03c38afa41
This CL introduces - GarbageCollectedMixin - IsGarbageCollectedMixinType - HeapObjectHeaderFor (utility method to get correct header for mixins) Bug: chromium:1056170 Change-Id: I48c2c02fa57487824130ea3620c975a0785075e4 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2130275 Commit-Queue: Omer Katz <omerkatz@chromium.org> Reviewed-by: Michael Lippautz <mlippautz@chromium.org> Reviewed-by: Anton Bikineev <bikineev@chromium.org> Reviewed-by: Ulan Degenbaev <ulan@chromium.org> Cr-Commit-Position: refs/heads/master@{#66953}
143 lines
5.0 KiB
C++
143 lines
5.0 KiB
C++
// Copyright 2020 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef INCLUDE_CPPGC_GARBAGE_COLLECTED_H_
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#define INCLUDE_CPPGC_GARBAGE_COLLECTED_H_
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#include <type_traits>
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#include "include/cppgc/internals.h"
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#include "include/cppgc/platform.h"
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#include "include/cppgc/type_traits.h"
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namespace cppgc {
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namespace internal {
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template <typename T, typename = void>
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struct IsGarbageCollectedMixinType : std::false_type {
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static_assert(sizeof(T), "T must be fully defined");
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};
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template <typename T>
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struct IsGarbageCollectedMixinType<
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T,
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void_t<typename std::remove_const_t<T>::IsGarbageCollectedMixinTypeMarker>>
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: std::true_type {
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static_assert(sizeof(T), "T must be fully defined");
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};
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template <typename T, typename = void>
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struct IsGarbageCollectedType : IsGarbageCollectedMixinType<T> {
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static_assert(sizeof(T), "T must be fully defined");
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};
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template <typename T>
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struct IsGarbageCollectedType<
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T, void_t<typename std::remove_const_t<T>::IsGarbageCollectedTypeMarker>>
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: std::true_type {
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static_assert(sizeof(T), "T must be fully defined");
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};
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class GarbageCollectedBase {
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public:
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// Must use MakeGarbageCollected.
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void* operator new(size_t) = delete;
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void* operator new[](size_t) = delete;
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// The garbage collector is taking care of reclaiming the object. Also,
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// virtual destructor requires an unambiguous, accessible 'operator delete'.
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void operator delete(void*) {
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#ifdef V8_ENABLE_CHECKS
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internal::Abort();
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#endif // V8_ENABLE_CHECKS
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}
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void operator delete[](void*) = delete;
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protected:
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GarbageCollectedBase() = default;
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};
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} // namespace internal
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template <typename>
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class GarbageCollected : public internal::GarbageCollectedBase {
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public:
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using IsGarbageCollectedTypeMarker = void;
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protected:
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GarbageCollected() = default;
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};
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class GarbageCollectedMixin : public internal::GarbageCollectedBase {
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public:
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using IsGarbageCollectedMixinTypeMarker = void;
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// Sentinel used to mark not-fully-constructed mixins.
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static constexpr void* kNotFullyConstructedObject = nullptr;
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// TODO(chromium:1056170): Add virtual Trace method.
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protected:
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// Provide default implementation that indicate that the vtable is not yet
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// set up properly. This is used to to get GCInfo objects for mixins so that
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// these objects can be processed later on.
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virtual const void* GetObjectStart() const {
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return kNotFullyConstructedObject;
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}
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GarbageCollectedMixin() = default;
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};
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namespace internal {
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class __thisIsHereToForceASemicolonAfterThisMacro {};
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} // namespace internal
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// The USING_GARBAGE_COLLECTED_MIXIN macro defines all methods and markers
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// needed for handling mixins. HasUsingGarbageCollectedMixinMacro is used
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// by the clang GC plugin to check for proper usages of the
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// USING_GARBAGE_COLLECTED_MIXIN macro.
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#define USING_GARBAGE_COLLECTED_MIXIN() \
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public: \
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typedef int HasUsingGarbageCollectedMixinMacro; \
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const void* GetObjectStart() const override { \
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static_assert( \
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internal::IsSubclassOfTemplate< \
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std::remove_const_t<std::remove_pointer_t<decltype(this)>>, \
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cppgc::GarbageCollected>::value, \
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"Only garbage collected objects can have garbage collected mixins"); \
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return this; \
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} \
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\
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private: \
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friend class internal::__thisIsHereToForceASemicolonAfterThisMacro
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// Merge two or more Mixins into one:
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//
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// class A : public GarbageCollectedMixin {};
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// class B : public GarbageCollectedMixin {};
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// class C : public A, public B {
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// // C::GetObjectStart is now ambiguous because there are two
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// // candidates: A::GetObjectStart and B::GetObjectStart. Ditto for
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// // other functions.
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//
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// MERGE_GARBAGE_COLLECTED_MIXINS();
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// // The macro defines C::GetObjectStart, similar to GarbageCollectedMixin,ß
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// // so that they are no longer ambiguous.
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// // USING_GARBAGE_COLLECTED_MIXIN() overrides them later and provides the
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// // implementations.
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// };
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#define MERGE_GARBAGE_COLLECTED_MIXINS() \
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public: \
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const void* GetObjectStart() const override { \
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return kNotFullyConstructedObject; \
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} \
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\
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private: \
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friend class internal::__thisIsHereToForceASemicolonAfterThisMacro
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} // namespace cppgc
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#endif // INCLUDE_CPPGC_GARBAGE_COLLECTED_H_
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