Fix for bug #11896 "Partial locking in case of recursive trigger definitions".

If we are in stored function or trigger we should ensure that we won't change
table that is already used by calling statement (this can damage table or
easily cause infinite loops). Particularly this means that recursive triggers
should be disallowed.

mysql-test/t/sp-error.test

@@ -409,6 +409,35 @@ lock tables mysql.proc write|
 unlock tables|
 
 
+#
+# Check that in functions we don't allow to update tables which
+# are used by statements which invoke these functions.
+#
+--disable_warnings
+drop function if exists f1|
+--enable_warnings
+create function f1(i int) returns int
+begin
+  insert into t1 (val) values (i);
+  return 0;
+end|
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+select val, f1(val) from t1|
+# Table alias should not matter
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+select val, f1(val) from t1 as tab|
+select * from t1|
+--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
+update t1 set val= f1(val)|
+select * from t1|
+# But this should be OK
+select f1(17)|
+select * from t1|
+# Cleanup
+delete from t1 where val= 17|
+drop function f1|
+
+
 #
 # BUG#1965
 #