-Application *Application::app_ = 0;
-Application::Starter *Application::starter_ = 0;
-const char *Application::argv0_ = 0;
-string Application::name_;
-void *Application::data_ = 0;
+Application *Application::_app = nullptr;
+Application::Starter *Application::_starter = nullptr;
+const char *Application::_argv0 = nullptr;
+string Application::_name;
+void *Application::_data = nullptr;