1 | package strict; |
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2 | |
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3 | =head1 NAME |
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4 | |
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5 | strict - Perl pragma to restrict unsafe constructs |
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6 | |
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7 | =head1 SYNOPSIS |
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8 | |
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9 | use strict; |
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10 | |
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11 | use strict "vars"; |
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12 | use strict "refs"; |
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13 | use strict "subs"; |
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14 | |
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15 | use strict; |
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16 | no strict "vars"; |
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17 | |
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18 | =head1 DESCRIPTION |
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19 | |
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20 | If no import list is supplied, all possible restrictions are assumed. |
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21 | (This is the safest mode to operate in, but is sometimes too strict for |
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22 | casual programming.) Currently, there are three possible things to be |
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23 | strict about: "subs", "vars", and "refs". |
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24 | |
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25 | =over 6 |
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26 | |
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27 | =item C<strict refs> |
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28 | |
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29 | This generates a runtime error if you |
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30 | use symbolic references (see L<perlref>). |
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31 | |
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32 | use strict 'refs'; |
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33 | $ref = \$foo; |
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34 | print $$ref; # ok |
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35 | $ref = "foo"; |
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36 | print $$ref; # runtime error; normally ok |
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37 | $file = "STDOUT"; |
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38 | print $file "Hi!"; # error; note: no comma after $file |
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39 | |
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40 | =item C<strict vars> |
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41 | |
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42 | This generates a compile-time error if you access a variable that wasn't |
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43 | declared via "our" or C<use vars>, |
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44 | localized via C<my()>, or wasn't fully qualified. Because this is to avoid |
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45 | variable suicide problems and subtle dynamic scoping issues, a merely |
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46 | local() variable isn't good enough. See L<perlfunc/my> and |
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47 | L<perlfunc/local>. |
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48 | |
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49 | use strict 'vars'; |
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50 | $X::foo = 1; # ok, fully qualified |
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51 | my $foo = 10; # ok, my() var |
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52 | local $foo = 9; # blows up |
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53 | |
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54 | package Cinna; |
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55 | our $bar; # Declares $bar in current package |
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56 | $bar = 'HgS'; # ok, global declared via pragma |
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57 | |
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58 | The local() generated a compile-time error because you just touched a global |
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59 | name without fully qualifying it. |
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60 | |
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61 | Because of their special use by sort(), the variables $a and $b are |
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62 | exempted from this check. |
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63 | |
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64 | =item C<strict subs> |
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65 | |
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66 | This disables the poetry optimization, generating a compile-time error if |
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67 | you try to use a bareword identifier that's not a subroutine, unless it |
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68 | appears in curly braces or on the left hand side of the "=E<gt>" symbol. |
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69 | |
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70 | |
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71 | use strict 'subs'; |
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72 | $SIG{PIPE} = Plumber; # blows up |
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73 | $SIG{PIPE} = "Plumber"; # just fine: bareword in curlies always ok |
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74 | $SIG{PIPE} = \&Plumber; # preferred form |
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75 | |
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76 | |
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77 | |
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78 | =back |
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79 | |
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80 | See L<perlmodlib/Pragmatic Modules>. |
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81 | |
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82 | |
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83 | =cut |
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84 | |
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85 | $strict::VERSION = "1.01"; |
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86 | |
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87 | my %bitmask = ( |
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88 | refs => 0x00000002, |
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89 | subs => 0x00000200, |
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90 | vars => 0x00000400 |
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91 | ); |
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92 | |
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93 | sub bits { |
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94 | my $bits = 0; |
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95 | foreach my $s (@_){ $bits |= $bitmask{$s} || 0; }; |
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96 | $bits; |
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97 | } |
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98 | |
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99 | sub import { |
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100 | shift; |
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101 | $^H |= bits(@_ ? @_ : qw(refs subs vars)); |
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102 | } |
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103 | |
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104 | sub unimport { |
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105 | shift; |
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106 | $^H &= ~ bits(@_ ? @_ : qw(refs subs vars)); |
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107 | } |
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108 | |
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109 | 1; |
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