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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_ALLOCATION_H_
#define INCLUDE_CPPGC_ALLOCATION_H_
#include <atomic>
#include <cstddef>
#include <cstdint>
#include <new>
#include <type_traits>
#include <utility>
#include "cppgc/custom-space.h"
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/gc-info.h"
#include "cppgc/type-traits.h"
#include "v8config.h" // NOLINT(build/include_directory)
#if defined(__has_attribute)
#if __has_attribute(assume_aligned)
#define CPPGC_DEFAULT_ALIGNED \
__attribute__((assume_aligned(api_constants::kDefaultAlignment)))
#define CPPGC_DOUBLE_WORD_ALIGNED \
__attribute__((assume_aligned(2 * api_constants::kDefaultAlignment)))
#endif // __has_attribute(assume_aligned)
#endif // defined(__has_attribute)
#if !defined(CPPGC_DEFAULT_ALIGNED)
#define CPPGC_DEFAULT_ALIGNED
#endif
#if !defined(CPPGC_DOUBLE_WORD_ALIGNED)
#define CPPGC_DOUBLE_WORD_ALIGNED
#endif
namespace cppgc {
/**
* AllocationHandle is used to allocate garbage-collected objects.
*/
class AllocationHandle;
namespace internal {
// Similar to C++17 std::align_val_t;
enum class AlignVal : size_t {};
class V8_EXPORT MakeGarbageCollectedTraitInternal {
protected:
static inline void MarkObjectAsFullyConstructed(const void* payload) {
// See api_constants for an explanation of the constants.
std::atomic<uint16_t>* atomic_mutable_bitfield =
reinterpret_cast<std::atomic<uint16_t>*>(
const_cast<uint16_t*>(reinterpret_cast<const uint16_t*>(
reinterpret_cast<const uint8_t*>(payload) -
api_constants::kFullyConstructedBitFieldOffsetFromPayload)));
// It's safe to split use load+store here (instead of a read-modify-write
// operation), since it's guaranteed that this 16-bit bitfield is only
// modified by a single thread. This is cheaper in terms of code bloat (on
// ARM) and performance.
uint16_t value = atomic_mutable_bitfield->load(std::memory_order_relaxed);
value |= api_constants::kFullyConstructedBitMask;
atomic_mutable_bitfield->store(value, std::memory_order_release);
}
// Dispatch based on compile-time information.
//
// Default implementation is for a custom space with >`kDefaultAlignment` byte
// alignment.
template <typename GCInfoType, typename CustomSpace, size_t alignment>
struct AllocationDispatcher final {
static void* Invoke(AllocationHandle& handle, size_t size) {
static_assert(std::is_base_of<CustomSpaceBase, CustomSpace>::value,
"Custom space must inherit from CustomSpaceBase.");
static_assert(
!CustomSpace::kSupportsCompaction,
"Custom spaces that support compaction do not support allocating "
"objects with non-default (i.e. word-sized) alignment.");
return MakeGarbageCollectedTraitInternal::Allocate(
handle, size, static_cast<AlignVal>(alignment),
internal::GCInfoTrait<GCInfoType>::Index(), CustomSpace::kSpaceIndex);
}
};
// Fast path for regular allocations for the default space with
// `kDefaultAlignment` byte alignment.
template <typename GCInfoType>
struct AllocationDispatcher<GCInfoType, void,
api_constants::kDefaultAlignment>
final {
static void* Invoke(AllocationHandle& handle, size_t size) {
return MakeGarbageCollectedTraitInternal::Allocate(
handle, size, internal::GCInfoTrait<GCInfoType>::Index());
}
};
// Default space with >`kDefaultAlignment` byte alignment.
template <typename GCInfoType, size_t alignment>
struct AllocationDispatcher<GCInfoType, void, alignment> final {
static void* Invoke(AllocationHandle& handle, size_t size) {
return MakeGarbageCollectedTraitInternal::Allocate(
handle, size, static_cast<AlignVal>(alignment),
internal::GCInfoTrait<GCInfoType>::Index());
}
};
// Custom space with `kDefaultAlignment` byte alignment.
template <typename GCInfoType, typename CustomSpace>
struct AllocationDispatcher<GCInfoType, CustomSpace,
api_constants::kDefaultAlignment>
final {
static void* Invoke(AllocationHandle& handle, size_t size) {
static_assert(std::is_base_of<CustomSpaceBase, CustomSpace>::value,
"Custom space must inherit from CustomSpaceBase.");
return MakeGarbageCollectedTraitInternal::Allocate(
handle, size, internal::GCInfoTrait<GCInfoType>::Index(),
CustomSpace::kSpaceIndex);
}
};
private:
static void* CPPGC_DEFAULT_ALIGNED Allocate(cppgc::AllocationHandle&, size_t,
GCInfoIndex);
static void* CPPGC_DOUBLE_WORD_ALIGNED Allocate(cppgc::AllocationHandle&,
size_t, AlignVal,
GCInfoIndex);
static void* CPPGC_DEFAULT_ALIGNED Allocate(cppgc::AllocationHandle&, size_t,
GCInfoIndex, CustomSpaceIndex);
static void* CPPGC_DOUBLE_WORD_ALIGNED Allocate(cppgc::AllocationHandle&,
size_t, AlignVal, GCInfoIndex,
CustomSpaceIndex);
friend class HeapObjectHeader;
};
} // namespace internal
/**
* Base trait that provides utilities for advancers users that have custom
* allocation needs (e.g., overriding size). It's expected that users override
* MakeGarbageCollectedTrait (see below) and inherit from
* MakeGarbageCollectedTraitBase and make use of the low-level primitives
* offered to allocate and construct an object.
*/
template <typename T>
class MakeGarbageCollectedTraitBase
: private internal::MakeGarbageCollectedTraitInternal {
private:
static_assert(internal::IsGarbageCollectedType<T>::value,
"T needs to be a garbage collected object");
static_assert(!IsGarbageCollectedWithMixinTypeV<T> ||
sizeof(T) <=
internal::api_constants::kLargeObjectSizeThreshold,
"GarbageCollectedMixin may not be a large object");
protected:
/**
* Allocates memory for an object of type T.
*
* \param handle AllocationHandle identifying the heap to allocate the object
* on.
* \param size The size that should be reserved for the object.
* \returns the memory to construct an object of type T on.
*/
V8_INLINE static void* Allocate(AllocationHandle& handle, size_t size) {
static_assert(
std::is_base_of<typename T::ParentMostGarbageCollectedType, T>::value,
"U of GarbageCollected<U> must be a base of T. Check "
"GarbageCollected<T> base class inheritance.");
static constexpr size_t kWantedAlignment =
alignof(T) < internal::api_constants::kDefaultAlignment
? internal::api_constants::kDefaultAlignment
: alignof(T);
static_assert(
kWantedAlignment <= internal::api_constants::kMaxSupportedAlignment,
"Requested alignment larger than alignof(std::max_align_t) bytes. "
"Please file a bug to possibly get this restriction lifted.");
return AllocationDispatcher<
typename internal::GCInfoFolding<
T, typename T::ParentMostGarbageCollectedType>::ResultType,
typename SpaceTrait<T>::Space, kWantedAlignment>::Invoke(handle, size);
}
/**
* Marks an object as fully constructed, resulting in precise handling by the
* garbage collector.
*
* \param payload The base pointer the object is allocated at.
*/
V8_INLINE static void MarkObjectAsFullyConstructed(const void* payload) {
internal::MakeGarbageCollectedTraitInternal::MarkObjectAsFullyConstructed(
payload);
}
};
/**
* Passed to MakeGarbageCollected to specify how many bytes should be appended
* to the allocated object.
*
* Example:
* \code
* class InlinedArray final : public GarbageCollected<InlinedArray> {
* public:
* explicit InlinedArray(size_t bytes) : size(bytes), byte_array(this + 1) {}
* void Trace(Visitor*) const {}
* size_t size;
* char* byte_array;
* };
*
* auto* inlined_array = MakeGarbageCollected<InlinedArray(
* GetAllocationHandle(), AdditionalBytes(4), 4);
* for (size_t i = 0; i < 4; i++) {
* Process(inlined_array->byte_array[i]);
* }
* \endcode
*/
struct AdditionalBytes {
constexpr explicit AdditionalBytes(size_t bytes) : value(bytes) {}
const size_t value;
};
/**
* Default trait class that specifies how to construct an object of type T.
* Advanced users may override how an object is constructed using the utilities
* that are provided through MakeGarbageCollectedTraitBase.
*
* Any trait overriding construction must
* - allocate through `MakeGarbageCollectedTraitBase<T>::Allocate`;
* - mark the object as fully constructed using
* `MakeGarbageCollectedTraitBase<T>::MarkObjectAsFullyConstructed`;
*/
template <typename T>
class MakeGarbageCollectedTrait : public MakeGarbageCollectedTraitBase<T> {
public:
template <typename... Args>
static T* Call(AllocationHandle& handle, Args&&... args) {
void* memory =
MakeGarbageCollectedTraitBase<T>::Allocate(handle, sizeof(T));
T* object = ::new (memory) T(std::forward<Args>(args)...);
MakeGarbageCollectedTraitBase<T>::MarkObjectAsFullyConstructed(object);
return object;
}
template <typename... Args>
static T* Call(AllocationHandle& handle, AdditionalBytes additional_bytes,
Args&&... args) {
void* memory = MakeGarbageCollectedTraitBase<T>::Allocate(
handle, sizeof(T) + additional_bytes.value);
T* object = ::new (memory) T(std::forward<Args>(args)...);
MakeGarbageCollectedTraitBase<T>::MarkObjectAsFullyConstructed(object);
return object;
}
};
/**
* Allows users to specify a post-construction callback for specific types. The
* callback is invoked on the instance of type T right after it has been
* constructed. This can be useful when the callback requires a
* fully-constructed object to be able to dispatch to virtual methods.
*/
template <typename T, typename = void>
struct PostConstructionCallbackTrait {
static void Call(T*) {}
};
/**
* Constructs a managed object of type T where T transitively inherits from
* GarbageCollected.
*
* \param args List of arguments with which an instance of T will be
* constructed.
* \returns an instance of type T.
*/
template <typename T, typename... Args>
V8_INLINE T* MakeGarbageCollected(AllocationHandle& handle, Args&&... args) {
T* object =
MakeGarbageCollectedTrait<T>::Call(handle, std::forward<Args>(args)...);
PostConstructionCallbackTrait<T>::Call(object);
return object;
}
/**
* Constructs a managed object of type T where T transitively inherits from
* GarbageCollected. Created objects will have additional bytes appended to
* it. Allocated memory would suffice for `sizeof(T) + additional_bytes`.
*
* \param additional_bytes Denotes how many bytes to append to T.
* \param args List of arguments with which an instance of T will be
* constructed.
* \returns an instance of type T.
*/
template <typename T, typename... Args>
V8_INLINE T* MakeGarbageCollected(AllocationHandle& handle,
AdditionalBytes additional_bytes,
Args&&... args) {
T* object = MakeGarbageCollectedTrait<T>::Call(handle, additional_bytes,
std::forward<Args>(args)...);
PostConstructionCallbackTrait<T>::Call(object);
return object;
}
} // namespace cppgc
#undef CPPGC_DEFAULT_ALIGNED
#undef CPPGC_DOUBLE_WORD_ALIGNED
#endif // INCLUDE_CPPGC_ALLOCATION_H_

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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_COMMON_H_
#define INCLUDE_CPPGC_COMMON_H_
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
/**
* Indicator for the stack state of the embedder.
*/
enum class EmbedderStackState {
/**
* Stack may contain interesting heap pointers.
*/
kMayContainHeapPointers,
/**
* Stack does not contain any interesting heap pointers.
*/
kNoHeapPointers,
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_COMMON_H_

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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_CROSS_THREAD_PERSISTENT_H_
#define INCLUDE_CPPGC_CROSS_THREAD_PERSISTENT_H_
#include <atomic>
#include "cppgc/internal/persistent-node.h"
#include "cppgc/internal/pointer-policies.h"
#include "cppgc/persistent.h"
#include "cppgc/visitor.h"
namespace cppgc {
namespace internal {
// Wrapper around PersistentBase that allows accessing poisoned memory when
// using ASAN. This is needed as the GC of the heap that owns the value
// of a CTP, may clear it (heap termination, weakness) while the object
// holding the CTP may be poisoned as itself may be deemed dead.
class CrossThreadPersistentBase : public PersistentBase {
public:
CrossThreadPersistentBase() = default;
explicit CrossThreadPersistentBase(const void* raw) : PersistentBase(raw) {}
V8_CLANG_NO_SANITIZE("address") const void* GetValueFromGC() const {
return raw_;
}
V8_CLANG_NO_SANITIZE("address")
PersistentNode* GetNodeFromGC() const { return node_; }
V8_CLANG_NO_SANITIZE("address")
void ClearFromGC() const {
raw_ = nullptr;
SetNodeSafe(nullptr);
}
// GetNodeSafe() can be used for a thread-safe IsValid() check in a
// double-checked locking pattern. See ~BasicCrossThreadPersistent.
PersistentNode* GetNodeSafe() const {
return reinterpret_cast<std::atomic<PersistentNode*>*>(&node_)->load(
std::memory_order_acquire);
}
// The GC writes using SetNodeSafe() while holding the lock.
V8_CLANG_NO_SANITIZE("address")
void SetNodeSafe(PersistentNode* value) const {
#if defined(__has_feature)
#if __has_feature(address_sanitizer)
#define V8_IS_ASAN 1
#endif
#endif
#ifdef V8_IS_ASAN
__atomic_store(&node_, &value, __ATOMIC_RELEASE);
#else // !V8_IS_ASAN
// Non-ASAN builds can use atomics. This also covers MSVC which does not
// have the __atomic_store intrinsic.
reinterpret_cast<std::atomic<PersistentNode*>*>(&node_)->store(
value, std::memory_order_release);
#endif // !V8_IS_ASAN
#undef V8_IS_ASAN
}
};
template <typename T, typename WeaknessPolicy, typename LocationPolicy,
typename CheckingPolicy>
class BasicCrossThreadPersistent final : public CrossThreadPersistentBase,
public LocationPolicy,
private WeaknessPolicy,
private CheckingPolicy {
public:
using typename WeaknessPolicy::IsStrongPersistent;
using PointeeType = T;
~BasicCrossThreadPersistent() {
// This implements fast path for destroying empty/sentinel.
//
// Simplified version of `AssignUnsafe()` to allow calling without a
// complete type `T`. Uses double-checked locking with a simple thread-safe
// check for a valid handle based on a node.
if (GetNodeSafe()) {
PersistentRegionLock guard;
const void* old_value = GetValue();
// The fast path check (GetNodeSafe()) does not acquire the lock. Recheck
// validity while holding the lock to ensure the reference has not been
// cleared.
if (IsValid(old_value)) {
CrossThreadPersistentRegion& region =
this->GetPersistentRegion(old_value);
region.FreeNode(GetNode());
SetNode(nullptr);
} else {
CPPGC_DCHECK(!GetNode());
}
}
// No need to call SetValue() as the handle is not used anymore. This can
// leave behind stale sentinel values but will always destroy the underlying
// node.
}
BasicCrossThreadPersistent(
const SourceLocation& loc = SourceLocation::Current())
: LocationPolicy(loc) {}
BasicCrossThreadPersistent(
std::nullptr_t, const SourceLocation& loc = SourceLocation::Current())
: LocationPolicy(loc) {}
BasicCrossThreadPersistent(
SentinelPointer s, const SourceLocation& loc = SourceLocation::Current())
: CrossThreadPersistentBase(s), LocationPolicy(loc) {}
BasicCrossThreadPersistent(
T* raw, const SourceLocation& loc = SourceLocation::Current())
: CrossThreadPersistentBase(raw), LocationPolicy(loc) {
if (!IsValid(raw)) return;
PersistentRegionLock guard;
CrossThreadPersistentRegion& region = this->GetPersistentRegion(raw);
SetNode(region.AllocateNode(this, &TraceAsRoot));
this->CheckPointer(raw);
}
class UnsafeCtorTag {
private:
UnsafeCtorTag() = default;
template <typename U, typename OtherWeaknessPolicy,
typename OtherLocationPolicy, typename OtherCheckingPolicy>
friend class BasicCrossThreadPersistent;
};
BasicCrossThreadPersistent(
UnsafeCtorTag, T* raw,
const SourceLocation& loc = SourceLocation::Current())
: CrossThreadPersistentBase(raw), LocationPolicy(loc) {
if (!IsValid(raw)) return;
CrossThreadPersistentRegion& region = this->GetPersistentRegion(raw);
SetNode(region.AllocateNode(this, &TraceAsRoot));
this->CheckPointer(raw);
}
BasicCrossThreadPersistent(
T& raw, const SourceLocation& loc = SourceLocation::Current())
: BasicCrossThreadPersistent(&raw, loc) {}
template <typename U, typename MemberBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicCrossThreadPersistent(
internal::BasicMember<U, MemberBarrierPolicy, MemberWeaknessTag,
MemberCheckingPolicy, MemberStorageType>
member,
const SourceLocation& loc = SourceLocation::Current())
: BasicCrossThreadPersistent(member.Get(), loc) {}
BasicCrossThreadPersistent(
const BasicCrossThreadPersistent& other,
const SourceLocation& loc = SourceLocation::Current())
: BasicCrossThreadPersistent(loc) {
// Invoke operator=.
*this = other;
}
// Heterogeneous ctor.
template <typename U, typename OtherWeaknessPolicy,
typename OtherLocationPolicy, typename OtherCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicCrossThreadPersistent(
const BasicCrossThreadPersistent<U, OtherWeaknessPolicy,
OtherLocationPolicy,
OtherCheckingPolicy>& other,
const SourceLocation& loc = SourceLocation::Current())
: BasicCrossThreadPersistent(loc) {
*this = other;
}
BasicCrossThreadPersistent(
BasicCrossThreadPersistent&& other,
const SourceLocation& loc = SourceLocation::Current()) noexcept {
// Invoke operator=.
*this = std::move(other);
}
BasicCrossThreadPersistent& operator=(
const BasicCrossThreadPersistent& other) {
PersistentRegionLock guard;
AssignSafe(guard, other.Get());
return *this;
}
template <typename U, typename OtherWeaknessPolicy,
typename OtherLocationPolicy, typename OtherCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicCrossThreadPersistent& operator=(
const BasicCrossThreadPersistent<U, OtherWeaknessPolicy,
OtherLocationPolicy,
OtherCheckingPolicy>& other) {
PersistentRegionLock guard;
AssignSafe(guard, other.Get());
return *this;
}
BasicCrossThreadPersistent& operator=(BasicCrossThreadPersistent&& other) {
if (this == &other) return *this;
Clear();
PersistentRegionLock guard;
PersistentBase::operator=(std::move(other));
LocationPolicy::operator=(std::move(other));
if (!IsValid(GetValue())) return *this;
GetNode()->UpdateOwner(this);
other.SetValue(nullptr);
other.SetNode(nullptr);
this->CheckPointer(Get());
return *this;
}
/**
* Assigns a raw pointer.
*
* Note: **Not thread-safe.**
*/
BasicCrossThreadPersistent& operator=(T* other) {
AssignUnsafe(other);
return *this;
}
// Assignment from member.
template <typename U, typename MemberBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicCrossThreadPersistent& operator=(
internal::BasicMember<U, MemberBarrierPolicy, MemberWeaknessTag,
MemberCheckingPolicy, MemberStorageType>
member) {
return operator=(member.Get());
}
/**
* Assigns a nullptr.
*
* \returns the handle.
*/
BasicCrossThreadPersistent& operator=(std::nullptr_t) {
Clear();
return *this;
}
/**
* Assigns the sentinel pointer.
*
* \returns the handle.
*/
BasicCrossThreadPersistent& operator=(SentinelPointer s) {
PersistentRegionLock guard;
AssignSafe(guard, s);
return *this;
}
/**
* Returns a pointer to the stored object.
*
* Note: **Not thread-safe.**
*
* \returns a pointer to the stored object.
*/
// CFI cast exemption to allow passing SentinelPointer through T* and support
// heterogeneous assignments between different Member and Persistent handles
// based on their actual types.
V8_CLANG_NO_SANITIZE("cfi-unrelated-cast") T* Get() const {
return static_cast<T*>(const_cast<void*>(GetValue()));
}
/**
* Clears the stored object.
*/
void Clear() {
PersistentRegionLock guard;
AssignSafe(guard, nullptr);
}
/**
* Returns a pointer to the stored object and releases it.
*
* Note: **Not thread-safe.**
*
* \returns a pointer to the stored object.
*/
T* Release() {
T* result = Get();
Clear();
return result;
}
/**
* Conversio to boolean.
*
* Note: **Not thread-safe.**
*
* \returns true if an actual object has been stored and false otherwise.
*/
explicit operator bool() const { return Get(); }
/**
* Conversion to object of type T.
*
* Note: **Not thread-safe.**
*
* \returns the object.
*/
operator T*() const { return Get(); }
/**
* Dereferences the stored object.
*
* Note: **Not thread-safe.**
*/
T* operator->() const { return Get(); }
T& operator*() const { return *Get(); }
template <typename U, typename OtherWeaknessPolicy = WeaknessPolicy,
typename OtherLocationPolicy = LocationPolicy,
typename OtherCheckingPolicy = CheckingPolicy>
BasicCrossThreadPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>
To() const {
using OtherBasicCrossThreadPersistent =
BasicCrossThreadPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>;
PersistentRegionLock guard;
return OtherBasicCrossThreadPersistent(
typename OtherBasicCrossThreadPersistent::UnsafeCtorTag(),
static_cast<U*>(Get()));
}
template <typename U = T,
typename = typename std::enable_if<!BasicCrossThreadPersistent<
U, WeaknessPolicy>::IsStrongPersistent::value>::type>
BasicCrossThreadPersistent<U, internal::StrongCrossThreadPersistentPolicy>
Lock() const {
return BasicCrossThreadPersistent<
U, internal::StrongCrossThreadPersistentPolicy>(*this);
}
private:
static bool IsValid(const void* ptr) {
return ptr && ptr != kSentinelPointer;
}
static void TraceAsRoot(RootVisitor& root_visitor, const void* ptr) {
root_visitor.Trace(*static_cast<const BasicCrossThreadPersistent*>(ptr));
}
void AssignUnsafe(T* ptr) {
const void* old_value = GetValue();
if (IsValid(old_value)) {
PersistentRegionLock guard;
old_value = GetValue();
// The fast path check (IsValid()) does not acquire the lock. Reload
// the value to ensure the reference has not been cleared.
if (IsValid(old_value)) {
CrossThreadPersistentRegion& region =
this->GetPersistentRegion(old_value);
if (IsValid(ptr) && (&region == &this->GetPersistentRegion(ptr))) {
SetValue(ptr);
this->CheckPointer(ptr);
return;
}
region.FreeNode(GetNode());
SetNode(nullptr);
} else {
CPPGC_DCHECK(!GetNode());
}
}
SetValue(ptr);
if (!IsValid(ptr)) return;
PersistentRegionLock guard;
SetNode(this->GetPersistentRegion(ptr).AllocateNode(this, &TraceAsRoot));
this->CheckPointer(ptr);
}
void AssignSafe(PersistentRegionLock&, T* ptr) {
PersistentRegionLock::AssertLocked();
const void* old_value = GetValue();
if (IsValid(old_value)) {
CrossThreadPersistentRegion& region =
this->GetPersistentRegion(old_value);
if (IsValid(ptr) && (&region == &this->GetPersistentRegion(ptr))) {
SetValue(ptr);
this->CheckPointer(ptr);
return;
}
region.FreeNode(GetNode());
SetNode(nullptr);
}
SetValue(ptr);
if (!IsValid(ptr)) return;
SetNode(this->GetPersistentRegion(ptr).AllocateNode(this, &TraceAsRoot));
this->CheckPointer(ptr);
}
void ClearFromGC() const {
if (IsValid(GetValueFromGC())) {
WeaknessPolicy::GetPersistentRegion(GetValueFromGC())
.FreeNode(GetNodeFromGC());
CrossThreadPersistentBase::ClearFromGC();
}
}
// See Get() for details.
V8_CLANG_NO_SANITIZE("cfi-unrelated-cast")
T* GetFromGC() const {
return static_cast<T*>(const_cast<void*>(GetValueFromGC()));
}
friend class internal::RootVisitor;
};
template <typename T, typename LocationPolicy, typename CheckingPolicy>
struct IsWeak<
BasicCrossThreadPersistent<T, internal::WeakCrossThreadPersistentPolicy,
LocationPolicy, CheckingPolicy>>
: std::true_type {};
} // namespace internal
namespace subtle {
/**
* **DO NOT USE: Has known caveats, see below.**
*
* CrossThreadPersistent allows retaining objects from threads other than the
* thread the owning heap is operating on.
*
* Known caveats:
* - Does not protect the heap owning an object from terminating.
* - Reaching transitively through the graph is unsupported as objects may be
* moved concurrently on the thread owning the object.
*/
template <typename T>
using CrossThreadPersistent = internal::BasicCrossThreadPersistent<
T, internal::StrongCrossThreadPersistentPolicy>;
/**
* **DO NOT USE: Has known caveats, see below.**
*
* CrossThreadPersistent allows weakly retaining objects from threads other than
* the thread the owning heap is operating on.
*
* Known caveats:
* - Does not protect the heap owning an object from terminating.
* - Reaching transitively through the graph is unsupported as objects may be
* moved concurrently on the thread owning the object.
*/
template <typename T>
using WeakCrossThreadPersistent = internal::BasicCrossThreadPersistent<
T, internal::WeakCrossThreadPersistentPolicy>;
} // namespace subtle
} // namespace cppgc
#endif // INCLUDE_CPPGC_CROSS_THREAD_PERSISTENT_H_

