C++ PropertyDescriptor::value方法代码示例

static JSValue defineProperties(ExecState* exec, JSObject* object, JSObject* properties)
{
    PropertyNameArray propertyNames(exec);
    asObject(properties)->methodTable()->getOwnPropertyNames(asObject(properties), exec, propertyNames, ExcludeDontEnumProperties);
    size_t numProperties = propertyNames.size();
    Vector<PropertyDescriptor> descriptors;
    MarkedArgumentBuffer markBuffer;
    for (size_t i = 0; i < numProperties; i++) {
        PropertySlot slot;
        JSValue prop = properties->get(exec, propertyNames[i]);
        if (exec->hadException())
            return jsNull();
        PropertyDescriptor descriptor;
        if (!toPropertyDescriptor(exec, prop, descriptor))
            return jsNull();
        descriptors.append(descriptor);
        // Ensure we mark all the values that we're accumulating
        if (descriptor.isDataDescriptor() && descriptor.value())
            markBuffer.append(descriptor.value());
        if (descriptor.isAccessorDescriptor()) {
            if (descriptor.getter())
                markBuffer.append(descriptor.getter());
            if (descriptor.setter())
                markBuffer.append(descriptor.setter());
        }
    }
    for (size_t i = 0; i < numProperties; i++) {
        object->methodTable()->defineOwnProperty(object, exec, propertyNames[i], descriptors[i], true);
        if (exec->hadException())
            return jsNull();
    }
    return object;
}

JSValue JSC_HOST_CALL objectConstructorGetOwnPropertyDescriptor(ExecState* exec, JSObject*, JSValue, const ArgList& args)
{
    if (!args.at(0).isObject())
        return throwError(exec, TypeError, "Requested property descriptor of a value that is not an object.");
    UString propertyName = args.at(1).toString(exec);
    if (exec->hadException())
        return jsNull();
    JSObject* object = asObject(args.at(0));
    PropertyDescriptor descriptor;
    if (!object->getOwnPropertyDescriptor(exec, Identifier(exec, propertyName), descriptor))
        return jsUndefined();
    if (exec->hadException())
        return jsUndefined();

    JSObject* description = constructEmptyObject(exec);
    if (!descriptor.isAccessorDescriptor()) {
        description->putDirect(exec->propertyNames().value, descriptor.value() ? descriptor.value() : jsUndefined(), 0);
        description->putDirect(exec->propertyNames().writable, jsBoolean(descriptor.writable()), 0);
    } else {
        description->putDirect(exec->propertyNames().get, descriptor.getter() ? descriptor.getter() : jsUndefined(), 0);
        description->putDirect(exec->propertyNames().set, descriptor.setter() ? descriptor.setter() : jsUndefined(), 0);
    }
    
    description->putDirect(exec->propertyNames().enumerable, jsBoolean(descriptor.enumerable()), 0);
    description->putDirect(exec->propertyNames().configurable, jsBoolean(descriptor.configurable()), 0);

    return description;
}

bool RegExpObject::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, const PropertyDescriptor& descriptor, bool shouldThrow)
{
    VM& vm = exec->vm();
    auto scope = DECLARE_THROW_SCOPE(vm);

    if (propertyName == vm.propertyNames->lastIndex) {
        RegExpObject* regExp = asRegExpObject(object);
        if (descriptor.configurablePresent() && descriptor.configurable())
            return typeError(exec, scope, shouldThrow, ASCIILiteral(UnconfigurablePropertyChangeConfigurabilityError));
        if (descriptor.enumerablePresent() && descriptor.enumerable())
            return typeError(exec, scope, shouldThrow, ASCIILiteral(UnconfigurablePropertyChangeEnumerabilityError));
        if (descriptor.isAccessorDescriptor())
            return typeError(exec, scope, shouldThrow, ASCIILiteral(UnconfigurablePropertyChangeAccessMechanismError));
        if (!regExp->m_lastIndexIsWritable) {
            if (descriptor.writablePresent() && descriptor.writable())
                return typeError(exec, scope, shouldThrow, ASCIILiteral(UnconfigurablePropertyChangeWritabilityError));
            if (!sameValue(exec, regExp->getLastIndex(), descriptor.value()))
                return typeError(exec, scope, shouldThrow, ASCIILiteral(ReadonlyPropertyChangeError));
            return true;
        }
        if (descriptor.value()) {
            regExp->setLastIndex(exec, descriptor.value(), false);
            RETURN_IF_EXCEPTION(scope, false);
        }
        if (descriptor.writablePresent() && !descriptor.writable())
            regExp->m_lastIndexIsWritable = false;
        return true;
    }

