error safe for casting bytea 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 ='bytea'::regtype
order by castsource::regtype;

 castsource | casttarget | castfunc | castcontext | castmethod |   prosrc   | proname
------------+------------+----------+-------------+------------+------------+---------
 bytea      | smallint   |     6370 | e           | f          | bytea_int2 | int2
 bytea      | integer    |     6371 | e           | f          | bytea_int4 | int4
 bytea      | bigint     |     6372 | e           | f          | bytea_int8 | int8
(3 rows)

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

Author: jianhe-fun

src/backend/utils/adt/bytea.c

@@ -1027,10 +1027,14 @@ bytea_int2(PG_FUNCTION_ARGS)
 
 	/* Check that the byte array is not too long */
 	if (len > sizeof(result))
-		ereport(ERROR,
+	{
+		errsave(fcinfo->context,
 				errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 				errmsg("smallint out of range"));
 
+		PG_RETURN_NULL();
+	}
+
 	/* Convert it to an integer; most significant bytes come first */
 	result = 0;
 	for (int i = 0; i < len; i++)
@@ -1052,10 +1056,14 @@ bytea_int4(PG_FUNCTION_ARGS)
 
 	/* Check that the byte array is not too long */
 	if (len > sizeof(result))
-		ereport(ERROR,
+	{
+		errsave(fcinfo->context,
 				errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 				errmsg("integer out of range"));
 
+		PG_RETURN_NULL();
+	}
+
 	/* Convert it to an integer; most significant bytes come first */
 	result = 0;
 	for (int i = 0; i < len; i++)
@@ -1077,10 +1085,14 @@ bytea_int8(PG_FUNCTION_ARGS)
 
 	/* Check that the byte array is not too long */
 	if (len > sizeof(result))
-		ereport(ERROR,
+	{
+		errsave(fcinfo->context,
 				errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 				errmsg("bigint out of range"));
 
+		PG_RETURN_NULL();
+	}
+
 	/* Convert it to an integer; most significant bytes come first */
 	result = 0;
 	for (int i = 0; i < len; i++)