3 our $VERSION = '1.09'; ## no critic
11 perl -MO=Lint[,OPTIONS] foo.pl
15 The B::Lint module is equivalent to an extended version of the B<-w>
16 option of B<perl>. It is named after the program F<lint> which carries
17 out a similar process for C programs.
19 =head1 OPTIONS AND LINT CHECKS
21 Option words are separated by commas (not whitespace) and follow the
22 usual conventions of compiler backend options. Following any options
23 (indicated by a leading B<->) come lint check arguments. Each such
24 argument (apart from the special B<all> and B<none> options) is a
25 word representing one possible lint check (turning on that check) or
26 is B<no-foo> (turning off that check). Before processing the check
27 arguments, a standard list of checks is turned on. Later options
28 override earlier ones. Available options are:
32 =item B<magic-diamond>
34 Produces a warning whenever the magic C<E<lt>E<gt>> readline is
35 used. Internally it uses perl's two-argument open which itself treats
36 filenames with special characters specially. This could allow
37 interestingly named files to have unexpected effects when reading.
42 The above creates a file named C<rm *|>. When perl opens it with
43 C<E<lt>E<gt>> it actually executes the shell program C<rm *>. This
44 makes C<E<lt>E<gt>> dangerous to use carelessly.
48 Produces a warning whenever an array is used in an implicit scalar
49 context. For example, both of the lines
54 will elicit a warning. Using an explicit B<scalar()> silences the
59 =item B<implicit-read> and B<implicit-write>
61 These options produce a warning whenever an operation implicitly
62 reads or (respectively) writes to one of Perl's special variables.
63 For example, B<implicit-read> will warn about these:
67 and B<implicit-write> will warn about these:
71 Both B<implicit-read> and B<implicit-write> warn about this:
77 This option warns whenever a bareword is implicitly quoted, but is also
78 the name of a subroutine in the current package. Typical mistakes that it will
81 use constant foo => 'bar';
85 Neither of these will do what a naive user would expect.
87 =item B<dollar-underscore>
89 This option warns whenever C<$_> is used either explicitly anywhere or
90 as the implicit argument of a B<print> statement.
92 =item B<private-names>
94 This option warns on each use of any variable, subroutine or
95 method name that lives in a non-current package but begins with
96 an underscore ("_"). Warnings aren't issued for the special case
97 of the single character name "_" by itself (e.g. C<$_> and C<@_>).
99 =item B<undefined-subs>
101 This option warns whenever an undefined subroutine is invoked.
102 This option will only catch explicitly invoked subroutines such
103 as C<foo()> and not indirect invocations such as C<&$subref()>
104 or C<$obj-E<gt>meth()>. Note that some programs or modules delay
105 definition of subs until runtime by means of the AUTOLOAD
108 =item B<regexp-variables>
110 This option warns whenever one of the regexp variables C<$`>, C<$&> or C<$'>
111 is used. Any occurrence of any of these variables in your
112 program can slow your whole program down. See L<perlre> for
117 Turn all warnings on.
121 Turn all warnings off.
125 =head1 NON LINT-CHECK OPTIONS
131 Normally, Lint only checks the main code of the program together
132 with all subs defined in package main. The B<-u> option lets you
133 include other package names whose subs are then checked by Lint.
137 =head1 EXTENDING LINT
139 Lint can be extended by with plugins. Lint uses L<Module::Pluggable>
140 to find available plugins. Plugins are expected but not required to
141 inform Lint of which checks they are adding.
143 The C<< B::Lint->register_plugin( MyPlugin => \@new_checks ) >> method
144 adds the list of C<@new_checks> to the list of valid checks. If your
145 module wasn't loaded by L<Module::Pluggable> then your class name is
146 added to the list of plugins.
148 You must create a C<match( \%checks )> method in your plugin class or one
149 of its parents. It will be called on every op as a regular method call
150 with a hash ref of checks as its parameter.
152 The class methods C<< B::Lint->file >> and C<< B::Lint->line >> contain
153 the current filename and line number.
157 B::Lint->register_plugin( Sample => [ 'good_taste' ] );
160 my ( $op, $checks_href ) = shift @_;
161 if ( $checks_href->{good_taste} ) {
170 =item while(<FH>) stomps $_
174 =item unchecked system calls
176 =item more tests, validate against older perls
182 This is only a very preliminary version.
186 Malcolm Beattie, mbeattie@sable.ox.ac.uk.
191 use B qw( walkoptree_slow
192 main_root main_cv walksymtable parents
194 OPf_WANT_VOID OPf_WANT_LIST OPf_WANT OPf_STACKED SVf_POK );
197 # The current M::P doesn't know about .pmc files.
