShape shape, bool strict, MutableHandleValue vp);

template <AllowGC allowGC>
static MOZ_ALWAYS_INLINE bool
GetPropertyHelperInline(JSContext *cx,
                        typename MaybeRooted<JSObject*, allowGC>::HandleType obj,
                        typename MaybeRooted<JSObject*, allowGC>::HandleType receiver,
                        typename MaybeRooted<jsid, allowGC>::HandleType id,
                        typename MaybeRooted<Value, allowGC>::MutableHandleType vp)
{
    /* This call site is hot -- use the always-inlined variant of LookupNativeProperty(). */
    typename MaybeRooted<JSObject*, allowGC>::RootType obj2(cx);
    typename MaybeRooted<Shape*, allowGC>::RootType shape(cx);
    if (!LookupPropertyInline<allowGC>(cx, obj, id, &obj2, &shape))
        return false;

    if (!shape) {
        if (!allowGC)
            return false;

        vp.setUndefined();

        if (!CallJSPropertyOp(cx, obj->getClass()->getProperty,
                              MaybeRooted<JSObject*, allowGC>::toHandle(obj),
                              MaybeRooted<jsid, allowGC>::toHandle(id),
                              MaybeRooted<Value, allowGC>::toMutableHandle(vp)))
        {
            return false;
        }

        /*
         * Give a strict warning if foo.bar is evaluated by a script for an
         * object foo with no property named 'bar'.
         */
        if (vp.isUndefined()) {
            jsbytecode *pc = nullptr;
            RootedScript script(cx, cx->currentScript(&pc));
            if (!pc)
                return true;
            JSOp op = (JSOp) *pc;

            if (op == JSOP_GETXPROP) {
                /* Undefined property during a name lookup, report an error. */
                JSAutoByteString printable;
                if (js_ValueToPrintable(cx, IdToValue(id), &printable))
                    js_ReportIsNotDefined(cx, printable.ptr());
                return false;
            }

            /* Don't warn if extra warnings not enabled or for random getprop operations. */
            if (!cx->compartment()->options().extraWarnings(cx) || (op != JSOP_GETPROP && op != JSOP_GETELEM))
                return true;

            /* Don't warn repeatedly for the same script. */
            if (!script || script->warnedAboutUndefinedProp())
                return true;

            /*
             * Don't warn in self-hosted code (where the further presence of
             * JS::RuntimeOptions::werror() would result in impossible-to-avoid
             * errors to entirely-innocent client code).
             */
            if (script->selfHosted())
                return true;

            /* We may just be checking if that object has an iterator. */
            if (JSID_IS_ATOM(id, cx->names().iteratorIntrinsic))
                return true;

            /* Do not warn about tests like (obj[prop] == undefined). */
            pc += js_CodeSpec[op].length;
            if (Detecting(cx, script, pc))
                return true;

            unsigned flags = JSREPORT_WARNING | JSREPORT_STRICT;
            script->setWarnedAboutUndefinedProp();

            /* Ok, bad undefined property reference: whine about it. */
            RootedValue val(cx, IdToValue(id));
            if (!js_ReportValueErrorFlags(cx, flags, JSMSG_UNDEFINED_PROP,
                                          JSDVG_IGNORE_STACK, val, js::NullPtr(),
                                          nullptr, nullptr))
            {
                return false;
            }
        }
        return true;
    }

    if (!obj2->isNative()) {
        if (!allowGC)
            return false;
        HandleObject obj2Handle = MaybeRooted<JSObject*, allowGC>::toHandle(obj2);
        HandleObject receiverHandle = MaybeRooted<JSObject*, allowGC>::toHandle(receiver);
        HandleId idHandle = MaybeRooted<jsid, allowGC>::toHandle(id);
        MutableHandleValue vpHandle = MaybeRooted<Value, allowGC>::toMutableHandle(vp);
        return obj2->template is<ProxyObject>()
               ? Proxy::get(cx, obj2Handle, receiverHandle, idHandle, vpHandle)
               : JSObject::getGeneric(cx, obj2Handle, obj2Handle, idHandle, vpHandle);
    }

    if (IsImplicitDenseOrTypedArrayElement(shape)) {
        vp.set(obj2->getDenseOrTypedArrayElement(JSID_TO_INT(id)));
        return true;
    }

