368 lines
9.1 KiB
Perl
368 lines
9.1 KiB
Perl
package B::Lint;
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=head1 NAME
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B::Lint - Perl lint
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=head1 SYNOPSIS
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perl -MO=Lint[,OPTIONS] foo.pl
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=head1 DESCRIPTION
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The B::Lint module is equivalent to an extended version of the B<-w>
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option of B<perl>. It is named after the program B<lint> which carries
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out a similar process for C programs.
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=head1 OPTIONS AND LINT CHECKS
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Option words are separated by commas (not whitespace) and follow the
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usual conventions of compiler backend options. Following any options
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(indicated by a leading B<->) come lint check arguments. Each such
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argument (apart from the special B<all> and B<none> options) is a
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word representing one possible lint check (turning on that check) or
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is B<no-foo> (turning off that check). Before processing the check
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arguments, a standard list of checks is turned on. Later options
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override earlier ones. Available options are:
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=over 8
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=item B<context>
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Produces a warning whenever an array is used in an implicit scalar
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context. For example, both of the lines
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$foo = length(@bar);
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$foo = @bar;
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will elicit a warning. Using an explicit B<scalar()> silences the
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warning. For example,
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$foo = scalar(@bar);
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=item B<implicit-read> and B<implicit-write>
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These options produce a warning whenever an operation implicitly
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reads or (respectively) writes to one of Perl's special variables.
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For example, B<implicit-read> will warn about these:
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/foo/;
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and B<implicit-write> will warn about these:
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s/foo/bar/;
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Both B<implicit-read> and B<implicit-write> warn about this:
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for (@a) { ... }
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=item B<dollar-underscore>
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This option warns whenever $_ is used either explicitly anywhere or
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as the implicit argument of a B<print> statement.
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=item B<private-names>
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This option warns on each use of any variable, subroutine or
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method name that lives in a non-current package but begins with
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an underscore ("_"). Warnings aren't issued for the special case
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of the single character name "_" by itself (e.g. $_ and @_).
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=item B<undefined-subs>
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This option warns whenever an undefined subroutine is invoked.
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This option will only catch explicitly invoked subroutines such
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as C<foo()> and not indirect invocations such as C<&$subref()>
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or C<$obj-E<gt>meth()>. Note that some programs or modules delay
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definition of subs until runtime by means of the AUTOLOAD
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mechanism.
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=item B<regexp-variables>
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This option warns whenever one of the regexp variables $', $& or
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$' is used. Any occurrence of any of these variables in your
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program can slow your whole program down. See L<perlre> for
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details.
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=item B<all>
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Turn all warnings on.
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=item B<none>
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Turn all warnings off.
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=back
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=head1 NON LINT-CHECK OPTIONS
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=over 8
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=item B<-u Package>
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Normally, Lint only checks the main code of the program together
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with all subs defined in package main. The B<-u> option lets you
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include other package names whose subs are then checked by Lint.
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=back
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=head1 BUGS
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This is only a very preliminary version.
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=head1 AUTHOR
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Malcolm Beattie, mbeattie@sable.ox.ac.uk.
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=cut
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use strict;
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use B qw(walkoptree_slow main_root walksymtable svref_2object parents);
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# Constants (should probably be elsewhere)
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sub G_ARRAY () { 1 }
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sub OPf_LIST () { 1 }
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sub OPf_KNOW () { 2 }
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sub OPf_STACKED () { 64 }
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my $file = "unknown"; # shadows current filename
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my $line = 0; # shadows current line number
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my $curstash = "main"; # shadows current stash
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# Lint checks
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my %check;
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my %implies_ok_context;
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BEGIN {
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map($implies_ok_context{$_}++,
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qw(pp_scalar pp_av2arylen pp_aelem pp_aslice pp_helem pp_hslice
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pp_keys pp_values pp_hslice pp_defined pp_undef pp_delete));
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}
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# Lint checks turned on by default
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my @default_checks = qw(context);
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my %valid_check;
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# All valid checks
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BEGIN {
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map($valid_check{$_}++,
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qw(context implicit_read implicit_write dollar_underscore
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private_names undefined_subs regexp_variables));
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}
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# Debugging options
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my ($debug_op);
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my %done_cv; # used to mark which subs have already been linted
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my @extra_packages; # Lint checks mainline code and all subs which are
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# in main:: or in one of these packages.
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sub warning {
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my $format = (@_ < 2) ? "%s" : shift;
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warn sprintf("$format at %s line %d\n", @_, $file, $line);
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}
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# This gimme can't cope with context that's only determined
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# at runtime via dowantarray().