198 use Module::Pluggable ( require => 1 );
200 use List::Util 'first';
201 ## no critic Prototypes
202 sub any (&@) { my $test = shift @_; $test->() and return 1 for @_; return 0 }
206 # Import or create some constants from B. B doesn't provide
207 # everything I need so some things like OPpCONST_BARE are defined
209 for my $sym ( qw( begin_av check_av init_av end_av ),
210 [ 'OPpCONST_BARE' => 64 ] )
213 ( $sym, $val ) = @$sym if ref $sym;
215 if ( any { $sym eq $_ } @B::EXPORT_OK, @B::EXPORT ) {
220 constant->import( $sym => $val );
225 my $file = "unknown"; # shadows current filename
226 my $line = 0; # shadows current line number
227 my $curstash = "main"; # shadows current stash
228 my $curcv; # shadows current B::CV for pad lookups
232 sub curstash {$curstash}
237 my %implies_ok_context;
239 map( $implies_ok_context{$_}++,
240 qw(scalar av2arylen aelem aslice helem hslice
241 keys values hslice defined undef delete) );
243 # Lint checks turned on by default
245 = qw(context magic_diamond undefined_subs regexp_variables);
251 qw(context implicit_read implicit_write dollar_underscore
252 private_names bare_subs undefined_subs regexp_variables
256 $valid_check{$check} = __PACKAGE__;
262 my %done_cv; # used to mark which subs have already been linted
263 my @extra_packages; # Lint checks mainline code and all subs which are
264 # in main:: or in one of these packages.
267 my $format = ( @_ < 2 ) ? "%s" : shift @_;
268 warn sprintf( "$format at %s line %d\n", @_, $file, $line );
269 return undef; ## no critic undef
272 # This gimme can't cope with context that's only determined
273 # at runtime via dowantarray().
276 my $flags = $op->flags;
277 if ( $flags & OPf_WANT ) {
278 return ( ( $flags & OPf_WANT ) == OPf_WANT_LIST ? 1 : 0 );
280 return undef; ## no critic undef
283 my @plugins = __PACKAGE__->plugins;
287 # A boolean function to be used while inside a B::walkoptree_slow
288 # call. If we are in the EXPR part of C<grep EXPR, ...> or C<grep
289 # { EXPR } ...>, this returns true.
290 return any { $_->name =~ m/\A(?:grep|map)/xms } @{ parents() };
293 sub inside_foreach_modifier {
297 # A boolean function to be used while inside a B::walkoptree_slow
298 # call. If we are in the EXPR part of C<EXPR foreach ...> this
300 for my $ancestor ( @{ parents() } ) {
301 next unless $ancestor->name eq 'leaveloop';
303 my $first = $ancestor->first;
304 next unless $first->name eq 'enteriter';
306 next if $first->redoop->name =~ m/\A(?:next|db|set)state\z/xms;
314 [qw[ B::PADOP::gv_harder gv padix]],
315 [qw[ B::SVOP::sv_harder sv targ]],
316 [qw[ B::SVOP::gv_harder gv padix]]
320 # I'm generating some functions here because they're mostly
321 # similar. It's all for compatibility with threaded
322 # perl. Perhaps... this code should inspect $Config{usethreads}
323 # and generate a *specific* function. I'm leaving it generic for
326 # In threaded perl SVs and GVs aren't used directly in the optrees
327 # like they are in non-threaded perls. The ops that would use a SV
328 # or GV keep an index into the subroutine's scratchpad. I'm
329 # currently ignoring $cv->DEPTH and that might be at my peril.
331 my ( $subname, $attr, $pad_attr ) = @$_;
332 my $target = do { ## no critic strict
340 if ( not $op->isa('B::PADOP') ) {
343 return $elt if eval { $elt->isa('B::SV') };
345 my $ix = $op->$pad_attr;
346 my @entire_pad = $curcv->PADLIST->ARRAY;
347 my @elts = map +( $_->ARRAY )[$ix], @entire_pad;
349 eval { $_->isa('B::SV') } ? $_ : ();
351 @elts[ 0, reverse 1 .. $#elts ];
359 # This is a fallback ->lint for all the ops where I haven't
360 # defined something more specific. Nothing happens here.
362 # Call all registered plugins
364 $m = $_->can('match'), $op->$m( \%check ) for @plugins;
371 # nextstate ops sit between statements. Whenever I see one I
372 # update the current info on file, line, and stash. This code also
373 # updates it when it sees a dbstate or setstate op. I have no idea
374 # what those are but having seen them mentioned together in other
375 # parts of the perl I think they're kind of equivalent.