    /* This call site is hot -- use the always-inlined variant of NativeGet(). */
    if (!NativeGetInline<allowGC>(cx, obj, receiver, obj2, shape, vp))
        return false;

    return true;
}

bool
baseops::GetProperty(JSContext *cx, HandleObject obj, HandleObject receiver, HandleId id, MutableHandleValue vp)
{
    /* This call site is hot -- use the always-inlined variant of GetPropertyHelper(). */
    return GetPropertyHelperInline<CanGC>(cx, obj, receiver, id, vp);
}

bool
baseops::GetPropertyNoGC(JSContext *cx, JSObject *obj, JSObject *receiver, jsid id, Value *vp)
{
    AutoAssertNoException nogc(cx);
    return GetPropertyHelperInline<NoGC>(cx, obj, receiver, id, vp);
}

static MOZ_ALWAYS_INLINE bool
LookupPropertyPureInline(JSObject *obj, jsid id, JSObject **objp, Shape **propp)
{
    if (!obj->isNative())
        return false;

    JSObject *current = obj;
    while (true) {
        /* Search for a native dense element, typed array element, or property. */

        if (JSID_IS_INT(id) && current->containsDenseElement(JSID_TO_INT(id))) {
            *objp = current;
            MarkDenseOrTypedArrayElementFound<NoGC>(propp);
            return true;
        }

        if (current->is<TypedArrayObject>()) {
            uint64_t index;
            if (IsTypedArrayIndex(id, &index)) {
                if (index < obj->as<TypedArrayObject>().length()) {
                    *objp = current;
                    MarkDenseOrTypedArrayElementFound<NoGC>(propp);
                } else {
                    *objp = nullptr;
                    *propp = nullptr;
                }
                return true;
            }
        }

        if (Shape *shape = current->nativeLookupPure(id)) {
            *objp = current;
            *propp = shape;
            return true;
        }

        /* Fail if there's a resolve hook. */
        if (current->getClass()->resolve != JS_ResolveStub)
            return false;

        JSObject *proto = current->getProto();

        if (!proto)
            break;
        if (!proto->isNative())
            return false;

        current = proto;
    }

    *objp = nullptr;
    *propp = nullptr;
    return true;
}

static MOZ_ALWAYS_INLINE bool
NativeGetPureInline(JSObject *pobj, Shape *shape, Value *vp)
{
    JS_ASSERT(pobj->isNative());

    if (shape->hasSlot()) {
        *vp = pobj->nativeGetSlot(shape->slot());
        JS_ASSERT(!vp->isMagic());
    } else {
        vp->setUndefined();
    }

    /* Fail if we have a custom getter. */
    return shape->hasDefaultGetter();
}

bool
js::LookupPropertyPure(JSObject *obj, jsid id, JSObject **objp, Shape **propp)
{
    return LookupPropertyPureInline(obj, id, objp, propp);
}

/*
 * A pure version of GetPropertyHelper that can be called from parallel code
 * without locking. This code path cannot GC. This variant returns false
 * whenever a side-effect might have occured in the effectful version. This
 * includes, but is not limited to:
 *
 *  - Any object in the lookup chain has a non-stub resolve hook.
 *  - Any object in the lookup chain is non-native.
 *  - The property has a getter.
 */
bool
js::GetPropertyPure(ThreadSafeContext *cx, JSObject *obj, jsid id, Value *vp)
{
    /* Deal with native objects. */
    JSObject *obj2;
    Shape *shape;
    if (!LookupPropertyPureInline(obj, id, &obj2, &shape))
        return false;

    if (!shape) {
        /* Fail if we have a non-stub class op hooks. */
        if (obj->getClass()->getProperty && obj->getClass()->getProperty != JS_PropertyStub)
            return false;

        if (obj->getOps()->getElement)
            return false;

        /* Vanilla native object, return undefined. */
        vp->setUndefined();
        return true;
    }

    if (IsImplicitDenseOrTypedArrayElement(shape)) {
        *vp = obj2->getDenseOrTypedArrayElement(JSID_TO_INT(id));
        return true;
    }

    /* Special case 'length' on Array and TypedArray. */
    if (JSID_IS_ATOM(id, cx->names().length)) {
        if (obj->is<ArrayObject>()) {
            vp->setNumber(obj->as<ArrayObject>().length());
            return true;
        }

        if (obj->is<TypedArrayObject>()) {
            vp->setNumber(obj->as<TypedArrayObject>().length());
            return true;
        }
    }

    return NativeGetPureInline(obj2, shape, vp);
}

static bool
MOZ_ALWAYS_INLINE
GetElementPure(ThreadSafeContext *cx, JSObject *obj, uint32_t index, Value *vp)
{
    if (index <= JSID_INT_MAX)
        return GetPropertyPure(cx, obj, INT_TO_JSID(index), vp);
    return false;
}

