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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
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_EPOCH_TRACKER_H
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#define LLVM_ADT_EPOCH_TRACKER_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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