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[perl5.git] / ext / B / B / Lint.pm
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1package B::Lint;
2
3=head1 NAME
4
5B::Lint - Perl lint
6
7=head1 SYNOPSIS
8
9perl -MO=Lint[,OPTIONS] foo.pl
10
11=head1 DESCRIPTION
12
13The B::Lint module is equivalent to an extended version of the B<-w>
14option of B<perl>. It is named after the program B<lint> which carries
15out a similar process for C programs.
16
17=head1 OPTIONS AND LINT CHECKS
18
19Option words are separated by commas (not whitespace) and follow the
20usual conventions of compiler backend options. Following any options
21(indicated by a leading B<->) come lint check arguments. Each such
22argument (apart from the special B<all> and B<none> options) is a
23word representing one possible lint check (turning on that check) or
24is B<no-foo> (turning off that check). Before processing the check
25arguments, a standard list of checks is turned on. Later options
26override earlier ones. Available options are:
27
28=over 8
29
30=item B<context>
31
32Produces a warning whenever an array is used in an implicit scalar
33context. For example, both of the lines
34
35 $foo = length(@bar);
36 $foo = @bar;
37will elicit a warning. Using an explicit B<scalar()> silences the
38warning. For example,
39
40 $foo = scalar(@bar);
41
42=item B<implicit-read> and B<implicit-write>
43
44These options produce a warning whenever an operation implicitly
45reads or (respectively) writes to one of Perl's special variables.
46For example, B<implicit-read> will warn about these:
47
48 /foo/;
49
50and B<implicit-write> will warn about these:
51
52 s/foo/bar/;
53
54Both B<implicit-read> and B<implicit-write> warn about this:
55
56 for (@a) { ... }
57
58=item B<dollar-underscore>
59
60This option warns whenever $_ is used either explicitly anywhere or
61as the implicit argument of a B<print> statement.
62
63=item B<private-names>
64
65This option warns on each use of any variable, subroutine or
66method name that lives in a non-current package but begins with
67an underscore ("_"). Warnings aren't issued for the special case
68of the single character name "_" by itself (e.g. $_ and @_).
69
70=item B<undefined-subs>
71
72This option warns whenever an undefined subroutine is invoked.
73This option will only catch explicitly invoked subroutines such
74as C<foo()> and not indirect invocations such as C<&$subref()>
75or C<$obj-E<gt>meth()>. Note that some programs or modules delay
76definition of subs until runtime by means of the AUTOLOAD
77mechanism.
78
79=item B<regexp-variables>
80
81This option warns whenever one of the regexp variables $', $& or
82$' is used. Any occurrence of any of these variables in your
83program can slow your whole program down. See L<perlre> for
84details.
85
86=item B<all>
87
88Turn all warnings on.
89
90=item B<none>
91
92Turn all warnings off.
93
94=back
95
96=head1 NON LINT-CHECK OPTIONS
97
98=over 8
99
100=item B<-u Package>
101
102Normally, Lint only checks the main code of the program together
103with all subs defined in package main. The B<-u> option lets you
104include other package names whose subs are then checked by Lint.
105
106=back
107
108=head1 BUGS
109
110This is only a very preliminary version.
111
112=head1 AUTHOR
113
114Malcolm Beattie, mbeattie@sable.ox.ac.uk.
115
116=cut
117
118use strict;
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119use B qw(walkoptree_slow main_root walksymtable svref_2object parents
120 OPf_WANT_LIST OPf_WANT OPf_STACKED G_ARRAY
121 );
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122
123my $file = "unknown"; # shadows current filename
124my $line = 0; # shadows current line number
125my $curstash = "main"; # shadows current stash
126
127# Lint checks
128my %check;
129my %implies_ok_context;
130BEGIN {
131 map($implies_ok_context{$_}++,
132 qw(pp_scalar pp_av2arylen pp_aelem pp_aslice pp_helem pp_hslice
133 pp_keys pp_values pp_hslice pp_defined pp_undef pp_delete));
134}
135
136# Lint checks turned on by default
137my @default_checks = qw(context);
138
139my %valid_check;
140# All valid checks
141BEGIN {
142 map($valid_check{$_}++,
143 qw(context implicit_read implicit_write dollar_underscore
144 private_names undefined_subs regexp_variables));
145}
146
147# Debugging options
148my ($debug_op);
149
150my %done_cv; # used to mark which subs have already been linted
151my @extra_packages; # Lint checks mainline code and all subs which are
152 # in main:: or in one of these packages.