/*
 * A pure version of GetObjectElementOperation that can be called from
 * parallel code without locking. This variant returns false whenever a
 * side-effect might have occurred.
 */
bool
js::GetObjectElementOperationPure(ThreadSafeContext *cx, JSObject *obj, const Value &prop,
                                  Value *vp)
{
    uint32_t index;
    if (IsDefinitelyIndex(prop, &index))
        return GetElementPure(cx, obj, index, vp);

    /* Atomizing the property value is effectful and not threadsafe. */
    if (!prop.isString() || !prop.toString()->isAtom())
        return false;

    JSAtom *name = &prop.toString()->asAtom();
    if (name->isIndex(&index))
        return GetElementPure(cx, obj, index, vp);

    return GetPropertyPure(cx, obj, NameToId(name->asPropertyName()), vp);
}

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

    /* This call site is hot -- use the always-inlined variant of js_GetPropertyHelper(). */
    return GetPropertyHelperInline<CanGC>(cx, obj, receiver, id, vp);
}

static bool
MaybeReportUndeclaredVarAssignment(JSContext *cx, JSString *propname)
{
    {
        JSScript *script = cx->currentScript(nullptr, JSContext::ALLOW_CROSS_COMPARTMENT);
        if (!script)
            return true;

        // If the code is not strict and extra warnings aren't enabled, then no
        // check is needed.
        if (!script->strict() && !cx->compartment()->options().extraWarnings(cx))
            return true;
    }

    JSAutoByteString bytes(cx, propname);
    return !!bytes &&
           JS_ReportErrorFlagsAndNumber(cx,
                                        (JSREPORT_WARNING | JSREPORT_STRICT
                                         | JSREPORT_STRICT_MODE_ERROR),
                                        js_GetErrorMessage, nullptr,
                                        JSMSG_UNDECLARED_VAR, bytes.ptr());
}

bool
JSObject::reportReadOnly(ThreadSafeContext *cxArg, jsid id, unsigned report)
{
    if (cxArg->isForkJoinContext())
        return cxArg->asForkJoinContext()->reportError(report);

    if (!cxArg->isJSContext())
        return true;

    JSContext *cx = cxArg->asJSContext();
    RootedValue val(cx, IdToValue(id));
    return js_ReportValueErrorFlags(cx, report, JSMSG_READ_ONLY,
                                    JSDVG_IGNORE_STACK, val, js::NullPtr(),
                                    nullptr, nullptr);
}

bool
JSObject::reportNotConfigurable(ThreadSafeContext *cxArg, jsid id, unsigned report)
{
    if (cxArg->isForkJoinContext())
        return cxArg->asForkJoinContext()->reportError(report);

    if (!cxArg->isJSContext())
        return true;

    JSContext *cx = cxArg->asJSContext();
    RootedValue val(cx, IdToValue(id));
    return js_ReportValueErrorFlags(cx, report, JSMSG_CANT_DELETE,
                                    JSDVG_IGNORE_STACK, val, js::NullPtr(),
                                    nullptr, nullptr);
}

bool
JSObject::reportNotExtensible(ThreadSafeContext *cxArg, unsigned report)
{
    if (cxArg->isForkJoinContext())
        return cxArg->asForkJoinContext()->reportError(report);

    if (!cxArg->isJSContext())
        return true;

    JSContext *cx = cxArg->asJSContext();
    RootedValue val(cx, ObjectValue(*this));
    return js_ReportValueErrorFlags(cx, report, JSMSG_OBJECT_NOT_EXTENSIBLE,
                                    JSDVG_IGNORE_STACK, val, js::NullPtr(),
                                    nullptr, nullptr);
}

bool
JSObject::callMethod(JSContext *cx, HandleId id, unsigned argc, Value *argv, MutableHandleValue vp)
{
    RootedValue fval(cx);
    RootedObject obj(cx, this);
    if (!JSObject::getGeneric(cx, obj, obj, id, &fval))
        return false;
    return Invoke(cx, ObjectValue(*obj), fval, argc, argv, vp);
}

template <ExecutionMode mode>
bool
baseops::SetPropertyHelper(typename ExecutionModeTraits<mode>::ContextType cxArg,
                           HandleObject obj, HandleObject receiver, HandleId id,
                           QualifiedBool qualified, MutableHandleValue vp, bool strict)
{
    JS_ASSERT(cxArg->isThreadLocal(obj));

    if (MOZ_UNLIKELY(obj->watched())) {
        if (mode == ParallelExecution)
            return false;

