+ smx_mailbox_t getImpl() { return pimpl_; } // FIXME: make me protected
+
+ // We don't have to manage the lifetime of mailboxes:
+ friend void intrusive_ptr_add_ref(Mailbox*) {}
+ friend void intrusive_ptr_release(Mailbox*) {}
+ using Ptr = boost::intrusive_ptr<Mailbox>;
+