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-rw-r--r--js/src/vm/NativeObject.cpp2907
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diff --git a/js/src/vm/NativeObject.cpp b/js/src/vm/NativeObject.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "vm/NativeObject-inl.h"
+
+#include "mozilla/Casting.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
+
+#include <algorithm>
+#include <iterator>
+
+#include "gc/MaybeRooted.h"
+#include "gc/StableCellHasher.h"
+#include "js/friend/ErrorMessages.h" // js::GetErrorMessage, JSMSG_*
+#include "js/friend/StackLimits.h" // js::AutoCheckRecursionLimit
+#include "js/Printer.h" // js::GenericPrinter
+#include "js/Value.h"
+#include "vm/EqualityOperations.h" // js::SameValue
+#include "vm/GetterSetter.h" // js::GetterSetter
+#include "vm/Interpreter.h" // js::CallGetter, js::CallSetter
+#include "vm/JSONPrinter.h" // js::JSONPrinter
+#include "vm/PlainObject.h" // js::PlainObject
+#include "vm/TypedArrayObject.h"
+#include "vm/Watchtower.h"
+
+#ifdef ENABLE_RECORD_TUPLE
+# include "builtin/RecordObject.h"
+# include "builtin/TupleObject.h"
+# include "vm/RecordTupleShared.h"
+#endif
+
+#include "gc/Nursery-inl.h"
+#include "vm/JSObject-inl.h"
+#include "vm/Shape-inl.h"
+
+using namespace js;
+
+using JS::AutoCheckCannotGC;
+using mozilla::CheckedInt;
+using mozilla::PodCopy;
+using mozilla::RoundUpPow2;
+
+struct EmptyObjectElements {
+ const ObjectElements emptyElementsHeader;
+
+ // Add an extra (unused) Value to make sure an out-of-bounds index when
+ // masked (resulting in index 0) accesses valid memory.
+ const Value val;
+
+ public:
+ constexpr EmptyObjectElements()
+ : emptyElementsHeader(0, 0), val(UndefinedValue()) {}
+ explicit constexpr EmptyObjectElements(ObjectElements::SharedMemory shmem)
+ : emptyElementsHeader(0, 0, shmem), val(UndefinedValue()) {}
+};
+
+static constexpr EmptyObjectElements emptyElementsHeader;
+
+/* Objects with no elements share one empty set of elements. */
+HeapSlot* const js::emptyObjectElements = reinterpret_cast<HeapSlot*>(
+ uintptr_t(&emptyElementsHeader) + sizeof(ObjectElements));
+
+static constexpr EmptyObjectElements emptyElementsHeaderShared(
+ ObjectElements::SharedMemory::IsShared);
+
+/* Objects with no elements share one empty set of elements. */
+HeapSlot* const js::emptyObjectElementsShared = reinterpret_cast<HeapSlot*>(
+ uintptr_t(&emptyElementsHeaderShared) + sizeof(ObjectElements));
+
+struct EmptyObjectSlots : public ObjectSlots {
+ explicit constexpr EmptyObjectSlots(size_t dictionarySlotSpan)
+ : ObjectSlots(0, dictionarySlotSpan, NoUniqueIdInSharedEmptySlots) {}
+};
+
+static constexpr EmptyObjectSlots emptyObjectSlotsHeaders[17] = {
+ EmptyObjectSlots(0), EmptyObjectSlots(1), EmptyObjectSlots(2),
+ EmptyObjectSlots(3), EmptyObjectSlots(4), EmptyObjectSlots(5),
+ EmptyObjectSlots(6), EmptyObjectSlots(7), EmptyObjectSlots(8),
+ EmptyObjectSlots(9), EmptyObjectSlots(10), EmptyObjectSlots(11),
+ EmptyObjectSlots(12), EmptyObjectSlots(13), EmptyObjectSlots(14),
+ EmptyObjectSlots(15), EmptyObjectSlots(16)};
+
+static_assert(std::size(emptyObjectSlotsHeaders) ==
+ NativeObject::MAX_FIXED_SLOTS + 1);
+
+HeapSlot* const js::emptyObjectSlotsForDictionaryObject[17] = {
+ emptyObjectSlotsHeaders[0].slots(), emptyObjectSlotsHeaders[1].slots(),
+ emptyObjectSlotsHeaders[2].slots(), emptyObjectSlotsHeaders[3].slots(),
+ emptyObjectSlotsHeaders[4].slots(), emptyObjectSlotsHeaders[5].slots(),
+ emptyObjectSlotsHeaders[6].slots(), emptyObjectSlotsHeaders[7].slots(),
+ emptyObjectSlotsHeaders[8].slots(), emptyObjectSlotsHeaders[9].slots(),
+ emptyObjectSlotsHeaders[10].slots(), emptyObjectSlotsHeaders[11].slots(),
+ emptyObjectSlotsHeaders[12].slots(), emptyObjectSlotsHeaders[13].slots(),
+ emptyObjectSlotsHeaders[14].slots(), emptyObjectSlotsHeaders[15].slots(),
+ emptyObjectSlotsHeaders[16].slots()};
+
+static_assert(std::size(emptyObjectSlotsForDictionaryObject) ==
+ NativeObject::MAX_FIXED_SLOTS + 1);
+
+HeapSlot* const js::emptyObjectSlots = emptyObjectSlotsForDictionaryObject[0];
+
+#ifdef DEBUG
+
+bool NativeObject::canHaveNonEmptyElements() {
+ return !this->is<TypedArrayObject>();
+}
+
+#endif // DEBUG
+
+/* static */
+void ObjectElements::PrepareForPreventExtensions(JSContext* cx,
+ NativeObject* obj) {
+ if (!obj->hasEmptyElements()) {
+ obj->shrinkCapacityToInitializedLength(cx);
+ }
+
+ // shrinkCapacityToInitializedLength ensures there are no shifted elements.
+ MOZ_ASSERT(obj->getElementsHeader()->numShiftedElements() == 0);
+}
+
+/* static */
+void ObjectElements::PreventExtensions(NativeObject* obj) {
+ MOZ_ASSERT(!obj->isExtensible());
+ MOZ_ASSERT(obj->getElementsHeader()->numShiftedElements() == 0);
+ MOZ_ASSERT(obj->getDenseInitializedLength() == obj->getDenseCapacity());
+
+ if (!obj->hasEmptyElements()) {
+ obj->getElementsHeader()->setNotExtensible();
+ }
+}
+
+/* static */
+bool ObjectElements::FreezeOrSeal(JSContext* cx, Handle<NativeObject*> obj,
+ IntegrityLevel level) {
+ MOZ_ASSERT_IF(level == IntegrityLevel::Frozen && obj->is<ArrayObject>(),
+ !obj->as<ArrayObject>().lengthIsWritable());
+ MOZ_ASSERT(!obj->isExtensible());
+ MOZ_ASSERT(obj->getElementsHeader()->numShiftedElements() == 0);
+
+ if (obj->hasEmptyElements() || obj->denseElementsAreFrozen()) {
+ return true;
+ }
+
+ if (level == IntegrityLevel::Frozen) {
+ if (!JSObject::setFlag(cx, obj, ObjectFlag::FrozenElements)) {
+ return false;
+ }
+ }
+
+ if (!obj->denseElementsAreSealed()) {
+ obj->getElementsHeader()->seal();
+ }
+
+ if (level == IntegrityLevel::Frozen) {
+ obj->getElementsHeader()->freeze();
+ }
+
+ return true;
+}
+
+#if defined(DEBUG) || defined(JS_JITSPEW)
+
+template <typename KnownF, typename UnknownF>
+void ForEachObjectElementsFlag(uint16_t flags, KnownF known, UnknownF unknown) {
+ for (uint16_t i = 1; i; i = i << 1) {
+ if (!(flags & i)) {
+ continue;
+ }
+ switch (ObjectElements::Flags(flags & i)) {
+ case ObjectElements::Flags::FIXED:
+ known("FIXED");
+ break;
+ case ObjectElements::Flags::NONWRITABLE_ARRAY_LENGTH:
+ known("NONWRITABLE_ARRAY_LENGTH");
+ break;
+# ifdef ENABLE_RECORD_TUPLE
+ case ObjectElements::Flags::TUPLE_IS_ATOMIZED:
+ known("TUPLE_IS_ATOMIZED");
+ break;
+# endif
+ case ObjectElements::Flags::SHARED_MEMORY:
+ known("SHARED_MEMORY");
+ break;
+ case ObjectElements::Flags::NOT_EXTENSIBLE:
+ known("NOT_EXTENSIBLE");
+ break;
+ case ObjectElements::Flags::SEALED:
+ known("SEALED");
+ break;
+ case ObjectElements::Flags::FROZEN:
+ known("FROZEN");
+ break;
+ case ObjectElements::Flags::NON_PACKED:
+ known("NON_PACKED");
+ break;
+ case ObjectElements::Flags::MAYBE_IN_ITERATION:
+ known("MAYBE_IN_ITERATION");
+ break;
+ default:
+ unknown(i);
+ break;
+ }
+ }
+}
+
+void ObjectElements::dumpStringContent(js::GenericPrinter& out) const {
+ out.printf("<(js::ObjectElements*)0x%p, flags=[", this);
+
+ bool first = true;
+ ForEachObjectElementsFlag(
+ flags,
+ [&](const char* name) {
+ if (!first) {
+ out.put(", ");
+ }
+ first = false;
+
+ out.put(name);
+ },
+ [&](uint16_t value) {
+ if (!first) {
+ out.put(", ");
+ }
+ first = false;
+
+ out.printf("Unknown(%04x)", value);
+ });
+ out.put("]");
+
+ out.printf(", init=%u, capacity=%u, length=%u>", initializedLength, capacity,
+ length);
+}
+#endif
+
+#ifdef DEBUG
+static mozilla::Atomic<bool, mozilla::Relaxed> gShapeConsistencyChecksEnabled(
+ false);
+
+/* static */
+void js::NativeObject::enableShapeConsistencyChecks() {
+ gShapeConsistencyChecksEnabled = true;
+}
+
+void js::NativeObject::checkShapeConsistency() {
+ if (!gShapeConsistencyChecksEnabled) {
+ return;
+ }
+
+ MOZ_ASSERT(is<NativeObject>());
+
+ if (PropMap* map = shape()->propMap()) {
+ map->checkConsistency(this);
+ } else {
+ MOZ_ASSERT(shape()->propMapLength() == 0);
+ }
+}
+#endif
+
+#ifdef DEBUG
+
+bool js::NativeObject::slotInRange(uint32_t slot,
+ SentinelAllowed sentinel) const {
+ MOZ_ASSERT(!gc::IsForwarded(shape()));
+ uint32_t capacity = numFixedSlots() + numDynamicSlots();
+ if (sentinel == SENTINEL_ALLOWED) {
+ return slot <= capacity;
+ }
+ return slot < capacity;
+}
+
+bool js::NativeObject::slotIsFixed(uint32_t slot) const {
+ // We call numFixedSlotsMaybeForwarded() to allow reading slots of
+ // associated objects in trace hooks that may be called during a moving GC.
+ return slot < numFixedSlotsMaybeForwarded();
+}
+
+bool js::NativeObject::isNumFixedSlots(uint32_t nfixed) const {
+ // We call numFixedSlotsMaybeForwarded() to allow reading slots of
+ // associated objects in trace hooks that may be called during a moving GC.
+ return nfixed == numFixedSlotsMaybeForwarded();
+}
+
+uint32_t js::NativeObject::outOfLineNumDynamicSlots() const {
+ return numDynamicSlots();
+}
+#endif /* DEBUG */
+
+mozilla::Maybe<PropertyInfo> js::NativeObject::lookup(JSContext* cx, jsid id) {
+ MOZ_ASSERT(is<NativeObject>());
+ uint32_t index;
+ if (PropMap* map = shape()->lookup(cx, id, &index)) {
+ return mozilla::Some(map->getPropertyInfo(index));
+ }
+ return mozilla::Nothing();
+}
+
+mozilla::Maybe<PropertyInfo> js::NativeObject::lookupPure(jsid id) {
+ MOZ_ASSERT(is<NativeObject>());
+ uint32_t index;
+ if (PropMap* map = shape()->lookupPure(id, &index)) {
+ return mozilla::Some(map->getPropertyInfo(index));
+ }
+ return mozilla::Nothing();
+}
+
+bool NativeObject::setUniqueId(JSContext* cx, uint64_t uid) {
+ MOZ_ASSERT(!hasUniqueId());
+ MOZ_ASSERT(!gc::HasUniqueId(this));
+
+ return setOrUpdateUniqueId(cx, uid);
+}
+
+bool NativeObject::setOrUpdateUniqueId(JSContext* cx, uint64_t uid) {
+ if (!hasDynamicSlots() && !allocateSlots(cx, 0)) {
+ return false;
+ }
+
+ getSlotsHeader()->setUniqueId(uid);
+
+ return true;
+}
+
+bool NativeObject::growSlots(JSContext* cx, uint32_t oldCapacity,
+ uint32_t newCapacity) {
+ MOZ_ASSERT(newCapacity > oldCapacity);
+
+ /*
+ * Slot capacities are determined by the span of allocated objects. Due to
+ * the limited number of bits to store shape slots, object growth is
+ * throttled well before the slot capacity can overflow.