    scope.release();
    return Base::defineOwnProperty(object, exec, propertyName, descriptor, shouldThrow);
}

bool Arguments::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor, bool shouldThrow)
{
    Arguments* thisObject = jsCast<Arguments*>(object);
    unsigned i = propertyName.asIndex();
    if (i < thisObject->d->numArguments) {
        ASSERT(i < PropertyName::NotAnIndex);
        // If the property is not yet present on the object, and is not yet marked as deleted, then add it now.
        PropertySlot slot;
        if ((!thisObject->d->deletedArguments || !thisObject->d->deletedArguments[i]) && !JSObject::getOwnPropertySlot(thisObject, exec, propertyName, slot))
            object->putDirect(exec->globalData(), propertyName, thisObject->argument(i).get(), 0);
        if (!Base::defineOwnProperty(object, exec, propertyName, descriptor, shouldThrow))
            return false;

        if (!thisObject->d->deletedArguments) {
            thisObject->d->deletedArguments = adoptArrayPtr(new bool[thisObject->d->numArguments]);
            memset(thisObject->d->deletedArguments.get(), 0, sizeof(bool) * thisObject->d->numArguments);
        }
        // From ES 5.1, 10.6 Arguments Object
        // 5. If the value of isMapped is not undefined, then
        if (!thisObject->d->deletedArguments[i]) {
            // a. If IsAccessorDescriptor(Desc) is true, then
            if (descriptor.isAccessorDescriptor()) {
                // i. Call the [[Delete]] internal method of map passing P, and false as the arguments.
                thisObject->d->deletedArguments[i] = true;
            } else { // b. Else
                // i. If Desc.[[Value]] is present, then
                // 1. Call the [[Put]] internal method of map passing P, Desc.[[Value]], and Throw as the arguments.
                if (descriptor.value())
                    thisObject->argument(i).set(exec->globalData(), thisObject, descriptor.value());
                // ii. If Desc.[[Writable]] is present and its value is false, then
                // 1. Call the [[Delete]] internal method of map passing P and false as arguments.
                if (descriptor.writablePresent() && !descriptor.writable())
                    thisObject->d->deletedArguments[i] = true;
            }
        }
        return true;
    }

    if (propertyName == exec->propertyNames().length && !thisObject->d->overrodeLength) {
        thisObject->putDirect(exec->globalData(), propertyName, jsNumber(thisObject->d->numArguments), DontEnum);
        thisObject->d->overrodeLength = true;
    } else if (propertyName == exec->propertyNames().callee && !thisObject->d->overrodeCallee) {
        thisObject->putDirect(exec->globalData(), propertyName, thisObject->d->callee.get(), DontEnum);
        thisObject->d->overrodeCallee = true;
    } else if (propertyName == exec->propertyNames().caller && thisObject->d->isStrictMode)
        thisObject->createStrictModeCallerIfNecessary(exec);

    return Base::defineOwnProperty(object, exec, propertyName, descriptor, shouldThrow);
}

static bool putDescriptor(ExecState* exec, JSObject* target, const Identifier& propertyName, PropertyDescriptor& descriptor, unsigned attributes, JSValue oldValue)
{
    if (descriptor.isGenericDescriptor() || descriptor.isDataDescriptor()) {
        target->putWithAttributes(exec, propertyName, descriptor.value() ? descriptor.value() : oldValue, attributes & ~(Getter | Setter));
        return true;
    }
    attributes &= ~ReadOnly;
    if (descriptor.getter() && descriptor.getter().isObject())
        target->defineGetter(exec, propertyName, asObject(descriptor.getter()), attributes);
    if (exec->hadException())
        return false;
    if (descriptor.setter() && descriptor.setter().isObject())
        target->defineSetter(exec, propertyName, asObject(descriptor.setter()), attributes);
    return !exec->hadException();
}

bool Arguments::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, const PropertyDescriptor& descriptor, bool shouldThrow)
{
    Arguments* thisObject = jsCast<Arguments*>(object);
    unsigned i = propertyName.asIndex();
    if (i < thisObject->m_numArguments) {
        RELEASE_ASSERT(i < PropertyName::NotAnIndex);
        // If the property is not yet present on the object, and is not yet marked as deleted, then add it now.
        PropertySlot slot(thisObject);
        if (!thisObject->isDeletedArgument(i) && !JSObject::getOwnPropertySlot(thisObject, exec, propertyName, slot)) {
            JSValue value = thisObject->tryGetArgument(i);
            ASSERT(value);
            object->putDirectMayBeIndex(exec, propertyName, value);
        }
        if (!Base::defineOwnProperty(object, exec, propertyName, descriptor, shouldThrow))
            return false;

