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Diffstat (limited to 'js/src/vm/NativeObject.cpp')
| -rw-r--r-- | js/src/vm/NativeObject.cpp | 2791 |
1 files changed, 2791 insertions, 0 deletions
diff --git a/js/src/vm/NativeObject.cpp b/js/src/vm/NativeObject.cpp new file mode 100644 index 0000000000..1654cc2649 --- /dev/null +++ b/js/src/vm/NativeObject.cpp @@ -0,0 +1,2791 @@ +/* -*- 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 "js/friend/ErrorMessages.h" // js::GetErrorMessage, JSMSG_* +#include "js/friend/StackLimits.h" // js::AutoCheckRecursionLimit +#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/PlainObject.h" // js::PlainObject +#include "vm/TypedArrayObject.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) {} +}; + +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; +} + +#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(); +} + +#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::growSlots(JSContext* cx, uint32_t oldCapacity, + uint32_t newCapacity) { + MOZ_ASSERT(newCapacity > oldCapacity); + MOZ_ASSERT_IF(!is<ArrayObject>(), newCapacity >= SLOT_CAPACITY_MIN); + + /* + * Slot capacities are determined by the span of allocated objects. Due to + * the limited number of bits to store shape slots, object growth is + * throttled well before the slot capacity can overflow. + */ + NativeObject::slotsSizeMustNotOverflow(); + MOZ_ASSERT(newCapacity <= MAX_SLOTS_COUNT); + + if (!hasDynamicSlots()) { + return allocateSlots(cx, newCapacity); + } + + 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 = ReallocateObjectBuffer<HeapSlot>( + cx, this, reinterpret_cast<HeapSlot*>(oldHeaderSlots), oldAllocated, + newAllocated); + if (!allocation) { + return false; /* Leave slots at its old size. */ + } + + auto* newHeaderSlots = + new (allocation) ObjectSlots(newCapacity, dictionarySpan); + 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::allocateSlots(JSContext* cx, uint32_t newCapacity) { + MOZ_ASSERT(!hasDynamicSlots()); + + uint32_t newAllocated = ObjectSlots::allocCount(newCapacity); + + uint32_t dictionarySpan = getSlotsHeader()->dictionarySlotSpan(); + + HeapSlot* allocation = AllocateObjectBuffer<HeapSlot>(cx, this, newAllocated); + if (!allocation) { + return false; + } + + auto* newHeaderSlots = + new (allocation) ObjectSlots(newCapacity, dictionarySpan); + 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. + MOZ_ASSERT(cx->isMainThreadContext()); + + 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(newCapacity < oldCapacity); + MOZ_ASSERT(oldCapacity == getSlotsHeader()->capacity()); + + ObjectSlots* oldHeaderSlots = ObjectSlots::fromSlots(slots_); + MOZ_ASSERT(oldHeaderSlots->capacity() == oldCapacity); + + uint32_t oldAllocated = ObjectSlots::allocCount(oldCapacity); + + if (newCapacity == 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>(), newCapacity >= SLOT_CAPACITY_MIN); + + uint32_t dictionarySpan = getSlotsHeader()->dictionarySlotSpan(); + + uint32_t newAllocated = ObjectSlots::allocCount(newCapacity); + + HeapSlot* allocation = ReallocateObjectBuffer<HeapSlot>( + cx, this, reinterpret_cast<HeapSlot*>(oldHeaderSlots), oldAllocated, + newAllocated); + 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); + 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 (cx->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 SLOT_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 < SLOT_CAPACITY_MIN) { + amount = SLOT_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 = ReallocateObjectBuffer<HeapSlot>( + cx, this, oldHeaderSlots, oldAllocated, newAllocated); + 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 = AllocateObjectBuffer<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 = ReallocateObjectBuffer<HeapSlot>( + cx, this, oldHeaderSlots, oldAllocated, newAllocated); + 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)) { + MOZ_ASSERT(!cx->isHelperThreadContext()); + + 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)) { + MOZ_ASSERT(!cx->isHelperThreadContext()); + + 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_ASSERT(!cx->isHelperThreadContext()); + 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, ¤tValue)) { + 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); + } + + MOZ_ASSERT(!cx->isHelperThreadContext()); + 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)) { + MOZ_ASSERT(!cx->isHelperThreadContext()); + 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.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, ¤tValue)) { + 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, ¤tValue)) { + return false; + } + + if (!desc.hasValue()) { + // Fill in desc.[[Value]]. + desc.setValue(currentValue); + } else { + // Step 7.a.i.2. + bool same; + MOZ_ASSERT(!cx->isHelperThreadContext()); + 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. + MOZ_ASSERT(!cx->isHelperThreadContext()); + 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. + MOZ_ASSERT(!cx->isHelperThreadContext()); + 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>()) { + // 9.4.5.5 step 2. Indexed properties of typed arrays are special. + if (mozilla::Maybe<uint64_t> index = ToTypedArrayIndex(id)) { + // This method is only called for non-existent properties, which + // means any absent indexed property must be out of range. + MOZ_ASSERT(index.value() >= obj->as<TypedArrayObject>().length()); + + // The following steps refer to 9.4.5.11 IntegerIndexedElementSet. + + // Step 1 is enforced by the caller. + + // Steps 2-3. + // We still need to call ToNumber or ToBigInt, because of its + // possible side effects. + if (!obj->as<TypedArrayObject>().convertForSideEffect(cx, v)) { + return false; + } + + // Step 4 (nothing to do, the index is out of range). + + // Step 5. + return result.succeed(); + } + } 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 (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()) { + MOZ_ASSERT(!cx->isHelperThreadContext()); + + 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; +} |