Bug #4555 ALTER TABLE crashes mysqld with enum column collated utf8_unicode_ci

mysql-test/r/ctype_utf8.result

@@ -240,3 +240,6 @@ select 'zвася'  rlike '[[:<:]]вася[[:>:]]';
 select 'zвасяz' rlike '[[:<:]]вася[[:>:]]';
 'zвасяz' rlike '[[:<:]]вася[[:>:]]'
 0
+CREATE TABLE t1 (a enum ('Y', 'N') DEFAULT 'N' COLLATE utf8_unicode_ci);
+ALTER TABLE t1 ADD COLUMN b CHAR(20);
+DROP TABLE t1;

mysql-test/t/ctype_utf8.test

@@ -157,3 +157,11 @@ select ' вася ' rlike '[[:<:]]вася[[:>:]]';
 select  'васяz' rlike '[[:<:]]вася[[:>:]]';
 select 'zвася'  rlike '[[:<:]]вася[[:>:]]';
 select 'zвасяz' rlike '[[:<:]]вася[[:>:]]';
+
+#
+# Bug #4555
+# ALTER TABLE crashes mysqld with enum column collated utf8_unicode_ci
+#
+CREATE TABLE t1 (a enum ('Y', 'N') DEFAULT 'N' COLLATE utf8_unicode_ci);
+ALTER TABLE t1 ADD COLUMN b CHAR(20);
+DROP TABLE t1;

sql/field.cc

@@ -5625,8 +5625,11 @@ bool Field_enum::eq_def(Field *field)
   if (typelib->count < from_lib->count)
     return 0;
   for (uint i=0 ; i < from_lib->count ; i++)
-    if (my_strcasecmp(field_charset,
-                      typelib->type_names[i],from_lib->type_names[i]))
+    if (my_strnncoll(field_charset,
+                     (const uchar*)typelib->type_names[i],
+                     strlen(typelib->type_names[i]),
+                     (const uchar*)from_lib->type_names[i],
+                     strlen(from_lib->type_names[i])))
       return 0;
   return 1;
 }