153
154sub warning {
155 my $format = (@_ < 2) ? "%s" : shift;
156 warn sprintf("$format at %s line %d\n", @_, $file, $line);
157}
158
159# This gimme can't cope with context that's only determined
160# at runtime via dowantarray().
161sub gimme {
162 my $op = shift;
163 my $flags = $op->flags;
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164 if ($flags & OPf_WANT) {
165 return(($flags & OPf_WANT_LIST) ? 1 : 0);
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166 }
167 return undef;
168}
169
170sub B::OP::lint {}
171
172sub B::COP::lint {
173 my $op = shift;
174 if ($op->ppaddr eq "pp_nextstate") {
175 $file = $op->filegv->SV->PV;
176 $line = $op->line;
177 $curstash = $op->stash->NAME;
178 }
179}
180
181sub B::UNOP::lint {
182 my $op = shift;
183 my $ppaddr = $op->ppaddr;
184 if ($check{context} && ($ppaddr eq "pp_rv2av" || $ppaddr eq "pp_rv2hv")) {
185 my $parent = parents->[0];
186 my $pname = $parent->ppaddr;
187 return if gimme($op) || $implies_ok_context{$pname};
188 # Two special cases to deal with: "foreach (@foo)" and "delete $a{$b}"
189 # null out the parent so we have to check for a parent of pp_null and
190 # a grandparent of pp_enteriter or pp_delete
191 if ($pname eq "pp_null") {
192 my $gpname = parents->[1]->ppaddr;
193 return if $gpname eq "pp_enteriter" || $gpname eq "pp_delete";
194 }
195 warning("Implicit scalar context for %s in %s",
196 $ppaddr eq "pp_rv2av" ? "array" : "hash", $parent->desc);
197 }
198 if ($check{private_names} && $ppaddr eq "pp_method") {
199 my $methop = $op->first;
200 if ($methop->ppaddr eq "pp_const") {
201 my $method = $methop->sv->PV;
202 if ($method =~ /^_/ && !defined(&{"$curstash\::$method"})) {
203 warning("Illegal reference to private method name $method");
204 }
205 }
206 }
207}
208
209sub B::PMOP::lint {
210 my $op = shift;
211 if ($check{implicit_read}) {
212 my $ppaddr = $op->ppaddr;
213 if ($ppaddr eq "pp_match" && !($op->flags & OPf_STACKED)) {
214 warning('Implicit match on $_');
215 }
216 }
217 if ($check{implicit_write}) {
218 my $ppaddr = $op->ppaddr;
219 if ($ppaddr eq "pp_subst" && !($op->flags & OPf_STACKED)) {
220 warning('Implicit substitution on $_');
221 }
222 }
223}
224
225sub B::LOOP::lint {
226 my $op = shift;
227 if ($check{implicit_read} || $check{implicit_write}) {
228 my $ppaddr = $op->ppaddr;
229 if ($ppaddr eq "pp_enteriter") {
230 my $last = $op->last;
231 if ($last->ppaddr eq "pp_gv" && $last->gv->NAME eq "_") {
232 warning('Implicit use of $_ in foreach');
233 }
234 }
235 }
236}
237
238sub B::GVOP::lint {
239 my $op = shift;
240 if ($check{dollar_underscore} && $op->ppaddr eq "pp_gvsv"
241 && $op->gv->NAME eq "_")
242 {
243 warning('Use of $_');
244 }
245 if ($check{private_names}) {
246 my $ppaddr = $op->ppaddr;
247 my $gv = $op->gv;
248 if (($ppaddr eq "pp_gv" || $ppaddr eq "pp_gvsv")
