1B::Lint(3) User Contributed Perl Documentation B::Lint(3)
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6 B::Lint - Perl lint
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9 perl -MO=Lint[,OPTIONS] foo.pl
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12 The B::Lint module is equivalent to an extended version of the -w
13 option of perl. It is named after the program lint which carries out a
14 similar process for C programs.
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17 Option words are separated by commas (not whitespace) and follow the
18 usual conventions of compiler backend options. Following any options
19 (indicated by a leading -) come lint check arguments. Each such
20 argument (apart from the special all and none options) is a word
21 representing one possible lint check (turning on that check) or is no-
22 foo (turning off that check). Before processing the check arguments, a
23 standard list of checks is turned on. Later options override earlier
24 ones. Available options are:
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26 magic-diamond
27 Produces a warning whenever the magic "<>" readline is used.
28 Internally it uses perl's two-argument open which itself treats
29 filenames with special characters specially. This could allow
30 interestingly named files to have unexpected effects when
31 reading.
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33 % touch 'rm *|'
34 % perl -pe 1
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36 The above creates a file named "rm *|". When perl opens it with
37 "<>" it actually executes the shell program "rm *". This makes
38 "<>" dangerous to use carelessly.
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40 context Produces a warning whenever an array is used in an implicit
41 scalar context. For example, both of the lines
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43 $foo = length(@bar);
44 $foo = @bar;
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46 will elicit a warning. Using an explicit scalar() silences the
47 warning. For example,
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49 $foo = scalar(@bar);
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51 implicit-read and implicit-write
52 These options produce a warning whenever an operation
53 implicitly reads or (respectively) writes to one of Perl's
54 special variables. For example, implicit-read will warn about
55 these:
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57 /foo/;
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59 and implicit-write will warn about these:
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61 s/foo/bar/;
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63 Both implicit-read and implicit-write warn about this:
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65 for (@a) { ... }
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67 bare-subs
68 This option warns whenever a bareword is implicitly quoted, but
69 is also the name of a subroutine in the current package.
70 Typical mistakes that it will trap are:
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72 use constant foo => 'bar';
73 @a = ( foo => 1 );
74 $b{foo} = 2;
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76 Neither of these will do what a naive user would expect.
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78 Notice: Perl 5.22.0 does not report "foo" in $b{foo} as BARE
79 token anymore. Therefore B::Lint test is not reliable here. See
80 CPAN RT#101115
81 <https://rt.cpan.org/Public/Bug/Display.html?id=101115>.
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83 dollar-underscore
84 This option warns whenever $_ is used either explicitly
85 anywhere or as the implicit argument of a print statement.
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87 private-names
88 This option warns on each use of any variable, subroutine or
89 method name that lives in a non-current package but begins with
90 an underscore ("_"). Warnings aren't issued for the special
91 case of the single character name "_" by itself (e.g. $_ and
92 @_).
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94 undefined-subs
95 This option warns whenever an undefined subroutine is invoked.
96 This option will only catch explicitly invoked subroutines such
97 as "foo()" and not indirect invocations such as "&$subref()" or
98 "$obj->meth()". Note that some programs or modules delay
99 definition of subs until runtime by means of the AUTOLOAD
100 mechanism.
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102 regexp-variables
103 This option warns whenever one of the regexp variables "$`", $&
104 or "$'" is used. Any occurrence of any of these variables in
105 your program can slow your whole program down. See perlre for
106 details.
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108 all Turn all warnings on.
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110 none Turn all warnings off.
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113 -u Package
114 Normally, Lint only checks the main code of the program
115 together with all subs defined in package main. The -u option
116 lets you include other package names whose subs are then
117 checked by Lint.
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120 Lint can be extended by with plugins. Lint uses Module::Pluggable to
121 find available plugins. Plugins are expected but not required to inform
122 Lint of which checks they are adding.
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124 The "B::Lint->register_plugin( MyPlugin => \@new_checks )" method adds
125 the list of @new_checks to the list of valid checks. If your module
126 wasn't loaded by Module::Pluggable then your class name is added to the
127 list of plugins.
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129 You must create a "match( \%checks )" method in your plugin class or
130 one of its parents. It will be called on every op as a regular method
131 call with a hash ref of checks as its parameter.
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133 The class methods "B::Lint->file" and "B::Lint->line" contain the
134 current filename and line number.
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136 package Sample;
137 use B::Lint;
138 B::Lint->register_plugin( Sample => [ 'good_taste' ] );
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140 sub match {
141 my ( $op, $checks_href ) = shift @_;
142 if ( $checks_href->{good_taste} ) {
143 ...
144 }
145 }
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148 while(<FH>) stomps $_
149 strict oo
150 unchecked system calls
151 more tests, validate against older perls
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154 This is only a very preliminary version.
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157 Malcolm Beattie, mbeattie@sable.ox.ac.uk.
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160 Sebastien Aperghis-Tramoni - bug fixes
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164perl v5.32.0 2020-07-28 B::Lint(3)