3eefe03c51
A few notes: 1) Oilpan is a generic library, meaning that it can work with arbitrary user types. The library is split in type-aware (include/) and type-erased (src/) parts. The former comprises a lot of code that still needs to be defended with dchecks; 2) Macros are prefixed with CPPGC_, so that they don't clash in the user code with similar macros from other libraries; 3) The macros simply forward requests to V8 so that dcheck handlers can be configured uniformly; 4) The CL doesn't contain CHECK_EQ and friends, but they can be added later if needed. Bug: chromium:1056170 Change-Id: I68e6f663247705233eaf030384164d81e53071e1 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2148774 Commit-Queue: Anton Bikineev <bikineev@chromium.org> Reviewed-by: Omer Katz <omerkatz@chromium.org> Reviewed-by: Michael Lippautz <mlippautz@chromium.org> Reviewed-by: Ulan Degenbaev <ulan@chromium.org> Cr-Commit-Position: refs/heads/master@{#67129}
93 lines
2.7 KiB
C++
93 lines
2.7 KiB
C++
// Copyright 2020 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef INCLUDE_CPPGC_VISITOR_H_
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#define INCLUDE_CPPGC_VISITOR_H_
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#include "include/cppgc/garbage-collected.h"
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#include "include/cppgc/internal/logging.h"
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#include "include/cppgc/internal/pointer-policies.h"
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#include "include/cppgc/liveness-broker.h"
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#include "include/cppgc/member.h"
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#include "include/cppgc/trace-trait.h"
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namespace cppgc {
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namespace internal {
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class VisitorBase;
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} // namespace internal
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class Visitor;
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using WeakCallback = void (*)(const LivenessBroker&, const void*);
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/**
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* Visitor passed to trace methods. All managed pointers must have called the
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* visitor's trace method on them.
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*/
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class Visitor {
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public:
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template <typename T>
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void Trace(const Member<T>& member) {
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const T* value = member.GetRawAtomic();
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CPPGC_DCHECK(value != kSentinelPointer);
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Trace(value);
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}
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template <typename T>
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void Trace(const WeakMember<T>& weak_member) {
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static_assert(sizeof(T), "T must be fully defined");
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static_assert(internal::IsGarbageCollectedType<T>::value,
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"T must be GarabgeCollected or GarbageCollectedMixin type");
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const T* value = weak_member.GetRawAtomic();
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// Bailout assumes that WeakMember emits write barrier.
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if (!value) {
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return;
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}
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// TODO(chromium:1056170): DCHECK (or similar) for deleted values as they
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// should come in at a different path.
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VisitWeak(value, TraceTrait<T>::GetTraceDescriptor(value),
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&HandleWeakMember<T>, &weak_member);
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}
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protected:
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virtual void Visit(const void* self, TraceDescriptor) {}
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virtual void VisitWeak(const void* self, TraceDescriptor, WeakCallback,
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const void* weak_member) {}
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private:
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template <typename T>
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static void HandleWeakMember(const LivenessBroker& info, const void* object) {
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const WeakMember<T>* weak_member =
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reinterpret_cast<const WeakMember<T>*>(object);
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if (!info.IsHeapObjectAlive(*weak_member)) {
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// Object is passed down through the marker as const. Alternatives are
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// - non-const Trace method;
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// - mutable pointer in MemberBase;
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const_cast<WeakMember<T>*>(weak_member)->Clear();
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}
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}
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Visitor() = default;
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template <typename T>
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void Trace(const T* t) {
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static_assert(sizeof(T), "T must be fully defined");
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static_assert(internal::IsGarbageCollectedType<T>::value,
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"T must be GarabgeCollected or GarbageCollectedMixin type");
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if (!t) {
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return;
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}
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Visit(t, TraceTrait<T>::GetTraceDescriptor(t));
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}
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friend class internal::VisitorBase;
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};
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} // namespace cppgc
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#endif // INCLUDE_CPPGC_VISITOR_H_
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