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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 "base/base_export.h"
      9 #include "base/callback.h"
     10 #include "base/containers/stack.h"
     11 #include "base/macros.h"
     12 #include "base/synchronization/lock.h"
     13 
     14 namespace base {
     15 
     16 // This class provides a facility similar to the CRT atexit(), except that
     17 // we control when the callbacks are executed. Under Windows for a DLL they
     18 // happen at a really bad time and under the loader lock. This facility is
     19 // mostly used by base::Singleton.
     20 //
     21 // The usage is simple. Early in the main() or WinMain() scope create an
     22 // AtExitManager object on the stack:
     23 // int main(...) {
     24 //    base::AtExitManager exit_manager;
     25 //
     26 // }
     27 // When the exit_manager object goes out of scope, all the registered
     28 // callbacks and singleton destructors will be called.
     29 
     30 class BASE_EXPORT AtExitManager {
     31  public:
     32   typedef void (*AtExitCallbackType)(void*);
     33 
     34   AtExitManager();
     35 
     36   // The dtor calls all the registered callbacks. Do not try to register more
     37   // callbacks after this point.
     38   ~AtExitManager();
     39 
     40   // Registers the specified function to be called at exit. The prototype of
     41   // the callback function is void func(void*).
     42   static void RegisterCallback(AtExitCallbackType func, void* param);
     43 
     44   // Registers the specified task to be called at exit.
     45   static void RegisterTask(base::Closure task);
     46 
     47   // Calls the functions registered with RegisterCallback in LIFO order. It
     48   // is possible to register new callbacks after calling this function.
     49   static void ProcessCallbacksNow();
     50 
     51   // Disable all registered at-exit callbacks. This is used only in a single-
     52   // process mode.
     53   static void DisableAllAtExitManagers();
     54 
     55  protected:
     56   // This constructor will allow this instance of AtExitManager to be created
     57   // even if one already exists.  This should only be used for testing!
     58   // AtExitManagers are kept on a global stack, and it will be removed during
     59   // destruction.  This allows you to shadow another AtExitManager.
     60   explicit AtExitManager(bool shadow);
     61 
     62  private:
     63   base::Lock lock_;
     64   base::stack<base::Closure> stack_;
     65   bool processing_callbacks_;
     66   AtExitManager* next_manager_;  // Stack of managers to allow shadowing.
     67 
     68   DISALLOW_COPY_AND_ASSIGN(AtExitManager);
     69 };
     70 
     71 #if defined(UNIT_TEST)
     72 class ShadowingAtExitManager : public AtExitManager {
     73  public:
     74   ShadowingAtExitManager() : AtExitManager(true) {}
     75 };
     76 #endif  // defined(UNIT_TEST)
     77 
     78 }  // namespace base
     79 
     80 #endif  // BASE_AT_EXIT_H_
     81