Thanks to those who replied to my query about readdir and thread safety. I've dug around a bit, read the POSIX spec for readdir_r, and come up with the implementation in the attached patch. It basically just adds a mutex gizmo to the directory stream structure and puts a lock on it while calling the ordinary readdir and assigning return values. All tests pass with a threaded build of this on top of maintperl@19035 (though they did before the patch as well). To really stress test this with multiple threads going after the same directory stream I'd need an SMP machine to test on, which I don't have. But I think we are at least somewhat safer than we were before. The affected files are: configure.com vms/vms.c vms/vmsish.h