Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/ADT/EpochTracker.h
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//===- 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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5.30G
  void incrementEpoch() {}
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  class HandleBase {
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  public:
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    HandleBase() = default;
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25.4G
    explicit HandleBase(const DebugEpochBase *) {}
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0
    bool isHandleInSync() const { return true; }
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0
    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