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1 // Copyright (c) 2011 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/base_export.h"
11 #include "base/callback.h"
12 #include "base/macros.h"
13 #include "base/synchronization/lock.h"
14 
15 namespace base {
16 
17 // This class provides a facility similar to the CRT atexit(), except that
18 // we control when the callbacks are executed. Under Windows for a DLL they
19 // happen at a really bad time and under the loader lock. This facility is
20 // mostly used by base::Singleton.
21 //
22 // The usage is simple. Early in the main() or WinMain() scope create an
23 // AtExitManager object on the stack:
24 // int main(...) {
25 //    base::AtExitManager exit_manager;
26 //
27 // }
28 // When the exit_manager object goes out of scope, all the registered
29 // callbacks and singleton destructors will be called.
30 
31 class BASE_EXPORT AtExitManager {
32  public:
33   typedef void (*AtExitCallbackType)(void*);
34 
35   AtExitManager();
36 
37   // The dtor calls all the registered callbacks. Do not try to register more
38   // callbacks after this point.
39   ~AtExitManager();
40 
41   // Registers the specified function to be called at exit. The prototype of
42   // the callback function is void func(void*).
43   static void RegisterCallback(AtExitCallbackType func, void* param);
44 
45   // Registers the specified task to be called at exit.
46   static void RegisterTask(base::Closure task);
47 
48   // Calls the functions registered with RegisterCallback in LIFO order. It
49   // is possible to register new callbacks after calling this function.
50   static void ProcessCallbacksNow();
51 
52  protected:
53   // This constructor will allow this instance of AtExitManager to be created
54   // even if one already exists.  This should only be used for testing!
55   // AtExitManagers are kept on a global stack, and it will be removed during
56   // destruction.  This allows you to shadow another AtExitManager.
57   explicit AtExitManager(bool shadow);
58 
59  private:
60   base::Lock lock_;
61   std::stack<base::Closure> stack_;
62   bool processing_callbacks_;
63   AtExitManager* next_manager_;  // Stack of managers to allow shadowing.
64 
65   DISALLOW_COPY_AND_ASSIGN(AtExitManager);
66 };
67 
68 #if defined(UNIT_TEST)
69 class ShadowingAtExitManager : public AtExitManager {
70  public:
ShadowingAtExitManager()71   ShadowingAtExitManager() : AtExitManager(true) {}
72 };
73 #endif  // defined(UNIT_TEST)
74 
75 }  // namespace base
76 
77 #endif  // BASE_AT_EXIT_H_
78