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Filename : EndOfScope.pm
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package B::Hooks::EndOfScope; # git description: 0.27-8-gbe15c53
# ABSTRACT: Execute code after a scope finished compilation
# KEYWORDS: code hooks execution scope

use strict;
use warnings;

our $VERSION = '0.28';

use 5.006001;

BEGIN {
  use Module::Implementation 0.05;
  Module::Implementation::build_loader_sub(
    implementations => [ 'XS', 'PP' ],
    symbols => [ 'on_scope_end' ],
  )->();
}

use Sub::Exporter::Progressive 0.001006 -setup => {
  exports => [ 'on_scope_end' ],
  groups  => { default => ['on_scope_end'] },
};

1;

__END__

=pod

=encoding UTF-8

=head1 NAME

B::Hooks::EndOfScope - Execute code after a scope finished compilation

=head1 VERSION

version 0.28

=head1 SYNOPSIS

    on_scope_end { ... };

=head1 DESCRIPTION

This module allows you to execute code when perl finished compiling the
surrounding scope.

=head1 FUNCTIONS

=head2 on_scope_end

    on_scope_end { ... };

    on_scope_end $code;

Registers C<$code> to be executed after the surrounding scope has been
compiled.

This is exported by default. See L<Sub::Exporter> on how to customize it.

=head1 LIMITATIONS

=head2 Pure-perl mode caveat

This caveat applies to B<any> version of perl where L<Variable::Magic>
is unavailable or otherwise disabled.

While L<Variable::Magic> has access to some very dark sorcery to make it
possible to throw an exception from within a callback, the pure-perl
implementation does not have access to these hacks. Therefore, what
would have been a B<compile-time exception> is instead B<converted to a
warning>, and your execution will continue as if the exception never
happened.

To explicitly request an XS (or PP) implementation one has two choices. Either
to import from the desired implementation explicitly:

 use B::Hooks::EndOfScope::XS
   or
 use B::Hooks::EndOfScope::PP

or by setting C<$ENV{B_HOOKS_ENDOFSCOPE_IMPLEMENTATION}> to either C<XS> or
C<PP>.

=head2 Perl 5.8.0 ~ 5.8.3

Due to a L<core interpreter bug
|https://rt.perl.org/Public/Bug/Display.html?id=27040#txn-82797> present in
older perl versions, the implementation of B::Hooks::EndOfScope deliberately
leaks a single empty hash for every scope being cleaned. This is done to
avoid the memory corruption associated with the bug mentioned above.

In order to stabilize this workaround use of L<Variable::Magic> is disabled
on perls prior to version 5.8.4. On such systems loading/requesting
L<B::Hooks::EndOfScope::XS> explicitly will result in a compile-time
exception.

=head2 Perl versions 5.6.x

Versions of perl before 5.8.0 lack a feature allowing changing the visibility
of C<%^H> via setting bit 17 within C<$^H>. As such the only way to achieve
the effect necessary for this module to work, is to use the C<local> operator
explicitly on these platforms. This might lead to unexpected interference
with other scope-driven libraries relying on the same mechanism. On the flip
side there are no such known incompatibilities at the time this note was
written.

For further details on the unavailable behavior please refer to the test
file F<t/02-localise.t> included with the distribution.

=head1 SEE ALSO

L<Sub::Exporter>

L<Variable::Magic>

=head1 SUPPORT

Bugs may be submitted through L<the RT bug tracker|https://rt.cpan.org/Public/Dist/Display.html?Name=B-Hooks-EndOfScope>
(or L<bug-B-Hooks-EndOfScope@rt.cpan.org|mailto:bug-B-Hooks-EndOfScope@rt.cpan.org>).

=head1 AUTHORS

=over 4

=item *

Florian Ragwitz <rafl@debian.org>

=item *

Peter Rabbitson <ribasushi@leporine.io>

=back

=head1 CONTRIBUTORS

=for stopwords Karen Etheridge Graham Knop Christian Walde Simon Wilper Tatsuhiko Miyagawa Tomas Doran

=over 4

=item *

Karen Etheridge <ether@cpan.org>

=item *

Graham Knop <haarg@haarg.org>

=item *

Christian Walde <walde.christian@googlemail.com>

=item *

Simon Wilper <sxw@chronowerks.de>

=item *

Tatsuhiko Miyagawa <miyagawa@bulknews.net>

=item *

Tomas Doran <bobtfish@bobtfish.net>

=back

=head1 COPYRIGHT AND LICENCE

This software is copyright (c) 2008 by Florian Ragwitz.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut