From: Michael Neumann <mneumann@...>
Date: 2004-10-25T17:58:41+09:00
Subject: Re: Forcing a GC run

On Mon, Oct 25, 2004 at 10:39:47AM +0900, Bill Atkins wrote:
> How exactly did that happen?  I'm confused. :)

A finalizer was not invoked at life-time... ah, hard to explain, see
yourself:

  def take_snapshot
    snap = []
    ObjectSpace.define_finalizer(snap, proc {
      p "finalizer called"
    })
    return snap
  end

  # BE CAREFUL! Might freeze your computer!
  loop do
    p "snap"
    take_snapshot
  end

Memory consumption will grow towards infinity. Why? Probably because the
proc, as it's a closure, implicitly references the snap object, and as
such, snap will never be recycled.

Whereas the following works fine:

  $fin = proc { p "finalizer called" }
  def take_snapshot
    snap = []
    ObjectSpace.define_finalizer(snap, $fin)
    return snap
  end

  loop do
    p "snap"
    take_snapshot
  end

Regards,

  Michael