On Thu, 23 Oct 2003, Mike Pomraning wrote:
[....] suggestions on how I might determine which DESTROY [of a shared, blessed ref] is the very last one?
Sorry to reply to my own post, but here's how I've attempted to identify the last DESTROY of a shared object:
sub DESTROY { return unless threads::shared::_refcnt($_[0]) == 1; # if we're here, the shared object is going away for good. # time to release system resources, call XS deallocators, etc. } }
The only other approach I can think of is to do (ser|ted)ious inventorying via CLONE, DESTROY and constructors, or a wrapped bless. (I did see the "[CAUTION] Thread-saving modules" not-a-bug thread from Jul 2002 before my previous post, but this is not quite the same.)
The "inventory" approach is the one that Thread::Pool uses. But it may be simpler than you think:
There is a global that keeps the CLONE level:
our $cloned = 0;
Then this variable gets incremented with each clone:
sub CLONE { $cloned++ }
When an object gets created, it keeps the current cloned value with its information:
sub new {
bless {cloned => $cloned},$_[0];
}And then in DESTROY, you check whether they're still the same
sub DESTROY {
return unless $_[0]->{'cloned'} == $cloned;
# other stuff
}Multiple destruction of non-shared objects makes sense to me, as each becomes a thread-local copy. Multiple destruction of shared objects, however, does not (though I think I understand the mechanics of why it happens). Am I looking at this issue the wrong way?
Maybe the above is already what you have, maybe it is simpler. It works for Thread::Pool.
By the way, Thread::Pool also contains:
return unless UNIVERSAL::isa( $_[0],__PACKAGE__ ); # ignore rogue DESTROYs
I'm not sure this is needed for 5.8.1 and above. But it was definitely needed for 5.8.0.
Hope this helps.
Liz
