There was a post in 2008 (http://lists.boost.org/boost-users/2008/05/36589.php) about using a NULL cleanup function for thread_specific_ptr, but no response to the issue. It appears that there is now a special case in the code for thread_specific_ptr to not call NULL cleanup functions; is this official (and thus can be relied upon)? I did not see it mentioned in the documentation. -- Jeremiah Willcock