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// 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_GC_INFO_H_
#define INCLUDE_CPPGC_INTERNAL_GC_INFO_H_
#include <atomic>
#include <cstdint>
#include <type_traits>
#include "cppgc/internal/finalizer-trait.h"
#include "cppgc/internal/name-trait.h"
#include "cppgc/trace-trait.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
using GCInfoIndex = uint16_t;
// Acquires a new GC info object and returns the index. In addition, also
// updates `registered_index` atomically.
V8_EXPORT GCInfoIndex
EnsureGCInfoIndex(std::atomic<GCInfoIndex>& registered_index,
FinalizationCallback, TraceCallback, NameCallback, bool);
// Fold types based on finalizer behavior. Note that finalizer characteristics
// align with trace behavior, i.e., destructors are virtual when trace methods
// are and vice versa.
template <typename T, typename ParentMostGarbageCollectedType>
struct GCInfoFolding {
static constexpr bool kHasVirtualDestructorAtBase =
std::has_virtual_destructor<ParentMostGarbageCollectedType>::value;
static constexpr bool kBothTypesAreTriviallyDestructible =
std::is_trivially_destructible<ParentMostGarbageCollectedType>::value &&
std::is_trivially_destructible<T>::value;
static constexpr bool kHasCustomFinalizerDispatchAtBase =
internal::HasFinalizeGarbageCollectedObject<
ParentMostGarbageCollectedType>::value;
#ifdef CPPGC_SUPPORTS_OBJECT_NAMES
static constexpr bool kWantsDetailedObjectNames = true;
#else // !CPPGC_SUPPORTS_OBJECT_NAMES
static constexpr bool kWantsDetailedObjectNames = false;
#endif // !CPPGC_SUPPORTS_OBJECT_NAMES
// Folding would regresses name resolution when deriving names from C++
// class names as it would just folds a name to the base class name.
using ResultType = std::conditional_t<(kHasVirtualDestructorAtBase ||
kBothTypesAreTriviallyDestructible ||
kHasCustomFinalizerDispatchAtBase) &&
!kWantsDetailedObjectNames,
ParentMostGarbageCollectedType, T>;
};
// Trait determines how the garbage collector treats objects wrt. to traversing,
// finalization, and naming.
template <typename T>
struct GCInfoTrait final {
static GCInfoIndex Index() {
static_assert(sizeof(T), "T must be fully defined");
static std::atomic<GCInfoIndex>
registered_index; // Uses zero initialization.
const GCInfoIndex index = registered_index.load(std::memory_order_acquire);
return index ? index
: EnsureGCInfoIndex(
registered_index, FinalizerTrait<T>::kCallback,
TraceTrait<T>::Trace, NameTrait<T>::GetName,
std::is_polymorphic<T>::value);
}
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_GC_INFO_H_
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