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Postings from February 2001
On Thu, Feb 15, 2001 at 08:07:39AM -0300, Branden wrote:
> I think you just said all about why we shouldn't bother giving objects
> deterministic finalization, and I agree with you. If we explicitly want to
> free resources (files, database connections), then we explicitly call close.
> Otherwise, it will be called when DESTROY is eventually called.
No, the question of whether Perl 6 wants deterministic finalization
or not is a separate one. If it doesn't have it, we will be losing
a very common Perl idiom:
{
my $fh = IO::File->new("file");
print $fh $data;
}
It's nice to know that when the above block exits, $fh will be closed.
Remember that "closed" doesn't just refer to freeing the resources
associated with it -- it also includes flushing buffers and the like.
Without deterministic finalization, you will almost always want to
write the above to include an explicit $fh->close(). The problem is
that you can not only count on $fh's DESTROY being called at the end of
the block, you often can't count on it ever happening. Consider the
case where the interpreter dies on a signal, for example -- DESTROY
methods will quite possibly not be called.
I'm not certain that Perl should lose deterministic finalization. On
the other hand, I really wish that Perl had a more modern GC scheme,
if only so that circular structures could be properly collected. In
the end, however, I don't think that any of our opinions will decide
this -- either Dan's forthcoming PDD will show how Perl 6 can have
its cake and eat it too, or Larry will decide.
- Damien
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