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99 lines
3.2 KiB
C++
99 lines
3.2 KiB
C++
//===- llvm/ADT/EpochTracker.h - ADT epoch tracking --------------*- C++ -*-==//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the DebugEpochBase and DebugEpochBase::HandleBase classes.
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// These can be used to write iterators that are fail-fast when LLVM is built
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// with asserts enabled.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_EPOCHTRACKER_H
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#define LLVM_ADT_EPOCHTRACKER_H
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#include "llvm/Config/abi-breaking.h"
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#include <cstdint>
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namespace llvm {
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#if LLVM_ENABLE_ABI_BREAKING_CHECKS
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/// A base class for data structure classes wishing to make iterators
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/// ("handles") pointing into themselves fail-fast. When building without
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/// asserts, this class is empty and does nothing.
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///
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/// DebugEpochBase does not by itself track handles pointing into itself. The
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/// expectation is that routines touching the handles will poll on
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/// isHandleInSync at appropriate points to assert that the handle they're using
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/// is still valid.
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///
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class DebugEpochBase {
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uint64_t Epoch;
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public:
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DebugEpochBase() : Epoch(0) {}
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/// Calling incrementEpoch invalidates all handles pointing into the
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/// calling instance.
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void incrementEpoch() { ++Epoch; }
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/// The destructor calls incrementEpoch to make use-after-free bugs
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/// more likely to crash deterministically.
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~DebugEpochBase() { incrementEpoch(); }
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/// A base class for iterator classes ("handles") that wish to poll for
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/// iterator invalidating modifications in the underlying data structure.
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/// When LLVM is built without asserts, this class is empty and does nothing.
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///
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/// HandleBase does not track the parent data structure by itself. It expects
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/// the routines modifying the data structure to call incrementEpoch when they
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/// make an iterator-invalidating modification.
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///
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class HandleBase {
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const uint64_t *EpochAddress;
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uint64_t EpochAtCreation;
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public:
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HandleBase() : EpochAddress(nullptr), EpochAtCreation(UINT64_MAX) {}
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explicit HandleBase(const DebugEpochBase *Parent)
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: EpochAddress(&Parent->Epoch), EpochAtCreation(Parent->Epoch) {}
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/// Returns true if the DebugEpochBase this Handle is linked to has
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/// not called incrementEpoch on itself since the creation of this
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/// HandleBase instance.
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bool isHandleInSync() const { return *EpochAddress == EpochAtCreation; }
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/// Returns a pointer to the epoch word stored in the data structure
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/// this handle points into. Can be used to check if two iterators point
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/// into the same data structure.
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const void *getEpochAddress() const { return EpochAddress; }
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};
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};
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#else
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class DebugEpochBase {
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public:
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void incrementEpoch() {}
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class HandleBase {
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public:
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HandleBase() = default;
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explicit HandleBase(const DebugEpochBase *) {}
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bool isHandleInSync() const { return true; }
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const void *getEpochAddress() const { return nullptr; }
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};
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};
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#endif // LLVM_ENABLE_ABI_BREAKING_CHECKS
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} // namespace llvm
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#endif
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