NPFVAR_PROTO
const opt_proto_t *op = npfvar_get_data(vars, NPFVAR_PROTO, 0);
const opt_proto_t *op = npfvar_get_data(vars, NPFVAR_PROTO, i);
const opt_proto_t *op = npfvar_get_data(vars, NPFVAR_PROTO, i);
NPFVAR_PROTO, &$3, sizeof($3));
$$ = npfvar_create_element(NPFVAR_PROTO, &$1, sizeof($1));
$$ = npfvar_create_element(NPFVAR_PROTO, &$2, sizeof($2));
[NPFVAR_PROTO] = "proto",