MDEV-9346 - The federatedx and spider engine make mysqld crash when they are

            configured withtout username

Federated/spider/connect engines or replication threads connecting to other host
with empty user name may crash mysqld.

This is addition to original patch, which adds a test case and amends a macro.

mysql-test/suite/federated/federatedx.result

@@ -2157,6 +2157,12 @@ DROP TABLE federated.t1;
 End of 5.1 tests
 SET @@GLOBAL.CONCURRENT_INSERT= @OLD_MASTER_CONCURRENT_INSERT;
 SET @@GLOBAL.CONCURRENT_INSERT= @OLD_SLAVE_CONCURRENT_INSERT;
+#
+# MDEV-9346 - The federatedx and spider engine make mysqld crash when
+#             they are configured withtout username
+#
+CREATE TABLE t1 (a INT) ENGINE=FEDERATED CONNECTION='mysql://@127.0.0.1:SLAVE_PORT/federated/t1';
+ERROR HY000: Can't create federated table. Foreign data src error:  database: 'federated'  username: ''  hostname: '127.0.0.1'
 DROP TABLE IF EXISTS federated.t1;
 DROP DATABASE IF EXISTS federated;
 DROP TABLE IF EXISTS federated.t1;

mysql-test/suite/federated/federatedx.test

@@ -2000,4 +2000,13 @@ SET @@GLOBAL.CONCURRENT_INSERT= @OLD_SLAVE_CONCURRENT_INSERT;
 
 connection default;
 
+--echo #
+--echo # MDEV-9346 - The federatedx and spider engine make mysqld crash when
+--echo #             they are configured withtout username
+--echo #
+connection master;
+--replace_result $SLAVE_MYPORT SLAVE_PORT
+--error ER_CANT_CREATE_FEDERATED_TABLE
+eval CREATE TABLE t1 (a INT) ENGINE=FEDERATED CONNECTION='mysql://@127.0.0.1:$SLAVE_MYPORT/federated/t1';
+
 source include/federated_cleanup.inc;

sql/client_settings.h

@@ -37,7 +37,7 @@
                              CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA | \
                              CLIENT_CONNECT_ATTRS)
 
-#define read_user_name(A) {strmov(A,"");}
+#define read_user_name(A) A[0]= 0
 #undef _CUSTOMCONFIG_
 
 #define mysql_server_init(a,b,c) mysql_client_plugin_init()