-class Task;
-using TaskPtr = boost::intrusive_ptr<Task>;
-XBT_PUBLIC void intrusive_ptr_release(Task* o);
-XBT_PUBLIC void intrusive_ptr_add_ref(Task* o);
-class ExecTask;
-using ExecTaskPtr = boost::intrusive_ptr<ExecTask>;
-class CommTask;
-using CommTaskPtr = boost::intrusive_ptr<CommTask>;
-class IoTask;
-using IoTaskPtr = boost::intrusive_ptr<IoTask>;
-