can't lock an object from a base class in a derived class

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

Hi,

I'm trying to split a large chunk of code that uses shared variables and I can't get past the error "lock can only be used on shared values". Here's the reduced version of that code, in two files:

***mybase.pm:

package mybase;
use threads;
use threads::shared;

my $mode : shared;
1;
[download]

***derived.pm:

#!/usr/bin/perl
package derived;
use strict;
use Exporter;
use threads;
use threads::shared;
use mybase;
use vars qw(@ISA);
@ISA = ('mybase');

sub foo {
lock($mybase::mode);
$mybase::mode = 1;
}

foo();
1;
[download]

***

[root@nf-power2 perltest]# ./derived.pm
lock can only be used on shared values at ./derived.pm line 12.
[download]

Any ideas on why a variable declared as shared is not appearing as a one?

Thanks,
b

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Re: can't lock an object from a base class in a derived class by Corion (Patriarch) on Jun 05, 2008 at 20:24 UTC
You're using two different variables. In `mybase` you declare a lexical variable named `$mode` : `my $mode : shared;` [download] ... but in the package `derived`, you try to access a global variable named `$mode`: `$mybase::mode = 1;` [download] The two variables are different (and the lexical variable is unreachable from `derived` anyway) and hence Perl complains.	[reply] [d/l] [select]