        // From ES 5.1, 10.6 Arguments Object
        // 5. If the value of isMapped is not undefined, then
        if (thisObject->isArgument(i)) {
            // a. If IsAccessorDescriptor(Desc) is true, then
            if (descriptor.isAccessorDescriptor()) {
                // i. Call the [[Delete]] internal method of map passing P, and false as the arguments.
                thisObject->tryDeleteArgument(exec->vm(), i);
            } else { // b. Else
                // i. If Desc.[[Value]] is present, then
                // 1. Call the [[Put]] internal method of map passing P, Desc.[[Value]], and Throw as the arguments.
                if (descriptor.value())
                    thisObject->trySetArgument(exec->vm(), i, descriptor.value());
                // ii. If Desc.[[Writable]] is present and its value is false, then
                // 1. Call the [[Delete]] internal method of map passing P and false as arguments.
                if (descriptor.writablePresent() && !descriptor.writable())
                    thisObject->tryDeleteArgument(exec->vm(), i);
            }
        }
        return true;
    }

    if (propertyName == exec->propertyNames().length && !thisObject->m_overrodeLength) {
        thisObject->putDirect(exec->vm(), propertyName, jsNumber(thisObject->m_numArguments), DontEnum);
        thisObject->m_overrodeLength = true;
    } else if (propertyName == exec->propertyNames().callee && !thisObject->m_overrodeCallee) {
        thisObject->putDirect(exec->vm(), propertyName, thisObject->m_callee.get(), DontEnum);
        thisObject->m_overrodeCallee = true;
    } else if (propertyName == exec->propertyNames().caller && thisObject->m_isStrictMode)
        thisObject->createStrictModeCallerIfNecessary(exec);

    return Base::defineOwnProperty(object, exec, propertyName, descriptor, shouldThrow);
}

EncodedJSValue JSC_HOST_CALL objectConstructorGetOwnPropertyDescriptor(ExecState* exec)
{
    if (!exec->argument(0).isObject())
        return throwVMError(exec, createTypeError(exec, ASCIILiteral("Requested property descriptor of a value that is not an object.")));
    String propertyName = exec->argument(1).toString(exec)->value(exec);
    if (exec->hadException())
        return JSValue::encode(jsNull());
    JSObject* object = asObject(exec->argument(0));
    PropertyDescriptor descriptor;
    if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, Identifier(exec, propertyName), descriptor))
        return JSValue::encode(jsUndefined());
    if (exec->hadException())
        return JSValue::encode(jsUndefined());

    JSObject* description = constructEmptyObject(exec);
    if (!descriptor.isAccessorDescriptor()) {
        description->putDirect(exec->vm(), exec->propertyNames().value, descriptor.value() ? descriptor.value() : jsUndefined(), 0);
        description->putDirect(exec->vm(), exec->propertyNames().writable, jsBoolean(descriptor.writable()), 0);
    } else {
        ASSERT(descriptor.getter());
        ASSERT(descriptor.setter());
        description->putDirect(exec->vm(), exec->propertyNames().get, descriptor.getter(), 0);
        description->putDirect(exec->vm(), exec->propertyNames().set, descriptor.setter(), 0);
    }

    description->putDirect(exec->vm(), exec->propertyNames().enumerable, jsBoolean(descriptor.enumerable()), 0);
    description->putDirect(exec->vm(), exec->propertyNames().configurable, jsBoolean(descriptor.configurable()), 0);

    return JSValue::encode(description);
}

bool StringObject::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor, bool throwException)
{
    StringObject* thisObject = jsCast<StringObject*>(object);

