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Postings from November 2009
On Tue, Nov 17, 2009 at 2:27 PM, David Nicol <davidnicol@gmail.com> wrote:
> 1: are there situations where a RAIL object will be the subject of one of
> these functions?
> (resource acquisition is locking is the big design pattern that relies on
> timely destruction)
>
Yes.
I previously gave the following example which demonstrates resources being
help until global destruction (marked by "G") rather than being released
timely:
# Timely release
>perl -le"{ my $x=''; $x = bless {}; } print 'G'; DESTROY { print 'D' }"
D
G
# Resource held until global destruction
>perl -le"{ my $x=''; vec($x,0,1)=0; $x = bless {}; } print 'G'; DESTROY {
print 'D' }"
G
D
Here's an example that uses lvalue keys(%h) in the most straightforward
manner:
perl -le'
sub init {
my %h;
keys(%h) = @_;
%h = map { $_ => bless {} } @_;
return \%h;
}
DESTROY { print "D" }
{ my $h = init(qw(a b c)); }
print "G";
'
GDDD
2: can TARG be a weak reference using current weak reference technology?
>
That was mentioned earlier in this thread, and seems from a high and distant
> level to be the way to go.
>
Yes, I believe so.
What's wrong with that suggestion?
The only downside is overhead. It makes yet another variable magical (the
var passed as an arg). I can write up a patch tonight if you wish.
Should I only use weaken when necessary (lvalue subs)?
When does TARG hold the last reference to something,
>
See the reply to your first question.
can TARG manipulation stuff simply leave reference counts alone?
>
If these ops couldn't be used as the return value for lvalue subs, I believe
we could do forgo ref counting. I don't think that's a condition we can
meet.
Eric
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