semantic check for RRSIG: improve info string construction

refs #4

src/knot/zone/semantic-check.c

@@ -293,8 +293,13 @@ static int check_rrsig_rdata(err_handler_t *handler,
                              const knot_rrset_t *dnskey_rrset)
 {
 	/* Prepare additional info string. */
-	char info_str[50] = "Record type: ";
-	knot_rrtype_to_string(knot_rrset_type(rrset), info_str + 13, 47);
+	char info_str[50] = { '\0' };
+	char type_str[10] = { '\0' };
+	knot_rrtype_to_string(knot_rrset_type(rrset), type_str, sizeof(type_str));
+	int ret = snprintf(info_str, sizeof(info_str), "Record type: %s", type_str);
+	if (ret < 0 || ret >= sizeof(info_str)) {
+		return KNOT_ENOMEM;
+	}
 
 	if (knot_rrset_rdata_rr_count(rrsig) == 0) {
 		err_handler_handle_error(handler, node, ZC_ERR_RRSIG_NO_RRSIG,