Issue #4168 has been updated by Charles Nutter. Given proper WeakReference and ReferenceQueue implementations (the latter we still don't for C, I believe), implementing weak-keyed or weak-valued hashes becomes trivial. See my "weakling" gem for an example that uses Java WeaReference/ReferenceQueue. Without ReferenceQueue, WeakReference is much less useful. You are forced to constantly scan lists/maps/etc for dead links. ---------------------------------------- http://redmine.ruby-lang.org/issues/show/4168 ---------------------------------------- http://redmine.ruby-lang.org