    if (propertyName == exec->propertyNames().length) {
        if (!object->isExtensible()) {
            if (throwException)
                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to define property on object that is not extensible.")));
            return false;
        }
        if (descriptor.configurablePresent() && descriptor.configurable()) {
            if (throwException)
                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to configurable attribute of unconfigurable property.")));
            return false;
        }
        if (descriptor.enumerablePresent() && descriptor.enumerable()) {
            if (throwException)
                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change enumerable attribute of unconfigurable property.")));
            return false;
        }
        if (descriptor.isAccessorDescriptor()) {
            if (throwException)
                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change access mechanism for an unconfigurable property.")));
            return false;
        }
        if (descriptor.writablePresent() && descriptor.writable()) {
            if (throwException)
                throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change writable attribute of unconfigurable property.")));
            return false;
        }
        if (!descriptor.value())
            return true;
        if (propertyName == exec->propertyNames().length && sameValue(exec, descriptor.value(), jsNumber(thisObject->internalValue()->length())))
            return true;
        if (throwException)
            throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change value of a readonly property.")));
        return false;
    }

    return Base::defineOwnProperty(object, exec, propertyName, descriptor, throwException);
}

// Defined in ES5.1 15.4.5.1
bool JSArray::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, const PropertyDescriptor& descriptor, bool throwException)
{
    JSArray* array = jsCast<JSArray*>(object);

    // 3. If P is "length", then
    if (propertyName == exec->propertyNames().length) {
        // All paths through length definition call the default [[DefineOwnProperty]], hence:
        // from ES5.1 8.12.9 7.a.
        if (descriptor.configurablePresent() && descriptor.configurable())
            return reject(exec, throwException, "Attempting to change configurable attribute of unconfigurable property.");
        // from ES5.1 8.12.9 7.b.
        if (descriptor.enumerablePresent() && descriptor.enumerable())
            return reject(exec, throwException, "Attempting to change enumerable attribute of unconfigurable property.");

        // a. If the [[Value]] field of Desc is absent, then
        // a.i. Return the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", Desc, and Throw as arguments.
        if (descriptor.isAccessorDescriptor())
            return reject(exec, throwException, "Attempting to change access mechanism for an unconfigurable property.");
        // from ES5.1 8.12.9 10.a.
        if (!array->isLengthWritable() && descriptor.writablePresent() && descriptor.writable())
            return reject(exec, throwException, "Attempting to change writable attribute of unconfigurable property.");
        // This descriptor is either just making length read-only, or changing nothing!
        if (!descriptor.value()) {
            if (descriptor.writablePresent())
                array->setLengthWritable(exec, descriptor.writable());
            return true;
        }
        
        // b. Let newLenDesc be a copy of Desc.
        // c. Let newLen be ToUint32(Desc.[[Value]]).
        unsigned newLen = descriptor.value().toUInt32(exec);
        // d. If newLen is not equal to ToNumber( Desc.[[Value]]), throw a RangeError exception.
        if (newLen != descriptor.value().toNumber(exec)) {
            exec->vm().throwException(exec, createRangeError(exec, ASCIILiteral("Invalid array length")));
            return false;
        }

        // Based on SameValue check in 8.12.9, this is always okay.
        // FIXME: Nothing prevents this from being called on a RuntimeArray, and the length function will always return 0 in that case.
        if (newLen == array->length()) {
            if (descriptor.writablePresent())
                array->setLengthWritable(exec, descriptor.writable());
            return true;
        }

        // e. Set newLenDesc.[[Value] to newLen.
        // f. If newLen >= oldLen, then
        // f.i. Return the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and Throw as arguments.
        // g. Reject if oldLenDesc.[[Writable]] is false.
        if (!array->isLengthWritable())
            return reject(exec, throwException, "Attempting to change value of a readonly property.");
        
        // h. If newLenDesc.[[Writable]] is absent or has the value true, let newWritable be true.
        // i. Else,
        // i.i. Need to defer setting the [[Writable]] attribute to false in case any elements cannot be deleted.
        // i.ii. Let newWritable be false.
        // i.iii. Set newLenDesc.[[Writable] to true.
        // j. Let succeeded be the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and Throw as arguments.
        // k. If succeeded is false, return false.
        // l. While newLen < oldLen repeat,
        // l.i. Set oldLen to oldLen – 1.
        // l.ii. Let deleteSucceeded be the result of calling the [[Delete]] internal method of A passing ToString(oldLen) and false as arguments.
        // l.iii. If deleteSucceeded is false, then
        if (!array->setLength(exec, newLen, throwException)) {
            // 1. Set newLenDesc.[[Value] to oldLen+1.
            // 2. If newWritable is false, set newLenDesc.[[Writable] to false.
            // 3. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and false as arguments.
            // 4. Reject.
            if (descriptor.writablePresent())
                array->setLengthWritable(exec, descriptor.writable());
            return false;
        }

