View of /trunk/pg/lib/ww_strict.pm

    1 package ww_strict;
    2 
    3 $strict::VERSION = "1.03";
    4 
    5 =head1 NAME
    6 
    7 strict - Perl pragma to restrict unsafe constructs
    8 
    9 =head1 SYNOPSIS
   10 
   11     use strict;
   12 
   13     use strict "vars";
   14     use strict "refs";
   15     use strict "subs";
   16 
   17     use strict;
   18     no strict "vars";
   19 
   20 =head1 DESCRIPTION
   21 
   22 If no import list is supplied, all possible restrictions are assumed.
   23 (This is the safest mode to operate in, but is sometimes too strict for
   24 casual programming.)  Currently, there are three possible things to be
   25 strict about:  "subs", "vars", and "refs".
   26 
   27 =over 6
   28 
   29 =item C<strict refs>
   30 
   31 This generates a runtime error if you
   32 use symbolic references (see L<perlref>).
   33 
   34     use strict 'refs';
   35     $ref = \$foo;
   36     print $$ref;  # ok
   37     $ref = "foo";
   38     print $$ref;  # runtime error; normally ok
   39     $file = "STDOUT";
   40     print $file "Hi!";  # error; note: no comma after $file
   41 
   42 =item C<strict vars>
   43 
   44 This generates a compile-time error if you access a variable that wasn't
   45 declared via "our" or C<use vars>,
   46 localized via C<my()>, or wasn't fully qualified.  Because this is to avoid
   47 variable suicide problems and subtle dynamic scoping issues, a merely
   48 local() variable isn't good enough.  See L<perlfunc/my> and
   49 L<perlfunc/local>.
   50 
   51     use strict 'vars';
   52     $X::foo = 1;   # ok, fully qualified
   53     my $foo = 10;  # ok, my() var
   54     local $foo = 9;  # blows up
   55 
   56     package Cinna;
   57     our $bar;     # Declares $bar in current package
   58     $bar = 'HgS';   # ok, global declared via pragma
   59 
   60 The local() generated a compile-time error because you just touched a global
   61 name without fully qualifying it.
   62 
   63 Because of their special use by sort(), the variables $a and $b are
   64 exempted from this check.
   65 
   66 =item C<strict subs>
   67 
   68 This disables the poetry optimization, generating a compile-time error if
   69 you try to use a bareword identifier that's not a subroutine, unless it
   70 appears in curly braces or on the left hand side of the "=E<gt>" symbol.
   71 
   72 
   73     use strict 'subs';
   74     $SIG{PIPE} = Plumber;     # blows up
   75     $SIG{PIPE} = "Plumber";   # just fine: bareword in curlies always ok
   76     $SIG{PIPE} = \&Plumber;   # preferred form
   77 
   78 
   79 
   80 =back
   81 
   82 See L<perlmodlib/Pragmatic Modules>.
   83 
   84 
   85 =cut
   86 
   87 $strict::VERSION = "1.01";
   88 
   89 my %bitmask = (
   90 refs => 0x00000002,
   91 subs => 0x00000200,
   92 vars => 0x00000400
   93 );
   94 
   95 sub bits {
   96     my $bits = 0;
   97     my @wrong;
   98     foreach my $s (@_) {
   99   push @wrong, $s unless exists $bitmask{$s};
  100         $bits |= $bitmask{$s} || 0;
  101     }
  102     if (@wrong) {
  103         #require Carp;
  104         Carp::croak("Unknown 'strict' tag(s) '@wrong'");
  105     }
  106     $bits;
  107 }
  108 
  109 my $default_bits = bits(qw(refs subs vars));
  110 
  111 sub import {
  112     shift;
  113     $^H |= @_ ? bits(@_) : $default_bits;
  114 }
  115 
  116 sub unimport {
  117     shift;
  118     $^H &= ~ bits(@_ ? @_ : qw(refs subs vars));
  119 }
  120 
  121 1;
  122 __END__
  123