Tor should exit if it fails to write its PidFile, under principle of least confusion. Also, maybe Tor should create the directory that the PidFile points to
Running with the option: --PidFile /var/run/tor/tor.pid Directory /var/run/tor is missing. Tor starts without any warnings. It has to either create the directory, or complain that it can't create the pid file.
FreeBSD 10.3