Perl::Critic::Policy::Modules::ProhibitPOSIXimport - don't import the whole of POSIX into a module
This policy is part of the
It asks you not to
use POSIX with an import of all the symbols from that module if you're only using a few things.
package Foo; use POSIX; # bad
The aim is to save some memory, and maybe run a bit faster. A full
POSIX import adds about 550 symbols to your module and that's about 30 to 40 kbytes in Perl 5.10 on a 32-bit system, or about 115 kbytes in Perl 5.8. If lots of modules do this then it adds up.
As noted in the
POSIX module docs, the way it exports everything by default is an historical accident, not something to encourage.
A full import is allowed in
package main, which is the top-level of a script etc, since in a script you want convenience rather than a bit of memory, at least initially.
#!/usr/bin/perl use POSIX; # ok
An import of no symbols is allowed and you then add a
POSIX:: qualifier to each call or constant. Qualifiers like this can make it clear where the function is coming from.
package Foo; use POSIX (); # ok my $fd = POSIX::dup(0); if ($! == POSIX::ENOENT())
An import of an explicit set of functions and constants is allowed. This allows short names without the memory penalty of a full import. However it can be error-prone to update the imports with what you actually use (see
ProhibitCallsToUndeclaredSubs for some checking).
package Foo; use POSIX qw(dup ENOENT); # ok ... my $fd = dup(0);
A full import is allowed in a module if there's 15 or more calls to
POSIX module functions. This rule might change or be configurable in the future, but the intention is that a module making heavy use of
POSIX shouldn't be burdened by a
POSIX:: on every call or by maintaining a list of explicit imports.
package Foo; use POSIX; # ok ... tzset(); dup(1)... # 15 or more calls to POSIX stuff
If you don't care this sort of thing you can always disable
ProhibitPOSIXimport from your .perlcriticrc in the usual way (see "CONFIGURATION" in Perl::Critic),
Copyright 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Kevin Ryde
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