+ */
+ NativeObject::slotsSizeMustNotOverflow();
+ MOZ_ASSERT(newCapacity <= MAX_SLOTS_COUNT);
+
+ if (!hasDynamicSlots()) {
+ return allocateSlots(cx, newCapacity);
+ }
+
+ uint64_t uid = maybeUniqueId();
+
+ uint32_t newAllocated = ObjectSlots::allocCount(newCapacity);
+
+ uint32_t dictionarySpan = getSlotsHeader()->dictionarySlotSpan();
+
+ uint32_t oldAllocated = ObjectSlots::allocCount(oldCapacity);
+
+ ObjectSlots* oldHeaderSlots = ObjectSlots::fromSlots(slots_);
+ MOZ_ASSERT(oldHeaderSlots->capacity() == oldCapacity);
+
+ HeapSlot* allocation = ReallocateCellBuffer<HeapSlot>(
+ cx, this, reinterpret_cast<HeapSlot*>(oldHeaderSlots), oldAllocated,
+ newAllocated, js::MallocArena);
+ if (!allocation) {
+ return false; /* Leave slots at its old size. */
+ }
+
+ auto* newHeaderSlots =
+ new (allocation) ObjectSlots(newCapacity, dictionarySpan, uid);
+ slots_ = newHeaderSlots->slots();
+
+ Debug_SetSlotRangeToCrashOnTouch(slots_ + oldCapacity,
+ newCapacity - oldCapacity);
+
+ RemoveCellMemory(this, ObjectSlots::allocSize(oldCapacity),
+ MemoryUse::ObjectSlots);
+ AddCellMemory(this, ObjectSlots::allocSize(newCapacity),
+ MemoryUse::ObjectSlots);
+
+ MOZ_ASSERT(hasDynamicSlots());
+ return true;
+}
+
+bool NativeObject::growSlotsForNewSlot(JSContext* cx, uint32_t numFixed,
+ uint32_t slot) {
+ MOZ_ASSERT(slotSpan() == slot);
+ MOZ_ASSERT(shape()->numFixedSlots() == numFixed);
+ MOZ_ASSERT(slot >= numFixed);
+
+ uint32_t newCapacity = calculateDynamicSlots(numFixed, slot + 1, getClass());
+
+ uint32_t oldCapacity = numDynamicSlots();
+ MOZ_ASSERT(oldCapacity < newCapacity);
+
+ return growSlots(cx, oldCapacity, newCapacity);
+}
+
+bool NativeObject::allocateInitialSlots(JSContext* cx, uint32_t capacity) {
+ uint32_t count = ObjectSlots::allocCount(capacity);
+ HeapSlot* allocation = AllocateCellBuffer<HeapSlot>(cx, this, count);
+ if (MOZ_UNLIKELY(!allocation)) {
+ // The new object will be unreachable, but we have to make it safe for
+ // finalization. It can also be observed with dumpHeap().
+ // Give it a dummy shape that has no dynamic slots.
+ setShape(GlobalObject::getEmptyPlainObjectShape(cx));
+ initEmptyDynamicSlots();
+ return false;
+ }
+
+ auto* headerSlots = new (allocation)
+ ObjectSlots(capacity, 0, ObjectSlots::NoUniqueIdInDynamicSlots);
+ slots_ = headerSlots->slots();
+
+ Debug_SetSlotRangeToCrashOnTouch(slots_, capacity);
+
+ if (!IsInsideNursery(this)) {
+ AddCellMemory(this, ObjectSlots::allocSize(capacity),
+ MemoryUse::ObjectSlots);
+ }
+
+ MOZ_ASSERT(hasDynamicSlots());
+ return true;
+}
+
+bool NativeObject::allocateSlots(JSContext* cx, uint32_t newCapacity) {
+ MOZ_ASSERT(!hasUniqueId());
+ MOZ_ASSERT(!hasDynamicSlots());
+
+ uint32_t newAllocated = ObjectSlots::allocCount(newCapacity);
+
+ uint32_t dictionarySpan = getSlotsHeader()->dictionarySlotSpan();
+
+ HeapSlot* allocation = AllocateCellBuffer<HeapSlot>(cx, this, newAllocated);
+ if (!allocation) {
+ return false;
+ }
+
+ auto* newHeaderSlots = new (allocation) ObjectSlots(
+ newCapacity, dictionarySpan, ObjectSlots::NoUniqueIdInDynamicSlots);
+ slots_ = newHeaderSlots->slots();
+
+ Debug_SetSlotRangeToCrashOnTouch(slots_, newCapacity);
+
+ AddCellMemory(this, ObjectSlots::allocSize(newCapacity),
+ MemoryUse::ObjectSlots);
+
+ MOZ_ASSERT(hasDynamicSlots());
+ return true;
+}
+
+/* static */
+bool NativeObject::growSlotsPure(JSContext* cx, NativeObject* obj,
+ uint32_t newCapacity) {
+ // IC code calls this directly.
+ AutoUnsafeCallWithABI unsafe;
+
+ if (!obj->growSlots(cx, obj->numDynamicSlots(), newCapacity)) {
+ cx->recoverFromOutOfMemory();
+ return false;
+ }
+
+ return true;
+}
+
+/* static */
+bool NativeObject::addDenseElementPure(JSContext* cx, NativeObject* obj) {
+ // IC code calls this directly.
+ AutoUnsafeCallWithABI unsafe;
+
+ MOZ_ASSERT(obj->getDenseInitializedLength() == obj->getDenseCapacity());
+ MOZ_ASSERT(obj->isExtensible());
+ MOZ_ASSERT(!obj->isIndexed());
+ MOZ_ASSERT(!obj->is<TypedArrayObject>());
+ MOZ_ASSERT_IF(obj->is<ArrayObject>(),
+ obj->as<ArrayObject>().lengthIsWritable());
+
+ // growElements will report OOM also if the number of dense elements will
+ // exceed MAX_DENSE_ELEMENTS_COUNT. See goodElementsAllocationAmount.
+ uint32_t oldCapacity = obj->getDenseCapacity();
+ if (MOZ_UNLIKELY(!obj->growElements(cx, oldCapacity + 1))) {
+ cx->recoverFromOutOfMemory();
+ return false;
+ }
+
+ MOZ_ASSERT(obj->getDenseCapacity() > oldCapacity);
+ MOZ_ASSERT(obj->getDenseCapacity() <= MAX_DENSE_ELEMENTS_COUNT);
+ return true;
+}
+
+static inline void FreeSlots(JSContext* cx, NativeObject* obj,
+ ObjectSlots* slots, size_t nbytes) {
+ // Note: this is called when shrinking slots, not from the finalizer.
+ if (obj->isTenured()) {
+ MOZ_ASSERT(!cx->nursery().isInside(slots));
+ js_free(slots);
+ } else {
+ cx->nursery().freeBuffer(slots, nbytes);
+ }
+}
+
+void NativeObject::shrinkSlots(JSContext* cx, uint32_t oldCapacity,
+ uint32_t newCapacity) {
+ MOZ_ASSERT(hasDynamicSlots());
+ MOZ_ASSERT(newCapacity < oldCapacity);
+ MOZ_ASSERT(oldCapacity == getSlotsHeader()->capacity());
+
+ ObjectSlots* oldHeaderSlots = ObjectSlots::fromSlots(slots_);
+ MOZ_ASSERT(oldHeaderSlots->capacity() == oldCapacity);
+
+ uint64_t uid = maybeUniqueId();
+
+ uint32_t oldAllocated = ObjectSlots::allocCount(oldCapacity);
+
+ if (newCapacity == 0 && uid == 0) {
+ size_t nbytes = ObjectSlots::allocSize(oldCapacity);
+ RemoveCellMemory(this, nbytes, MemoryUse::ObjectSlots);
+ FreeSlots(cx, this, oldHeaderSlots, nbytes);
+ // dictionarySlotSpan is initialized to the correct value by the callers.
+ setEmptyDynamicSlots(0);
+ return;
+ }
+
+ MOZ_ASSERT_IF(!is<ArrayObject>() && !hasUniqueId(),
+ newCapacity >= SLOT_CAPACITY_MIN);
+
+ uint32_t dictionarySpan = getSlotsHeader()->dictionarySlotSpan();
+
+ uint32_t newAllocated = ObjectSlots::allocCount(newCapacity);
+
+ HeapSlot* allocation = ReallocateCellBuffer<HeapSlot>(
+ cx, this, reinterpret_cast<HeapSlot*>(oldHeaderSlots), oldAllocated,
+ newAllocated, js::MallocArena);
+ if (!allocation) {
+ // It's possible for realloc to fail when shrinking an allocation. In this
+ // case we continue using the original allocation but still update the
+ // capacity to the new requested capacity, which is smaller than the actual
+ // capacity.
+ cx->recoverFromOutOfMemory();
+ allocation = reinterpret_cast<HeapSlot*>(getSlotsHeader());
+ }
+
+ RemoveCellMemory(this, ObjectSlots::allocSize(oldCapacity),
+ MemoryUse::ObjectSlots);
+ AddCellMemory(this, ObjectSlots::allocSize(newCapacity),
+ MemoryUse::ObjectSlots);
+
+ auto* newHeaderSlots =
+ new (allocation) ObjectSlots(newCapacity, dictionarySpan, uid);
+ slots_ = newHeaderSlots->slots();
+}
+
+void NativeObject::initFixedElements(gc::AllocKind kind, uint32_t length) {
+ uint32_t capacity =
+ gc::GetGCKindSlots(kind) - ObjectElements::VALUES_PER_HEADER;
+
+ setFixedElements();
+ new (getElementsHeader()) ObjectElements(capacity, length);
+ getElementsHeader()->flags |= ObjectElements::FIXED;
+
+ MOZ_ASSERT(hasFixedElements());
+}
+
+bool NativeObject::willBeSparseElements(uint32_t requiredCapacity,
+ uint32_t newElementsHint) {
+ MOZ_ASSERT(is<NativeObject>());
+ MOZ_ASSERT(requiredCapacity > MIN_SPARSE_INDEX);
+
+ uint32_t cap = getDenseCapacity();
+ MOZ_ASSERT(requiredCapacity >= cap);
+
+ if (requiredCapacity > MAX_DENSE_ELEMENTS_COUNT) {
+ return true;
+ }
+
+ uint32_t minimalDenseCount = requiredCapacity / SPARSE_DENSITY_RATIO;
+ if (newElementsHint >= minimalDenseCount) {
+ return false;
+ }
+ minimalDenseCount -= newElementsHint;
+
+ if (minimalDenseCount > cap) {
+ return true;
+ }
+
+ uint32_t len = getDenseInitializedLength();
+ const Value* elems = getDenseElements();
+ for (uint32_t i = 0; i < len; i++) {
+ if (!elems[i].isMagic(JS_ELEMENTS_HOLE) && !--minimalDenseCount) {
+ return false;
+ }
+ }
+ return true;
+}
+
+/* static */
+DenseElementResult NativeObject::maybeDensifySparseElements(
+ JSContext* cx, Handle<NativeObject*> obj) {
+ /*
+ * Wait until after the object goes into dictionary mode, which must happen
+ * when sparsely packing any array with more than MIN_SPARSE_INDEX elements
+ * (see PropertyTree::MAX_HEIGHT).
+ */
+ if (!obj->inDictionaryMode()) {
+ return DenseElementResult::Incomplete;
+ }
+
+ /*
+ * Only measure the number of indexed properties every log(n) times when
+ * populating the object.
+ */
+ uint32_t slotSpan = obj->slotSpan();
+ if (slotSpan != RoundUpPow2(slotSpan)) {
+ return DenseElementResult::Incomplete;
+ }
+
+ /* Watch for conditions under which an object's elements cannot be dense. */
+ if (!obj->isExtensible()) {
+ return DenseElementResult::Incomplete;
+ }
+
+ /*
+ * The indexes in the object need to be sufficiently dense before they can
+ * be converted to dense mode.
+ */
+ uint32_t numDenseElements = 0;
+ uint32_t newInitializedLength = 0;
+
+ for (ShapePropertyIter<NoGC> iter(obj->shape()); !iter.done(); iter++) {
+ uint32_t index;
+ if (!IdIsIndex(iter->key(), &index)) {
+ continue;
+ }
+ if (iter->flags() != PropertyFlags::defaultDataPropFlags) {
+ // For simplicity, only densify the object if all indexed properties can
+ // be converted to dense elements.
+ return DenseElementResult::Incomplete;
+ }
+ MOZ_ASSERT(iter->isDataProperty());
+ numDenseElements++;
+ newInitializedLength = std::max(newInitializedLength, index + 1);
+ }
+
+ if (numDenseElements * SPARSE_DENSITY_RATIO < newInitializedLength) {
+ return DenseElementResult::Incomplete;
+ }
+
+ if (newInitializedLength > MAX_DENSE_ELEMENTS_COUNT) {
+ return DenseElementResult::Incomplete;
+ }
+
+ /*
+ * This object meets all necessary restrictions, convert all indexed
+ * properties into dense elements.
+ */
+
+ if (newInitializedLength > obj->getDenseCapacity()) {
+ if (!obj->growElements(cx, newInitializedLength)) {
+ return DenseElementResult::Failure;
+ }
+ }
+
+ obj->ensureDenseInitializedLength(newInitializedLength, 0);
+
+ if (obj->compartment()->objectMaybeInIteration(obj)) {
+ // Mark the densified elements as maybe-in-iteration. See also the comment
+ // in GetIterator.
+ obj->markDenseElementsMaybeInIteration();
+ }
+
+ if (!NativeObject::densifySparseElements(cx, obj)) {
+ return DenseElementResult::Failure;
+ }
+
+ return DenseElementResult::Success;
+}
+
+void NativeObject::moveShiftedElements() {
+ MOZ_ASSERT(isExtensible());
+
+ ObjectElements* header = getElementsHeader();
+ uint32_t numShifted = header->numShiftedElements();
+ MOZ_ASSERT(numShifted > 0);
+
+ uint32_t initLength = header->initializedLength;
+
+ ObjectElements* newHeader =
+ static_cast<ObjectElements*>(getUnshiftedElementsHeader());
+ memmove(newHeader, header, sizeof(ObjectElements));
+
+ newHeader->clearShiftedElements();
+ newHeader->capacity += numShifted;
+ elements_ = newHeader->elements();
+
+ // To move the elements, temporarily update initializedLength to include
+ // the shifted elements.
+ newHeader->initializedLength += numShifted;
+
+ // Move the elements. Initialize to |undefined| to ensure pre-barriers
+ // don't see garbage.
+ for (size_t i = 0; i < numShifted; i++) {
+ initDenseElement(i, UndefinedValue());
+ }
+ moveDenseElements(0, numShifted, initLength);
+
+ // Restore the initialized length. We use setDenseInitializedLength to
+ // make sure prepareElementRangeForOverwrite is called on the shifted
+ // elements.
+ setDenseInitializedLength(initLength);
+}
+
+void NativeObject::maybeMoveShiftedElements() {
+ MOZ_ASSERT(isExtensible());
+
+ ObjectElements* header = getElementsHeader();
+ MOZ_ASSERT(header->numShiftedElements() > 0);
+
+ // Move the elements if less than a third of the allocated space is in use.
