js/src/vm/JSObject.cpp
author Jan de Mooij <jdemooij@mozilla.com>
Thu, 21 Jun 2018 11:05:42 +0200
changeset 477488 422829b56d7fe2bcd0e1d0e2bcc74c119c6a0f6c
parent 477487 4db8094fadc1b5577ab3668e1f49875af9f758f6
child 478770 2f70bd2a3a9b4ee46613b08533bb106e9a73cd20
permissions -rw-r--r--
Bug 1469217 part 6 - Remove JSPROP_SHADOWABLE, address review comments. r=anba

/* -*- 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 "vm/JSObject-inl.h"

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

#include <string.h>

#include "jsapi.h"
#include "jsexn.h"
#include "jsfriendapi.h"
#include "jsnum.h"
#include "jstypes.h"
#include "jsutil.h"

#include "builtin/Array.h"
#ifdef ENABLE_BIGINT
#include "builtin/BigInt.h"
#endif
#include "builtin/Eval.h"
#include "builtin/Object.h"
#include "builtin/String.h"
#include "builtin/Symbol.h"
#include "frontend/BytecodeCompiler.h"
#include "gc/Policy.h"
#include "jit/BaselineJIT.h"
#include "js/MemoryMetrics.h"
#include "js/Proxy.h"
#include "js/UbiNode.h"
#include "js/UniquePtr.h"
#include "js/Wrapper.h"
#include "util/Text.h"
#include "util/Windows.h"
#include "vm/ArgumentsObject.h"
#include "vm/BytecodeUtil.h"
#include "vm/Interpreter.h"
#include "vm/Iteration.h"
#include "vm/JSAtom.h"
#include "vm/JSContext.h"
#include "vm/JSFunction.h"
#include "vm/JSScript.h"
#include "vm/ProxyObject.h"
#include "vm/RegExpStaticsObject.h"
#include "vm/Shape.h"
#include "vm/TypedArrayObject.h"

#include "builtin/Boolean-inl.h"
#include "builtin/TypedObject-inl.h"
#include "gc/Marking-inl.h"
#include "vm/ArrayObject-inl.h"
#include "vm/BooleanObject-inl.h"
#include "vm/Caches-inl.h"
#include "vm/Compartment-inl.h"
#include "vm/Interpreter-inl.h"
#include "vm/JSAtom-inl.h"
#include "vm/JSContext-inl.h"
#include "vm/JSFunction-inl.h"
#include "vm/NativeObject-inl.h"
#include "vm/NumberObject-inl.h"
#include "vm/Realm-inl.h"
#include "vm/Shape-inl.h"
#include "vm/StringObject-inl.h"
#include "vm/TypedArrayObject-inl.h"
#include "vm/UnboxedObject-inl.h"

using namespace js;
using namespace js::gc;

void
js::ReportNotObject(JSContext* cx, const Value& v)
{
    MOZ_ASSERT(!v.isObject());

    RootedValue value(cx, v);
    UniqueChars bytes = DecompileValueGenerator(cx, JSDVG_SEARCH_STACK, value, nullptr);
    if (bytes)
        JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr, JSMSG_NOT_NONNULL_OBJECT,
                                   bytes.get());
}

void
js::ReportNotObjectArg(JSContext* cx, const char* nth, const char* fun, HandleValue v)
{
    MOZ_ASSERT(!v.isObject());

    JSAutoByteString bytes;
    if (const char* chars = ValueToSourceForError(cx, v, bytes)) {
        JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr, JSMSG_NOT_NONNULL_OBJECT_ARG,
                                   nth, fun, chars);
    }
}

void
js::ReportNotObjectWithName(JSContext* cx, const char* name, HandleValue v)
{
    MOZ_ASSERT(!v.isObject());

    JSAutoByteString bytes;
    if (const char* chars = ValueToSourceForError(cx, v, bytes)) {
        JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr, JSMSG_NOT_NONNULL_OBJECT_NAME,
                                   name, chars);
    }
}

JS_PUBLIC_API(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";
}

// ES6 draft rev37 6.2.4.4 FromPropertyDescriptor
JS_PUBLIC_API(bool)
JS::FromPropertyDescriptor(JSContext* cx, Handle<PropertyDescriptor> desc, MutableHandleValue vp)
{
    AssertHeapIsIdle();
    CHECK_REQUEST(cx);
    assertSameCompartment(cx, desc);

    // Step 1.
    if (!desc.object()) {
        vp.setUndefined();
        return true;
    }

    return FromPropertyDescriptorToObject(cx, desc, vp);
}

bool
js::FromPropertyDescriptorToObject(JSContext* cx, Handle<PropertyDescriptor> desc,
                                   MutableHandleValue vp)
{
    // Step 2-3.
    RootedObject obj(cx, NewBuiltinClassInstance<PlainObject>(cx));
    if (!obj)
        return false;

    const JSAtomState& names = cx->names();

    // Step 4.
    if (desc.hasValue()) {
        if (!DefineDataProperty(cx, obj, names.value, desc.value()))
            return false;
    }

    // Step 5.
    RootedValue v(cx);
    if (desc.hasWritable()) {
        v.setBoolean(desc.writable());
        if (!DefineDataProperty(cx, obj, names.writable, v))
            return false;
    }

    // Step 6.
    if (desc.hasGetterObject()) {
        if (JSObject* get = desc.getterObject())
            v.setObject(*get);
        else
            v.setUndefined();
        if (!DefineDataProperty(cx, obj, names.get, v))
            return false;
    }

    // Step 7.
    if (desc.hasSetterObject()) {
        if (JSObject* set = desc.setterObject())
            v.setObject(*set);
        else
            v.setUndefined();
        if (!DefineDataProperty(cx, obj, names.set, v))
            return false;
    }

    // Step 8.
    if (desc.hasEnumerable()) {
        v.setBoolean(desc.enumerable());
        if (!DefineDataProperty(cx, obj, names.enumerable, v))
            return false;
    }

    // Step 9.
    if (desc.hasConfigurable()) {
        v.setBoolean(desc.configurable());
        if (!DefineDataProperty(cx, obj, names.configurable, v))
            return false;
    }

    vp.setObject(*obj);
    return true;
}

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

    HandleValue v = args[0];
    if (!v.isObject()) {
        UniqueChars bytes = DecompileValueGenerator(cx, JSDVG_SEARCH_STACK, v, nullptr);
        if (!bytes)
            return false;
        JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
                                   bytes.get(), "not an object");
        return false;
    }

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

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

    return GetProperty(cx, obj, obj, id, vp);
}

bool
js::Throw(JSContext* cx, jsid id, unsigned errorNumber, const char* details)
{
    MOZ_ASSERT(js_ErrorFormatString[errorNumber].argCount == (details ? 2 : 1));

    RootedValue idVal(cx, IdToValue(id));
    JSString* idstr = ValueToSource(cx, idVal);
    if (!idstr)
       return false;
    JSAutoByteString bytes(cx, idstr);
    if (!bytes)
        return false;

    if (details) {
        JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr, errorNumber, bytes.ptr(),
                                   details);
    } else {
        JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr, errorNumber, bytes.ptr());
    }

    return false;
}


/*** PropertyDescriptor operations and DefineProperties ******************************************/

static const char js_getter_str[] = "getter";
static const char js_setter_str[] = "setter";

static Result<>
CheckCallable(JSContext* cx, JSObject* obj, const char* fieldName)
{
    if (obj && !obj->isCallable()) {
        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_GET_SET_FIELD,
                                  fieldName);
        return cx->alreadyReportedError();
    }
    return Ok();
}

bool
js::ToPropertyDescriptor(JSContext* cx, HandleValue descval, bool checkAccessors,
                         MutableHandle<PropertyDescriptor> desc)
{
    // step 2
    RootedObject obj(cx, NonNullObjectWithName(cx, "property descriptor", descval));
    if (!obj)
        return false;

    // step 3
    desc.clear();

    bool found = false;
    RootedId id(cx);
    RootedValue v(cx);
    unsigned attrs = 0;

    // step 4
    id = NameToId(cx->names().enumerable);
    if (!GetPropertyIfPresent(cx, obj, id, &v, &found))
        return false;
    if (found) {
        if (ToBoolean(v))
            attrs |= JSPROP_ENUMERATE;
    } else {
        attrs |= JSPROP_IGNORE_ENUMERATE;
    }

    // step 5
    id = NameToId(cx->names().configurable);
    if (!GetPropertyIfPresent(cx, obj, id, &v, &found))
        return false;
    if (found) {
        if (!ToBoolean(v))
            attrs |= JSPROP_PERMANENT;
    } else {
        attrs |= JSPROP_IGNORE_PERMANENT;
    }

    // step 6
    id = NameToId(cx->names().value);
    if (!GetPropertyIfPresent(cx, obj, id, &v, &found))
        return false;
    if (found)
        desc.value().set(v);
    else
        attrs |= JSPROP_IGNORE_VALUE;

    // step 7
    id = NameToId(cx->names().writable);
    if (!GetPropertyIfPresent(cx, obj, id, &v, &found))
        return false;
    if (found) {
        if (!ToBoolean(v))
            attrs |= JSPROP_READONLY;
    } else {
        attrs |= JSPROP_IGNORE_READONLY;
    }

    // step 8
    bool hasGetOrSet;
    id = NameToId(cx->names().get);
    if (!GetPropertyIfPresent(cx, obj, id, &v, &found))
        return false;
    hasGetOrSet = found;
    if (found) {
        if (v.isObject()) {
            if (checkAccessors)
                JS_TRY_OR_RETURN_FALSE(cx, CheckCallable(cx, &v.toObject(), js_getter_str));
            desc.setGetterObject(&v.toObject());
        } else if (!v.isUndefined()) {
            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_GET_SET_FIELD,
                                      js_getter_str);
            return false;
        }
        attrs |= JSPROP_GETTER;
    }

    // step 9
    id = NameToId(cx->names().set);
    if (!GetPropertyIfPresent(cx, obj, id, &v, &found))
        return false;
    hasGetOrSet |= found;
    if (found) {
        if (v.isObject()) {
            if (checkAccessors)
                JS_TRY_OR_RETURN_FALSE(cx, CheckCallable(cx, &v.toObject(), js_setter_str));
            desc.setSetterObject(&v.toObject());
        } else if (!v.isUndefined()) {
            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_GET_SET_FIELD,
                                      js_setter_str);
            return false;
        }
        attrs |= JSPROP_SETTER;
    }

    // step 10
    if (hasGetOrSet) {
        if (!(attrs & JSPROP_IGNORE_READONLY) || !(attrs & JSPROP_IGNORE_VALUE)) {
            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_DESCRIPTOR);
            return false;
        }

        // By convention, these bits are not used on accessor descriptors.
        attrs &= ~(JSPROP_IGNORE_READONLY | JSPROP_IGNORE_VALUE);
    }

    desc.setAttributes(attrs);
    MOZ_ASSERT_IF(attrs & JSPROP_READONLY, !(attrs & (JSPROP_GETTER | JSPROP_SETTER)));
    return true;
}

Result<>
js::CheckPropertyDescriptorAccessors(JSContext* cx, Handle<PropertyDescriptor> desc)
{
    if (desc.hasGetterObject())
        MOZ_TRY(CheckCallable(cx, desc.getterObject(), js_getter_str));

    if (desc.hasSetterObject())
        MOZ_TRY(CheckCallable(cx, desc.setterObject(), js_setter_str));

    return Ok();
}

void
js::CompletePropertyDescriptor(MutableHandle<PropertyDescriptor> desc)
{
    desc.assertValid();

    if (desc.isGenericDescriptor() || desc.isDataDescriptor()) {
        if (!desc.hasWritable())
            desc.attributesRef() |= JSPROP_READONLY;
        desc.attributesRef() &= ~(JSPROP_IGNORE_READONLY | JSPROP_IGNORE_VALUE);
    } else {
        if (!desc.hasGetterObject())
            desc.setGetterObject(nullptr);
        if (!desc.hasSetterObject())
            desc.setSetterObject(nullptr);
        desc.attributesRef() |= JSPROP_GETTER | JSPROP_SETTER;
    }
    if (!desc.hasConfigurable())
        desc.attributesRef() |= JSPROP_PERMANENT;
    desc.attributesRef() &= ~(JSPROP_IGNORE_PERMANENT | JSPROP_IGNORE_ENUMERATE);

    desc.assertComplete();
}

bool
js::ReadPropertyDescriptors(JSContext* cx, HandleObject props, bool checkAccessors,
                            AutoIdVector* ids, MutableHandle<PropertyDescriptorVector> descs)
{
    if (!GetPropertyKeys(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<PropertyDescriptor> desc(cx);
        RootedValue v(cx);
        if (!GetProperty(cx, props, props, id, &v) ||
            !ToPropertyDescriptor(cx, v, checkAccessors, &desc) ||
            !descs.append(desc))
        {
            return false;
        }
    }
    return true;
}

/*** Seal and freeze *****************************************************************************/

static unsigned
GetSealedOrFrozenAttributes(unsigned attrs, IntegrityLevel level)
{
    /* Make all attributes permanent; if freezing, make data attributes read-only. */
    if (level == IntegrityLevel::Frozen && !(attrs & (JSPROP_GETTER | JSPROP_SETTER)))
        return JSPROP_PERMANENT | JSPROP_READONLY;
    return JSPROP_PERMANENT;
}

/* ES6 draft rev 29 (6 Dec 2014) 7.3.13. */
bool
js::SetIntegrityLevel(JSContext* cx, HandleObject obj, IntegrityLevel level)
{
    assertSameCompartment(cx, obj);

    // Steps 3-5. (Steps 1-2 are redundant assertions.)
    if (!PreventExtensions(cx, obj))
        return false;

    // Steps 6-9, loosely interpreted.
    if (obj->isNative() && !obj->as<NativeObject>().inDictionaryMode() &&
        !obj->is<TypedArrayObject>() && !obj->is<MappedArgumentsObject>())
    {
        HandleNativeObject nobj = obj.as<NativeObject>();

        // 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, nobj->getClass(),
                                                         nobj->taggedProto(),
                                                         nobj->numFixedSlots(),
                                                         nobj->lastProperty()->getObjectFlags()));
        if (!last)
            return false;

        // Get an in-order list of the shapes in this object.
        using ShapeVec = GCVector<Shape*, 8>;
        Rooted<ShapeVec> shapes(cx, ShapeVec(cx));
        for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
            if (!shapes.append(&r.front()))
                return false;
        }
        Reverse(shapes.begin(), shapes.end());

        for (Shape* shape : shapes) {
            Rooted<StackShape> child(cx, StackShape(shape));
            child.setAttrs(child.attrs() | GetSealedOrFrozenAttributes(child.attrs(), level));

            if (!JSID_IS_EMPTY(child.get().propid) && level == IntegrityLevel::Frozen)
                MarkTypePropertyNonWritable(cx, nobj, child.get().propid);

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

        MOZ_ASSERT(nobj->lastProperty()->slotSpan() == last->slotSpan());
        MOZ_ALWAYS_TRUE(nobj->setLastProperty(cx, last));

        // Ordinarily ArraySetLength handles this, but we're going behind its back
        // right now, so we must do this manually.
        if (level == IntegrityLevel::Frozen && obj->is<ArrayObject>()) {
            MOZ_ASSERT(!nobj->denseElementsAreCopyOnWrite());
            obj->as<ArrayObject>().setNonWritableLength(cx);
        }
    } else {
        // Steps 6-7.
        AutoIdVector keys(cx);
        if (!GetPropertyKeys(cx, obj, JSITER_HIDDEN | JSITER_OWNONLY | JSITER_SYMBOLS, &keys))
            return false;

        RootedId id(cx);
        Rooted<PropertyDescriptor> desc(cx);

        const unsigned AllowConfigure = JSPROP_IGNORE_ENUMERATE | JSPROP_IGNORE_READONLY |
                                        JSPROP_IGNORE_VALUE;
        const unsigned AllowConfigureAndWritable = AllowConfigure & ~JSPROP_IGNORE_READONLY;

