DFN_NAN
cyclenlp->toporder = DFN_NAN; /* graph call chain */
parentp->toporder = DFN_NAN;
if (parentp->toporder == DFN_NAN) {
return (childp->toporder != DFN_NAN && childp->toporder != DFN_BUSY);
if (childp->toporder == DFN_NAN)
int dfn_counter = DFN_NAN;