+ if (header->capacity < header->numAllocatedElements() / 3) {
+ moveShiftedElements();
+ }
+}
+
+bool NativeObject::tryUnshiftDenseElements(uint32_t count) {
+ MOZ_ASSERT(isExtensible());
+ MOZ_ASSERT(count > 0);
+
+ ObjectElements* header = getElementsHeader();
+ uint32_t numShifted = header->numShiftedElements();
+
+ if (count > numShifted) {
+ // We need more elements than are easily available. Try to make space
+ // for more elements than we need (and shift the remaining ones) so
+ // that unshifting more elements later will be fast.
+
+ // Don't bother reserving elements if the number of elements is small.
+ // Note that there's no technical reason for using this particular
+ // limit.
+ if (header->initializedLength <= 10 ||
+ header->hasNonwritableArrayLength() ||
+ MOZ_UNLIKELY(count > ObjectElements::MaxShiftedElements)) {
+ return false;
+ }
+
+ MOZ_ASSERT(header->capacity >= header->initializedLength);
+ uint32_t unusedCapacity = header->capacity - header->initializedLength;
+
+ // Determine toShift, the number of extra elements we want to make
+ // available.
+ uint32_t toShift = count - numShifted;
+ MOZ_ASSERT(toShift <= ObjectElements::MaxShiftedElements,
+ "count <= MaxShiftedElements so toShift <= MaxShiftedElements");
+
+ // Give up if we need to allocate more elements.
+ if (toShift > unusedCapacity) {
+ return false;
+ }
+
+ // Move more elements than we need, so that other unshift calls will be
+ // fast. We just have to make sure we don't exceed unusedCapacity.
+ toShift = std::min(toShift + unusedCapacity / 2, unusedCapacity);
+
+ // Ensure |numShifted + toShift| does not exceed MaxShiftedElements.
+ if (numShifted + toShift > ObjectElements::MaxShiftedElements) {
+ toShift = ObjectElements::MaxShiftedElements - numShifted;
+ }
+
+ MOZ_ASSERT(count <= numShifted + toShift);
+ MOZ_ASSERT(numShifted + toShift <= ObjectElements::MaxShiftedElements);
+ MOZ_ASSERT(toShift <= unusedCapacity);
+
+ // Now move/unshift the elements.
+ uint32_t initLen = header->initializedLength;
+ setDenseInitializedLength(initLen + toShift);
+ for (uint32_t i = 0; i < toShift; i++) {
+ initDenseElement(initLen + i, UndefinedValue());
+ }
+ moveDenseElements(toShift, 0, initLen);
+
+ // Shift the elements we just prepended.
+ shiftDenseElementsUnchecked(toShift);
+
+ // We can now fall-through to the fast path below.
+ header = getElementsHeader();
+ MOZ_ASSERT(header->numShiftedElements() == numShifted + toShift);
+
+ numShifted = header->numShiftedElements();
+ MOZ_ASSERT(count <= numShifted);
+ }
+
+ elements_ -= count;
+ ObjectElements* newHeader = getElementsHeader();
+ memmove(newHeader, header, sizeof(ObjectElements));
+
+ newHeader->unshiftShiftedElements(count);
+
+ // Initialize to |undefined| to ensure pre-barriers don't see garbage.
+ for (uint32_t i = 0; i < count; i++) {
+ initDenseElement(i, UndefinedValue());
+ }
+
+ return true;
+}
+
+// Given a requested capacity (in elements) and (potentially) the length of an
+// array for which elements are being allocated, compute an actual allocation
+// amount (in elements). (Allocation amounts include space for an
+// ObjectElements instance, so a return value of |N| implies
+// |N - ObjectElements::VALUES_PER_HEADER| usable elements.)
+//
+// The requested/actual allocation distinction is meant to:
+//
+// * preserve amortized O(N) time to add N elements;
+// * minimize the number of unused elements beyond an array's length, and
+// * provide at least ELEMENT_CAPACITY_MIN elements no matter what (so adding
+// the first several elements to small arrays only needs one allocation).
+//
+// Note: the structure and behavior of this method follow along with
+// UnboxedArrayObject::chooseCapacityIndex. Changes to the allocation strategy
+// in one should generally be matched by the other.
+/* static */
+bool NativeObject::goodElementsAllocationAmount(JSContext* cx,
+ uint32_t reqCapacity,
+ uint32_t length,
+ uint32_t* goodAmount) {
+ if (reqCapacity > MAX_DENSE_ELEMENTS_COUNT) {
+ ReportOutOfMemory(cx);
+ return false;
+ }
+
+ uint32_t reqAllocated = reqCapacity + ObjectElements::VALUES_PER_HEADER;
+
+ // Handle "small" requests primarily by doubling.
+ const uint32_t Mebi = 1 << 20;
+ if (reqAllocated < Mebi) {
+ uint32_t amount =
+ mozilla::AssertedCast<uint32_t>(RoundUpPow2(reqAllocated));
+
+ // If |amount| would be 2/3 or more of the array's length, adjust
+ // it (up or down) to be equal to the array's length. This avoids
+ // allocating excess elements that aren't likely to be needed, either
+ // in this resizing or a subsequent one. The 2/3 factor is chosen so
+ // that exceptional resizings will at most triple the capacity, as
+ // opposed to the usual doubling.
+ uint32_t goodCapacity = amount - ObjectElements::VALUES_PER_HEADER;
+ if (length >= reqCapacity && goodCapacity > (length / 3) * 2) {
+ amount = length + ObjectElements::VALUES_PER_HEADER;
+ }
+
+ if (amount < ELEMENT_CAPACITY_MIN) {
+ amount = ELEMENT_CAPACITY_MIN;
+ }
+
+ *goodAmount = amount;
+
+ return true;
+ }
+
+ // The almost-doubling above wastes a lot of space for larger bucket sizes.
+ // For large amounts, switch to bucket sizes that obey this formula:
+ //
+ // count(n+1) = Math.ceil(count(n) * 1.125)
+ //
+ // where |count(n)| is the size of the nth bucket, measured in 2**20 slots.
+ // These bucket sizes still preserve amortized O(N) time to add N elements,
+ // just with a larger constant factor.
+ //
+ // The bucket size table below was generated with this JavaScript (and
+ // manual reformatting):
+ //
+ // for (let n = 1, i = 0; i < 34; i++) {
+ // print('0x' + (n * (1 << 20)).toString(16) + ', ');
+ // n = Math.ceil(n * 1.125);
+ // }
+ static constexpr uint32_t BigBuckets[] = {
+ 0x100000, 0x200000, 0x300000, 0x400000, 0x500000, 0x600000,
+ 0x700000, 0x800000, 0x900000, 0xb00000, 0xd00000, 0xf00000,
+ 0x1100000, 0x1400000, 0x1700000, 0x1a00000, 0x1e00000, 0x2200000,
+ 0x2700000, 0x2c00000, 0x3200000, 0x3900000, 0x4100000, 0x4a00000,
+ 0x5400000, 0x5f00000, 0x6b00000, 0x7900000, 0x8900000, 0x9b00000,
+ 0xaf00000, 0xc500000, 0xde00000, 0xfa00000};
+ static_assert(BigBuckets[std::size(BigBuckets) - 1] <=
+ MAX_DENSE_ELEMENTS_ALLOCATION);
+
+ // Pick the first bucket that'll fit |reqAllocated|.
+ for (uint32_t b : BigBuckets) {
+ if (b >= reqAllocated) {
+ *goodAmount = b;
+ return true;
+ }
+ }
+
+ // Otherwise, return the maximum bucket size.
+ *goodAmount = MAX_DENSE_ELEMENTS_ALLOCATION;
+ return true;
+}
+
+bool NativeObject::growElements(JSContext* cx, uint32_t reqCapacity) {
+ MOZ_ASSERT(isExtensible());
+ MOZ_ASSERT(canHaveNonEmptyElements());
+
+ // If there are shifted elements, consider moving them first. If we don't
+ // move them here, the code below will include the shifted elements in the
+ // resize.
+ uint32_t numShifted = getElementsHeader()->numShiftedElements();
+ if (numShifted > 0) {
+ // If the number of elements is small, it's cheaper to just move them as
+ // it may avoid a malloc/realloc. Note that there's no technical reason
+ // for using this particular value, but it works well in real-world use
+ // cases.
+ static const size_t MaxElementsToMoveEagerly = 20;
+
+ if (getElementsHeader()->initializedLength <= MaxElementsToMoveEagerly) {
+ moveShiftedElements();
+ } else {
+ maybeMoveShiftedElements();
+ }
+ if (getDenseCapacity() >= reqCapacity) {
+ return true;
+ }
+ // moveShiftedElements() may have changed the number of shifted elements;
+ // update `numShifted` accordingly.
+ numShifted = getElementsHeader()->numShiftedElements();
+
+ // If |reqCapacity + numShifted| overflows, we just move all shifted
+ // elements to avoid the problem.
+ CheckedInt<uint32_t> checkedReqCapacity(reqCapacity);
+ checkedReqCapacity += numShifted;
+ if (MOZ_UNLIKELY(!checkedReqCapacity.isValid())) {
+ moveShiftedElements();
+ numShifted = 0;
+ }
+ }
+
+ uint32_t oldCapacity = getDenseCapacity();
+ MOZ_ASSERT(oldCapacity < reqCapacity);
+
+ uint32_t newAllocated = 0;
+ if (is<ArrayObject>() && !as<ArrayObject>().lengthIsWritable()) {
+ // Preserve the |capacity <= length| invariant for arrays with
+ // non-writable length. See also js::ArraySetLength which initially
+ // enforces this requirement.
+ MOZ_ASSERT(reqCapacity <= as<ArrayObject>().length());
+ // Adding to reqCapacity must not overflow uint32_t.
+ MOZ_ASSERT(reqCapacity <= MAX_DENSE_ELEMENTS_COUNT);
+
+ // Then, add the header and shifted elements sizes to the new capacity
+ // to get the overall amount to allocate.
+ newAllocated = reqCapacity + numShifted + ObjectElements::VALUES_PER_HEADER;
+ } else {
+ // For arrays with writable length, and all non-Array objects, call
+ // `NativeObject::goodElementsAllocationAmount()` to determine the
+ // amount to allocate from the the requested capacity and existing length.
+ if (!goodElementsAllocationAmount(cx, reqCapacity + numShifted,
+ getElementsHeader()->length,
+ &newAllocated)) {
+ return false;
+ }
+ }
+
+ // newAllocated now contains the size of the buffer we need to allocate;
+ // subtract off the header and shifted elements size to get the new capacity
+ uint32_t newCapacity =
+ newAllocated - ObjectElements::VALUES_PER_HEADER - numShifted;
+ // If the new capacity isn't strictly greater than the old capacity, then this
+ // method shouldn't have been called; if the new capacity doesn't satisfy
+ // what was requested, then one of the calculations above must have been
+ // wrong.
+ MOZ_ASSERT(newCapacity > oldCapacity && newCapacity >= reqCapacity);
+
+ // If newCapacity exceeds MAX_DENSE_ELEMENTS_COUNT, the array should become
+ // sparse.
+ MOZ_ASSERT(newCapacity <= MAX_DENSE_ELEMENTS_COUNT);
+
+ uint32_t initlen = getDenseInitializedLength();
+
+ HeapSlot* oldHeaderSlots =
+ reinterpret_cast<HeapSlot*>(getUnshiftedElementsHeader());
+ HeapSlot* newHeaderSlots;
+ uint32_t oldAllocated = 0;
+ if (hasDynamicElements()) {
+ // If the object has dynamic elements, then we might be able to resize the
+ // buffer in-place.
+
+ // First, check that adding to oldCapacity won't overflow uint32_t
+ MOZ_ASSERT(oldCapacity <= MAX_DENSE_ELEMENTS_COUNT);
+ // Then, add the header and shifted elements sizes to get the overall size
+ // of the existing buffer
+ oldAllocated = oldCapacity + ObjectElements::VALUES_PER_HEADER + numShifted;
+
+ // Finally, try to resize the buffer.
+ newHeaderSlots = ReallocateCellBuffer<HeapSlot>(
+ cx, this, oldHeaderSlots, oldAllocated, newAllocated, js::MallocArena);
+ if (!newHeaderSlots) {
+ return false; // If the resizing failed, then we leave elements at its
+ // old size.
+ }
+ } else {
+ // If the object has fixed elements, then we always need to allocate a new
+ // buffer, because if we've reached this code, then the requested capacity
+ // is greater than the existing inline space available within the object
+ newHeaderSlots = AllocateCellBuffer<HeapSlot>(cx, this, newAllocated);
+ if (!newHeaderSlots) {
+ return false; // Leave elements at its old size.
+ }
+
+ // Copy the initialized elements into the new buffer,
+ PodCopy(newHeaderSlots, oldHeaderSlots,
+ ObjectElements::VALUES_PER_HEADER + initlen + numShifted);
+ }
+
+ // If the object already had dynamic elements, then we have to account
+ // for freeing the old elements buffer.
+ if (oldAllocated) {
+ RemoveCellMemory(this, oldAllocated * sizeof(HeapSlot),
+ MemoryUse::ObjectElements);
+ }
+
+ ObjectElements* newheader = reinterpret_cast<ObjectElements*>(newHeaderSlots);
+ // Update the elements pointer to point to the new elements buffer.
+ elements_ = newheader->elements() + numShifted;
+
+ // Clear the "fixed elements" flag, because if this code has been reached,
+ // this object now has dynamic elements.
+ getElementsHeader()->flags &= ~ObjectElements::FIXED;
+ getElementsHeader()->capacity = newCapacity;
+
+ // Poison the uninitialized portion of the new elements buffer.
+ Debug_SetSlotRangeToCrashOnTouch(elements_ + initlen, newCapacity - initlen);
+
+ // Account for allocating the new elements buffer.
+ AddCellMemory(this, newAllocated * sizeof(HeapSlot),
+ MemoryUse::ObjectElements);
+
+ return true;
+}
+
+void NativeObject::shrinkElements(JSContext* cx, uint32_t reqCapacity) {
+ MOZ_ASSERT(canHaveNonEmptyElements());
+ MOZ_ASSERT(reqCapacity >= getDenseInitializedLength());
+
+ if (!hasDynamicElements()) {
+ return;
+ }
+
+ // If we have shifted elements, consider moving them.
