name : finalizer-trait.h // Copyright 2020 the V8 project authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #ifndef INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_ #define INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_ #include <type_traits> #include "cppgc/type-traits.h" namespace cppgc { namespace internal { using FinalizationCallback = void (*)(void*); template <typename T, typename = void> struct HasFinalizeGarbageCollectedObject : std::false_type {}; template <typename T> struct HasFinalizeGarbageCollectedObject< T, std::void_t<decltype(std::declval<T>().FinalizeGarbageCollectedObject())>> : std::true_type {}; // The FinalizerTraitImpl specifies how to finalize objects. template <typename T, bool isFinalized> struct FinalizerTraitImpl; template <typename T> struct FinalizerTraitImpl<T, true> { private: // Dispatch to custom FinalizeGarbageCollectedObject(). struct Custom { static void Call(void* obj) { static_cast<T*>(obj)->FinalizeGarbageCollectedObject(); } }; // Dispatch to regular destructor. struct Destructor { static void Call(void* obj) { static_cast<T*>(obj)->~T(); } }; using FinalizeImpl = std::conditional_t<HasFinalizeGarbageCollectedObject<T>::value, Custom, Destructor>; public: static void Finalize(void* obj) { static_assert(sizeof(T), "T must be fully defined"); FinalizeImpl::Call(obj); } }; template <typename T> struct FinalizerTraitImpl<T, false> { static void Finalize(void* obj) { static_assert(sizeof(T), "T must be fully defined"); } }; // The FinalizerTrait is used to determine if a type requires finalization and // what finalization means. template <typename T> struct FinalizerTrait { private: // Object has a finalizer if it has // - a custom FinalizeGarbageCollectedObject method, or // - a destructor. static constexpr bool kNonTrivialFinalizer = internal::HasFinalizeGarbageCollectedObject<T>::value || !std::is_trivially_destructible<typename std::remove_cv<T>::type>::value; static void Finalize(void* obj) { internal::FinalizerTraitImpl<T, kNonTrivialFinalizer>::Finalize(obj); } public: static constexpr bool HasFinalizer() { return kNonTrivialFinalizer; } // The callback used to finalize an object of type T. static constexpr FinalizationCallback kCallback = kNonTrivialFinalizer ? Finalize : nullptr; }; template <typename T> constexpr FinalizationCallback FinalizerTrait<T>::kCallback; } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_