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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_CUSTOM_SPACE_H_
#define INCLUDE_CPPGC_CUSTOM_SPACE_H_
#include <stddef.h>
namespace cppgc {
/**
* Index identifying a custom space.
*/
struct CustomSpaceIndex {
constexpr CustomSpaceIndex(size_t value) : value(value) {} // NOLINT
size_t value;
};
/**
* Top-level base class for custom spaces. Users must inherit from CustomSpace
* below.
*/
class CustomSpaceBase {
public:
virtual ~CustomSpaceBase() = default;
virtual CustomSpaceIndex GetCustomSpaceIndex() const = 0;
virtual bool IsCompactable() const = 0;
};
/**
* Base class custom spaces should directly inherit from. The class inheriting
* from `CustomSpace` must define `kSpaceIndex` as unique space index. These
* indices need for form a sequence starting at 0.
*
* Example:
* \code
* class CustomSpace1 : public CustomSpace<CustomSpace1> {
* public:
* static constexpr CustomSpaceIndex kSpaceIndex = 0;
* };
* class CustomSpace2 : public CustomSpace<CustomSpace2> {
* public:
* static constexpr CustomSpaceIndex kSpaceIndex = 1;
* };
* \endcode
*/
template <typename ConcreteCustomSpace>
class CustomSpace : public CustomSpaceBase {
public:
/**
* Compaction is only supported on spaces that manually manage slots
* recording.
*/
static constexpr bool kSupportsCompaction = false;
CustomSpaceIndex GetCustomSpaceIndex() const final {
return ConcreteCustomSpace::kSpaceIndex;
}
bool IsCompactable() const final {
return ConcreteCustomSpace::kSupportsCompaction;
}
};
/**
* User-overridable trait that allows pinning types to custom spaces.
*/
template <typename T, typename = void>
struct SpaceTrait {
using Space = void;
};
namespace internal {
template <typename CustomSpace>
struct IsAllocatedOnCompactableSpaceImpl {
static constexpr bool value = CustomSpace::kSupportsCompaction;
};
template <>
struct IsAllocatedOnCompactableSpaceImpl<void> {
// Non-custom spaces are by default not compactable.
static constexpr bool value = false;
};
template <typename T>
struct IsAllocatedOnCompactableSpace {
public:
static constexpr bool value =
IsAllocatedOnCompactableSpaceImpl<typename SpaceTrait<T>::Space>::value;
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_CUSTOM_SPACE_H_

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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_DEFAULT_PLATFORM_H_
#define INCLUDE_CPPGC_DEFAULT_PLATFORM_H_
#include <memory>
#include "cppgc/platform.h"
#include "libplatform/libplatform.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
/**
* Platform provided by cppgc. Uses V8's DefaultPlatform provided by
* libplatform internally. Exception: `GetForegroundTaskRunner()`, see below.
*/
class V8_EXPORT DefaultPlatform : public Platform {
public:
using IdleTaskSupport = v8::platform::IdleTaskSupport;
explicit DefaultPlatform(
int thread_pool_size = 0,
IdleTaskSupport idle_task_support = IdleTaskSupport::kDisabled,
std::unique_ptr<TracingController> tracing_controller = {})
: v8_platform_(v8::platform::NewDefaultPlatform(
thread_pool_size, idle_task_support,
v8::platform::InProcessStackDumping::kDisabled,
std::move(tracing_controller))) {}
cppgc::PageAllocator* GetPageAllocator() override {
return v8_platform_->GetPageAllocator();
}
double MonotonicallyIncreasingTime() override {
return v8_platform_->MonotonicallyIncreasingTime();
}
std::shared_ptr<cppgc::TaskRunner> GetForegroundTaskRunner() override {
// V8's default platform creates a new task runner when passed the
// `v8::Isolate` pointer the first time. For non-default platforms this will
// require getting the appropriate task runner.
return v8_platform_->GetForegroundTaskRunner(kNoIsolate);
}
std::unique_ptr<cppgc::JobHandle> PostJob(
cppgc::TaskPriority priority,
std::unique_ptr<cppgc::JobTask> job_task) override {
return v8_platform_->PostJob(priority, std::move(job_task));
}
TracingController* GetTracingController() override {
return v8_platform_->GetTracingController();
}
v8::Platform* GetV8Platform() const { return v8_platform_.get(); }
protected:
static constexpr v8::Isolate* kNoIsolate = nullptr;
std::unique_ptr<v8::Platform> v8_platform_;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_DEFAULT_PLATFORM_H_

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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_EPHEMERON_PAIR_H_
#define INCLUDE_CPPGC_EPHEMERON_PAIR_H_
#include "cppgc/liveness-broker.h"
#include "cppgc/member.h"
namespace cppgc {
/**
* An ephemeron pair is used to conditionally retain an object.
* The `value` will be kept alive only if the `key` is alive.
*/
template <typename K, typename V>
struct EphemeronPair {
EphemeronPair(K* k, V* v) : key(k), value(v) {}
WeakMember<K> key;
Member<V> value;
void ClearValueIfKeyIsDead(const LivenessBroker& broker) {
if (!broker.IsHeapObjectAlive(key)) value = nullptr;
}
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_EPHEMERON_PAIR_H_

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// Copyright 2021 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_EXPLICIT_MANAGEMENT_H_
#define INCLUDE_CPPGC_EXPLICIT_MANAGEMENT_H_
#include <cstddef>
#include "cppgc/allocation.h"
#include "cppgc/internal/logging.h"
#include "cppgc/type-traits.h"
namespace cppgc {
class HeapHandle;
namespace subtle {
template <typename T>
void FreeUnreferencedObject(HeapHandle& heap_handle, T& object);
template <typename T>
bool Resize(T& object, AdditionalBytes additional_bytes);
} // namespace subtle
namespace internal {
class ExplicitManagementImpl final {
private:
V8_EXPORT static void FreeUnreferencedObject(HeapHandle&, void*);
V8_EXPORT static bool Resize(void*, size_t);
template <typename T>
friend void subtle::FreeUnreferencedObject(HeapHandle&, T&);
template <typename T>
friend bool subtle::Resize(T&, AdditionalBytes);
};
} // namespace internal
namespace subtle {
/**
* Informs the garbage collector that `object` can be immediately reclaimed. The
* destructor may not be invoked immediately but only on next garbage
* collection.
*
* It is up to the embedder to guarantee that no other object holds a reference
* to `object` after calling `FreeUnreferencedObject()`. In case such a
* reference exists, it's use results in a use-after-free.
*
* To aid in using the API, `FreeUnreferencedObject()` may be called from
* destructors on objects that would be reclaimed in the same garbage collection
* cycle.
*
* \param heap_handle The corresponding heap.
* \param object Reference to an object that is of type `GarbageCollected` and
* should be immediately reclaimed.
*/
template <typename T>
void FreeUnreferencedObject(HeapHandle& heap_handle, T& object) {
static_assert(IsGarbageCollectedTypeV<T>,
"Object must be of type GarbageCollected.");
internal::ExplicitManagementImpl::FreeUnreferencedObject(heap_handle,
&object);
}
/**
* Tries to resize `object` of type `T` with additional bytes on top of
* sizeof(T). Resizing is only useful with trailing inlined storage, see e.g.
* `MakeGarbageCollected(AllocationHandle&, AdditionalBytes)`.
*
* `Resize()` performs growing or shrinking as needed and may skip the operation
* for internal reasons, see return value.
*
* It is up to the embedder to guarantee that in case of shrinking a larger
* object down, the reclaimed area is not used anymore. Any subsequent use
* results in a use-after-free.
*
* The `object` must be live when calling `Resize()`.
*
* \param object Reference to an object that is of type `GarbageCollected` and
* should be resized.
* \param additional_bytes Bytes in addition to sizeof(T) that the object should
* provide.
* \returns true when the operation was successful and the result can be relied
* on, and false otherwise.
*/
template <typename T>
bool Resize(T& object, AdditionalBytes additional_bytes) {
static_assert(IsGarbageCollectedTypeV<T>,
"Object must be of type GarbageCollected.");
return internal::ExplicitManagementImpl::Resize(
&object, sizeof(T) + additional_bytes.value);
}
} // namespace subtle
} // namespace cppgc
#endif // INCLUDE_CPPGC_EXPLICIT_MANAGEMENT_H_

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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_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;
/**
* 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_

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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_HEAP_CONSISTENCY_H_
#define INCLUDE_CPPGC_HEAP_CONSISTENCY_H_
#include <cstddef>
#include "cppgc/internal/write-barrier.h"
#include "cppgc/macros.h"
#include "cppgc/member.h"
#include "cppgc/trace-trait.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
class HeapHandle;
namespace subtle {
/**
* **DO NOT USE: Use the appropriate managed types.**
*
* Consistency helpers that aid in maintaining a consistent internal state of
* the garbage collector.
*/
class HeapConsistency final {
public:
using WriteBarrierParams = internal::WriteBarrier::Params;
using WriteBarrierType = internal::WriteBarrier::Type;
/**
* Gets the required write barrier type for a specific write.
*
* \param slot Slot containing the pointer to the object. The slot itself
* must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
* \param value The pointer to the object. May be an interior pointer to an
* interface of the actual object.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
static V8_INLINE WriteBarrierType GetWriteBarrierType(
const void* slot, const void* value, WriteBarrierParams& params) {
return internal::WriteBarrier::GetWriteBarrierType(slot, value, params);
}
/**
* Gets the required write barrier type for a specific write. This override is
* only used for all the BasicMember types.
*
* \param slot Slot containing the pointer to the object. The slot itself
* must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
* \param value The pointer to the object held via `BasicMember`.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
static V8_INLINE WriteBarrierType GetWriteBarrierType(
const internal::BasicMember<T, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& value,
WriteBarrierParams& params) {
return internal::WriteBarrier::GetWriteBarrierType(
value.GetRawSlot(), value.GetRawStorage(), params);
}
/**
* Gets the required write barrier type for a specific write.
*
* \param slot Slot to some part of an object. The object must not necessarily
have been allocated using `MakeGarbageCollected()` but can also live
off-heap or on stack.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \param callback Callback returning the corresponding heap handle. The
* callback is only invoked if the heap cannot otherwise be figured out. The
* callback must not allocate.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrierType
GetWriteBarrierType(const void* slot, WriteBarrierParams& params,
HeapHandleCallback callback) {
return internal::WriteBarrier::GetWriteBarrierType(slot, params, callback);
}
/**
* Gets the required write barrier type for a specific write.
* This version is meant to be used in conjunction with with a marking write
* barrier barrier which doesn't consider the slot.
*
* \param value The pointer to the object. May be an interior pointer to an
* interface of the actual object.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
static V8_INLINE WriteBarrierType
GetWriteBarrierType(const void* value, WriteBarrierParams& params) {
return internal::WriteBarrier::GetWriteBarrierType(value, params);
}
/**
* Conservative Dijkstra-style write barrier that processes an object if it
* has not yet been processed.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param object The pointer to the object. May be an interior pointer to a
* an interface of the actual object.
*/
static V8_INLINE void DijkstraWriteBarrier(const WriteBarrierParams& params,
const void* object) {
internal::WriteBarrier::DijkstraMarkingBarrier(params, object);
}
/**
* Conservative Dijkstra-style write barrier that processes a range of
* elements if they have not yet been processed.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param first_element Pointer to the first element that should be processed.
* The slot itself must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
* \param element_size Size of the element in bytes.
* \param number_of_elements Number of elements that should be processed,
* starting with `first_element`.
* \param trace_callback The trace callback that should be invoked for each
* element if necessary.
*/
static V8_INLINE void DijkstraWriteBarrierRange(
const WriteBarrierParams& params, const void* first_element,
size_t element_size, size_t number_of_elements,
TraceCallback trace_callback) {
internal::WriteBarrier::DijkstraMarkingBarrierRange(
params, first_element, element_size, number_of_elements,
trace_callback);
}
/**
* Steele-style write barrier that re-processes an object if it has already
* been processed.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param object The pointer to the object which must point to an object that
* has been allocated using `MakeGarbageCollected()`. Interior pointers are
* not supported.
*/
static V8_INLINE void SteeleWriteBarrier(const WriteBarrierParams& params,
const void* object) {
internal::WriteBarrier::SteeleMarkingBarrier(params, object);
}
/**
* Generational barrier for maintaining consistency when running with multiple
* generations.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param slot Slot containing the pointer to the object. The slot itself
* must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
*/
static V8_INLINE void GenerationalBarrier(const WriteBarrierParams& params,
const void* slot) {
internal::WriteBarrier::GenerationalBarrier<
internal::WriteBarrier::GenerationalBarrierType::kPreciseSlot>(params,
slot);
}
/**
* Generational barrier for maintaining consistency when running with multiple
* generations. This version is used when slot contains uncompressed pointer.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param slot Uncompressed slot containing the direct pointer to the object.
* The slot itself must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
*/
static V8_INLINE void GenerationalBarrierForUncompressedSlot(
const WriteBarrierParams& params, const void* uncompressed_slot) {
internal::WriteBarrier::GenerationalBarrier<
internal::WriteBarrier::GenerationalBarrierType::
kPreciseUncompressedSlot>(params, uncompressed_slot);
}
/**
* Generational barrier for source object that may contain outgoing pointers
* to objects in young generation.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param inner_pointer Pointer to the source object.
*/
static V8_INLINE void GenerationalBarrierForSourceObject(
const WriteBarrierParams& params, const void* inner_pointer) {
internal::WriteBarrier::GenerationalBarrier<
internal::WriteBarrier::GenerationalBarrierType::kImpreciseSlot>(
params, inner_pointer);
}
private:
HeapConsistency() = delete;
};
/**
* Disallows garbage collection finalizations. Any garbage collection triggers
* result in a crash when in this scope.
*
* Note that the garbage collector already covers paths that can lead to garbage
* collections, so user code does not require checking
* `IsGarbageCollectionAllowed()` before allocations.
*/
class V8_EXPORT V8_NODISCARD DisallowGarbageCollectionScope final {
CPPGC_STACK_ALLOCATED();
public:
/**
* \returns whether garbage collections are currently allowed.
*/
static bool IsGarbageCollectionAllowed(HeapHandle& heap_handle);
/**
* Enters a disallow garbage collection scope. Must be paired with `Leave()`.
* Prefer a scope instance of `DisallowGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Enter(HeapHandle& heap_handle);
/**
* Leaves a disallow garbage collection scope. Must be paired with `Enter()`.
* Prefer a scope instance of `DisallowGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Leave(HeapHandle& heap_handle);
/**
* Constructs a scoped object that automatically enters and leaves a disallow
* garbage collection scope based on its lifetime.
*
* \param heap_handle The corresponding heap.
*/
explicit DisallowGarbageCollectionScope(HeapHandle& heap_handle);
~DisallowGarbageCollectionScope();
DisallowGarbageCollectionScope(const DisallowGarbageCollectionScope&) =
delete;
DisallowGarbageCollectionScope& operator=(
const DisallowGarbageCollectionScope&) = delete;
private:
HeapHandle& heap_handle_;
};
/**
* Avoids invoking garbage collection finalizations. Already running garbage
* collection phase are unaffected by this scope.
*
* Should only be used temporarily as the scope has an impact on memory usage
* and follow up garbage collections.
*/
class V8_EXPORT V8_NODISCARD NoGarbageCollectionScope final {
CPPGC_STACK_ALLOCATED();
public:
/**
* Enters a no garbage collection scope. Must be paired with `Leave()`. Prefer
* a scope instance of `NoGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Enter(HeapHandle& heap_handle);
/**
* Leaves a no garbage collection scope. Must be paired with `Enter()`. Prefer
* a scope instance of `NoGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Leave(HeapHandle& heap_handle);
/**
* Constructs a scoped object that automatically enters and leaves a no
* garbage collection scope based on its lifetime.
*
* \param heap_handle The corresponding heap.
*/
explicit NoGarbageCollectionScope(HeapHandle& heap_handle);
~NoGarbageCollectionScope();
NoGarbageCollectionScope(const NoGarbageCollectionScope&) = delete;
NoGarbageCollectionScope& operator=(const NoGarbageCollectionScope&) = delete;
private:
HeapHandle& heap_handle_;
};
} // namespace subtle
} // namespace cppgc
#endif // INCLUDE_CPPGC_HEAP_CONSISTENCY_H_

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// Copyright 2022 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_HEAP_HANDLE_H_
#define INCLUDE_CPPGC_HEAP_HANDLE_H_
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
class HeapBase;
class WriteBarrierTypeForCagedHeapPolicy;
class WriteBarrierTypeForNonCagedHeapPolicy;
} // namespace internal
/**
* Opaque handle used for additional heap APIs.
*/
class HeapHandle {
public:
// Deleted copy ctor to avoid treating the type by value.
HeapHandle(const HeapHandle&) = delete;
HeapHandle& operator=(const HeapHandle&) = delete;
private:
HeapHandle() = default;
V8_INLINE bool is_incremental_marking_in_progress() const {
return is_incremental_marking_in_progress_;
}
V8_INLINE bool is_young_generation_enabled() const {
return is_young_generation_enabled_;
}
bool is_incremental_marking_in_progress_ = false;
bool is_young_generation_enabled_ = false;
friend class internal::HeapBase;
friend class internal::WriteBarrierTypeForCagedHeapPolicy;
friend class internal::WriteBarrierTypeForNonCagedHeapPolicy;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_HEAP_HANDLE_H_

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// Copyright 2021 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_HEAP_STATE_H_
#define INCLUDE_CPPGC_HEAP_STATE_H_
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
class HeapHandle;
namespace subtle {
/**
* Helpers to peek into heap-internal state.
*/
class V8_EXPORT HeapState final {
public:
/**
* Returns whether the garbage collector is marking. This API is experimental
* and is expected to be removed in future.
*
* \param heap_handle The corresponding heap.
* \returns true if the garbage collector is currently marking, and false
* otherwise.
*/
static bool IsMarking(const HeapHandle& heap_handle);
/*
* Returns whether the garbage collector is sweeping. This API is experimental
* and is expected to be removed in future.
*
* \param heap_handle The corresponding heap.
* \returns true if the garbage collector is currently sweeping, and false
* otherwise.
*/
static bool IsSweeping(const HeapHandle& heap_handle);
/*
* Returns whether the garbage collector is currently sweeping on the thread
* owning this heap. This API allows the caller to determine whether it has
* been called from a destructor of a managed object. This API is experimental
* and may be removed in future.
*
* \param heap_handle The corresponding heap.
* \returns true if the garbage collector is currently sweeping on this
* thread, and false otherwise.
*/
static bool IsSweepingOnOwningThread(const HeapHandle& heap_handle);
/**
* Returns whether the garbage collector is in the atomic pause, i.e., the
* mutator is stopped from running. This API is experimental and is expected
* to be removed in future.
*
* \param heap_handle The corresponding heap.
* \returns true if the garbage collector is currently in the atomic pause,
* and false otherwise.
*/
static bool IsInAtomicPause(const HeapHandle& heap_handle);
/**
* Returns whether the last garbage collection was finalized conservatively
* (i.e., with a non-empty stack). This API is experimental and is expected to
* be removed in future.
*
* \param heap_handle The corresponding heap.
* \returns true if the last garbage collection was finalized conservatively,
* and false otherwise.
*/
static bool PreviousGCWasConservative(const HeapHandle& heap_handle);
private:
HeapState() = delete;
};
} // namespace subtle
} // namespace cppgc
#endif // INCLUDE_CPPGC_HEAP_STATE_H_

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// Copyright 2021 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_HEAP_STATISTICS_H_
#define INCLUDE_CPPGC_HEAP_STATISTICS_H_
#include <cstddef>
#include <cstdint>
#include <string>
#include <vector>
namespace cppgc {
/**
* `HeapStatistics` contains memory consumption and utilization statistics for a
* cppgc heap.
*/
struct HeapStatistics final {
/**
* Specifies the detail level of the heap statistics. Brief statistics contain
* only the top-level allocated and used memory statistics for the entire
* heap. Detailed statistics also contain a break down per space and page, as
* well as freelist statistics and object type histograms. Note that used
* memory reported by brief statistics and detailed statistics might differ
* slightly.
*/
enum DetailLevel : uint8_t {
kBrief,
kDetailed,
};
/**
* Object statistics for a single type.
*/
struct ObjectStatsEntry {
/**
* Number of allocated bytes.
*/
size_t allocated_bytes;
/**
* Number of allocated objects.
*/
size_t object_count;
};
/**
* Page granularity statistics. For each page the statistics record the
* allocated memory size and overall used memory size for the page.
*/
struct PageStatistics {
/** Overall committed amount of memory for the page. */
size_t committed_size_bytes = 0;
/** Resident amount of memory held by the page. */
size_t resident_size_bytes = 0;
/** Amount of memory actually used on the page. */
size_t used_size_bytes = 0;
/** Statistics for object allocated on the page. Filled only when
* NameProvider::SupportsCppClassNamesAsObjectNames() is true. */
std::vector<ObjectStatsEntry> object_statistics;
};
/**
* Statistics of the freelist (used only in non-large object spaces). For
* each bucket in the freelist the statistics record the bucket size, the
* number of freelist entries in the bucket, and the overall allocated memory
* consumed by these freelist entries.
*/
struct FreeListStatistics {
/** bucket sizes in the freelist. */
std::vector<size_t> bucket_size;
/** number of freelist entries per bucket. */
std::vector<size_t> free_count;
/** memory size consumed by freelist entries per size. */
std::vector<size_t> free_size;
};
/**
* Space granularity statistics. For each space the statistics record the
* space name, the amount of allocated memory and overall used memory for the
* space. The statistics also contain statistics for each of the space's
* pages, its freelist and the objects allocated on the space.
*/
struct SpaceStatistics {
/** The space name */
std::string name;
/** Overall committed amount of memory for the heap. */
size_t committed_size_bytes = 0;
/** Resident amount of memory held by the heap. */
size_t resident_size_bytes = 0;
/** Amount of memory actually used on the space. */
size_t used_size_bytes = 0;
/** Statistics for each of the pages in the space. */
std::vector<PageStatistics> page_stats;
/** Statistics for the freelist of the space. */
FreeListStatistics free_list_stats;
};
/** Overall committed amount of memory for the heap. */
size_t committed_size_bytes = 0;
/** Resident amount of memory held by the heap. */
size_t resident_size_bytes = 0;
/** Amount of memory actually used on the heap. */
size_t used_size_bytes = 0;
/** Detail level of this HeapStatistics. */
DetailLevel detail_level;
/** Statistics for each of the spaces in the heap. Filled only when
* `detail_level` is `DetailLevel::kDetailed`. */
std::vector<SpaceStatistics> space_stats;
/**
* Vector of `cppgc::GarbageCollected` type names.
*/
std::vector<std::string> type_names;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_HEAP_STATISTICS_H_

