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 B<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:
34 Produces a warning whenever an array is used in an implicit scalar
35 context. For example, both of the lines
39 will elicit a warning. Using an explicit B<scalar()> silences the
44 =item B<implicit-read> and B<implicit-write>
46 These options produce a warning whenever an operation implicitly
47 reads or (respectively) writes to one of Perl's special variables.
48 For example, B<implicit-read> will warn about these:
52 and B<implicit-write> will warn about these:
56 Both B<implicit-read> and B<implicit-write> warn about this:
60 =item B<dollar-underscore>
62 This option warns whenever $_ is used either explicitly anywhere or
63 as the implicit argument of a B<print> statement.
65 =item B<private-names>
67 This option warns on each use of any variable, subroutine or
68 method name that lives in a non-current package but begins with
69 an underscore ("_"). Warnings aren't issued for the special case
70 of the single character name "_" by itself (e.g. $_ and @_).
72 =item B<undefined-subs>
74 This option warns whenever an undefined subroutine is invoked.
75 This option will only catch explicitly invoked subroutines such
76 as C<foo()> and not indirect invocations such as C<&$subref()>
77 or C<$obj-E<gt>meth()>. Note that some programs or modules delay
78 definition of subs until runtime by means of the AUTOLOAD
81 =item B<regexp-variables>
83 This option warns whenever one of the regexp variables $', $& or
84 $' is used. Any occurrence of any of these variables in your
85 program can slow your whole program down. See L<perlre> for
94 Turn all warnings off.
98 =head1 NON LINT-CHECK OPTIONS
104 Normally, Lint only checks the main code of the program together
105 with all subs defined in package main. The B<-u> option lets you
106 include other package names whose subs are then checked by Lint.
112 This is only a very preliminary version.
114 This module doesn't work correctly on thread-enabled perls.
118 Malcolm Beattie, mbeattie@sable.ox.ac.uk.
123 use B qw(walkoptree_slow main_root walksymtable svref_2object parents
124 OPf_WANT_LIST OPf_WANT OPf_STACKED G_ARRAY
127 my $file = "unknown"; # shadows current filename
128 my $line = 0; # shadows current line number
129 my $curstash = "main"; # shadows current stash
133 my %implies_ok_context;
135 map($implies_ok_context{$_}++,
136 qw(scalar av2arylen aelem aslice helem hslice
137 keys values hslice defined undef delete));
140 # Lint checks turned on by default
141 my @default_checks = qw(context);
146 map($valid_check{$_}++,
147 qw(context implicit_read implicit_write dollar_underscore
148 private_names undefined_subs regexp_variables));
154 my %done_cv; # used to mark which subs have already been linted
155 my @extra_packages; # Lint checks mainline code and all subs which are
156 # in main:: or in one of these packages.
159 my $format = (@_ < 2) ? "%s" : shift;
160 warn sprintf("$format at %s line %d\n", @_, $file, $line);
163 # This gimme can't cope with context that's only determined
164 # at runtime via dowantarray().
