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1// Copyright 2020 the V8 project authors. All rights reserved.2// Use of this source code is governed by a BSD-style license that can be3// found in the LICENSE file.4 5#ifndef INCLUDE_CPPGC_PREFINALIZER_H_6#define INCLUDE_CPPGC_PREFINALIZER_H_7 8#include "cppgc/internal/compiler-specific.h"9#include "cppgc/liveness-broker.h"10 11namespace cppgc {12 13namespace internal {14 15class V8_EXPORT PrefinalizerRegistration final {16 public:17  using Callback = bool (*)(const cppgc::LivenessBroker&, void*);18 19  PrefinalizerRegistration(void*, Callback);20 21  void* operator new(size_t, void* location) = delete;22  void* operator new(size_t) = delete;23};24 25}  // namespace internal26 27/**28 * Macro must be used in the private section of `Class` and registers a29 * prefinalization callback `void Class::PreFinalizer()`. The callback is30 * invoked on garbage collection after the collector has found an object to be31 * dead.32 *33 * Callback properties:34 * - The callback is invoked before a possible destructor for the corresponding35 *   object.36 * - The callback may access the whole object graph, irrespective of whether37 *   objects are considered dead or alive.38 * - The callback is invoked on the same thread as the object was created on.39 *40 * Example:41 * \code42 * class WithPrefinalizer : public GarbageCollected<WithPrefinalizer> {43 *   CPPGC_USING_PRE_FINALIZER(WithPrefinalizer, Dispose);44 *45 *  public:46 *   void Trace(Visitor*) const {}47 *   void Dispose() { prefinalizer_called = true; }48 *   ~WithPrefinalizer() {49 *     // prefinalizer_called == true50 *   }51 *  private:52 *   bool prefinalizer_called = false;53 * };54 * \endcode55 */56#define CPPGC_USING_PRE_FINALIZER(Class, PreFinalizer)                         \57 public:                                                                       \58  static bool InvokePreFinalizer(const cppgc::LivenessBroker& liveness_broker, \59                                 void* object) {                               \60    static_assert(cppgc::IsGarbageCollectedOrMixinTypeV<Class>,                \61                  "Only garbage collected objects can have prefinalizers");    \62    Class* self = static_cast<Class*>(object);                                 \63    if (liveness_broker.IsHeapObjectAlive(self)) return false;                 \64    self->PreFinalizer();                                                      \65    return true;                                                               \66  }                                                                            \67                                                                               \68 private:                                                                      \69  CPPGC_NO_UNIQUE_ADDRESS cppgc::internal::PrefinalizerRegistration            \70      prefinalizer_dummy_{this, Class::InvokePreFinalizer};                    \71  static_assert(true, "Force semicolon.")72 73}  // namespace cppgc74 75#endif  // INCLUDE_CPPGC_PREFINALIZER_H_76