B::Hooks::EndOfScope(3) User Contributed Perl Documentation B::Hooks::EndOfScope(3)

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

version 0.28

on_scope_end { ... };

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

on_scope_end { ... };
on_scope_end $code;

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

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

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

While 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 compile-time exception is instead 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
use B::Hooks::EndOfScope::PP

or by setting $ENV{B_HOOKS_ENDOFSCOPE_IMPLEMENTATION} to either "XS" or "PP".

Due to a 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 Variable::Magic is disabled on perls prior to version 5.8.4. On such systems loading/requesting B::Hooks::EndOfScope::XS explicitly will result in a compile-time exception.

Versions of perl before 5.8.0 lack a feature allowing changing the visibility of "%^H" via setting bit 17 within $^H. As such the only way to achieve the effect necessary for this module to work, is to use the "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 t/02-localise.t included with the distribution.



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

  • Florian Ragwitz <rafl@debian.org>
  • Peter Rabbitson <ribasushi@leporine.io>

  • Karen Etheridge <ether@cpan.org>
  • Graham Knop <haarg@haarg.org>
  • Christian Walde <walde.christian@googlemail.com>
  • Simon Wilper <sxw@chronowerks.de>
  • Tatsuhiko Miyagawa <miyagawa@bulknews.net>
  • Tomas Doran <bobtfish@bobtfish.net>

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.

2024-03-04 perl v5.38.2