Fix garbage cycle collection for kotlin.Array

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/RTTIGenerator.kt

@@ -165,6 +165,12 @@ internal class RTTIGenerator(override val context: Context) : ContextUtils {
         val objOffsetsPtr = staticData.placeGlobalConstArray("krefs:$className", int32Type,
                 objOffsets.map { Int32(it.toInt()) })
 
+        val objOffsetsCount = if (classDesc.descriptor == context.builtIns.array) {
+            1 // To mark it as non-leaf.
+        } else {
+            objOffsets.size
+        }
+
         val fields = llvmDeclarations.fields.mapIndexed { index, field ->
             // Note: using FQ name because a class may have multiple fields with the same name due to property overriding
             val nameSignature = field.fqNameSafe.localHash // FIXME: add signature
@@ -191,7 +197,7 @@ internal class RTTIGenerator(override val context: Context) : ContextUtils {
                 name,
                 size,
                 superType,
-                objOffsetsPtr, objOffsets.size,
+                objOffsetsPtr, objOffsetsCount,
                 interfacesPtr, interfaces.size,
                 methodsPtr, methods.size,
                 fieldsPtr, if (classDesc.isInterface) -1 else fields.size,

backend.native/tests/build.gradle

@@ -2117,6 +2117,10 @@ task memory_cycles0(type: RunKonanTest) {
     source = "runtime/memory/cycles0.kt"
 }
 
+task memory_cycles1(type: RunKonanTest) {
+    source = "runtime/memory/cycles1.kt"
+}
+
 task memory_basic0(type: RunKonanTest) {
     source = "runtime/memory/basic0.kt"
 }

backend.native/tests/runtime/memory/cycles1.kt

@@ -0,0 +1,17 @@
+package runtime.memory.cycles1
+
+import kotlin.test.*
+import konan.ref.*
+
+@Test fun runTest() {
+    val weakRefToTrashCycle = createLoop()
+    konan.internal.GC.collect()
+    assertNull(weakRefToTrashCycle.get())
+}
+
+private fun createLoop(): WeakReference<Any> {
+    val loop = Array<Any?>(1, { null })
+    loop[0] = loop
+
+    return WeakReference(loop)
+}

runtime/src/main/cpp/Memory.cpp

@@ -442,12 +442,13 @@ inline void traverseContainerObjectFields(ContainerHeader* container, func proce
   ObjHeader* obj = reinterpret_cast<ObjHeader*>(container + 1);
   for (int object = 0; object < container->objectCount(); object++) {
     const TypeInfo* typeInfo = obj->type_info();
-    for (int index = 0; index < typeInfo->objOffsetsCount_; index++) {
-      ObjHeader** location = reinterpret_cast<ObjHeader**>(
-          reinterpret_cast<uintptr_t>(obj + 1) + typeInfo->objOffsets_[index]);
-      process(location);
-    }
-    if (typeInfo == theArrayTypeInfo) {
+    if (typeInfo != theArrayTypeInfo) {
+      for (int index = 0; index < typeInfo->objOffsetsCount_; index++) {
+        ObjHeader** location = reinterpret_cast<ObjHeader**>(
+            reinterpret_cast<uintptr_t>(obj + 1) + typeInfo->objOffsets_[index]);
+        process(location);
+      }
+    } else {
       ArrayHeader* array = obj->array();
       for (int index = 0; index < array->count_; index++) {
         process(ArrayAddressOfElementAt(array, index));

runtime/src/main/cpp/TypeInfo.h

@@ -81,8 +81,10 @@ struct TypeInfo {
     int32_t instanceSize_;
     // Must be pointer to Any for array classes, and null for Any.
     const TypeInfo* superType_;
-    // All object references inside this object.
+    // All object reference fields inside this object.
     const int32_t* objOffsets_;
+    // Count of object reference fields inside this object.
+    // 1 for kotlin.Array to mark it as non-leaf.
     int32_t objOffsetsCount_;
     const TypeInfo* const* implementedInterfaces_;
     int32_t implementedInterfacesCount_;