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 be 3 // 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 12 namespace cppgc { 13 namespace internal { 14 15 using FinalizationCallback = void (*)(void*); 16 17 template <typename T, typename = void> 18 struct HasFinalizeGarbageCollectedObject : std::false_type {}; 19 20 template <typename T> 21 struct 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. 27 template <typename T, bool isFinalized> 28 struct FinalizerTraitImpl; 29 30 template <typename T> 31 struct 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 56 template <typename T> 57 struct 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 and 64 // what finalization means. 65 template <typename T> 66 struct FinalizerTrait { 67 private: 68 // Object has a finalizer if it has 69 // - a custom FinalizeGarbageCollectedObject method, or 70 // - 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 87 template <typename T> 88 constexpr FinalizationCallback FinalizerTrait<T>::kCallback; 89 90 } // namespace internal 91 } // namespace cppgc 92 93 #endif // INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_ 94