LLVM  6.0.0svn
EpochTracker.h
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1 //===- llvm/ADT/EpochTracker.h - ADT epoch tracking --------------*- C++ -*-==//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines the DebugEpochBase and DebugEpochBase::HandleBase classes.
11 // These can be used to write iterators that are fail-fast when LLVM is built
12 // with asserts enabled.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_ADT_EPOCH_TRACKER_H
17 #define LLVM_ADT_EPOCH_TRACKER_H
18 
19 #include "llvm/Config/abi-breaking.h"
20 #include "llvm/Config/llvm-config.h"
21 
22 #include <cstdint>
23 
24 namespace llvm {
25 
26 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
27 
28 /// \brief A base class for data structure classes wishing to make iterators
29 /// ("handles") pointing into themselves fail-fast. When building without
30 /// asserts, this class is empty and does nothing.
31 ///
32 /// DebugEpochBase does not by itself track handles pointing into itself. The
33 /// expectation is that routines touching the handles will poll on
34 /// isHandleInSync at appropriate points to assert that the handle they're using
35 /// is still valid.
36 ///
38  uint64_t Epoch;
39 
40 public:
41  DebugEpochBase() : Epoch(0) {}
42 
43  /// \brief Calling incrementEpoch invalidates all handles pointing into the
44  /// calling instance.
45  void incrementEpoch() { ++Epoch; }
46 
47  /// \brief The destructor calls incrementEpoch to make use-after-free bugs
48  /// more likely to crash deterministically.
50 
51  /// \brief A base class for iterator classes ("handles") that wish to poll for
52  /// iterator invalidating modifications in the underlying data structure.
53  /// When LLVM is built without asserts, this class is empty and does nothing.
54  ///
55  /// HandleBase does not track the parent data structure by itself. It expects
56  /// the routines modifying the data structure to call incrementEpoch when they
57  /// make an iterator-invalidating modification.
58  ///
59  class HandleBase {
60  const uint64_t *EpochAddress;
61  uint64_t EpochAtCreation;
62 
63  public:
64  HandleBase() : EpochAddress(nullptr), EpochAtCreation(UINT64_MAX) {}
65 
66  explicit HandleBase(const DebugEpochBase *Parent)
67  : EpochAddress(&Parent->Epoch), EpochAtCreation(Parent->Epoch) {}
68 
69  /// \brief Returns true if the DebugEpochBase this Handle is linked to has
70  /// not called incrementEpoch on itself since the creation of this
71  /// HandleBase instance.
72  bool isHandleInSync() const { return *EpochAddress == EpochAtCreation; }
73 
74  /// \brief Returns a pointer to the epoch word stored in the data structure
75  /// this handle points into. Can be used to check if two iterators point
76  /// into the same data structure.
77  const void *getEpochAddress() const { return EpochAddress; }
78  };
79 };
80 
81 #else
82 
83 class DebugEpochBase {
84 public:
85  void incrementEpoch() {}
86 
87  class HandleBase {
88  public:
89  HandleBase() = default;
90  explicit HandleBase(const DebugEpochBase *) {}
91  bool isHandleInSync() const { return true; }
92  const void *getEpochAddress() const { return nullptr; }
93  };
94 };
95 
96 #endif // LLVM_ENABLE_ABI_BREAKING_CHECKS
97 
98 } // namespace llvm
99 
100 #endif
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
A base class for data structure classes wishing to make iterators ("handles") pointing into themselve...
Definition: EpochTracker.h:37
~DebugEpochBase()
The destructor calls incrementEpoch to make use-after-free bugs more likely to crash deterministicall...
Definition: EpochTracker.h:49
void incrementEpoch()
Calling incrementEpoch invalidates all handles pointing into the calling instance.
Definition: EpochTracker.h:45
A base class for iterator classes ("handles") that wish to poll for iterator invalidating modificatio...
Definition: EpochTracker.h:59
HandleBase(const DebugEpochBase *Parent)
Definition: EpochTracker.h:66
const void * getEpochAddress() const
Returns a pointer to the epoch word stored in the data structure this handle points into...
Definition: EpochTracker.h:77
bool isHandleInSync() const
Returns true if the DebugEpochBase this Handle is linked to has not called incrementEpoch on itself s...
Definition: EpochTracker.h:72