friend s4u::Mailbox;
friend s4u::MailboxPtr s4u::Mailbox::by_name(const std::string& name);
friend mc::CommunicationDeterminismChecker;
friend s4u::Mailbox;
friend s4u::MailboxPtr s4u::Mailbox::by_name(const std::string& name);
friend mc::CommunicationDeterminismChecker;