Packages and symbol tables

[johnnywang]

(This is a continuation of XML::Generator problem in mod_perl, now I got rid of all the none relevant info)

I have a module Foo.pm:

package Foo;

package Foo::Bar;
use base 'Foo';

package Foo::Bar::Test;
use base 'Foo::Bar';

1;

My problem is that the above module loads ok in command line perl, but it fails in mod_perl (failed on the last "use base 'Foo::Bar'", it can't find the class Foo::Bar)

Is there a way to find out what symbols/packages have been loaded before that failed call? I tried the following:

package Foo;

package Foo::Bar;
use base 'Foo';

print "$_ => $Foo::{$_}\n" foreach keys %Foo::;

which in commandline produces:

Bar:: => *Foo::Bar::
VERSION => *Foo::VERSION 
Bar:: => *Foo::Bar::
isa => *Foo::isa
VERSION => *Foo::VERSION

but in mod_perl, it produces:

Bar:: => *Foo::Bar:: <br>
VERSION => *Foo::VERSION <br>

I guess my question is whether this is the right way to see whether the "Foo::Bar" package is loaded, and why mod_perl behaves differently? (perl 5.8.0, mod_perl 1.29, apache1.3.3)

In my real situation, the package is XML::Generator. To complicate the things further, I have another "identical" installation of perl/mod_perl/apache, where this works ok. I guess I'm trying to find out how to figure out what the difference is.

[Joost]

BEGIN { print "$_ => $Foo::{$_}\n" foreach keys %Foo::; }

is probably better in your specific case.

Anyway, my guess at what's going wrong is that base is trying to be clever in a way that you don't expect.

Since you're defining the packages in the same file, just drop the use base and do:

package Foo::Bar;
our @ISA = 'Foo';

[johnnywang]

Thanks Joost, your suggested change to use @ISA solved the problem (although I'm now on to the next one!) care to explain the thinking in your message?

[Jenda]

use base ... has two basic tasks. 1. make sure the module is loaded and 2. add the module into @INC. In your case you do not need the first so it's easiest to just do the second. Please see perldoc base.

[Anonymous Monk]

base.pm vs @ISA