base/at_exit.h

   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
  13 namespace 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
  29 class 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   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 }  // namespace base
  70
  71 #endif  // BASE_AT_EXIT_H_