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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_HEAP_H_
#define INCLUDE_CPPGC_HEAP_H_
#include <cstddef>
#include <cstdint>
#include <memory>
#include <vector>
#include "cppgc/common.h"
#include "cppgc/custom-space.h"
#include "cppgc/platform.h"
#include "v8config.h" // NOLINT(build/include_directory)
/**
* cppgc - A C++ garbage collection library.
*/
namespace cppgc {
class AllocationHandle;
class HeapHandle;
/**
* Implementation details of cppgc. Those details are considered internal and
* may change at any point in time without notice. Users should never rely on
* the contents of this namespace.
*/
namespace internal {
class Heap;
} // namespace internal
class V8_EXPORT Heap {
public:
/**
* Specifies the stack state the embedder is in.
*/
using StackState = EmbedderStackState;
/**
* Specifies whether conservative stack scanning is supported.
*/
enum class StackSupport : uint8_t {
/**
* Conservative stack scan is supported.
*/
kSupportsConservativeStackScan,
/**
* Conservative stack scan is not supported. Embedders may use this option
* when using custom infrastructure that is unsupported by the library.
*/
kNoConservativeStackScan,
};
/**
* Specifies supported marking types.
*/
enum class MarkingType : uint8_t {
/**
* Atomic stop-the-world marking. This option does not require any write
* barriers but is the most intrusive in terms of jank.
*/
kAtomic,
/**
* Incremental marking interleaves marking with the rest of the application
* workload on the same thread.
*/
kIncremental,
/**
* Incremental and concurrent marking.
*/
kIncrementalAndConcurrent
};
/**
* Specifies supported sweeping types.
*/
enum class SweepingType : uint8_t {
/**
* Atomic stop-the-world sweeping. All of sweeping is performed at once.
*/
kAtomic,
/**
* Incremental sweeping interleaves sweeping with the rest of the
* application workload on the same thread.
*/
kIncremental,
/**
* Incremental and concurrent sweeping. Sweeping is split and interleaved
* with the rest of the application.
*/
kIncrementalAndConcurrent
};
/**
* Constraints for a Heap setup.
*/
struct ResourceConstraints {
/**
* Allows the heap to grow to some initial size in bytes before triggering
* garbage collections. This is useful when it is known that applications
* need a certain minimum heap to run to avoid repeatedly invoking the
* garbage collector when growing the heap.
*/
size_t initial_heap_size_bytes = 0;
};
/**
* Options specifying Heap properties (e.g. custom spaces) when initializing a
* heap through `Heap::Create()`.
*/
struct HeapOptions {
/**
* Creates reasonable defaults for instantiating a Heap.
*
* \returns the HeapOptions that can be passed to `Heap::Create()`.
*/
static HeapOptions Default() { return {}; }
/**
* Custom spaces added to heap are required to have indices forming a
* numbered sequence starting at 0, i.e., their `kSpaceIndex` must
* correspond to the index they reside in the vector.
*/
std::vector<std::unique_ptr<CustomSpaceBase>> custom_spaces;
/**
* Specifies whether conservative stack scan is supported. When conservative
* stack scan is not supported, the collector may try to invoke
* garbage collections using non-nestable task, which are guaranteed to have
* no interesting stack, through the provided Platform. If such tasks are
* not supported by the Platform, the embedder must take care of invoking
* the GC through `ForceGarbageCollectionSlow()`.
*/
StackSupport stack_support = StackSupport::kSupportsConservativeStackScan;
/**
* Specifies which types of marking are supported by the heap.
*/
MarkingType marking_support = MarkingType::kIncrementalAndConcurrent;
/**
* Specifies which types of sweeping are supported by the heap.
*/
SweepingType sweeping_support = SweepingType::kIncrementalAndConcurrent;
/**
* Resource constraints specifying various properties that the internal
* GC scheduler follows.
*/
ResourceConstraints resource_constraints;
};
/**
* Creates a new heap that can be used for object allocation.
*
* \param platform implemented and provided by the embedder.
* \param options HeapOptions specifying various properties for the Heap.
* \returns a new Heap instance.
*/
static std::unique_ptr<Heap> Create(
std::shared_ptr<Platform> platform,
HeapOptions options = HeapOptions::Default());
virtual ~Heap() = default;
/**
* Forces garbage collection.
*
* \param source String specifying the source (or caller) triggering a
* forced garbage collection.
* \param reason String specifying the reason for the forced garbage
* collection.
* \param stack_state The embedder stack state, see StackState.
*/
void ForceGarbageCollectionSlow(
const char* source, const char* reason,
StackState stack_state = StackState::kMayContainHeapPointers);
/**
* \returns the opaque handle for allocating objects using
* `MakeGarbageCollected()`.
*/
AllocationHandle& GetAllocationHandle();
/**
* \returns the opaque heap handle which may be used to refer to this heap in
* other APIs. Valid as long as the underlying `Heap` is alive.
*/
HeapHandle& GetHeapHandle();
private:
Heap() = default;
friend class internal::Heap;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_HEAP_H_

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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_API_CONSTANTS_H_
#define INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_
#include <cstddef>
#include <cstdint>
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
// Embedders should not rely on this code!
// Internal constants to avoid exposing internal types on the API surface.
namespace api_constants {
constexpr size_t kKB = 1024;
constexpr size_t kMB = kKB * 1024;
constexpr size_t kGB = kMB * 1024;
// Offset of the uint16_t bitfield from the payload contaning the
// in-construction bit. This is subtracted from the payload pointer to get
// to the right bitfield.
static constexpr size_t kFullyConstructedBitFieldOffsetFromPayload =
2 * sizeof(uint16_t);
// Mask for in-construction bit.
static constexpr uint16_t kFullyConstructedBitMask = uint16_t{1};
static constexpr size_t kPageSize = size_t{1} << 17;
#if defined(V8_TARGET_ARCH_ARM64) && defined(V8_OS_DARWIN)
constexpr size_t kGuardPageSize = 0;
#else
constexpr size_t kGuardPageSize = 4096;
#endif
static constexpr size_t kLargeObjectSizeThreshold = kPageSize / 2;
#if defined(CPPGC_CAGED_HEAP)
#if defined(CPPGC_2GB_CAGE)
constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(2) * kGB;
#else // !defined(CPPGC_2GB_CAGE)
constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(4) * kGB;
#endif // !defined(CPPGC_2GB_CAGE)
constexpr size_t kCagedHeapReservationAlignment = kCagedHeapReservationSize;
#endif // defined(CPPGC_CAGED_HEAP)
static constexpr size_t kDefaultAlignment = sizeof(void*);
// Maximum support alignment for a type as in `alignof(T)`.
static constexpr size_t kMaxSupportedAlignment = 2 * kDefaultAlignment;
// Granularity of heap allocations.
constexpr size_t kAllocationGranularity = sizeof(void*);
// Default cacheline size.
constexpr size_t kCachelineSize = 64;
} // namespace api_constants
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_

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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_ATOMIC_ENTRY_FLAG_H_
#define INCLUDE_CPPGC_INTERNAL_ATOMIC_ENTRY_FLAG_H_
#include <atomic>
namespace cppgc {
namespace internal {
// A flag which provides a fast check whether a scope may be entered on the
// current thread, without needing to access thread-local storage or mutex. Can
// have false positives (i.e., spuriously report that it might be entered), so
// it is expected that this will be used in tandem with a precise check that the
// scope is in fact entered on that thread.
//
// Example:
// g_frobnicating_flag.MightBeEntered() &&
// ThreadLocalFrobnicator().IsFrobnicating()
//
// Relaxed atomic operations are sufficient, since:
// - all accesses remain atomic
// - each thread must observe its own operations in order
// - no thread ever exits the flag more times than it enters (if used correctly)
// And so if a thread observes zero, it must be because it has observed an equal
// number of exits as entries.
class AtomicEntryFlag final {
public:
void Enter() { entries_.fetch_add(1, std::memory_order_relaxed); }
void Exit() { entries_.fetch_sub(1, std::memory_order_relaxed); }
// Returns false only if the current thread is not between a call to Enter
// and a call to Exit. Returns true if this thread or another thread may
// currently be in the scope guarded by this flag.
bool MightBeEntered() const {
return entries_.load(std::memory_order_relaxed) != 0;
}
private:
std::atomic_int entries_{0};
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_ATOMIC_ENTRY_FLAG_H_

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// Copyright 2022 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_BASE_PAGE_HANDLE_H_
#define INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_
#include "cppgc/heap-handle.h"
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/logging.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
// The class is needed in the header to allow for fast access to HeapHandle in
// the write barrier.
class BasePageHandle {
public:
static V8_INLINE BasePageHandle* FromPayload(void* payload) {
return reinterpret_cast<BasePageHandle*>(
(reinterpret_cast<uintptr_t>(payload) &
~(api_constants::kPageSize - 1)) +
api_constants::kGuardPageSize);
}
static V8_INLINE const BasePageHandle* FromPayload(const void* payload) {
return FromPayload(const_cast<void*>(payload));
}
HeapHandle& heap_handle() { return heap_handle_; }
const HeapHandle& heap_handle() const { return heap_handle_; }
protected:
explicit BasePageHandle(HeapHandle& heap_handle) : heap_handle_(heap_handle) {
CPPGC_DCHECK(reinterpret_cast<uintptr_t>(this) % api_constants::kPageSize ==
api_constants::kGuardPageSize);
}
HeapHandle& heap_handle_;
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_

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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_CAGED_HEAP_LOCAL_DATA_H_
#define INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_
#include <array>
#include <cstddef>
#include <cstdint>
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/caged-heap.h"
#include "cppgc/internal/logging.h"
#include "cppgc/platform.h"
#include "v8config.h" // NOLINT(build/include_directory)
#if __cpp_lib_bitopts
#include <bit>
#endif // __cpp_lib_bitopts
#if defined(CPPGC_CAGED_HEAP)
namespace cppgc {
namespace internal {
class HeapBase;
class HeapBaseHandle;
#if defined(CPPGC_YOUNG_GENERATION)
// AgeTable is the bytemap needed for the fast generation check in the write
// barrier. AgeTable contains entries that correspond to 4096 bytes memory
// regions (cards). Each entry in the table represents generation of the objects
// that reside on the corresponding card (young, old or mixed).
class V8_EXPORT AgeTable final {
static constexpr size_t kRequiredSize = 1 * api_constants::kMB;
static constexpr size_t kAllocationGranularity =
api_constants::kAllocationGranularity;
public:
// Represents age of the objects living on a single card.
enum class Age : uint8_t { kOld, kYoung, kMixed };
// When setting age for a range, consider or ignore ages of the adjacent
// cards.
enum class AdjacentCardsPolicy : uint8_t { kConsider, kIgnore };
static constexpr size_t kCardSizeInBytes =
api_constants::kCagedHeapReservationSize / kRequiredSize;
void SetAge(uintptr_t cage_offset, Age age) {
table_[card(cage_offset)] = age;
}
V8_INLINE Age GetAge(uintptr_t cage_offset) const {
return table_[card(cage_offset)];
}
void SetAgeForRange(uintptr_t cage_offset_begin, uintptr_t cage_offset_end,
Age age, AdjacentCardsPolicy adjacent_cards_policy);
Age GetAgeForRange(uintptr_t cage_offset_begin,
uintptr_t cage_offset_end) const;
void ResetForTesting();
private:
V8_INLINE size_t card(uintptr_t offset) const {
constexpr size_t kGranularityBits =
#if __cpp_lib_bitopts
std::countr_zero(static_cast<uint32_t>(kCardSizeInBytes));
#elif V8_HAS_BUILTIN_CTZ
__builtin_ctz(static_cast<uint32_t>(kCardSizeInBytes));
#else //! V8_HAS_BUILTIN_CTZ
// Hardcode and check with assert.
#if defined(CPPGC_2GB_CAGE)
11;
#else // !defined(CPPGC_2GB_CAGE)
12;
#endif // !defined(CPPGC_2GB_CAGE)
#endif // !V8_HAS_BUILTIN_CTZ
static_assert((1 << kGranularityBits) == kCardSizeInBytes);
const size_t entry = offset >> kGranularityBits;
CPPGC_DCHECK(table_.size() > entry);
return entry;
}
std::array<Age, kRequiredSize> table_;
};
static_assert(sizeof(AgeTable) == 1 * api_constants::kMB,
"Size of AgeTable is 1MB");
#endif // CPPGC_YOUNG_GENERATION
struct CagedHeapLocalData final {
V8_INLINE static CagedHeapLocalData& Get() {
return *reinterpret_cast<CagedHeapLocalData*>(CagedHeapBase::GetBase());
}
#if defined(CPPGC_YOUNG_GENERATION)
AgeTable age_table;
#endif
};
} // namespace internal
} // namespace cppgc
#endif // defined(CPPGC_CAGED_HEAP)
#endif // INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_

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// Copyright 2022 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_CAGED_HEAP_H_
#define INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_H_
#include <climits>
#include <cstddef>
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/base-page-handle.h"
#include "v8config.h" // NOLINT(build/include_directory)
#if defined(CPPGC_CAGED_HEAP)
namespace cppgc {
namespace internal {
class V8_EXPORT CagedHeapBase {
public:
V8_INLINE static uintptr_t OffsetFromAddress(const void* address) {
return reinterpret_cast<uintptr_t>(address) &
(api_constants::kCagedHeapReservationAlignment - 1);
}
V8_INLINE static bool IsWithinCage(const void* address) {
CPPGC_DCHECK(g_heap_base_);
return (reinterpret_cast<uintptr_t>(address) &
~(api_constants::kCagedHeapReservationAlignment - 1)) ==
g_heap_base_;
}
V8_INLINE static bool AreWithinCage(const void* addr1, const void* addr2) {
#if defined(CPPGC_2GB_CAGE)
static constexpr size_t kHalfWordShift = sizeof(uint32_t) * CHAR_BIT - 1;
#else //! defined(CPPGC_2GB_CAGE)
static constexpr size_t kHalfWordShift = sizeof(uint32_t) * CHAR_BIT;
#endif //! defined(CPPGC_2GB_CAGE)
static_assert((static_cast<size_t>(1) << kHalfWordShift) ==
api_constants::kCagedHeapReservationSize);
CPPGC_DCHECK(g_heap_base_);
return !(((reinterpret_cast<uintptr_t>(addr1) ^ g_heap_base_) |
(reinterpret_cast<uintptr_t>(addr2) ^ g_heap_base_)) >>
kHalfWordShift);
}
V8_INLINE static uintptr_t GetBase() { return g_heap_base_; }
private:
friend class CagedHeap;
static uintptr_t g_heap_base_;
};
} // namespace internal
} // namespace cppgc
#endif // defined(CPPGC_CAGED_HEAP)
#endif // INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_H_

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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_COMPILER_SPECIFIC_H_
#define INCLUDE_CPPGC_INTERNAL_COMPILER_SPECIFIC_H_
namespace cppgc {
#if defined(__has_attribute)
#define CPPGC_HAS_ATTRIBUTE(FEATURE) __has_attribute(FEATURE)
#else
#define CPPGC_HAS_ATTRIBUTE(FEATURE) 0
#endif
#if defined(__has_cpp_attribute)
#define CPPGC_HAS_CPP_ATTRIBUTE(FEATURE) __has_cpp_attribute(FEATURE)
#else
#define CPPGC_HAS_CPP_ATTRIBUTE(FEATURE) 0
#endif
// [[no_unique_address]] comes in C++20 but supported in clang with -std >=
// c++11.
#if CPPGC_HAS_CPP_ATTRIBUTE(no_unique_address)
#define CPPGC_NO_UNIQUE_ADDRESS [[no_unique_address]]
#else
#define CPPGC_NO_UNIQUE_ADDRESS
#endif
#if CPPGC_HAS_ATTRIBUTE(unused)
#define CPPGC_UNUSED __attribute__((unused))
#else
#define CPPGC_UNUSED
#endif
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_COMPILER_SPECIFIC_H_

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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_FINALIZER_TRAIT_H_
#define INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_
#include <type_traits>
#include "cppgc/type-traits.h"
namespace cppgc {
namespace internal {
using FinalizationCallback = void (*)(void*);
template <typename T, typename = void>
struct HasFinalizeGarbageCollectedObject : std::false_type {};
template <typename T>
struct HasFinalizeGarbageCollectedObject<
T,
std::void_t<decltype(std::declval<T>().FinalizeGarbageCollectedObject())>>
: std::true_type {};
// The FinalizerTraitImpl specifies how to finalize objects.
template <typename T, bool isFinalized>
struct FinalizerTraitImpl;
template <typename T>
struct FinalizerTraitImpl<T, true> {
private:
// Dispatch to custom FinalizeGarbageCollectedObject().
struct Custom {
static void Call(void* obj) {
static_cast<T*>(obj)->FinalizeGarbageCollectedObject();
}
};
// Dispatch to regular destructor.
struct Destructor {
static void Call(void* obj) { static_cast<T*>(obj)->~T(); }
};
using FinalizeImpl =
std::conditional_t<HasFinalizeGarbageCollectedObject<T>::value, Custom,
Destructor>;
public:
static void Finalize(void* obj) {
static_assert(sizeof(T), "T must be fully defined");
FinalizeImpl::Call(obj);
}
};
template <typename T>
struct FinalizerTraitImpl<T, false> {
static void Finalize(void* obj) {
static_assert(sizeof(T), "T must be fully defined");
}
};
// The FinalizerTrait is used to determine if a type requires finalization and
// what finalization means.
template <typename T>
struct FinalizerTrait {
private:
// Object has a finalizer if it has
// - a custom FinalizeGarbageCollectedObject method, or
// - a destructor.
static constexpr bool kNonTrivialFinalizer =
internal::HasFinalizeGarbageCollectedObject<T>::value ||
!std::is_trivially_destructible<typename std::remove_cv<T>::type>::value;
static void Finalize(void* obj) {
internal::FinalizerTraitImpl<T, kNonTrivialFinalizer>::Finalize(obj);
}
public:
static constexpr bool HasFinalizer() { return kNonTrivialFinalizer; }
// The callback used to finalize an object of type T.
static constexpr FinalizationCallback kCallback =
kNonTrivialFinalizer ? Finalize : nullptr;
};
template <typename T>
constexpr FinalizationCallback FinalizerTrait<T>::kCallback;
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_

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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/logging.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;
struct V8_EXPORT EnsureGCInfoIndexTrait final {
// Acquires a new GC info object and updates `registered_index` with the index
// that identifies that new info accordingly.
template <typename T>
V8_INLINE static void EnsureIndex(
std::atomic<GCInfoIndex>& registered_index) {
EnsureGCInfoIndexTraitDispatch<T>{}(registered_index);
}
private:
template <typename T, bool = std::is_polymorphic<T>::value,
bool = FinalizerTrait<T>::HasFinalizer(),
bool = NameTrait<T>::HasNonHiddenName()>
struct EnsureGCInfoIndexTraitDispatch;
static void V8_PRESERVE_MOST
EnsureGCInfoIndexPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback,
FinalizationCallback, NameCallback);
static void V8_PRESERVE_MOST EnsureGCInfoIndexPolymorphic(
std::atomic<GCInfoIndex>&, TraceCallback, FinalizationCallback);
static void V8_PRESERVE_MOST EnsureGCInfoIndexPolymorphic(
std::atomic<GCInfoIndex>&, TraceCallback, NameCallback);
static void V8_PRESERVE_MOST
EnsureGCInfoIndexPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback);
static void V8_PRESERVE_MOST
EnsureGCInfoIndexNonPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback,
FinalizationCallback, NameCallback);
static void V8_PRESERVE_MOST EnsureGCInfoIndexNonPolymorphic(
std::atomic<GCInfoIndex>&, TraceCallback, FinalizationCallback);
static void V8_PRESERVE_MOST EnsureGCInfoIndexNonPolymorphic(
std::atomic<GCInfoIndex>&, TraceCallback, NameCallback);
static void V8_PRESERVE_MOST
EnsureGCInfoIndexNonPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback);
};
#define DISPATCH(is_polymorphic, has_finalizer, has_non_hidden_name, function) \
template <typename T> \
struct EnsureGCInfoIndexTrait::EnsureGCInfoIndexTraitDispatch< \
T, is_polymorphic, has_finalizer, has_non_hidden_name> { \
V8_INLINE void operator()(std::atomic<GCInfoIndex>& registered_index) { \
function; \
} \
};
// --------------------------------------------------------------------- //
// DISPATCH(is_polymorphic, has_finalizer, has_non_hidden_name, function)
// --------------------------------------------------------------------- //
DISPATCH(true, true, true, //
EnsureGCInfoIndexPolymorphic(registered_index, //
TraceTrait<T>::Trace, //
FinalizerTrait<T>::kCallback, //
NameTrait<T>::GetName)) //
DISPATCH(true, true, false, //
EnsureGCInfoIndexPolymorphic(registered_index, //
TraceTrait<T>::Trace, //
FinalizerTrait<T>::kCallback)) //
DISPATCH(true, false, true, //
EnsureGCInfoIndexPolymorphic(registered_index, //
TraceTrait<T>::Trace, //
NameTrait<T>::GetName)) //
DISPATCH(true, false, false, //
EnsureGCInfoIndexPolymorphic(registered_index, //
TraceTrait<T>::Trace)) //
DISPATCH(false, true, true, //
EnsureGCInfoIndexNonPolymorphic(registered_index, //
TraceTrait<T>::Trace, //
FinalizerTrait<T>::kCallback, //
NameTrait<T>::GetName)) //
DISPATCH(false, true, false, //
EnsureGCInfoIndexNonPolymorphic(registered_index, //
TraceTrait<T>::Trace, //
FinalizerTrait<T>::kCallback)) //
DISPATCH(false, false, true, //
EnsureGCInfoIndexNonPolymorphic(registered_index, //
TraceTrait<T>::Trace, //
NameTrait<T>::GetName)) //
DISPATCH(false, false, false, //
EnsureGCInfoIndexNonPolymorphic(registered_index, //
TraceTrait<T>::Trace)) //
#undef DISPATCH
// 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 {
V8_INLINE static GCInfoIndex Index() {
static_assert(sizeof(T), "T must be fully defined");
static std::atomic<GCInfoIndex>
registered_index; // Uses zero initialization.
GCInfoIndex index = registered_index.load(std::memory_order_acquire);
if (V8_UNLIKELY(!index)) {
EnsureGCInfoIndexTrait::EnsureIndex<T>(registered_index);
// Slow path call uses V8_PRESERVE_MOST which does not support return
// values (also preserves RAX). Avoid out parameter by just reloading the
// value here which at this point is guaranteed to be set.
index = registered_index.load(std::memory_order_acquire);
CPPGC_DCHECK(index != 0);
}
return index;
}
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_GC_INFO_H_

