ctype_utf8.result, ctype_utf8.test, item_strfunc.cc:

  LEFT() didn't work well in some cases.

mysql-test/r/ctype_utf8.result

@@ -93,6 +93,9 @@ this	is a	test
 select insert("aa",100,1,"b"),insert("aa",1,3,"b");
 insert("aa",100,1,"b")	insert("aa",1,3,"b")
 aa	b
+select char_length(left(@a:='тест',5)), length(@a), @a;
+char_length(left(@a:='тест',5))	length(@a)	@a
+4	8	тест
 create table t1 select date_format("2004-01-19 10:10:10", "%Y-%m-%d");
 show create table t1;
 Table	Create Table

mysql-test/t/ctype_utf8.test

@@ -62,6 +62,12 @@ DROP TABLE t1;
 select insert('txs',2,1,'hi'),insert('is ',4,0,'a'),insert('txxxxt',2,4,'es');
 select insert("aa",100,1,"b"),insert("aa",1,3,"b");
 
+#
+# LELF() didn't work well with utf8 in some cases too.
+#
+select char_length(left(@a:='тест',5)), length(@a), @a;
+
+
 #
 # CREATE ... SELECT
 #

sql/item_strfunc.cc

@@ -977,17 +977,19 @@ String *Item_func_left::val_str(String *str)
   DBUG_ASSERT(fixed == 1);
   String *res  =args[0]->val_str(str);
   long length  =(long) args[1]->val_int();
+  uint char_pos;
 
   if ((null_value=args[0]->null_value))
     return 0;
   if (length <= 0)
     return &my_empty_string;
-  if (res->length() <= (uint) length)
+  if (res->length() <= (uint) length ||
+      res->length() <= (char_pos= res->charpos(length)))
     return res;
   if (&str_value == res)
-    str_value.length(res->charpos(length));
+    str_value.length(char_pos);
   else
-    str_value.set(*res, 0, res->charpos(length));
+    str_value.set(*res, 0, char_pos);
   return &str_value;
 }