        // m. If newWritable is false, then
        // i. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length",
        //    Property Descriptor{[[Writable]]: false}, and false as arguments. This call will always
        //    return true.
        if (descriptor.writablePresent())
            array->setLengthWritable(exec, descriptor.writable());
        // n. Return true.
        return true;
    }

    // 4. Else if P is an array index (15.4), then
    // a. Let index be ToUint32(P).
    if (Optional<uint32_t> optionalIndex = parseIndex(propertyName)) {
        // b. Reject if index >= oldLen and oldLenDesc.[[Writable]] is false.
        uint32_t index = optionalIndex.value();
        // FIXME: Nothing prevents this from being called on a RuntimeArray, and the length function will always return 0 in that case.
        if (index >= array->length() && !array->isLengthWritable())
            return reject(exec, throwException, "Attempting to define numeric property on array with non-writable length property.");
        // c. Let succeeded be the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing P, Desc, and false as arguments.
        // d. Reject if succeeded is false.
        // e. If index >= oldLen
        // e.i. Set oldLenDesc.[[Value]] to index + 1.
        // e.ii. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", oldLenDesc, and false as arguments. This call will always return true.
        // f. Return true.
        return array->defineOwnIndexedProperty(exec, index, descriptor, throwException);
    }
//.........这里部分代码省略.........

bool JSFunction::defineOwnProperty(JSObject* object, ExecState* exec, PropertyName propertyName, PropertyDescriptor& descriptor, bool throwException)
{
    JSFunction* thisObject = jsCast<JSFunction*>(object);
    if (thisObject->isHostFunction())
        return Base::defineOwnProperty(object, exec, propertyName, descriptor, throwException);

    if (propertyName == exec->propertyNames().prototype) {
        // Make sure prototype has been reified, such that it can only be overwritten
        // following the rules set out in ECMA-262 8.12.9.
        PropertySlot slot;
        thisObject->methodTable()->getOwnPropertySlot(thisObject, exec, propertyName, slot);
        thisObject->m_allocationProfile.clear();
        thisObject->m_allocationProfileWatchpoint.notifyWrite();
        return Base::defineOwnProperty(object, exec, propertyName, descriptor, throwException);
    }

    bool valueCheck;
    if (propertyName == exec->propertyNames().arguments) {
        if (thisObject->jsExecutable()->isStrictMode()) {
            if (!Base::getOwnPropertyDescriptor(thisObject, exec, propertyName, descriptor))
                thisObject->putDirectAccessor(exec, propertyName, thisObject->globalObject()->throwTypeErrorGetterSetter(exec), DontDelete | DontEnum | Accessor);
            return Base::defineOwnProperty(object, exec, propertyName, descriptor, throwException);
        }
        valueCheck = !descriptor.value() || sameValue(exec, descriptor.value(), exec->interpreter()->retrieveArgumentsFromVMCode(exec, thisObject));
    } else if (propertyName == exec->propertyNames().caller) {
        if (thisObject->jsExecutable()->isStrictMode()) {
            if (!Base::getOwnPropertyDescriptor(thisObject, exec, propertyName, descriptor))
                thisObject->putDirectAccessor(exec, propertyName, thisObject->globalObject()->throwTypeErrorGetterSetter(exec), DontDelete | DontEnum | Accessor);
            return Base::defineOwnProperty(object, exec, propertyName, descriptor, throwException);
        }
        valueCheck = !descriptor.value() || sameValue(exec, descriptor.value(), exec->interpreter()->retrieveCallerFromVMCode(exec, thisObject));
    } else if (propertyName == exec->propertyNames().length)
        valueCheck = !descriptor.value() || sameValue(exec, descriptor.value(), jsNumber(thisObject->jsExecutable()->parameterCount()));
    else if (propertyName == exec->propertyNames().name)
        valueCheck = !descriptor.value() || sameValue(exec, descriptor.value(), thisObject->jsExecutable()->nameValue());
    else
        return Base::defineOwnProperty(object, exec, propertyName, descriptor, throwException);
     
