Bug#20432: mysql client interprets commands in comments

do not look for client-specific commands while inside a multi-line comment.
we will allow multi-comments pretty much anywhere within SQL-statements,
but client-specific commands (help, use, print, ...) must be the first token
in the input.

client/mysql.cc

@@ -1052,7 +1052,7 @@ static int read_lines(bool execute_commands)
       (We want to allow help, print and clear anywhere at line start
     */
     if (execute_commands && (named_cmds || glob_buffer.is_empty()) 
-	&& !in_string && (com=find_command(line,0)))
+	&& !ml_comment && !in_string && (com=find_command(line,0)))
     {
       if ((*com->func)(&glob_buffer,line) > 0)
 	break;

mysql-test/r/mysql_client.result

+1
+1
+ERROR 1064 (42000) at line 3: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
+ERROR at line 1: USE must be followed by a database name

mysql-test/t/mysql_client.test

+# This test should work in embedded server after we fix mysqltest
+-- source include/not_embedded.inc
+
+#
+# Bug #20432: mysql client interprets commands in comments
+#
+
+# if the client sees the 'use' within the comment, we haven't fixed
+--exec echo "/*"          >  $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec echo "use"         >> $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec echo "*/"          >> $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec $MYSQL              < $MYSQLTEST_VARDIR/tmp/bug20432.sql 2>&1
+
+# SQL can have embedded comments => workie
+--exec echo "select /*"   >  $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec echo "use"         >> $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec echo "*/ 1"        >> $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec $MYSQL              < $MYSQLTEST_VARDIR/tmp/bug20432.sql 2>&1
+
+# client commands on the other hand must be at BOL => error
+--exec echo "/*"          >  $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec echo "xxx"         >> $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec echo "*/ use"      >> $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--error 1
+--exec $MYSQL              < $MYSQLTEST_VARDIR/tmp/bug20432.sql 2>&1
+
+# client comment recognized, but parameter missing => error
+--exec echo "use"         >  $MYSQLTEST_VARDIR/tmp/bug20432.sql
+--exec $MYSQL              < $MYSQLTEST_VARDIR/tmp/bug20432.sql 2>&1