This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
File/Find/t/find.t tests 1 and 2 (was Re: [perl #17061] no strict 'garbage')
[perl5.git] / lib / strict.pm
CommitLineData
a0d0e21e
LW
1package strict;
2
f06db76b
AD
3=head1 NAME
4
5strict - Perl pragma to restrict unsafe constructs
6
7=head1 SYNOPSIS
8
9 use strict;
10
11 use strict "vars";
12 use strict "refs";
13 use strict "subs";
14
15 use strict;
16 no strict "vars";
17
18=head1 DESCRIPTION
19
20If no import list is supplied, all possible restrictions are assumed.
21(This is the safest mode to operate in, but is sometimes too strict for
55497cff
PP
22casual programming.) Currently, there are three possible things to be
23strict about: "subs", "vars", and "refs".
f06db76b
AD
24
25=over 6
26
27=item C<strict refs>
28
29This generates a runtime error if you
30use symbolic references (see L<perlref>).
31
32 use strict 'refs';
33 $ref = \$foo;
34 print $$ref; # ok
35 $ref = "foo";
36 print $$ref; # runtime error; normally ok
d6fd2b02
GS
37 $file = "STDOUT";
38 print $file "Hi!"; # error; note: no comma after $file
f06db76b 39
cec39fc8
RS
40There is one exception to this rule:
41
42 $bar = \&{'foo'};
43 &$bar;
44
45is allowed so that C<goto &$AUTOLOAD> would not break under stricture.
46
47
f06db76b
AD
48=item C<strict vars>
49
50This generates a compile-time error if you access a variable that wasn't
17f410f9
GS
51declared via "our" or C<use vars>,
52localized via C<my()>, or wasn't fully qualified. Because this is to avoid
f06db76b
AD
53variable suicide problems and subtle dynamic scoping issues, a merely
54local() variable isn't good enough. See L<perlfunc/my> and
55L<perlfunc/local>.
56
57 use strict 'vars';
58 $X::foo = 1; # ok, fully qualified
59 my $foo = 10; # ok, my() var
60 local $foo = 9; # blows up
61
535b5725 62 package Cinna;
17f410f9 63 our $bar; # Declares $bar in current package
535b5725
TP
64 $bar = 'HgS'; # ok, global declared via pragma
65
f06db76b
AD
66The local() generated a compile-time error because you just touched a global
67name without fully qualifying it.
68
3ce0d271
GS
69Because of their special use by sort(), the variables $a and $b are
70exempted from this check.
71
f06db76b
AD
72=item C<strict subs>
73
cb1a09d0
AD
74This disables the poetry optimization, generating a compile-time error if
75you try to use a bareword identifier that's not a subroutine, unless it
1fef88e7 76appears in curly braces or on the left hand side of the "=E<gt>" symbol.
cb1a09d0 77
f06db76b
AD
78
79 use strict 'subs';
80 $SIG{PIPE} = Plumber; # blows up
cb1a09d0
AD
81 $SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok
82 $SIG{PIPE} = \&Plumber; # preferred form
83
84
f06db76b
AD
85
86=back
87
ee580363 88See L<perlmodlib/Pragmatic Modules>.
f06db76b
AD
89
90
91=cut
92
d6a466d7 93$strict::VERSION = "1.02";
4682965a
MB
94
95my %bitmask = (
96refs => 0x00000002,
97subs => 0x00000200,
98vars => 0x00000400
99);
100
a0d0e21e
LW
101sub bits {
102 my $bits = 0;
210bfd0c
EM
103 my @wrong;
104 foreach my $s (@_) {
105 push @wrong, $s unless exists $bitmask{$s};
106 $bits |= $bitmask{$s} || 0;
107 }
108 if (@wrong) {
109 my $useno = {
110 __PACKAGE__.'::import' => 'use',
111 __PACKAGE__.'::unimport' => 'no'
112 }->{ (caller(1))[3] };
113 require Carp;
114 Carp::croak("Don't know how to '$useno ".__PACKAGE__." qw(@wrong)'");
115 }
a0d0e21e
LW
116 $bits;
117}
118
119sub import {
120 shift;
55497cff 121 $^H |= bits(@_ ? @_ : qw(refs subs vars));
a0d0e21e
LW
122}
123
124sub unimport {
125 shift;
55497cff 126 $^H &= ~ bits(@_ ? @_ : qw(refs subs vars));
a0d0e21e
LW
127}
128
1291;