On Sun, Oct 25, 2009 at 5:02 PM, Yukihiro Matsumoto <matz / ruby-lang.org> wrote:
> Originally, _id2ref is an implementation dependent hack for weakref,
> so that you can remove it, if you can provide the better way.

I suspected as much, since that seemed to be the primary place for it
to be used. I guess the remaining question is about the uniqueness of
object_id. I believe on Sun's JVMs java.lang.System.identityHashcode
of an object will be unique for the lifetime of the object, but not
unique forever (which I'm sure is the case on MRI). However, I don't
think there's any guarantee that the identityHashCode will be unique
across JVMs, though the documentation says an implementation should
make a "best effort" to keep it unique.

We will look at removing _id2ref in 1.5 (or making it do nothing, with
a warning) as well as modifying the one stdlib that uses it (DRb, for
reasons I have not yet explored). And I will explore whether
identityHashcode will be "unique enough" as I suspect it should be.

- Charlie