base/at_exit.h

   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/basictypes.h"
  12 #include "base/callback.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_