+ "-v", Arg.Set(verbose), " verbose mode"; ] @
+IFNDEF NTRACE
+THEN [
+ "-trace-file", Arg.Set_string(trace_file),
+ "<trace_file> save the full trace in dot format in <trace_file>";
+ "-trace", Arg.String (set_tracer),
+ "<tracer1:l1,...,tracern:ln> enable tracing with the specified level. Valid tracers are: "
+ ^ (pretty_tracers ())
+ ]
+ELSE []
+END
+