        // 8.a/9.a. The two different loops are merged here.
        for (size_t i = 0; i < keys.length(); i++) {
            id = keys[i];

            if (level == IntegrityLevel::Sealed) {
                // 8.a.i.
                desc.setAttributes(AllowConfigure | JSPROP_PERMANENT);
            } else {
                // 9.a.i-ii.
                Rooted<PropertyDescriptor> currentDesc(cx);
                if (!GetOwnPropertyDescriptor(cx, obj, id, &currentDesc))
                    return false;

                // 9.a.iii.
                if (!currentDesc.object())
                    continue;

                // 9.a.iii.1-2
                if (currentDesc.isAccessorDescriptor())
                    desc.setAttributes(AllowConfigure | JSPROP_PERMANENT);
                else
                    desc.setAttributes(AllowConfigureAndWritable | JSPROP_PERMANENT | JSPROP_READONLY);
            }

            // 8.a.i-ii. / 9.a.iii.3-4
            if (!DefineProperty(cx, obj, id, desc))
                return false;
        }
    }

    // Finally, freeze or seal the dense elements.
    if (obj->isNative())
        ObjectElements::FreezeOrSeal(cx, &obj->as<NativeObject>(), level);

    return true;
}

static bool
ResolveLazyProperties(JSContext* cx, HandleNativeObject obj)
{
    const Class* clasp = obj->getClass();
    if (JSEnumerateOp enumerate = clasp->getEnumerate()) {
        if (!enumerate(cx, obj))
            return false;
    }
    if (clasp->getNewEnumerate() && clasp->getResolve()) {
        AutoIdVector properties(cx);
        if (!clasp->getNewEnumerate()(cx, obj, properties, /* enumerableOnly = */ false))
            return false;

        RootedId id(cx);
        for (size_t i = 0; i < properties.length(); i++) {
            id = properties[i];
            bool found;
            if (!HasOwnProperty(cx, obj, id, &found))
                return false;
        }
    }
    return true;
}

// ES6 draft rev33 (12 Feb 2015) 7.3.15
bool
js::TestIntegrityLevel(JSContext* cx, HandleObject obj, IntegrityLevel level, bool* result)
{
    // Steps 3-6. (Steps 1-2 are redundant assertions.)
    bool status;
    if (!IsExtensible(cx, obj, &status))
        return false;
    if (status) {
        *result = false;
        return true;
    }

    // Fast path for native objects.
    if (obj->isNative()) {
        HandleNativeObject nobj = obj.as<NativeObject>();

        // Force lazy properties to be resolved.
        if (!ResolveLazyProperties(cx, nobj))
            return false;

        // Typed array elements are non-configurable, writable properties, so
        // if any elements are present, the typed array cannot be frozen.
        if (nobj->is<TypedArrayObject>() && nobj->as<TypedArrayObject>().length() > 0 &&
            level == IntegrityLevel::Frozen)
        {
            *result = false;
            return true;
        }

        bool hasDenseElements = false;
        for (size_t i = 0; i < nobj->getDenseInitializedLength(); i++) {
            if (nobj->containsDenseElement(i)) {
                hasDenseElements = true;
                break;
            }
        }

        if (hasDenseElements) {
            // Unless the sealed flag is set, dense elements are configurable.
            if (!nobj->denseElementsAreSealed()) {
                *result = false;
                return true;
            }

            // Unless the frozen flag is set, dense elements are writable.
            if (level == IntegrityLevel::Frozen && !nobj->denseElementsAreFrozen()) {
                *result = false;
                return true;
            }
        }

        // Steps 7-9.
        for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
            Shape* shape = &r.front();

            // Steps 9.c.i-ii.
            if (shape->configurable() ||
                (level == IntegrityLevel::Frozen &&
                 shape->isDataDescriptor() && shape->writable()))
            {
                *result = false;
                return true;
            }
        }
    } else {
        // Steps 7-8.
        AutoIdVector props(cx);
        if (!GetPropertyKeys(cx, obj, JSITER_HIDDEN | JSITER_OWNONLY | JSITER_SYMBOLS, &props))
            return false;

        // Step 9.
        RootedId id(cx);
        Rooted<PropertyDescriptor> desc(cx);
        for (size_t i = 0, len = props.length(); i < len; i++) {
            id = props[i];

            // Steps 9.a-b.
            if (!GetOwnPropertyDescriptor(cx, obj, id, &desc))
                return false;

            // Step 9.c.
            if (!desc.object())
                continue;

            // Steps 9.c.i-ii.
            if (desc.configurable() ||
                (level == IntegrityLevel::Frozen && desc.isDataDescriptor() && desc.writable()))
            {
                *result = false;
                return true;
            }
        }
    }

    // Step 10.
    *result = true;
    return true;
}


/* * */

/*
 * 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::AllocKind::OBJECT8;
    if (clasp == &JSFunction::class_)
        return gc::AllocKind::OBJECT2;
    return gc::AllocKind::OBJECT4;
}

static inline JSObject*
NewObject(JSContext* cx, HandleObjectGroup group, gc::AllocKind kind,
          NewObjectKind newKind, uint32_t initialShapeFlags = 0)
{
    const Class* clasp = group->clasp();

    MOZ_ASSERT(clasp != &ArrayObject::class_);
    MOZ_ASSERT_IF(clasp == &JSFunction::class_,
                  kind == AllocKind::FUNCTION || kind == AllocKind::FUNCTION_EXTENDED);

    // 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, group->proto(), nfixed,
                                                      initialShapeFlags));
    if (!shape)
        return nullptr;

    gc::InitialHeap heap = GetInitialHeap(newKind, clasp);

    JSObject* obj;
    if (clasp->isJSFunction()) {
        JS_TRY_VAR_OR_RETURN_NULL(cx, obj, JSFunction::create(cx, kind, heap, shape, group));
    } else if (MOZ_LIKELY(clasp->isNative())) {
        JS_TRY_VAR_OR_RETURN_NULL(cx, obj, NativeObject::create(cx, kind, heap, shape, group));
    } else {
        MOZ_ASSERT(IsTypedObjectClass(clasp));
        JS_TRY_VAR_OR_RETURN_NULL(cx, obj, TypedObject::create(cx, kind, heap, shape, group));
    }

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

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

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

bool
js::NewObjectWithTaggedProtoIsCachable(JSContext* cx, Handle<TaggedProto> proto,
                                       NewObjectKind newKind, const Class* clasp)
{
    return !cx->helperThread() &&
           proto.isObject() &&
           newKind == GenericObject &&
           clasp->isNative() &&
           !proto.toObject()->is<GlobalObject>();
}

JSObject*
js::NewObjectWithGivenTaggedProto(JSContext* cx, const Class* clasp,
                                  Handle<TaggedProto> proto,
                                  gc::AllocKind allocKind, NewObjectKind newKind,
                                  uint32_t initialShapeFlags)
{
    if (CanBeFinalizedInBackground(allocKind, clasp))
        allocKind = GetBackgroundAllocKind(allocKind);

    bool isCachable = NewObjectWithTaggedProtoIsCachable(cx, proto, newKind, clasp);
    if (isCachable) {
        NewObjectCache& cache = cx->caches().newObjectCache;
        NewObjectCache::EntryIndex entry = -1;
        if (cache.lookupProto(clasp, proto.toObject(), allocKind, &entry)) {
            JSObject* obj = cache.newObjectFromHit(cx, entry, GetInitialHeap(newKind, clasp));
            if (obj)
                return obj;
        }
    }

    RootedObjectGroup group(cx, ObjectGroup::defaultNewGroup(cx, clasp, proto, nullptr));
    if (!group)
        return nullptr;

    RootedObject obj(cx, NewObject(cx, group, allocKind, newKind, initialShapeFlags));
    if (!obj)
        return nullptr;

    if (isCachable && !obj->as<NativeObject>().hasDynamicSlots()) {
        NewObjectCache& cache = cx->caches().newObjectCache;
        NewObjectCache::EntryIndex entry = -1;
        cache.lookupProto(clasp, proto.toObject(), allocKind, &entry);
        cache.fillProto(entry, clasp, proto, allocKind, &obj->as<NativeObject>());
    }

    return obj;
}

static bool
NewObjectIsCachable(JSContext* cx, NewObjectKind newKind, const Class* clasp)
{
    return !cx->helperThread() &&
           newKind == GenericObject &&
           clasp->isNative();
}

JSObject*
js::NewObjectWithClassProtoCommon(JSContext* cx, const Class* clasp, HandleObject protoArg,
                                  gc::AllocKind allocKind, NewObjectKind newKind)
{
    if (protoArg)
        return NewObjectWithGivenTaggedProto(cx, clasp, AsTaggedProto(protoArg), allocKind, newKind);

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

    Handle<GlobalObject*> global = cx->global();

    bool isCachable = NewObjectIsCachable(cx, newKind, clasp);
    if (isCachable) {
        NewObjectCache& cache = cx->caches().newObjectCache;
        NewObjectCache::EntryIndex entry = -1;
        if (cache.lookupGlobal(clasp, global, allocKind, &entry)) {
            gc::InitialHeap heap = GetInitialHeap(newKind, clasp);
            JSObject* obj = cache.newObjectFromHit(cx, entry, heap);
            if (obj)
                return obj;
        }
    }

    // Find the appropriate proto for clasp. Built-in classes have a cached
    // proto on cx->global(); all others get %ObjectPrototype%.
    JSProtoKey protoKey = JSCLASS_CACHED_PROTO_KEY(clasp);
    if (protoKey == JSProto_Null)
        protoKey = JSProto_Object;

    JSObject* proto = GlobalObject::getOrCreatePrototype(cx, protoKey);
    if (!proto)
        return nullptr;

    RootedObjectGroup group(cx, ObjectGroup::defaultNewGroup(cx, clasp, TaggedProto(proto)));
    if (!group)
        return nullptr;

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

    if (isCachable && !obj->as<NativeObject>().hasDynamicSlots()) {
        NewObjectCache& cache = cx->caches().newObjectCache;
        NewObjectCache::EntryIndex entry = -1;
        cache.lookupGlobal(clasp, global, allocKind, &entry);
        cache.fillGlobal(entry, clasp, global, allocKind, &obj->as<NativeObject>());
    }

    return obj;
}

static bool
NewObjectWithGroupIsCachable(JSContext* cx, HandleObjectGroup group,
                             NewObjectKind newKind)
{
    if (!group->proto().isObject() ||
        newKind != GenericObject ||
        !group->clasp()->isNative() ||
        cx->helperThread())
    {
        return false;
    }

    AutoSweepObjectGroup sweep(group);
    return !group->newScript(sweep) || group->newScript(sweep)->analyzed();
}

/*
 * Create a plain object with the specified group. This bypasses getNewGroup to
 * avoid losing creation site information for objects made by scripted 'new'.
 */
JSObject*
js::NewObjectWithGroupCommon(JSContext* cx, HandleObjectGroup group,
                             gc::AllocKind allocKind, NewObjectKind newKind)
{
    MOZ_ASSERT(gc::IsObjectAllocKind(allocKind));
    if (CanBeFinalizedInBackground(allocKind, group->clasp()))
        allocKind = GetBackgroundAllocKind(allocKind);

    bool isCachable = NewObjectWithGroupIsCachable(cx, group, newKind);
    if (isCachable) {
        NewObjectCache& cache = cx->caches().newObjectCache;
        NewObjectCache::EntryIndex entry = -1;
        if (cache.lookupGroup(group, allocKind, &entry)) {
            JSObject* obj = cache.newObjectFromHit(cx, entry,
                                                   GetInitialHeap(newKind, group->clasp()));
            if (obj)
                return obj;
        }
    }

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

    if (isCachable && !obj->as<NativeObject>().hasDynamicSlots()) {
        NewObjectCache& cache = cx->caches().newObjectCache;
        NewObjectCache::EntryIndex entry = -1;
        cache.lookupGroup(group, allocKind, &entry);
        cache.fillGroup(entry, group, allocKind, &obj->as<NativeObject>());
    }

    return obj;
}

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

    if (script) {
        /* Try to specialize the group of the object to the scripted call site. */
        if (!ObjectGroup::setAllocationSiteObjectGroup(cx, script, pc, obj, newKind == SingletonObject))
            return false;
    }

    pobj.set(obj);
    return true;
}

JSObject*
js::CreateThis(JSContext* cx, const Class* newclasp, HandleObject callee)
{
    RootedObject proto(cx);
    if (!GetPrototypeFromConstructor(cx, callee, &proto))
        return nullptr;
    gc::AllocKind kind = NewObjectGCKind(newclasp);
    return NewObjectWithClassProto(cx, newclasp, proto, kind);
}

static inline JSObject*
CreateThisForFunctionWithGroup(JSContext* cx, HandleObjectGroup group,
                               NewObjectKind newKind)
{
    bool isUnboxed;
    TypeNewScript* maybeNewScript;
    {
        AutoSweepObjectGroup sweep(group);
        isUnboxed = group->maybeUnboxedLayout(sweep);
        maybeNewScript = group->newScript(sweep);
    }

    if (isUnboxed && newKind != SingletonObject)
        return UnboxedPlainObject::create(cx, group, newKind);

    if (maybeNewScript) {
        if (maybeNewScript->analyzed()) {
            // The definite properties analysis has been performed for this
            // group, so get the shape and alloc kind to use from the
            // TypeNewScript's template.
            RootedPlainObject templateObject(cx, maybeNewScript->templateObject());
            MOZ_ASSERT(templateObject->group() == group);

            RootedPlainObject res(cx, CopyInitializerObject(cx, templateObject, newKind));
            if (!res)
                return nullptr;

            if (newKind == SingletonObject) {
                Rooted<TaggedProto> proto(cx, TaggedProto(templateObject->staticPrototype()));
                if (!JSObject::splicePrototype(cx, res, &PlainObject::class_, proto))
                    return nullptr;
            } else {
                res->setGroup(group);
            }
            return res;
        }

        // The initial objects registered with a TypeNewScript can't be in the
        // nursery.
        if (newKind == GenericObject)
            newKind = TenuredObject;

        // Not enough objects with this group have been created yet, so make a
        // plain object and register it with the group. Use the maximum number
        // of fixed slots, as is also required by the TypeNewScript.
        gc::AllocKind allocKind = GuessObjectGCKind(NativeObject::MAX_FIXED_SLOTS);
        PlainObject* res = NewObjectWithGroup<PlainObject>(cx, group, allocKind, newKind);
        if (!res)
            return nullptr;

        // Make sure group->newScript is still there.
        AutoSweepObjectGroup sweep(group);
        if (newKind != SingletonObject && group->newScript(sweep))
            group->newScript(sweep)->registerNewObject(res);

        return res;
    }

    gc::AllocKind allocKind = NewObjectGCKind(&PlainObject::class_);

    if (newKind == SingletonObject) {
        Rooted<TaggedProto> protoRoot(cx, group->proto());
        return NewObjectWithGivenTaggedProto<PlainObject>(cx, protoRoot, allocKind, newKind);
    }
    return NewObjectWithGroup<PlainObject>(cx, group, allocKind, newKind);
}

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

    if (proto) {
        RootedObjectGroup group(cx, ObjectGroup::defaultNewGroup(cx, nullptr, TaggedProto(proto),
                                                                 newTarget));
        if (!group)
            return nullptr;

        {
            AutoSweepObjectGroup sweep(group);
            if (group->newScript(sweep) && !group->newScript(sweep)->analyzed()) {
                bool regenerate;
                if (!group->newScript(sweep)->maybeAnalyze(cx, group, &regenerate))
                    return nullptr;
                if (regenerate) {
                    // The script was analyzed successfully and may have changed
                    // the new type table, so refetch the group.
                    group = ObjectGroup::defaultNewGroup(cx, nullptr, TaggedProto(proto),
                                                         newTarget);
                    AutoSweepObjectGroup sweepNewGroup(group);
                    MOZ_ASSERT(group && group->newScript(sweepNewGroup));
                }
            }
        }

        res = CreateThisForFunctionWithGroup(cx, group, newKind);
    } else {
        res = NewBuiltinClassInstance<PlainObject>(cx, newKind);
    }

