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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   AtExitManager* next_manager_;  // Stack of managers to allow shadowing.
     63 
     64   DISALLOW_COPY_AND_ASSIGN(AtExitManager);
     65 };
     66 
     67 #if defined(UNIT_TEST)
     68 class ShadowingAtExitManager : public AtExitManager {
     69  public:
     70   ShadowingAtExitManager() : AtExitManager(true) {}
     71 };
     72 #endif  // defined(UNIT_TEST)
     73 
     74 }  // namespace base
     75 
     76 #endif  // BASE_AT_EXIT_H_
     77