How can I smoke out undefined subroutines?

Question

I want to scan a code base to identify all instances of undefined subroutines that are not presently reachable.

As an example:

use strict;
use warnin         


        

Answer 1

To find calls to subs that aren't defined at compile time, you can use B::Lint as follows:

a.pl:

use List::Util qw( min );

sub defined_sub { }
sub defined_later;
sub undefined_sub;

defined_sub();
defined_later();
undefined_sub();
undeclared_sub();
min();
max();              # XXX Didn't import
List::Util::max();
List::Util::mac();  # XXX Typo!

sub defined_later { }

Test:

$ perl -MO=Lint,undefined-subs a.pl
Undefined subroutine 'undefined_sub' called at a.pl line 9
Nonexistent subroutine 'undeclared_sub' called at a.pl line 10
Nonexistent subroutine 'max' called at a.pl line 12
Nonexistent subroutine 'List::Util::mac' called at a.pl line 14
a.pl syntax OK

Note that this is just for sub calls. Method calls (such as Class->method and method Class) aren't checked. But you are asking about sub calls.

Note that foo $x is a valid method call (using the indirect method call syntax) meaning $x->foo if foo isn't a valid function or sub, so B::Lint won't catch that. But it will catch foo($x).