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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_LOGGING_H_
#define INCLUDE_CPPGC_INTERNAL_LOGGING_H_
#include "cppgc/source-location.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
void V8_EXPORT DCheckImpl(const char*,
const SourceLocation& = SourceLocation::Current());
[[noreturn]] void V8_EXPORT
FatalImpl(const char*, const SourceLocation& = SourceLocation::Current());
// Used to ignore -Wunused-variable.
template <typename>
struct EatParams {};
#if defined(DEBUG)
#define CPPGC_DCHECK_MSG(condition, message) \
do { \
if (V8_UNLIKELY(!(condition))) { \
::cppgc::internal::DCheckImpl(message); \
} \
} while (false)
#else // !defined(DEBUG)
#define CPPGC_DCHECK_MSG(condition, message) \
(static_cast<void>(::cppgc::internal::EatParams<decltype( \
static_cast<void>(condition), message)>{}))
#endif // !defined(DEBUG)
#define CPPGC_DCHECK(condition) CPPGC_DCHECK_MSG(condition, #condition)
#define CPPGC_CHECK_MSG(condition, message) \
do { \
if (V8_UNLIKELY(!(condition))) { \
::cppgc::internal::FatalImpl(message); \
} \
} while (false)
#define CPPGC_CHECK(condition) CPPGC_CHECK_MSG(condition, #condition)
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_LOGGING_H_

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// Copyright 2022 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_MEMBER_STORAGE_H_
#define INCLUDE_CPPGC_INTERNAL_MEMBER_STORAGE_H_
#include <atomic>
#include <cstddef>
#include <type_traits>
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/logging.h"
#include "cppgc/sentinel-pointer.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
enum class WriteBarrierSlotType {
kCompressed,
kUncompressed,
};
#if defined(CPPGC_POINTER_COMPRESSION)
#if defined(__clang__)
// Attribute const allows the compiler to assume that CageBaseGlobal::g_base_
// doesn't change (e.g. across calls) and thereby avoid redundant loads.
#define CPPGC_CONST __attribute__((const))
#define CPPGC_REQUIRE_CONSTANT_INIT \
__attribute__((require_constant_initialization))
#else // defined(__clang__)
#define CPPGC_CONST
#define CPPGC_REQUIRE_CONSTANT_INIT
#endif // defined(__clang__)
class V8_EXPORT CageBaseGlobal final {
public:
V8_INLINE CPPGC_CONST static uintptr_t Get() {
CPPGC_DCHECK(IsBaseConsistent());
return g_base_.base;
}
V8_INLINE CPPGC_CONST static bool IsSet() {
CPPGC_DCHECK(IsBaseConsistent());
return (g_base_.base & ~kLowerHalfWordMask) != 0;
}
private:
// We keep the lower halfword as ones to speed up decompression.
static constexpr uintptr_t kLowerHalfWordMask =
(api_constants::kCagedHeapReservationAlignment - 1);
static union alignas(api_constants::kCachelineSize) Base {
uintptr_t base;
char cache_line[api_constants::kCachelineSize];
} g_base_ CPPGC_REQUIRE_CONSTANT_INIT;
CageBaseGlobal() = delete;
V8_INLINE static bool IsBaseConsistent() {
return kLowerHalfWordMask == (g_base_.base & kLowerHalfWordMask);
}
friend class CageBaseGlobalUpdater;
};
#undef CPPGC_REQUIRE_CONSTANT_INIT
#undef CPPGC_CONST
class V8_TRIVIAL_ABI CompressedPointer final {
public:
using IntegralType = uint32_t;
static constexpr auto kWriteBarrierSlotType =
WriteBarrierSlotType::kCompressed;
V8_INLINE CompressedPointer() : value_(0u) {}
V8_INLINE explicit CompressedPointer(const void* ptr)
: value_(Compress(ptr)) {}
V8_INLINE explicit CompressedPointer(std::nullptr_t) : value_(0u) {}
V8_INLINE explicit CompressedPointer(SentinelPointer)
: value_(kCompressedSentinel) {}
V8_INLINE const void* Load() const { return Decompress(value_); }
V8_INLINE const void* LoadAtomic() const {
return Decompress(
reinterpret_cast<const std::atomic<IntegralType>&>(value_).load(
std::memory_order_relaxed));
}
V8_INLINE void Store(const void* ptr) { value_ = Compress(ptr); }
V8_INLINE void StoreAtomic(const void* value) {
reinterpret_cast<std::atomic<IntegralType>&>(value_).store(
Compress(value), std::memory_order_relaxed);
}
V8_INLINE void Clear() { value_ = 0u; }
V8_INLINE bool IsCleared() const { return !value_; }
V8_INLINE bool IsSentinel() const { return value_ == kCompressedSentinel; }
V8_INLINE uint32_t GetAsInteger() const { return value_; }
V8_INLINE friend bool operator==(CompressedPointer a, CompressedPointer b) {
return a.value_ == b.value_;
}
V8_INLINE friend bool operator!=(CompressedPointer a, CompressedPointer b) {
return a.value_ != b.value_;
}
V8_INLINE friend bool operator<(CompressedPointer a, CompressedPointer b) {
return a.value_ < b.value_;
}
V8_INLINE friend bool operator<=(CompressedPointer a, CompressedPointer b) {
return a.value_ <= b.value_;
}
V8_INLINE friend bool operator>(CompressedPointer a, CompressedPointer b) {
return a.value_ > b.value_;
}
V8_INLINE friend bool operator>=(CompressedPointer a, CompressedPointer b) {
return a.value_ >= b.value_;
}
static V8_INLINE IntegralType Compress(const void* ptr) {
static_assert(
SentinelPointer::kSentinelValue == 0b10,
"The compression scheme relies on the sentinel encoded as 0b10");
static constexpr size_t kGigaCageMask =
~(api_constants::kCagedHeapReservationAlignment - 1);
CPPGC_DCHECK(CageBaseGlobal::IsSet());
const uintptr_t base = CageBaseGlobal::Get();
CPPGC_DCHECK(!ptr || ptr == kSentinelPointer ||
(base & kGigaCageMask) ==
(reinterpret_cast<uintptr_t>(ptr) & kGigaCageMask));
#if defined(CPPGC_2GB_CAGE)
// Truncate the pointer.
auto compressed =
static_cast<IntegralType>(reinterpret_cast<uintptr_t>(ptr));
#else // !defined(CPPGC_2GB_CAGE)
const auto uptr = reinterpret_cast<uintptr_t>(ptr);
// Shift the pointer by one and truncate.
auto compressed = static_cast<IntegralType>(uptr >> 1);
#endif // !defined(CPPGC_2GB_CAGE)
// Normal compressed pointers must have the MSB set.
CPPGC_DCHECK((!compressed || compressed == kCompressedSentinel) ||
(compressed & (1 << 31)));
return compressed;
}
static V8_INLINE void* Decompress(IntegralType ptr) {
CPPGC_DCHECK(CageBaseGlobal::IsSet());
const uintptr_t base = CageBaseGlobal::Get();
// Treat compressed pointer as signed and cast it to uint64_t, which will
// sign-extend it.
#if defined(CPPGC_2GB_CAGE)
const uint64_t mask = static_cast<uint64_t>(static_cast<int32_t>(ptr));
#else // !defined(CPPGC_2GB_CAGE)
// Then, shift the result by one. It's important to shift the unsigned
// value, as otherwise it would result in undefined behavior.
const uint64_t mask = static_cast<uint64_t>(static_cast<int32_t>(ptr)) << 1;
#endif // !defined(CPPGC_2GB_CAGE)
return reinterpret_cast<void*>(mask & base);
}
private:
#if defined(CPPGC_2GB_CAGE)
static constexpr IntegralType kCompressedSentinel =
SentinelPointer::kSentinelValue;
#else // !defined(CPPGC_2GB_CAGE)
static constexpr IntegralType kCompressedSentinel =
SentinelPointer::kSentinelValue >> 1;
#endif // !defined(CPPGC_2GB_CAGE)
// All constructors initialize `value_`. Do not add a default value here as it
// results in a non-atomic write on some builds, even when the atomic version
// of the constructor is used.
IntegralType value_;
};
#endif // defined(CPPGC_POINTER_COMPRESSION)
class V8_TRIVIAL_ABI RawPointer final {
public:
using IntegralType = uintptr_t;
static constexpr auto kWriteBarrierSlotType =
WriteBarrierSlotType::kUncompressed;
V8_INLINE RawPointer() : ptr_(nullptr) {}
V8_INLINE explicit RawPointer(const void* ptr) : ptr_(ptr) {}
V8_INLINE const void* Load() const { return ptr_; }
V8_INLINE const void* LoadAtomic() const {
return reinterpret_cast<const std::atomic<const void*>&>(ptr_).load(
std::memory_order_relaxed);
}
V8_INLINE void Store(const void* ptr) { ptr_ = ptr; }
V8_INLINE void StoreAtomic(const void* ptr) {
reinterpret_cast<std::atomic<const void*>&>(ptr_).store(
ptr, std::memory_order_relaxed);
}
V8_INLINE void Clear() { ptr_ = nullptr; }
V8_INLINE bool IsCleared() const { return !ptr_; }
V8_INLINE bool IsSentinel() const { return ptr_ == kSentinelPointer; }
V8_INLINE uintptr_t GetAsInteger() const {
return reinterpret_cast<uintptr_t>(ptr_);
}
V8_INLINE friend bool operator==(RawPointer a, RawPointer b) {
return a.ptr_ == b.ptr_;
}
V8_INLINE friend bool operator!=(RawPointer a, RawPointer b) {
return a.ptr_ != b.ptr_;
}
V8_INLINE friend bool operator<(RawPointer a, RawPointer b) {
return a.ptr_ < b.ptr_;
}
V8_INLINE friend bool operator<=(RawPointer a, RawPointer b) {
return a.ptr_ <= b.ptr_;
}
V8_INLINE friend bool operator>(RawPointer a, RawPointer b) {
return a.ptr_ > b.ptr_;
}
V8_INLINE friend bool operator>=(RawPointer a, RawPointer b) {
return a.ptr_ >= b.ptr_;
}
private:
// All constructors initialize `ptr_`. Do not add a default value here as it
// results in a non-atomic write on some builds, even when the atomic version
// of the constructor is used.
const void* ptr_;
};
#if defined(CPPGC_POINTER_COMPRESSION)
using DefaultMemberStorage = CompressedPointer;
#else // !defined(CPPGC_POINTER_COMPRESSION)
using DefaultMemberStorage = RawPointer;
#endif // !defined(CPPGC_POINTER_COMPRESSION)
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_MEMBER_STORAGE_H_

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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_NAME_TRAIT_H_
#define INCLUDE_CPPGC_INTERNAL_NAME_TRAIT_H_
#include <cstddef>
#include <cstdint>
#include <type_traits>
#include "cppgc/name-provider.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
#if CPPGC_SUPPORTS_OBJECT_NAMES && defined(__clang__)
#define CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME 1
// Provides constexpr c-string storage for a name of fixed |Size| characters.
// Automatically appends terminating 0 byte.
template <size_t Size>
struct NameBuffer {
char name[Size + 1]{};
static constexpr NameBuffer FromCString(const char* str) {
NameBuffer result;
for (size_t i = 0; i < Size; ++i) result.name[i] = str[i];
result.name[Size] = 0;
return result;
}
};
template <typename T>
const char* GetTypename() {
static constexpr char kSelfPrefix[] =
"const char *cppgc::internal::GetTypename() [T =";
static_assert(__builtin_strncmp(__PRETTY_FUNCTION__, kSelfPrefix,
sizeof(kSelfPrefix) - 1) == 0,
"The prefix must match");
static constexpr const char* kTypenameStart =
__PRETTY_FUNCTION__ + sizeof(kSelfPrefix);
static constexpr size_t kTypenameSize =
__builtin_strlen(__PRETTY_FUNCTION__) - sizeof(kSelfPrefix) - 1;
// NameBuffer is an indirection that is needed to make sure that only a
// substring of __PRETTY_FUNCTION__ gets materialized in the binary.
static constexpr auto buffer =
NameBuffer<kTypenameSize>::FromCString(kTypenameStart);
return buffer.name;
}
#else
#define CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME 0
#endif
struct HeapObjectName {
const char* value;
bool name_was_hidden;
};
enum class HeapObjectNameForUnnamedObject : uint8_t {
kUseClassNameIfSupported,
kUseHiddenName,
};
class V8_EXPORT NameTraitBase {
protected:
static HeapObjectName GetNameFromTypeSignature(const char*);
};
// Trait that specifies how the garbage collector retrieves the name for a
// given object.
template <typename T>
class NameTrait final : public NameTraitBase {
public:
static constexpr bool HasNonHiddenName() {
#if CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME
return true;
#elif CPPGC_SUPPORTS_OBJECT_NAMES
return true;
#else // !CPPGC_SUPPORTS_OBJECT_NAMES
return std::is_base_of<NameProvider, T>::value;
#endif // !CPPGC_SUPPORTS_OBJECT_NAMES
}
static HeapObjectName GetName(
const void* obj, HeapObjectNameForUnnamedObject name_retrieval_mode) {
return GetNameFor(static_cast<const T*>(obj), name_retrieval_mode);
}
private:
static HeapObjectName GetNameFor(const NameProvider* name_provider,
HeapObjectNameForUnnamedObject) {
// Objects inheriting from `NameProvider` are not considered unnamed as
// users already provided a name for them.
return {name_provider->GetHumanReadableName(), false};
}
static HeapObjectName GetNameFor(
const void*, HeapObjectNameForUnnamedObject name_retrieval_mode) {
if (name_retrieval_mode == HeapObjectNameForUnnamedObject::kUseHiddenName)
return {NameProvider::kHiddenName, true};
#if CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME
return {GetTypename<T>(), false};
#elif CPPGC_SUPPORTS_OBJECT_NAMES
#if defined(V8_CC_GNU)
#define PRETTY_FUNCTION_VALUE __PRETTY_FUNCTION__
#elif defined(V8_CC_MSVC)
#define PRETTY_FUNCTION_VALUE __FUNCSIG__
#else
#define PRETTY_FUNCTION_VALUE nullptr
#endif
static const HeapObjectName leaky_name =
GetNameFromTypeSignature(PRETTY_FUNCTION_VALUE);
return leaky_name;
#undef PRETTY_FUNCTION_VALUE
#else // !CPPGC_SUPPORTS_OBJECT_NAMES
return {NameProvider::kHiddenName, true};
#endif // !CPPGC_SUPPORTS_OBJECT_NAMES
}
};
using NameCallback = HeapObjectName (*)(const void*,
HeapObjectNameForUnnamedObject);
} // namespace internal
} // namespace cppgc
#undef CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME
#endif // INCLUDE_CPPGC_INTERNAL_NAME_TRAIT_H_

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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_PERSISTENT_NODE_H_
#define INCLUDE_CPPGC_INTERNAL_PERSISTENT_NODE_H_
#include <array>
#include <memory>
#include <vector>
#include "cppgc/internal/logging.h"
#include "cppgc/trace-trait.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
class CrossThreadPersistentRegion;
class FatalOutOfMemoryHandler;
class RootVisitor;
// PersistentNode represents a variant of two states:
// 1) traceable node with a back pointer to the Persistent object;
// 2) freelist entry.
class PersistentNode final {
public:
PersistentNode() = default;
PersistentNode(const PersistentNode&) = delete;
PersistentNode& operator=(const PersistentNode&) = delete;
void InitializeAsUsedNode(void* owner, TraceRootCallback trace) {
CPPGC_DCHECK(trace);
owner_ = owner;
trace_ = trace;
}
void InitializeAsFreeNode(PersistentNode* next) {
next_ = next;
trace_ = nullptr;
}
void UpdateOwner(void* owner) {
CPPGC_DCHECK(IsUsed());
owner_ = owner;
}
PersistentNode* FreeListNext() const {
CPPGC_DCHECK(!IsUsed());
return next_;
}
void Trace(RootVisitor& root_visitor) const {
CPPGC_DCHECK(IsUsed());
trace_(root_visitor, owner_);
}
bool IsUsed() const { return trace_; }
void* owner() const {
CPPGC_DCHECK(IsUsed());
return owner_;
}
private:
// PersistentNode acts as a designated union:
// If trace_ != nullptr, owner_ points to the corresponding Persistent handle.
// Otherwise, next_ points to the next freed PersistentNode.
union {
void* owner_ = nullptr;
PersistentNode* next_;
};
TraceRootCallback trace_ = nullptr;
};
class V8_EXPORT PersistentRegionBase {
using PersistentNodeSlots = std::array<PersistentNode, 256u>;
public:
// Clears Persistent fields to avoid stale pointers after heap teardown.
~PersistentRegionBase();
PersistentRegionBase(const PersistentRegionBase&) = delete;
PersistentRegionBase& operator=(const PersistentRegionBase&) = delete;
void Iterate(RootVisitor&);
size_t NodesInUse() const;
void ClearAllUsedNodes();
protected:
explicit PersistentRegionBase(const FatalOutOfMemoryHandler& oom_handler);
PersistentNode* TryAllocateNodeFromFreeList(void* owner,
TraceRootCallback trace) {
PersistentNode* node = nullptr;
if (V8_LIKELY(free_list_head_)) {
node = free_list_head_;
free_list_head_ = free_list_head_->FreeListNext();
CPPGC_DCHECK(!node->IsUsed());
node->InitializeAsUsedNode(owner, trace);
nodes_in_use_++;
}
return node;
}
void FreeNode(PersistentNode* node) {
CPPGC_DCHECK(node);
CPPGC_DCHECK(node->IsUsed());
node->InitializeAsFreeNode(free_list_head_);
free_list_head_ = node;
CPPGC_DCHECK(nodes_in_use_ > 0);
nodes_in_use_--;
}
PersistentNode* RefillFreeListAndAllocateNode(void* owner,
TraceRootCallback trace);
private:
template <typename PersistentBaseClass>
void ClearAllUsedNodes();
void RefillFreeList();
std::vector<std::unique_ptr<PersistentNodeSlots>> nodes_;
PersistentNode* free_list_head_ = nullptr;
size_t nodes_in_use_ = 0;
const FatalOutOfMemoryHandler& oom_handler_;
friend class CrossThreadPersistentRegion;
};
// Variant of PersistentRegionBase that checks whether the allocation and
// freeing happens only on the thread that created the region.
class V8_EXPORT PersistentRegion final : public PersistentRegionBase {
public:
explicit PersistentRegion(const FatalOutOfMemoryHandler&);
// Clears Persistent fields to avoid stale pointers after heap teardown.
~PersistentRegion() = default;
PersistentRegion(const PersistentRegion&) = delete;
PersistentRegion& operator=(const PersistentRegion&) = delete;
V8_INLINE PersistentNode* AllocateNode(void* owner, TraceRootCallback trace) {
CPPGC_DCHECK(IsCreationThread());
auto* node = TryAllocateNodeFromFreeList(owner, trace);
if (V8_LIKELY(node)) return node;
// Slow path allocation allows for checking thread correspondence.
CPPGC_CHECK(IsCreationThread());
return RefillFreeListAndAllocateNode(owner, trace);
}
V8_INLINE void FreeNode(PersistentNode* node) {
CPPGC_DCHECK(IsCreationThread());
PersistentRegionBase::FreeNode(node);
}
private:
bool IsCreationThread();
int creation_thread_id_;
};
// CrossThreadPersistent uses PersistentRegionBase but protects it using this
// lock when needed.
class V8_EXPORT PersistentRegionLock final {
public:
PersistentRegionLock();
~PersistentRegionLock();
static void AssertLocked();
};
// Variant of PersistentRegionBase that checks whether the PersistentRegionLock
// is locked.
class V8_EXPORT CrossThreadPersistentRegion final
: protected PersistentRegionBase {
public:
explicit CrossThreadPersistentRegion(const FatalOutOfMemoryHandler&);
// Clears Persistent fields to avoid stale pointers after heap teardown.
~CrossThreadPersistentRegion();
CrossThreadPersistentRegion(const CrossThreadPersistentRegion&) = delete;
CrossThreadPersistentRegion& operator=(const CrossThreadPersistentRegion&) =
delete;
V8_INLINE PersistentNode* AllocateNode(void* owner, TraceRootCallback trace) {
PersistentRegionLock::AssertLocked();
auto* node = TryAllocateNodeFromFreeList(owner, trace);
if (V8_LIKELY(node)) return node;
return RefillFreeListAndAllocateNode(owner, trace);
}
V8_INLINE void FreeNode(PersistentNode* node) {
PersistentRegionLock::AssertLocked();
PersistentRegionBase::FreeNode(node);
}
void Iterate(RootVisitor&);
size_t NodesInUse() const;
void ClearAllUsedNodes();
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_PERSISTENT_NODE_H_