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

    return res;
}

bool
js::GetPrototypeFromConstructor(JSContext* cx, HandleObject newTarget, MutableHandleObject proto)
{
    RootedValue protov(cx);
    if (!GetProperty(cx, newTarget, newTarget, cx->names().prototype, &protov))
        return false;
    proto.set(protov.isObject() ? &protov.toObject() : nullptr);
    return true;
}

JSObject*
js::CreateThisForFunction(JSContext* cx, HandleObject callee, HandleObject newTarget,
                          NewObjectKind newKind)
{
    RootedObject proto(cx);
    if (!GetPrototypeFromConstructor(cx, newTarget, &proto))
        return nullptr;

    JSObject* obj = CreateThisForFunctionWithProto(cx, callee, newTarget, proto, newKind);

    if (obj && newKind == SingletonObject) {
        RootedPlainObject nobj(cx, &obj->as<PlainObject>());

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

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

        return nobj;
    }

    return obj;
}

/* static */ bool
JSObject::nonNativeSetProperty(JSContext* cx, HandleObject obj, HandleId id, HandleValue v,
                               HandleValue receiver, ObjectOpResult& result)
{
    return obj->getOpsSetProperty()(cx, obj, id, v, receiver, result);
}

/* static */ bool
JSObject::nonNativeSetElement(JSContext* cx, HandleObject obj, uint32_t index, HandleValue v,
                              HandleValue receiver, ObjectOpResult& result)
{
    RootedId id(cx);
    if (!IndexToId(cx, index, &id))
        return false;
    return nonNativeSetProperty(cx, obj, id, v, receiver, result);
}

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

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

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

    if (copyBehavior == MakeNonConfigurableIntoConfigurable) {
        // Mask off the JSPROP_PERMANENT bit.
        desc.attributesRef() &= ~JSPROP_PERMANENT;
    }

    JSAutoRealm ar(cx, target);
    cx->markId(id);
    RootedId wrappedId(cx, id);
    if (!cx->compartment()->wrap(cx, &desc))
        return false;

    return DefineProperty(cx, target, wrappedId, desc);
}

JS_FRIEND_API(bool)
JS_CopyPropertiesFrom(JSContext* cx, HandleObject target, HandleObject obj)
{
    JSAutoRealm ar(cx, obj);

    AutoIdVector props(cx);
    if (!GetPropertyKeys(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
CopyProxyObject(JSContext* cx, Handle<ProxyObject*> from, Handle<ProxyObject*> to)
{
    MOZ_ASSERT(from->getClass() == to->getClass());

    if (from->is<WrapperObject>() &&
        (Wrapper::wrapperHandler(from)->flags() &
         Wrapper::CROSS_COMPARTMENT))
    {
        to->setCrossCompartmentPrivate(GetProxyPrivate(from));
    } else {
        RootedValue v(cx, GetProxyPrivate(from));
        if (!cx->compartment()->wrap(cx, &v))
            return false;
        to->setSameCompartmentPrivate(v);
    }

    MOZ_ASSERT(from->numReservedSlots() == to->numReservedSlots());

    RootedValue v(cx);
    for (size_t n = 0; n < from->numReservedSlots(); n++) {
        v = GetProxyReservedSlot(from, n);
        if (!cx->compartment()->wrap(cx, &v))
            return false;
        SetProxyReservedSlot(to, n, v);
    }

    return true;
}

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

    RootedObject clone(cx);
    if (obj->isNative()) {
        clone = NewObjectWithGivenTaggedProto(cx, obj->getClass(), proto);
        if (!clone)
            return nullptr;

        if (clone->is<JSFunction>() && (obj->compartment() != clone->compartment())) {
            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_CANT_CLONE_OBJECT);
            return nullptr;
        }

        if (obj->as<NativeObject>().hasPrivate())
            clone->as<NativeObject>().setPrivate(obj->as<NativeObject>().getPrivate());
    } else {
        ProxyOptions options;
        options.setClass(obj->getClass());

        clone = ProxyObject::New(cx, GetProxyHandler(obj), JS::NullHandleValue, proto, options);
        if (!clone)
            return nullptr;

        if (!CopyProxyObject(cx, obj.as<ProxyObject>(), clone.as<ProxyObject>()))
            return nullptr;
    }

    return clone;
}

static bool
GetScriptArrayObjectElements(HandleArrayObject arr, MutableHandle<GCVector<Value>> values)
{
    MOZ_ASSERT(!arr->isSingleton());
    MOZ_ASSERT(!arr->isIndexed());

    size_t length = arr->length();
    if (!values.appendN(MagicValue(JS_ELEMENTS_HOLE), length))
        return false;

    size_t initlen = arr->getDenseInitializedLength();
    for (size_t i = 0; i < initlen; i++)
        values[i].set(arr->getDenseElement(i));

    return true;
}

static bool
GetScriptPlainObjectProperties(HandleObject obj, MutableHandle<IdValueVector> properties)
{
    if (obj->is<PlainObject>()) {
        PlainObject* nobj = &obj->as<PlainObject>();

        if (!properties.appendN(IdValuePair(), nobj->slotSpan()))
            return false;

        for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
            Shape& shape = r.front();
            MOZ_ASSERT(shape.isDataDescriptor());
            uint32_t slot = shape.slot();
            properties[slot].get().id = shape.propid();
            properties[slot].get().value = nobj->getSlot(slot);
        }

        for (size_t i = 0; i < nobj->getDenseInitializedLength(); i++) {
            Value v = nobj->getDenseElement(i);
            if (!v.isMagic(JS_ELEMENTS_HOLE) && !properties.append(IdValuePair(INT_TO_JSID(i), v)))
                return false;
        }

        return true;
    }

    if (obj->is<UnboxedPlainObject>()) {
        UnboxedPlainObject* nobj = &obj->as<UnboxedPlainObject>();

        const UnboxedLayout& layout = nobj->layout();
        if (!properties.appendN(IdValuePair(), layout.properties().length()))
            return false;

        for (size_t i = 0; i < layout.properties().length(); i++) {
            const UnboxedLayout::Property& property = layout.properties()[i];
            properties[i].get().id = NameToId(property.name);
            properties[i].get().value = nobj->getValue(property);
        }

        return true;
    }

    MOZ_CRASH("Bad object kind");
}

static bool
DeepCloneValue(JSContext* cx, Value* vp, NewObjectKind newKind)
{
    if (vp->isObject()) {
        RootedObject obj(cx, &vp->toObject());
        obj = DeepCloneObjectLiteral(cx, obj, newKind);
        if (!obj)
            return false;
        vp->setObject(*obj);
    } else {
        cx->markAtomValue(*vp);
    }
    return true;
}

JSObject*
js::DeepCloneObjectLiteral(JSContext* cx, HandleObject obj, NewObjectKind newKind)
{
    /* NB: Keep this in sync with XDRObjectLiteral. */
    MOZ_ASSERT_IF(obj->isSingleton(),
                  cx->realm()->behaviors().getSingletonsAsTemplates());
    MOZ_ASSERT(obj->is<PlainObject>() || obj->is<UnboxedPlainObject>() ||
               obj->is<ArrayObject>());
    MOZ_ASSERT(newKind != SingletonObject);

    if (obj->is<ArrayObject>()) {
        Rooted<GCVector<Value>> values(cx, GCVector<Value>(cx));
        if (!GetScriptArrayObjectElements(obj.as<ArrayObject>(), &values))
            return nullptr;

        // Deep clone any elements.
        for (uint32_t i = 0; i < values.length(); ++i) {
            if (!DeepCloneValue(cx, values[i].address(), newKind))
                return nullptr;
        }

        ObjectGroup::NewArrayKind arrayKind = ObjectGroup::NewArrayKind::Normal;
        if (obj->is<ArrayObject>() && obj->as<ArrayObject>().denseElementsAreCopyOnWrite())
            arrayKind = ObjectGroup::NewArrayKind::CopyOnWrite;

        return ObjectGroup::newArrayObject(cx, values.begin(), values.length(), newKind,
                                           arrayKind);
    }

    Rooted<IdValueVector> properties(cx, IdValueVector(cx));
    if (!GetScriptPlainObjectProperties(obj, &properties))
        return nullptr;

    for (size_t i = 0; i < properties.length(); i++) {
        cx->markId(properties[i].get().id);
        if (!DeepCloneValue(cx, &properties[i].get().value, newKind))
            return nullptr;
    }

    if (obj->isSingleton())
        newKind = SingletonObject;

    return ObjectGroup::newPlainObject(cx, properties.begin(), properties.length(), newKind);
}

static bool
InitializePropertiesFromCompatibleNativeObject(JSContext* cx,
                                               HandleNativeObject dst,
                                               HandleNativeObject src)
{
    assertSameCompartment(cx, src, dst);
    MOZ_ASSERT(src->getClass() == dst->getClass());
    MOZ_ASSERT(dst->lastProperty()->getObjectFlags() == 0);
    MOZ_ASSERT(!src->isSingleton());
    MOZ_ASSERT(src->numFixedSlots() == dst->numFixedSlots());

    if (!dst->ensureElements(cx, src->getDenseInitializedLength()))
        return false;

    uint32_t initialized = src->getDenseInitializedLength();
    for (uint32_t i = 0; i < initialized; ++i) {
        dst->setDenseInitializedLength(i + 1);
        dst->initDenseElement(i, src->getDenseElement(i));
    }

    MOZ_ASSERT(!src->hasPrivate());
    RootedShape shape(cx);
    if (src->staticPrototype() == dst->staticPrototype()) {
        shape = src->lastProperty();
    } else {
        // We need to generate a new shape for dst that has dst's proto but all
        // the property information from src.  Note that we asserted above that
        // dst's object flags are 0.
        shape = EmptyShape::getInitialShape(cx, dst->getClass(), dst->taggedProto(),
                                            dst->numFixedSlots(), 0);
        if (!shape)
            return false;

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

        for (Shape* shapeToClone : shapes) {
            Rooted<StackShape> child(cx, StackShape(shapeToClone));
            shape = cx->zone()->propertyTree().getChild(cx, shape, child);
            if (!shape)
                return false;
        }
    }
    size_t span = shape->slotSpan();
    if (!dst->setLastProperty(cx, shape))
        return false;
    for (size_t i = JSCLASS_RESERVED_SLOTS(src->getClass()); i < span; i++)
        dst->setSlot(i, src->getSlot(i));

    return true;
}

JS_FRIEND_API(bool)
JS_InitializePropertiesFromCompatibleNativeObject(JSContext* cx,
                                                  HandleObject dst,
                                                  HandleObject src)
{
    return InitializePropertiesFromCompatibleNativeObject(cx,
                                                          dst.as<NativeObject>(),
                                                          src.as<NativeObject>());
}

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

    JSContext* cx = xdr->cx();
    assertSameCompartment(cx, obj);

    // Distinguish between objects and array classes.
    uint32_t isArray = 0;
    {
        if (mode == XDR_ENCODE) {
            MOZ_ASSERT(obj->is<PlainObject>() ||
                       obj->is<UnboxedPlainObject>() ||
                       obj->is<ArrayObject>());
            isArray = obj->is<ArrayObject>() ? 1 : 0;
        }

        MOZ_TRY(xdr->codeUint32(&isArray));
    }

    RootedValue tmpValue(cx), tmpIdValue(cx);
    RootedId tmpId(cx);

    if (isArray) {
        Rooted<GCVector<Value>> values(cx, GCVector<Value>(cx));
        if (mode == XDR_ENCODE) {
            RootedArrayObject arr(cx, &obj->as<ArrayObject>());
            if (!GetScriptArrayObjectElements(arr, &values))
                return xdr->fail(JS::TranscodeResult_Throw);
        }

        uint32_t initialized;
        if (mode == XDR_ENCODE)
            initialized = values.length();
        MOZ_TRY(xdr->codeUint32(&initialized));
        if (mode == XDR_DECODE && !values.appendN(MagicValue(JS_ELEMENTS_HOLE), initialized))
            return xdr->fail(JS::TranscodeResult_Throw);

        // Recursively copy dense elements.
        for (unsigned i = 0; i < initialized; i++)
            MOZ_TRY(XDRScriptConst(xdr, values[i]));

        uint32_t copyOnWrite;
        if (mode == XDR_ENCODE) {
            copyOnWrite = obj->is<ArrayObject>() &&
                          obj->as<ArrayObject>().denseElementsAreCopyOnWrite();
        }
        MOZ_TRY(xdr->codeUint32(&copyOnWrite));

        if (mode == XDR_DECODE) {
            ObjectGroup::NewArrayKind arrayKind = copyOnWrite
                                                  ? ObjectGroup::NewArrayKind::CopyOnWrite
                                                  : ObjectGroup::NewArrayKind::Normal;
            obj.set(ObjectGroup::newArrayObject(cx, values.begin(), values.length(),
                                                TenuredObject, arrayKind));
            if (!obj)
                return xdr->fail(JS::TranscodeResult_Throw);
        }

        return Ok();
    }

    // Code the properties in the object.
    Rooted<IdValueVector> properties(cx, IdValueVector(cx));
    if (mode == XDR_ENCODE && !GetScriptPlainObjectProperties(obj, &properties))
        return xdr->fail(JS::TranscodeResult_Throw);

    uint32_t nproperties = properties.length();
    MOZ_TRY(xdr->codeUint32(&nproperties));

    if (mode == XDR_DECODE && !properties.appendN(IdValuePair(), nproperties))
        return xdr->fail(JS::TranscodeResult_Throw);

    for (size_t i = 0; i < nproperties; i++) {
        if (mode == XDR_ENCODE) {
            tmpIdValue = IdToValue(properties[i].get().id);
            tmpValue = properties[i].get().value;
        }

        MOZ_TRY(XDRScriptConst(xdr, &tmpIdValue));
        MOZ_TRY(XDRScriptConst(xdr, &tmpValue));

        if (mode == XDR_DECODE) {
            if (!ValueToId<CanGC>(cx, tmpIdValue, &tmpId))
                return xdr->fail(JS::TranscodeResult_Throw);
            properties[i].get().id = tmpId;
            properties[i].get().value = tmpValue;
        }
    }

    // Code whether the object is a singleton.
    uint32_t isSingleton;
    if (mode == XDR_ENCODE)
        isSingleton = obj->isSingleton() ? 1 : 0;
    MOZ_TRY(xdr->codeUint32(&isSingleton));

    if (mode == XDR_DECODE) {
        NewObjectKind newKind = isSingleton ? SingletonObject : TenuredObject;
        obj.set(ObjectGroup::newPlainObject(cx, properties.begin(), properties.length(), newKind));
        if (!obj)
            return xdr->fail(JS::TranscodeResult_Throw);
    }

    return Ok();
}

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

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

/* static */ bool
NativeObject::fillInAfterSwap(JSContext* cx, HandleNativeObject obj,
                              const Vector<Value>& values, void* priv)
{
    // This object has just been swapped with some other object, and its shape
    // no longer reflects its allocated size. Correct this information and
    // fill the slots in with the specified values.
    MOZ_ASSERT(obj->slotSpan() == values.length());

    // Make sure the shape's numFixedSlots() is correct.
    size_t nfixed = gc::GetGCKindSlots(obj->asTenured().getAllocKind(), obj->getClass());
    if (nfixed != obj->shape()->numFixedSlots()) {
        if (!NativeObject::generateOwnShape(cx, obj))
            return false;
        obj->shape()->setNumFixedSlots(nfixed);
    }

    if (obj->hasPrivate())
        obj->setPrivate(priv);
    else
        MOZ_ASSERT(!priv);

    if (obj->slots_) {
        js_free(obj->slots_);
        obj->slots_ = nullptr;
    }

    if (size_t ndynamic = dynamicSlotsCount(nfixed, values.length(), obj->getClass())) {
        obj->slots_ = cx->zone()->pod_malloc<HeapSlot>(ndynamic);
        if (!obj->slots_)
            return false;
        Debug_SetSlotRangeToCrashOnTouch(obj->slots_, ndynamic);
    }

    obj->initSlotRange(0, values.begin(), values.length());
    return true;
}

void
JSObject::fixDictionaryShapeAfterSwap()
{
    // Dictionary shapes can point back to their containing objects, so after
    // swapping the guts of those objects fix the pointers up.
    if (isNative() && as<NativeObject>().inDictionaryMode())
        as<NativeObject>().shape()->listp = as<NativeObject>().shapePtr();
}

static MOZ_MUST_USE bool
CopyProxyValuesBeforeSwap(JSContext* cx, ProxyObject* proxy, Vector<Value>& values)
{
    MOZ_ASSERT(values.empty());