376 if ( $op->name =~ m/\A(?:next|db|set)state\z/ ) {
379 $curstash = $op->stash->NAME;
382 # Call all registered plugins
384 $m = $_->can('match'), $op->$m( \%check ) for @plugins;
391 my $opname = $op->name;
395 # Check arrays and hashes in scalar or void context where
396 # scalar() hasn't been used.
399 unless $check{context}
400 and $opname =~ m/\Arv2[ah]v\z/xms
403 my ( $parent, $gparent ) = @{ parents() }[ 0, 1 ];
404 my $pname = $parent->name;
406 next if $implies_ok_context{$pname};
408 # Three special cases to deal with: "foreach (@foo)", "delete
409 # $a{$b}", and "exists $a{$b}" null out the parent so we have to
410 # check for a parent of pp_null and a grandparent of
411 # pp_enteriter, pp_delete, pp_exists
415 and $gparent->name =~ m/\A(?:delete|enteriter|exists)\z/xms;
417 # our( @bar ); would also trigger this error so I exclude
420 if $op->private & OPpOUR_INTRO
421 and ( $op->flags & OPf_WANT ) == OPf_WANT_VOID;
423 warning 'Implicit scalar context for %s in %s',
424 $opname eq "rv2av" ? "array" : "hash", $parent->desc;
429 # Looks for calls to methods with names that begin with _ and
430 # that aren't visible within the current package. Maybe this
431 # should look at @ISA.
433 unless $check{private_names}
434 and $opname =~ m/\Amethod/xms;
436 my $methop = $op->first;
437 next unless $methop->name eq "const";
439 my $method = $methop->sv_harder->PV;
441 unless $method =~ m/\A_/xms
442 and not defined &{"$curstash\::$method"};
444 warning q[Illegal reference to private method name '%s'], $method;
447 # Call all registered plugins
449 $m = $_->can('match'), $op->$m( \%check ) for @plugins;
458 # Look for /.../ that doesn't use =~ to bind to something.
460 unless $check{implicit_read}
461 and $op->name eq "match"
462 and not( $op->flags & OPf_STACKED
463 or inside_grepmap() );
464 warning 'Implicit match on $_';
469 # Look for s/.../.../ that doesn't use =~ to bind to
472 unless $check{implicit_write}
473 and $op->name eq "subst"
474 and not $op->flags & OPf_STACKED;
475 warning 'Implicit substitution on $_';
478 # Call all registered plugins
480 $m = $_->can('match'), $op->$m( \%check ) for @plugins;
489 # Look for C<for ( ... )>.
491 unless ( $check{implicit_read} or $check{implicit_write} )
492 and $op->name eq "enteriter";
494 my $last = $op->last;
496 unless $last->name eq "gv"
497 and $last->gv_harder->NAME eq "_"
498 and $op->redoop->name =~ m/\A(?:next|db|set)state\z/xms;
500 warning 'Implicit use of $_ in foreach';
503 # Call all registered plugins
505 $m = $_->can('match'), $op->$m( \%check ) for @plugins;
509 # In threaded vs non-threaded perls you'll find that threaded perls
510 # use PADOP in place of SVOPs so they can do lookups into the
511 # scratchpad to find things. I suppose this is so a optree can be
512 # shared between threads and all symbol table muckery will just get
513 # written to a scratchpad.
514 *B::PADOP::lint = \&B::SVOP::lint;
521 unless $check{magic_diamond}
522 and parents()->[0]->name eq 'readline'
523 and $op->gv_harder->NAME eq 'ARGV';
530 unless $check{bare_subs}
531 and $op->name eq 'const'
532 and $op->private & OPpCONST_BARE;
534 my $sv = $op->sv_harder;
535 next unless $sv->FLAGS & SVf_POK;
538 my $subname = "$curstash\::$sub";
540 # I want to skip over things that were declared with the
541 # constant pragma. Well... sometimes. Hmm. I want to ignore
542 # C<<use constant FOO => ...>> but warn on C<<FOO => ...>>
543 # later. The former is typical declaration syntax and the
544 # latter would be an error.
546 # Skipping over both could be handled by looking if
547 # $constant::declared{$subname} is true.
549 # Check that it's a function.
551 unless exists &{"$curstash\::$sub"};
553 warning q[Bare sub name '%s' interpreted as string], $sub;
557 next unless $check{private_names};
559 my $opname = $op->name;
560 if ( $opname =~ m/\Agv(?:sv)?\z/xms ) {
562 # Looks for uses of variables and stuff that are named
563 # private and we're not in the same package.
