MDEV-7130: MASTER_POS_WAIT(log_name,log_pos,timeout,"connection_name") hangs, does not respect the timeout

Changed also arg_count check for connection_name to prevent same bug
if fifth argument is introduced in future

Author: f4rnham

mysql-test/suite/rpl/r/rpl_master_pos_wait.result

@@ -18,4 +18,26 @@ show slave status;
 select master_pos_wait('foo', 98);
 master_pos_wait('foo', 98)
 NULL
+*** MDEV-7130: MASTER_POS_WAIT(log_name,log_pos,timeout,"connection_name") hangs, does not respect the timeout ***
+include/stop_slave.inc
+reset slave all;
+change master 'my_slave' to master_port=MASTER_MYPORT, master_host='127.0.0.1', master_user='root';
+set default_master_connection = 'my_slave';
+include/start_slave.inc
+# Call without connection name -- works (expected -1)
+select master_pos_wait('master-bin.000001',1000000,1);
+master_pos_wait('master-bin.000001',1000000,1)
+-1
+set default_master_connection = '';
+# Call for non-existing anonymous connection -- works (expected NULL)
+select master_pos_wait('master-bin.000001',1000000,1);
+master_pos_wait('master-bin.000001',1000000,1)
+NULL
+# Call with a valid connection name -- hangs before MDEV-7130 fix (expected -1)
+select master_pos_wait('master-bin.000001',1000000,1,"my_slave");
+master_pos_wait('master-bin.000001',1000000,1,"my_slave")
+-1
+STOP SLAVE 'my_slave';
+RESET SLAVE 'my_slave' ALL;
+change master to master_port=MASTER_MYPORT, master_host='127.0.0.1', master_user='root';
 include/rpl_end.inc

mysql-test/suite/rpl/t/rpl_master_pos_wait.test

@@ -25,5 +25,36 @@ echo "*** must be NULL ***";
 select master_pos_wait('foo', 98);
 
 # End of 4.1 tests
+
+
+--echo *** MDEV-7130: MASTER_POS_WAIT(log_name,log_pos,timeout,"connection_name") hangs, does not respect the timeout ***
+
+--connection slave
+--source include/stop_slave.inc
+reset slave all;
+--replace_result $MASTER_MYPORT MASTER_MYPORT
+eval change master 'my_slave' to master_port=$MASTER_MYPORT, master_host='127.0.0.1', master_user='root';
+set default_master_connection = 'my_slave';
+--source include/start_slave.inc
+
+--echo # Call without connection name -- works (expected -1)
+select master_pos_wait('master-bin.000001',1000000,1);
+
+set default_master_connection = '';
+
+--echo # Call for non-existing anonymous connection -- works (expected NULL)
+select master_pos_wait('master-bin.000001',1000000,1);
+
+--echo # Call with a valid connection name -- hangs before MDEV-7130 fix (expected -1)
+select master_pos_wait('master-bin.000001',1000000,1,"my_slave");
+
+STOP SLAVE 'my_slave';
+RESET SLAVE 'my_slave' ALL;
+
+--replace_result $MASTER_MYPORT MASTER_MYPORT
+eval change master to master_port=$MASTER_MYPORT, master_host='127.0.0.1', master_user='root';
+
+# End of 10.0 tests
+
 --let $rpl_only_running_threads= 1
 --source include/rpl_end.inc

sql/item_func.cc

@@ -3943,11 +3943,11 @@ longlong Item_master_pos_wait::val_int()
   }
 #ifdef HAVE_REPLICATION
   longlong pos = (ulong)args[1]->val_int();
-  longlong timeout = (arg_count==3) ? args[2]->val_int() : 0 ;
+  longlong timeout = (arg_count>=3) ? args[2]->val_int() : 0 ;
   String connection_name_buff;
   LEX_STRING connection_name;
   Master_info *mi;
-  if (arg_count == 4)
+  if (arg_count >= 4)
   {
     String *con;
     if (!(con= args[3]->val_str(&connection_name_buff)))