+ uint32_t numShifted = getElementsHeader()->numShiftedElements();
+ if (numShifted > 0) {
+ maybeMoveShiftedElements();
+ numShifted = getElementsHeader()->numShiftedElements();
+ }
+
+ uint32_t oldCapacity = getDenseCapacity();
+ MOZ_ASSERT(reqCapacity < oldCapacity);
+
+ uint32_t newAllocated = 0;
+ MOZ_ALWAYS_TRUE(goodElementsAllocationAmount(cx, reqCapacity + numShifted, 0,
+ &newAllocated));
+ MOZ_ASSERT(oldCapacity <= MAX_DENSE_ELEMENTS_COUNT);
+
+ uint32_t oldAllocated =
+ oldCapacity + ObjectElements::VALUES_PER_HEADER + numShifted;
+ if (newAllocated == oldAllocated) {
+ return; // Leave elements at its old size.
+ }
+
+ MOZ_ASSERT(newAllocated > ObjectElements::VALUES_PER_HEADER);
+ uint32_t newCapacity =
+ newAllocated - ObjectElements::VALUES_PER_HEADER - numShifted;
+ MOZ_ASSERT(newCapacity <= MAX_DENSE_ELEMENTS_COUNT);
+
+ HeapSlot* oldHeaderSlots =
+ reinterpret_cast<HeapSlot*>(getUnshiftedElementsHeader());
+ HeapSlot* newHeaderSlots = ReallocateCellBuffer<HeapSlot>(
+ cx, this, oldHeaderSlots, oldAllocated, newAllocated, js::MallocArena);
+ if (!newHeaderSlots) {
+ cx->recoverFromOutOfMemory();
+ return; // Leave elements at its old size.
+ }
+
+ RemoveCellMemory(this, oldAllocated * sizeof(HeapSlot),
+ MemoryUse::ObjectElements);
+
+ ObjectElements* newheader = reinterpret_cast<ObjectElements*>(newHeaderSlots);
+ elements_ = newheader->elements() + numShifted;
+ getElementsHeader()->capacity = newCapacity;
+
+ AddCellMemory(this, newAllocated * sizeof(HeapSlot),
+ MemoryUse::ObjectElements);
+}
+
+void NativeObject::shrinkCapacityToInitializedLength(JSContext* cx) {
+ // When an array's length becomes non-writable, writes to indexes greater
+ // greater than or equal to the length don't change the array. We handle this
+ // with a check for non-writable length in most places. But in JIT code every
+ // check counts -- so we piggyback the check on the already-required range
+ // check for |index < capacity| by making capacity of arrays with non-writable
+ // length never exceed the length. This mechanism is also used when an object
+ // becomes non-extensible.
+
+ if (getElementsHeader()->numShiftedElements() > 0) {
+ moveShiftedElements();
+ }
+
+ ObjectElements* header = getElementsHeader();
+ uint32_t len = header->initializedLength;
+ MOZ_ASSERT(header->capacity >= len);
+ if (header->capacity == len) {
+ return;
+ }
+
+ shrinkElements(cx, len);
+
+ header = getElementsHeader();
+ uint32_t oldAllocated = header->numAllocatedElements();
+ header->capacity = len;
+
+ // The size of the memory allocation hasn't changed but we lose the actual
+ // capacity information. Make the associated size match the updated capacity.
+ if (!hasFixedElements()) {
+ uint32_t newAllocated = header->numAllocatedElements();
+ RemoveCellMemory(this, oldAllocated * sizeof(HeapSlot),
+ MemoryUse::ObjectElements);
+ AddCellMemory(this, newAllocated * sizeof(HeapSlot),
+ MemoryUse::ObjectElements);
+ }
+}
+
+/* static */
+bool NativeObject::allocDictionarySlot(JSContext* cx, Handle<NativeObject*> obj,
+ uint32_t* slotp) {
+ MOZ_ASSERT(obj->inDictionaryMode());
+
+ uint32_t slotSpan = obj->slotSpan();
+ MOZ_ASSERT(slotSpan >= JSSLOT_FREE(obj->getClass()));
+
+ // Try to pull a free slot from the slot-number free list.
+ DictionaryPropMap* map = obj->dictionaryShape()->propMap();
+ uint32_t last = map->freeList();
+ if (last != SHAPE_INVALID_SLOT) {
+#ifdef DEBUG
+ MOZ_ASSERT(last < slotSpan);
+ uint32_t next = obj->getSlot(last).toPrivateUint32();
+ MOZ_ASSERT_IF(next != SHAPE_INVALID_SLOT, next < slotSpan);
+#endif
+ *slotp = last;
+ const Value& vref = obj->getSlot(last);
+ map->setFreeList(vref.toPrivateUint32());
+ obj->setSlot(last, UndefinedValue());
+ return true;
+ }
+
+ if (MOZ_UNLIKELY(slotSpan >= SHAPE_MAXIMUM_SLOT)) {
+ ReportOutOfMemory(cx);
+ return false;
+ }
+
+ *slotp = slotSpan;
+
+ uint32_t numFixed = obj->numFixedSlots();
+ if (slotSpan < numFixed) {
+ obj->initFixedSlot(slotSpan, UndefinedValue());
+ obj->setDictionaryModeSlotSpan(slotSpan + 1);
+ return true;
+ }
+
+ uint32_t dynamicSlotIndex = slotSpan - numFixed;
+ if (dynamicSlotIndex >= obj->numDynamicSlots()) {
+ if (MOZ_UNLIKELY(!obj->growSlotsForNewSlot(cx, numFixed, slotSpan))) {
+ return false;
+ }
+ }
+ obj->initDynamicSlot(numFixed, slotSpan, UndefinedValue());
+ obj->setDictionaryModeSlotSpan(slotSpan + 1);
+ return true;
+}
+
+void NativeObject::freeDictionarySlot(uint32_t slot) {
+ MOZ_ASSERT(inDictionaryMode());
+ MOZ_ASSERT(slot < slotSpan());
+
+ DictionaryPropMap* map = dictionaryShape()->propMap();
+ uint32_t last = map->freeList();
+
+ // Can't afford to check the whole free list, but let's check the head.
+ MOZ_ASSERT_IF(last != SHAPE_INVALID_SLOT, last < slotSpan() && last != slot);
+
+ // Place all freed slots other than reserved slots (bug 595230) on the
+ // dictionary's free list.
+ if (JSSLOT_FREE(getClass()) <= slot) {
+ MOZ_ASSERT_IF(last != SHAPE_INVALID_SLOT, last < slotSpan());
+ setSlot(slot, PrivateUint32Value(last));
+ map->setFreeList(slot);
+ } else {
+ setSlot(slot, UndefinedValue());
+ }
+}
+
+template <AllowGC allowGC>
+bool js::NativeLookupOwnProperty(
+ JSContext* cx, typename MaybeRooted<NativeObject*, allowGC>::HandleType obj,
+ typename MaybeRooted<jsid, allowGC>::HandleType id, PropertyResult* propp) {
+ return NativeLookupOwnPropertyInline<allowGC>(cx, obj, id, propp);
+}
+
+template bool js::NativeLookupOwnProperty<CanGC>(JSContext* cx,
+ Handle<NativeObject*> obj,
+ HandleId id,
+ PropertyResult* propp);
+
+template bool js::NativeLookupOwnProperty<NoGC>(JSContext* cx,
+ NativeObject* const& obj,
+ const jsid& id,
+ PropertyResult* propp);
+
+/*** [[DefineOwnProperty]] **************************************************/
+
+static bool CallJSAddPropertyOp(JSContext* cx, JSAddPropertyOp op,
+ HandleObject obj, HandleId id, HandleValue v) {
+ AutoCheckRecursionLimit recursion(cx);
+ if (!recursion.check(cx)) {
+ return false;
+ }
+
+ cx->check(obj, id, v);
+ return op(cx, obj, id, v);
+}
+
+static MOZ_ALWAYS_INLINE bool CallAddPropertyHook(JSContext* cx,
+ Handle<NativeObject*> obj,
+ HandleId id,
+ HandleValue value) {
+ JSAddPropertyOp addProperty = obj->getClass()->getAddProperty();
+ if (MOZ_UNLIKELY(addProperty)) {
+ if (!CallJSAddPropertyOp(cx, addProperty, obj, id, value)) {
+ NativeObject::removeProperty(cx, obj, id);
+ return false;
+ }
+ }
+ return true;
+}
+
+static MOZ_ALWAYS_INLINE bool CallAddPropertyHookDense(
+ JSContext* cx, Handle<NativeObject*> obj, uint32_t index,
+ HandleValue value) {
+ // Inline addProperty for array objects.
+ if (obj->is<ArrayObject>()) {
+ ArrayObject* arr = &obj->as<ArrayObject>();
+ uint32_t length = arr->length();
+ if (index >= length) {
+ arr->setLength(index + 1);
+ }
+ return true;
+ }
+
+ JSAddPropertyOp addProperty = obj->getClass()->getAddProperty();
+ if (MOZ_UNLIKELY(addProperty)) {
+ RootedId id(cx, PropertyKey::Int(index));
+ if (!CallJSAddPropertyOp(cx, addProperty, obj, id, value)) {
+ obj->setDenseElementHole(index);
+ return false;
+ }
+ }
+ return true;
+}
+
+/**
+ * Determines whether a write to the given element on |arr| should fail
+ * because |arr| has a non-writable length, and writing that element would
+ * increase the length of the array.
+ */
+static bool WouldDefinePastNonwritableLength(ArrayObject* arr, uint32_t index) {
+ return !arr->lengthIsWritable() && index >= arr->length();
+}
+
+static bool ChangeProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, HandleObject getter,
+ HandleObject setter, PropertyFlags flags,
+ PropertyResult* existing, uint32_t* slotOut) {
+ MOZ_ASSERT(existing);
+
+ Rooted<GetterSetter*> gs(cx);
+
+ // If we're redefining a getter/setter property but the getter and setter
+ // objects are still the same, use the existing GetterSetter.
+ if (existing->isNativeProperty()) {
+ PropertyInfo prop = existing->propertyInfo();
+ if (prop.isAccessorProperty()) {
+ GetterSetter* current = obj->getGetterSetter(prop);
+ if (current->getter() == getter && current->setter() == setter) {
+ gs = current;
+ }
+ }
+ }
+
+ if (!gs) {
+ gs = GetterSetter::create(cx, getter, setter);
+ if (!gs) {
+ return false;
+ }
+ }
+
+ if (existing->isNativeProperty()) {
+ if (!NativeObject::changeProperty(cx, obj, id, flags, slotOut)) {
+ return false;
+ }
+ } else {
+ if (!NativeObject::addProperty(cx, obj, id, flags, slotOut)) {
+ return false;
+ }
+ }
+
+ obj->setSlot(*slotOut, PrivateGCThingValue(gs));
+ return true;
+}
+
+static PropertyFlags ComputePropertyFlags(const PropertyDescriptor& desc) {
+ desc.assertComplete();
+
+ PropertyFlags flags;
+ flags.setFlag(PropertyFlag::Configurable, desc.configurable());
+ flags.setFlag(PropertyFlag::Enumerable, desc.enumerable());
+
+ if (desc.isDataDescriptor()) {
+ flags.setFlag(PropertyFlag::Writable, desc.writable());
+ } else {
+ MOZ_ASSERT(desc.isAccessorDescriptor());
+ flags.setFlag(PropertyFlag::AccessorProperty);
+ }
+
+ return flags;
+}
+
+// Whether we're adding a new property or changing an existing property (this
+// can be either a property stored in the shape tree or a dense element).
+enum class IsAddOrChange { Add, Change };
+
+template <IsAddOrChange AddOrChange>
+static MOZ_ALWAYS_INLINE bool AddOrChangeProperty(
+ JSContext* cx, Handle<NativeObject*> obj, HandleId id,
+ Handle<PropertyDescriptor> desc, PropertyResult* existing = nullptr) {
+ desc.assertComplete();
+
+#ifdef DEBUG
+ if constexpr (AddOrChange == IsAddOrChange::Add) {
+ MOZ_ASSERT(existing == nullptr);
+ MOZ_ASSERT(!obj->containsPure(id));
+ } else {
+ static_assert(AddOrChange == IsAddOrChange::Change);
+ MOZ_ASSERT(existing);
+ MOZ_ASSERT(existing->isNativeProperty() || existing->isDenseElement());
+ }
+#endif
+
+ // Use dense storage for indexed properties where possible: when we have an
+ // integer key with default property attributes and are either adding a new
+ // property or changing a dense element.
+ PropertyFlags flags = ComputePropertyFlags(desc);
+ if (id.isInt() && flags == PropertyFlags::defaultDataPropFlags &&
+ (AddOrChange == IsAddOrChange::Add || existing->isDenseElement())) {
+ MOZ_ASSERT(!desc.isAccessorDescriptor());
+ MOZ_ASSERT(!obj->is<TypedArrayObject>());
+ uint32_t index = id.toInt();
+ DenseElementResult edResult = obj->ensureDenseElements(cx, index, 1);
+ if (edResult == DenseElementResult::Failure) {
+ return false;
+ }
+ if (edResult == DenseElementResult::Success) {
+ obj->setDenseElement(index, desc.value());
+ if (!CallAddPropertyHookDense(cx, obj, index, desc.value())) {
+ return false;
+ }
+ return true;
+ }
+ }
+
+ uint32_t slot;
+ if constexpr (AddOrChange == IsAddOrChange::Add) {
+ if (desc.isAccessorDescriptor()) {
+ Rooted<GetterSetter*> gs(
+ cx, GetterSetter::create(cx, desc.getter(), desc.setter()));
+ if (!gs) {
+ return false;
+ }
+ if (!NativeObject::addProperty(cx, obj, id, flags, &slot)) {
+ return false;
+ }
+ obj->initSlot(slot, PrivateGCThingValue(gs));
+ } else {
+ if (!NativeObject::addProperty(cx, obj, id, flags, &slot)) {
+ return false;
+ }
+ obj->initSlot(slot, desc.value());
+ }
+ } else {
+ if (desc.isAccessorDescriptor()) {
+ if (!ChangeProperty(cx, obj, id, desc.getter(), desc.setter(), flags,
+ existing, &slot)) {
+ return false;
+ }
+ } else {
+ if (existing->isNativeProperty()) {
+ if (!NativeObject::changeProperty(cx, obj, id, flags, &slot)) {
+ return false;
+ }
+ } else {
+ if (!NativeObject::addProperty(cx, obj, id, flags, &slot)) {
+ return false;
+ }
+ }
+ obj->setSlot(slot, desc.value());
+ }
+ }
+
+ MOZ_ASSERT(slot < obj->slotSpan());
+
+ // Clear any existing dense index after adding a sparse indexed property,
+ // and investigate converting the object to dense indexes.
