From: Giles Bowkett <gilesb@...>
Date: 2006-04-18T04:22:16+09:00
Subject: Re: IO not closed by GC

I have a question abt this GC stuff, tangential to the challenge
itself, so million pardons, but I see this in many languages -- it's
always a suggestion rather than a requirement. Is this just to trip up
incautious programmers with shallow understanding? Or is it a hook for
special cases when you want to override that stuff w/custom memory
mgmt? What's the benefit? I've seen so much use of this type of
command in bad Java and virtually never seen ppl using it anywhere
else. I guess I sound kind of aggressive or critical but it's a common
decision among language designers so there must be some reason for it.
(Also apologies for the brevity, I'm on my mobile.)


Giles




On 4/17/06, Gennady Bystritsky <Gennady.Bystritsky@quest.com> wrote:
> Even GC.start does not guarantee that the garbage collection will be
> actually started, it is just a hint after all. And I am not sure that
> even when an IO object is being garbage collected, there will be an
> implicit call to close(). I personally would not expect it as no
> finalizers are installed by default.
>
> So the programmer must take care to write the correct code, short or
> long ;-).
>
> Even if GC.start helped in your case, the overall code would be longer
> (because of calls to GC.start) and work much worse (as GC does a lot
> that you may not need for the moment) than what I have suggested. And
> using blocks with popen is GUARANTEED to close descriptors properly. See
> my point?
>
> By the way, you are welcome.
>
> Gennady.
>
> > -----Original Message-----
> > From: Stephan Maka [mailto:stephan@spaceboyz.net]
> > Sent: Monday, April 17, 2006 10:37
> > To: ruby-talk ML
> > Subject: Re: IO not closed by GC
> >
> > Gennady Bystritsky wrote:
> > > But you do not even know when GC will be run, so in your
> > case it might
> >
> > Inserting 'GC.start; sleep 1' won't help...
> >
> > > not even have kicked in. On the other hand, IO.popen has a
> > nice block
> > > form that gurantees that an underlying IO object will be closed
> > > properly. You can rewrite your code as:
> > >
> > > os = IO.popen('uname -sr') { |io| io.readlines.to_s.strip }
> >
> > That works, but is longer. Shorter code is more readable in general...
> >
> > Anyway, I think an IO object should be closed when not being
> > needed anylonger.
> >
> >
> > Stephan.
> >
>
>


--
Giles Bowkett
http://www.gilesgoatboy.org