Log torrc option can't handle tab after severity
Set your torrc file to be
log debug file /tmp/debug.log
where that long space is a tab.
tor -f /path/to/torrc
and you'll get
Aug 23 15:23:49.300 [warn] Couldn't parse log levels in Log option 'Log debug file /tmp/debug.log' Aug 23 15:23:49.300 [warn] Failed to parse/validate config: Failed to validate Log options. See logs for details. Aug 23 15:23:49.300 [err] Reading config failed--see warnings above.
It looks like the issue is in parse_log_severity_config() where we do stuff like
space = strchr(cfg, ' ');
Reported by toralf.