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Prevent object from cloning

by menth0l (Monk)
on Oct 18, 2010 at 09:06 UTC ( #865899=perlquestion: print w/ replies, xml ) Need Help??
menth0l has asked for the wisdom of the Perl Monks concerning the following question:

Hi, Is there any way to prevent cloning an object/class of objects from being cloned while creating new thread? When i do something like:
package MyPackage; use threads; use threads::shared; { use Object::InsideOut qw(:NOT_SHARED); }; package main; use threads; my $o = new MyPackage; threads->create(\&th)->join(); sub th { my $o1 = new MyPackage; }
i get:
ERROR: Attempt to DESTROY object ID 1 of class MyPackage twice ERROR: Attempt to DESTROY object ID 1 of class MyPackage twice Scalars leaked: 1
I assume that new thread copies $o (id = 1) into its scope and then tries to destroy it at the and along with $o1 which have the same id (1) since it's just cloned version of $o. Now, how can i prevent this? One way would be to create o _after_ thread is created (but that limits ways of using 'MyPackage' and i don't want that). Second: ensuring that $o1 would get new id (but how?). Third: ensuring that new thread would get undef as a $o value so that destroy method would not be invoked (but once again: how?). Of course i could mark MyPackage as :SHARED but in my real app this class consist of fields which are classes that cannot be shared. So, is there any other way to get rid of those annoying memory leaks?

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Re: Prevent object from cloning
by Corion (Pope) on Oct 18, 2010 at 09:22 UTC

    Are you really wedded to inside-out objects? I'm not aware of any approach that works well with objects spawned in threads and objects spawned (and cloned) outside of threads. I would throw out Object::Insideout and use plain objects instead.

Re: Prevent object from cloning
by BrowserUk (Pope) on Oct 18, 2010 at 09:23 UTC
      Adding CLONE_SKIP to MyPackage results in abnormal thread termination. This is what i caught using eval:
      OIO error: panic: del_backref at C:/Perl/site/lib/Object/InsideOut.pm +line 1305. Package: main File: C:\Development\workspace\ebi.ds.lite\_Scripts\bug.pl Line: 27 Subsequent to the above, the following error also occurred: OIO error: panic: del_backref at C:/Perl/site/lib/Object/InsideOut +.pm line 1883. Package: main File: C:\Development\workspace\ebi.ds.lite\_Scripts\bug.pl Line: 27 Trace begun at C:\Perl\site\lib\Object\InsideOut.pm line 1942 Object::InsideOut::DESTROY('MyPackage=SCALAR(0x1ba3b0c)') called at C: +\Development\workspace\ebi.ds.lite\_Scripts\bug.pl line 27 eval {...} at C:\Development\workspace\ebi.ds.lite\_Scripts\bug.pl lin +e 27 main::th at C:\Development\workspace\ebi.ds.lite\_Scripts\bug.pl line +22 eval {...} at C:\Development\workspace\ebi.ds.lite\_Scripts\bug.pl lin +e 22 Unbalanced string table refcount: (1) for "1" during global destructio +n. Scalars leaked: 1
      This class have to be implemented via OIO and i can't fallback on classic hashref based object.
        Adding CLONE_SKIP to MyPackage results in abnormal thread termination.

        Contact the author of Object::InsideOut and report the bug.

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