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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_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 {
V8_INLINE static void InitializingBarrier(const void*, const void*) {
// Since in initializing writes the source object is always white, having no
// barrier doesn't break the tri-color invariant.
}
template <WriteBarrierSlotType SlotType>
V8_INLINE static void AssigningBarrier(const void* slot, const void* value) {
#ifdef CPPGC_SLIM_WRITE_BARRIER
if (V8_UNLIKELY(WriteBarrier::IsEnabled()))
WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot);
#else // !CPPGC_SLIM_WRITE_BARRIER
WriteBarrier::Params params;
const WriteBarrier::Type type =
WriteBarrier::GetWriteBarrierType(slot, value, params);
WriteBarrier(type, params, slot, value);
#endif // !CPPGC_SLIM_WRITE_BARRIER
}
template <WriteBarrierSlotType SlotType>
V8_INLINE static void AssigningBarrier(const void* slot, RawPointer storage) {
static_assert(
SlotType == WriteBarrierSlotType::kUncompressed,
"Assigning storages of Member and UncompressedMember is not supported");
#ifdef CPPGC_SLIM_WRITE_BARRIER
if (V8_UNLIKELY(WriteBarrier::IsEnabled()))
WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot);
#else // !CPPGC_SLIM_WRITE_BARRIER
WriteBarrier::Params params;
const WriteBarrier::Type type =
WriteBarrier::GetWriteBarrierType(slot, storage, params);
WriteBarrier(type, params, slot, storage.Load());
#endif // !CPPGC_SLIM_WRITE_BARRIER
}
#if defined(CPPGC_POINTER_COMPRESSION)
template <WriteBarrierSlotType SlotType>
V8_INLINE static void AssigningBarrier(const void* slot,
CompressedPointer storage) {
static_assert(
SlotType == WriteBarrierSlotType::kCompressed,
"Assigning storages of Member and UncompressedMember is not supported");
#ifdef CPPGC_SLIM_WRITE_BARRIER
if (V8_UNLIKELY(WriteBarrier::IsEnabled()))
WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot);
#else // !CPPGC_SLIM_WRITE_BARRIER
WriteBarrier::Params params;
const WriteBarrier::Type type =
WriteBarrier::GetWriteBarrierType(slot, storage, params);
WriteBarrier(type, params, slot, storage.Load());
#endif // !CPPGC_SLIM_WRITE_BARRIER
}
#endif // defined(CPPGC_POINTER_COMPRESSION)
private:
V8_INLINE static void WriteBarrier(WriteBarrier::Type type,
const WriteBarrier::Params& params,
const void* slot, const void* value) {
switch (type) {
case WriteBarrier::Type::kGenerational:
WriteBarrier::GenerationalBarrier<
WriteBarrier::GenerationalBarrierType::kPreciseSlot>(params, slot);
break;
case WriteBarrier::Type::kMarking:
WriteBarrier::DijkstraMarkingBarrier(params, value);
break;
case WriteBarrier::Type::kNone:
break;
}
}
};
struct NoWriteBarrierPolicy {
V8_INLINE static void InitializingBarrier(const void*, const void*) {}
template <WriteBarrierSlotType>
V8_INLINE static void AssigningBarrier(const void*, const void*) {}
template <WriteBarrierSlotType, typename MemberStorage>
V8_INLINE static void AssigningBarrier(const void*, MemberStorage) {}
};
class V8_EXPORT SameThreadEnabledCheckingPolicyBase {
protected:
void CheckPointerImpl(const void* ptr, bool points_to_payload,
bool check_off_heap_assignments);
const HeapBase* heap_ = nullptr;
};
template <bool kCheckOffHeapAssignments>
class V8_EXPORT SameThreadEnabledCheckingPolicy
: private SameThreadEnabledCheckingPolicyBase {
protected:
template <typename T>
void CheckPointer(const T* ptr) {
if (!ptr || (kSentinelPointer == ptr)) return;
CheckPointersImplTrampoline<T>::Call(this, ptr);
}
private:
template <typename T, bool = IsCompleteV<T>>
struct CheckPointersImplTrampoline {
static void Call(SameThreadEnabledCheckingPolicy* policy, const T* ptr) {
policy->CheckPointerImpl(ptr, false, kCheckOffHeapAssignments);
}
};
template <typename T>
struct CheckPointersImplTrampoline<T, true> {
static void Call(SameThreadEnabledCheckingPolicy* policy, const T* ptr) {
policy->CheckPointerImpl(ptr, IsGarbageCollectedTypeV<T>,
kCheckOffHeapAssignments);
}
};
};
class DisabledCheckingPolicy {
protected:
V8_INLINE void CheckPointer(const void*) {}
};
#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
using DefaultMemberCheckingPolicy = DisabledCheckingPolicy;
using DefaultPersistentCheckingPolicy = DisabledCheckingPolicy;
#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.
using DefaultCrossThreadPersistentCheckingPolicy = DisabledCheckingPolicy;
class KeepLocationPolicy {
public:
constexpr const SourceLocation& Location() const { return location_; }
protected:
constexpr KeepLocationPolicy() = default;
constexpr explicit KeepLocationPolicy(const SourceLocation& location)
: location_(location) {}
// KeepLocationPolicy must not copy underlying source locations.
KeepLocationPolicy(const KeepLocationPolicy&) = delete;
KeepLocationPolicy& operator=(const KeepLocationPolicy&) = delete;
// Location of the original moved from object should be preserved.
KeepLocationPolicy(KeepLocationPolicy&&) = default;
KeepLocationPolicy& operator=(KeepLocationPolicy&&) = default;
private:
SourceLocation location_;
};
class IgnoreLocationPolicy {
public:
constexpr SourceLocation Location() const { return {}; }
protected:
constexpr IgnoreLocationPolicy() = default;
constexpr explicit IgnoreLocationPolicy(const SourceLocation&) {}
};
#if CPPGC_SUPPORTS_OBJECT_NAMES
using DefaultLocationPolicy = KeepLocationPolicy;
#else
using DefaultLocationPolicy = IgnoreLocationPolicy;
#endif
struct StrongPersistentPolicy {
using IsStrongPersistent = std::true_type;
static V8_EXPORT PersistentRegion& GetPersistentRegion(const void* object);
};
struct WeakPersistentPolicy {
using IsStrongPersistent = std::false_type;
static V8_EXPORT PersistentRegion& GetPersistentRegion(const void* object);
};
struct StrongCrossThreadPersistentPolicy {
using IsStrongPersistent = std::true_type;
static V8_EXPORT CrossThreadPersistentRegion& GetPersistentRegion(
const void* object);
};
struct WeakCrossThreadPersistentPolicy {
using IsStrongPersistent = std::false_type;
static V8_EXPORT CrossThreadPersistentRegion& GetPersistentRegion(
const void* object);
};
// 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_

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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_WRITE_BARRIER_H_
#define INCLUDE_CPPGC_INTERNAL_WRITE_BARRIER_H_
#include <cstddef>
#include <cstdint>
#include "cppgc/heap-handle.h"
#include "cppgc/heap-state.h"
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/atomic-entry-flag.h"
#include "cppgc/internal/base-page-handle.h"
#include "cppgc/internal/member-storage.h"
#include "cppgc/platform.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/trace-trait.h"
#include "v8config.h" // NOLINT(build/include_directory)
#if defined(CPPGC_CAGED_HEAP)
#include "cppgc/internal/caged-heap-local-data.h"
#include "cppgc/internal/caged-heap.h"
#endif
namespace cppgc {
class HeapHandle;
namespace internal {
#if defined(CPPGC_CAGED_HEAP)
class WriteBarrierTypeForCagedHeapPolicy;
#else // !CPPGC_CAGED_HEAP
class WriteBarrierTypeForNonCagedHeapPolicy;
#endif // !CPPGC_CAGED_HEAP
class V8_EXPORT WriteBarrier final {
public:
enum class Type : uint8_t {
kNone,
kMarking,
kGenerational,
};
enum class GenerationalBarrierType : uint8_t {
kPreciseSlot,
kPreciseUncompressedSlot,
kImpreciseSlot,
};
struct Params {
HeapHandle* heap = nullptr;
#if V8_ENABLE_CHECKS
Type type = Type::kNone;
#endif // !V8_ENABLE_CHECKS
#if defined(CPPGC_CAGED_HEAP)
uintptr_t slot_offset = 0;
uintptr_t value_offset = 0;
#endif // CPPGC_CAGED_HEAP
};
enum class ValueMode {
kValuePresent,
kNoValuePresent,
};
// Returns the required write barrier for a given `slot` and `value`.
static V8_INLINE Type GetWriteBarrierType(const void* slot, const void* value,
Params& params);
// Returns the required write barrier for a given `slot` and `value`.
template <typename MemberStorage>
static V8_INLINE Type GetWriteBarrierType(const void* slot, MemberStorage,
Params& params);
// Returns the required write barrier for a given `slot`.
template <typename HeapHandleCallback>
static V8_INLINE Type GetWriteBarrierType(const void* slot, Params& params,
HeapHandleCallback callback);
// Returns the required write barrier for a given `value`.
static V8_INLINE Type GetWriteBarrierType(const void* value, Params& params);
#ifdef CPPGC_SLIM_WRITE_BARRIER
// A write barrier that combines `GenerationalBarrier()` and
// `DijkstraMarkingBarrier()`. We only pass a single parameter here to clobber
// as few registers as possible.
template <WriteBarrierSlotType>
static V8_NOINLINE void V8_PRESERVE_MOST
CombinedWriteBarrierSlow(const void* slot);
#endif // CPPGC_SLIM_WRITE_BARRIER
static V8_INLINE void DijkstraMarkingBarrier(const Params& params,
const void* object);
static V8_INLINE void DijkstraMarkingBarrierRange(
const Params& params, const void* first_element, size_t element_size,
size_t number_of_elements, TraceCallback trace_callback);
static V8_INLINE void SteeleMarkingBarrier(const Params& params,
const void* object);
#if defined(CPPGC_YOUNG_GENERATION)
template <GenerationalBarrierType>
static V8_INLINE void GenerationalBarrier(const Params& params,
const void* slot);
#else // !CPPGC_YOUNG_GENERATION
template <GenerationalBarrierType>
static V8_INLINE void GenerationalBarrier(const Params& params,
const void* slot){}
#endif // CPPGC_YOUNG_GENERATION
#if V8_ENABLE_CHECKS
static void CheckParams(Type expected_type, const Params& params);
#else // !V8_ENABLE_CHECKS
static void CheckParams(Type expected_type, const Params& params) {}
#endif // !V8_ENABLE_CHECKS
// The FlagUpdater class allows cppgc internal to update
// |write_barrier_enabled_|.
class FlagUpdater;
static bool IsEnabled() { return write_barrier_enabled_.MightBeEntered(); }
private:
WriteBarrier() = delete;
#if defined(CPPGC_CAGED_HEAP)
using WriteBarrierTypePolicy = WriteBarrierTypeForCagedHeapPolicy;
#else // !CPPGC_CAGED_HEAP
using WriteBarrierTypePolicy = WriteBarrierTypeForNonCagedHeapPolicy;
#endif // !CPPGC_CAGED_HEAP
static void DijkstraMarkingBarrierSlow(const void* value);
static void DijkstraMarkingBarrierSlowWithSentinelCheck(const void* value);
static void DijkstraMarkingBarrierRangeSlow(HeapHandle& heap_handle,
const void* first_element,
size_t element_size,
size_t number_of_elements,
TraceCallback trace_callback);
static void SteeleMarkingBarrierSlow(const void* value);
static void SteeleMarkingBarrierSlowWithSentinelCheck(const void* value);
#if defined(CPPGC_YOUNG_GENERATION)
static CagedHeapLocalData& GetLocalData(HeapHandle&);
static void GenerationalBarrierSlow(const CagedHeapLocalData& local_data,
const AgeTable& age_table,
const void* slot, uintptr_t value_offset,
HeapHandle* heap_handle);
static void GenerationalBarrierForUncompressedSlotSlow(
const CagedHeapLocalData& local_data, const AgeTable& age_table,
const void* slot, uintptr_t value_offset, HeapHandle* heap_handle);
static void GenerationalBarrierForSourceObjectSlow(
const CagedHeapLocalData& local_data, const void* object,
HeapHandle* heap_handle);
#endif // CPPGC_YOUNG_GENERATION
static AtomicEntryFlag write_barrier_enabled_;
};
template <WriteBarrier::Type type>
V8_INLINE WriteBarrier::Type SetAndReturnType(WriteBarrier::Params& params) {
if constexpr (type == WriteBarrier::Type::kNone)
return WriteBarrier::Type::kNone;
#if V8_ENABLE_CHECKS
params.type = type;
#endif // !V8_ENABLE_CHECKS
return type;
}
#if defined(CPPGC_CAGED_HEAP)
class V8_EXPORT WriteBarrierTypeForCagedHeapPolicy final {
public:
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
return ValueModeDispatch<value_mode>::Get(slot, value, params, callback);
}
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback,
typename MemberStorage>
static V8_INLINE WriteBarrier::Type Get(const void* slot, MemberStorage value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
return ValueModeDispatch<value_mode>::Get(slot, value, params, callback);
}
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
return GetNoSlot(value, params, callback);
}
private:
WriteBarrierTypeForCagedHeapPolicy() = delete;
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type GetNoSlot(const void* value,
WriteBarrier::Params& params,
HeapHandleCallback) {
const bool within_cage = CagedHeapBase::IsWithinCage(value);
if (!within_cage) return WriteBarrier::Type::kNone;
// We know that |value| points either within the normal page or to the
// beginning of large-page, so extract the page header by bitmasking.
BasePageHandle* page =
BasePageHandle::FromPayload(const_cast<void*>(value));
HeapHandle& heap_handle = page->heap_handle();
if (V8_UNLIKELY(heap_handle.is_incremental_marking_in_progress())) {
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
template <WriteBarrier::ValueMode value_mode>
struct ValueModeDispatch;
};
template <>
struct WriteBarrierTypeForCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kValuePresent> {
template <typename HeapHandleCallback, typename MemberStorage>
static V8_INLINE WriteBarrier::Type Get(const void* slot,
MemberStorage storage,
WriteBarrier::Params& params,
HeapHandleCallback) {
if (V8_LIKELY(!WriteBarrier::IsEnabled()))
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
return BarrierEnabledGet(slot, storage.Load(), params);
}
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value,
WriteBarrier::Params& params,
HeapHandleCallback) {
if (V8_LIKELY(!WriteBarrier::IsEnabled()))
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
return BarrierEnabledGet(slot, value, params);
}
private:
static V8_INLINE WriteBarrier::Type BarrierEnabledGet(
const void* slot, const void* value, WriteBarrier::Params& params) {
const bool within_cage = CagedHeapBase::AreWithinCage(slot, value);
if (!within_cage) return WriteBarrier::Type::kNone;
// We know that |value| points either within the normal page or to the
// beginning of large-page, so extract the page header by bitmasking.
BasePageHandle* page =
BasePageHandle::FromPayload(const_cast<void*>(value));
HeapHandle& heap_handle = page->heap_handle();
if (V8_LIKELY(!heap_handle.is_incremental_marking_in_progress())) {
#if defined(CPPGC_YOUNG_GENERATION)
if (!heap_handle.is_young_generation_enabled())
return WriteBarrier::Type::kNone;
params.heap = &heap_handle;
params.slot_offset = CagedHeapBase::OffsetFromAddress(slot);
params.value_offset = CagedHeapBase::OffsetFromAddress(value);
return SetAndReturnType<WriteBarrier::Type::kGenerational>(params);
#else // !CPPGC_YOUNG_GENERATION
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
#endif // !CPPGC_YOUNG_GENERATION
}
// Use marking barrier.
params.heap = &heap_handle;
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
};
template <>
struct WriteBarrierTypeForCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kNoValuePresent> {
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void*,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
if (V8_LIKELY(!WriteBarrier::IsEnabled()))
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
HeapHandle& handle = callback();
#if defined(CPPGC_YOUNG_GENERATION)
if (V8_LIKELY(!handle.is_incremental_marking_in_progress())) {
if (!handle.is_young_generation_enabled()) {
return WriteBarrier::Type::kNone;
}
params.heap = &handle;
// Check if slot is on stack.
if (V8_UNLIKELY(!CagedHeapBase::IsWithinCage(slot))) {
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
params.slot_offset = CagedHeapBase::OffsetFromAddress(slot);
return SetAndReturnType<WriteBarrier::Type::kGenerational>(params);
}
#else // !defined(CPPGC_YOUNG_GENERATION)
if (V8_UNLIKELY(!handle.is_incremental_marking_in_progress())) {
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
#endif // !defined(CPPGC_YOUNG_GENERATION)
params.heap = &handle;
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
};
#endif // CPPGC_CAGED_HEAP
class V8_EXPORT WriteBarrierTypeForNonCagedHeapPolicy final {
public:
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
return ValueModeDispatch<value_mode>::Get(slot, value, params, callback);
}
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, RawPointer value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
return ValueModeDispatch<value_mode>::Get(slot, value.Load(), params,
callback);
}
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
// The slot will never be used in `Get()` below.
return Get<WriteBarrier::ValueMode::kValuePresent>(nullptr, value, params,
callback);
}
private:
template <WriteBarrier::ValueMode value_mode>
struct ValueModeDispatch;
WriteBarrierTypeForNonCagedHeapPolicy() = delete;
};
template <>
struct WriteBarrierTypeForNonCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kValuePresent> {
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void*, const void* object,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
// The following check covers nullptr as well as sentinel pointer.
if (object <= static_cast<void*>(kSentinelPointer)) {
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
if (V8_LIKELY(!WriteBarrier::IsEnabled())) {
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
// We know that |object| is within the normal page or in the beginning of a
// large page, so extract the page header by bitmasking.
BasePageHandle* page =
BasePageHandle::FromPayload(const_cast<void*>(object));
HeapHandle& heap_handle = page->heap_handle();
if (V8_LIKELY(heap_handle.is_incremental_marking_in_progress())) {
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
};
template <>
struct WriteBarrierTypeForNonCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kNoValuePresent> {
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void*, const void*,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
if (V8_UNLIKELY(WriteBarrier::IsEnabled())) {
HeapHandle& handle = callback();
if (V8_LIKELY(handle.is_incremental_marking_in_progress())) {
params.heap = &handle;
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
}
return WriteBarrier::Type::kNone;
}
};
// static
WriteBarrier::Type WriteBarrier::GetWriteBarrierType(
const void* slot, const void* value, WriteBarrier::Params& params) {
return WriteBarrierTypePolicy::Get<ValueMode::kValuePresent>(slot, value,
params, []() {});
}
// static
template <typename MemberStorage>
WriteBarrier::Type WriteBarrier::GetWriteBarrierType(
const void* slot, MemberStorage value, WriteBarrier::Params& params) {
return WriteBarrierTypePolicy::Get<ValueMode::kValuePresent>(slot, value,
params, []() {});
}
// static
template <typename HeapHandleCallback>
WriteBarrier::Type WriteBarrier::GetWriteBarrierType(
const void* slot, WriteBarrier::Params& params,
HeapHandleCallback callback) {
return WriteBarrierTypePolicy::Get<ValueMode::kNoValuePresent>(
slot, nullptr, params, callback);
}
// static
WriteBarrier::Type WriteBarrier::GetWriteBarrierType(
const void* value, WriteBarrier::Params& params) {
return WriteBarrierTypePolicy::Get<ValueMode::kValuePresent>(value, params,
[]() {});
}
// static
void WriteBarrier::DijkstraMarkingBarrier(const Params& params,
const void* object) {
CheckParams(Type::kMarking, params);
#if defined(CPPGC_CAGED_HEAP)
// Caged heap already filters out sentinels.
DijkstraMarkingBarrierSlow(object);
#else // !CPPGC_CAGED_HEAP
DijkstraMarkingBarrierSlowWithSentinelCheck(object);
#endif // !CPPGC_CAGED_HEAP
}
// static
void WriteBarrier::DijkstraMarkingBarrierRange(const Params& params,
const void* first_element,
size_t element_size,
size_t number_of_elements,
TraceCallback trace_callback) {
CheckParams(Type::kMarking, params);
DijkstraMarkingBarrierRangeSlow(*params.heap, first_element, element_size,
number_of_elements, trace_callback);
}
// static
void WriteBarrier::SteeleMarkingBarrier(const Params& params,
const void* object) {
CheckParams(Type::kMarking, params);
#if defined(CPPGC_CAGED_HEAP)
// Caged heap already filters out sentinels.
SteeleMarkingBarrierSlow(object);
#else // !CPPGC_CAGED_HEAP
SteeleMarkingBarrierSlowWithSentinelCheck(object);
#endif // !CPPGC_CAGED_HEAP
}
#if defined(CPPGC_YOUNG_GENERATION)
// static
template <WriteBarrier::GenerationalBarrierType type>
void WriteBarrier::GenerationalBarrier(const Params& params, const void* slot) {
CheckParams(Type::kGenerational, params);
const CagedHeapLocalData& local_data = CagedHeapLocalData::Get();
const AgeTable& age_table = local_data.age_table;
// Bail out if the slot (precise or imprecise) is in young generation.
if (V8_LIKELY(age_table.GetAge(params.slot_offset) == AgeTable::Age::kYoung))
return;
// Dispatch between different types of barriers.
// TODO(chromium:1029379): Consider reload local_data in the slow path to
// reduce register pressure.
if constexpr (type == GenerationalBarrierType::kPreciseSlot) {
GenerationalBarrierSlow(local_data, age_table, slot, params.value_offset,
params.heap);
} else if constexpr (type ==
GenerationalBarrierType::kPreciseUncompressedSlot) {
GenerationalBarrierForUncompressedSlotSlow(
local_data, age_table, slot, params.value_offset, params.heap);
} else {
GenerationalBarrierForSourceObjectSlow(local_data, slot, params.heap);
}
}
#endif // !CPPGC_YOUNG_GENERATION
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_WRITE_BARRIER_H_

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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_LIVENESS_BROKER_H_
#define INCLUDE_CPPGC_LIVENESS_BROKER_H_
#include "cppgc/heap.h"
#include "cppgc/member.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/trace-trait.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
class LivenessBrokerFactory;
} // namespace internal
/**
* The broker is passed to weak callbacks to allow (temporarily) querying
* the liveness state of an object. References to non-live objects must be
* cleared when `IsHeapObjectAlive()` returns false.
*
* \code
* class GCedWithCustomWeakCallback final
* : public GarbageCollected<GCedWithCustomWeakCallback> {
* public:
* UntracedMember<Bar> bar;
*
* void CustomWeakCallbackMethod(const LivenessBroker& broker) {
* if (!broker.IsHeapObjectAlive(bar))
* bar = nullptr;
* }
*
* void Trace(cppgc::Visitor* visitor) const {
* visitor->RegisterWeakCallbackMethod<
* GCedWithCustomWeakCallback,
* &GCedWithCustomWeakCallback::CustomWeakCallbackMethod>(this);
* }
* };
* \endcode
*/
class V8_EXPORT LivenessBroker final {
public:
template <typename T>
bool IsHeapObjectAlive(const T* object) const {
// - nullptr objects are considered alive to allow weakness to be used from
// stack while running into a conservative GC. Treating nullptr as dead
// would mean that e.g. custom collections could not be strongified on
// stack.
// - Sentinel pointers are also preserved in weakness and not cleared.
return !object || object == kSentinelPointer ||
IsHeapObjectAliveImpl(
TraceTrait<T>::GetTraceDescriptor(object).base_object_payload);
}
template <typename T>
bool IsHeapObjectAlive(const WeakMember<T>& weak_member) const {
return IsHeapObjectAlive<T>(weak_member.Get());
}
template <typename T>
bool IsHeapObjectAlive(const UntracedMember<T>& untraced_member) const {
return IsHeapObjectAlive<T>(untraced_member.Get());
}
private:
LivenessBroker() = default;
bool IsHeapObjectAliveImpl(const void*) const;
friend class internal::LivenessBrokerFactory;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_LIVENESS_BROKER_H_

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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_MACROS_H_
#define INCLUDE_CPPGC_MACROS_H_
#include <cstddef>
#include "cppgc/internal/compiler-specific.h"
namespace cppgc {
// Use CPPGC_STACK_ALLOCATED if the object is only stack allocated.
// Add the CPPGC_STACK_ALLOCATED_IGNORE annotation on a case-by-case basis when
// enforcement of CPPGC_STACK_ALLOCATED should be suppressed.
#if defined(__clang__)
#define CPPGC_STACK_ALLOCATED() \
public: \
using IsStackAllocatedTypeMarker CPPGC_UNUSED = int; \
\
private: \
void* operator new(size_t) = delete; \
void* operator new(size_t, void*) = delete; \
static_assert(true, "Force semicolon.")
#define CPPGC_STACK_ALLOCATED_IGNORE(bug_or_reason) \
__attribute__((annotate("stack_allocated_ignore")))
#else // !defined(__clang__)
#define CPPGC_STACK_ALLOCATED() static_assert(true, "Force semicolon.")
#define CPPGC_STACK_ALLOCATED_IGNORE(bug_or_reason)
#endif // !defined(__clang__)
} // namespace cppgc
#endif // INCLUDE_CPPGC_MACROS_H_

