Bug#12611: ESCAPE + LIKE do not work when the escape char is a multibyte one

item_cmpfunc.cc:
  Pass unicode value as "escape" argument to my_wildcmp
  if a multibyte character set is used.
  For single byte character set nothing has changed:
  native (non-unicode) character code is still passed.

ctype_utf8.result, ctype_utf8.test:
  adding test case

mysql-test/r/ctype_utf8.result

@@ -955,6 +955,10 @@ char_length(a)	length(a)	a
 2	4	ан
 drop table t1;
 set names utf8;
+select 'andre%' like 'andreñ%' escape 'ñ';
+'andre%' like 'andreñ%' escape 'ñ'
+1
+set names utf8;
 select 'a\\' like 'a\\';
 'a\\' like 'a\\'
 1

mysql-test/t/ctype_utf8.test

@@ -810,6 +810,12 @@ alter table t1 modify a char(2) character set utf8;
 select char_length(a), length(a), a from t1 order by a;
 drop table t1;
 
+#
+# Bugs#12611
+# ESCAPE + LIKE do not work when the escape char is a multibyte one
+#
+set names utf8;
+select 'andre%' like 'andreñ%' escape 'ñ';
 
 #
 # Bugs#11754: SET NAMES utf8 followed by SELECT "A\\" LIKE "A\\" returns 0

sql/item_cmpfunc.cc

@@ -2293,7 +2293,25 @@ bool Item_func_like::fix_fields(THD *thd, TABLE_LIST *tlist, Item ** ref)
   {
     /* If we are on execution stage */
     String *escape_str= escape_item->val_str(&tmp_value1);
-    escape= escape_str ? *(escape_str->ptr()) : '\\';
+    if (escape_str)
+    {
+      CHARSET_INFO *cs= cmp.cmp_collation.collation;
+      if (use_mb(cs))
+      {
+        my_wc_t wc;
+        int rc= cs->cset->mb_wc(cs, &wc,
+                                (const uchar*) escape_str->ptr(),
+                                (const uchar*) escape_str->ptr() +
+                                               escape_str->length());
+        escape= (int) (rc > 0 ? wc : '\\');
+      }
+      else
+      {
+        escape= *(escape_str->ptr());
+      }
+    }
+    else
+      escape= '\\';
  
     /*
       We could also do boyer-more for non-const items, but as we would have to