Using 8 bytes for data pointer does not work at least on
all computers. The result may become 0 or negative number.
(mysqld, myisamchk)
 


myisam/mi_create.c:
  Fixed Bug#11226, "Dynamic table >4GB issue".
mysql-test/r/variables.result:
  Restricted myisam_data_pointer_size back to 7.
mysql-test/t/variables.test:
  Restricted myisam_data_pointer_size back to 7.
sql/mysqld.cc:
  Restricted myisam_data_pointer_size back to 7.