Bug#42511 mysqld: ctype-ucs2.c:2044: my_strnncollsp_utf32: Assertion (tlen % 4) == 0' fai

Problem: trailing spaces were stripped using 8-bit code,
so the truncation result length was incorrect, which led
to an assertion failure.
Fix: using multi-byte safe code.

mysql-test/r/ctype_utf32.result

@@ -1114,5 +1114,18 @@ format(123,2,'no_NO')
 123,00
 DROP TABLE t1;
 #
+# Bug#42511 mysqld: ctype-ucs2.c:2044: my_strnncollsp_utf32: Assertion (tlen % 4) == 0' faied
+#
+CREATE TABLE t1 (
+b char(250) CHARACTER SET utf32,
+key (b)
+) ENGINE=MYISAM;
+INSERT INTO t1 VALUES ('d'),('f');
+SELECT * FROM t1 WHERE b BETWEEN 'a' AND 'z';
+b
+d
+f
+DROP TABLE t1;
+#
 # End of 5.5 tests
 #

mysql-test/t/ctype_utf32.test

@@ -818,6 +818,17 @@ SHOW CREATE TABLE t1;
 SELECT * FROM t1;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#42511 mysqld: ctype-ucs2.c:2044: my_strnncollsp_utf32: Assertion (tlen % 4) == 0' faied
+--echo #
+CREATE TABLE t1 (
+ b char(250) CHARACTER SET utf32,
+ key (b)
+) ENGINE=MYISAM;
+INSERT INTO t1 VALUES ('d'),('f');
+SELECT * FROM t1 WHERE b BETWEEN 'a' AND 'z';
+DROP TABLE t1;
+
 --echo #
 --echo # End of 5.5 tests
 --echo #

storage/myisam/mi_key.c

@@ -253,18 +253,17 @@ uint _mi_pack_key(register MI_INFO *info, uint keynr, uchar *key, uchar *old,
     pos=old;
     if (keyseg->flag & HA_SPACE_PACK)
     {
-      uchar *end=pos+length;
       if (type == HA_KEYTYPE_NUM)
       {
-	while (pos < end && pos[0] == ' ')
-	  pos++;
+        uchar *end= pos + length;
+        while (pos < end && pos[0] == ' ')
+          pos++;
+        length= (uint) (end - pos);
       }
       else if (type != HA_KEYTYPE_BINARY)
       {
-	while (end > pos && end[-1] == ' ')
-	  end--;
+        length= cs->cset->lengthsp(cs, (char*) pos, length);
       }
-      length=(uint) (end-pos);
       FIX_LENGTH(cs, pos, length, char_length);
       store_key_length_inc(key,char_length);
       memcpy((uchar*) key,pos,(size_t) char_length);