aopen_entry
union aopen_entry *p = t->afree;
union aopen_entry *p = &t->atid_tab[atid - t->atid_base];
t->atid_tab = (union aopen_entry *)&t->tid_tab[t->ntids];
union aopen_entry *atid_tab;
union aopen_entry *afree;
union aopen_entry *next;