Creating Dynamic Singletons & the Loki Library

Listing 8

  template <class T>
  class DeletableSingleton {
  public:
    static void ScheduleDestruction(T*, void (*pFun)()) {
      static bool firstPass = true;
      isDead = false;
      deleter = pFun;
      if (firstPass || needCallback) {
        std::atexit(atexitCallback);
        firstPass = false;
        needCallback = false;
      }
    }
    static void OnDeadReference() { }
    static void GracefulDelete();
  protected:
    static void (*deleter) ();
    static bool isDead;
    static bool needCallback;
    static void atexitCallback();
  };

  template <class T> void (*DeletableSingleton<T>::deleter) ();
  template <class T> bool DeletableSingleton<T>::isDead = true;
  template <class T> bool DeletableSingleton<T>::needCallback = true;

  template< class T >
  void DeletableSingleton<T>::GracefulDelete() {
    if (isDead) return;
    isDead = true;
    deleter();
  }

  template< class T >
  void DeletableSingleton<T>::atexitCallback() {
    needCallback =
#ifdef ATEXIT_FIXED
     true;
#else
     false;
#endif
     GracefulDelete();
  }