249 && $gv->NAME =~ /^_./ && $gv->STASH->NAME ne $curstash)
250 {
251 warning('Illegal reference to private name %s', $gv->NAME);
252 }
253 }
254 if ($check{undefined_subs}) {
255 if ($op->ppaddr eq "pp_gv" && $op->next->ppaddr eq "pp_entersub") {
256 my $gv = $op->gv;
257 my $subname = $gv->STASH->NAME . "::" . $gv->NAME;
258 no strict 'refs';
259 if (!defined(&$subname)) {
260 $subname =~ s/^main:://;
261 warning('Undefined subroutine %s called', $subname);
262 }
263 }
264 }
265 if ($check{regexp_variables} && $op->ppaddr eq "pp_gvsv") {
266 my $name = $op->gv->NAME;
267 if ($name =~ /^[&'`]$/) {
268 warning('Use of regexp variable $%s', $name);
269 }
270 }
271}
272
273sub B::GV::lintcv {
274 my $gv = shift;
275 my $cv = $gv->CV;
276 #warn sprintf("lintcv: %s::%s (done=%d)\n",
277 # $gv->STASH->NAME, $gv->NAME, $done_cv{$$cv});#debug
278 return if !$$cv || $done_cv{$$cv}++;
279 my $root = $cv->ROOT;
280 #warn " root = $root (0x$$root)\n";#debug
281 walkoptree_slow($root, "lint") if $$root;
282}
283
284sub do_lint {
285 my %search_pack;
286 walkoptree_slow(main_root, "lint") if ${main_root()};
287
288 # Now do subs in main
289 no strict qw(vars refs);
290 my $sym;
291 local(*glob);
292 while (($sym, *glob) = each %{"main::"}) {
293 #warn "Trying $sym\n";#debug
294 svref_2object(\*glob)->EGV->lintcv unless $sym =~ /::$/;
295 }
296
297 # Now do subs in non-main packages given by -u options
298 map { $search_pack{$_} = 1 } @extra_packages;
299 walksymtable(\%{"main::"}, "lintcv", sub {
300 my $package = shift;
301 $package =~ s/::$//;
302 #warn "Considering $package\n";#debug
303 return exists $search_pack{$package};
304 });
305}
306
307sub compile {
308 my @options = @_;
309 my ($option, $opt, $arg);
310 # Turn on default lint checks
311 for $opt (@default_checks) {
312 $check{$opt} = 1;
313 }
314 OPTION:
315 while ($option = shift @options) {
316 if ($option =~ /^-(.)(.*)/) {
317 $opt = $1;
318 $arg = $2;
319 } else {
320 unshift @options, $option;
321 last OPTION;
322 }
323 if ($opt eq "-" && $arg eq "-") {
324 shift @options;
325 last OPTION;
326 } elsif ($opt eq "D") {
327 $arg ||= shift @options;
328 foreach $arg (split(//, $arg)) {
329 if ($arg eq "o") {
330 B->debug(1);
331 } elsif ($arg eq "O") {
332 $debug_op = 1;
333 }
334 }
335 } elsif ($opt eq "u") {
336 $arg ||= shift @options;
337 push(@extra_packages, $arg);
338 }
339 }
340 foreach $opt (@default_checks, @options) {
341 $opt =~ tr/-/_/;
342 if ($opt eq "all") {
343 %check = %valid_check;
344 }
345 elsif ($opt eq "none") {
346 %check = ();
347 }
348 else {
349 if ($opt =~ s/^no-//) {
350 $check{$opt} = 0;
351 }
352 else {
353 $check{$opt} = 1;
354 }
355 warn "No such check: $opt\n" unless defined $valid_check{$opt};
356 }
357 }
358 # Remaining arguments are things to check
359
360 return \&do_lint;
361}
362
3631;