564 my $gv = $op->gv_harder;
565 my $name = $gv->NAME;
567 unless $name =~ m/\A_./xms
568 and $gv->STASH->NAME ne $curstash;
570 warning q[Illegal reference to private name '%s'], $name;
572 elsif ( $opname eq "method_named" ) {
573 my $method = $op->sv_harder->PV;
574 next unless $method =~ m/\A_./xms;
576 warning q[Illegal reference to private method name '%s'], $method;
582 # Warn on uses of $_ with a few exceptions. I'm not warning on
583 # $_ inside grep, map, or statement modifer foreach because
584 # they localize $_ and it'd be impossible to use these
585 # features without getting warnings.
588 unless $check{dollar_underscore}
589 and $op->name eq "gvsv"
590 and $op->gv_harder->NAME eq "_"
591 and not( inside_grepmap
592 or inside_foreach_modifier );
599 # Look for any uses of $`, $&, or $'.
601 unless $check{regexp_variables}
602 and $op->name eq "gvsv";
604 my $name = $op->gv_harder->NAME;
605 next unless $name =~ m/\A[\&\'\`]\z/xms;
607 warning 'Use of regexp variable $%s', $name;
612 # Look for calls to functions that either don't exist or don't
615 unless $check{undefined_subs}
616 and $op->name eq "gv"
617 and $op->next->name eq "entersub";
619 my $gv = $op->gv_harder;
620 my $subname = $gv->STASH->NAME . "::" . $gv->NAME;
622 no strict 'refs'; ## no critic strict
623 if ( not exists &$subname ) {
624 $subname =~ s/\Amain:://;
625 warning q[Nonexistant subroutine '%s' called], $subname;
627 elsif ( not defined &$subname ) {
628 $subname =~ s/\A\&?main:://;
629 warning q[Undefined subroutine '%s' called], $subname;
633 # Call all registered plugins
635 $m = $_->can('match'), $op->$m( \%check ) for @plugins;
641 # Example: B::svref_2object( \ *A::Glob )->lintcv
645 return unless $cv->can('lintcv');
652 # Example: B::svref_2object( \ &foo )->lintcv
654 # Write to the *global* $
657 #warn sprintf("lintcv: %s::%s (done=%d)\n",
658 # $gv->STASH->NAME, $gv->NAME, $done_cv{$$curcv});#debug
659 return unless ref($curcv) and $$curcv and not $done_cv{$$curcv}++;
660 my $root = $curcv->ROOT;
662 #warn " root = $root (0x$$root)\n";#debug
663 walkoptree_slow( $root, "lint" ) if $$root;
670 # Copy to the global $curcv for use in pad lookups.
672 walkoptree_slow( main_root, "lint" ) if ${ main_root() };
674 # Do all the miscellaneous non-sub blocks.
675 for my $av ( begin_av, init_av, check_av, end_av ) {
676 next unless eval { $av->isa('B::AV') };
677 for my $cv ( $av->ARRAY ) {
678 next unless ref($cv) and $cv->FILE eq $0;
686 if ( $_[0]->FILE eq $0 ) { $_[0]->lintcv }
696 # Turn on default lint checks
697 for my $opt (@default_checks) {
702 while ( my $option = shift @options ) {
704 unless ( ( $opt, $arg ) = $option =~ m/\A-(.)(.*)/xms ) {
705 unshift @options, $option;
709 if ( $opt eq "-" && $arg eq "-" ) {
713 elsif ( $opt eq "D" ) {
714 $arg ||= shift @options;
715 foreach my $arg ( split //, $arg ) {
719 elsif ( $arg eq "O" ) {
724 elsif ( $opt eq "u" ) {
725 $arg ||= shift @options;
726 push @extra_packages, $arg;
730 foreach my $opt ( @default_checks, @options ) {
732 if ( $opt eq "all" ) {
733 %check = %valid_check;
735 elsif ( $opt eq "none" ) {
739 if ( $opt =~ s/\Ano_//xms ) {
745 carp "No such check: $opt"
746 unless defined $valid_check{$opt};
750 # Remaining arguments are things to check. So why aren't I
751 # capturing them or something? I don't know.
756 sub register_plugin {
757 my ( undef, $plugin, $new_checks ) = @_;
759 # Allow the user to be lazy and not give us a name.
760 $plugin = caller unless defined $plugin;
762 # Register the plugin's named checks, if any.
763 for my $check ( eval {@$new_checks} ) {
764 if ( not defined $check ) {
765 carp 'Undefined value in checks.';
768 if ( exists $valid_check{$check} ) {
770 "$check is already registered as a $valid_check{$check} feature.";
774 $valid_check{$check} = $plugin;
777 # Register a non-Module::Pluggable loaded module. @plugins already
778 # contains whatever M::P found on disk. The user might load a
779 # plugin manually from some arbitrary namespace and ask for it to
781 if ( not any { $_ eq $plugin } @plugins ) {
782 push @plugins, $plugin;