+ if (id.isInt()) {
+ uint32_t index = id.toInt();
+ if constexpr (AddOrChange == IsAddOrChange::Add) {
+ MOZ_ASSERT(!obj->containsDenseElement(index));
+ } else {
+ obj->removeDenseElementForSparseIndex(index);
+ }
+ // Only try to densify sparse elements if the property we just added/changed
+ // is in the last slot. This avoids a perf cliff in pathological cases: in
+ // maybeDensifySparseElements we densify if the slot span is a power-of-two,
+ // but if we get slots from the free list, the slot span will stay the same
+ // until the free list is empty. This means we'd get quadratic behavior by
+ // trying to densify for each sparse element we add. See bug 1782487.
+ if (slot == obj->slotSpan() - 1) {
+ DenseElementResult edResult =
+ NativeObject::maybeDensifySparseElements(cx, obj);
+ if (edResult == DenseElementResult::Failure) {
+ return false;
+ }
+ if (edResult == DenseElementResult::Success) {
+ MOZ_ASSERT(!desc.isAccessorDescriptor());
+ return CallAddPropertyHookDense(cx, obj, index, desc.value());
+ }
+ }
+ }
+
+ if (desc.isDataDescriptor()) {
+ return CallAddPropertyHook(cx, obj, id, desc.value());
+ }
+
+ return CallAddPropertyHook(cx, obj, id, UndefinedHandleValue);
+}
+
+// Versions of AddOrChangeProperty optimized for adding a plain data property.
+// This function doesn't handle integer ids as we may have to store them in
+// dense elements.
+static MOZ_ALWAYS_INLINE bool AddDataProperty(JSContext* cx,
+ Handle<NativeObject*> obj,
+ HandleId id, HandleValue v) {
+ MOZ_ASSERT(!id.isInt());
+
+ uint32_t slot;
+ if (!NativeObject::addProperty(cx, obj, id,
+ PropertyFlags::defaultDataPropFlags, &slot)) {
+ return false;
+ }
+
+ obj->initSlot(slot, v);
+
+ return CallAddPropertyHook(cx, obj, id, v);
+}
+
+bool js::AddSlotAndCallAddPropHook(JSContext* cx, Handle<NativeObject*> obj,
+ HandleValue v, Handle<Shape*> newShape) {
+ MOZ_ASSERT(obj->getClass()->getAddProperty());
+ MOZ_ASSERT(newShape->asShared().lastProperty().isDataProperty());
+
+ RootedId id(cx, newShape->asShared().lastProperty().key());
+ MOZ_ASSERT(!id.isInt());
+
+ uint32_t slot = newShape->asShared().lastProperty().slot();
+ if (!obj->setShapeAndAddNewSlot(cx, &newShape->asShared(), slot)) {
+ return false;
+ }
+ obj->initSlot(slot, v);
+
+ return CallAddPropertyHook(cx, obj, id, v);
+}
+
+static bool IsAccessorDescriptor(const PropertyResult& prop) {
+ if (prop.isNativeProperty()) {
+ return prop.propertyInfo().isAccessorProperty();
+ }
+
+ MOZ_ASSERT(prop.isDenseElement() || prop.isTypedArrayElement());
+ return false;
+}
+
+static bool IsDataDescriptor(const PropertyResult& prop) {
+ return !IsAccessorDescriptor(prop);
+}
+
+static bool GetCustomDataProperty(JSContext* cx, HandleObject obj, HandleId id,
+ MutableHandleValue vp);
+
+static bool GetExistingDataProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, const PropertyResult& prop,
+ MutableHandleValue vp) {
+ if (prop.isDenseElement()) {
+ vp.set(obj->getDenseElement(prop.denseElementIndex()));
+ return true;
+ }
+ if (prop.isTypedArrayElement()) {
+ size_t idx = prop.typedArrayElementIndex();
+ return obj->as<TypedArrayObject>().getElement<CanGC>(cx, idx, vp);
+ }
+
+ PropertyInfo propInfo = prop.propertyInfo();
+ if (propInfo.isDataProperty()) {
+ vp.set(obj->getSlot(propInfo.slot()));
+ return true;
+ }
+
+ MOZ_RELEASE_ASSERT(propInfo.isCustomDataProperty());
+ return GetCustomDataProperty(cx, obj, id, vp);
+}
+
+/*
+ * If desc is redundant with an existing own property obj[id], then set
+ * |*redundant = true| and return true.
+ */
+static bool DefinePropertyIsRedundant(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, const PropertyResult& prop,
+ JS::PropertyAttributes attrs,
+ Handle<PropertyDescriptor> desc,
+ bool* redundant) {
+ *redundant = false;
+
+ if (desc.hasConfigurable() && desc.configurable() != attrs.configurable()) {
+ return true;
+ }
+ if (desc.hasEnumerable() && desc.enumerable() != attrs.enumerable()) {
+ return true;
+ }
+ if (desc.isDataDescriptor()) {
+ if (IsAccessorDescriptor(prop)) {
+ return true;
+ }
+ if (desc.hasWritable() && desc.writable() != attrs.writable()) {
+ return true;
+ }
+ if (desc.hasValue()) {
+ // Get the current value of the existing property.
+ RootedValue currentValue(cx);
+ if (!GetExistingDataProperty(cx, obj, id, prop, &currentValue)) {
+ return false;
+ }
+
+ // Don't call SameValue here to ensure we properly update distinct
+ // NaN values.
+ if (desc.value() != currentValue) {
+ return true;
+ }
+ }
+
+ // Check for custom data properties for ArrayObject/ArgumentsObject.
+ // PropertyDescriptor can't represent these properties so they're never
+ // redundant.
+ if (prop.isNativeProperty() && prop.propertyInfo().isCustomDataProperty()) {
+ return true;
+ }
+ } else if (desc.isAccessorDescriptor()) {
+ if (!prop.isNativeProperty()) {
+ return true;
+ }
+ PropertyInfo propInfo = prop.propertyInfo();
+ if (desc.hasGetter() && (!propInfo.isAccessorProperty() ||
+ desc.getter() != obj->getGetter(propInfo))) {
+ return true;
+ }
+ if (desc.hasSetter() && (!propInfo.isAccessorProperty() ||
+ desc.setter() != obj->getSetter(propInfo))) {
+ return true;
+ }
+ }
+
+ *redundant = true;
+ return true;
+}
+
+bool js::NativeDefineProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, Handle<PropertyDescriptor> desc_,
+ ObjectOpResult& result) {
+ desc_.assertValid();
+
+ // Section numbers and step numbers below refer to ES2018, draft rev
+ // 540b827fccf6122a984be99ab9af7be20e3b5562.
+ //
+ // This function aims to implement 9.1.6 [[DefineOwnProperty]] as well as
+ // the [[DefineOwnProperty]] methods described in 9.4.2.1 (arrays), 9.4.4.2
+ // (arguments), and 9.4.5.3 (typed array views).
+
+ // Dispense with custom behavior of exotic native objects first.
+ if (obj->is<ArrayObject>()) {
+ // 9.4.2.1 step 2. Redefining an array's length is very special.
+ Rooted<ArrayObject*> arr(cx, &obj->as<ArrayObject>());
+ if (id == NameToId(cx->names().length)) {
+ // 9.1.6.3 ValidateAndApplyPropertyDescriptor, step 7.a.
+ if (desc_.isAccessorDescriptor()) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+
+ return ArraySetLength(cx, arr, id, desc_, result);
+ }
+
+ // 9.4.2.1 step 3. Don't extend a fixed-length array.
+ uint32_t index;
+ if (IdIsIndex(id, &index)) {
+ if (WouldDefinePastNonwritableLength(arr, index)) {
+ return result.fail(JSMSG_CANT_DEFINE_PAST_ARRAY_LENGTH);
+ }
+ }
+ } else if (obj->is<TypedArrayObject>()) {
+ // 9.4.5.3 step 3. Indexed properties of typed arrays are special.
+ if (mozilla::Maybe<uint64_t> index = ToTypedArrayIndex(id)) {
+ Rooted<TypedArrayObject*> tobj(cx, &obj->as<TypedArrayObject>());
+ return DefineTypedArrayElement(cx, tobj, index.value(), desc_, result);
+ }
+ } else if (obj->is<ArgumentsObject>()) {
+ Rooted<ArgumentsObject*> argsobj(cx, &obj->as<ArgumentsObject>());
+ if (id.isAtom(cx->names().length)) {
+ // Either we are resolving the .length property on this object,
+ // or redefining it. In the latter case only, we must reify the
+ // property.
+ if (!desc_.resolving()) {
+ if (!ArgumentsObject::reifyLength(cx, argsobj)) {
+ return false;
+ }
+ }
+ } else if (id.isAtom(cx->names().callee) &&
+ argsobj->is<MappedArgumentsObject>()) {
+ // Do same thing as .length for .callee on MappedArgumentsObject.
+ if (!desc_.resolving()) {
+ Rooted<MappedArgumentsObject*> mapped(
+ cx, &argsobj->as<MappedArgumentsObject>());
+ if (!MappedArgumentsObject::reifyCallee(cx, mapped)) {
+ return false;
+ }
+ }
+ } else if (id.isWellKnownSymbol(JS::SymbolCode::iterator)) {
+ // Do same thing as .length for [@@iterator].
+ if (!desc_.resolving()) {
+ if (!ArgumentsObject::reifyIterator(cx, argsobj)) {
+ return false;
+ }
+ }
+ } else if (id.isInt()) {
+ if (!desc_.resolving()) {
+ argsobj->markElementOverridden();
+ }
+ }
+ }
+
+ // 9.1.6.1 OrdinaryDefineOwnProperty step 1.
+ PropertyResult prop;
+ if (desc_.resolving()) {
+ // We are being called from a resolve or enumerate hook to reify a
+ // lazily-resolved property. To avoid reentering the resolve hook and
+ // recursing forever, skip the resolve hook when doing this lookup.
+ if (!NativeLookupOwnPropertyNoResolve(cx, obj, id, &prop)) {
+ return false;
+ }
+ } else {
+ if (!NativeLookupOwnProperty<CanGC>(cx, obj, id, &prop)) {
+ return false;
+ }
+ }
+
+ // From this point, the step numbers refer to
+ // 9.1.6.3, ValidateAndApplyPropertyDescriptor.
+ // Step 1 is a redundant assertion.
+
+ // Filling in desc: Here we make a copy of the desc_ argument. We will turn
+ // it into a complete descriptor before updating obj. The spec algorithm
+ // does not explicitly do this, but the end result is the same. Search for
+ // "fill in" below for places where the filling-in actually occurs.
+ Rooted<PropertyDescriptor> desc(cx, desc_);
+
+ // Step 2.
+ if (prop.isNotFound()) {
+ // Note: We are sharing the property definition machinery with private
+ // fields. Private fields may be added to non-extensible objects.
+ if (!obj->isExtensible() && !id.isPrivateName() &&
+ // R&T wrappers are non-extensible, but we still want to be able to
+ // lazily resolve their properties. We can special-case them to
+ // allow doing so.
+ IF_RECORD_TUPLE(
+ !(IsExtendedPrimitiveWrapper(*obj) && desc_.resolving()), true)) {
+ return result.fail(JSMSG_CANT_DEFINE_PROP_OBJECT_NOT_EXTENSIBLE);
+ }
+
+ // Fill in missing desc fields with defaults.
+ CompletePropertyDescriptor(&desc);
+
+ if (!AddOrChangeProperty<IsAddOrChange::Add>(cx, obj, id, desc)) {
+ return false;
+ }
+ return result.succeed();
+ }
+
+ // Step 3 and 7.a.i.3, 8.a.iii, 10 (partially). Prop might not actually
+ // have a real shape, e.g. in the case of typed array elements,
+ // GetPropertyAttributes is used to paper-over that difference.
+ JS::PropertyAttributes attrs = GetPropertyAttributes(obj, prop);
+ bool redundant;
+ if (!DefinePropertyIsRedundant(cx, obj, id, prop, attrs, desc, &redundant)) {
+ return false;
+ }
+ if (redundant) {
+ return result.succeed();
+ }
+
+ // Step 4.
+ if (!attrs.configurable()) {
+ if (desc.hasConfigurable() && desc.configurable()) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+ if (desc.hasEnumerable() && desc.enumerable() != attrs.enumerable()) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+ }
+
+ // Fill in desc.[[Configurable]] and desc.[[Enumerable]] if missing.
+ if (!desc.hasConfigurable()) {
+ desc.setConfigurable(attrs.configurable());
+ }
+ if (!desc.hasEnumerable()) {
+ desc.setEnumerable(attrs.enumerable());
+ }
+
+ // Steps 5-8.
+ if (desc.isGenericDescriptor()) {
+ // Step 5. No further validation is required.
+
+ // Fill in desc. A generic descriptor has none of these fields, so copy
+ // everything from shape.
+ MOZ_ASSERT(!desc.hasValue());
+ MOZ_ASSERT(!desc.hasWritable());
+ MOZ_ASSERT(!desc.hasGetter());
+ MOZ_ASSERT(!desc.hasSetter());
+ if (IsDataDescriptor(prop)) {
+ RootedValue currentValue(cx);
+ if (!GetExistingDataProperty(cx, obj, id, prop, &currentValue)) {
+ return false;
+ }
+ desc.setValue(currentValue);
+ desc.setWritable(attrs.writable());
+ } else {
+ PropertyInfo propInfo = prop.propertyInfo();
+ desc.setGetter(obj->getGetter(propInfo));
+ desc.setSetter(obj->getSetter(propInfo));
+ }
+ } else if (desc.isDataDescriptor() != IsDataDescriptor(prop)) {
+ // Step 6.
+ if (!attrs.configurable()) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+
+ // Fill in desc fields with default values (steps 6.b.i and 6.c.i).
+ CompletePropertyDescriptor(&desc);
+ } else if (desc.isDataDescriptor()) {
+ // Step 7.
+ bool frozen = !attrs.configurable() && !attrs.writable();
+
+ // Step 7.a.i.1.
