at_exit.h revision c7f5f8508d98d5952d42ed7648c2a8f30a4da156 
1// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef BASE_AT_EXIT_H_
6#define BASE_AT_EXIT_H_
7
8#include <stack>
9
10#include "base/basictypes.h"
11#include "base/lock.h"
12
13namespace base {
14
15// This class provides a facility similar to the CRT atexit(), except that
16// we control when the callbacks are executed. Under Windows for a DLL they
17// happen at a really bad time and under the loader lock. This facility is
18// mostly used by base::Singleton.
19//
20// The usage is simple. Early in the main() or WinMain() scope create an
21// AtExitManager object on the stack:
22// int main(...) {
23//    base::AtExitManager exit_manager;
24//
25// }
26// When the exit_manager object goes out of scope, all the registered
27// callbacks and singleton destructors will be called.
28
29class AtExitManager {
30 protected:
31  // This constructor will allow this instance of AtExitManager to be created
32  // even if one already exists.  This should only be used for testing!
33  // AtExitManagers are kept on a global stack, and it will be removed during
34  // destruction.  This allows you to shadow another AtExitManager.
35  explicit AtExitManager(bool shadow);
36
37 public:
38  typedef void (*AtExitCallbackType)(void*);
39
40  AtExitManager();
41
42  // The dtor calls all the registered callbacks. Do not try to register more
43  // callbacks after this point.
44  ~AtExitManager();
45
46  // Registers the specified function to be called at exit. The prototype of
47  // the callback function is void func().
48  static void RegisterCallback(AtExitCallbackType func, void* param);
49
50  // Calls the functions registered with RegisterCallback in LIFO order. It
51  // is possible to register new callbacks after calling this function.
52  static void ProcessCallbacksNow();
53
54 private:
55  struct CallbackAndParam {
56    CallbackAndParam(AtExitCallbackType func, void* param)
57        : func_(func), param_(param) { }
58    AtExitCallbackType func_;
59    void* param_;
60  };
61
62  Lock lock_;
63  std::stack<CallbackAndParam> stack_;
64  AtExitManager* next_manager_;  // Stack of managers to allow shadowing.
65
66  DISALLOW_COPY_AND_ASSIGN(AtExitManager);
67};
68
69#if defined(UNIT_TEST)
70class ShadowingAtExitManager : public AtExitManager {
71 public:
72  ShadowingAtExitManager() : AtExitManager(true) {}
73};
74#endif  // defined(UNIT_TEST)
75
76}  // namespace base
77
78#endif  // BASE_AT_EXIT_H_
79