Re: Things you need to know before programming Perl ithreads

[Zaxo]

liz++, thanks.

I got curious about how closures would do, so I tried your technique to see what happens (perl 5.8.1-RC2),

use threads();

{
    my $foo = 'bar';
    sub foo () :lvalue { $foo }
}

threads->new(
    sub {
        foo = 'quux';
        print 'thread: coderef = ', \&foo, $/;
        print 'foo is ', foo, $/;
    }
)->join;

print 'main: coderef = ', \&foo, $/;
print 'foo is ', foo, $/;
__END__

$ perl thrcl.pl
thread: coderef = CODE(0x8129538)
foo is quux
main: coderef = CODE(0x8060674)
foo is bar

so the object of the closure is duplicated - you did say everything, but I had to check.

Now, what if I want all threads to see the same thing?

use threads();
use threads::shared;
{
    my $foo :shared = 'bar';
    sub foo () :lvalue { $foo }
}

threads->new(
    sub {
        foo = 'quux';
        print 'thread: coderef = ', \&foo, $/;
        print 'foo is ', foo, $/;
    }
)->join;

print 'main: coderef = ', \&foo, $/;
print 'foo is ', foo, $/;
__END__

$ perl thrcl.pl
thread: coderef = CODE(0x8163924)
foo is quux
main: coderef = CODE(0x80fe448)
foo is quux

so both foo()'s point to the same cloistered object.

Trying to stick the :shared attribute on sub foo did no good. I expected it to prevent duplication of the code, but perl smacked me down with,

$ perl thrcl.pl
Invalid CODE attribute: shared at thrcl.pl line 5
BEGIN failed--compilation aborted at thrcl.pl line 5.

I suspect I need to read some more of the fine manual.

After Compline,
Zaxo