    if (descriptor.configurablePresent() && descriptor.configurable()) {
        if (throwException)
            throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to configurable attribute of unconfigurable property.")));
        return false;
    }
    if (descriptor.enumerablePresent() && descriptor.enumerable()) {
        if (throwException)
            throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change enumerable attribute of unconfigurable property.")));
        return false;
    }
    if (descriptor.isAccessorDescriptor()) {
        if (throwException)
            throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change access mechanism for an unconfigurable property.")));
        return false;
    }
    if (descriptor.writablePresent() && descriptor.writable()) {
        if (throwException)
            throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change writable attribute of unconfigurable property.")));
        return false;
    }
    if (!valueCheck) {
        if (throwException)
            throwError(exec, createTypeError(exec, ASCIILiteral("Attempting to change value of a readonly property.")));
        return false;
    }
    return true;
}

bool JSObject::defineOwnProperty(ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor, bool throwException)
{
    // If we have a new property we can just put it on normally
    PropertyDescriptor current;
    if (!getOwnPropertyDescriptor(exec, propertyName, current))
        return putDescriptor(exec, this, propertyName, descriptor, descriptor.attributes(), jsUndefined());

    if (descriptor.isEmpty())
        return true;

    if (current.equalTo(descriptor))
        return true;

    // Filter out invalid changes
    if (!current.configurable()) {
        if (descriptor.configurable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to configurable attribute of unconfigurable property.");
            return false;
        }
        if (descriptor.enumerablePresent() && descriptor.enumerable() != current.enumerable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change enumerable attribute of unconfigurable property.");
            return false;
        }
    }

    // A generic descriptor is simply changing the attributes of an existing property
    if (descriptor.isGenericDescriptor()) {
        if (!current.attributesEqual(descriptor)) {
            deleteProperty(exec, propertyName);
            putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value());
        }
        return true;
    }

    // Changing between a normal property or an accessor property
    if (descriptor.isDataDescriptor() != current.isDataDescriptor()) {
        if (!current.configurable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change access mechanism for an unconfigurable property.");
            return false;
        }
        deleteProperty(exec, propertyName);
        return putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value() ? current.value() : jsUndefined());
    }

    // Changing the value and attributes of an existing property
    if (descriptor.isDataDescriptor()) {
        if (!current.configurable()) {
            if (!current.writable() && descriptor.writable()) {
                if (throwException)
                    throwError(exec, TypeError, "Attempting to change writable attribute of unconfigurable property.");
                return false;
            }
            if (!current.writable()) {
                if (descriptor.value() || !JSValue::strictEqual(current.value(), descriptor.value())) {
                    if (throwException)
                        throwError(exec, TypeError, "Attempting to change value of a readonly property.");
                    return false;
                }
            }
        } else if (current.attributesEqual(descriptor)) {
            if (!descriptor.value())
                return true;
            PutPropertySlot slot;
            put(exec, propertyName, descriptor.value(), slot);
            if (exec->hadException())
                return false;
            return true;
        }
        deleteProperty(exec, propertyName);
        return putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value());
    }

    // Changing the accessor functions of an existing accessor property
    ASSERT(descriptor.isAccessorDescriptor());
    if (!current.configurable()) {
        if (descriptor.setterPresent() && !(current.setter() && JSValue::strictEqual(current.setter(), descriptor.setter()))) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change the setter of an unconfigurable property.");
            return false;
        }
        if (descriptor.getterPresent() && !(current.getter() && JSValue::strictEqual(current.getter(), descriptor.getter()))) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change the getter of an unconfigurable property.");
            return false;
        }
    }
    JSValue accessor = getDirect(propertyName);
    if (!accessor)
        return false;
    GetterSetter* getterSetter = asGetterSetter(accessor);
    if (current.attributesEqual(descriptor)) {
        if (descriptor.setter())
            getterSetter->setSetter(asObject(descriptor.setter()));
        if (descriptor.getter())
            getterSetter->setGetter(asObject(descriptor.getter()));
        return true;
    }
//.........这里部分代码省略.........

