Message Box With Gtk

I want a simple function showing Message box in gtk like Windows'API.
Therefore I make next code.

/**
 * This method's work is like Windows' MessageBox
 * @date 2009-1-10
 * @version 1.0
 */
bool ShowMessageBox(std::string title, std::string message)
{
  GlobalParameter* gp = GlobalParameter::getInstance();
  GtkDialogFlags flag=(GtkDialogFlags(GTK_DIALOG_MODAL|GTK_DIALOG_DESTROY_WITH_PARENT);
  GtkWidget* dialog = gtk_dialog_new_with_buttons(title.c_str(),GTK_WINDOW(gp->getM_main_window()),flag,NULL);
  GtkWidget* label = gtk_label_new(message.c_str());
  gtk_container_add(GTK_CONTAINER(GTK_DIALOG(dialog)->vbox),label);
  gtk_widget_show_all(dialog);
  gint response = gtk_dialog_run(GTK_DIALOG(dialog));
  return true;
}