Function span_log 

pub unsafe extern "C" fn span_log(
    s: *mut logging_state_t,
    level: c_int,
    format: *const c_char,
    ...
) -> c_int

Generate a log entry. \brief Generate a log entry. \param s The logging context. \param level The severity level of the entry. \param format ??? \return 0 if no output generated, else 1.