[BUG] Strange weak-ref behaviour

[Michael Neumann]

Hi. Take a look at the source code at the end of the email and run it.
The expected output for me is, either an empty string ("") or nothing
(and this up to 1000 times). But, the output I get (on both Ruby 1.8.x
and 1.9) is like that shown below:

"w.rb:16:in `_id2ref'"
["w.rb:16:in `_id2ref'", "w.rb:16:in `each_object'", "w.rb:14:in
`each'", "/home/mneumann/usr/lib/ruby/1.9/set.rb:193:in `each_key'",
"/home/mneumann/usr/lib/ruby/1.9/set.rb:193:in `each'", "w.rb:14:in
`each_object'", "w.rb:30"]
"w.rb:16:in `_id2ref'"
"/home/mneumann/usr/lib/ruby/1.9/set.rb:193:in `each'"
"/home/mneumann/usr/lib/ruby/1.9/set.rb:193:in `each_key'"
"w.rb:14:in `each'"
#<RangeError: 0x4086550 is recycled object>
["w.rb:16:in `_id2ref'", "w.rb:16:in `each_object'", "w.rb:14:in
`each'", "/home/mneumann/usr/lib/ruby/1.9/set.rb:193:in `each_key'",
"/home/mneumann/usr/lib/ruby/1.9/set.rb:193:in `each'", "w.rb:14:in
`each_object'", "w.rb:30"]
#<RangeError: 0x4084e1c is recycled object>
"w.rb:14:in `each'"
"w.rb:14:in `each_object'"
"w.rb:14:in `each'"
"w.rb:16:in `_id2ref'"
"w.rb:14:in `each_object'"
"w.rb:30"

There must be something wrong, or is this correct? Does Ruby reuse
object_id's? BTW, what happens if an application uses more than 4 billon
(32-bit) objects? Does Ruby fail or reuse old object_ids?

Thanks in advance.

Regards,

Michael


#################################
# here the code. if no output is shown, try to
# increase the number of objects registered (1000)
#
require 'set'

class StateRegistry

def initialize
@registered_objects = Set.new
end

def register(obj)
@registered_objects.add(obj.object_id)
end

def each_object
@registered_objects.each do |oid|
begin
obj = ObjectSpace._id2ref(oid)
rescue RangeError
next
end
yield obj
end
end
end

s = StateRegistry.new
1000.times do
s.register("")
end
ObjectSpace.garbage_collect
s.each_object {|obj| p obj}

 

[ts]

M> There must be something wrong, or is this correct?

correct.

M> Does Ruby reuse object_id's?

it can


Guy Decoux

 

[Michael Neumann]

M> There must be something wrong, or is this correct?

correct.

Excuse my stupidity. Of course I should define a finalizer (and should
not write emails that early in the morning .

Regards,

Michael

 

[Markus]

I may be confused, but I do not see where you are even using using
weak-refs. It looks like you are doing something like this:

* 1000 times
* Making an object
* Noting its id
* Setting it free to wander in the woods unreferenced
* Sending the wolf into the woods to hunt unreferenced objects
* Calling for it by id
* Being surprised to hear that it is no longer with us

This does not look like a bug to me (I wouldn't expect them to answer
after I've set the wolf on them), but I may be misunderstanding.

-- Markus

 

[Michael Neumann]

I may be confused, but I do not see where you are even using using
weak-refs. It looks like you are doing something like this:

* 1000 times
* Making an object
* Noting its id
* Setting it free to wander in the woods unreferenced
* Sending the wolf into the woods to hunt unreferenced objects
* Calling for it by id
* Being surprised to hear that it is no longer with us

This does not look like a bug to me (I wouldn't expect them to answer
after I've set the wolf on them), but I may be misunderstanding.

Correct. It isn't a bug! I got confused, as I thought, object_id's would
not be reused.

Regards,

Michael