From: Robert Klemme <bob.news@...>
Date: 2005-04-13T02:59:36+09:00
Subject: Re: ability to run finalizers at a given point of a program?


"Guillaume Cottenceau" <gcottenc@gmail.com> schrieb im Newsbeitrag 
news:dc3bf8580504120943240e01e4@mail.gmail.com...
> Hi,
>
> I'm considering the possibility to run the finalizers at a given point
> of a program. I have written the following program, and I'm
> experiencing the following unexpected behaviour: I call GC.start in
> the hope that finalizers of unscoped objects that have one will be
> run, but it seems they aren't.
>
> http://www.zarb.org/~gc/t/prog/destructor/nodestructor.rb

Apart from what Guy wrote already, why do you need to determine the point in 
time when finalizers are called?  The whole idea of GC and finalization is 
that you *don't* care when it happens.  If you need to ensure (hint, hint) 
that some cleanup code is invoked at some point in time then the 
transactional pattern employed by File.open() and others might be more 
appropriate:

def do_work
  x = create_x_somehow
  begin
    yield x
  ensure
    # always called, even in case of exception
    x.cleanup
  end
end

do_work do |an_x|
  puts an_x.to_u
end

And another remark: as opposed to Java finalizers, Ruby finalizers are 
guaranteed to be invoked, even on program exit:

$ ruby -e 'ObjectSpace.define_finalizer(Object.new){ puts "called" }'
called
$ ruby -e 'o=Object.new;ObjectSpace.define_finalizer(o){ puts "called" }'
called

Btw, you can also define exit handlers with at_exit:
http://www.ruby-doc.org/core/classes/Kernel.html#M001736

Kind regards

    robert