MDEV-6609 SQL inside an anonymous block is executed with wrong SQL_MODE

MDEV-6606 Server crashes in String::append on selecting sql_mode inside anonymous block

mysql-test/r/compound.result

@@ -155,11 +155,20 @@ execute stmt using @a, @b, @c|
 include/show_binlog_events.inc
 Log_name	Pos	Event_type	Server_id	End_log_pos	Info
 master-bin.000001	#	Gtid	#	#	GTID #-#-#
-master-bin.000001	#	Query	#	#	use `test`; SELECT "test"."fn"(9)
+master-bin.000001	#	Query	#	#	use `test`; SELECT `test`.`fn`(9)
 master-bin.000001	#	Gtid	#	#	GTID #-#-#
-master-bin.000001	#	Query	#	#	use `test`; SELECT "test"."fn"(1)
+master-bin.000001	#	Query	#	#	use `test`; SELECT `test`.`fn`(1)
 master-bin.000001	#	Gtid	#	#	BEGIN GTID #-#-#
 master-bin.000001	#	Query	#	#	use `test`; insert t1 values( NAME_CONST('a',4)+3)
 master-bin.000001	#	Query	#	#	COMMIT
 drop function fn|
 drop table t1|
+begin not atomic select @@sql_mode; end|
+@@sql_mode
+
+create table t1 (a int)|
+select a from t1 having a > 1|
+a
+begin not atomic select a from t1 having a > 1; end|
+a
+drop table t1|

mysql-test/t/compound.test

@@ -148,3 +148,13 @@ delimiter |;
 drop function fn|
 drop table t1|
 
+#
+# MDEV-6606 Server crashes in String::append on selecting sql_mode inside anonymous block
+# MDEV-6609 SQL inside an anonymous block is executed with wrong SQL_MODE
+#
+begin not atomic select @@sql_mode; end|
+create table t1 (a int)|
+select a from t1 having a > 1|
+begin not atomic select a from t1 having a > 1; end|
+drop table t1|
+

sql/sql_yacc.yy

@@ -254,6 +254,7 @@ static bool maybe_start_compound_statement(THD *thd)
 
     Lex->sp_chistics.suid= SP_IS_NOT_SUID;
     Lex->sphead->set_body_start(thd, YYLIP->get_cpp_ptr());
+    Lex->sphead->m_sql_mode= thd->variables.sql_mode;
   }
   return 0;
 }