error safe for casting macaddr8 to other types per pg_cast

select castsource::regtype, casttarget::regtype, castfunc, castcontext,castmethod, pp.prosrc, pp.proname
from pg_cast pc join pg_proc pp on pp.oid = pc.castfunc
and pc.castfunc > 0 and castsource::regtype ='macaddr8'::regtype
order by castsource::regtype;

 castsource | casttarget | castfunc | castcontext | castmethod |      prosrc       | proname
------------+------------+----------+-------------+------------+-------------------+---------
 macaddr8   | macaddr    |     4124 | i           | f          | macaddr8tomacaddr | macaddr
(1 row)

discussion: https://postgr.es/m/CADkLM=fv1JfY4Ufa-jcwwNbjQixNViskQ8jZu3Tz_p656i_4hQ@mail.gmail.com

Author: jianhe-fun

src/backend/utils/adt/mac8.c

@@ -550,7 +550,7 @@ macaddr8tomacaddr(PG_FUNCTION_ARGS)
 	result = (macaddr *) palloc0(sizeof(macaddr));
 
 	if ((addr->d != 0xFF) || (addr->e != 0xFE))
-		ereport(ERROR,
+		ereturn(fcinfo->context, (Datum) 0,
 				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 				 errmsg("macaddr8 data out of range to convert to macaddr"),
 				 errhint("Only addresses that have FF and FE as values in the "