B::Hooks::EndOfScope(3pm) - phpMan

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

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

VERSION
version 0.25

SYNOPSIS
on_scope_end { ... };

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

FUNCTIONS
on_scope_end
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.

LIMITATIONS
Pure-perl mode caveat
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
or
use B::Hooks::EndOfScope::PP

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

Perl 5.8.0 ~ 5.8.3
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.

Perl versions 5.6.x
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.