Re: Apache::Reload/ModPerl::Util/base.pm incompatibility prospective patch

["Philippe M. Chiasson" <go...@ectoplasm.org>]

Have you tried the alternate unload_package implementation, the one in C/XS?

You can try it out by doing

BEGIN {
   $ModPerl::Util::DEFAULT_UNLOAD_METHOD = 'unload_package_xs';
}
use ModPerl::Util;

Somewhere early in your server startup scripts.

On 29/12/08 15:08, David Ihnen wrote:
> Philip M. Gollucci wrote:
>> David Ihnen wrote:
>>> 1. Problem Description:
>>>
>>> While developing with CGI::Application and utilizing Apache::Reload,
>>> we encountered an issue where our modules were not being succesfully
>>> reinitialized on reload. It was traced down to @ISA not containing
>>> the proper values after a 'use base' directive, but only on automatic
>>> reload, and freshly on perl 5.10, not our previous version of perl
>>> 5.8.8!
>> Are you able to try 5.8.9, its at least a smaller change set to look
>> at if 5.8.9 breaks too.
>>
> No, not easily when I considered the mod_perl ramifications
> particularly. I did find a way around this particular problem on the web
> server though.
>
> I noticed line 79. of base.pm
>
> 79 next if grep $_->isa($base), ($inheritor, @bases);
>
> Experimentally, if I commented it out, the web server could reload
> properly! Score!
>
> Hm. I know ->isa is a UNIVERSAL function. UNIVERSAL.pm is... not
> implimented in perl. Must be in the C code.
>
> So I found UNIVERSAL.c
>
> whose isa function implimentation said after some error checks essentially
>
> ST(0) = boolSV(sv_derived_from(sv, name));
>
>
> which function had the documentation
>
> =head1 SV Manipulation Functions
>
> =for apidoc sv_derived_from
>
> Returns a boolean indicating whether the SV is derived from the specified class
> I<at the C level>.  To check derivation at the Perl level, call C<isa()>  as a
> normal Perl method.
>
> =cut
>
>
> Ooh. at the **C** level. I bet the unload utility doesn't even *affect*
> the C level!
>
> Those who understand perl C code might be better able to tell if
> unloading in the C levels is possible, a good idea, or just bad mojo.
> Having taken some medicine to deal with the C-inspired headache that
> inspection brought on, I returned to base.pm.
>
> ISA is a package local variable list that lists the parents. In order to
> see all-the-parents, or replicate ->isa, I have to get the list of all
> the packages in ISA, all THEIR ISAs, and so on, as long as there are
> contents therein. And my scan will pay attention only to the interpreter
> state, not the C state...
>
> I should be able to do that in perl easily enough. PATCH
>
> --- 510base.pm 2008-12-29 12:48:27.000000000 -0700
> +++ /usr/share/perl/5.10.0/base.pm 2008-12-29 12:48:48.000000000 -0700
> @@ -76,7 +76,20 @@
> warn "Class '$inheritor' tried to inherit from itself\n";
> }
>
> - next if grep $_->isa($base), ($inheritor, @bases);
> + my @classlist = ($inheritor, @bases);
> + foreach ($inheritor, @bases) {
> + my @parents = @$_::ISA;
> + do {
> + my $class = shift @parents;
> + foreach my $parent (@$class::ISA) {
> + unless (grep { $_ eq $parent } @classlist) {
> + push @classlist, $parent;
> + push @parents, @$parent::ISA;
> + }
> + }
> + } while (scalar @parents);
> + }
> + next if grep {$_ eq $base} @classlist;
>
> if (has_version($base)) {
> ${$base.'::VERSION'} = '-1, set by base.pm'
>
> I know thats kind of ugly, and verbose, and maybe not very performant.
> But it works for the web server. Its not in any of the ISAs at
> re-require time so it does not skip loading the module even if the C HAS
> seen it before, and the application continues happily.
>
> So at any rate, its a patch that works for my case (much as I hate
> patching base.pm) - and to my somewhat weak understanding of the C code
> implimentation, does the same thing in perl that the isa-iteration did
> in c. What is the proper path here?
>
> David Ihnen
> Perl Programmer
> Norchem Laboratories, Inc
>

-- 
Philippe M. Chiasson     GPG: F9BFE0C2480E7680 1AE53631CB32A107 88C3A5A5
http://gozer.ectoplasm.org/       m/gozer\@(apache|cpan|ectoplasm)\.org/