Componentpedia / Listings / B::Hooks::EndOfScope

=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 LSub::Exporter on how to customize it.

=head1 LIMITATIONS

=head2 Pure-perl mode caveat

This caveat applies to B version of perl where LVariable::Magic is unavailable or otherwise disabled.

While LVariable::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 is instead B, 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 or C.

=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 LVariable::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 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

LSub::Exporter

LVariable::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.

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