    // Remove the GCPtrValues we're about to swap from the store buffer, to
    // ensure we don't trace bogus values.
    StoreBuffer& sb = cx->runtime()->gc.storeBuffer();

    // Reserve space for the private slot and the reserved slots.
    if (!values.reserve(1 + proxy->numReservedSlots()))
        return false;

    js::detail::ProxyValueArray* valArray = js::detail::GetProxyDataLayout(proxy)->values();
    sb.unputValue(&valArray->privateSlot);
    values.infallibleAppend(valArray->privateSlot);

    for (size_t i = 0; i < proxy->numReservedSlots(); i++) {
        sb.unputValue(&valArray->reservedSlots.slots[i]);
        values.infallibleAppend(valArray->reservedSlots.slots[i]);
    }

    return true;
}

bool
ProxyObject::initExternalValueArrayAfterSwap(JSContext* cx, const Vector<Value>& values)
{
    MOZ_ASSERT(getClass()->isProxy());

    size_t nreserved = numReservedSlots();

    // |values| contains the private slot and the reserved slots.
    MOZ_ASSERT(values.length() == 1 + nreserved);

    size_t nbytes = js::detail::ProxyValueArray::sizeOf(nreserved);

    auto* valArray =
        reinterpret_cast<js::detail::ProxyValueArray*>(cx->zone()->pod_malloc<uint8_t>(nbytes));
    if (!valArray)
        return false;

    valArray->privateSlot = values[0];

    for (size_t i = 0; i < nreserved; i++)
        valArray->reservedSlots.slots[i] = values[i + 1];

    // Note: we allocate external slots iff the proxy had an inline
    // ProxyValueArray, so at this point reservedSlots points into the
    // old object and we don't have to free anything.
    data.reservedSlots = &valArray->reservedSlots;
    return true;
}

/* 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.
    MOZ_ASSERT(IsBackgroundFinalized(a->asTenured().getAllocKind()) ==
               IsBackgroundFinalized(b->asTenured().getAllocKind()));
    MOZ_ASSERT(a->compartment() == b->compartment());

    // You must have entered the objects' compartment before calling this.
    MOZ_ASSERT(cx->compartment() == a->compartment());

    AutoEnterOOMUnsafeRegion oomUnsafe;

    if (!JSObject::getGroup(cx, a))
        oomUnsafe.crash("JSObject::swap");
    if (!JSObject::getGroup(cx, b))
        oomUnsafe.crash("JSObject::swap");

    /*
     * Neither object may be in the nursery, but ensure we update any embedded
     * nursery pointers in either object.
     */
    MOZ_ASSERT(!IsInsideNursery(a) && !IsInsideNursery(b));
    cx->runtime()->gc.storeBuffer().putWholeCell(a);
    cx->runtime()->gc.storeBuffer().putWholeCell(b);

    unsigned r = NotifyGCPreSwap(a, b);

    // Do the fundamental swapping of the contents of two objects.
    MOZ_ASSERT(a->compartment() == b->compartment());
    MOZ_ASSERT(a->is<JSFunction>() == b->is<JSFunction>());

    // Don't try to swap functions with different sizes.
    MOZ_ASSERT_IF(a->is<JSFunction>(), a->tenuredSizeOfThis() == b->tenuredSizeOfThis());

    // Watch for oddball objects that have special organizational issues and
    // can't be swapped.
    MOZ_ASSERT(!a->is<RegExpObject>() && !b->is<RegExpObject>());
    MOZ_ASSERT(!a->is<ArrayObject>() && !b->is<ArrayObject>());
    MOZ_ASSERT(!a->is<ArrayBufferObject>() && !b->is<ArrayBufferObject>());
    MOZ_ASSERT(!a->is<TypedArrayObject>() && !b->is<TypedArrayObject>());
    MOZ_ASSERT(!a->is<TypedObject>() && !b->is<TypedObject>());

    // Don't swap objects that may currently be participating in shape
    // teleporting optimizations.
    //
    // See: ReshapeForProtoMutation, ReshapeForShadowedProp
    MOZ_ASSERT_IF(a->isNative() && a->isDelegate(), a->taggedProto() == TaggedProto());
    MOZ_ASSERT_IF(b->isNative() && b->isDelegate(), b->taggedProto() == TaggedProto());

    bool aIsProxyWithInlineValues =
        a->is<ProxyObject>() && a->as<ProxyObject>().usingInlineValueArray();
    bool bIsProxyWithInlineValues =
        b->is<ProxyObject>() && b->as<ProxyObject>().usingInlineValueArray();

    if (a->tenuredSizeOfThis() == b->tenuredSizeOfThis()) {
        // When both objects are the same size, just do a plain swap of their
        // contents.
        size_t size = a->tenuredSizeOfThis();

        char tmp[mozilla::tl::Max<sizeof(JSFunction), sizeof(JSObject_Slots16)>::value];
        MOZ_ASSERT(size <= sizeof(tmp));

        js_memcpy(tmp, a, size);
        js_memcpy(a, b, size);
        js_memcpy(b, tmp, size);

        a->fixDictionaryShapeAfterSwap();
        b->fixDictionaryShapeAfterSwap();

        if (aIsProxyWithInlineValues)
            b->as<ProxyObject>().setInlineValueArray();
        if (bIsProxyWithInlineValues)
            a->as<ProxyObject>().setInlineValueArray();
    } else {
        // Avoid GC in here to avoid confusing the tracing code with our
        // intermediate state.
        AutoSuppressGC suppress(cx);

        // When the objects have different sizes, they will have different
        // numbers of fixed slots before and after the swap, so the slots for
        // native objects will need to be rearranged.
        NativeObject* na = a->isNative() ? &a->as<NativeObject>() : nullptr;
        NativeObject* nb = b->isNative() ? &b->as<NativeObject>() : nullptr;

        // Remember the original values from the objects.
        Vector<Value> avals(cx);
        void* apriv = nullptr;
        if (na) {
            apriv = na->hasPrivate() ? na->getPrivate() : nullptr;
            for (size_t i = 0; i < na->slotSpan(); i++) {
                if (!avals.append(na->getSlot(i)))
                    oomUnsafe.crash("JSObject::swap");
            }
        }
        Vector<Value> bvals(cx);
        void* bpriv = nullptr;
        if (nb) {
            bpriv = nb->hasPrivate() ? nb->getPrivate() : nullptr;
            for (size_t i = 0; i < nb->slotSpan(); i++) {
                if (!bvals.append(nb->getSlot(i)))
                    oomUnsafe.crash("JSObject::swap");
            }
        }

        // Do the same for proxies storing ProxyValueArray inline.
        ProxyObject* proxyA = a->is<ProxyObject>() ? &a->as<ProxyObject>() : nullptr;
        ProxyObject* proxyB = b->is<ProxyObject>() ? &b->as<ProxyObject>() : nullptr;

        if (aIsProxyWithInlineValues) {
            if (!CopyProxyValuesBeforeSwap(cx, proxyA, avals))
                oomUnsafe.crash("CopyProxyValuesBeforeSwap");
        }
        if (bIsProxyWithInlineValues) {
            if (!CopyProxyValuesBeforeSwap(cx, proxyB, bvals))
                oomUnsafe.crash("CopyProxyValuesBeforeSwap");
        }

        // Swap the main fields of the objects, whether they are native objects or proxies.
        char tmp[sizeof(JSObject_Slots0)];
        js_memcpy(&tmp, a, sizeof tmp);
        js_memcpy(a, b, sizeof tmp);
        js_memcpy(b, &tmp, sizeof tmp);

        a->fixDictionaryShapeAfterSwap();
        b->fixDictionaryShapeAfterSwap();

        if (na) {
            if (!NativeObject::fillInAfterSwap(cx, b.as<NativeObject>(), avals, apriv))
                oomUnsafe.crash("fillInAfterSwap");
        }
        if (nb) {
            if (!NativeObject::fillInAfterSwap(cx, a.as<NativeObject>(), bvals, bpriv))
                oomUnsafe.crash("fillInAfterSwap");
        }
        if (aIsProxyWithInlineValues) {
            if (!b->as<ProxyObject>().initExternalValueArrayAfterSwap(cx, avals))
                oomUnsafe.crash("initExternalValueArray");
        }
        if (bIsProxyWithInlineValues) {
            if (!a->as<ProxyObject>().initExternalValueArrayAfterSwap(cx, bvals))
                oomUnsafe.crash("initExternalValueArray");
        }
    }

    // Swapping the contents of two objects invalidates type sets which contain
    // either of the objects, so mark all such sets as unknown.
    MarkObjectGroupUnknownProperties(cx, a->group());
    MarkObjectGroupUnknownProperties(cx, b->group());

    /*
     * 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.
     */
    JS::Zone* zone = a->zone();
    if (zone->needsIncrementalBarrier()) {
        a->traceChildren(zone->barrierTracer());
        b->traceChildren(zone->barrierTracer());
    }

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

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

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

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

static NativeObject*
DefineConstructorAndPrototype(JSContext* cx, HandleObject obj, JSProtoKey key, HandleAtom atom,
                              HandleObject protoProto, const Class* clasp,
                              Native constructor, unsigned nargs,
                              const JSPropertySpec* ps, const JSFunctionSpec* fs,
                              const JSPropertySpec* static_ps, const JSFunctionSpec* static_fs,
                              NativeObject** ctorp)
{
    /*
     * 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 won't let us use protoProto as the proto.
     */
    RootedNativeObject proto(cx, NewNativeObjectWithClassProto(cx, clasp, protoProto, SingletonObject));
    if (!proto)
        return nullptr;

    /* After this point, control must exit via label bad or out. */
    RootedNativeObject 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, atom, value, attrs, named))
                goto bad;
        }

        ctor = proto;
    } else {
        RootedFunction fun(cx, NewNativeConstructor(cx, constructor, nargs, atom));
        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, 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 && !JSObject::splicePrototype(cx, ctor, 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) {
        ObjectOpResult ignored;
        RootedId id(cx, AtomToId(atom));

        // XXX FIXME - absurd to call this here; instead define the property last.
        DeleteProperty(cx, obj, id, ignored);
    }
    if (cached)
        ClearClassObject(obj, key);
    return nullptr;
}

NativeObject*
js::InitClass(JSContext* cx, HandleObject obj, HandleObject protoProto_,
              const Class* clasp, Native constructor, unsigned nargs,
              const JSPropertySpec* ps, const JSFunctionSpec* fs,
              const JSPropertySpec* static_ps, const JSFunctionSpec* static_fs,
              NativeObject** ctorp)
{
    RootedObject protoProto(cx, protoProto_);

    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) {
        protoProto = GlobalObject::getOrCreatePrototype(cx, JSProto_Object);
        if (!protoProto)
            return nullptr;
    }

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

void
JSObject::fixupAfterMovingGC()
{
    // For copy-on-write objects that don't own their elements, fix up the
    // elements pointer if it points to inline elements in the owning object.
    if (is<NativeObject>()) {
        NativeObject& obj = as<NativeObject>();
        if (obj.denseElementsAreCopyOnWrite()) {
            NativeObject* owner = obj.getElementsHeader()->ownerObject();
            // Get the new owner pointer but don't call MaybeForwarded as we
            // don't need to access the object's shape.
            if (IsForwarded(owner))
                owner = Forwarded(owner);
            if (owner != &obj && owner->hasFixedElements())
                obj.elements_ = owner->getElementsHeader()->elements();
            MOZ_ASSERT(!IsForwarded(obj.getElementsHeader()->ownerObject().get()));
        }
    }
}

static bool
ReshapeForProtoMutation(JSContext* cx, HandleObject obj)
{
    // To avoid the JIT guarding on each prototype in chain to detect prototype
    // mutation, we can instead reshape the rest of the proto chain such that a
    // guard on any of them is sufficient. To avoid excessive reshaping and
    // invalidation, we apply heuristics to decide when to apply this and when
    // to require a guard.
    //
    // Heuristics:
    //  - Always reshape singleton objects. This historically avoided
    //    de-optimizing in cases that compiler doesn't support
    //    uncacheable-proto. TODO: Revisit if this is a good idea.
    //  - Other objects instead set UNCACHEABLE_PROTO flag on shape to avoid
    //    creating too many private shape copies.
    //  - Only propegate along proto chain if we are mark DELEGATE. This avoids
    //    reshaping in normal object access cases.
    //
    // NOTE: We only handle NativeObjects and don't propegate reshapes through
    //       any non-native objects on the chain.
    //
    // See Also:
    //  - GeneratePrototypeGuards
    //  - GeneratePrototypeHoleGuards
    //  - ObjectGroup::defaultNewGroup

    RootedObject pobj(cx, obj);

    while (pobj && pobj->isNative()) {
        if (pobj->isSingleton()) {
            // If object was converted to a singleton it should have cleared
            // any UNCACHEABLE_PROTO flags.
            MOZ_ASSERT(!pobj->hasUncacheableProto());

            if (!NativeObject::reshapeForProtoMutation(cx, pobj.as<NativeObject>()))
                return false;
        } else {
            if (!JSObject::setUncacheableProto(cx, pobj))
                return false;
        }

        if (!obj->isDelegate())
            break;

        pobj = pobj->staticPrototype();
    }

    return true;
}

static bool
SetClassAndProto(JSContext* cx, HandleObject obj,
                 const Class* clasp, Handle<js::TaggedProto> proto)
{
    // Regenerate object shape (and possibly prototype shape) to invalidate JIT
    // code that is affected by a prototype mutation.
    if (!ReshapeForProtoMutation(cx, obj))
        return false;

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

    if (obj->isSingleton()) {
        /*
         * Just splice the prototype, but mark the properties as unknown for
         * consistent behavior.
         */
        if (!JSObject::splicePrototype(cx, obj, clasp, proto))
            return false;
        MarkObjectGroupUnknownProperties(cx, obj->group());
        return true;
    }

    RootedObjectGroup oldGroup(cx, obj->group());

    ObjectGroup* newGroup;
    if (oldGroup->maybeInterpretedFunction()) {
        // We're changing the group/proto of a scripted function. Create a new
        // group so we can keep track of the interpreted function for Ion
        // inlining.
        MOZ_ASSERT(obj->is<JSFunction>());
        newGroup = ObjectGroupRealm::makeGroup(cx, &JSFunction::class_, proto);
        if (!newGroup)
            return false;
        newGroup->setInterpretedFunction(oldGroup->maybeInterpretedFunction());
    } else {
        newGroup = ObjectGroup::defaultNewGroup(cx, clasp, proto);
        if (!newGroup)
            return false;
    }

    obj->setGroup(newGroup);

    // Add the object's property types to the new group.
    AutoSweepObjectGroup sweep(newGroup);
    if (!newGroup->unknownProperties(sweep)) {
        if (obj->isNative())
            AddPropertyTypesAfterProtoChange(cx, &obj->as<NativeObject>(), oldGroup);
        else
            MarkObjectGroupUnknownProperties(cx, newGroup);
    }

    // Type sets containing this object will contain the old group but not the
    // new group of the object, so we need to treat all such type sets as
    // unknown.
    MarkObjectGroupUnknownProperties(cx, oldGroup);

    return true;
}

/* static */ bool
JSObject::changeToSingleton(JSContext* cx, HandleObject obj)
{
    MOZ_ASSERT(!obj->isSingleton());

    MarkObjectGroupUnknownProperties(cx, obj->group());

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

    obj->group_ = group;
    return true;
}

/**
 * Returns the original Object.prototype from the embedding-provided incumbent
 * global.
 *
 * Really, we want the incumbent global itself so we can pass it to other
 * embedding hooks which need it. Specifically, the enqueue promise hook
 * takes an incumbent global so it can set that on the PromiseCallbackJob
 * it creates.
 *
 * The reason for not just returning the global itself is that we'd need to
 * wrap it into the current compartment, and later unwrap it. Unwrapping
 * globals is tricky, though: we might accidentally unwrap through an inner
 * to its outer window and end up with the wrong global. Plain objects don't
 * have this problem, so we use the global's Object.prototype. The code using
 * it - e.g. EnqueuePromiseReactionJob - can then unwrap the object and get
 * its global without fear of unwrapping too far.
 */
bool
js::GetObjectFromIncumbentGlobal(JSContext* cx, MutableHandleObject obj)
{
    RootedObject globalObj(cx, cx->runtime()->getIncumbentGlobal(cx));
    if (!globalObj) {
        obj.set(nullptr);
        return true;
    }

    {
        AutoRealm ar(cx, globalObj);
        Handle<GlobalObject*> global = globalObj.as<GlobalObject>();
        obj.set(GlobalObject::getOrCreateObjectPrototype(cx, global));
        if (!obj)
            return false;
    }

    // The object might be from a different compartment, so wrap it.
    if (obj && !cx->compartment()->wrap(cx, obj))
        return false;

    return true;
}

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

JSProtoKey
JS::IdentifyStandardInstance(JSObject* obj)
{
    // Note: The prototype shares its JSClass with instances.
    MOZ_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.
    MOZ_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->as<JSFunction>().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::LookupProperty(JSContext* cx, HandleObject obj, js::HandleId id,
                   MutableHandleObject objp, MutableHandle<PropertyResult> propp)
{
    if (LookupPropertyOp op = obj->getOpsLookupProperty())
        return op(cx, obj, id, objp, propp);
    return LookupPropertyInline<CanGC>(cx, obj.as<NativeObject>(), id, objp, propp);
}

bool
js::LookupName(JSContext* cx, HandlePropertyName name, HandleObject envChain,
               MutableHandleObject objp, MutableHandleObject pobjp, MutableHandle<PropertyResult> propp)
{
    RootedId id(cx, NameToId(name));

    for (RootedObject env(cx, envChain); env; env = env->enclosingEnvironment()) {
        if (!LookupProperty(cx, env, id, pobjp, propp))
            return false;
        if (propp) {
            objp.set(env);
            return true;
        }
    }

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

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

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

    for (JSObject* env = envChain; env; env = env->enclosingEnvironment()) {
        if (env->getOpsLookupProperty())
            return false;
        if (!LookupPropertyInline<NoGC>(cx, &env->as<NativeObject>(), NameToId(name), pobjp, propp))
            return false;
        if (*propp) {
            *objp = env;
            return true;
        }
    }

    return true;
}

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

    RootedObject pobj(cx);
    Rooted<PropertyResult> prop(cx);

    RootedObject env(cx, envChain);
    for (; !env->is<GlobalObject>(); env = env->enclosingEnvironment()) {
        if (!LookupProperty(cx, env, id, &pobj, &prop))
            return false;
        if (prop)
            break;
    }

    objp.set(env);
    return true;
}

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

    RootedObject pobj(cx);
    Rooted<PropertyResult> prop(cx);

    RootedObject env(cx, envChain);
    for (; !env->isUnqualifiedVarObj(); env = env->enclosingEnvironment()) {
        if (!LookupProperty(cx, env, id, &pobj, &prop))
            return false;
        if (prop)
            break;
    }

    // See note above RuntimeLexicalErrorObject.
    if (pobj == env) {
        bool isTDZ = false;
        if (prop && name != cx->names().dotThis) {
            // Treat Debugger environments specially for TDZ checks, as they
            // look like non-native environments but in fact wrap native
            // environments.
            if (env->is<DebugEnvironmentProxy>()) {
                RootedValue v(cx);
                Rooted<DebugEnvironmentProxy*> envProxy(cx, &env->as<DebugEnvironmentProxy>());
                if (!DebugEnvironmentProxy::getMaybeSentinelValue(cx, envProxy, id, &v))
                    return false;
                isTDZ = IsUninitializedLexical(v);
            } else {
                isTDZ = IsUninitializedLexicalSlot(env, prop);
            }
        }

        if (isTDZ) {
            env = RuntimeLexicalErrorObject::create(cx, env, JSMSG_UNINITIALIZED_LEXICAL);
            if (!env)
                return false;
        } else if (env->is<LexicalEnvironmentObject>() && !prop.shape()->writable()) {
            // Assigning to a named lambda callee name is a no-op in sloppy mode.
            Rooted<LexicalEnvironmentObject*> lexicalEnv(cx, &env->as<LexicalEnvironmentObject>());
            if (lexicalEnv->isExtensible() ||
                lexicalEnv->scope().kind() != ScopeKind::NamedLambda)
            {
                MOZ_ASSERT(name != cx->names().dotThis);
                env = RuntimeLexicalErrorObject::create(cx, env, JSMSG_BAD_CONST_ASSIGN);
                if (!env)
                    return false;
            }
        }
    }

    objp.set(env);
    return true;
}

bool
js::HasOwnProperty(JSContext* cx, HandleObject obj, HandleId id, bool* result)
{
    if (obj->is<ProxyObject>())
        return Proxy::hasOwn(cx, obj, id, result);

    if (GetOwnPropertyOp op = obj->getOpsGetOwnPropertyDescriptor()) {
        Rooted<PropertyDescriptor> desc(cx);
        if (!op(cx, obj, id, &desc))
            return false;
        *result = !!desc.object();
        return true;
    }

    Rooted<PropertyResult> prop(cx);
    if (!NativeLookupOwnProperty<CanGC>(cx, obj.as<NativeObject>(), id, &prop))
        return false;
    *result = prop.isFound();
    return true;
}

bool
js::LookupPropertyPure(JSContext* cx, JSObject* obj, jsid id, JSObject** objp,
                       PropertyResult* propp)
{
    bool isTypedArrayOutOfRange = false;
    do {
        if (!LookupOwnPropertyPure(cx, obj, id, propp, &isTypedArrayOutOfRange))
            return false;

        if (*propp) {
            *objp = obj;
            return true;
        }

        if (isTypedArrayOutOfRange) {
            *objp = nullptr;
            return true;
        }

        obj = obj->staticPrototype();
    } while (obj);

    *objp = nullptr;
    propp->setNotFound();
    return true;
}

bool
js::LookupOwnPropertyPure(JSContext* cx, JSObject* obj, jsid id, PropertyResult* propp,
                          bool* isTypedArrayOutOfRange /* = nullptr */)
{
    JS::AutoCheckCannotGC nogc;
    if (isTypedArrayOutOfRange)
        *isTypedArrayOutOfRange = false;

    if (obj->isNative()) {
        // Search for a native dense element, typed array element, or property.

        if (JSID_IS_INT(id) && obj->as<NativeObject>().containsDenseElement(JSID_TO_INT(id))) {
            propp->setDenseOrTypedArrayElement();
            return true;
        }

        if (obj->is<TypedArrayObject>()) {
            uint64_t index;
            if (IsTypedArrayIndex(id, &index)) {
                if (index < obj->as<TypedArrayObject>().length()) {
                    propp->setDenseOrTypedArrayElement();
                } else {
                    propp->setNotFound();
                    if (isTypedArrayOutOfRange)
                        *isTypedArrayOutOfRange = true;
                }
                return true;
            }
        }

        if (Shape* shape = obj->as<NativeObject>().lookupPure(id)) {
            propp->setNativeProperty(shape);
            return true;
        }

        // Fail if there's a resolve hook, unless the mayResolve hook tells
        // us the resolve hook won't define a property with this id.
        if (ClassMayResolveId(cx->names(), obj->getClass(), id, obj))
            return false;
    } else if (obj->is<UnboxedPlainObject>()) {
        if (obj->as<UnboxedPlainObject>().containsUnboxedOrExpandoProperty(cx, id)) {
            propp->setNonNativeProperty();
            return true;
        }
    } else if (obj->is<TypedObject>()) {
        if (obj->as<TypedObject>().typeDescr().hasProperty(cx->names(), id)) {
            propp->setNonNativeProperty();
            return true;
        }
    } else {
        return false;
    }

    propp->setNotFound();
    return true;
}

static inline bool
NativeGetPureInline(NativeObject* pobj, jsid id, PropertyResult prop, Value* vp)
{
    if (prop.isDenseOrTypedArrayElement()) {
        // For simplicity we ignore the TypedArray with string index case.
        if (!JSID_IS_INT(id))
            return false;

        *vp = pobj->getDenseOrTypedArrayElement(JSID_TO_INT(id));
        return true;
    }

    // Fail if we have a custom getter.
    Shape* shape = prop.shape();
    if (!shape->isDataProperty())
        return false;

    *vp = pobj->getSlot(shape->slot());
    MOZ_ASSERT(!vp->isMagic());
    return true;
}

bool
js::GetPropertyPure(JSContext* cx, JSObject* obj, jsid id, Value* vp)
{
    JSObject* pobj;
    PropertyResult prop;
    if (!LookupPropertyPure(cx, obj, id, &pobj, &prop))
        return false;

    if (!prop) {
        vp->setUndefined();
        return true;
    }

    return pobj->isNative() && NativeGetPureInline(&pobj->as<NativeObject>(), id, prop, vp);
}

bool
js::GetOwnPropertyPure(JSContext* cx, JSObject* obj, jsid id, Value* vp)
{
    PropertyResult prop;
    if (!LookupOwnPropertyPure(cx, obj, id, &prop))
        return false;

    if (!prop) {
        vp->setUndefined();
        return true;
    }

    return obj->isNative() && NativeGetPureInline(&obj->as<NativeObject>(), id, prop, vp);
}

static inline bool
NativeGetGetterPureInline(PropertyResult prop, JSFunction** fp)
{
    if (!prop.isDenseOrTypedArrayElement() && prop.shape()->hasGetterObject()) {
        Shape* shape = prop.shape();
        if (shape->getterObject()->is<JSFunction>()) {
            *fp = &shape->getterObject()->as<JSFunction>();
            return true;
        }
    }

    *fp = nullptr;
    return true;
}

bool
js::GetGetterPure(JSContext* cx, JSObject* obj, jsid id, JSFunction** fp)
{
    /* Just like GetPropertyPure, but get getter function, without invoking
     * it. */
    JSObject* pobj;
    PropertyResult prop;
    if (!LookupPropertyPure(cx, obj, id, &pobj, &prop))
        return false;

    if (!prop) {
        *fp = nullptr;
        return true;
    }

    return prop.isNativeProperty() && NativeGetGetterPureInline(prop, fp);
}

bool
js::GetOwnGetterPure(JSContext* cx, JSObject* obj, jsid id, JSFunction** fp)
{
    JS::AutoCheckCannotGC nogc;
    PropertyResult prop;
    if (!LookupOwnPropertyPure(cx, obj, id, &prop))
        return false;

    if (!prop) {
        *fp = nullptr;
        return true;
    }

    return prop.isNativeProperty() && NativeGetGetterPureInline(prop, fp);
}

bool
js::GetOwnNativeGetterPure(JSContext* cx, JSObject* obj, jsid id, JSNative* native)
{
    JS::AutoCheckCannotGC nogc;
    *native = nullptr;
    PropertyResult prop;
    if (!LookupOwnPropertyPure(cx, obj, id, &prop))
        return false;

    if (!prop || prop.isDenseOrTypedArrayElement() || !prop.shape()->hasGetterObject())
        return true;

    JSObject* getterObj = prop.shape()->getterObject();
    if (!getterObj->is<JSFunction>())
        return true;

    JSFunction* getter = &getterObj->as<JSFunction>();
    if (!getter->isNative())
        return true;

    *native = getter->native();
    return true;
}

bool
js::HasOwnDataPropertyPure(JSContext* cx, JSObject* obj, jsid id, bool* result)
{
    PropertyResult prop;
    if (!LookupOwnPropertyPure(cx, obj, id, &prop))
        return false;

    *result = prop && !prop.isDenseOrTypedArrayElement() &&
              prop.shape()->isDataProperty();
    return true;
}

bool
js::GetPrototypeIfOrdinary(JSContext* cx, HandleObject obj, bool* isOrdinary,
                           MutableHandleObject protop)
{
    if (obj->is<js::ProxyObject>())
        return js::Proxy::getPrototypeIfOrdinary(cx, obj, isOrdinary, protop);

    *isOrdinary = true;
    protop.set(obj->staticPrototype());
    return true;
}

/*** ES6 standard internal methods ***************************************************************/

bool
js::SetPrototype(JSContext* cx, HandleObject obj, HandleObject proto, JS::ObjectOpResult& result)
{
    // The proxy trap subsystem fully handles prototype-setting for proxies
    // with dynamic [[Prototype]]s.
    if (obj->hasDynamicPrototype()) {
        MOZ_ASSERT(obj->is<ProxyObject>());
        return Proxy::setPrototype(cx, obj, proto, result);
    }

    /*
     * ES6 9.1.2 step 3-4 if |obj.[[Prototype]]| has SameValue as |proto| return true.
     * Since the values in question are objects, we can just compare pointers.
     */
    if (proto == obj->staticPrototype())
        return result.succeed();

    /* Disallow mutation of immutable [[Prototype]]s. */
    if (obj->staticPrototypeIsImmutable())
        return result.fail(JSMSG_CANT_SET_PROTO);

    /*
     * Disallow mutating the [[Prototype]] on ArrayBuffer objects, which
     * due to their complicated delegate-object shenanigans can't easily
     * have a mutable [[Prototype]].
     */
    if (obj->is<ArrayBufferObject>()) {
        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_CANT_SET_PROTO_OF,
                                  "incompatible ArrayBuffer");
        return false;
    }

    /*
     * Disallow mutating the [[Prototype]] on Typed Objects, per the spec.
     */
    if (obj->is<TypedObject>()) {
        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_CANT_SET_PROTO_OF,
                                  "incompatible TypedObject");
        return false;
    }

    /* ES6 9.1.2 step 5 forbids changing [[Prototype]] if not [[Extensible]]. */
    bool extensible;
    if (!IsExtensible(cx, obj, &extensible))
        return false;
    if (!extensible)
        return result.fail(JSMSG_CANT_SET_PROTO);

    // If this is a global object, resolve the Object class so that its
    // [[Prototype]] chain is always properly immutable, even in the presence
    // of lazy standard classes.
    if (obj->is<GlobalObject>()) {
        Handle<GlobalObject*> global = obj.as<GlobalObject>();
        if (!GlobalObject::ensureConstructor(cx, global, JSProto_Object))
            return false;
    }

    /*
     * ES6 9.1.2 step 6 forbids generating cyclical prototype chains. But we
     * have to do this comparison on the observable WindowProxy, not on the
     * possibly-Window object we're setting the proto on.
     */
    RootedObject objMaybeWindowProxy(cx, ToWindowProxyIfWindow(obj));
    RootedObject obj2(cx, proto);
    while (obj2) {
        MOZ_ASSERT(!IsWindow(obj2));
        if (obj2 == objMaybeWindowProxy)
            return result.fail(JSMSG_CANT_SET_PROTO_CYCLE);

        bool isOrdinary;
        if (!GetPrototypeIfOrdinary(cx, obj2, &isOrdinary, &obj2))
            return false;
        if (!isOrdinary)
            break;
    }

    // Convert unboxed objects to their native representations before changing
    // their prototype/group, as they depend on the group for their layout.
    if (!MaybeConvertUnboxedObjectToNative(cx, obj))
        return false;

