From: Robert Klemme <bob.news@...>
Date: 2006-02-05T20:08:20+09:00
Subject: Re: Problem with weak references on OS X 10.3

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Caleb Clausen <vikkous@gmail.com> wrote:
> On 2/4/06, Robert Klemme <shortcutter@googlemail.com> wrote:
>>> I now see that I also get the problem with my ruby 1.6 _if_ I run
>>> the test program within irb; without irb, it runs without problems.
>>
>> I would not count on IRB in such circumstances - especially if local
>> variables are involved. IRB does certain things differently there.
>> Did you only test in IRB or also in a Ruby script?
>
> It happens running it with plain ruby (no irb) on my ruby 1.8 (and
> 1.9). I only mentioned it because irb does seem to be required to
> create the problem on my ruby 1.6. Irb is not the problem; it doesn't
> treat local variables that differently.
>
>> Not so fast. This error you are seeing is absolutely expected:
>> i.__getobj__ returns the original instance. If that is not an object
>> id (which it isn't in your case) it's not a legal argument for
>> ObjectSpace._id2ref().
>>
>> You probably wanted o2=i.__getobj__
>
> Uh-oh. You're right. Too much monkey code and hack, not enough look
> and think.
>
> (After hurriedly fixing my test...) Ok, so if I _correctly_ use
> WeakRefs, there is no problem. That is interesting, and I'd sure like
> to know why, because it's not obvious to me. I'm going to investigate
> this deeper, and see if I isolate the difference that lets WeakRef
> work.
>
>> Since you keep a reference to o all the time in the block,
>> ObjectSpace._id2ref must always return the same instance. *If* you
>> actually see the error you claimed you saw initially then there's
>> something seriously broken.  At the moment I rather suspect it's some
>> other issue (such as testing in IRB).  I'd also try to use brackets
>> around the equality test - just to be sure that precedence doesn't
>> come into play.
>
> I'm pretty sure about the precedence of or, but just in case, I tried
> it with more parens. It's still broken.

I was also, but sometimes it's better to explicitely rule potential sources 
of error out.

I have to admit I still cannot believe that you actually saw the results you 
claimed to see initially.  Can anybody verify this on Mac OS please?  I 
don't have a Mac around otherwise I'd do it.  I've attached an equivalent 
version of the script.

Kind regards

    robert

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#!/usr/bin/env ruby=0A=
=0A=
print( (ARGV.shift || 1000).to_i.times do |i|=0A=
  o1 =3D Object.new=0A=
  id =3D o1.object_id=0A=
  o2 =3D ObjectSpace._id2ref id=0A=
  o1.equal? o2 or raise "#{i}: #{o1.inspect} #{o2.inspect} - #{id} =
#{o2.object_id}"=0A=
end, " runs\n" )=0A=

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