let get_marked_out_zone call_marks =
let add (out0, out_zone) (out_key, m_out) =
if MarkPair.is_bottom m_out then (out0, out_zone)
else match out_key with
| PdgIndex.Signature.OutRet -> true, out_zone
| PdgIndex.Signature.OutLoc z ->
out0, Locations.Zone.join out_zone z
in Signature.fold_all_outputs add (false, Locations.Zone.bottom) call_marks