JSObject* ProgramExecutable::initializeGlobalProperties(VM& vm, CallFrame* callFrame, JSScope* scope)
{
    auto throwScope = DECLARE_THROW_SCOPE(vm);
    RELEASE_ASSERT(scope);
    JSGlobalObject* globalObject = scope->globalObject();
    RELEASE_ASSERT(globalObject);
    ASSERT(&globalObject->vm() == &vm);

    ParserError error;
    JSParserStrictMode strictMode = isStrictMode() ? JSParserStrictMode::Strict : JSParserStrictMode::NotStrict;
    DebuggerMode debuggerMode = globalObject->hasInteractiveDebugger() ? DebuggerOn : DebuggerOff;

    UnlinkedProgramCodeBlock* unlinkedCodeBlock = vm.codeCache()->getUnlinkedProgramCodeBlock(
        vm, this, source(), strictMode, debuggerMode, error);

    if (globalObject->hasDebugger())
        globalObject->debugger()->sourceParsed(callFrame, source().provider(), error.line(), error.message());

    if (error.isValid())
        return error.toErrorObject(globalObject, source());

    JSValue nextPrototype = globalObject->getPrototypeDirect();
    while (nextPrototype && nextPrototype.isObject()) {
        if (UNLIKELY(asObject(nextPrototype)->type() == ProxyObjectType)) {
            ExecState* exec = globalObject->globalExec();
            return createTypeError(exec, ASCIILiteral("Proxy is not allowed in the global prototype chain."));
        }
        nextPrototype = asObject(nextPrototype)->getPrototypeDirect();
    }
    
    JSGlobalLexicalEnvironment* globalLexicalEnvironment = globalObject->globalLexicalEnvironment();
    const VariableEnvironment& variableDeclarations = unlinkedCodeBlock->variableDeclarations();
    const VariableEnvironment& lexicalDeclarations = unlinkedCodeBlock->lexicalDeclarations();
    // The ES6 spec says that no vars/global properties/let/const can be duplicated in the global scope.
    // This carried out section 15.1.8 of the ES6 spec: http://www.ecma-international.org/ecma-262/6.0/index.html#sec-globaldeclarationinstantiation
    {
        ExecState* exec = globalObject->globalExec();
        // Check for intersection of "var" and "let"/"const"/"class"
        for (auto& entry : lexicalDeclarations) {
            if (variableDeclarations.contains(entry.key))
                return createSyntaxError(exec, makeString("Can't create duplicate variable: '", String(entry.key.get()), "'"));
        }

        // Check if any new "let"/"const"/"class" will shadow any pre-existing global property names, or "var"/"let"/"const" variables.
        // It's an error to introduce a shadow.
        for (auto& entry : lexicalDeclarations) {
            bool hasProperty = globalObject->hasProperty(exec, entry.key.get());
            RETURN_IF_EXCEPTION(throwScope, throwScope.exception());
            if (hasProperty) {
                // The ES6 spec says that just RestrictedGlobalProperty can't be shadowed
                // This carried out section 8.1.1.4.14 of the ES6 spec: http://www.ecma-international.org/ecma-262/6.0/index.html#sec-hasrestrictedglobalproperty
                PropertyDescriptor descriptor;
                globalObject->getOwnPropertyDescriptor(exec, entry.key.get(), descriptor);
                
                if (descriptor.value() != jsUndefined() && !descriptor.configurable())
                    return createSyntaxError(exec, makeString("Can't create duplicate variable that shadows a global property: '", String(entry.key.get()), "'"));
            }

            hasProperty = globalLexicalEnvironment->hasProperty(exec, entry.key.get());
            RETURN_IF_EXCEPTION(throwScope, throwScope.exception());
            if (hasProperty) {
                if (UNLIKELY(entry.value.isConst() && !vm.globalConstRedeclarationShouldThrow() && !isStrictMode())) {
                    // We only allow "const" duplicate declarations under this setting.
                    // For example, we don't "let" variables to be overridden by "const" variables.
                    if (globalLexicalEnvironment->isConstVariable(entry.key.get()))
                        continue;
                }
                return createSyntaxError(exec, makeString("Can't create duplicate variable: '", String(entry.key.get()), "'"));
            }
        }