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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_MEMBER_H_
#define INCLUDE_CPPGC_MEMBER_H_
#include <atomic>
#include <cstddef>
#include <type_traits>
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/member-storage.h"
#include "cppgc/internal/pointer-policies.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/type-traits.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace subtle {
class HeapConsistency;
} // namespace subtle
class Visitor;
namespace internal {
// MemberBase always refers to the object as const object and defers to
// BasicMember on casting to the right type as needed.
template <typename StorageType>
class V8_TRIVIAL_ABI MemberBase {
public:
using RawStorage = StorageType;
protected:
struct AtomicInitializerTag {};
V8_INLINE MemberBase() = default;
V8_INLINE explicit MemberBase(const void* value) : raw_(value) {}
V8_INLINE MemberBase(const void* value, AtomicInitializerTag) {
SetRawAtomic(value);
}
V8_INLINE explicit MemberBase(RawStorage raw) : raw_(raw) {}
V8_INLINE explicit MemberBase(std::nullptr_t) : raw_(nullptr) {}
V8_INLINE explicit MemberBase(SentinelPointer s) : raw_(s) {}
V8_INLINE const void** GetRawSlot() const {
return reinterpret_cast<const void**>(const_cast<MemberBase*>(this));
}
V8_INLINE const void* GetRaw() const { return raw_.Load(); }
V8_INLINE void SetRaw(void* value) { raw_.Store(value); }
V8_INLINE const void* GetRawAtomic() const { return raw_.LoadAtomic(); }
V8_INLINE void SetRawAtomic(const void* value) { raw_.StoreAtomic(value); }
V8_INLINE RawStorage GetRawStorage() const { return raw_; }
V8_INLINE void SetRawStorageAtomic(RawStorage other) {
reinterpret_cast<std::atomic<RawStorage>&>(raw_).store(
other, std::memory_order_relaxed);
}
V8_INLINE bool IsCleared() const { return raw_.IsCleared(); }
V8_INLINE void ClearFromGC() const { raw_.Clear(); }
private:
friend class MemberDebugHelper;
mutable RawStorage raw_;
};
// The basic class from which all Member classes are 'generated'.
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
class V8_TRIVIAL_ABI BasicMember final : private MemberBase<StorageType>,
private CheckingPolicy {
using Base = MemberBase<StorageType>;
public:
using PointeeType = T;
using RawStorage = typename Base::RawStorage;
V8_INLINE constexpr BasicMember() = default;
V8_INLINE constexpr BasicMember(std::nullptr_t) {} // NOLINT
V8_INLINE BasicMember(SentinelPointer s) : Base(s) {} // NOLINT
V8_INLINE BasicMember(T* raw) : Base(raw) { // NOLINT
InitializingWriteBarrier(raw);
this->CheckPointer(Get());
}
V8_INLINE BasicMember(T& raw) // NOLINT
: BasicMember(&raw) {}
// Atomic ctor. Using the AtomicInitializerTag forces BasicMember to
// initialize using atomic assignments. This is required for preventing
// data races with concurrent marking.
using AtomicInitializerTag = typename Base::AtomicInitializerTag;
V8_INLINE BasicMember(std::nullptr_t, AtomicInitializerTag atomic)
: Base(nullptr, atomic) {}
V8_INLINE BasicMember(SentinelPointer s, AtomicInitializerTag atomic)
: Base(s, atomic) {}
V8_INLINE BasicMember(T* raw, AtomicInitializerTag atomic)
: Base(raw, atomic) {
InitializingWriteBarrier(raw);
this->CheckPointer(Get());
}
V8_INLINE BasicMember(T& raw, AtomicInitializerTag atomic)
: BasicMember(&raw, atomic) {}
// Copy ctor.
V8_INLINE BasicMember(const BasicMember& other)
: BasicMember(other.GetRawStorage()) {}
// Heterogeneous copy constructors. When the source pointer have a different
// type, perform a compress-decompress round, because the source pointer may
// need to be adjusted.
template <typename U, typename OtherBarrierPolicy, typename OtherWeaknessTag,
typename OtherCheckingPolicy,
std::enable_if_t<internal::IsDecayedSameV<T, U>>* = nullptr>
V8_INLINE BasicMember( // NOLINT
const BasicMember<U, OtherWeaknessTag, OtherBarrierPolicy,
OtherCheckingPolicy, StorageType>& other)
: BasicMember(other.GetRawStorage()) {}
template <typename U, typename OtherBarrierPolicy, typename OtherWeaknessTag,
typename OtherCheckingPolicy,
std::enable_if_t<internal::IsStrictlyBaseOfV<T, U>>* = nullptr>
V8_INLINE BasicMember( // NOLINT
const BasicMember<U, OtherWeaknessTag, OtherBarrierPolicy,
OtherCheckingPolicy, StorageType>& other)
: BasicMember(other.Get()) {}
// Move ctor.
V8_INLINE BasicMember(BasicMember&& other) noexcept
: BasicMember(other.GetRawStorage()) {
other.Clear();
}
// Heterogeneous move constructors. When the source pointer have a different
// type, perform a compress-decompress round, because the source pointer may
// need to be adjusted.
template <typename U, typename OtherBarrierPolicy, typename OtherWeaknessTag,
typename OtherCheckingPolicy,
std::enable_if_t<internal::IsDecayedSameV<T, U>>* = nullptr>
V8_INLINE BasicMember(
BasicMember<U, OtherWeaknessTag, OtherBarrierPolicy, OtherCheckingPolicy,
StorageType>&& other) noexcept
: BasicMember(other.GetRawStorage()) {
other.Clear();
}
template <typename U, typename OtherBarrierPolicy, typename OtherWeaknessTag,
typename OtherCheckingPolicy,
std::enable_if_t<internal::IsStrictlyBaseOfV<T, U>>* = nullptr>
V8_INLINE BasicMember(
BasicMember<U, OtherWeaknessTag, OtherBarrierPolicy, OtherCheckingPolicy,
StorageType>&& other) noexcept
: BasicMember(other.Get()) {
other.Clear();
}
// Construction from Persistent.
template <typename U, typename PersistentWeaknessPolicy,
typename PersistentLocationPolicy,
typename PersistentCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
V8_INLINE BasicMember(const BasicPersistent<U, PersistentWeaknessPolicy,
PersistentLocationPolicy,
PersistentCheckingPolicy>& p)
: BasicMember(p.Get()) {}
// Copy assignment.
V8_INLINE BasicMember& operator=(const BasicMember& other) {
return operator=(other.GetRawStorage());
}
// Heterogeneous copy assignment. When the source pointer have a different
// type, perform a compress-decompress round, because the source pointer may
// need to be adjusted.
template <typename U, typename OtherWeaknessTag, typename OtherBarrierPolicy,
typename OtherCheckingPolicy>
V8_INLINE BasicMember& operator=(
const BasicMember<U, OtherWeaknessTag, OtherBarrierPolicy,
OtherCheckingPolicy, StorageType>& other) {
if constexpr (internal::IsDecayedSameV<T, U>) {
return operator=(other.GetRawStorage());
} else {
static_assert(internal::IsStrictlyBaseOfV<T, U>);
return operator=(other.Get());
}
}
// Move assignment.
V8_INLINE BasicMember& operator=(BasicMember&& other) noexcept {
operator=(other.GetRawStorage());
other.Clear();
return *this;
}
// Heterogeneous move assignment. When the source pointer have a different
// type, perform a compress-decompress round, because the source pointer may
// need to be adjusted.
template <typename U, typename OtherWeaknessTag, typename OtherBarrierPolicy,
typename OtherCheckingPolicy>
V8_INLINE BasicMember& operator=(
BasicMember<U, OtherWeaknessTag, OtherBarrierPolicy, OtherCheckingPolicy,
StorageType>&& other) noexcept {
if constexpr (internal::IsDecayedSameV<T, U>) {
operator=(other.GetRawStorage());
} else {
static_assert(internal::IsStrictlyBaseOfV<T, U>);
operator=(other.Get());
}
other.Clear();
return *this;
}
// Assignment from Persistent.
template <typename U, typename PersistentWeaknessPolicy,
typename PersistentLocationPolicy,
typename PersistentCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
V8_INLINE BasicMember& operator=(
const BasicPersistent<U, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
other) {
return operator=(other.Get());
}
V8_INLINE BasicMember& operator=(T* other) {
Base::SetRawAtomic(other);
AssigningWriteBarrier(other);
this->CheckPointer(Get());
return *this;
}
V8_INLINE BasicMember& operator=(std::nullptr_t) {
Clear();
return *this;
}
V8_INLINE BasicMember& operator=(SentinelPointer s) {
Base::SetRawAtomic(s);
return *this;
}
template <typename OtherWeaknessTag, typename OtherBarrierPolicy,
typename OtherCheckingPolicy>
V8_INLINE void Swap(BasicMember<T, OtherWeaknessTag, OtherBarrierPolicy,
OtherCheckingPolicy, StorageType>& other) {
auto tmp = GetRawStorage();
*this = other;
other = tmp;
}
V8_INLINE explicit operator bool() const { return !Base::IsCleared(); }
V8_INLINE operator T*() const { return Get(); }
V8_INLINE T* operator->() const { return Get(); }
V8_INLINE T& operator*() const { return *Get(); }
// CFI cast exemption to allow passing SentinelPointer through T* and support
// heterogeneous assignments between different Member and Persistent handles
// based on their actual types.
V8_INLINE V8_CLANG_NO_SANITIZE("cfi-unrelated-cast") T* Get() const {
// Executed by the mutator, hence non atomic load.
//
// The const_cast below removes the constness from MemberBase storage. The
// following static_cast re-adds any constness if specified through the
// user-visible template parameter T.
return static_cast<T*>(const_cast<void*>(Base::GetRaw()));
}
V8_INLINE void Clear() {
Base::SetRawStorageAtomic(RawStorage{});
}
V8_INLINE T* Release() {
T* result = Get();
Clear();
return result;
}
V8_INLINE const T** GetSlotForTesting() const {
return reinterpret_cast<const T**>(Base::GetRawSlot());
}
V8_INLINE RawStorage GetRawStorage() const {
return Base::GetRawStorage();
}
private:
V8_INLINE explicit BasicMember(RawStorage raw) : Base(raw) {
InitializingWriteBarrier(Get());
this->CheckPointer(Get());
}
V8_INLINE BasicMember& operator=(RawStorage other) {
Base::SetRawStorageAtomic(other);
AssigningWriteBarrier();
this->CheckPointer(Get());
return *this;
}
V8_INLINE const T* GetRawAtomic() const {
return static_cast<const T*>(Base::GetRawAtomic());
}
V8_INLINE void InitializingWriteBarrier(T* value) const {
WriteBarrierPolicy::InitializingBarrier(Base::GetRawSlot(), value);
}
V8_INLINE void AssigningWriteBarrier(T* value) const {
WriteBarrierPolicy::template AssigningBarrier<
StorageType::kWriteBarrierSlotType>(Base::GetRawSlot(), value);
}
V8_INLINE void AssigningWriteBarrier() const {
WriteBarrierPolicy::template AssigningBarrier<
StorageType::kWriteBarrierSlotType>(Base::GetRawSlot(),
Base::GetRawStorage());
}
V8_INLINE void ClearFromGC() const { Base::ClearFromGC(); }
V8_INLINE T* GetFromGC() const { return Get(); }
friend class cppgc::subtle::HeapConsistency;
friend class cppgc::Visitor;
template <typename U>
friend struct cppgc::TraceTrait;
template <typename T1, typename WeaknessTag1, typename WriteBarrierPolicy1,
typename CheckingPolicy1, typename StorageType1>
friend class BasicMember;
};
// Member equality operators.
template <typename T1, typename WeaknessTag1, typename WriteBarrierPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessTag2,
typename WriteBarrierPolicy2, typename CheckingPolicy2,
typename StorageType>
V8_INLINE bool operator==(
const BasicMember<T1, WeaknessTag1, WriteBarrierPolicy1, CheckingPolicy1,
StorageType>& member1,
const BasicMember<T2, WeaknessTag2, WriteBarrierPolicy2, CheckingPolicy2,
StorageType>& member2) {
if constexpr (internal::IsDecayedSameV<T1, T2>) {
// Check compressed pointers if types are the same.
return member1.GetRawStorage() == member2.GetRawStorage();
} else {
static_assert(internal::IsStrictlyBaseOfV<T1, T2> ||
internal::IsStrictlyBaseOfV<T2, T1>);
// Otherwise, check decompressed pointers.
return member1.Get() == member2.Get();
}
}
template <typename T1, typename WeaknessTag1, typename WriteBarrierPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessTag2,
typename WriteBarrierPolicy2, typename CheckingPolicy2,
typename StorageType>
V8_INLINE bool operator!=(
const BasicMember<T1, WeaknessTag1, WriteBarrierPolicy1, CheckingPolicy1,
StorageType>& member1,
const BasicMember<T2, WeaknessTag2, WriteBarrierPolicy2, CheckingPolicy2,
StorageType>& member2) {
return !(member1 == member2);
}
// Equality with raw pointers.
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType, typename U>
V8_INLINE bool operator==(
const BasicMember<T, WeaknessTag, WriteBarrierPolicy, CheckingPolicy,
StorageType>& member,
U* raw) {
// Never allow comparison with erased pointers.
static_assert(!internal::IsDecayedSameV<void, U>);
if constexpr (internal::IsDecayedSameV<T, U>) {
// Check compressed pointers if types are the same.
return member.GetRawStorage() == StorageType(raw);
} else if constexpr (internal::IsStrictlyBaseOfV<T, U>) {
// Cast the raw pointer to T, which may adjust the pointer.
return member.GetRawStorage() == StorageType(static_cast<T*>(raw));
} else {
// Otherwise, decompressed the member.
return member.Get() == raw;
}
}
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType, typename U>
V8_INLINE bool operator!=(
const BasicMember<T, WeaknessTag, WriteBarrierPolicy, CheckingPolicy,
StorageType>& member,
U* raw) {
return !(member == raw);
}
template <typename T, typename U, typename WeaknessTag,
typename WriteBarrierPolicy, typename CheckingPolicy,
typename StorageType>
V8_INLINE bool operator==(
T* raw, const BasicMember<U, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& member) {
return member == raw;
}
template <typename T, typename U, typename WeaknessTag,
typename WriteBarrierPolicy, typename CheckingPolicy,
typename StorageType>
V8_INLINE bool operator!=(
T* raw, const BasicMember<U, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& member) {
return !(raw == member);
}
// Equality with sentinel.
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator==(
const BasicMember<T, WeaknessTag, WriteBarrierPolicy, CheckingPolicy,
StorageType>& member,
SentinelPointer) {
return member.GetRawStorage().IsSentinel();
}
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator!=(
const BasicMember<T, WeaknessTag, WriteBarrierPolicy, CheckingPolicy,
StorageType>& member,
SentinelPointer s) {
return !(member == s);
}
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator==(
SentinelPointer s, const BasicMember<T, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& member) {
return member == s;
}
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator!=(
SentinelPointer s, const BasicMember<T, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& member) {
return !(s == member);
}
// Equality with nullptr.
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator==(
const BasicMember<T, WeaknessTag, WriteBarrierPolicy, CheckingPolicy,
StorageType>& member,
std::nullptr_t) {
return !static_cast<bool>(member);
}
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator!=(
const BasicMember<T, WeaknessTag, WriteBarrierPolicy, CheckingPolicy,
StorageType>& member,
std::nullptr_t n) {
return !(member == n);
}
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator==(
std::nullptr_t n, const BasicMember<T, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& member) {
return member == n;
}
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
V8_INLINE bool operator!=(
std::nullptr_t n, const BasicMember<T, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& member) {
return !(n == member);
}
// Relational operators.
template <typename T1, typename WeaknessTag1, typename WriteBarrierPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessTag2,
typename WriteBarrierPolicy2, typename CheckingPolicy2,
typename StorageType>
V8_INLINE bool operator<(
const BasicMember<T1, WeaknessTag1, WriteBarrierPolicy1, CheckingPolicy1,
StorageType>& member1,
const BasicMember<T2, WeaknessTag2, WriteBarrierPolicy2, CheckingPolicy2,
StorageType>& member2) {
static_assert(
internal::IsDecayedSameV<T1, T2>,
"Comparison works only for same pointer type modulo cv-qualifiers");
return member1.GetRawStorage() < member2.GetRawStorage();
}
template <typename T1, typename WeaknessTag1, typename WriteBarrierPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessTag2,
typename WriteBarrierPolicy2, typename CheckingPolicy2,
typename StorageType>
V8_INLINE bool operator<=(
const BasicMember<T1, WeaknessTag1, WriteBarrierPolicy1, CheckingPolicy1,
StorageType>& member1,
const BasicMember<T2, WeaknessTag2, WriteBarrierPolicy2, CheckingPolicy2,
StorageType>& member2) {
static_assert(
internal::IsDecayedSameV<T1, T2>,
"Comparison works only for same pointer type modulo cv-qualifiers");
return member1.GetRawStorage() <= member2.GetRawStorage();
}
template <typename T1, typename WeaknessTag1, typename WriteBarrierPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessTag2,
typename WriteBarrierPolicy2, typename CheckingPolicy2,
typename StorageType>
V8_INLINE bool operator>(
const BasicMember<T1, WeaknessTag1, WriteBarrierPolicy1, CheckingPolicy1,
StorageType>& member1,
const BasicMember<T2, WeaknessTag2, WriteBarrierPolicy2, CheckingPolicy2,
StorageType>& member2) {
static_assert(
internal::IsDecayedSameV<T1, T2>,
"Comparison works only for same pointer type modulo cv-qualifiers");
return member1.GetRawStorage() > member2.GetRawStorage();
}
template <typename T1, typename WeaknessTag1, typename WriteBarrierPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessTag2,
typename WriteBarrierPolicy2, typename CheckingPolicy2,
typename StorageType>
V8_INLINE bool operator>=(
const BasicMember<T1, WeaknessTag1, WriteBarrierPolicy1, CheckingPolicy1,
StorageType>& member1,
const BasicMember<T2, WeaknessTag2, WriteBarrierPolicy2, CheckingPolicy2,
StorageType>& member2) {
static_assert(
internal::IsDecayedSameV<T1, T2>,
"Comparison works only for same pointer type modulo cv-qualifiers");
return member1.GetRawStorage() >= member2.GetRawStorage();
}
template <typename T, typename WriteBarrierPolicy, typename CheckingPolicy,
typename StorageType>
struct IsWeak<internal::BasicMember<T, WeakMemberTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>>
: std::true_type {};
} // namespace internal
/**
* Members are used in classes to contain strong pointers to other garbage
* collected objects. All Member fields of a class must be traced in the class'
* trace method.
*/
template <typename T>
using Member = internal::BasicMember<
T, internal::StrongMemberTag, internal::DijkstraWriteBarrierPolicy,
internal::DefaultMemberCheckingPolicy, internal::DefaultMemberStorage>;
/**
* WeakMember is similar to Member in that it is used to point to other garbage
* collected objects. However instead of creating a strong pointer to the
* object, the WeakMember creates a weak pointer, which does not keep the
* pointee alive. Hence if all pointers to to a heap allocated object are weak
* the object will be garbage collected. At the time of GC the weak pointers
* will automatically be set to null.
*/
template <typename T>
using WeakMember = internal::BasicMember<
T, internal::WeakMemberTag, internal::DijkstraWriteBarrierPolicy,
internal::DefaultMemberCheckingPolicy, internal::DefaultMemberStorage>;
/**
* UntracedMember is a pointer to an on-heap object that is not traced for some
* reason. Do not use this unless you know what you are doing. Keeping raw
* pointers to on-heap objects is prohibited unless used from stack. Pointee
* must be kept alive through other means.
*/
template <typename T>
using UntracedMember = internal::BasicMember<
T, internal::UntracedMemberTag, internal::NoWriteBarrierPolicy,
internal::DefaultMemberCheckingPolicy, internal::DefaultMemberStorage>;
namespace subtle {
/**
* UncompressedMember. Use with care in hot paths that would otherwise cause
* many decompression cycles.
*/
template <typename T>
using UncompressedMember = internal::BasicMember<
T, internal::StrongMemberTag, internal::DijkstraWriteBarrierPolicy,
internal::DefaultMemberCheckingPolicy, internal::RawPointer>;
} // namespace subtle
} // namespace cppgc
#endif // INCLUDE_CPPGC_MEMBER_H_

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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_NAME_PROVIDER_H_
#define INCLUDE_CPPGC_NAME_PROVIDER_H_
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
/**
* NameProvider allows for providing a human-readable name for garbage-collected
* objects.
*
* There's two cases of names to distinguish:
* a. Explicitly specified names via using NameProvider. Such names are always
* preserved in the system.
* b. Internal names that Oilpan infers from a C++ type on the class hierarchy
* of the object. This is not necessarily the type of the actually
* instantiated object.
*
* Depending on the build configuration, Oilpan may hide names, i.e., represent
* them with kHiddenName, of case b. to avoid exposing internal details.
*/
class V8_EXPORT NameProvider {
public:
/**
* Name that is used when hiding internals.
*/
static constexpr const char kHiddenName[] = "InternalNode";
/**
* Name that is used in case compiler support is missing for composing a name
* from C++ types.
*/
static constexpr const char kNoNameDeducible[] = "<No name>";
/**
* Indicating whether the build supports extracting C++ names as object names.
*
* @returns true if C++ names should be hidden and represented by kHiddenName.
*/
static constexpr bool SupportsCppClassNamesAsObjectNames() {
#if CPPGC_SUPPORTS_OBJECT_NAMES
return true;
#else // !CPPGC_SUPPORTS_OBJECT_NAMES
return false;
#endif // !CPPGC_SUPPORTS_OBJECT_NAMES
}
virtual ~NameProvider() = default;
/**
* Specifies a name for the garbage-collected object. Such names will never
* be hidden, as they are explicitly specified by the user of this API.
*
* @returns a human readable name for the object.
*/
virtual const char* GetHumanReadableName() const = 0;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_NAME_PROVIDER_H_

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// Copyright 2021 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_OBJECT_SIZE_TRAIT_H_
#define INCLUDE_CPPGC_OBJECT_SIZE_TRAIT_H_
#include <cstddef>
#include "cppgc/type-traits.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
struct V8_EXPORT BaseObjectSizeTrait {
protected:
static size_t GetObjectSizeForGarbageCollected(const void*);
static size_t GetObjectSizeForGarbageCollectedMixin(const void*);
};
} // namespace internal
namespace subtle {
/**
* Trait specifying how to get the size of an object that was allocated using
* `MakeGarbageCollected()`. Also supports querying the size with an inner
* pointer to a mixin.
*/
template <typename T, bool = IsGarbageCollectedMixinTypeV<T>>
struct ObjectSizeTrait;
template <typename T>
struct ObjectSizeTrait<T, false> : cppgc::internal::BaseObjectSizeTrait {
static_assert(sizeof(T), "T must be fully defined");
static_assert(IsGarbageCollectedTypeV<T>,
"T must be of type GarbageCollected or GarbageCollectedMixin");
static size_t GetSize(const T& object) {
return GetObjectSizeForGarbageCollected(&object);
}
};
template <typename T>
struct ObjectSizeTrait<T, true> : cppgc::internal::BaseObjectSizeTrait {
static_assert(sizeof(T), "T must be fully defined");
static size_t GetSize(const T& object) {
return GetObjectSizeForGarbageCollectedMixin(&object);
}
};
} // namespace subtle
} // namespace cppgc
#endif // INCLUDE_CPPGC_OBJECT_SIZE_TRAIT_H_

