namespace s4u {
xbt::signal<void(Activity&)> Activity::on_veto;
-xbt::signal<void(Activity&)> Activity::on_completion;
+xbt::signal<void(Activity const&)> Activity::on_completion;
+xbt::signal<void(Activity const&)> Activity::on_suspended;
+xbt::signal<void(Activity const&)> Activity::on_resumed;
std::set<Activity*>* Activity::vetoed_activities_ = nullptr;