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Edit File: garbage-collected.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_GARBAGE_COLLECTED_H_ #define INCLUDE_CPPGC_GARBAGE_COLLECTED_H_ #include "cppgc/internal/api-constants.h" #include "cppgc/platform.h" #include "cppgc/trace-trait.h" #include "cppgc/type-traits.h" namespace cppgc { class Visitor; /** * Base class for managed objects. Only descendent types of `GarbageCollected` * can be constructed using `MakeGarbageCollected()`. Must be inherited from as * left-most base class. * * Types inheriting from GarbageCollected must provide a method of * signature `void Trace(cppgc::Visitor*) const` that dispatchs all managed * pointers to the visitor and delegates to garbage-collected base classes. * The method must be virtual if the type is not directly a child of * GarbageCollected and marked as final. * * \code * // Example using final class. * class FinalType final : public GarbageCollected<FinalType> { * public: * void Trace(cppgc::Visitor* visitor) const { * // Dispatch using visitor->Trace(...); * } * }; * * // Example using non-final base class. * class NonFinalBase : public GarbageCollected<NonFinalBase> { * public: * virtual void Trace(cppgc::Visitor*) const {} * }; * * class FinalChild final : public NonFinalBase { * public: * void Trace(cppgc::Visitor* visitor) const final { * // Dispatch using visitor->Trace(...); * NonFinalBase::Trace(visitor); * } * }; * \endcode */ template <typename T> class GarbageCollected { public: using IsGarbageCollectedTypeMarker = void; using ParentMostGarbageCollectedType = T; // Must use MakeGarbageCollected. void* operator new(size_t) = delete; void* operator new[](size_t) = delete; // The garbage collector is taking care of reclaiming the object. Also, // virtual destructor requires an unambiguous, accessible 'operator delete'. void operator delete(void*) { #ifdef V8_ENABLE_CHECKS internal::Fatal( "Manually deleting a garbage collected object is not allowed"); #endif // V8_ENABLE_CHECKS } void operator delete[](void*) = delete; protected: GarbageCollected() = default; }; /** * Base class for managed mixin objects. Such objects cannot be constructed * directly but must be mixed into the inheritance hierarchy of a * GarbageCollected object. * * Types inheriting from GarbageCollectedMixin must override a virtual method * of signature `void Trace(cppgc::Visitor*) const` that dispatchs all managed * pointers to the visitor and delegates to base classes. * * \code * class Mixin : public GarbageCollectedMixin { * public: * void Trace(cppgc::Visitor* visitor) const override { * // Dispatch using visitor->Trace(...); * } * }; * \endcode */ class GarbageCollectedMixin { public: using IsGarbageCollectedMixinTypeMarker = void; // Must use MakeGarbageCollected. void* operator new(size_t) = delete; void* operator new[](size_t) = delete; // The garbage collector is taking care of reclaiming the object. // Not override the non-array varaint of `delete` to not conflict with the // operator in GarbageCollected above. void operator delete[](void*) = delete; /** * This Trace method must be overriden by objects inheriting from * GarbageCollectedMixin. */ virtual void Trace(cppgc::Visitor*) const {} }; } // namespace cppgc #endif // INCLUDE_CPPGC_GARBAGE_COLLECTED_H_