- * Log a message to syslog if multi-threaded HTTP_DAEMON, else to bio_err
- * prog: the name of the current app
+ * Output a message using the trace API with the given category
+ * if the category is >= 0 and tracing is enabled.
+ * Log the message to syslog if multi-threaded HTTP_DAEMON, else to bio_err
+ * if the verbosity is sufficient for the given level of severity.
+ * category: trace category as defined in trace.h, or -1
+ * prog: the name of the current app, or NULL