167 my $flags = $op->flags;
168 if ($flags & OPf_WANT) {
169 return(($flags & OPf_WANT) == OPf_WANT_LIST ? 1 : 0);
178 if ($op->name eq "nextstate") {
181 $curstash = $op->stash->NAME;
187 my $opname = $op->name;
188 if ($check{context} && ($opname eq "rv2av" || $opname eq "rv2hv")) {
189 my $parent = parents->[0];
190 my $pname = $parent->name;
191 return if gimme($op) || $implies_ok_context{$pname};
192 # Two special cases to deal with: "foreach (@foo)" and "delete $a{$b}"
193 # null out the parent so we have to check for a parent of pp_null and
194 # a grandparent of pp_enteriter or pp_delete
195 if ($pname eq "null") {
196 my $gpname = parents->[1]->name;
197 return if $gpname eq "enteriter" || $gpname eq "delete";
199 warning("Implicit scalar context for %s in %s",
200 $opname eq "rv2av" ? "array" : "hash", $parent->desc);
202 if ($check{private_names} && $opname eq "method") {
203 my $methop = $op->first;
204 if ($methop->name eq "const") {
205 my $method = $methop->sv->PV;
206 if ($method =~ /^_/ && !defined(&{"$curstash\::$method"})) {
207 warning("Illegal reference to private method name $method");
215 if ($check{implicit_read}) {
216 if ($op->name eq "match" && !($op->flags & OPf_STACKED)) {
217 warning('Implicit match on $_');
220 if ($check{implicit_write}) {
221 if ($op->name eq "subst" && !($op->flags & OPf_STACKED)) {
222 warning('Implicit substitution on $_');
229 if ($check{implicit_read} || $check{implicit_write}) {
230 if ($op->name eq "enteriter") {
231 my $last = $op->last;
232 if ($last->name eq "gv" && $last->gv->NAME eq "_") {
233 warning('Implicit use of $_ in foreach');
241 if ($check{dollar_underscore} && $op->name eq "gvsv"
242 && $op->gv->NAME eq "_")
244 warning('Use of $_');
246 if ($check{private_names}) {
247 my $opname = $op->name;
248 if ($opname eq "gv" || $opname eq "gvsv") {
250 if ($gv->NAME =~ /^_./ && $gv->STASH->NAME ne $curstash) {
251 warning('Illegal reference to private name %s', $gv->NAME);
255 if ($check{undefined_subs}) {
256 if ($op->name eq "gv"
257 && $op->next->name eq "entersub")
260 my $subname = $gv->STASH->NAME . "::" . $gv->NAME;
262 if (!defined(&$subname)) {
263 $subname =~ s/^main:://;
264 warning('Undefined subroutine %s called', $subname);
268 if ($check{regexp_variables} && $op->name eq "gvsv") {
269 my $name = $op->gv->NAME;
270 if ($name =~ /^[&'`]$/) {
271 warning('Use of regexp variable $%s', $name);
279 #warn sprintf("lintcv: %s::%s (done=%d)\n",
280 # $gv->STASH->NAME, $gv->NAME, $done_cv{$$cv});#debug
281 return if !$$cv || $done_cv{$$cv}++;
282 my $root = $cv->ROOT;
283 #warn " root = $root (0x$$root)\n";#debug
284 walkoptree_slow($root, "lint") if $$root;
289 walkoptree_slow(main_root, "lint") if ${main_root()};
291 # Now do subs in main
292 no strict qw(vars refs);
294 for my $sym (keys %main::) {
295 next if $sym =~ /::$/;
296 *glob = $main::{$sym};
297 svref_2object(\*glob)->EGV->lintcv;
300 # Now do subs in non-main packages given by -u options
301 map { $search_pack{$_} = 1 } @extra_packages;
302 walksymtable(\%{"main::"}, "lintcv", sub {
305 #warn "Considering $package\n";#debug
306 return exists $search_pack{$package};
312 my ($option, $opt, $arg);
313 # Turn on default lint checks
314 for $opt (@default_checks) {
318 while ($option = shift @options) {
319 if ($option =~ /^-(.)(.*)/) {
323 unshift @options, $option;
326 if ($opt eq "-" && $arg eq "-") {
329 } elsif ($opt eq "D") {
330 $arg ||= shift @options;
331 foreach $arg (split(//, $arg)) {
334 } elsif ($arg eq "O") {
338 } elsif ($opt eq "u") {
339 $arg ||= shift @options;
340 push(@extra_packages, $arg);
343 foreach $opt (@default_checks, @options) {
346 %check = %valid_check;
348 elsif ($opt eq "none") {
352 if ($opt =~ s/^no_//) {
358 warn "No such check: $opt\n" unless defined $valid_check{$opt};
361 # Remaining arguments are things to check