Limit join_buffer_size, sort_buffer_size and myisam_sort_buffer_size to 4GB on all platforms, since the related code in 5.0 is not 64-bit safe. This is patch is a part of work on bug #5731 and will be null-merged to 5.1.


sql/mysqld.cc:
  Limit join_buffer_size, sort_buffer_size and myisam_sort_buffer_size to 4GB on all platforms.