    Rooted<TaggedProto> taggedProto(cx, TaggedProto(proto));
    if (!SetClassAndProto(cx, obj, obj->getClass(), taggedProto))
        return false;

    return result.succeed();
}

bool
js::SetPrototype(JSContext* cx, HandleObject obj, HandleObject proto)
{
    ObjectOpResult result;
    return SetPrototype(cx, obj, proto, result) && result.checkStrict(cx, obj);
}

bool
js::PreventExtensions(JSContext* cx, HandleObject obj, ObjectOpResult& result)
{
    if (obj->is<ProxyObject>())
        return js::Proxy::preventExtensions(cx, obj, result);

    if (!obj->nonProxyIsExtensible())
        return result.succeed();

    if (!MaybeConvertUnboxedObjectToNative(cx, obj))
        return false;

    if (obj->isNative()) {
        // Force lazy properties to be resolved.
        if (!ResolveLazyProperties(cx, obj.as<NativeObject>()))
            return false;

        // Prepare the elements. We have to do this before we mark the object
        // non-extensible; that's fine because these changes are not observable.
        if (!ObjectElements::PreventExtensions(cx, &obj->as<NativeObject>()))
            return false;
    }

    if (!JSObject::setFlags(cx, obj, BaseShape::NOT_EXTENSIBLE, JSObject::GENERATE_SHAPE))
        return false;

    return result.succeed();
}

bool
js::PreventExtensions(JSContext* cx, HandleObject obj)
{
    ObjectOpResult result;
    return PreventExtensions(cx, obj, result) && result.checkStrict(cx, obj);
}

bool
js::GetOwnPropertyDescriptor(JSContext* cx, HandleObject obj, HandleId id,
                             MutableHandle<PropertyDescriptor> desc)
{
    if (GetOwnPropertyOp op = obj->getOpsGetOwnPropertyDescriptor()) {
        bool ok = op(cx, obj, id, desc);
        if (ok)
            desc.assertCompleteIfFound();
        return ok;
    }

    return NativeGetOwnPropertyDescriptor(cx, obj.as<NativeObject>(), id, desc);
}

bool
js::DefineProperty(JSContext* cx, HandleObject obj, HandleId id, Handle<PropertyDescriptor> desc)
{
    ObjectOpResult result;
    return DefineProperty(cx, obj, id, desc, result) &&
           result.checkStrict(cx, obj, id);
}

bool
js::DefineProperty(JSContext* cx, HandleObject obj, HandleId id, Handle<PropertyDescriptor> desc,
                   ObjectOpResult& result)
{
    desc.assertValid();
    if (DefinePropertyOp op = obj->getOpsDefineProperty())
        return op(cx, obj, id, desc, result);
    return NativeDefineProperty(cx, obj.as<NativeObject>(), id, desc, result);
}

bool
js::DefineAccessorProperty(JSContext* cx, HandleObject obj, HandleId id,
                           HandleObject getter, HandleObject setter, unsigned attrs,
                           ObjectOpResult& result)
{
    Rooted<PropertyDescriptor> desc(cx);

    {
        GetterOp getterOp = JS_DATA_TO_FUNC_PTR(GetterOp, getter.get());
        SetterOp setterOp = JS_DATA_TO_FUNC_PTR(SetterOp, setter.get());
        desc.initFields(nullptr, UndefinedHandleValue, attrs, getterOp, setterOp);
    }

    if (DefinePropertyOp op = obj->getOpsDefineProperty()) {
        MOZ_ASSERT(!cx->helperThread());
        return op(cx, obj, id, desc, result);
    }
    return NativeDefineProperty(cx, obj.as<NativeObject>(), id, desc, result);
}

bool
js::DefineDataProperty(JSContext* cx, HandleObject obj, HandleId id, HandleValue value,
                       unsigned attrs, ObjectOpResult& result)
{
    Rooted<PropertyDescriptor> desc(cx);
    desc.initFields(nullptr, value, attrs, nullptr, nullptr);
    if (DefinePropertyOp op = obj->getOpsDefineProperty()) {
        MOZ_ASSERT(!cx->helperThread());
        return op(cx, obj, id, desc, result);
    }
    return NativeDefineProperty(cx, obj.as<NativeObject>(), id, desc, result);
}

bool
js::DefineDataProperty(JSContext* cx, HandleObject obj, PropertyName* name, HandleValue value,
                       unsigned attrs, ObjectOpResult& result)
{
    RootedId id(cx, NameToId(name));
    return DefineDataProperty(cx, obj, id, value, attrs, result);
}

bool
js::DefineDataElement(JSContext* cx, HandleObject obj, uint32_t index, HandleValue value,
                      unsigned attrs, ObjectOpResult& result)
{
    RootedId id(cx);
    if (!IndexToId(cx, index, &id))
        return false;
    return DefineDataProperty(cx, obj, id, value, attrs, result);
}

bool
js::DefineAccessorProperty(JSContext* cx, HandleObject obj, HandleId id,
                           HandleObject getter, HandleObject setter, unsigned attrs)
{
    ObjectOpResult result;
    if (!DefineAccessorProperty(cx, obj, id, getter, setter, attrs, result))
        return false;
    if (!result) {
        MOZ_ASSERT(!cx->helperThread());
        result.reportError(cx, obj, id);
        return false;
    }
    return true;
}

bool
js::DefineDataProperty(JSContext* cx, HandleObject obj, HandleId id, HandleValue value,
                       unsigned attrs)
{
    ObjectOpResult result;
    if (!DefineDataProperty(cx, obj, id, value, attrs, result))
        return false;
    if (!result) {
        MOZ_ASSERT(!cx->helperThread());
        result.reportError(cx, obj, id);
        return false;
    }
    return true;
}

bool
js::DefineDataProperty(JSContext* cx, HandleObject obj, PropertyName* name, HandleValue value,
                       unsigned attrs)
{
    RootedId id(cx, NameToId(name));
    return DefineDataProperty(cx, obj, id, value, attrs);
}

bool
js::DefineDataElement(JSContext* cx, HandleObject obj, uint32_t index, HandleValue value,
                      unsigned attrs)
{
    RootedId id(cx);
    if (!IndexToId(cx, index, &id))
        return false;
    return DefineDataProperty(cx, obj, id, value, attrs);
}

/*** SpiderMonkey nonstandard internal methods ***************************************************/

bool
js::SetImmutablePrototype(JSContext* cx, HandleObject obj, bool* succeeded)
{
    if (obj->hasDynamicPrototype()) {
        MOZ_ASSERT(!cx->helperThread());
        return Proxy::setImmutablePrototype(cx, obj, succeeded);
    }

    if (!JSObject::setFlags(cx, obj, BaseShape::IMMUTABLE_PROTOTYPE))
        return false;
    *succeeded = true;
    return true;
}

bool
js::GetPropertyDescriptor(JSContext* cx, HandleObject obj, HandleId id,
                          MutableHandle<PropertyDescriptor> desc)
{
    RootedObject pobj(cx);

    for (pobj = obj; pobj;) {
        if (pobj->is<ProxyObject>()) {
            bool ok = Proxy::getPropertyDescriptor(cx, pobj, id, desc);
            if (ok)
                desc.assertCompleteIfFound();
            return ok;
        }

        if (!GetOwnPropertyDescriptor(cx, pobj, id, desc))
            return false;

        if (desc.object())
            return true;

        if (!GetPrototype(cx, pobj, &pobj))
            return false;
    }

    MOZ_ASSERT(!desc.object());
    return true;
}

/* * */

extern bool
PropertySpecNameToId(JSContext* cx, const char* name, MutableHandleId id,
                     js::PinningBehavior pin = js::DoNotPinAtom);

static bool
DefineFunctionFromSpec(JSContext* cx, HandleObject obj, const JSFunctionSpec* fs, unsigned flags,
                       DefineAsIntrinsic intrinsic)
{
    RootedId id(cx);
    if (!PropertySpecNameToId(cx, fs->name, &id))
        return false;

    JSFunction* fun = NewFunctionFromSpec(cx, fs, id);
    if (!fun)
        return false;

    if (intrinsic == AsIntrinsic)
        fun->setIsIntrinsic();

    RootedValue funVal(cx, ObjectValue(*fun));
    return DefineDataProperty(cx, obj, id, funVal, flags & ~JSFUN_FLAGS_MASK);
}

bool
js::DefineFunctions(JSContext* cx, HandleObject obj, const JSFunctionSpec* fs,
                    DefineAsIntrinsic intrinsic)
{
    for (; fs->name; fs++) {
        if (!DefineFunctionFromSpec(cx, obj, fs, fs->flags, intrinsic))
            return false;
    }
    return true;
}


/*** ToPrimitive *************************************************************/

/*
 * Gets |obj[id]|.  If that value's not callable, returns true and stores an
 * object value in *vp.  If it's callable, calls it with no arguments and |obj|
 * as |this|, returning the result in *vp.
 *
 * This is a mini-abstraction for ES6 draft rev 36 (2015 Mar 17),
 * 7.1.1, second algorithm (OrdinaryToPrimitive), steps 5.a-c.
 */
static bool
MaybeCallMethod(JSContext* cx, HandleObject obj, HandleId id, MutableHandleValue vp)
{
    if (!GetProperty(cx, obj, obj, id, vp))
        return false;
    if (!IsCallable(vp)) {
        vp.setObject(*obj);
        return true;
    }

    return js::Call(cx, vp, obj, vp);
}

static bool
ReportCantConvert(JSContext* cx, unsigned errorNumber, HandleObject obj, JSType hint)
{
    const Class* clasp = obj->getClass();

    // Avoid recursive death when decompiling in ReportValueError.
    RootedString str(cx);
    if (hint == JSTYPE_STRING) {
        str = JS_AtomizeAndPinString(cx, clasp->name);
        if (!str)
            return false;
    } else {
        str = nullptr;
    }

    RootedValue val(cx, ObjectValue(*obj));
    ReportValueError(cx, errorNumber, JSDVG_SEARCH_STACK, val, str,
                     hint == JSTYPE_UNDEFINED
                     ? "primitive type"
                     : hint == JSTYPE_STRING ? "string" : "number");
    return false;
}

bool
JS::OrdinaryToPrimitive(JSContext* cx, HandleObject obj, JSType hint, MutableHandleValue vp)
{
    MOZ_ASSERT(hint == JSTYPE_NUMBER || hint == JSTYPE_STRING || hint == JSTYPE_UNDEFINED);

    Rooted<jsid> id(cx);

    const Class* clasp = obj->getClass();
    if (hint == JSTYPE_STRING) {
        id = NameToId(cx->names().toString);

        /* Optimize (new String(...)).toString(). */
        if (clasp == &StringObject::class_) {
            StringObject* nobj = &obj->as<StringObject>();
            if (HasNativeMethodPure(nobj, cx->names().toString, str_toString, cx)) {
                vp.setString(nobj->unbox());
                return true;
            }
        }

        if (!MaybeCallMethod(cx, obj, id, vp))
            return false;
        if (vp.isPrimitive())
            return true;

        id = NameToId(cx->names().valueOf);
        if (!MaybeCallMethod(cx, obj, id, vp))
            return false;
        if (vp.isPrimitive())
            return true;
    } else {
        id = NameToId(cx->names().valueOf);

        /* Optimize new String(...).valueOf(). */
        if (clasp == &StringObject::class_) {
            StringObject* nobj = &obj->as<StringObject>();
            if (HasNativeMethodPure(nobj, cx->names().valueOf, str_toString, cx)) {
                vp.setString(nobj->unbox());
                return true;
            }
        }

        /* Optimize new Number(...).valueOf(). */
        if (clasp == &NumberObject::class_) {
            NumberObject* nobj = &obj->as<NumberObject>();
            if (HasNativeMethodPure(nobj, cx->names().valueOf, num_valueOf, cx)) {
                vp.setNumber(nobj->unbox());
                return true;
            }
        }

        if (!MaybeCallMethod(cx, obj, id, vp))
            return false;
        if (vp.isPrimitive())
            return true;

        id = NameToId(cx->names().toString);
        if (!MaybeCallMethod(cx, obj, id, vp))
            return false;
        if (vp.isPrimitive())
            return true;
    }

    return ReportCantConvert(cx, JSMSG_CANT_CONVERT_TO, obj, hint);
}

bool
js::ToPrimitiveSlow(JSContext* cx, JSType preferredType, MutableHandleValue vp)
{
    // Step numbers refer to the first algorithm listed in ES6 draft rev 36
    // (2015 Mar 17) 7.1.1 ToPrimitive.
    MOZ_ASSERT(preferredType == JSTYPE_UNDEFINED ||
               preferredType == JSTYPE_STRING ||
               preferredType == JSTYPE_NUMBER);
    RootedObject obj(cx, &vp.toObject());

    // Steps 4-5.
    RootedValue method(cx);
    if (!GetInterestingSymbolProperty(cx, obj, cx->wellKnownSymbols().toPrimitive, &method))
        return false;

    // Step 6.
    if (!method.isNullOrUndefined()) {
        // Step 6 of GetMethod. js::Call() below would do this check and throw a
        // TypeError anyway, but this produces a better error message.
        if (!IsCallable(method))
            return ReportCantConvert(cx, JSMSG_TOPRIMITIVE_NOT_CALLABLE, obj, preferredType);

        // Steps 1-3, 6.a-b.
        RootedValue arg0(cx, StringValue(preferredType == JSTYPE_STRING
                                         ? cx->names().string
                                         : preferredType == JSTYPE_NUMBER
                                         ? cx->names().number
                                         : cx->names().default_));

        if (!js::Call(cx, method, vp, arg0, vp))
            return false;

        // Steps 6.c-d.
        if (vp.isObject())
            return ReportCantConvert(cx, JSMSG_TOPRIMITIVE_RETURNED_OBJECT, obj, preferredType);
        return true;
    }

    return OrdinaryToPrimitive(cx, obj, preferredType, vp);
}

/* ES6 draft rev 28 (2014 Oct 14) 7.1.14 */
bool
js::ToPropertyKeySlow(JSContext* cx, HandleValue argument, MutableHandleId result)
{
    MOZ_ASSERT(argument.isObject());

    // Steps 1-2.
    RootedValue key(cx, argument);
    if (!ToPrimitiveSlow(cx, JSTYPE_STRING, &key))
        return false;

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

/* * */

bool
js::IsDelegate(JSContext* cx, HandleObject obj, const js::Value& v, bool* result)
{
    if (v.isPrimitive()) {
        *result = false;
        return true;
    }
    return IsDelegateOfObject(cx, obj, &v.toObject(), result);
}

bool
js::IsDelegateOfObject(JSContext* cx, HandleObject protoObj, JSObject* obj, bool* result)
{
    RootedObject obj2(cx, obj);
    for (;;) {
        if (!GetPrototype(cx, obj2, &obj2))
            return false;
        if (!obj2) {
            *result = false;
            return true;
        }
        if (obj2 == protoObj) {
            *result = true;
            return true;
        }
    }
}

JSObject*
js::PrimitiveToObject(JSContext* cx, const Value& v)
{
    if (v.isString()) {
        Rooted<JSString*> str(cx, v.toString());
        return StringObject::create(cx, str);
    }
    if (v.isNumber())
        return NumberObject::create(cx, v.toNumber());
    if (v.isBoolean())
        return BooleanObject::create(cx, v.toBoolean());
#ifdef ENABLE_BIGINT
    if (v.isSymbol()) {
        RootedSymbol symbol(cx, v.toSymbol());
        return SymbolObject::create(cx, symbol);
    }
    MOZ_ASSERT(v.isBigInt());
    RootedBigInt bigInt(cx, v.toBigInt());
    return BigIntObject::create(cx, bigInt);
#else
    MOZ_ASSERT(v.isSymbol());
    RootedSymbol symbol(cx, v.toSymbol());
    return SymbolObject::create(cx, symbol);
#endif
}