+ if (frozen && desc.hasWritable() && desc.writable()) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+
+ if (frozen || !desc.hasValue()) {
+ RootedValue currentValue(cx);
+ if (!GetExistingDataProperty(cx, obj, id, prop, &currentValue)) {
+ return false;
+ }
+
+ if (!desc.hasValue()) {
+ // Fill in desc.[[Value]].
+ desc.setValue(currentValue);
+ } else {
+ // Step 7.a.i.2.
+ bool same;
+ if (!SameValue(cx, desc.value(), currentValue, &same)) {
+ return false;
+ }
+ if (!same) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+ }
+ }
+
+ // Step 7.a.i.3.
+ if (frozen) {
+ return result.succeed();
+ }
+
+ // Fill in desc.[[Writable]].
+ if (!desc.hasWritable()) {
+ desc.setWritable(attrs.writable());
+ }
+ } else {
+ // Step 8.
+ PropertyInfo propInfo = prop.propertyInfo();
+ MOZ_ASSERT(propInfo.isAccessorProperty());
+ MOZ_ASSERT(desc.isAccessorDescriptor());
+
+ // The spec says to use SameValue, but since the values in
+ // question are objects, we can just compare pointers.
+ if (desc.hasSetter()) {
+ // Step 8.a.i.
+ if (!attrs.configurable() && desc.setter() != obj->getSetter(propInfo)) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+ } else {
+ // Fill in desc.[[Set]] from shape.
+ desc.setSetter(obj->getSetter(propInfo));
+ }
+ if (desc.hasGetter()) {
+ // Step 8.a.ii.
+ if (!attrs.configurable() && desc.getter() != obj->getGetter(propInfo)) {
+ return result.fail(JSMSG_CANT_REDEFINE_PROP);
+ }
+ } else {
+ // Fill in desc.[[Get]] from shape.
+ desc.setGetter(obj->getGetter(propInfo));
+ }
+
+ // Step 8.a.iii (Omitted).
+ }
+
+ // Step 9.
+ if (!AddOrChangeProperty<IsAddOrChange::Change>(cx, obj, id, desc, &prop)) {
+ return false;
+ }
+
+ // Step 10.
+ return result.succeed();
+}
+
+bool js::NativeDefineDataProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, HandleValue value,
+ unsigned attrs, ObjectOpResult& result) {
+ Rooted<PropertyDescriptor> desc(cx, PropertyDescriptor::Data(value, attrs));
+ return NativeDefineProperty(cx, obj, id, desc, result);
+}
+
+bool js::NativeDefineAccessorProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, HandleObject getter,
+ HandleObject setter, unsigned attrs) {
+ Rooted<PropertyDescriptor> desc(
+ cx, PropertyDescriptor::Accessor(
+ getter ? mozilla::Some(getter) : mozilla::Nothing(),
+ setter ? mozilla::Some(setter) : mozilla::Nothing(), attrs));
+
+ ObjectOpResult result;
+ if (!NativeDefineProperty(cx, obj, id, desc, result)) {
+ return false;
+ }
+
+ if (!result) {
+ // Off-thread callers should not get here: they must call this
+ // function only with known-valid arguments. Populating a new
+ // PlainObject with configurable properties is fine.
+ result.reportError(cx, obj, id);
+ return false;
+ }
+
+ return true;
+}
+
+bool js::NativeDefineDataProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, HandleValue value,
+ unsigned attrs) {
+ ObjectOpResult result;
+ if (!NativeDefineDataProperty(cx, obj, id, value, attrs, result)) {
+ return false;
+ }
+ if (!result) {
+ // Off-thread callers should not get here: they must call this
+ // function only with known-valid arguments. Populating a new
+ // PlainObject with configurable properties is fine.
+ result.reportError(cx, obj, id);
+ return false;
+ }
+ return true;
+}
+
+bool js::NativeDefineDataProperty(JSContext* cx, Handle<NativeObject*> obj,
+ PropertyName* name, HandleValue value,
+ unsigned attrs) {
+ RootedId id(cx, NameToId(name));
+ return NativeDefineDataProperty(cx, obj, id, value, attrs);
+}
+
+static bool DefineNonexistentProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, HandleValue v,
+ ObjectOpResult& result) {
+ // Optimized NativeDefineProperty() version for known absent properties.
+
+ // Dispense with custom behavior of exotic native objects first.
+ if (obj->is<ArrayObject>()) {
+ // Array's length property is non-configurable, so we shouldn't
+ // encounter it in this function.
+ MOZ_ASSERT(id != NameToId(cx->names().length));
+
+ // 9.4.2.1 step 3. Don't extend a fixed-length array.
+ uint32_t index;
+ if (IdIsIndex(id, &index)) {
+ if (WouldDefinePastNonwritableLength(&obj->as<ArrayObject>(), index)) {
+ return result.fail(JSMSG_CANT_DEFINE_PAST_ARRAY_LENGTH);
+ }
+ }
+ } else if (obj->is<TypedArrayObject>()) {
+ // TypedArray Exotic Objects, 10.4.5.5 step 1.
+ //
+ // Indexed properties of typed arrays are special.
+ if (mozilla::Maybe<uint64_t> index = ToTypedArrayIndex(id)) {
+ Rooted<TypedArrayObject*> tobj(cx, &obj->as<TypedArrayObject>());
+ return SetTypedArrayElementOutOfBounds(cx, tobj, *index, v, result);
+ }
+ } else if (obj->is<ArgumentsObject>()) {
+ // If this method is called with either |length| or |@@iterator|, the
+ // property was previously deleted and hence should already be marked
+ // as overridden.
+ MOZ_ASSERT_IF(id.isAtom(cx->names().length),
+ obj->as<ArgumentsObject>().hasOverriddenLength());
+ MOZ_ASSERT_IF(id.isWellKnownSymbol(JS::SymbolCode::iterator),
+ obj->as<ArgumentsObject>().hasOverriddenIterator());
+
+ // We still need to mark any element properties as overridden.
+ if (id.isInt()) {
+ obj->as<ArgumentsObject>().markElementOverridden();
+ }
+ }
+
+#ifdef DEBUG
+ PropertyResult prop;
+ if (!NativeLookupOwnPropertyNoResolve(cx, obj, id, &prop)) {
+ return false;
+ }
+ MOZ_ASSERT(prop.isNotFound(), "didn't expect to find an existing property");
+#endif
+
+ // 9.1.6.3, ValidateAndApplyPropertyDescriptor.
+ // Step 1 is a redundant assertion, step 3 and later don't apply here.
+
+ // Step 2.
+ if (!obj->isExtensible()) {
+ return result.fail(JSMSG_CANT_DEFINE_PROP_OBJECT_NOT_EXTENSIBLE);
+ }
+
+ if (id.isInt()) {
+ // This might be a dense element. Use AddOrChangeProperty as it knows
+ // how to deal with that.
+ Rooted<PropertyDescriptor> desc(
+ cx, PropertyDescriptor::Data(v, {JS::PropertyAttribute::Configurable,
+ JS::PropertyAttribute::Enumerable,
+ JS::PropertyAttribute::Writable}));
+ if (!AddOrChangeProperty<IsAddOrChange::Add>(cx, obj, id, desc)) {
+ return false;
+ }
+ } else {
+ if (!AddDataProperty(cx, obj, id, v)) {
+ return false;
+ }
+ }
+
+ return result.succeed();
+}
+
+bool js::AddOrUpdateSparseElementHelper(JSContext* cx,
+ Handle<NativeObject*> obj,
+ int32_t int_id, HandleValue v,
+ bool strict) {
+ MOZ_ASSERT(obj->is<ArrayObject>() || obj->is<PlainObject>());
+
+ // This helper doesn't handle the case where the index is a dense element.
+ MOZ_ASSERT(int_id >= 0);
+ MOZ_ASSERT(!obj->containsDenseElement(int_id));
+
+ MOZ_ASSERT(PropertyKey::fitsInInt(int_id));
+ RootedId id(cx, PropertyKey::Int(int_id));
+
+ // First decide if this is an add or an update. Because the IC guards have
+ // already ensured this exists exterior to the dense array range, and the
+ // prototype checks have ensured there are no indexes on the prototype, we
+ // can use the shape lineage to find the element if it exists:
+ uint32_t index;
+ PropMap* map = obj->shape()->lookup(cx, id, &index);
+
+ // If we didn't find the property, we're on the add path: delegate to
+ // AddOrChangeProperty. This will add either a sparse element or a dense
+ // element.
+ if (map == nullptr) {
+ Rooted<PropertyDescriptor> desc(
+ cx, PropertyDescriptor::Data(v, {JS::PropertyAttribute::Configurable,
+ JS::PropertyAttribute::Enumerable,
+ JS::PropertyAttribute::Writable}));
+ return AddOrChangeProperty<IsAddOrChange::Add>(cx, obj, id, desc);
+ }
+
+ // At this point we're updating a property: See SetExistingProperty.
+ PropertyInfo prop = map->getPropertyInfo(index);
+ if (prop.isDataProperty() && prop.writable()) {
+ obj->setSlot(prop.slot(), v);
+ return true;
+ }
+
+ // We don't know exactly what this object looks like, hit the slowpath.
+ RootedValue receiver(cx, ObjectValue(*obj));
+ JS::ObjectOpResult result;
+ return SetProperty(cx, obj, id, v, receiver, result) &&
+ result.checkStrictModeError(cx, obj, id, strict);
+}
+
+/*** [[HasProperty]] ********************************************************/
+
+// ES6 draft rev31 9.1.7.1 OrdinaryHasProperty
+bool js::NativeHasProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, bool* foundp) {
+ Rooted<NativeObject*> pobj(cx, obj);
+ PropertyResult prop;
+
+ // This loop isn't explicit in the spec algorithm. See the comment on step
+ // 7.a. below.
+ for (;;) {
+ // Steps 2-3.
+ if (!NativeLookupOwnPropertyInline<CanGC>(cx, pobj, id, &prop)) {
+ return false;
+ }
+
+ // Step 4.
+ if (prop.isFound()) {
+ *foundp = true;
+ return true;
+ }
+
+ // Step 5-6.
+ JSObject* proto = pobj->staticPrototype();
+
+ // Step 8.
+ // As a side-effect of NativeLookupOwnPropertyInline, we may determine that
+ // a property is not found and the proto chain should not be searched. This
+ // can occur for:
+ // - Out-of-range numeric properties of a TypedArrayObject
+ // - Recursive resolve hooks (which is expected when they try to set the
+ // property being resolved).
+ if (!proto || prop.shouldIgnoreProtoChain()) {
+ *foundp = false;
+ return true;
+ }
+
+ // Step 7.a. If the prototype is also native, this step is a
+ // recursive tail call, and we don't need to go through all the
+ // plumbing of HasProperty; the top of the loop is where
+ // we're going to end up anyway. But if pobj is non-native,
+ // that optimization would be incorrect.
+ if (!proto->is<NativeObject>()) {
+ RootedObject protoRoot(cx, proto);
+ return HasProperty(cx, protoRoot, id, foundp);
+ }
+
+ pobj = &proto->as<NativeObject>();
+ }
+}
+
+/*** [[GetOwnPropertyDescriptor]] *******************************************/
+
+bool js::NativeGetOwnPropertyDescriptor(
+ JSContext* cx, Handle<NativeObject*> obj, HandleId id,
+ MutableHandle<mozilla::Maybe<PropertyDescriptor>> desc) {
+ PropertyResult prop;
+ if (!NativeLookupOwnProperty<CanGC>(cx, obj, id, &prop)) {
+ return false;
+ }
+ if (prop.isNotFound()) {
+ desc.reset();
+ return true;
+ }
+
+ if (prop.isNativeProperty() && prop.propertyInfo().isAccessorProperty()) {
+ PropertyInfo propInfo = prop.propertyInfo();
+ desc.set(mozilla::Some(PropertyDescriptor::Accessor(
+ obj->getGetter(propInfo), obj->getSetter(propInfo),
+ propInfo.propAttributes())));
+ return true;
+ }
+
+ RootedValue value(cx);
+ if (!GetExistingDataProperty(cx, obj, id, prop, &value)) {
+ return false;
+ }
+
+ JS::PropertyAttributes attrs = GetPropertyAttributes(obj, prop);
+ desc.set(mozilla::Some(PropertyDescriptor::Data(value, attrs)));
+ return true;
+}
+
+/*** [[Get]] ****************************************************************/
+
+static bool GetCustomDataProperty(JSContext* cx, HandleObject obj, HandleId id,
+ MutableHandleValue vp) {
+ cx->check(obj, id, vp);
+
+ const JSClass* clasp = obj->getClass();
+ if (clasp == &ArrayObject::class_) {
+ if (!ArrayLengthGetter(cx, obj, id, vp)) {
+ return false;
+ }
+ } else if (clasp == &MappedArgumentsObject::class_) {
+ if (!MappedArgGetter(cx, obj, id, vp)) {
+ return false;
+ }
+ } else {
+ MOZ_RELEASE_ASSERT(clasp == &UnmappedArgumentsObject::class_);
+ if (!UnmappedArgGetter(cx, obj, id, vp)) {
+ return false;
+ }
+ }
+
+ cx->check(vp);
+ return true;
+}
+
+static inline bool CallGetter(JSContext* cx, Handle<NativeObject*> obj,
+ HandleValue receiver, HandleId id,
+ PropertyInfo prop, MutableHandleValue vp) {
+ MOZ_ASSERT(!prop.isDataProperty());
+
+ if (prop.isAccessorProperty()) {
+ RootedValue getter(cx, obj->getGetterValue(prop));
+ return js::CallGetter(cx, receiver, getter, vp);
+ }
+
+ MOZ_ASSERT(prop.isCustomDataProperty());
+
+ return GetCustomDataProperty(cx, obj, id, vp);
+}
+
+template <AllowGC allowGC>
+static MOZ_ALWAYS_INLINE bool GetExistingProperty(
+ JSContext* cx, typename MaybeRooted<Value, allowGC>::HandleType receiver,
+ typename MaybeRooted<NativeObject*, allowGC>::HandleType obj,
+ typename MaybeRooted<jsid, allowGC>::HandleType id, PropertyInfo prop,
+ typename MaybeRooted<Value, allowGC>::MutableHandleType vp) {
+ if (prop.isDataProperty()) {
+ vp.set(obj->getSlot(prop.slot()));
+ return true;
+ }
+
+ vp.setUndefined();
+
+ if (!prop.isCustomDataProperty() && !obj->hasGetter(prop)) {
+ return true;
+ }
+
+ if constexpr (!allowGC) {
+ return false;
+ } else {
+ return CallGetter(cx, obj, receiver, id, prop, vp);
+ }
+}
+
+bool js::NativeGetExistingProperty(JSContext* cx, HandleObject receiver,
+ Handle<NativeObject*> obj, HandleId id,
+ PropertyInfo prop, MutableHandleValue vp) {
+ RootedValue receiverValue(cx, ObjectValue(*receiver));
+ return GetExistingProperty<CanGC>(cx, receiverValue, obj, id, prop, vp);
+}
+
+enum IsNameLookup { NotNameLookup = false, NameLookup = true };
+
+/*
+ * Finish getting the property `receiver[id]` after looking at every object on
+ * the prototype chain and not finding any such property.
