-surf_callback(void, simgrid::surf::Storage*) storageCreatedCallbacks;
-surf_callback(void, simgrid::surf::Storage*) storageDestructedCallbacks;
-surf_callback(void, simgrid::surf::Storage*, e_surf_resource_state_t, e_surf_resource_state_t) storageStateChangedCallbacks;
-surf_callback(void, simgrid::surf::StorageAction*, e_surf_action_state_t, e_surf_action_state_t) storageActionStateChangedCallbacks;
+simgrid::xbt::signal<void(simgrid::surf::Storage*)> storageCreatedCallbacks;
+simgrid::xbt::signal<void(simgrid::surf::Storage*)> storageDestructedCallbacks;
+simgrid::xbt::signal<void(simgrid::surf::Storage*, int, int)> storageStateChangedCallbacks; // signature: wasOn, isOn
+simgrid::xbt::signal<void(simgrid::surf::StorageAction*, e_surf_action_state_t, e_surf_action_state_t)> storageActionStateChangedCallbacks;