1 //===- llvm/ADT/EpochTracker.h - ADT epoch tracking --------------*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_ADT_EPOCH_TRACKER_H
17 #define LLVM_ADT_EPOCH_TRACKER_H
19 #include "llvm/Config/abi-breaking.h"
20 #include "llvm/Config/llvm-config.h"
26 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
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.
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
37 class DebugEpochBase {
41 DebugEpochBase() : Epoch(0) {}
43 /// \brief Calling incrementEpoch invalidates all handles pointing into the
45 void incrementEpoch() { ++Epoch; }
47 /// \brief The destructor calls incrementEpoch to make use-after-free bugs
48 /// more likely to crash deterministically.
49 ~DebugEpochBase() { incrementEpoch(); }
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.
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.
60 const uint64_t *EpochAddress;
61 uint64_t EpochAtCreation;
64 HandleBase() : EpochAddress(nullptr), EpochAtCreation(UINT64_MAX) {}
66 explicit HandleBase(const DebugEpochBase *Parent)
67 : EpochAddress(&Parent->Epoch), EpochAtCreation(Parent->Epoch) {}
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; }
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; }
83 class DebugEpochBase {
85 void incrementEpoch() {}
89 HandleBase() = default;
90 explicit HandleBase(const DebugEpochBase *) {}
91 bool isHandleInSync() const { return true; }
92 const void *getEpochAddress() const { return nullptr; }
96 #endif // LLVM_ENABLE_ABI_BREAKING_CHECKS