gistfile1.rbx

require 'rubygems'
require 'eventmachine'

GC.disable

def Object.finalizer info = nil
  proc{
    p [Time.now, :FINALIZER, info]
  }
end

class Test
  def initialize
    @abc = :def
  end
end

EM.run{

  def check_objects
    EM.add_periodic_timer(1) {
      GC.enable
      ObjectSpace.garbage_collect
      GC.disable

      c = 0
      ObjectSpace.each_object(Test){ c+=1 }
      p [Time.now, :OBJECTS, c]
    }
  end

  def test
    obj = Test.new
    ObjectSpace.define_finalizer obj, Object.finalizer(obj.inspect)

    prc = proc{ p obj; :done }
    ObjectSpace.define_finalizer prc, Object.finalizer(prc.inspect)
  end

  test
  check_objects

  # check_objects
  # test

}

__END__

calling check_objects, then test:

[Tue Sep 23 15:29:04 -0700 2008, :OBJECTS, 1]
[Tue Sep 23 15:29:05 -0700 2008, :FINALIZER, "#<Proc:0x0033da4c@-:35>"]
[Tue Sep 23 15:29:05 -0700 2008, :OBJECTS, 1]
[Tue Sep 23 15:29:06 -0700 2008, :OBJECTS, 1]
[Tue Sep 23 15:29:08 -0700 2008, :OBJECTS, 1]


calling test, then check_objects:

[Tue Sep 23 15:29:16 -0700 2008, :OBJECTS, 1]
[Tue Sep 23 15:29:17 -0700 2008, :FINALIZER, "#<Test:0x124d230 @abc=:def>"]
[Tue Sep 23 15:29:17 -0700 2008, :FINALIZER, "#<Proc:0x0033da4c@-:35>"]
[Tue Sep 23 15:29:17 -0700 2008, :OBJECTS, 0]
[Tue Sep 23 15:29:19 -0700 2008, :OBJECTS, 0]