/*
 * Invokes the ES5 ToObject algorithm on vp, returning the result. If vp might
 * already be an object, use ToObject. reportScanStack controls how null and
 * undefined errors are reported.
 *
 * Callers must handle the already-object case.
 */
JSObject*
js::ToObjectSlow(JSContext* cx, JS::HandleValue val, bool reportScanStack)
{
    MOZ_ASSERT(!val.isMagic());
    MOZ_ASSERT(!val.isObject());

    if (val.isNullOrUndefined()) {
        if (reportScanStack) {
            ReportIsNullOrUndefined(cx, JSDVG_SEARCH_STACK, val);
        } else {
            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_CANT_CONVERT_TO,
                                      val.isNull() ? "null" : "undefined", "object");
        }
        return nullptr;
    }

    return PrimitiveToObject(cx, val);
}

Value
js::GetThisValue(JSObject* obj)
{
    // Use the WindowProxy if the global is a Window, as Window must never be
    // exposed to script.
    if (obj->is<GlobalObject>())
        return ObjectValue(*ToWindowProxyIfWindow(obj));

    // We should not expose any environments except NSVOs to script. The NSVO is
    // pretending to be the global object in this case.
    MOZ_ASSERT(obj->is<NonSyntacticVariablesObject>() || !obj->is<EnvironmentObject>());

    return ObjectValue(*obj);
}

Value
js::GetThisValueOfLexical(JSObject* env)
{
    MOZ_ASSERT(IsExtensibleLexicalEnvironment(env));
    return env->as<LexicalEnvironmentObject>().thisValue();
}

Value
js::GetThisValueOfWith(JSObject* env)
{
    MOZ_ASSERT(env->is<WithEnvironmentObject>());
    return GetThisValue(env->as<WithEnvironmentObject>().withThis());
}

class GetObjectSlotNameFunctor : public JS::CallbackTracer::ContextFunctor
{
    JSObject* obj;

  public:
    explicit GetObjectSlotNameFunctor(JSObject* ctx) : obj(ctx) {}
    virtual void operator()(JS::CallbackTracer* trc, char* buf, size_t bufsize) override;
};

void
GetObjectSlotNameFunctor::operator()(JS::CallbackTracer* trc, char* buf, size_t bufsize)
{
    MOZ_ASSERT(trc->contextIndex() != JS::CallbackTracer::InvalidIndex);

    uint32_t slot = uint32_t(trc->contextIndex());

    Shape* shape;
    if (obj->isNative()) {
        shape = obj->as<NativeObject>().lastProperty();
        while (shape && (shape->isEmptyShape() ||
                         !shape->isDataProperty() ||
                         shape->slot() != slot))
        {
            shape = shape->previous();
        }
    } else {
        shape = nullptr;
    }

    if (!shape) {
        do {
            const char* slotname = nullptr;
            const char* pattern = nullptr;
            if (obj->is<GlobalObject>()) {
                pattern = "CLASS_OBJECT(%s)";
                if (false)
                    ;
#define TEST_SLOT_MATCHES_PROTOTYPE(name,init,clasp) \
                else if ((JSProto_##name) == slot) { slotname = js_##name##_str; }
                JS_FOR_EACH_PROTOTYPE(TEST_SLOT_MATCHES_PROTOTYPE)
#undef TEST_SLOT_MATCHES_PROTOTYPE
            } else {
                pattern = "%s";
                if (obj->is<EnvironmentObject>()) {
                    if (slot == EnvironmentObject::enclosingEnvironmentSlot()) {
                        slotname = "enclosing_environment";
                    } else if (obj->is<CallObject>()) {
                        if (slot == CallObject::calleeSlot())
                            slotname = "callee_slot";
                    } else if (obj->is<WithEnvironmentObject>()) {
                        if (slot == WithEnvironmentObject::objectSlot())
                            slotname = "with_object";
                        else if (slot == WithEnvironmentObject::thisSlot())
                            slotname = "with_this";
                    }
                }
            }

            if (slotname)
                snprintf(buf, bufsize, pattern, slotname);
            else
                snprintf(buf, bufsize, "**UNKNOWN SLOT %" PRIu32 "**", slot);
        } while (false);
    } else {
        jsid propid = shape->propid();
        if (JSID_IS_INT(propid)) {
            snprintf(buf, bufsize, "%" PRId32, JSID_TO_INT(propid));
        } else if (JSID_IS_ATOM(propid)) {
            PutEscapedString(buf, bufsize, JSID_TO_ATOM(propid), 0);
        } else if (JSID_IS_SYMBOL(propid)) {
            snprintf(buf, bufsize, "**SYMBOL KEY**");
        } else {
            snprintf(buf, bufsize, "**FINALIZED ATOM KEY**");
        }
    }
}

/*** Debugging routines **************************************************************************/

#ifdef DEBUG

/*
 * Routines to print out values during debugging.  These are FRIEND_API to help
 * the debugger find them and to support temporarily hacking js::Dump* calls
 * into other code.
 */

static void
dumpValue(const Value& v, js::GenericPrinter& out)
{
    if (v.isNull())
        out.put("null");
    else if (v.isUndefined())
        out.put("undefined");
    else if (v.isInt32())
        out.printf("%d", v.toInt32());
    else if (v.isDouble())
        out.printf("%g", v.toDouble());
    else if (v.isString())
        v.toString()->dumpNoNewline(out);
    else if (v.isSymbol())
        v.toSymbol()->dump(out);
    else if (v.isObject() && v.toObject().is<JSFunction>()) {
        JSFunction* fun = &v.toObject().as<JSFunction>();
        if (fun->displayAtom()) {
            out.put("<function ");
            EscapedStringPrinter(out, fun->displayAtom(), 0);
        } else {
            out.put("<unnamed function");
        }
        if (fun->hasScript()) {
            JSScript* script = fun->nonLazyScript();
            out.printf(" (%s:%u)",
                    script->filename() ? script->filename() : "", script->lineno());
        }
        out.printf(" at %p>", (void*) fun);
    } else if (v.isObject()) {
        JSObject* obj = &v.toObject();
        const Class* clasp = obj->getClass();
        out.printf("<%s%s at %p>",
                clasp->name,
                (clasp == &PlainObject::class_) ? "" : " object",
                (void*) obj);
    } else if (v.isBoolean()) {
        if (v.toBoolean())
            out.put("true");
        else
            out.put("false");
    } else if (v.isMagic()) {
        out.put("<invalid");
#ifdef DEBUG
        switch (v.whyMagic()) {
          case JS_ELEMENTS_HOLE:     out.put(" elements hole");      break;
          case JS_NO_ITER_VALUE:     out.put(" no iter value");      break;
          case JS_GENERATOR_CLOSING: out.put(" generator closing");  break;
          case JS_OPTIMIZED_OUT:     out.put(" optimized out");      break;
          default:                   out.put(" ?!");                 break;
        }
#endif
        out.putChar('>');
    } else {
        out.put("unexpected value");
    }
}

namespace js {

// We don't want jsfriendapi.h to depend on GenericPrinter,
// so these functions are declared directly in the cpp.

JS_FRIEND_API(void)
DumpValue(const JS::Value& val, js::GenericPrinter& out);

JS_FRIEND_API(void)
DumpId(jsid id, js::GenericPrinter& out);

JS_FRIEND_API(void)
DumpInterpreterFrame(JSContext* cx, js::GenericPrinter& out, InterpreterFrame* start = nullptr);

} // namespace js

JS_FRIEND_API(void)
js::DumpValue(const Value& val, js::GenericPrinter& out)
{
    dumpValue(val, out);
    out.putChar('\n');
}

JS_FRIEND_API(void)
js::DumpId(jsid id, js::GenericPrinter& out)
{
    out.printf("jsid %p = ", (void*) JSID_BITS(id));
    dumpValue(IdToValue(id), out);
    out.putChar('\n');
}

static void
DumpProperty(const NativeObject* obj, Shape& shape, js::GenericPrinter& out)
{
    jsid id = shape.propid();
    if (JSID_IS_ATOM(id))
        JSID_TO_ATOM(id)->dumpCharsNoNewline(out);
    else if (JSID_IS_INT(id))
       out.printf("%d", JSID_TO_INT(id));
    else if (JSID_IS_SYMBOL(id))
        JSID_TO_SYMBOL(id)->dump(out);
    else
        out.printf("id %p", reinterpret_cast<void*>(JSID_BITS(id)));

    if (shape.isDataProperty()) {
        out.printf(": ");
        dumpValue(obj->getSlot(shape.maybeSlot()), out);
    }

    out.printf(" (shape %p", (void*) &shape);

    uint8_t attrs = shape.attributes();
    if (attrs & JSPROP_ENUMERATE) out.put(" enumerate");
    if (attrs & JSPROP_READONLY) out.put(" readonly");
    if (attrs & JSPROP_PERMANENT) out.put(" permanent");

    if (shape.hasGetterValue())
        out.printf(" getterValue %p", shape.getterObject());
    else if (!shape.hasDefaultGetter())
        out.printf(" getterOp %p", JS_FUNC_TO_DATA_PTR(void*, shape.getterOp()));

    if (shape.hasSetterValue())
        out.printf(" setterValue %p", shape.setterObject());
    else if (!shape.hasDefaultSetter())
        out.printf(" setterOp %p", JS_FUNC_TO_DATA_PTR(void*, shape.setterOp()));

    if (shape.isDataProperty())
        out.printf(" slot %d", shape.maybeSlot());

    out.printf(")\n");
}

bool
JSObject::uninlinedIsProxy() const
{
    return is<ProxyObject>();
}

bool
JSObject::uninlinedNonProxyIsExtensible() const
{
    return nonProxyIsExtensible();
}

void
JSObject::dump(js::GenericPrinter& out) const
{
    const JSObject* obj = this;
    out.printf("object %p\n", obj);

    if (IsCrossCompartmentWrapper(this)) {
        out.printf("  compartment %p\n", compartment());
    } else {
        JSObject* globalObj = &nonCCWGlobal();
        out.printf("  global %p [%s]\n", globalObj, globalObj->getClass()->name);
    }

    const Class* clasp = obj->getClass();
    out.printf("  class %p %s\n", clasp, clasp->name);

    if (obj->hasLazyGroup()) {
        out.put("  lazy group\n");
    } else {
        const ObjectGroup* group = obj->group();
        out.printf("  group %p\n", group);
    }

    out.put("  flags:");
    if (obj->isDelegate()) out.put(" delegate");
    if (!obj->is<ProxyObject>() && !obj->nonProxyIsExtensible()) out.put(" not_extensible");
    if (obj->maybeHasInterestingSymbolProperty()) out.put(" maybe_has_interesting_symbol");
    if (obj->isBoundFunction()) out.put(" bound_function");
    if (obj->isQualifiedVarObj()) out.put(" varobj");
    if (obj->isUnqualifiedVarObj()) out.put(" unqualified_varobj");
    if (obj->isIteratedSingleton()) out.put(" iterated_singleton");
    if (obj->isNewGroupUnknown()) out.put(" new_type_unknown");
    if (obj->hasUncacheableProto()) out.put(" has_uncacheable_proto");
    if (obj->hasStaticPrototype() && obj->staticPrototypeIsImmutable())
        out.put(" immutable_prototype");

    const NativeObject* nobj = obj->isNative() ? &obj->as<NativeObject>() : nullptr;
    if (nobj) {
        if (nobj->inDictionaryMode())
            out.put(" inDictionaryMode");
        if (nobj->hasShapeTable())
            out.put(" hasShapeTable");
        if (nobj->hadElementsAccess())
            out.put(" had_elements_access");
        if (nobj->isIndexed())
            out.put(" indexed");
    } else {
        out.put(" not_native\n");
    }
    out.putChar('\n');

    out.put("  proto ");
    TaggedProto proto = obj->taggedProto();
    if (proto.isDynamic())
        out.put("<dynamic>");
    else
        dumpValue(ObjectOrNullValue(proto.toObjectOrNull()), out);
    out.putChar('\n');

    if (nobj) {
        if (clasp->flags & JSCLASS_HAS_PRIVATE)
            out.printf("  private %p\n", nobj->getPrivate());

        uint32_t reserved = JSCLASS_RESERVED_SLOTS(clasp);
        if (reserved) {
            out.printf("  reserved slots:\n");
            for (uint32_t i = 0; i < reserved; i++) {
                out.printf("    %3d ", i);
                out.put(": ");
                dumpValue(nobj->getSlot(i), out);
                out.putChar('\n');
            }
        }

        out.put("  properties:\n");
        Vector<Shape*, 8, SystemAllocPolicy> props;
        for (Shape::Range<NoGC> r(nobj->lastProperty()); !r.empty(); r.popFront()) {
            if (!props.append(&r.front())) {
                out.printf("(OOM while appending properties)\n");
                break;
            }
        }
        for (size_t i = props.length(); i-- != 0;) {
            out.printf("    ");
            DumpProperty(nobj, *props[i], out);
        }

        uint32_t slots = nobj->getDenseInitializedLength();
        if (slots) {
            out.put("  elements:\n");
            for (uint32_t i = 0; i < slots; i++) {
                out.printf("    %3d: ", i);
                dumpValue(nobj->getDenseElement(i), out);
                out.putChar('\n');
            }
        }
    }
}

// For debuggers.
void
JSObject::dump() const
{
    Fprinter out(stderr);
    dump(out);
}

static void
MaybeDumpScope(Scope* scope, js::GenericPrinter& out)
{
    if (scope) {
        out.printf("  scope: %s\n", ScopeKindString(scope->kind()));
        for (BindingIter bi(scope); bi; bi++) {
            out.put("    ");
            dumpValue(StringValue(bi.name()), out);
            out.putChar('\n');
        }
    }
}

static void
MaybeDumpValue(const char* name, const Value& v, js::GenericPrinter& out)
{
    if (!v.isNull()) {
        out.printf("  %s: ", name);
        dumpValue(v, out);
        out.putChar('\n');
    }
}

JS_FRIEND_API(void)
js::DumpInterpreterFrame(JSContext* cx, js::GenericPrinter& out, InterpreterFrame* start)
{
    /* This should only called during live debugging. */
    ScriptFrameIter i(cx);
    if (!start) {
        if (i.done()) {
            out.printf("no stack for cx = %p\n", (void*) cx);
            return;
        }
    } else {
        while (!i.done() && !i.isJSJit() && i.interpFrame() != start)
            ++i;

        if (i.done()) {
            out.printf("fp = %p not found in cx = %p\n",
                    (void*)start, (void*)cx);
            return;
        }
    }

    for (; !i.done(); ++i) {
        if (i.isJSJit())
            out.put("JIT frame\n");
        else
            out.printf("InterpreterFrame at %p\n", (void*) i.interpFrame());

        if (i.isFunctionFrame()) {
            out.put("callee fun: ");
            RootedValue v(cx);
            JSObject* fun = i.callee(cx);
            v.setObject(*fun);
            dumpValue(v, out);
        } else {
            out.put("global or eval frame, no callee");
        }
        out.putChar('\n');

        out.printf("file %s line %u\n",
                i.script()->filename(), i.script()->lineno());

        if (jsbytecode* pc = i.pc()) {
            out.printf("  pc = %p\n", pc);
            out.printf("  current op: %s\n", CodeName[*pc]);
            MaybeDumpScope(i.script()->lookupScope(pc), out);
        }
        if (i.isFunctionFrame())
            MaybeDumpValue("this", i.thisArgument(cx), out);
        if (!i.isJSJit()) {
            out.put("  rval: ");
            dumpValue(i.interpFrame()->returnValue(), out);
            out.putChar('\n');
        }

        out.put("  flags:");
        if (i.isConstructing())
            out.put(" constructing");
        if (!i.isJSJit() && i.interpFrame()->isDebuggerEvalFrame())
            out.put(" debugger eval");
        if (i.isEvalFrame())
            out.put(" eval");
        out.putChar('\n');

        out.printf("  envChain: (JSObject*) %p\n", (void*) i.environmentChain(cx));

        out.putChar('\n');
    }
}

#endif /* DEBUG */

namespace js {

// We don't want jsfriendapi.h to depend on GenericPrinter,
// so these functions are declared directly in the cpp.

