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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_INTERNAL_FINALIZER_TRAIT_H_6#define INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_7 8#include <type_traits>9 10#include "cppgc/type-traits.h"11 12namespace cppgc {13namespace internal {14 15using FinalizationCallback = void (*)(void*);16 17template <typename T, typename = void>18struct HasFinalizeGarbageCollectedObject : std::false_type {};19 20template <typename T>21struct HasFinalizeGarbageCollectedObject<22    T,23    std::void_t<decltype(std::declval<T>().FinalizeGarbageCollectedObject())>>24    : std::true_type {};25 26// The FinalizerTraitImpl specifies how to finalize objects.27template <typename T, bool isFinalized>28struct FinalizerTraitImpl;29 30template <typename T>31struct FinalizerTraitImpl<T, true> {32 private:33  // Dispatch to custom FinalizeGarbageCollectedObject().34  struct Custom {35    static void Call(void* obj) {36      static_cast<T*>(obj)->FinalizeGarbageCollectedObject();37    }38  };39 40  // Dispatch to regular destructor.41  struct Destructor {42    static void Call(void* obj) { static_cast<T*>(obj)->~T(); }43  };44 45  using FinalizeImpl =46      std::conditional_t<HasFinalizeGarbageCollectedObject<T>::value, Custom,47                         Destructor>;48 49 public:50  static void Finalize(void* obj) {51    static_assert(sizeof(T), "T must be fully defined");52    FinalizeImpl::Call(obj);53  }54};55 56template <typename T>57struct FinalizerTraitImpl<T, false> {58  static void Finalize(void* obj) {59    static_assert(sizeof(T), "T must be fully defined");60  }61};62 63// The FinalizerTrait is used to determine if a type requires finalization and64// what finalization means.65template <typename T>66struct FinalizerTrait {67 private:68  // Object has a finalizer if it has69  // - a custom FinalizeGarbageCollectedObject method, or70  // - a destructor.71  static constexpr bool kNonTrivialFinalizer =72      internal::HasFinalizeGarbageCollectedObject<T>::value ||73      !std::is_trivially_destructible<typename std::remove_cv<T>::type>::value;74 75  static void Finalize(void* obj) {76    internal::FinalizerTraitImpl<T, kNonTrivialFinalizer>::Finalize(obj);77  }78 79 public:80  static constexpr bool HasFinalizer() { return kNonTrivialFinalizer; }81 82  // The callback used to finalize an object of type T.83  static constexpr FinalizationCallback kCallback =84      kNonTrivialFinalizer ? Finalize : nullptr;85};86 87template <typename T>88constexpr FinalizationCallback FinalizerTrait<T>::kCallback;89 90}  // namespace internal91}  // namespace cppgc92 93#endif  // INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_94