        // Check if any new "var"s will shadow any previous "let"/"const"/"class" names.
        // It's an error to introduce a shadow.
        if (!globalLexicalEnvironment->isEmpty()) {
            for (auto& entry : variableDeclarations) {
                bool hasProperty = globalLexicalEnvironment->hasProperty(exec, entry.key.get());
                RETURN_IF_EXCEPTION(throwScope, throwScope.exception());
                if (hasProperty)
                    return createSyntaxError(exec, makeString("Can't create duplicate variable: '", String(entry.key.get()), "'"));
            }
        }
    }


    m_unlinkedProgramCodeBlock.set(vm, this, unlinkedCodeBlock);

    BatchedTransitionOptimizer optimizer(vm, globalObject);

    for (size_t i = 0, numberOfFunctions = unlinkedCodeBlock->numberOfFunctionDecls(); i < numberOfFunctions; ++i) {
        UnlinkedFunctionExecutable* unlinkedFunctionExecutable = unlinkedCodeBlock->functionDecl(i);
        ASSERT(!unlinkedFunctionExecutable->name().isEmpty());
        globalObject->addFunction(callFrame, unlinkedFunctionExecutable->name());
        if (vm.typeProfiler() || vm.controlFlowProfiler()) {
            vm.functionHasExecutedCache()->insertUnexecutedRange(sourceID(), 
                unlinkedFunctionExecutable->typeProfilingStartOffset(), 
                unlinkedFunctionExecutable->typeProfilingEndOffset());
        }
    }

    for (auto& entry : variableDeclarations) {
//.........这里部分代码省略.........

// ES5 8.10.5 ToPropertyDescriptor
static bool toPropertyDescriptor(ExecState* exec, JSValue in, PropertyDescriptor& desc)
{
    if (!in.isObject()) {
        throwError(exec, createTypeError(exec, ASCIILiteral("Property description must be an object.")));
        return false;
    }
    JSObject* description = asObject(in);

    PropertySlot enumerableSlot(description);
    if (description->getPropertySlot(exec, exec->propertyNames().enumerable, enumerableSlot)) {
        desc.setEnumerable(enumerableSlot.getValue(exec, exec->propertyNames().enumerable).toBoolean(exec));
        if (exec->hadException())
            return false;
    }

    PropertySlot configurableSlot(description);
    if (description->getPropertySlot(exec, exec->propertyNames().configurable, configurableSlot)) {
        desc.setConfigurable(configurableSlot.getValue(exec, exec->propertyNames().configurable).toBoolean(exec));
        if (exec->hadException())
            return false;
    }

    JSValue value;
    PropertySlot valueSlot(description);
    if (description->getPropertySlot(exec, exec->propertyNames().value, valueSlot)) {
        desc.setValue(valueSlot.getValue(exec, exec->propertyNames().value));
        if (exec->hadException())
            return false;
    }

    PropertySlot writableSlot(description);
    if (description->getPropertySlot(exec, exec->propertyNames().writable, writableSlot)) {
        desc.setWritable(writableSlot.getValue(exec, exec->propertyNames().writable).toBoolean(exec));
        if (exec->hadException())
            return false;
    }

    PropertySlot getSlot(description);
    if (description->getPropertySlot(exec, exec->propertyNames().get, getSlot)) {
        JSValue get = getSlot.getValue(exec, exec->propertyNames().get);
        if (exec->hadException())
            return false;
        if (!get.isUndefined()) {
            CallData callData;
            if (getCallData(get, callData) == CallTypeNone) {
                throwError(exec, createTypeError(exec, ASCIILiteral("Getter must be a function.")));
                return false;
            }
        }
        desc.setGetter(get);
    }

    PropertySlot setSlot(description);
    if (description->getPropertySlot(exec, exec->propertyNames().set, setSlot)) {
        JSValue set = setSlot.getValue(exec, exec->propertyNames().set);
        if (exec->hadException())
            return false;
        if (!set.isUndefined()) {
            CallData callData;
            if (getCallData(set, callData) == CallTypeNone) {
                throwError(exec, createTypeError(exec, ASCIILiteral("Setter must be a function.")));
                return false;
            }
        }
        desc.setSetter(set);
    }

    if (!desc.isAccessorDescriptor())
        return true;

    if (desc.value()) {
        throwError(exec, createTypeError(exec, ASCIILiteral("Invalid property.  'value' present on property with getter or setter.")));
        return false;
    }

    if (desc.writablePresent()) {
        throwError(exec, createTypeError(exec, ASCIILiteral("Invalid property.  'writable' present on property with getter or setter.")));
        return false;
    }
    return true;
}