test/cctest/test-weakmaps.cc

// Copyright 2011 the V8 project authors. All rights reserved.
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#include "v8.h"

#include "global-handles.h"
#include "snapshot.h"
#include "cctest.h"

using namespace v8::internal;


static Handle<JSWeakMap> AllocateJSWeakMap() {
  Handle<Map> map = FACTORY->NewMap(JS_WEAK_MAP_TYPE, JSWeakMap::kSize);
  Handle<JSObject> weakmap_obj = FACTORY->NewJSObjectFromMap(map);
  Handle<JSWeakMap> weakmap(JSWeakMap::cast(*weakmap_obj));
  // Do not use handles for the hash table, it would make entries strong.
  Object* table_obj = ObjectHashTable::Allocate(1)->ToObjectChecked();
  ObjectHashTable* table = ObjectHashTable::cast(table_obj);
  weakmap->set_table(table);
  weakmap->set_next(Smi::FromInt(0));
  return weakmap;
}

static void PutIntoWeakMap(Handle<JSWeakMap> weakmap,
                           Handle<JSObject> key,
                           Handle<Object> value) {
  Handle<ObjectHashTable> table = PutIntoObjectHashTable(
      Handle<ObjectHashTable>(ObjectHashTable::cast(weakmap->table())),
      Handle<JSObject>(JSObject::cast(*key)),
      value);
  weakmap->set_table(*table);
}

static int NumberOfWeakCalls = 0;
static void WeakPointerCallback(v8::Persistent<v8::Value> handle, void* id) {
  ASSERT(id == reinterpret_cast<void*>(1234));
  NumberOfWeakCalls++;
  handle.Dispose();
}


TEST(Weakness) {
  FLAG_incremental_marking = false;
  LocalContext context;
  v8::HandleScope scope;
  Handle<JSWeakMap> weakmap = AllocateJSWeakMap();
  GlobalHandles* global_handles = Isolate::Current()->global_handles();

  // Keep global reference to the key.
  Handle<Object> key;
  {
    v8::HandleScope scope;
    Handle<Map> map = FACTORY->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
    Handle<JSObject> object = FACTORY->NewJSObjectFromMap(map);
    key = global_handles->Create(*object);
  }
  CHECK(!global_handles->IsWeak(key.location()));

  // Put entry into weak map.
  {
    v8::HandleScope scope;
    PutIntoWeakMap(weakmap,
                   Handle<JSObject>(JSObject::cast(*key)),
                   Handle<Smi>(Smi::FromInt(23)));
  }
  CHECK_EQ(1, ObjectHashTable::cast(weakmap->table())->NumberOfElements());

  // Force a full GC.
  HEAP->CollectAllGarbage(false);
  CHECK_EQ(0, NumberOfWeakCalls);
  CHECK_EQ(1, ObjectHashTable::cast(weakmap->table())->NumberOfElements());
  CHECK_EQ(
      0, ObjectHashTable::cast(weakmap->table())->NumberOfDeletedElements());

  // Make the global reference to the key weak.
  {
    v8::HandleScope scope;
    global_handles->MakeWeak(key.location(),
                             reinterpret_cast<void*>(1234),
                             &WeakPointerCallback);
  }
  CHECK(global_handles->IsWeak(key.location()));

  // Force a full GC.
  // Perform two consecutive GCs because the first one will only clear
  // weak references whereas the second one will also clear weak maps.
  HEAP->CollectAllGarbage(false);
  CHECK_EQ(1, NumberOfWeakCalls);
  CHECK_EQ(1, ObjectHashTable::cast(weakmap->table())->NumberOfElements());
  CHECK_EQ(
      0, ObjectHashTable::cast(weakmap->table())->NumberOfDeletedElements());
  HEAP->CollectAllGarbage(false);
  CHECK_EQ(1, NumberOfWeakCalls);
  CHECK_EQ(0, ObjectHashTable::cast(weakmap->table())->NumberOfElements());
  CHECK_EQ(
      1, ObjectHashTable::cast(weakmap->table())->NumberOfDeletedElements());
}


TEST(Shrinking) {
  LocalContext context;
  v8::HandleScope scope;
  Handle<JSWeakMap> weakmap = AllocateJSWeakMap();