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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_PERSISTENT_H_
#define INCLUDE_CPPGC_PERSISTENT_H_
#include <type_traits>
#include "cppgc/internal/persistent-node.h"
#include "cppgc/internal/pointer-policies.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/source-location.h"
#include "cppgc/type-traits.h"
#include "cppgc/visitor.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
// PersistentBase always refers to the object as const object and defers to
// BasicPersistent on casting to the right type as needed.
class PersistentBase {
protected:
PersistentBase() = default;
explicit PersistentBase(const void* raw) : raw_(raw) {}
const void* GetValue() const { return raw_; }
void SetValue(const void* value) { raw_ = value; }
PersistentNode* GetNode() const { return node_; }
void SetNode(PersistentNode* node) { node_ = node; }
// Performs a shallow clear which assumes that internal persistent nodes are
// destroyed elsewhere.
void ClearFromGC() const {
raw_ = nullptr;
node_ = nullptr;
}
protected:
mutable const void* raw_ = nullptr;
mutable PersistentNode* node_ = nullptr;
friend class PersistentRegionBase;
};
// The basic class from which all Persistent classes are generated.
template <typename T, typename WeaknessPolicy, typename LocationPolicy,
typename CheckingPolicy>
class BasicPersistent final : public PersistentBase,
public LocationPolicy,
private WeaknessPolicy,
private CheckingPolicy {
public:
using typename WeaknessPolicy::IsStrongPersistent;
using PointeeType = T;
// Null-state/sentinel constructors.
BasicPersistent( // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: LocationPolicy(loc) {}
BasicPersistent(std::nullptr_t, // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: LocationPolicy(loc) {}
BasicPersistent( // NOLINT
SentinelPointer s, const SourceLocation& loc = SourceLocation::Current())
: PersistentBase(s), LocationPolicy(loc) {}
// Raw value constructors.
BasicPersistent(T* raw, // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: PersistentBase(raw), LocationPolicy(loc) {
if (!IsValid()) return;
SetNode(WeaknessPolicy::GetPersistentRegion(GetValue())
.AllocateNode(this, &TraceAsRoot));
this->CheckPointer(Get());
}
BasicPersistent(T& raw, // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(&raw, loc) {}
// Copy ctor.
BasicPersistent(const BasicPersistent& other,
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(other.Get(), loc) {}
// Heterogeneous ctor.
template <typename U, typename OtherWeaknessPolicy,
typename OtherLocationPolicy, typename OtherCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicPersistent(
const BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>& other,
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(other.Get(), loc) {}
// Move ctor. The heterogeneous move ctor is not supported since e.g.
// persistent can't reuse persistent node from weak persistent.
BasicPersistent(
BasicPersistent&& other,
const SourceLocation& loc = SourceLocation::Current()) noexcept
: PersistentBase(std::move(other)), LocationPolicy(std::move(other)) {
if (!IsValid()) return;
GetNode()->UpdateOwner(this);
other.SetValue(nullptr);
other.SetNode(nullptr);
this->CheckPointer(Get());
}
// Constructor from member.
template <typename U, typename MemberBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicPersistent(const internal::BasicMember<
U, MemberBarrierPolicy, MemberWeaknessTag,
MemberCheckingPolicy, MemberStorageType>& member,
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(member.Get(), loc) {}
~BasicPersistent() { Clear(); }
// Copy assignment.
BasicPersistent& operator=(const BasicPersistent& other) {
return operator=(other.Get());
}
template <typename U, typename OtherWeaknessPolicy,
typename OtherLocationPolicy, typename OtherCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicPersistent& operator=(
const BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>& other) {
return operator=(other.Get());
}
// Move assignment.
BasicPersistent& operator=(BasicPersistent&& other) noexcept {
if (this == &other) return *this;
Clear();
PersistentBase::operator=(std::move(other));
LocationPolicy::operator=(std::move(other));
if (!IsValid()) return *this;
GetNode()->UpdateOwner(this);
other.SetValue(nullptr);
other.SetNode(nullptr);
this->CheckPointer(Get());
return *this;
}
// Assignment from member.
template <typename U, typename MemberBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicPersistent& operator=(
const internal::BasicMember<U, MemberBarrierPolicy, MemberWeaknessTag,
MemberCheckingPolicy, MemberStorageType>&
member) {
return operator=(member.Get());
}
BasicPersistent& operator=(T* other) {
Assign(other);
return *this;
}
BasicPersistent& operator=(std::nullptr_t) {
Clear();
return *this;
}
BasicPersistent& operator=(SentinelPointer s) {
Assign(s);
return *this;
}
explicit operator bool() const { return Get(); }
operator T*() const { return Get(); }
T* operator->() const { return Get(); }
T& operator*() const { return *Get(); }
// CFI cast exemption to allow passing SentinelPointer through T* and support
// heterogeneous assignments between different Member and Persistent handles
// based on their actual types.
V8_CLANG_NO_SANITIZE("cfi-unrelated-cast") T* Get() const {
// The const_cast below removes the constness from PersistentBase storage.
// The following static_cast re-adds any constness if specified through the
// user-visible template parameter T.
return static_cast<T*>(const_cast<void*>(GetValue()));
}
void Clear() {
// Simplified version of `Assign()` to allow calling without a complete type
// `T`.
if (IsValid()) {
WeaknessPolicy::GetPersistentRegion(GetValue()).FreeNode(GetNode());
SetNode(nullptr);
}
SetValue(nullptr);
}
T* Release() {
T* result = Get();
Clear();
return result;
}
template <typename U, typename OtherWeaknessPolicy = WeaknessPolicy,
typename OtherLocationPolicy = LocationPolicy,
typename OtherCheckingPolicy = CheckingPolicy>
BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>
To() const {
return BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>(static_cast<U*>(Get()));
}
private:
static void TraceAsRoot(RootVisitor& root_visitor, const void* ptr) {
root_visitor.Trace(*static_cast<const BasicPersistent*>(ptr));
}
bool IsValid() const {
// Ideally, handling kSentinelPointer would be done by the embedder. On the
// other hand, having Persistent aware of it is beneficial since no node
// gets wasted.
return GetValue() != nullptr && GetValue() != kSentinelPointer;
}
void Assign(T* ptr) {
if (IsValid()) {
if (ptr && ptr != kSentinelPointer) {
// Simply assign the pointer reusing the existing node.
SetValue(ptr);
this->CheckPointer(ptr);
return;
}
WeaknessPolicy::GetPersistentRegion(GetValue()).FreeNode(GetNode());
SetNode(nullptr);
}
SetValue(ptr);
if (!IsValid()) return;
SetNode(WeaknessPolicy::GetPersistentRegion(GetValue())
.AllocateNode(this, &TraceAsRoot));
this->CheckPointer(Get());
}
void ClearFromGC() const {
if (IsValid()) {
WeaknessPolicy::GetPersistentRegion(GetValue()).FreeNode(GetNode());
PersistentBase::ClearFromGC();
}
}
// Set Get() for details.
V8_CLANG_NO_SANITIZE("cfi-unrelated-cast")
T* GetFromGC() const {
return static_cast<T*>(const_cast<void*>(GetValue()));
}
friend class internal::RootVisitor;
};
template <typename T1, typename WeaknessPolicy1, typename LocationPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessPolicy2,
typename LocationPolicy2, typename CheckingPolicy2>
bool operator==(const BasicPersistent<T1, WeaknessPolicy1, LocationPolicy1,
CheckingPolicy1>& p1,
const BasicPersistent<T2, WeaknessPolicy2, LocationPolicy2,
CheckingPolicy2>& p2) {
return p1.Get() == p2.Get();
}
template <typename T1, typename WeaknessPolicy1, typename LocationPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessPolicy2,
typename LocationPolicy2, typename CheckingPolicy2>
bool operator!=(const BasicPersistent<T1, WeaknessPolicy1, LocationPolicy1,
CheckingPolicy1>& p1,
const BasicPersistent<T2, WeaknessPolicy2, LocationPolicy2,
CheckingPolicy2>& p2) {
return !(p1 == p2);
}
template <typename T1, typename PersistentWeaknessPolicy,
typename PersistentLocationPolicy, typename PersistentCheckingPolicy,
typename T2, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType>
bool operator==(
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p,
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m) {
return p.Get() == m.Get();
}
template <typename T1, typename PersistentWeaknessPolicy,
typename PersistentLocationPolicy, typename PersistentCheckingPolicy,
typename T2, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType>
bool operator!=(
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p,
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m) {
return !(p == m);
}
template <typename T1, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType, typename T2,
typename PersistentWeaknessPolicy, typename PersistentLocationPolicy,
typename PersistentCheckingPolicy>
bool operator==(
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m,
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p) {
return m.Get() == p.Get();
}
template <typename T1, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType, typename T2,
typename PersistentWeaknessPolicy, typename PersistentLocationPolicy,
typename PersistentCheckingPolicy>
bool operator!=(
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m,
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p) {
return !(m == p);
}
template <typename T, typename LocationPolicy, typename CheckingPolicy>
struct IsWeak<BasicPersistent<T, internal::WeakPersistentPolicy, LocationPolicy,
CheckingPolicy>> : std::true_type {};
} // namespace internal
/**
* Persistent is a way to create a strong pointer from an off-heap object to
* another on-heap object. As long as the Persistent handle is alive the GC will
* keep the object pointed to alive. The Persistent handle is always a GC root
* from the point of view of the GC. Persistent must be constructed and
* destructed in the same thread.
*/
template <typename T>
using Persistent =
internal::BasicPersistent<T, internal::StrongPersistentPolicy>;
/**
* WeakPersistent is a way to create a weak pointer from an off-heap object to
* an on-heap object. The pointer is automatically cleared when the pointee gets
* collected. WeakPersistent must be constructed and destructed in the same
* thread.
*/
template <typename T>
using WeakPersistent =
internal::BasicPersistent<T, internal::WeakPersistentPolicy>;
} // namespace cppgc
#endif // INCLUDE_CPPGC_PERSISTENT_H_

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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_PLATFORM_H_
#define INCLUDE_CPPGC_PLATFORM_H_
#include <memory>
#include "cppgc/source-location.h"
#include "v8-platform.h" // NOLINT(build/include_directory)
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
// TODO(v8:10346): Create separate includes for concepts that are not
// V8-specific.
using IdleTask = v8::IdleTask;
using JobHandle = v8::JobHandle;
using JobDelegate = v8::JobDelegate;
using JobTask = v8::JobTask;
using PageAllocator = v8::PageAllocator;
using Task = v8::Task;
using TaskPriority = v8::TaskPriority;
using TaskRunner = v8::TaskRunner;
using TracingController = v8::TracingController;
/**
* Platform interface used by Heap. Contains allocators and executors.
*/
class V8_EXPORT Platform {
public:
virtual ~Platform() = default;
/**
* \returns the allocator used by cppgc to allocate its heap and various
* support structures. Returning nullptr results in using the `PageAllocator`
* provided by `cppgc::InitializeProcess()` instead.
*/
virtual PageAllocator* GetPageAllocator() = 0;
/**
* Monotonically increasing time in seconds from an arbitrary fixed point in
* the past. This function is expected to return at least
* millisecond-precision values. For this reason,
* it is recommended that the fixed point be no further in the past than
* the epoch.
**/
virtual double MonotonicallyIncreasingTime() = 0;
/**
* Foreground task runner that should be used by a Heap.
*/
virtual std::shared_ptr<TaskRunner> GetForegroundTaskRunner() {
return nullptr;
}
/**
* Posts `job_task` to run in parallel. Returns a `JobHandle` associated with
* the `Job`, which can be joined or canceled.
* This avoids degenerate cases:
* - Calling `CallOnWorkerThread()` for each work item, causing significant
* overhead.
* - Fixed number of `CallOnWorkerThread()` calls that split the work and
* might run for a long time. This is problematic when many components post
* "num cores" tasks and all expect to use all the cores. In these cases,
* the scheduler lacks context to be fair to multiple same-priority requests
* and/or ability to request lower priority work to yield when high priority
* work comes in.
* A canonical implementation of `job_task` looks like:
* \code
* class MyJobTask : public JobTask {
* public:
* MyJobTask(...) : worker_queue_(...) {}
* // JobTask implementation.
* void Run(JobDelegate* delegate) override {
* while (!delegate->ShouldYield()) {
* // Smallest unit of work.
* auto work_item = worker_queue_.TakeWorkItem(); // Thread safe.
* if (!work_item) return;
* ProcessWork(work_item);
* }
* }
*
* size_t GetMaxConcurrency() const override {
* return worker_queue_.GetSize(); // Thread safe.
* }
* };
*
* // ...
* auto handle = PostJob(TaskPriority::kUserVisible,
* std::make_unique<MyJobTask>(...));
* handle->Join();
* \endcode
*
* `PostJob()` and methods of the returned JobHandle/JobDelegate, must never
* be called while holding a lock that could be acquired by `JobTask::Run()`
* or `JobTask::GetMaxConcurrency()` -- that could result in a deadlock. This
* is because (1) `JobTask::GetMaxConcurrency()` may be invoked while holding
* internal lock (A), hence `JobTask::GetMaxConcurrency()` can only use a lock
* (B) if that lock is *never* held while calling back into `JobHandle` from
* any thread (A=>B/B=>A deadlock) and (2) `JobTask::Run()` or
* `JobTask::GetMaxConcurrency()` may be invoked synchronously from
* `JobHandle` (B=>JobHandle::foo=>B deadlock).
*
* A sufficient `PostJob()` implementation that uses the default Job provided
* in libplatform looks like:
* \code
* std::unique_ptr<JobHandle> PostJob(
* TaskPriority priority, std::unique_ptr<JobTask> job_task) override {
* return std::make_unique<DefaultJobHandle>(
* std::make_shared<DefaultJobState>(
* this, std::move(job_task), kNumThreads));
* }
* \endcode
*/
virtual std::unique_ptr<JobHandle> PostJob(
TaskPriority priority, std::unique_ptr<JobTask> job_task) {
return nullptr;
}
/**
* Returns an instance of a `TracingController`. This must be non-nullptr. The
* default implementation returns an empty `TracingController` that consumes
* trace data without effect.
*/
virtual TracingController* GetTracingController();
};
/**
* Process-global initialization of the garbage collector. Must be called before
* creating a Heap.
*
* Can be called multiple times when paired with `ShutdownProcess()`.
*
* \param page_allocator The allocator used for maintaining meta data. Must stay
* always alive and not change between multiple calls to InitializeProcess. If
* no allocator is provided, a default internal version will be used.
*/
V8_EXPORT void InitializeProcess(PageAllocator* page_allocator = nullptr);
/**
* Must be called after destroying the last used heap. Some process-global
* metadata may not be returned and reused upon a subsequent
* `InitializeProcess()` call.
*/
V8_EXPORT void ShutdownProcess();
namespace internal {
V8_EXPORT void Fatal(const std::string& reason = std::string(),
const SourceLocation& = SourceLocation::Current());
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_PLATFORM_H_

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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_PREFINALIZER_H_
#define INCLUDE_CPPGC_PREFINALIZER_H_
#include "cppgc/internal/compiler-specific.h"
#include "cppgc/liveness-broker.h"
namespace cppgc {
namespace internal {
class V8_EXPORT PrefinalizerRegistration final {
public:
using Callback = bool (*)(const cppgc::LivenessBroker&, void*);
PrefinalizerRegistration(void*, Callback);
void* operator new(size_t, void* location) = delete;
void* operator new(size_t) = delete;
};
} // namespace internal
/**
* Macro must be used in the private section of `Class` and registers a
* prefinalization callback `void Class::PreFinalizer()`. The callback is
* invoked on garbage collection after the collector has found an object to be
* dead.
*
* Callback properties:
* - The callback is invoked before a possible destructor for the corresponding
* object.
* - The callback may access the whole object graph, irrespective of whether
* objects are considered dead or alive.
* - The callback is invoked on the same thread as the object was created on.
*
* Example:
* \code
* class WithPrefinalizer : public GarbageCollected<WithPrefinalizer> {
* CPPGC_USING_PRE_FINALIZER(WithPrefinalizer, Dispose);
*
* public:
* void Trace(Visitor*) const {}
* void Dispose() { prefinalizer_called = true; }
* ~WithPrefinalizer() {
* // prefinalizer_called == true
* }
* private:
* bool prefinalizer_called = false;
* };
* \endcode
*/
#define CPPGC_USING_PRE_FINALIZER(Class, PreFinalizer) \
public: \
static bool InvokePreFinalizer(const cppgc::LivenessBroker& liveness_broker, \
void* object) { \
static_assert(cppgc::IsGarbageCollectedOrMixinTypeV<Class>, \
"Only garbage collected objects can have prefinalizers"); \
Class* self = static_cast<Class*>(object); \
if (liveness_broker.IsHeapObjectAlive(self)) return false; \
self->PreFinalizer(); \
return true; \
} \
\
private: \
CPPGC_NO_UNIQUE_ADDRESS cppgc::internal::PrefinalizerRegistration \
prefinalizer_dummy_{this, Class::InvokePreFinalizer}; \
static_assert(true, "Force semicolon.")
} // namespace cppgc
#endif // INCLUDE_CPPGC_PREFINALIZER_H_

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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_PROCESS_HEAP_STATISTICS_H_
#define INCLUDE_CPPGC_PROCESS_HEAP_STATISTICS_H_
#include <atomic>
#include <cstddef>
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
class ProcessHeapStatisticsUpdater;
} // namespace internal
class V8_EXPORT ProcessHeapStatistics final {
public:
static size_t TotalAllocatedObjectSize() {
return total_allocated_object_size_.load(std::memory_order_relaxed);
}
static size_t TotalAllocatedSpace() {
return total_allocated_space_.load(std::memory_order_relaxed);
}
private:
static std::atomic_size_t total_allocated_space_;
static std::atomic_size_t total_allocated_object_size_;
friend class internal::ProcessHeapStatisticsUpdater;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_PROCESS_HEAP_STATISTICS_H_

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// Copyright 2021 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_SENTINEL_POINTER_H_
#define INCLUDE_CPPGC_SENTINEL_POINTER_H_
#include <cstdint>
namespace cppgc {
namespace internal {
// Special tag type used to denote some sentinel member. The semantics of the
// sentinel is defined by the embedder.
struct SentinelPointer {
static constexpr intptr_t kSentinelValue = 0b10;
template <typename T>
operator T*() const {
return reinterpret_cast<T*>(kSentinelValue);
}
// Hidden friends.
friend bool operator==(SentinelPointer, SentinelPointer) { return true; }
friend bool operator!=(SentinelPointer, SentinelPointer) { return false; }
};
} // namespace internal
constexpr internal::SentinelPointer kSentinelPointer;
} // namespace cppgc
#endif // INCLUDE_CPPGC_SENTINEL_POINTER_H_

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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_SOURCE_LOCATION_H_
#define INCLUDE_CPPGC_SOURCE_LOCATION_H_
#include <cstddef>
#include <string>
#include "v8config.h" // NOLINT(build/include_directory)
#if defined(__has_builtin)
#define CPPGC_SUPPORTS_SOURCE_LOCATION \
(__has_builtin(__builtin_FUNCTION) && __has_builtin(__builtin_FILE) && \
__has_builtin(__builtin_LINE)) // NOLINT
#elif defined(V8_CC_GNU) && __GNUC__ >= 7
#define CPPGC_SUPPORTS_SOURCE_LOCATION 1
#elif defined(V8_CC_INTEL) && __ICC >= 1800
#define CPPGC_SUPPORTS_SOURCE_LOCATION 1
#else
#define CPPGC_SUPPORTS_SOURCE_LOCATION 0
#endif
namespace cppgc {
/**
* Encapsulates source location information. Mimics C++20's
* `std::source_location`.
*/
class V8_EXPORT SourceLocation final {
public:
/**
* Construct source location information corresponding to the location of the
* call site.
*/
#if CPPGC_SUPPORTS_SOURCE_LOCATION
static constexpr SourceLocation Current(
const char* function = __builtin_FUNCTION(),
const char* file = __builtin_FILE(), size_t line = __builtin_LINE()) {
return SourceLocation(function, file, line);
}
#else
static constexpr SourceLocation Current() { return SourceLocation(); }
#endif // CPPGC_SUPPORTS_SOURCE_LOCATION
/**
* Constructs unspecified source location information.
*/
constexpr SourceLocation() = default;
/**
* Returns the name of the function associated with the position represented
* by this object, if any.
*
* \returns the function name as cstring.
*/
constexpr const char* Function() const { return function_; }
/**
* Returns the name of the current source file represented by this object.
*
* \returns the file name as cstring.
*/
constexpr const char* FileName() const { return file_; }
/**
* Returns the line number represented by this object.
*
* \returns the line number.
*/
constexpr size_t Line() const { return line_; }
/**
* Returns a human-readable string representing this object.
*
* \returns a human-readable string representing source location information.
*/
std::string ToString() const;
private:
constexpr SourceLocation(const char* function, const char* file, size_t line)
: function_(function), file_(file), line_(line) {}
const char* function_ = nullptr;
const char* file_ = nullptr;
size_t line_ = 0u;
};
} // namespace cppgc
#endif // INCLUDE_CPPGC_SOURCE_LOCATION_H_

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// Copyright 2021 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_TESTING_H_
#define INCLUDE_CPPGC_TESTING_H_
#include "cppgc/common.h"
#include "cppgc/macros.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
class HeapHandle;
/**
* Namespace contains testing helpers.
*/
namespace testing {
/**
* Overrides the state of the stack with the provided value. Parameters passed
* to explicit garbage collection calls still take precedence. Must not be
* nested.
*
* This scope is useful to make the garbage collector consider the stack when
* tasks that invoke garbage collection (through the provided platform) contain
* interesting pointers on its stack.
*/
class V8_EXPORT V8_NODISCARD OverrideEmbedderStackStateScope final {
CPPGC_STACK_ALLOCATED();
public:
/**
* Constructs a scoped object that automatically enters and leaves the scope.
*
* \param heap_handle The corresponding heap.
*/
explicit OverrideEmbedderStackStateScope(HeapHandle& heap_handle,
EmbedderStackState state);
~OverrideEmbedderStackStateScope();
OverrideEmbedderStackStateScope(const OverrideEmbedderStackStateScope&) =
delete;
OverrideEmbedderStackStateScope& operator=(
const OverrideEmbedderStackStateScope&) = delete;
private:
HeapHandle& heap_handle_;
};
/**
* Testing interface for managed heaps that allows for controlling garbage
* collection timings. Embedders should use this class when testing the
* interaction of their code with incremental/concurrent garbage collection.
*/
class V8_EXPORT StandaloneTestingHeap final {
public:
explicit StandaloneTestingHeap(HeapHandle&);
/**
* Start an incremental garbage collection.
*/
void StartGarbageCollection();
/**
* Perform an incremental step. This will also schedule concurrent steps if
* needed.
*
* \param stack_state The state of the stack during the step.
*/
bool PerformMarkingStep(EmbedderStackState stack_state);
/**
* Finalize the current garbage collection cycle atomically.
* Assumes that garbage collection is in progress.
*
* \param stack_state The state of the stack for finalizing the garbage
* collection cycle.
*/
void FinalizeGarbageCollection(EmbedderStackState stack_state);
/**
* Toggle main thread marking on/off. Allows to stress concurrent marking
* (e.g. to better detect data races).
*
* \param should_mark Denotes whether the main thread should contribute to
* marking. Defaults to true.
*/
void ToggleMainThreadMarking(bool should_mark);
/**
* Force enable compaction for the next garbage collection cycle.
*/
void ForceCompactionForNextGarbageCollection();
private:
HeapHandle& heap_handle_;
};
V8_EXPORT bool IsHeapObjectOld(void*);
} // namespace testing
} // namespace cppgc
#endif // INCLUDE_CPPGC_TESTING_H_