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sub gimme {
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my $op = shift;
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my $flags = $op->flags;
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if ($flags & OPf_KNOW) {
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return(($flags & OPf_LIST) ? 1 : 0);
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}
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return undef;
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}
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sub B::OP::lint {}
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sub B::COP::lint {
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my $op = shift;
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if ($op->ppaddr eq "pp_nextstate") {
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$file = $op->filegv->SV->PV;
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$line = $op->line;
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$curstash = $op->stash->NAME;
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}
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}
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sub B::UNOP::lint {
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my $op = shift;
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my $ppaddr = $op->ppaddr;
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if ($check{context} && ($ppaddr eq "pp_rv2av" || $ppaddr eq "pp_rv2hv")) {
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my $parent = parents->[0];
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my $pname = $parent->ppaddr;
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return if gimme($op) || $implies_ok_context{$pname};
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# Two special cases to deal with: "foreach (@foo)" and "delete $a{$b}"
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# null out the parent so we have to check for a parent of pp_null and
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# a grandparent of pp_enteriter or pp_delete
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if ($pname eq "pp_null") {
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my $gpname = parents->[1]->ppaddr;
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return if $gpname eq "pp_enteriter" || $gpname eq "pp_delete";
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}
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warning("Implicit scalar context for %s in %s",
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$ppaddr eq "pp_rv2av" ? "array" : "hash", $parent->desc);
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}
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if ($check{private_names} && $ppaddr eq "pp_method") {
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my $methop = $op->first;
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if ($methop->ppaddr eq "pp_const") {
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my $method = $methop->sv->PV;
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if ($method =~ /^_/ && !defined(&{"$curstash\::$method"})) {
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warning("Illegal reference to private method name $method");
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}
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}
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}
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}
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sub B::PMOP::lint {
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my $op = shift;
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if ($check{implicit_read}) {
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my $ppaddr = $op->ppaddr;
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if ($ppaddr eq "pp_match" && !($op->flags & OPf_STACKED)) {
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warning('Implicit match on $_');
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}
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}
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if ($check{implicit_write}) {
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my $ppaddr = $op->ppaddr;
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if ($ppaddr eq "pp_subst" && !($op->flags & OPf_STACKED)) {
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warning('Implicit substitution on $_');
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}
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}
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}
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sub B::LOOP::lint {
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my $op = shift;
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if ($check{implicit_read} || $check{implicit_write}) {
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my $ppaddr = $op->ppaddr;
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if ($ppaddr eq "pp_enteriter") {
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my $last = $op->last;
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if ($last->ppaddr eq "pp_gv" && $last->gv->NAME eq "_") {
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warning('Implicit use of $_ in foreach');
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}
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}
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}
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}
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sub B::GVOP::lint {
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my $op = shift;
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if ($check{dollar_underscore} && $op->ppaddr eq "pp_gvsv"
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&& $op->gv->NAME eq "_")
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{
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warning('Use of $_');
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}
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if ($check{private_names}) {
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my $ppaddr = $op->ppaddr;
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my $gv = $op->gv;
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if (($ppaddr eq "pp_gv" || $ppaddr eq "pp_gvsv")
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&& $gv->NAME =~ /^_./ && $gv->STASH->NAME ne $curstash)
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{
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warning('Illegal reference to private name %s', $gv->NAME);
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}
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}
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if ($check{undefined_subs}) {
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if ($op->ppaddr eq "pp_gv" && $op->next->ppaddr eq "pp_entersub") {
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my $gv = $op->gv;
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my $subname = $gv->STASH->NAME . "::" . $gv->NAME;
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no strict 'refs';
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if (!defined(&$subname)) {
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$subname =~ s/^main:://;
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warning('Undefined subroutine %s called', $subname);
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}
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}
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}
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if ($check{regexp_variables} && $op->ppaddr eq "pp_gvsv") {
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my $name = $op->gv->NAME;
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if ($name =~ /^[&'`]$/) {
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warning('Use of regexp variable $%s', $name);
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}
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}
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}
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sub B::GV::lintcv {
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my $gv = shift;
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my $cv = $gv->CV;
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#warn sprintf("lintcv: %s::%s (done=%d)\n",
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# $gv->STASH->NAME, $gv->NAME, $done_cv{$$cv});#debug
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return if !$$cv || $done_cv{$$cv}++;
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my $root = $cv->ROOT;
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#warn " root = $root (0x$$root)\n";#debug
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walkoptree_slow($root, "lint") if $$root;
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}
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sub do_lint {
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my %search_pack;
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walkoptree_slow(main_root, "lint") if ${main_root()};
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# Now do subs in main
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no strict qw(vars refs);
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my $sym;
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local(*glob);
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while (($sym, *glob) = each %{"main::"}) {
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#warn "Trying $sym\n";#debug
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svref_2object(\*glob)->EGV->lintcv unless $sym =~ /::$/;
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}
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# Now do subs in non-main packages given by -u options
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map { $search_pack{$_} = 1 } @extra_packages;
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walksymtable(\%{"main::"}, "lintcv", sub {
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my $package = shift;
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$package =~ s/::$//;
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#warn "Considering $package\n";#debug
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return exists $search_pack{$package};
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});
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}
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sub compile {
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my @options = @_;
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my ($option, $opt, $arg);
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# Turn on default lint checks
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for $opt (@default_checks) {
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$check{$opt} = 1;
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}
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OPTION:
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while ($option = shift @options) {
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if ($option =~ /^-(.)(.*)/) {
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$opt = $1;
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$arg = $2;
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} else {
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unshift @options, $option;
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last OPTION;
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}
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if ($opt eq "-" && $arg eq "-") {
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shift @options;
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last OPTION;
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} elsif ($opt eq "D") {
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$arg ||= shift @options;
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foreach $arg (split(//, $arg)) {
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if ($arg eq "o") {
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B->debug(1);
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} elsif ($arg eq "O") {
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$debug_op = 1;
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}
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}
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} elsif ($opt eq "u") {
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$arg ||= shift @options;
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push(@extra_packages, $arg);
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}
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}
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foreach $opt (@default_checks, @options) {
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$opt =~ tr/-/_/;
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if ($opt eq "all") {
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%check = %valid_check;
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}
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elsif ($opt eq "none") {
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%check = ();
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}
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else {
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if ($opt =~ s/^no-//) {
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$check{$opt} = 0;
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}
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else {
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$check{$opt} = 1;
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}
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warn "No such check: $opt\n" unless defined $valid_check{$opt};
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}
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}
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# Remaining arguments are things to check
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return \&do_lint;
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}
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1;
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