B::Lint(3pm)                                    Perl Programmers Reference Guide                                    B::Lint(3pm)



NAME
       B::Lint - Perl lint

SYNOPSIS
       perl -MO=Lint[,OPTIONS] foo.pl

DESCRIPTION
       The B::Lint module is equivalent to an extended version of the -w option of perl. It is named after the program lint
       which carries out a similar process for C programs.

OPTIONS AND LINT CHECKS
       Option words are separated by commas (not whitespace) and follow the usual conventions of compiler backend options.
       Following any options (indicated by a leading -) come lint check arguments. Each such argument (apart from the special
       all and none options) is a word representing one possible lint check (turning on that check) or is no-foo (turning off
       that check). Before processing the check arguments, a standard list of checks is turned on. Later options override
       earlier ones. Available options are:

       magic-diamond
               Produces a warning whenever the magic "<>" readline is used. Internally it uses perl's two-argument open which
               itself treats filenames with special characters specially. This could allow interestingly named files to have
               unexpected effects when reading.

                 % touch 'rm *|'
                 % perl -pe 1

               The above creates a file named "rm *|". When perl opens it with "<>" it actually executes the shell program "rm
               *". This makes "<>" dangerous to use carelessly.

       context Produces a warning whenever an array is used in an implicit scalar context. For example, both of the lines

                   $foo = length(@bar);
                   $foo = @bar;

               will elicit a warning. Using an explicit scalar() silences the warning. For example,

                   $foo = scalar(@bar);

       implicit-read and implicit-write
               These options produce a warning whenever an operation implicitly reads or (respectively) writes to one of Perl's
               special variables.  For example, implicit-read will warn about these:

                   /foo/;

               and implicit-write will warn about these:

                   s/foo/bar/;

               Both implicit-read and implicit-write warn about this:

                   for (@a) { ... }

       bare-subs
               This option warns whenever a bareword is implicitly quoted, but is also the name of a subroutine in the current
               package. Typical mistakes that it will trap are:

                   use constant foo => 'bar';
                   @a = ( foo => 1 );
                   $b{foo} = 2;

               Neither of these will do what a naive user would expect.

       dollar-underscore
               This option warns whenever $_ is used either explicitly anywhere or as the implicit argument of a print
               statement.

       private-names
               This option warns on each use of any variable, subroutine or method name that lives in a non-current package but
               begins with an underscore ("_"). Warnings aren't issued for the special case of the single character name "_" by
               itself (e.g. $_ and @_).

       undefined-subs
               This option warns whenever an undefined subroutine is invoked.  This option will only catch explicitly invoked
               subroutines such as "foo()" and not indirect invocations such as "&$subref()" or "$obj->meth()". Note that some
               programs or modules delay definition of subs until runtime by means of the AUTOLOAD mechanism.

       regexp-variables
               This option warns whenever one of the regexp variables "$`", $& or "$'" is used. Any occurrence of any of these
               variables in your program can slow your whole program down. See perlre for details.

       all     Turn all warnings on.

       none    Turn all warnings off.

NON LINT-CHECK OPTIONS
       -u Package
               Normally, Lint only checks the main code of the program together with all subs defined in package main. The -u
               option lets you include other package names whose subs are then checked by Lint.

EXTENDING LINT
       Lint can be extended by with plugins. Lint uses Module::Pluggable to find available plugins. Plugins are expected but not
       required to inform Lint of which checks they are adding.

       The "B::Lint->register_plugin( MyPlugin => \@new_checks )" method adds the list of @new_checks to the list of valid
       checks. If your module wasn't loaded by Module::Pluggable then your class name is added to the list of plugins.

       You must create a "match( \%checks )" method in your plugin class or one of its parents. It will be called on every op as
       a regular method call with a hash ref of checks as its parameter.

       The class methods "B::Lint->file" and "B::Lint->line" contain the current filename and line number.

         package Sample;
         use B::Lint;
         B::Lint->register_plugin( Sample => [ 'good_taste' ] );

         sub match {
             my ( $op, $checks_href ) = shift @_;
             if ( $checks_href->{good_taste} ) {
                 ...
             }
         }

TODO
       while(<FH>) stomps $_
       strict oo
       unchecked system calls
       more tests, validate against older perls

BUGS
       This is only a very preliminary version.

AUTHOR
       Malcolm Beattie, mbeattieATsable.uk.

ACKNOWLEDGEMENTS
       Sebastien Aperghis-Tramoni - bug fixes



perl v5.12.4                                               2011-06-20                                               B::Lint(3pm)