Object::InsideOut leaks memory when using threads::shared

[menth0l]

It's my first post here... so hello ;) I have a big problem with memory leaks when using Object::InsideOut with threads::shared (ActiveState Perl 5.10.1, threads::shared 1.34, Object::InsideOut 3.69). Consider this code:

package Test;

use threads;
use threads::shared;

{
       use Object::InsideOut;

       my @dummy :Field;
}

package main;

while (1)
{
       my $o = new Test;
}

On my machine it constantly grows :/ One would assume that each created object will be destroyed (which is actually happening: :Init and :Destroy methods get to be called) and memory reused (which does not happen!). Interesting thing about that is when i comment out "use threads::shared" line it works fine. Memory usage is constant. The same is true when i implement package Test with classic hash-based class: no memory leaks. It's very important for me to solve this without abandoning OIO as 99% of my app is based on it. So: is it a bug in OIO? Or maybe in threads::shared? Will be gratefull for any help..

[BrowserUk]

As the author of Object::InsideOut, is also the maintainer of threads & threads::shared, you should contact him. If he cannot fix it, probably no one can.

[menth0l]

Yeah, i've sent him an e-mail but i got no answer yet. Since i've a deadline ahead i try to find answer in other sources...

Maybe someone had the same problem as me? Or can someone at lest try to run this code and say whether it leaks on his/her machine? I would be very gratefull.

[BrowserUk]

Or can someone at lest try to run this code and say whether it leaks on his/her machine? I would be very gratefull.

I confirm that your test code leaks at a rate of about 1.5MB/s here (I've printed out the versions I have):

#! perl -slw
{
    package Test;
    use Object::InsideOut;

    my @dummy :Field;
}

package main;
use threads;
use threads::shared;

print $];
print $threads::VERSION;
print $threads::shared::VERSION;
print $Object::InsideOut::VERSION;

while (1) {
       my $o = new Test;
}

__END__
c:\test>junk66
5.010001
1.76
1.33
3.69

You'll see I've tried swapping things around a bit to see if it made any difference (having read the following in the O::IO docs:

If you receive an error similar to this: ERROR: Attempt to DESTROY object ID 1 of class Foo twice

the cause may be that some module used by your application is doing require threads somewhere in the background. DBI is one such module. The workaround is to add use threads; at the start of your application.

The only thing that prevented the leak was to comment out use threads::shared as you've already discovered.

I took a (brief) look inside, but that requires a PhD in O'Woe, and I failed my masters in that subject :)

[zentara]

If you are at the point of grasping at straws, trying to forcefully destroy the object's refcount may work.

See Memory Leak? i'm clueless. for Object::Destroyer

and Memory leaks and circular references for Scalar::Util 'weaken'; Hope it helps.

Just as a hack, you might try to see if reusing your scalar $o, stops the memory gain.

my $o;
  while (1)
  {
       $o = new Test;
  }

[menth0l]

Jerry D. Hedden has already answered to my bug report. He states that:


(...)it's not an OIO bug. It's a problem with the perl interpreter and/or threads::shared.

He managed though to fix this in new OIO version that he ut on CPAN (1.71):
http://cpansearch.perl.org/src/JDHEDDEN/Object-InsideOut-3.71/Changes

Thank you all for help and thanks to Jerry for quick reaction!

[BrowserUk]

it's not an OIO bug. It's a problem with the perl interpreter and/or threads::shared.

Interesting fix/workaround:

@@ -634,19 +634,23 @@
 
     # Save deleted IDs for later reuse
     my $reuse = $GBL{'id'}{'reuse'};
+    lock($reuse) if $GBL{'share'}{'ok'};
     if ($id) {
-        lock($reuse) if $GBL{'share'}{'ok'};
         if (! exists($$reuse{$tree})) {
             $$reuse{$tree} = make_shared([]);
         }
         my $r_tree = $$reuse{$tree};
         if (! exists($$r_tree[$thread_id])) {
-            $$r_tree[$thread_id] = make_shared({});
-        } elsif (exists($$r_tree[$thread_id]{$id})) {
-            warn("ERROR: Duplicate reclaimed object ID ($id) in class
+ tree for $tree in thread $thread_id\n");
-            return;
+            $$r_tree[$thread_id] = make_shared([]);
+        } else {
+            foreach  (@{$$r_tree[$thread_id]}) {
+                if ($_ == $id) {
+                    warn("ERROR: Duplicate reclaimed object ID ($id) 
+in class tree for $tree in thread $thread_id\n");
+                    return;
+                }
+            }
         }
-        $$r_tree[$thread_id]{$id} = $id;
+        push(@{$$r_tree[$thread_id]}, $id);
         return;
     }
 
@@ -654,9 +658,9 @@
     if (exists($$reuse{$tree}) &&
         exists($$reuse{$tree}[$thread_id]))
     {
-        keys(%{$$reuse{$tree}[$thread_id]});
-        if ((my $id) = each(%{$$reuse{$tree}[$thread_id]})) {
-            return (delete($$reuse{$tree}[$thread_id]{$id}));
+        my $id = pop(@{$$reuse{$tree}[$thread_id]});
+        if (defined($id)) {
+            return $id;
         }
     }