CrashRecoveryContext.h revision b52fde4185cd724f51aae4018b0f8278732379c7 
1//===--- CrashRecoveryContext.h - Crash Recovery ----------------*- 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#ifndef LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
11#define LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
12
13#include <string>
14
15namespace llvm {
16class StringRef;
17
18class CrashRecoveryContextCleanup;
19
20/// \brief Crash recovery helper object.
21///
22/// This class implements support for running operations in a safe context so
23/// that crashes (memory errors, stack overflow, assertion violations) can be
24/// detected and control restored to the crashing thread. Crash detection is
25/// purely "best effort", the exact set of failures which can be recovered from
26/// is platform dependent.
27///
28/// Clients make use of this code by first calling
29/// CrashRecoveryContext::Enable(), and then executing unsafe operations via a
30/// CrashRecoveryContext object. For example:
31///
32///    void actual_work(void *);
33///
34///    void foo() {
35///      CrashRecoveryContext CRC;
36///
37///      if (!CRC.RunSafely(actual_work, 0)) {
38///         ... a crash was detected, report error to user ...
39///      }
40///
41///      ... no crash was detected ...
42///    }
43///
44/// Crash recovery contexts may not be nested.
45class CrashRecoveryContext {
46  void *Impl;
47  CrashRecoveryContextCleanup *head;
48
49public:
50  CrashRecoveryContext() : Impl(0), head(0) {}
51  ~CrashRecoveryContext();
52
53  void registerCleanup(CrashRecoveryContextCleanup *cleanup);
54  void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
55
56  /// \brief Enable crash recovery.
57  static void Enable();
58
59  /// \brief Disable crash recovery.
60  static void Disable();
61
62  /// \brief Return the active context, if the code is currently executing in a
63  /// thread which is in a protected context.
64  static CrashRecoveryContext *GetCurrent();
65
66  /// \brief Return true if the current thread is recovering from a
67  /// crash.
68  static bool isRecoveringFromCrash();
69
70  /// \brief Execute the provide callback function (with the given arguments) in
71  /// a protected context.
72  ///
73  /// \return True if the function completed successfully, and false if the
74  /// function crashed (or HandleCrash was called explicitly). Clients should
75  /// make as little assumptions as possible about the program state when
76  /// RunSafely has returned false. Clients can use getBacktrace() to retrieve
77  /// the backtrace of the crash on failures.
78  bool RunSafely(void (*Fn)(void*), void *UserData);
79
80  /// \brief Execute the provide callback function (with the given arguments) in
81  /// a protected context which is run in another thread (optionally with a
82  /// requested stack size).
83  ///
84  /// See RunSafely() and llvm_execute_on_thread().
85  bool RunSafelyOnThread(void (*Fn)(void*), void *UserData,
86                         unsigned RequestedStackSize = 0);
87
88  /// \brief Explicitly trigger a crash recovery in the current process, and
89  /// return failure from RunSafely(). This function does not return.
90  void HandleCrash();
91
92  /// \brief Return a string containing the backtrace where the crash was
93  /// detected; or empty if the backtrace wasn't recovered.
94  ///
95  /// This function is only valid when a crash has been detected (i.e.,
96  /// RunSafely() has returned false.
97  const std::string &getBacktrace() const;
98};
99
100class CrashRecoveryContextCleanup {
101public:
102  bool cleanupFired;
103  enum ProvidedCleanups { DeleteCleanup, DestructorCleanup };
104
105  CrashRecoveryContextCleanup() : cleanupFired(false) {}
106  virtual ~CrashRecoveryContextCleanup();
107  virtual void recoverResources() = 0;
108
109  template <typename T> static CrashRecoveryContextCleanup *create(T *,
110                          ProvidedCleanups cleanupKind =
111                            CrashRecoveryContextCleanup::DeleteCleanup);
112
113private:
114  friend class CrashRecoveryContext;
115  CrashRecoveryContextCleanup *prev, *next;
116};
117
118template <typename T>
119class CrashRecoveryContextDestructorCleanup
120  : public CrashRecoveryContextCleanup
121{
122  T *resource;
123public:
124  CrashRecoveryContextDestructorCleanup(T *resource) : resource(resource) {}
125  virtual void recoverResources() {
126    resource->~T();
127  }
128};
129
130template <typename T>
131class CrashRecoveryContextDeleteCleanup
132  : public CrashRecoveryContextCleanup
133{
134  T *resource;
135public:
136  CrashRecoveryContextDeleteCleanup(T *resource) : resource(resource) {}
137  virtual void recoverResources() {
138    delete resource;
139  }
140};
141
142template <typename T>
143struct CrashRecoveryContextTrait {
144  static inline CrashRecoveryContextCleanup *
145  createCleanup(T *resource,
146                CrashRecoveryContextCleanup::ProvidedCleanups cleanup) {
147    switch (cleanup) {
148      case CrashRecoveryContextCleanup::DeleteCleanup:
149        return new CrashRecoveryContextDeleteCleanup<T>(resource);
150      case CrashRecoveryContextCleanup::DestructorCleanup:
151        return new CrashRecoveryContextDestructorCleanup<T>(resource);
152    }
153    return 0;
154  }
155};
156
157template<typename T>
158inline CrashRecoveryContextCleanup*
159CrashRecoveryContextCleanup::create(T *x,
160          CrashRecoveryContextCleanup::ProvidedCleanups cleanupKind) {
161  return CrashRecoveryContext::GetCurrent() ?
162          CrashRecoveryContextTrait<T>::createCleanup(x, cleanupKind) :
163          0;
164}
165
166class CrashRecoveryContextCleanupRegistrar {
167  CrashRecoveryContext *context;
168  CrashRecoveryContextCleanup *cleanup;
169public:
170  CrashRecoveryContextCleanupRegistrar(CrashRecoveryContextCleanup *cleanup)
171    : context(CrashRecoveryContext::GetCurrent()),
172      cleanup(cleanup)
173  {
174    if (context && cleanup)
175      context->registerCleanup(cleanup);
176  }
177  ~CrashRecoveryContextCleanupRegistrar() {
178    if (cleanup && !cleanup->cleanupFired) {
179      if (context)
180        context->unregisterCleanup(cleanup);
181      else
182        delete cleanup;
183    }
184  }
185};
186}
187
188#endif
189