  // Check initial capacity.
  CHECK_EQ(32, ObjectHashTable::cast(weakmap->table())->Capacity());

  // Fill up weak map to trigger capacity change.
  {
    v8::HandleScope scope;
    Handle<Map> map = FACTORY->NewMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
    for (int i = 0; i < 32; i++) {
      Handle<JSObject> object = FACTORY->NewJSObjectFromMap(map);
      PutIntoWeakMap(weakmap, object, Handle<Smi>(Smi::FromInt(i)));
    }
  }

  // Check increased capacity.
  CHECK_EQ(128, ObjectHashTable::cast(weakmap->table())->Capacity());

  // Force a full GC.
  CHECK_EQ(32, ObjectHashTable::cast(weakmap->table())->NumberOfElements());
  CHECK_EQ(
      0, ObjectHashTable::cast(weakmap->table())->NumberOfDeletedElements());
  HEAP->CollectAllGarbage(false);
  CHECK_EQ(0, ObjectHashTable::cast(weakmap->table())->NumberOfElements());
  CHECK_EQ(
      32, ObjectHashTable::cast(weakmap->table())->NumberOfDeletedElements());

  // Check shrunk capacity.
  CHECK_EQ(32, ObjectHashTable::cast(weakmap->table())->Capacity());
}


// Test that weak map values on an evacuation candidate which are not reachable
// by other paths are correctly recorded in the slots buffer.
TEST(Regress2060a) {
  FLAG_always_compact = true;
  LocalContext context;
  v8::HandleScope scope;
  Handle<JSFunction> function =
      FACTORY->NewFunction(FACTORY->function_symbol(), FACTORY->null_value());
  Handle<JSObject> key = FACTORY->NewJSObject(function);
  Handle<JSWeakMap> weakmap = AllocateJSWeakMap();

  // Start second old-space page so that values land on evacuation candidate.
  Page* first_page = HEAP->old_pointer_space()->anchor()->next_page();
  FACTORY->NewFixedArray(900 * KB / kPointerSize, TENURED);

  // Fill up weak map with values on an evacuation candidate.
  {
    v8::HandleScope scope;
    for (int i = 0; i < 32; i++) {
      Handle<JSObject> object = FACTORY->NewJSObject(function, TENURED);
      CHECK(!HEAP->InNewSpace(object->address()));
      CHECK(!first_page->Contains(object->address()));
      PutIntoWeakMap(weakmap, key, object);
    }
  }

  // Force compacting garbage collection.
  CHECK(FLAG_always_compact);
  HEAP->CollectAllGarbage(Heap::kNoGCFlags);
}


// Test that weak map keys on an evacuation candidate which are reachable by
// other strong paths are correctly recorded in the slots buffer.
TEST(Regress2060b) {
  FLAG_always_compact = true;
#ifdef VERIFY_HEAP
  FLAG_verify_heap = true;
#endif

  LocalContext context;
  v8::HandleScope scope;
  Handle<JSFunction> function =
      FACTORY->NewFunction(FACTORY->function_symbol(), FACTORY->null_value());

  // Start second old-space page so that keys land on evacuation candidate.
  Page* first_page = HEAP->old_pointer_space()->anchor()->next_page();
  FACTORY->NewFixedArray(900 * KB / kPointerSize, TENURED);

  // Fill up weak map with keys on an evacuation candidate.
  Handle<JSObject> keys[32];
  for (int i = 0; i < 32; i++) {
    keys[i] = FACTORY->NewJSObject(function, TENURED);
    CHECK(!HEAP->InNewSpace(keys[i]->address()));
    CHECK(!first_page->Contains(keys[i]->address()));
  }
  Handle<JSWeakMap> weakmap = AllocateJSWeakMap();
  for (int i = 0; i < 32; i++) {
    PutIntoWeakMap(weakmap, keys[i], Handle<Smi>(Smi::FromInt(i)));
  }

  // Force compacting garbage collection. The subsequent collections are used
  // to verify that key references were actually updated.
  CHECK(FLAG_always_compact);
  HEAP->CollectAllGarbage(Heap::kNoGCFlags);
  HEAP->CollectAllGarbage(Heap::kNoGCFlags);
  HEAP->CollectAllGarbage(Heap::kNoGCFlags);
}