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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_TRACE_TRAIT_H_
#define INCLUDE_CPPGC_TRACE_TRAIT_H_
#include <type_traits>
#include "cppgc/type-traits.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
class Visitor;
namespace internal {
class RootVisitor;
using TraceRootCallback = void (*)(RootVisitor&, const void* object);
// Implementation of the default TraceTrait handling GarbageCollected and
// GarbageCollectedMixin.
template <typename T,
bool =
IsGarbageCollectedMixinTypeV<typename std::remove_const<T>::type>>
struct TraceTraitImpl;
} // namespace internal
/**
* Callback for invoking tracing on a given object.
*
* \param visitor The visitor to dispatch to.
* \param object The object to invoke tracing on.
*/
using TraceCallback = void (*)(Visitor* visitor, const void* object);
/**
* Describes how to trace an object, i.e., how to visit all Oilpan-relevant
* fields of an object.
*/
struct TraceDescriptor {
/**
* Adjusted base pointer, i.e., the pointer to the class inheriting directly
* from GarbageCollected, of the object that is being traced.
*/
const void* base_object_payload;
/**
* Callback for tracing the object.
*/
TraceCallback callback;
};
namespace internal {
struct V8_EXPORT TraceTraitFromInnerAddressImpl {
static TraceDescriptor GetTraceDescriptor(const void* address);
};
/**
* Trait specifying how the garbage collector processes an object of type T.
*
* Advanced users may override handling by creating a specialization for their
* type.
*/
template <typename T>
struct TraceTraitBase {
static_assert(internal::IsTraceableV<T>, "T must have a Trace() method");
/**
* Accessor for retrieving a TraceDescriptor to process an object of type T.
*
* \param self The object to be processed.
* \returns a TraceDescriptor to process the object.
*/
static TraceDescriptor GetTraceDescriptor(const void* self) {
return internal::TraceTraitImpl<T>::GetTraceDescriptor(
static_cast<const T*>(self));
}
/**
* Function invoking the tracing for an object of type T.
*
* \param visitor The visitor to dispatch to.
* \param self The object to invoke tracing on.
*/
static void Trace(Visitor* visitor, const void* self) {
static_cast<const T*>(self)->Trace(visitor);
}
};
} // namespace internal
template <typename T>
struct TraceTrait : public internal::TraceTraitBase<T> {};
namespace internal {
template <typename T>
struct TraceTraitImpl<T, false> {
static_assert(IsGarbageCollectedTypeV<T>,
"T must be of type GarbageCollected or GarbageCollectedMixin");
static TraceDescriptor GetTraceDescriptor(const void* self) {
return {self, TraceTrait<T>::Trace};
}
};
template <typename T>
struct TraceTraitImpl<T, true> {
static TraceDescriptor GetTraceDescriptor(const void* self) {
return internal::TraceTraitFromInnerAddressImpl::GetTraceDescriptor(self);
}
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_TRACE_TRAIT_H_

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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_TYPE_TRAITS_H_
#define INCLUDE_CPPGC_TYPE_TRAITS_H_
// This file should stay with minimal dependencies to allow embedder to check
// against Oilpan types without including any other parts.
#include <cstddef>
#include <type_traits>
namespace cppgc {
class Visitor;
namespace internal {
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
class BasicMember;
struct DijkstraWriteBarrierPolicy;
struct NoWriteBarrierPolicy;
class StrongMemberTag;
class UntracedMemberTag;
class WeakMemberTag;
// Not supposed to be specialized by the user.
template <typename T>
struct IsWeak : std::false_type {};
// IsTraceMethodConst is used to verify that all Trace methods are marked as
// const. It is equivalent to IsTraceable but for a non-const object.
template <typename T, typename = void>
struct IsTraceMethodConst : std::false_type {};
template <typename T>
struct IsTraceMethodConst<T, std::void_t<decltype(std::declval<const T>().Trace(
std::declval<Visitor*>()))>> : std::true_type {
};
template <typename T, typename = void>
struct IsTraceable : std::false_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T>
struct IsTraceable<
T, std::void_t<decltype(std::declval<T>().Trace(std::declval<Visitor*>()))>>
: std::true_type {
// All Trace methods should be marked as const. If an object of type
// 'T' is traceable then any object of type 'const T' should also
// be traceable.
static_assert(IsTraceMethodConst<T>(),
"Trace methods should be marked as const.");
};
template <typename T>
constexpr bool IsTraceableV = IsTraceable<T>::value;
template <typename T, typename = void>
struct HasGarbageCollectedMixinTypeMarker : std::false_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T>
struct HasGarbageCollectedMixinTypeMarker<
T, std::void_t<
typename std::remove_const_t<T>::IsGarbageCollectedMixinTypeMarker>>
: std::true_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T, typename = void>
struct HasGarbageCollectedTypeMarker : std::false_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T>
struct HasGarbageCollectedTypeMarker<
T,
std::void_t<typename std::remove_const_t<T>::IsGarbageCollectedTypeMarker>>
: std::true_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T, bool = HasGarbageCollectedTypeMarker<T>::value,
bool = HasGarbageCollectedMixinTypeMarker<T>::value>
struct IsGarbageCollectedMixinType : std::false_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T>
struct IsGarbageCollectedMixinType<T, false, true> : std::true_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T, bool = HasGarbageCollectedTypeMarker<T>::value>
struct IsGarbageCollectedType : std::false_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T>
struct IsGarbageCollectedType<T, true> : std::true_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T>
struct IsGarbageCollectedOrMixinType
: std::integral_constant<bool, IsGarbageCollectedType<T>::value ||
IsGarbageCollectedMixinType<T>::value> {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T, bool = (HasGarbageCollectedTypeMarker<T>::value &&
HasGarbageCollectedMixinTypeMarker<T>::value)>
struct IsGarbageCollectedWithMixinType : std::false_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename T>
struct IsGarbageCollectedWithMixinType<T, true> : std::true_type {
static_assert(sizeof(T), "T must be fully defined");
};
template <typename BasicMemberCandidate, typename WeaknessTag,
typename WriteBarrierPolicy>
struct IsSubclassOfBasicMemberTemplate {
private:
template <typename T, typename CheckingPolicy, typename StorageType>
static std::true_type SubclassCheck(
BasicMember<T, WeaknessTag, WriteBarrierPolicy, CheckingPolicy,
StorageType>*);
static std::false_type SubclassCheck(...);
public:
static constexpr bool value =
decltype(SubclassCheck(std::declval<BasicMemberCandidate*>()))::value;
};
template <typename T,
bool = IsSubclassOfBasicMemberTemplate<
T, StrongMemberTag, DijkstraWriteBarrierPolicy>::value>
struct IsMemberType : std::false_type {};
template <typename T>
struct IsMemberType<T, true> : std::true_type {};
template <typename T, bool = IsSubclassOfBasicMemberTemplate<
T, WeakMemberTag, DijkstraWriteBarrierPolicy>::value>
struct IsWeakMemberType : std::false_type {};
template <typename T>
struct IsWeakMemberType<T, true> : std::true_type {};
template <typename T, bool = IsSubclassOfBasicMemberTemplate<
T, UntracedMemberTag, NoWriteBarrierPolicy>::value>
struct IsUntracedMemberType : std::false_type {};
template <typename T>
struct IsUntracedMemberType<T, true> : std::true_type {};
template <typename T>
struct IsComplete {
private:
template <typename U, size_t = sizeof(U)>
static std::true_type IsSizeOfKnown(U*);
static std::false_type IsSizeOfKnown(...);
public:
static constexpr bool value =
decltype(IsSizeOfKnown(std::declval<T*>()))::value;
};
template <typename T, typename U>
constexpr bool IsDecayedSameV =
std::is_same_v<std::decay_t<T>, std::decay_t<U>>;
template <typename B, typename D>
constexpr bool IsStrictlyBaseOfV =
std::is_base_of_v<std::decay_t<B>, std::decay_t<D>> &&
!IsDecayedSameV<B, D>;
} // namespace internal
/**
* Value is true for types that inherit from `GarbageCollectedMixin` but not
* `GarbageCollected<T>` (i.e., they are free mixins), and false otherwise.
*/
template <typename T>
constexpr bool IsGarbageCollectedMixinTypeV =
internal::IsGarbageCollectedMixinType<T>::value;
/**
* Value is true for types that inherit from `GarbageCollected<T>`, and false
* otherwise.
*/
template <typename T>
constexpr bool IsGarbageCollectedTypeV =
internal::IsGarbageCollectedType<T>::value;
/**
* Value is true for types that inherit from either `GarbageCollected<T>` or
* `GarbageCollectedMixin`, and false otherwise.
*/
template <typename T>
constexpr bool IsGarbageCollectedOrMixinTypeV =
internal::IsGarbageCollectedOrMixinType<T>::value;
/**
* Value is true for types that inherit from `GarbageCollected<T>` and
* `GarbageCollectedMixin`, and false otherwise.
*/
template <typename T>
constexpr bool IsGarbageCollectedWithMixinTypeV =
internal::IsGarbageCollectedWithMixinType<T>::value;
/**
* Value is true for types of type `Member<T>`, and false otherwise.
*/
template <typename T>
constexpr bool IsMemberTypeV = internal::IsMemberType<T>::value;
/**
* Value is true for types of type `UntracedMember<T>`, and false otherwise.
*/
template <typename T>
constexpr bool IsUntracedMemberTypeV = internal::IsUntracedMemberType<T>::value;
/**
* Value is true for types of type `WeakMember<T>`, and false otherwise.
*/
template <typename T>
constexpr bool IsWeakMemberTypeV = internal::IsWeakMemberType<T>::value;
/**
* Value is true for types that are considered weak references, and false
* otherwise.
*/
template <typename T>
constexpr bool IsWeakV = internal::IsWeak<T>::value;
/**
* Value is true for types that are complete, and false otherwise.
*/
template <typename T>
constexpr bool IsCompleteV = internal::IsComplete<T>::value;
} // namespace cppgc
#endif // INCLUDE_CPPGC_TYPE_TRAITS_H_

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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_VISITOR_H_
#define INCLUDE_CPPGC_VISITOR_H_
#include "cppgc/custom-space.h"
#include "cppgc/ephemeron-pair.h"
#include "cppgc/garbage-collected.h"
#include "cppgc/internal/logging.h"
#include "cppgc/internal/pointer-policies.h"
#include "cppgc/liveness-broker.h"
#include "cppgc/member.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/source-location.h"
#include "cppgc/trace-trait.h"
#include "cppgc/type-traits.h"
namespace cppgc {
namespace internal {
template <typename T, typename WeaknessPolicy, typename LocationPolicy,
typename CheckingPolicy>
class BasicCrossThreadPersistent;
template <typename T, typename WeaknessPolicy, typename LocationPolicy,
typename CheckingPolicy>
class BasicPersistent;
class ConservativeTracingVisitor;
class VisitorBase;
class VisitorFactory;
} // namespace internal
using WeakCallback = void (*)(const LivenessBroker&, const void*);
/**
* Visitor passed to trace methods. All managed pointers must have called the
* Visitor's trace method on them.
*
* \code
* class Foo final : public GarbageCollected<Foo> {
* public:
* void Trace(Visitor* visitor) const {
* visitor->Trace(foo_);
* visitor->Trace(weak_foo_);
* }
* private:
* Member<Foo> foo_;
* WeakMember<Foo> weak_foo_;
* };
* \endcode
*/
class V8_EXPORT Visitor {
public:
class Key {
private:
Key() = default;
friend class internal::VisitorFactory;
};
explicit Visitor(Key) {}
virtual ~Visitor() = default;
/**
* Trace method for Member.
*
* \param member Member reference retaining an object.
*/
template <typename T>
void Trace(const Member<T>& member) {
const T* value = member.GetRawAtomic();
CPPGC_DCHECK(value != kSentinelPointer);
TraceImpl(value);
}
/**
* Trace method for WeakMember.
*
* \param weak_member WeakMember reference weakly retaining an object.
*/
template <typename T>
void Trace(const WeakMember<T>& weak_member) {
static_assert(sizeof(T), "Pointee type must be fully defined.");
static_assert(internal::IsGarbageCollectedOrMixinType<T>::value,
"T must be GarbageCollected or GarbageCollectedMixin type");
static_assert(!internal::IsAllocatedOnCompactableSpace<T>::value,
"Weak references to compactable objects are not allowed");
const T* value = weak_member.GetRawAtomic();
// Bailout assumes that WeakMember emits write barrier.
if (!value) {
return;
}
CPPGC_DCHECK(value != kSentinelPointer);
VisitWeak(value, TraceTrait<T>::GetTraceDescriptor(value),
&HandleWeak<WeakMember<T>>, &weak_member);
}
#if defined(CPPGC_POINTER_COMPRESSION)
/**
* Trace method for UncompressedMember.
*
* \param member UncompressedMember reference retaining an object.
*/
template <typename T>
void Trace(const subtle::UncompressedMember<T>& member) {
const T* value = member.GetRawAtomic();
CPPGC_DCHECK(value != kSentinelPointer);
TraceImpl(value);
}
#endif // defined(CPPGC_POINTER_COMPRESSION)
/**
* Trace method for inlined objects that are not allocated themselves but
* otherwise follow managed heap layout and have a Trace() method.
*
* \param object reference of the inlined object.
*/
template <typename T>
void Trace(const T& object) {
#if V8_ENABLE_CHECKS
// This object is embedded in potentially multiple nested objects. The
// outermost object must not be in construction as such objects are (a) not
// processed immediately, and (b) only processed conservatively if not
// otherwise possible.
CheckObjectNotInConstruction(&object);
#endif // V8_ENABLE_CHECKS
TraceTrait<T>::Trace(this, &object);
}
/**
* Registers a weak callback method on the object of type T. See
* LivenessBroker for an usage example.
*
* \param object of type T specifying a weak callback method.
*/
template <typename T, void (T::*method)(const LivenessBroker&)>
void RegisterWeakCallbackMethod(const T* object) {
RegisterWeakCallback(&WeakCallbackMethodDelegate<T, method>, object);
}
/**
* Trace method for EphemeronPair.
*
* \param ephemeron_pair EphemeronPair reference weakly retaining a key object
* and strongly retaining a value object in case the key object is alive.
*/
template <typename K, typename V>
void Trace(const EphemeronPair<K, V>& ephemeron_pair) {
TraceEphemeron(ephemeron_pair.key, &ephemeron_pair.value);
RegisterWeakCallbackMethod<EphemeronPair<K, V>,
&EphemeronPair<K, V>::ClearValueIfKeyIsDead>(
&ephemeron_pair);
}
/**
* Trace method for a single ephemeron. Used for tracing a raw ephemeron in
* which the `key` and `value` are kept separately.
*
* \param weak_member_key WeakMember reference weakly retaining a key object.
* \param member_value Member reference with ephemeron semantics.
*/
template <typename KeyType, typename ValueType>
void TraceEphemeron(const WeakMember<KeyType>& weak_member_key,
const Member<ValueType>* member_value) {
const KeyType* key = weak_member_key.GetRawAtomic();
if (!key) return;
// `value` must always be non-null.
CPPGC_DCHECK(member_value);
const ValueType* value = member_value->GetRawAtomic();
if (!value) return;
// KeyType and ValueType may refer to GarbageCollectedMixin.
TraceDescriptor value_desc =
TraceTrait<ValueType>::GetTraceDescriptor(value);
CPPGC_DCHECK(value_desc.base_object_payload);
const void* key_base_object_payload =
TraceTrait<KeyType>::GetTraceDescriptor(key).base_object_payload;
CPPGC_DCHECK(key_base_object_payload);
VisitEphemeron(key_base_object_payload, value, value_desc);
}
/**
* Trace method for a single ephemeron. Used for tracing a raw ephemeron in
* which the `key` and `value` are kept separately. Note that this overload
* is for non-GarbageCollected `value`s that can be traced though.
*
* \param key `WeakMember` reference weakly retaining a key object.
* \param value Reference weakly retaining a value object. Note that
* `ValueType` here should not be `Member`. It is expected that
* `TraceTrait<ValueType>::GetTraceDescriptor(value)` returns a
* `TraceDescriptor` with a null base pointer but a valid trace method.
*/
template <typename KeyType, typename ValueType>
void TraceEphemeron(const WeakMember<KeyType>& weak_member_key,
const ValueType* value) {
static_assert(!IsGarbageCollectedOrMixinTypeV<ValueType>,
"garbage-collected types must use WeakMember and Member");
const KeyType* key = weak_member_key.GetRawAtomic();
if (!key) return;
// `value` must always be non-null.
CPPGC_DCHECK(value);
TraceDescriptor value_desc =
TraceTrait<ValueType>::GetTraceDescriptor(value);
// `value_desc.base_object_payload` must be null as this override is only
// taken for non-garbage-collected values.
CPPGC_DCHECK(!value_desc.base_object_payload);
// KeyType might be a GarbageCollectedMixin.
const void* key_base_object_payload =
TraceTrait<KeyType>::GetTraceDescriptor(key).base_object_payload;
CPPGC_DCHECK(key_base_object_payload);
VisitEphemeron(key_base_object_payload, value, value_desc);
}
/**
* Trace method that strongifies a WeakMember.
*
* \param weak_member WeakMember reference retaining an object.
*/
template <typename T>
void TraceStrongly(const WeakMember<T>& weak_member) {
const T* value = weak_member.GetRawAtomic();
CPPGC_DCHECK(value != kSentinelPointer);
TraceImpl(value);
}
/**
* Trace method for retaining containers strongly.
*
* \param object reference to the container.
*/
template <typename T>
void TraceStrongContainer(const T* object) {
TraceImpl(object);
}
/**
* Trace method for retaining containers weakly. Note that weak containers
* should emit write barriers.
*
* \param object reference to the container.
* \param callback to be invoked.
* \param callback_data custom data that is passed to the callback.
*/
template <typename T>
void TraceWeakContainer(const T* object, WeakCallback callback,
const void* callback_data) {
if (!object) return;
VisitWeakContainer(object, TraceTrait<T>::GetTraceDescriptor(object),
TraceTrait<T>::GetWeakTraceDescriptor(object), callback,
callback_data);
}
/**
* Registers a slot containing a reference to an object allocated on a
* compactable space. Such references maybe be arbitrarily moved by the GC.
*
* \param slot location of reference to object that might be moved by the GC.
* The slot must contain an uncompressed pointer.
*/
template <typename T>
void RegisterMovableReference(const T** slot) {
static_assert(internal::IsAllocatedOnCompactableSpace<T>::value,
"Only references to objects allocated on compactable spaces "
"should be registered as movable slots.");
static_assert(!IsGarbageCollectedMixinTypeV<T>,
"Mixin types do not support compaction.");
HandleMovableReference(reinterpret_cast<const void**>(slot));
}
/**
* Registers a weak callback that is invoked during garbage collection.
*
* \param callback to be invoked.
* \param data custom data that is passed to the callback.
*/
virtual void RegisterWeakCallback(WeakCallback callback, const void* data) {}
/**
* Defers tracing an object from a concurrent thread to the mutator thread.
* Should be called by Trace methods of types that are not safe to trace
* concurrently.
*
* \param parameter tells the trace callback which object was deferred.
* \param callback to be invoked for tracing on the mutator thread.
* \param deferred_size size of deferred object.
*
* \returns false if the object does not need to be deferred (i.e. currently
* traced on the mutator thread) and true otherwise (i.e. currently traced on
* a concurrent thread).
*/
virtual V8_WARN_UNUSED_RESULT bool DeferTraceToMutatorThreadIfConcurrent(
const void* parameter, TraceCallback callback, size_t deferred_size) {
// By default tracing is not deferred.
return false;
}
protected:
virtual void Visit(const void* self, TraceDescriptor) {}
virtual void VisitWeak(const void* self, TraceDescriptor, WeakCallback,
const void* weak_member) {}
virtual void VisitEphemeron(const void* key, const void* value,
TraceDescriptor value_desc) {}
virtual void VisitWeakContainer(const void* self, TraceDescriptor strong_desc,
TraceDescriptor weak_desc,
WeakCallback callback, const void* data) {}
virtual void HandleMovableReference(const void**) {}
private:
template <typename T, void (T::*method)(const LivenessBroker&)>
static void WeakCallbackMethodDelegate(const LivenessBroker& info,
const void* self) {
// Callback is registered through a potential const Trace method but needs
// to be able to modify fields. See HandleWeak.
(const_cast<T*>(static_cast<const T*>(self))->*method)(info);
}
template <typename PointerType>
static void HandleWeak(const LivenessBroker& info, const void* object) {
const PointerType* weak = static_cast<const PointerType*>(object);
auto* raw_ptr = weak->GetFromGC();
if (!info.IsHeapObjectAlive(raw_ptr)) {
weak->ClearFromGC();
}
}
template <typename T>
void TraceImpl(const T* t) {
static_assert(sizeof(T), "Pointee type must be fully defined.");
static_assert(internal::IsGarbageCollectedOrMixinType<T>::value,
"T must be GarbageCollected or GarbageCollectedMixin type");
if (!t) {
return;
}
Visit(t, TraceTrait<T>::GetTraceDescriptor(t));
}
#if V8_ENABLE_CHECKS
void CheckObjectNotInConstruction(const void* address);
#endif // V8_ENABLE_CHECKS
template <typename T, typename WeaknessPolicy, typename LocationPolicy,
typename CheckingPolicy>
friend class internal::BasicCrossThreadPersistent;
template <typename T, typename WeaknessPolicy, typename LocationPolicy,
typename CheckingPolicy>
friend class internal::BasicPersistent;
friend class internal::ConservativeTracingVisitor;
friend class internal::VisitorBase;
};
namespace internal {
class V8_EXPORT RootVisitor {
public:
explicit RootVisitor(Visitor::Key) {}
virtual ~RootVisitor() = default;
template <typename AnyStrongPersistentType,
std::enable_if_t<
AnyStrongPersistentType::IsStrongPersistent::value>* = nullptr>
void Trace(const AnyStrongPersistentType& p) {
using PointeeType = typename AnyStrongPersistentType::PointeeType;
const void* object = Extract(p);
if (!object) {
return;
}
VisitRoot(object, TraceTrait<PointeeType>::GetTraceDescriptor(object),
p.Location());
}
template <typename AnyWeakPersistentType,
std::enable_if_t<
!AnyWeakPersistentType::IsStrongPersistent::value>* = nullptr>
void Trace(const AnyWeakPersistentType& p) {
using PointeeType = typename AnyWeakPersistentType::PointeeType;
static_assert(!internal::IsAllocatedOnCompactableSpace<PointeeType>::value,
"Weak references to compactable objects are not allowed");
const void* object = Extract(p);
if (!object) {
return;
}
VisitWeakRoot(object, TraceTrait<PointeeType>::GetTraceDescriptor(object),
&HandleWeak<AnyWeakPersistentType>, &p, p.Location());
}
protected:
virtual void VisitRoot(const void*, TraceDescriptor, const SourceLocation&) {}
virtual void VisitWeakRoot(const void* self, TraceDescriptor, WeakCallback,
const void* weak_root, const SourceLocation&) {}
private:
template <typename AnyPersistentType>
static const void* Extract(AnyPersistentType& p) {
using PointeeType = typename AnyPersistentType::PointeeType;
static_assert(sizeof(PointeeType),
"Persistent's pointee type must be fully defined");
static_assert(internal::IsGarbageCollectedOrMixinType<PointeeType>::value,
"Persistent's pointee type must be GarbageCollected or "
"GarbageCollectedMixin");
return p.GetFromGC();
}
template <typename PointerType>
static void HandleWeak(const LivenessBroker& info, const void* object) {
const PointerType* weak = static_cast<const PointerType*>(object);
auto* raw_ptr = weak->GetFromGC();
if (!info.IsHeapObjectAlive(raw_ptr)) {
weak->ClearFromGC();
}
}
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_VISITOR_H_