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 {
101protected:
102  CrashRecoveryContext *context;
103  CrashRecoveryContextCleanup(CrashRecoveryContext *context)
104    : context(context), cleanupFired(false) {}
105public:
106  bool cleanupFired;
107
108  virtual ~CrashRecoveryContextCleanup();
109  virtual void recoverResources() = 0;
110
111  CrashRecoveryContext *getContext() const {
112    return context;
113  }
114
115private:
116  friend class CrashRecoveryContext;
117  CrashRecoveryContextCleanup *prev, *next;
118};
119
120template<typename DERIVED, typename T>
121class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
122protected:
123  T *resource;
124  CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T* resource)
125    : CrashRecoveryContextCleanup(context), resource(resource) {}
126public:
127  static DERIVED *create(T *x) {
128    if (x) {
129      if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
130        return new DERIVED(context, x);
131    }
132    return 0;
133  }
134};
135
136template <typename T>
137class CrashRecoveryContextDestructorCleanup : public
138  CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
139public:
140  CrashRecoveryContextDestructorCleanup(CrashRecoveryContext *context,
141                                        T *resource)
142    : CrashRecoveryContextCleanupBase<
143        CrashRecoveryContextDestructorCleanup<T>, T>(context, resource) {}
144
145  virtual void recoverResources() {
146    this->resource->~T();
147  }
148};
149
150template <typename T>
151class CrashRecoveryContextDeleteCleanup : public
152  CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
153public:
154  CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
155    : CrashRecoveryContextCleanupBase<
156        CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
157
158  virtual void recoverResources() {
159    delete this->resource;
160  }
161};
162
163template <typename T>
164class CrashRecoveryContextReleaseRefCleanup : public
165  CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T>
166{
167public:
168  CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
169                                        T *resource)
170    : CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>,
171          T>(context, resource) {}
172
173  virtual void recoverResources() {
174    this->resource->Release();
175  }
176};
177
178template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
179class CrashRecoveryContextCleanupRegistrar {
180  CrashRecoveryContextCleanup *cleanup;
181public:
182  CrashRecoveryContextCleanupRegistrar(T *x)
183    : cleanup(Cleanup::create(x)) {
184    if (cleanup)
185      cleanup->getContext()->registerCleanup(cleanup);
186  }
187
188  ~CrashRecoveryContextCleanupRegistrar() {
189    unregister();
190  }
191
192  void unregister() {
193    if (cleanup && !cleanup->cleanupFired)
194      cleanup->getContext()->unregisterCleanup(cleanup);
195    cleanup = 0;
196  }
197};
198}
199
200#endif
201