chromium/v8/include/cppgc/internal/pointer-policies.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_POINTER_POLICIES_H_
#define INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_

#include <cstdint>
#include <type_traits>

#include "cppgc/internal/member-storage.h"
#include "cppgc/internal/write-barrier.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/source-location.h"
#include "cppgc/type-traits.h"
#include "v8config.h"  // NOLINT(build/include_directory)

namespace cppgc {
namespace internal {

class HeapBase;
class PersistentRegion;
class CrossThreadPersistentRegion;

// Tags to distinguish between strong and weak member types.
class StrongMemberTag;
class WeakMemberTag;
class UntracedMemberTag;

struct DijkstraWriteBarrierPolicy { … };

struct NoWriteBarrierPolicy { … };

class V8_EXPORT SameThreadEnabledCheckingPolicyBase { … };

template <bool kCheckOffHeapAssignments>
class V8_EXPORT SameThreadEnabledCheckingPolicy
    : private SameThreadEnabledCheckingPolicyBase { … };

class DisabledCheckingPolicy { … };

#ifdef DEBUG
// Off heap members are not connected to object graph and thus cannot ressurect
// dead objects.
using DefaultMemberCheckingPolicy =
    SameThreadEnabledCheckingPolicy<false /* kCheckOffHeapAssignments*/>;
using DefaultPersistentCheckingPolicy =
    SameThreadEnabledCheckingPolicy<true /* kCheckOffHeapAssignments*/>;
#else   // !DEBUG
DefaultMemberCheckingPolicy;
DefaultPersistentCheckingPolicy;
#endif  // !DEBUG
// For CT(W)P neither marking information (for value), nor objectstart bitmap
// (for slot) are guaranteed to be present because there's no synchronization
// between heaps after marking.
DefaultCrossThreadPersistentCheckingPolicy;

class KeepLocationPolicy { … };

class IgnoreLocationPolicy { … };

#if CPPGC_SUPPORTS_OBJECT_NAMES
using DefaultLocationPolicy = KeepLocationPolicy;
#else
DefaultLocationPolicy;
#endif

struct StrongPersistentPolicy { … };

struct WeakPersistentPolicy { … };

struct StrongCrossThreadPersistentPolicy { … };

struct WeakCrossThreadPersistentPolicy { … };

// Forward declarations setting up the default policies.
template <typename T, typename WeaknessPolicy,
          typename LocationPolicy = DefaultLocationPolicy,
          typename CheckingPolicy = DefaultCrossThreadPersistentCheckingPolicy>
class BasicCrossThreadPersistent;
template <typename T, typename WeaknessPolicy,
          typename LocationPolicy = DefaultLocationPolicy,
          typename CheckingPolicy = DefaultPersistentCheckingPolicy>
class BasicPersistent;
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
          typename CheckingPolicy = DefaultMemberCheckingPolicy,
          typename StorageType = DefaultMemberStorage>
class BasicMember;

}  // namespace internal

}  // namespace cppgc

#endif  // INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_