JSObject*
js::Allocate(ExclusiveContext* cx, AllocKind kind, size_t nDynamicSlots, InitialHeap heap,
const Class* clasp)
{
static_assert(mozilla::IsConvertible<T*, JSObject*>::value, "must be JSObject derived");
MOZ_ASSERT(IsObjectAllocKind(kind));
size_t thingSize = Arena::thingSize(kind);
MOZ_ASSERT(thingSize == Arena::thingSize(kind));
MOZ_ASSERT(thingSize >= sizeof(JSObject_Slots0));
static_assert(sizeof(JSObject_Slots0) >= CellSize,
"All allocations must be at least the allocator-imposed minimum size.");
MOZ_ASSERT_IF(nDynamicSlots != 0, clasp->isNative() || clasp->isProxy());
// Off-main-thread alloc cannot trigger GC or make runtime assertions.
if (!cx->isJSContext()) {
JSObject* obj = GCRuntime::tryNewTenuredObject<NoGC>(cx, kind, thingSize, nDynamicSlots);
if (MOZ_UNLIKELY(allowGC && !obj))
ReportOutOfMemory(cx);
return obj;
}
JSContext* ncx = cx->asJSContext();
JSRuntime* rt = ncx->runtime();
if (!rt->gc.checkAllocatorState<allowGC>(ncx, kind))
return nullptr;
if (ncx->nursery().isEnabled() && heap != TenuredHeap) {
JSObject* obj = rt->gc.tryNewNurseryObject<allowGC>(ncx, thingSize, nDynamicSlots, clasp);
if (obj)
return obj;
// Our most common non-jit allocation path is NoGC; thus, if we fail the
// alloc and cannot GC, we *must* return nullptr here so that the caller
// will do a CanGC allocation to clear the nursery. Failing to do so will
// cause all allocations on this path to land in Tenured, and we will not
// get the benefit of the nursery.
if (!allowGC)
return nullptr;
}
return GCRuntime::tryNewTenuredObject<allowGC>(cx, kind, thingSize, nDynamicSlots);
}
