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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 twoargument
               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 noncurrent
               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, mbeattie@sable.ox.ac.uk.

ACKNOWLEDGEMENTS
       Sebastien Aperghis-Tramoni - bug fixes



perl v5.12.5                                     2012-11-03                                     B::Lint(3pm)