blead and Glib's lazy-loader

[Torsten Schoenfeld <kaffeetisch@gmx.de>]

Aloha,

it looks like current bleadperl breaks Glib's lazy-loading scheme.  This 
happened once before with perl 5.10: 
<http://markmail.org/message/dp27effje5arxgsc>.  The problem then was that we 
called av_clear on an @ISA array, which broke mro's idea of the hierarchy.  We 
switched to using av_shift repeatedly to fix this.

The current code (which works with perl 5.8 and perl 5.10 but breaks with blead) 
basically looks like this[1]:

	AV * isa = get_av("Some::ISA", FALSE);
	AV * new_isa = newAV ();

	for (i = 0 ; i < av_len (isa) + 1 ; i++) {
		SV * sv = av_shift (isa);
		...
		av_push (new_isa, "Something");
		sv_free (sv);
	}

	for (i = 0 ; i < av_len (new_isa) ; i++) {
		SV ** svp = av_fetch (new_isa, i, FALSE);
		av_push (isa, SvREFCNT_inc (*svp));
	}

	av_clear (new_isa);
	av_undef (new_isa);

This code is invoked whenever isa() or similar is called on a package which is 
set up for lazy-loading.  It seems that this time, the code only breaks when 
there are multiple layers of inheritance: the attached lazy-test-v3-good.pl 
works fine even with blead, whereas lazy-test-v3.pl breaks with blead (but works 
fine with perl 5.8 and 5.10).

Does anyone have any insights?

-Torsten

[1] The full code is in <http://search.cpan.org/src/TSCH/Glib-1.200/GObject.xs>, 
function class_info_finish_loading.  The failing test is 
<http://search.cpan.org/src/TSCH/Glib-1.200/t/lazy-loader.t>.
#!/usr/bin/perl
use strict;
use warnings;
use Glib;

@Foo::ISA = qw(Glib::InitiallyUnowned);

dump_hierarchy (Foo::);
warn Foo->isa('Glib::Object');
dump_hierarchy (Foo::);
warn Foo->isa('Glib::Object');

# force the lazy loader to setup the hierarchy
my $object = Glib::InitiallyUnowned->new ();

sub dump_hierarchy {
  my ($package, $indent) = @_;
  $indent ||= 0;

  print ' ' x $indent, $package, "\n";

  no strict 'refs';
  foreach my $parent (@{$package . '::ISA'}) {
    dump_hierarchy ($parent, $indent + 2);
  }
}
#!/usr/bin/perl
use strict;
use warnings;
use Glib;

dump_hierarchy (Glib::InitiallyUnowned::);
warn Glib::InitiallyUnowned->isa('Glib::Object');
dump_hierarchy (Glib::InitiallyUnowned::);
warn Glib::InitiallyUnowned->isa('Glib::Object');

# force the lazy loader to setup the hierarchy
my $object = Glib::InitiallyUnowned->new ();

sub dump_hierarchy {
  my ($package, $indent) = @_;
  $indent ||= 0;

  print ' ' x $indent, $package, "\n";

  no strict 'refs';
  foreach my $parent (@{$package . '::ISA'}) {
    dump_hierarchy ($parent, $indent + 2);
  }
}

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