JS_FRIEND_API(void)
DumpBacktrace(JSContext* cx, js::GenericPrinter& out);

}

JS_FRIEND_API(void)
js::DumpBacktrace(JSContext* cx, FILE* fp)
{
    Fprinter out(fp);
    js::DumpBacktrace(cx, out);
}

JS_FRIEND_API(void)
js::DumpBacktrace(JSContext* cx, js::GenericPrinter& out)
{
    size_t depth = 0;
    for (AllFramesIter i(cx); !i.done(); ++i, ++depth) {
        const char* filename;
        unsigned line;
        if (i.hasScript()) {
            filename = JS_GetScriptFilename(i.script());
            line = PCToLineNumber(i.script(), i.pc());
        } else {
            filename = i.filename();
            line = i.computeLine();
        }
        char frameType =
            i.isInterp() ? 'i' :
            i.isBaseline() ? 'b' :
            i.isIon() ? 'I' :
            i.isWasm() ? 'W' :
            '?';

        out.printf("#%zu %14p %c   %s:%d",
                        depth, i.rawFramePtr(), frameType, filename, line);

        if (i.hasScript()) {
            out.printf(" (%p @ %zu)\n",
                            i.script(), i.script()->pcToOffset(i.pc()));
        } else {
            out.printf(" (%p)\n", i.pc());
        }
    }

}

JS_FRIEND_API(void)
js::DumpBacktrace(JSContext* cx)
{
    DumpBacktrace(cx, stdout);
}

/* * */

js::gc::AllocKind
JSObject::allocKindForTenure(const js::Nursery& nursery) const
{
    MOZ_ASSERT(IsInsideNursery(this));

    if (is<ArrayObject>()) {
        const ArrayObject& aobj = as<ArrayObject>();
        MOZ_ASSERT(aobj.numFixedSlots() == 0);

        /* Use minimal size object if we are just going to copy the pointer. */
        if (!nursery.isInside(aobj.getElementsHeader()))
            return AllocKind::OBJECT0_BACKGROUND;

        size_t nelements = aobj.getDenseCapacity();
        return GetBackgroundAllocKind(GetGCArrayKind(nelements));
    }

    // Unboxed plain objects are sized according to the data they store.
    if (is<UnboxedPlainObject>()) {
        size_t nbytes = as<UnboxedPlainObject>().layoutDontCheckGeneration().size();
        return GetGCObjectKindForBytes(UnboxedPlainObject::offsetOfData() + nbytes);
    }

    if (is<JSFunction>())
        return as<JSFunction>().getAllocKind();

    /*
     * Typed arrays in the nursery may have a lazily allocated buffer, make
     * sure there is room for the array's fixed data when moving the array.
     */
    if (is<TypedArrayObject>() && !as<TypedArrayObject>().hasBuffer()) {
        size_t nbytes = as<TypedArrayObject>().byteLength();
        if (as<TypedArrayObject>().hasInlineElements())
            return GetBackgroundAllocKind(TypedArrayObject::AllocKindForLazyBuffer(nbytes));
        return GetGCObjectKind(getClass());
    }

    // Proxies that are CrossCompartmentWrappers may be nursery allocated.
    if (IsProxy(this))
        return as<ProxyObject>().allocKindForTenure();

    // Inlined typed objects are followed by their data, so make sure we copy
    // it all over to the new object.
    if (is<InlineTypedObject>()) {
        // Figure out the size of this object, from the prototype's TypeDescr.
        // The objects we are traversing here are all tenured, so we don't need
        // to check forwarding pointers.
        TypeDescr& descr = as<InlineTypedObject>().typeDescr();
        MOZ_ASSERT(!IsInsideNursery(&descr));
        return InlineTypedObject::allocKindForTypeDescriptor(&descr);
    }

    // Outline typed objects use the minimum allocation kind.
    if (is<OutlineTypedObject>())
        return AllocKind::OBJECT0;

    // All nursery allocatable non-native objects are handled above.
    return as<NativeObject>().allocKindForTenure();
}

void
JSObject::addSizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf, JS::ClassInfo* info)
{
    if (is<NativeObject>() && as<NativeObject>().hasDynamicSlots())
        info->objectsMallocHeapSlots += mallocSizeOf(as<NativeObject>().slots_);

    if (is<NativeObject>() && as<NativeObject>().hasDynamicElements()) {
        js::ObjectElements* elements = as<NativeObject>().getElementsHeader();
        if (!elements->isCopyOnWrite() || elements->ownerObject() == this) {
            void* allocatedElements = as<NativeObject>().getUnshiftedElementsHeader();
            info->objectsMallocHeapElementsNormal += mallocSizeOf(allocatedElements);
        }
    }

    // Other things may be measured in the future if DMD indicates it is worthwhile.
    if (is<JSFunction>() ||
        is<PlainObject>() ||
        is<ArrayObject>() ||
        is<CallObject>() ||
        is<RegExpObject>() ||
        is<ProxyObject>())
    {
        // Do nothing.  But this function is hot, and we win by getting the
        // common cases out of the way early.  Some stats on the most common
        // classes, as measured during a vanilla browser session:
        // - (53.7%, 53.7%): Function
        // - (18.0%, 71.7%): Object
        // - (16.9%, 88.6%): Array
        // - ( 3.9%, 92.5%): Call
        // - ( 2.8%, 95.3%): RegExp
        // - ( 1.0%, 96.4%): Proxy

        // Note that any JSClass that is special cased below likely needs to
        // specify the JSCLASS_DELAY_METADATA_CALLBACK flag, or else we will
        // probably crash if the object metadata callback attempts to get the
        // size of the new object (which Debugger code does) before private
        // slots are initialized.
    } else if (is<ArgumentsObject>()) {
        info->objectsMallocHeapMisc += as<ArgumentsObject>().sizeOfMisc(mallocSizeOf);
    } else if (is<RegExpStaticsObject>()) {
        info->objectsMallocHeapMisc += as<RegExpStaticsObject>().sizeOfData(mallocSizeOf);
    } else if (is<PropertyIteratorObject>()) {
        info->objectsMallocHeapMisc += as<PropertyIteratorObject>().sizeOfMisc(mallocSizeOf);
    } else if (is<ArrayBufferObject>()) {
        ArrayBufferObject::addSizeOfExcludingThis(this, mallocSizeOf, info);
    } else if (is<SharedArrayBufferObject>()) {
        SharedArrayBufferObject::addSizeOfExcludingThis(this, mallocSizeOf, info);
#ifdef JS_HAS_CTYPES
    } else {
        // This must be the last case.
        info->objectsMallocHeapMisc +=
            js::SizeOfDataIfCDataObject(mallocSizeOf, const_cast<JSObject*>(this));
#endif
    }
}

size_t
JSObject::sizeOfIncludingThisInNursery() const
{
    // This function doesn't concern itself yet with typed objects (bug 1133593)
    // nor unboxed objects (bug 1133592).

    MOZ_ASSERT(!isTenured());

    const Nursery& nursery = runtimeFromMainThread()->gc.nursery();
    size_t size = Arena::thingSize(allocKindForTenure(nursery));

    if (is<NativeObject>()) {
        const NativeObject& native = as<NativeObject>();

        size += native.numFixedSlots() * sizeof(Value);
        size += native.numDynamicSlots() * sizeof(Value);

        if (native.hasDynamicElements()) {
            js::ObjectElements& elements = *native.getElementsHeader();
            if (!elements.isCopyOnWrite() || elements.ownerObject() == this)
                size += (elements.capacity + elements.numShiftedElements()) * sizeof(HeapSlot);
        }

        if (is<ArgumentsObject>())
            size += as<ArgumentsObject>().sizeOfData();
    }

    return size;
}

JS::ubi::Node::Size
JS::ubi::Concrete<JSObject>::size(mozilla::MallocSizeOf mallocSizeOf) const
{
    JSObject& obj = get();

    if (!obj.isTenured())
        return obj.sizeOfIncludingThisInNursery();

    JS::ClassInfo info;
    obj.addSizeOfExcludingThis(mallocSizeOf, &info);
    return obj.tenuredSizeOfThis() + info.sizeOfAllThings();
}

const char16_t JS::ubi::Concrete<JSObject>::concreteTypeName[] = u"JSObject";

void
JSObject::traceChildren(JSTracer* trc)
{
    TraceEdge(trc, &group_, "group");

    if (is<ShapedObject>())
        as<ShapedObject>().traceShape(trc);

    const Class* clasp = group_->clasp();
    if (clasp->isNative()) {
        NativeObject* nobj = &as<NativeObject>();

        {
            GetObjectSlotNameFunctor func(nobj);
            JS::AutoTracingDetails ctx(trc, func);
            JS::AutoTracingIndex index(trc);
            // Tracing can mutate the target but cannot change the slot count,
            // but the compiler has no way of knowing this.
            const uint32_t nslots = nobj->slotSpan();
            for (uint32_t i = 0; i < nslots; ++i) {
                TraceManuallyBarrieredEdge(trc, nobj->getSlotRef(i).unsafeUnbarrieredForTracing(),
                                           "object slot");
                ++index;
            }
            MOZ_ASSERT(nslots == nobj->slotSpan());
        }

        do {
            if (nobj->denseElementsAreCopyOnWrite()) {
                GCPtrNativeObject& owner = nobj->getElementsHeader()->ownerObject();
                if (owner != nobj) {
                    TraceEdge(trc, &owner, "objectElementsOwner");
                    break;
                }
            }

            TraceRange(trc,
                       nobj->getDenseInitializedLength(),
                       static_cast<HeapSlot*>(nobj->getDenseElementsAllowCopyOnWrite()),
                       "objectElements");
        } while (false);
    }

    // Call the trace hook at the end so that during a moving GC the trace hook
    // will see updated fields and slots.
    if (clasp->hasTrace())
        clasp->doTrace(trc, this);
}

static JSAtom*
displayAtomFromObjectGroup(ObjectGroup& group)
{
    AutoSweepObjectGroup sweep(&group);
    TypeNewScript* script = group.newScript(sweep);
    if (!script)
        return nullptr;

    return script->function()->displayAtom();
}

/* static */ bool
JSObject::constructorDisplayAtom(JSContext* cx, js::HandleObject obj, js::MutableHandleAtom name)
{
    ObjectGroup *g = JSObject::getGroup(cx, obj);
    if (!g)
        return false;

    name.set(displayAtomFromObjectGroup(*g));
    return true;
}

JSAtom*
JSObject::maybeConstructorDisplayAtom() const
{
    if (hasLazyGroup())
        return nullptr;
    return displayAtomFromObjectGroup(*group());
}

// ES 2016 7.3.20.
MOZ_MUST_USE JSObject*
js::SpeciesConstructor(JSContext* cx, HandleObject obj, HandleObject defaultCtor,
                       bool (*isDefaultSpecies)(JSContext*, JSFunction*))
{
    // Step 1 (implicit).

    // Fast-path for steps 2 - 8. Applies if all of the following conditions
    // are met:
    // - obj.constructor can be retrieved without side-effects.
    // - obj.constructor[[@@species]] can be retrieved without side-effects.
    // - obj.constructor[[@@species]] is the builtin's original @@species
    //   getter.
    RootedValue ctor(cx);
    bool ctorGetSucceeded = GetPropertyPure(cx, obj, NameToId(cx->names().constructor),
                                            ctor.address());
    if (ctorGetSucceeded && ctor.isObject() && &ctor.toObject() == defaultCtor) {
        jsid speciesId = SYMBOL_TO_JSID(cx->wellKnownSymbols().species);
        JSFunction* getter;
        if (GetGetterPure(cx, defaultCtor, speciesId, &getter) && getter &&
            isDefaultSpecies(cx, getter))
        {
            return defaultCtor;
        }
    }

    // Step 2.
    if (!ctorGetSucceeded && !GetProperty(cx, obj, obj, cx->names().constructor, &ctor))
        return nullptr;

    // Step 3.
    if (ctor.isUndefined())
        return defaultCtor;

    // Step 4.
    if (!ctor.isObject()) {
        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NOT_NONNULL_OBJECT,
                                  "object's 'constructor' property");
        return nullptr;
    }

    // Step 5.
    RootedObject ctorObj(cx, &ctor.toObject());
    RootedValue s(cx);
    RootedId speciesId(cx, SYMBOL_TO_JSID(cx->wellKnownSymbols().species));
    if (!GetProperty(cx, ctorObj, ctor, speciesId, &s))
        return nullptr;

    // Step 6.
    if (s.isNullOrUndefined())
        return defaultCtor;

    // Step 7.
    if (IsConstructor(s))
        return &s.toObject();

    // Step 8.
    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NOT_CONSTRUCTOR,
                              "[Symbol.species] property of object's constructor");
    return nullptr;
}

MOZ_MUST_USE JSObject*
js::SpeciesConstructor(JSContext* cx, HandleObject obj, JSProtoKey ctorKey,
                       bool (*isDefaultSpecies)(JSContext*, JSFunction*))
{
    RootedObject defaultCtor(cx, GlobalObject::getOrCreateConstructor(cx, ctorKey));
    if (!defaultCtor)
        return nullptr;
    return SpeciesConstructor(cx, obj, defaultCtor, isDefaultSpecies);
}

bool
js::Unbox(JSContext* cx, HandleObject obj, MutableHandleValue vp)
{
    if (MOZ_UNLIKELY(obj->is<ProxyObject>()))
        return Proxy::boxedValue_unbox(cx, obj, vp);

    if (obj->is<BooleanObject>())
        vp.setBoolean(obj->as<BooleanObject>().unbox());
    else if (obj->is<NumberObject>())
        vp.setNumber(obj->as<NumberObject>().unbox());
    else if (obj->is<StringObject>())
        vp.setString(obj->as<StringObject>().unbox());
    else if (obj->is<DateObject>())
        vp.set(obj->as<DateObject>().UTCTime());
    else if (obj->is<SymbolObject>())
        vp.setSymbol(obj->as<SymbolObject>().unbox());
#ifdef ENABLE_BIGINT
    else if (obj->is<BigIntObject>())
        vp.setBigInt(obj->as<BigIntObject>().unbox());
#endif
    else
        vp.setUndefined();

    return true;
}

#ifdef DEBUG
/* static */ void
JSObject::debugCheckNewObject(ObjectGroup* group, Shape* shape, js::gc::AllocKind allocKind,
                              js::gc::InitialHeap heap)
{
    const js::Class* clasp = group->clasp();
    MOZ_ASSERT(clasp != &ArrayObject::class_);

    if (shape)
        MOZ_ASSERT(clasp == shape->getObjectClass());
    else
        MOZ_ASSERT(clasp == &UnboxedPlainObject::class_);

    if (!ClassCanHaveFixedData(clasp)) {
        MOZ_ASSERT(shape);
        MOZ_ASSERT(gc::GetGCKindSlots(allocKind, clasp) == shape->numFixedSlots());
    }

    // Classes with a finalizer must specify whether instances will be finalized
    // on the main thread or in the background, except proxies whose behaviour
    // depends on the target object.
    static const uint32_t FinalizeMask = JSCLASS_FOREGROUND_FINALIZE | JSCLASS_BACKGROUND_FINALIZE;
    uint32_t flags = clasp->flags;
    uint32_t finalizeFlags = flags & FinalizeMask;
    if (clasp->hasFinalize() && !clasp->isProxy()) {
        MOZ_ASSERT(finalizeFlags == JSCLASS_FOREGROUND_FINALIZE ||
                   finalizeFlags == JSCLASS_BACKGROUND_FINALIZE);
        MOZ_ASSERT((finalizeFlags == JSCLASS_BACKGROUND_FINALIZE) == IsBackgroundFinalized(allocKind));
    } else {
        MOZ_ASSERT(finalizeFlags == 0);
    }

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

    MOZ_ASSERT(!group->realm()->hasObjectPendingMetadata());

    // Non-native classes manage their own data and slots, so numFixedSlots and
    // slotSpan are always 0. Note that proxy classes can have reserved slots
    // but they're also not included in numFixedSlots/slotSpan.
    if (!clasp->isNative()) {
        MOZ_ASSERT_IF(!clasp->isProxy(), JSCLASS_RESERVED_SLOTS(clasp) == 0);
        MOZ_ASSERT(!clasp->hasPrivate());
        MOZ_ASSERT_IF(shape, shape->numFixedSlots() == 0);
        MOZ_ASSERT_IF(shape, shape->slotSpan() == 0);
    }
}
#endif