        /* Fire watchpoints, if any. */
        JSContext *cx = cxArg->asJSContext();
        WatchpointMap *wpmap = cx->compartment()->watchpointMap;
        if (wpmap && !wpmap->triggerWatchpoint(cx, obj, id, vp))
            return false;
    }

    RootedObject pobj(cxArg);
    RootedShape shape(cxArg);
    if (mode == ParallelExecution) {
        if (!LookupPropertyPure(obj, id, pobj.address(), shape.address()))
            return false;
    } else {
        JSContext *cx = cxArg->asJSContext();
        if (!LookupNativeProperty(cx, obj, id, &pobj, &shape))
            return false;
    }
    if (shape) {
        if (!pobj->isNative()) {
            if (pobj->is<ProxyObject>()) {
                if (mode == ParallelExecution)
                    return false;

                JSContext *cx = cxArg->asJSContext();
                Rooted<PropertyDescriptor> pd(cx);
                if (!Proxy::getPropertyDescriptor(cx, pobj, id, &pd))
                    return false;

                if ((pd.attributes() & (JSPROP_SHARED | JSPROP_SHADOWABLE)) == JSPROP_SHARED) {
                    return !pd.setter() ||
                           CallSetter(cx, receiver, id, pd.setter(), pd.attributes(), strict, vp);
                }

                if (pd.isReadonly()) {
                    if (strict)
                        return JSObject::reportReadOnly(cx, id, JSREPORT_ERROR);
                    if (cx->compartment()->options().extraWarnings(cx))
                        return JSObject::reportReadOnly(cx, id, JSREPORT_STRICT | JSREPORT_WARNING);
                    return true;
                }
            }

            shape = nullptr;
        }
    } else {
        /* We should never add properties to lexical blocks. */
        JS_ASSERT(!obj->is<BlockObject>());

        if (obj->isUnqualifiedVarObj() && !qualified) {
            if (mode == ParallelExecution)
                return false;

            if (!MaybeReportUndeclaredVarAssignment(cxArg->asJSContext(), JSID_TO_STRING(id)))
                return false;
        }
    }

    /*
     * Now either shape is null, meaning id was not found in obj or one of its
     * prototypes; or shape is non-null, meaning id was found directly in pobj.
     */
    unsigned attrs = JSPROP_ENUMERATE;
    const Class *clasp = obj->getClass();
    PropertyOp getter = clasp->getProperty;
    StrictPropertyOp setter = clasp->setProperty;

    if (IsImplicitDenseOrTypedArrayElement(shape)) {
        /* ES5 8.12.4 [[Put]] step 2, for a dense data property on pobj. */
        if (pobj != obj)
            shape = nullptr;
    } else if (shape) {
        /* ES5 8.12.4 [[Put]] step 2. */
        if (shape->isAccessorDescriptor()) {
            if (shape->hasDefaultSetter()) {
                /* Bail out of parallel execution if we are strict to throw. */
                if (mode == ParallelExecution)
                    return !strict;

                return js_ReportGetterOnlyAssignment(cxArg->asJSContext(), strict);
            }
        } else {
            JS_ASSERT(shape->isDataDescriptor());

            if (!shape->writable()) {
                /*
                 * Error in strict mode code, warn with extra warnings
                 * options, otherwise do nothing.
                 *
                 * Bail out of parallel execution if we are strict to throw.
                 */
                if (mode == ParallelExecution)
                    return !strict;

                JSContext *cx = cxArg->asJSContext();
                if (strict)
                    return JSObject::reportReadOnly(cx, id, JSREPORT_ERROR);
                if (cx->compartment()->options().extraWarnings(cx))
                    return JSObject::reportReadOnly(cx, id, JSREPORT_STRICT | JSREPORT_WARNING);
                return true;
            }
        }

        attrs = shape->attributes();
        if (pobj != obj) {
            /*
             * We found id in a prototype object: prepare to share or shadow.
             */
            if (!shape->shadowable()) {
                if (shape->hasDefaultSetter() && !shape->hasGetterValue())
                    return true;

                if (mode == ParallelExecution)
                    return false;

                return shape->set(cxArg->asJSContext(), obj, receiver, strict, vp);
            }

            /*
             * Preserve attrs except JSPROP_SHARED, getter, and setter when
             * shadowing any property that has no slot (is shared). We must
             * clear the shared attribute for the shadowing shape so that the
             * property in obj that it defines has a slot to retain the value
             * being set, in case the setter simply cannot operate on instances
             * of obj's class by storing the value in some class-specific
             * location.
             */
            if (!shape->hasSlot()) {
                attrs &= ~JSPROP_SHARED;
                getter = shap