+ *
+ * Per the spec, this should just set the result to `undefined` and call it a
+ * day. However this function also runs when we're evaluating an
+ * expression that's an Identifier (that is, an unqualified name lookup),
+ * so we need to figure out if that's what's happening and throw
+ * a ReferenceError if so.
+ */
+static bool GetNonexistentProperty(JSContext* cx, HandleId id,
+ IsNameLookup nameLookup,
+ MutableHandleValue vp) {
+ vp.setUndefined();
+
+ // If we are doing a name lookup, this is a ReferenceError.
+ if (nameLookup) {
+ ReportIsNotDefined(cx, id);
+ return false;
+ }
+
+ // Otherwise, just return |undefined|.
+ return true;
+}
+
+// The NoGC version of GetNonexistentProperty, present only to make types line
+// up.
+bool GetNonexistentProperty(JSContext* cx, const jsid& id,
+ IsNameLookup nameLookup,
+ FakeMutableHandle<Value> vp) {
+ return false;
+}
+
+static inline bool GeneralizedGetProperty(JSContext* cx, HandleObject obj,
+ HandleId id, HandleValue receiver,
+ IsNameLookup nameLookup,
+ MutableHandleValue vp) {
+ AutoCheckRecursionLimit recursion(cx);
+ if (!recursion.check(cx)) {
+ return false;
+ }
+ if (nameLookup) {
+ // When nameLookup is true, GetProperty implements ES6 rev 34 (2015 Feb
+ // 20) 8.1.1.2.6 GetBindingValue, with step 3 (the call to HasProperty)
+ // and step 6 (the call to Get) fused so that only a single lookup is
+ // needed.
+ //
+ // If we get here, we've reached a non-native object. Fall back on the
+ // algorithm as specified, with two separate lookups. (Note that we
+ // throw ReferenceErrors regardless of strictness, technically a bug.)
+
+ bool found;
+ if (!HasProperty(cx, obj, id, &found)) {
+ return false;
+ }
+ if (!found) {
+ ReportIsNotDefined(cx, id);
+ return false;
+ }
+ }
+
+ return GetProperty(cx, obj, receiver, id, vp);
+}
+
+static inline bool GeneralizedGetProperty(JSContext* cx, JSObject* obj, jsid id,
+ const Value& receiver,
+ IsNameLookup nameLookup,
+ FakeMutableHandle<Value> vp) {
+ AutoCheckRecursionLimit recursion(cx);
+ if (!recursion.checkDontReport(cx)) {
+ return false;
+ }
+ if (nameLookup) {
+ return false;
+ }
+ return GetPropertyNoGC(cx, obj, receiver, id, vp.address());
+}
+
+bool js::GetSparseElementHelper(JSContext* cx, Handle<NativeObject*> obj,
+ int32_t int_id, MutableHandleValue result) {
+ MOZ_ASSERT(obj->is<ArrayObject>() || obj->is<PlainObject>());
+
+ // This helper doesn't handle the case where the index is a dense element.
+ MOZ_ASSERT(int_id >= 0);
+ MOZ_ASSERT(!obj->containsDenseElement(int_id));
+
+ // Indexed properties can not exist on the prototype chain.
+ MOZ_ASSERT(!PrototypeMayHaveIndexedProperties(obj));
+
+ MOZ_ASSERT(PropertyKey::fitsInInt(int_id));
+ RootedId id(cx, PropertyKey::Int(int_id));
+
+ uint32_t index;
+ PropMap* map = obj->shape()->lookup(cx, id, &index);
+ if (!map) {
+ // Property not found, return directly.
+ result.setUndefined();
+ return true;
+ }
+
+ PropertyInfo prop = map->getPropertyInfo(index);
+ RootedValue receiver(cx, ObjectValue(*obj));
+ return GetExistingProperty<CanGC>(cx, receiver, obj, id, prop, result);
+}
+
+template <AllowGC allowGC>
+static MOZ_ALWAYS_INLINE bool NativeGetPropertyInline(
+ JSContext* cx, typename MaybeRooted<NativeObject*, allowGC>::HandleType obj,
+ typename MaybeRooted<Value, allowGC>::HandleType receiver,
+ typename MaybeRooted<jsid, allowGC>::HandleType id, IsNameLookup nameLookup,
+ typename MaybeRooted<Value, allowGC>::MutableHandleType vp) {
+ typename MaybeRooted<NativeObject*, allowGC>::RootType pobj(cx, obj);
+ PropertyResult prop;
+
+ // This loop isn't explicit in the spec algorithm. See the comment on step
+ // 4.d below.
+ for (;;) {
+ // Steps 2-3.
+ if (!NativeLookupOwnPropertyInline<allowGC>(cx, pobj, id, &prop)) {
+ return false;
+ }
+
+ if (prop.isFound()) {
+ // Steps 5-8. Special case for dense elements because
+ // GetExistingProperty doesn't support those.
+ if (prop.isDenseElement()) {
+ vp.set(pobj->getDenseElement(prop.denseElementIndex()));
+ return true;
+ }
+ if (prop.isTypedArrayElement()) {
+ size_t idx = prop.typedArrayElementIndex();
+ auto* tarr = &pobj->template as<TypedArrayObject>();
+ return tarr->template getElement<allowGC>(cx, idx, vp);
+ }
+
+ return GetExistingProperty<allowGC>(cx, receiver, pobj, id,
+ prop.propertyInfo(), vp);
+ }
+
+ // Steps 4.a-b.
+ JSObject* proto = pobj->staticPrototype();
+
+ // Step 4.c. The spec algorithm simply returns undefined if proto is
+ // null, but see the comment on GetNonexistentProperty.
+ if (!proto || prop.shouldIgnoreProtoChain()) {
+ return GetNonexistentProperty(cx, id, nameLookup, vp);
+ }
+
+ // Step 4.d. If the prototype is also native, this step is a
+ // recursive tail call, and we don't need to go through all the
+ // plumbing of JSObject::getGeneric; the top of the loop is where
+ // we're going to end up anyway. But if pobj is non-native,
+ // that optimization would be incorrect.
+ if (proto->getOpsGetProperty()) {
+ RootedObject protoRoot(cx, proto);
+ return GeneralizedGetProperty(cx, protoRoot, id, receiver, nameLookup,
+ vp);
+ }
+
+ pobj = &proto->as<NativeObject>();
+ }
+}
+
+bool js::NativeGetProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleValue receiver, HandleId id,
+ MutableHandleValue vp) {
+ return NativeGetPropertyInline<CanGC>(cx, obj, receiver, id, NotNameLookup,
+ vp);
+}
+
+bool js::NativeGetPropertyNoGC(JSContext* cx, NativeObject* obj,
+ const Value& receiver, jsid id, Value* vp) {
+ AutoAssertNoPendingException noexc(cx);
+ return NativeGetPropertyInline<NoGC>(cx, obj, receiver, id, NotNameLookup,
+ vp);
+}
+
+bool js::NativeGetElement(JSContext* cx, Handle<NativeObject*> obj,
+ HandleValue receiver, int32_t index,
+ MutableHandleValue vp) {
+ RootedId id(cx);
+
+ if (MOZ_LIKELY(index >= 0)) {
+ if (!IndexToId(cx, index, &id)) {
+ return false;
+ }
+ } else {
+ RootedValue indexVal(cx, Int32Value(index));
+ if (!PrimitiveValueToId<CanGC>(cx, indexVal, &id)) {
+ return false;
+ }
+ }
+ return NativeGetProperty(cx, obj, receiver, id, vp);
+}
+
+bool js::GetNameBoundInEnvironment(JSContext* cx, HandleObject envArg,
+ HandleId id, MutableHandleValue vp) {
+ // Manually unwrap 'with' environments to prevent looking up @@unscopables
+ // twice.
+ //
+ // This is unfortunate because internally, the engine does not distinguish
+ // HasProperty from HasBinding: both are implemented as a HasPropertyOp
+ // hook on a WithEnvironmentObject.
+ //
+ // In the case of attempting to get the value of a binding already looked up
+ // via JSOp::BindName, calling HasProperty on the WithEnvironmentObject is
+ // equivalent to calling HasBinding a second time. This results in the
+ // incorrect behavior of performing the @@unscopables check again.
+ RootedObject env(cx, MaybeUnwrapWithEnvironment(envArg));
+ RootedValue receiver(cx, ObjectValue(*env));
+ if (env->getOpsGetProperty()) {
+ return GeneralizedGetProperty(cx, env, id, receiver, NameLookup, vp);
+ }
+ return NativeGetPropertyInline<CanGC>(cx, env.as<NativeObject>(), receiver,
+ id, NameLookup, vp);
+}
+
+/*** [[Set]] ****************************************************************/
+
+static bool SetCustomDataProperty(JSContext* cx, HandleObject obj, HandleId id,
+ HandleValue v, ObjectOpResult& result) {
+ cx->check(obj, id, v);
+
+ const JSClass* clasp = obj->getClass();
+ if (clasp == &ArrayObject::class_) {
+ return ArrayLengthSetter(cx, obj, id, v, result);
+ }
+ if (clasp == &MappedArgumentsObject::class_) {
+ return MappedArgSetter(cx, obj, id, v, result);
+ }
+ MOZ_RELEASE_ASSERT(clasp == &UnmappedArgumentsObject::class_);
+ return UnmappedArgSetter(cx, obj, id, v, result);
+}
+
+static bool MaybeReportUndeclaredVarAssignment(JSContext* cx, HandleId id) {
+ {
+ jsbytecode* pc;
+ JSScript* script =
+ cx->currentScript(&pc, JSContext::AllowCrossRealm::Allow);
+ if (!script) {
+ return true;
+ }
+
+ if (!IsStrictSetPC(pc)) {
+ return true;
+ }
+ }
+
+ UniqueChars bytes =
+ IdToPrintableUTF8(cx, id, IdToPrintableBehavior::IdIsIdentifier);
+ if (!bytes) {
+ return false;
+ }
+ JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr, JSMSG_UNDECLARED_VAR,
+ bytes.get());
+ return false;
+}
+
+/*
+ * Finish assignment to a shapeful data property of a native object obj. This
+ * conforms to no standard and there is a lot of legacy baggage here.
+ */
+static bool NativeSetExistingDataProperty(JSContext* cx,
+ Handle<NativeObject*> obj,
+ HandleId id, PropertyInfo prop,
+ HandleValue v,
+ ObjectOpResult& result) {
+ MOZ_ASSERT(obj->is<NativeObject>());
+ MOZ_ASSERT(prop.isDataDescriptor());
+
+ if (!Watchtower::watchPropertyModification<AllowGC::CanGC>(cx, obj, id)) {
+ return false;
+ }
+
+ if (prop.isDataProperty()) {
+ // The common path. Standard data property.
+ obj->setSlot(prop.slot(), v);
+ return result.succeed();
+ }
+
+ MOZ_ASSERT(prop.isCustomDataProperty());
+ MOZ_ASSERT(!obj->is<WithEnvironmentObject>()); // See bug 1128681.
+
+ return SetCustomDataProperty(cx, obj, id, v, result);
+}
+
+/*
+ * When a [[Set]] operation finds no existing property with the given id
+ * or finds a writable data property on the prototype chain, we end up here.
+ * Finish the [[Set]] by defining a new property on receiver.
+ *
+ * This implements ES6 draft rev 28, 9.1.9 [[Set]] steps 5.b-f, but it
+ * is really old code and there are a few barnacles.
+ */
+bool js::SetPropertyByDefining(JSContext* cx, HandleId id, HandleValue v,
+ HandleValue receiverValue,
+ ObjectOpResult& result) {
+ // Step 5.b.
+ if (!receiverValue.isObject()) {
+ return result.fail(JSMSG_SET_NON_OBJECT_RECEIVER);
+ }
+ RootedObject receiver(cx, &receiverValue.toObject());
+
+ bool existing;
+ {
+ // Steps 5.c-d.
+ Rooted<mozilla::Maybe<PropertyDescriptor>> desc(cx);
+ if (!GetOwnPropertyDescriptor(cx, receiver, id, &desc)) {
+ return false;
+ }
+
+ existing = desc.isSome();
+
+ // Step 5.e.
+ if (existing) {
+ // Step 5.e.i.
+ if (desc->isAccessorDescriptor()) {
+ return result.fail(JSMSG_OVERWRITING_ACCESSOR);
+ }
+
+ // Step 5.e.ii.
+ if (!desc->writable()) {
+ return result.fail(JSMSG_READ_ONLY);
+ }
+ }
+ }
+
+ // Steps 5.e.iii-iv. and 5.f.i. Define the new data property.
+ Rooted<PropertyDescriptor> desc(cx);
+ if (existing) {
+ desc = PropertyDescriptor::Empty();
+ desc.setValue(v);
+ } else {
+ desc = PropertyDescriptor::Data(v, {JS::PropertyAttribute::Configurable,
+ JS::PropertyAttribute::Enumerable,
+ JS::PropertyAttribute::Writable});
+ }
+ return DefineProperty(cx, receiver, id, desc, result);
+}
+
+// When setting |id| for |receiver| and |obj| has no property for id, continue
+// the search up the prototype chain.
+bool js::SetPropertyOnProto(JSContext* cx, HandleObject obj, HandleId id,
+ HandleValue v, HandleValue receiver,
+ ObjectOpResult& result) {
+ MOZ_ASSERT(!obj->is<ProxyObject>());
+
+ RootedObject proto(cx, obj->staticPrototype());
+ if (proto) {
+ return SetProperty(cx, proto, id, v, receiver, result);
+ }
+
+ return SetPropertyByDefining(cx, id, v, receiver, result);
+}
+
+/*
+ * Implement "the rest of" assignment to a property when no property
+ * receiver[id] was found anywhere on the prototype chain.
