undefined value and orphaned memory with IPC::Shareable

dime has asked for the wisdom of the Perl Monks concerning the following question:

Question about an earlier post (Hash of Hashes Shared Across Parallel Forks Orphans Memory).

I had the same problem with IPC::Shareable as the person in the above-mentioned post, namely orphaned memory with IPC::Shareable. I side-stepped it by using an array instead of a hash. But frankly, I don't understand why that would help. And how/why does the mentioned solution improve things?

Maybe an answer will help with my current problem as well, but in case it doesn't: I have a loop which is supposed to add to said array, but if it ends up empty, the program dies with

Can't use an undefined value as an ARRAY reference at .../Shareable.pm line 446.

at the simple check

if (@array) {...}

Why can't I check if the array is empty? Here's a very short version of what I have:

use IPC::Shareable (':lock');

my @arr;
my %options = (
                 create => 'yes',
                 mode => 0644,
                 exclusive => 0,
                 destroy => 'yes'
               );
my $handle = tie @arr, 'IPC::Shareable', 'dat1', { %options } or die "
+Tie failed.\n";

#...

if (@arr) {
    #...
}
[download]

What do I need to change to make this work? Any help would be very much appreciated.

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Re: undefined value and orphaned memory with IPC::Shareable by perreal (Monk) on Jul 29, 2009 at 12:03 UTC
The error is not because you are checking an empty array. It comes from Shareable.pm, line 446: `446: return scalar(@{$self->{_data}});` [download] I'd say your $self->{_data} is not defined at this point. you can just assign an empty list to prevent this: `use IPC::Shareable (':lock'); my @arr; my %options = ( create => 'yes', mode => 0644, exclusive => 0, destroy => 'yes' ); my $handle = tie @arr, 'IPC::Shareable', 'dat1', { %options } or die " +Tie failed.\n"; @arr = (); # INITIALIZE <----------- if (@arr) { print "NOT empty\n"; }` [download]	[reply] [d/l] [select]

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Re: undefined value and orphaned memory with IPC::Shareable
by perreal (Monk) on Jul 29, 2009 at 12:03 UTC

446: return scalar(@{$self->{_data}});
[download]

use IPC::Shareable (':lock');

my @arr;
my %options = ( 
                 create => 'yes',
                 mode => 0644,
                 exclusive => 0,
                 destroy => 'yes'
               );  
my $handle = tie @arr, 'IPC::Shareable', 'dat1', { %options } or die "
+Tie failed.\n";

@arr = (); # INITIALIZE <-----------

if (@arr) {
        print "NOT empty\n";
}
[download]

[reply]
[d/l]
[select]