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| Rev | Author | Line No. | Line |
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| 14 | pmbaty | 1 | //===- llvm/ADT/EpochTracker.h - ADT epoch tracking --------------*- C++ -*-==// |
| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | /// |
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| 9 | /// \file |
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| 10 | /// This file defines the DebugEpochBase and DebugEpochBase::HandleBase classes. |
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| 11 | /// These can be used to write iterators that are fail-fast when LLVM is built |
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| 12 | /// with asserts enabled. |
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| 13 | /// |
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| 14 | //===----------------------------------------------------------------------===// |
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| 15 | |||
| 16 | #ifndef LLVM_ADT_EPOCHTRACKER_H |
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| 17 | #define LLVM_ADT_EPOCHTRACKER_H |
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| 18 | |||
| 19 | #include "llvm/Config/abi-breaking.h" |
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| 20 | |||
| 21 | #include <cstdint> |
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| 22 | |||
| 23 | namespace llvm { |
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| 24 | |||
| 25 | #if LLVM_ENABLE_ABI_BREAKING_CHECKS |
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| 26 | |||
| 27 | /// A base class for data structure classes wishing to make iterators |
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| 28 | /// ("handles") pointing into themselves fail-fast. When building without |
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| 29 | /// asserts, this class is empty and does nothing. |
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| 30 | /// |
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| 31 | /// DebugEpochBase does not by itself track handles pointing into itself. The |
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| 32 | /// expectation is that routines touching the handles will poll on |
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| 33 | /// isHandleInSync at appropriate points to assert that the handle they're using |
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| 34 | /// is still valid. |
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| 35 | /// |
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| 36 | class DebugEpochBase { |
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| 37 | uint64_t Epoch = 0; |
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| 38 | |||
| 39 | public: |
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| 40 | DebugEpochBase() = default; |
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| 41 | |||
| 42 | /// Calling incrementEpoch invalidates all handles pointing into the |
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| 43 | /// calling instance. |
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| 44 | void incrementEpoch() { ++Epoch; } |
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| 45 | |||
| 46 | /// The destructor calls incrementEpoch to make use-after-free bugs |
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| 47 | /// more likely to crash deterministically. |
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| 48 | ~DebugEpochBase() { incrementEpoch(); } |
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| 49 | |||
| 50 | /// A base class for iterator classes ("handles") that wish to poll for |
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| 51 | /// iterator invalidating modifications in the underlying data structure. |
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| 52 | /// When LLVM is built without asserts, this class is empty and does nothing. |
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| 53 | /// |
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| 54 | /// HandleBase does not track the parent data structure by itself. It expects |
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| 55 | /// the routines modifying the data structure to call incrementEpoch when they |
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| 56 | /// make an iterator-invalidating modification. |
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| 57 | /// |
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| 58 | class HandleBase { |
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| 59 | const uint64_t *EpochAddress = nullptr; |
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| 60 | uint64_t EpochAtCreation = UINT64_MAX; |
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| 61 | |||
| 62 | public: |
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| 63 | HandleBase() = default; |
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| 64 | |||
| 65 | explicit HandleBase(const DebugEpochBase *Parent) |
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| 66 | : EpochAddress(&Parent->Epoch), EpochAtCreation(Parent->Epoch) {} |
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| 67 | |||
| 68 | /// Returns true if the DebugEpochBase this Handle is linked to has |
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| 69 | /// not called incrementEpoch on itself since the creation of this |
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| 70 | /// HandleBase instance. |
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| 71 | bool isHandleInSync() const { return *EpochAddress == EpochAtCreation; } |
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| 72 | |||
| 73 | /// Returns a pointer to the epoch word stored in the data structure |
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| 74 | /// this handle points into. Can be used to check if two iterators point |
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| 75 | /// into the same data structure. |
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| 76 | const void *getEpochAddress() const { return EpochAddress; } |
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| 77 | }; |
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| 78 | }; |
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| 79 | |||
| 80 | #else |
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| 81 | |||
| 82 | class DebugEpochBase { |
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| 83 | public: |
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| 84 | void incrementEpoch() {} |
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| 85 | |||
| 86 | class HandleBase { |
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| 87 | public: |
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| 88 | HandleBase() = default; |
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| 89 | explicit HandleBase(const DebugEpochBase *) {} |
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| 90 | bool isHandleInSync() const { return true; } |
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| 91 | const void *getEpochAddress() const { return nullptr; } |
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| 92 | }; |
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| 93 | }; |
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| 94 | |||
| 95 | #endif // LLVM_ENABLE_ABI_BREAKING_CHECKS |
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| 96 | |||
| 97 | } // namespace llvm |
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| 98 | |||
| 99 | #endif |