+ *
+ * FIXME: This should be updated to follow ES6 draft rev 28, section 9.1.9,
+ * steps 4.d.i and 5.
+ */
+template <QualifiedBool IsQualified>
+static bool SetNonexistentProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, HandleValue v,
+ HandleValue receiver,
+ ObjectOpResult& result) {
+ if (!IsQualified && receiver.isObject() &&
+ receiver.toObject().isUnqualifiedVarObj()) {
+ if (!MaybeReportUndeclaredVarAssignment(cx, id)) {
+ return false;
+ }
+ }
+
+ // Pure optimization for the common case. There's no point performing the
+ // lookup in step 5.c again, as our caller just did it for us.
+ if (IsQualified && receiver.isObject() && obj == &receiver.toObject()) {
+ // Ensure that a custom GetOwnPropertyOp, if present, doesn't
+ // introduce additional properties which weren't previously found by
+ // LookupOwnProperty.
+#ifdef DEBUG
+ if (GetOwnPropertyOp op = obj->getOpsGetOwnPropertyDescriptor()) {
+ Rooted<mozilla::Maybe<PropertyDescriptor>> desc(cx);
+ if (!op(cx, obj, id, &desc)) {
+ return false;
+ }
+ MOZ_ASSERT(desc.isNothing());
+ }
+#endif
+
+ // Step 5.e. Define the new data property.
+ if (DefinePropertyOp op = obj->getOpsDefineProperty()) {
+ Rooted<PropertyDescriptor> desc(
+ cx, PropertyDescriptor::Data(v, {JS::PropertyAttribute::Configurable,
+ JS::PropertyAttribute::Enumerable,
+ JS::PropertyAttribute::Writable}));
+ return op(cx, obj, id, desc, result);
+ }
+
+ return DefineNonexistentProperty(cx, obj, id, v, result);
+ }
+
+ return SetPropertyByDefining(cx, id, v, receiver, result);
+}
+
+// Set an existing own property obj[index] that's a dense element.
+static bool SetDenseElement(JSContext* cx, Handle<NativeObject*> obj,
+ uint32_t index, HandleValue v,
+ ObjectOpResult& result) {
+ MOZ_ASSERT(!obj->is<TypedArrayObject>());
+ MOZ_ASSERT(obj->containsDenseElement(index));
+
+ obj->setDenseElement(index, v);
+ return result.succeed();
+}
+
+/*
+ * Finish the assignment `receiver[id] = v` when an existing property (shape)
+ * has been found on a native object (pobj). This implements ES6 draft rev 32
+ * (2015 Feb 2) 9.1.9 steps 5 and 6.
+ *
+ * It is necessary to pass both id and shape because shape could be an implicit
+ * dense or typed array element (i.e. not actually a pointer to a Shape).
+ */
+static bool SetExistingProperty(JSContext* cx, HandleId id, HandleValue v,
+ HandleValue receiver,
+ Handle<NativeObject*> pobj,
+ const PropertyResult& prop,
+ ObjectOpResult& result) {
+ // Step 5 for dense elements.
+ if (prop.isDenseElement() || prop.isTypedArrayElement()) {
+ // Step 5.a.
+ if (pobj->denseElementsAreFrozen()) {
+ return result.fail(JSMSG_READ_ONLY);
+ }
+
+ // Pure optimization for the common case:
+ if (receiver.isObject() && pobj == &receiver.toObject()) {
+ if (prop.isTypedArrayElement()) {
+ Rooted<TypedArrayObject*> tobj(cx, &pobj->as<TypedArrayObject>());
+ size_t idx = prop.typedArrayElementIndex();
+ return SetTypedArrayElement(cx, tobj, idx, v, result);
+ }
+
+ return SetDenseElement(cx, pobj, prop.denseElementIndex(), v, result);
+ }
+
+ // Steps 5.b-f.
+ return SetPropertyByDefining(cx, id, v, receiver, result);
+ }
+
+ // Step 5 for all other properties.
+ PropertyInfo propInfo = prop.propertyInfo();
+ if (propInfo.isDataDescriptor()) {
+ // Step 5.a.
+ if (!propInfo.writable()) {
+ return result.fail(JSMSG_READ_ONLY);
+ }
+
+ // steps 5.c-f.
+ if (receiver.isObject() && pobj == &receiver.toObject()) {
+ // Pure optimization for the common case. There's no point performing
+ // the lookup in step 5.c again, as our caller just did it for us. The
+ // result is |shapeProp|.
+
+ // Steps 5.e.i-ii.
+ return NativeSetExistingDataProperty(cx, pobj, id, propInfo, v, result);
+ }
+
+ // Shadow pobj[id] by defining a new data property receiver[id].
+ // Delegate everything to SetPropertyByDefining.
+ return SetPropertyByDefining(cx, id, v, receiver, result);
+ }
+
+ // Steps 6-11.
+ MOZ_ASSERT(propInfo.isAccessorProperty());
+
+ JSObject* setterObject = pobj->getSetter(propInfo);
+ if (!setterObject) {
+ return result.fail(JSMSG_GETTER_ONLY);
+ }
+
+ RootedValue setter(cx, ObjectValue(*setterObject));
+ if (!js::CallSetter(cx, receiver, setter, v)) {
+ return false;
+ }
+
+ return result.succeed();
+}
+
+template <QualifiedBool IsQualified>
+bool js::NativeSetProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, HandleValue v, HandleValue receiver,
+ ObjectOpResult& result) {
+ // Step numbers below reference ES6 rev 27 9.1.9, the [[Set]] internal
+ // method for ordinary objects. We substitute our own names for these names
+ // used in the spec: O -> pobj, P -> id, ownDesc -> shape.
+ PropertyResult prop;
+ Rooted<NativeObject*> pobj(cx, obj);
+
+ // This loop isn't explicit in the spec algorithm. See the comment on step
+ // 4.c.i below. (There's a very similar loop in the NativeGetProperty
+ // implementation, but unfortunately not similar enough to common up.)
+ //
+ // We're intentionally not spec-compliant for TypedArrays:
+ // When |pobj| is a TypedArray and |id| is a TypedArray index, we should
+ // ignore |receiver| and instead always try to set the property on |pobj|.
+ // Bug 1502889 showed that this behavior isn't web-compatible. This issue is
+ // also reported at <https://github.com/tc39/ecma262/issues/1541>.
+ for (;;) {
+ // Steps 2-3.
+ if (!NativeLookupOwnPropertyInline<CanGC>(cx, pobj, id, &prop)) {
+ return false;
+ }
+
+ if (prop.isFound()) {
+ // Steps 5-6.
+ return SetExistingProperty(cx, id, v, receiver, pobj, prop, result);
+ }
+
+ // Steps 4.a-b.
+ // As a side-effect of NativeLookupOwnPropertyInline, we may determine that
+ // a property is not found and the proto chain should not be searched. This
+ // can occur for:
+ // - Out-of-range numeric properties of a TypedArrayObject
+ // - Recursive resolve hooks (which is expected when they try to set the
+ // property being resolved).
+ JSObject* proto = pobj->staticPrototype();
+ if (!proto || prop.shouldIgnoreProtoChain()) {
+ // Step 4.d.i (and step 5).
+ return SetNonexistentProperty<IsQualified>(cx, obj, id, v, receiver,
+ result);
+ }
+
+ // Step 4.c.i. If the prototype is also native, this step is a
+ // recursive tail call, and we don't need to go through all the
+ // plumbing of SetProperty; the top of the loop is where we're going to
+ // end up anyway. But if pobj is non-native, that optimization would be
+ // incorrect.
+ if (!proto->is<NativeObject>()) {
+ // Unqualified assignments are not specified to go through [[Set]]
+ // at all, but they do go through this function. So check for
+ // unqualified assignment to a nonexistent global (a strict error).
+ RootedObject protoRoot(cx, proto);
+ if (!IsQualified) {
+ bool found;
+ if (!HasProperty(cx, protoRoot, id, &found)) {
+ return false;
+ }
+ if (!found) {
+ return SetNonexistentProperty<IsQualified>(cx, obj, id, v, receiver,
+ result);
+ }
+ }
+
+ return SetProperty(cx, protoRoot, id, v, receiver, result);
+ }
+ pobj = &proto->as<NativeObject>();
+ }
+}
+
+template bool js::NativeSetProperty<Qualified>(JSContext* cx,
+ Handle<NativeObject*> obj,
+ HandleId id, HandleValue value,
+ HandleValue receiver,
+ ObjectOpResult& result);
+
+template bool js::NativeSetProperty<Unqualified>(JSContext* cx,
+ Handle<NativeObject*> obj,
+ HandleId id, HandleValue value,
+ HandleValue receiver,
+ ObjectOpResult& result);
+
+bool js::NativeSetElement(JSContext* cx, Handle<NativeObject*> obj,
+ uint32_t index, HandleValue v, HandleValue receiver,
+ ObjectOpResult& result) {
+ RootedId id(cx);
+ if (!IndexToId(cx, index, &id)) {
+ return false;
+ }
+ return NativeSetProperty<Qualified>(cx, obj, id, v, receiver, result);
+}
+
+/*** [[Delete]] *************************************************************/
+
+static bool CallJSDeletePropertyOp(JSContext* cx, JSDeletePropertyOp op,
+ HandleObject receiver, HandleId id,
+ ObjectOpResult& result) {
+ AutoCheckRecursionLimit recursion(cx);
+ if (!recursion.check(cx)) {
+ return false;
+ }
+
+ cx->check(receiver, id);
+ if (op) {
+ return op(cx, receiver, id, result);
+ }
+ return result.succeed();
+}
+
+// ES6 draft rev31 9.1.10 [[Delete]]
+bool js::NativeDeleteProperty(JSContext* cx, Handle<NativeObject*> obj,
+ HandleId id, ObjectOpResult& result) {
+#ifdef ENABLE_RECORD_TUPLE
+ MOZ_ASSERT(!js::IsExtendedPrimitive(*obj));
+#endif
+
+ // Steps 2-3.
+ PropertyResult prop;
+ if (!NativeLookupOwnProperty<CanGC>(cx, obj, id, &prop)) {
+ return false;
+ }
+
+ // Step 4.
+ if (prop.isNotFound()) {
+ // If no property call the class's delProperty hook, passing succeeded
+ // as the result parameter. This always succeeds when there is no hook.
+ return CallJSDeletePropertyOp(cx, obj->getClass()->getDelProperty(), obj,
+ id, result);
+ }
+
+ // Step 6. Non-configurable property.
+ if (!GetPropertyAttributes(obj, prop).configurable()) {
+ return result.failCantDelete();
+ }
+
+ // Typed array elements are configurable, but can't be deleted.
+ if (prop.isTypedArrayElement()) {
+ return result.failCantDelete();
+ }
+
+ if (!CallJSDeletePropertyOp(cx, obj->getClass()->getDelProperty(), obj, id,
+ result)) {
+ return false;
+ }
+ if (!result) {
+ return true;
+ }
+
+ // Step 5.
+ if (prop.isDenseElement()) {
+ obj->setDenseElementHole(prop.denseElementIndex());
+ } else {
+ if (!NativeObject::removeProperty(cx, obj, id)) {
+ return false;
+ }
+ }
+
+ return SuppressDeletedProperty(cx, obj, id);
+}
+
+bool js::CopyDataPropertiesNative(JSContext* cx, Handle<PlainObject*> target,
+ Handle<NativeObject*> from,
+ Handle<PlainObject*> excludedItems,
+ bool* optimized) {
+#ifdef ENABLE_RECORD_TUPLE
+ MOZ_ASSERT(!js::IsExtendedPrimitive(*target));
+#endif
+
+ *optimized = false;
+
+ // Don't use the fast path if |from| may have extra indexed or lazy
+ // properties.
+ if (from->getDenseInitializedLength() > 0 || from->isIndexed() ||
+ from->is<TypedArrayObject>() ||
+ IF_RECORD_TUPLE(from->is<RecordObject>() || from->is<TupleObject>(),
+ false) ||
+ from->getClass()->getNewEnumerate() || from->getClass()->getEnumerate()) {
+ return true;
+ }
+
+ // Collect all enumerable data properties.
+ Rooted<PropertyInfoWithKeyVector> props(cx, PropertyInfoWithKeyVector(cx));
+
+ Rooted<NativeShape*> fromShape(cx, from->shape());
+ for (ShapePropertyIter<NoGC> iter(fromShape); !iter.done(); iter++) {
+ jsid id = iter->key();
+ MOZ_ASSERT(!id.isInt());
+
+ if (!iter->enumerable()) {
+ continue;
+ }
+ if (excludedItems && excludedItems->contains(cx, id)) {
+ continue;
+ }
+
+ // Don't use the fast path if |from| contains non-data properties.
+ //
+ // This enables two optimizations:
+ // 1. We don't need to handle the case when accessors modify |from|.
+ // 2. String and symbol properties can be added in one go.
+ if (!iter->isDataProperty()) {
+ return true;
+ }
+
+ if (!props.append(*iter)) {
+ return false;
+ }
+ }
+
+ *optimized = true;
+
+ // If |target| contains no own properties, we can directly call
+ // AddDataPropertyNonPrototype.
+ const bool targetHadNoOwnProperties = target->empty();
+
+ RootedId key(cx);
+ RootedValue value(cx);
+ for (size_t i = props.length(); i > 0; i--) {
+ PropertyInfoWithKey prop = props[i - 1];
+ MOZ_ASSERT(prop.isDataProperty());
+ MOZ_ASSERT(prop.enumerable());
+
+ key = prop.key();
+ MOZ_ASSERT(!key.isInt());
+
+ MOZ_ASSERT(from->is<NativeObject>());
+ MOZ_ASSERT(from->shape() == fromShape);
+
+ value = from->getSlot(prop.slot());
+ if (targetHadNoOwnProperties) {
+ MOZ_ASSERT(!target->containsPure(key),
+ "didn't expect to find an existing property");
+
+ if (!AddDataPropertyToPlainObject(cx, target, key, value)) {
+ return false;
+ }
+ } else {
+ if (!NativeDefineDataProperty(cx, target, key, value, JSPROP_ENUMERATE)) {
+ return false;
+ }
+ }
+ }
+
+ return true;
+}