1indirect(3) User Contributed Perl Documentation indirect(3)
2
6 indirect - Lexically warn about using the indirect object syntax.
7
9 Version 0.24
10
12 # In a script
13 no indirect;
14 my $x = new Apple 1, 2, 3; # warns
15 {
16 use indirect;
17 my $y = new Pear; # ok
18 {
19 no indirect hook => sub { die "You really wanted $_[0]\->$_[1] at $_[2]:$_[3]" };
20 my $z = new Pineapple 'fresh'; # croaks 'You really wanted Pineapple->new at blurp.pm:13'
21 }
22 }
23 try { ... }; # warns
24 no indirect ':fatal'; # or 'FATAL', or ':Fatal' ...
26 if (defied $foo) { ... } # croaks, note the typo
27 # From the command-line
29 perl -M-indirect -e 'my $x = new Banana;' # warns
30 # Or each time perl is ran
32 export PERL5OPT="-M-indirect"
33 perl -e 'my $y = new Coconut;' # warns
34
36 When enabled (or disabled as some may prefer to say, since you actually
37 turn it on by calling "no indirect"), this pragma warns about indirect
38 object syntax constructs that may have slipped into your code.
39 This syntax is now considered harmful, since its parsing has many
41 quirks and its use is error prone (when "swoosh" is not defined,
42 "swoosh $x" actually compiles to "$x->swoosh"). In
43 http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-fatal
44 <http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-
45 fatal>, Matt S. Trout gives an example of an indirect construct that
46 can cause a particularly bewildering error.
47 It currently does not warn for core functions ("print", "say", "exec"
49 or "system"). This may change in the future, or may be added as
50 optional features that would be enabled by passing options to
51 "unimport".
52 This module is not a source filter.
54
56 "unimport [ hook => $hook | ':fatal', 'FATAL', ... ]"
57 Magically called when "no indirect @opts" is encountered. Turns the
58 module on. The policy to apply depends on what is first found in @opts
59 :
60 · If it is a string that matches "/^:?fatal$/i", the compilation will
62 croak on the first indirect syntax met.
63 · If the key/value pair "hook => $hook" comes first, $hook will be
65 called for each error with a string representation of the object as
66 $_[0], the method name as $_[1], the current file as $_[2] and the
67 line number as $_[3]. If and only if the object is actually a
68 block, $_[0] is assured to start by '{'.
69 · Otherwise, a warning will be emitted for each indirect construct.
71 "import"
73 Magically called at each "use indirect". Turns the module off.
74
76 "msg $object, $method, $file, $line"
77 Returns the default error message generated by "indirect" when an
78 invalid construct is reported.
79
81 "I_THREADSAFE"
82 True iff the module could have been built with thread-safety features
83 enabled.
84 "I_FORKSAFE"
86 True iff this module could have been built with fork-safety features
87 enabled. This will always be true except on Windows where it's false
88 for perl 5.10.0 and below .
89
91 "Indirect call of method "%s" on object "%s" at %s line %d."
92 The default warning/exception message thrown when an indirect call on
93 an object is found.
94 "Indirect call of method "%s" on a block at %s line %d."
96 The default warning/exception message thrown when an indirect call on a
97 block is found.
98
100 "PERL_INDIRECT_PM_DISABLE"
101 If this environment variable is set to true when the pragma is used for
102 the first time, the XS code won't be loaded and, although the
103 'indirect' lexical hint will be set to true in the scope of use, the
104 pragma itself won't do anything. In this case, the pragma will always
105 be considered to be thread-safe, and as such "I_THREADSAFE" will be
106 true. This is useful for disabling "indirect" in production
107 environments.
108 Note that clearing this variable after "indirect" was loaded has no
110 effect. If you want to re-enable the pragma later, you also need to
111 reload it by deleting the 'indirect.pm' entry from %INC.
112
114 The implementation was tweaked to work around several limitations of
115 vanilla "perl" pragmas : it's thread safe, and does not suffer from a
116 "perl 5.8.x-5.10.0" bug that causes all pragmas to propagate into
117 "require"d scopes.
118 Before "perl" 5.12, "meth $obj" (no semicolon) at the end of a file is
120 not seen as an indirect object syntax, although it is as soon as there
121 is another token before the end (as in "meth $obj;" or "meth $obj 1").
122 If you use "perl" 5.12 or greater, those constructs are correctly
123 reported.
124 With 5.8 perls, the pragma does not propagate into "eval STRING". This
126 is due to a shortcoming in the way perl handles the hints hash, which
127 is addressed in perl 5.10.
128 The search for indirect method calls happens before constant folding.
130 Hence "my $x = new Class if 0" will be caught.
131
133 perl 5.8.1.
134 A C compiler. This module may happen to build with a C++ compiler as
136 well, but don't rely on it, as no guarantee is made in this regard.
137 XSLoader (standard since perl 5.006).
139
141 Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
142 You can contact me by mail or on "irc.perl.org" (vincent).
144
146 Please report any bugs or feature requests to "bug-indirect at
147 rt.cpan.org", or through the web interface at
148 <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=indirect>. I will be
149 notified, and then you'll automatically be notified of progress on your
150 bug as I make changes.
151
153 You can find documentation for this module with the perldoc command.
154 perldoc indirect
156 Tests code coverage report is available at
158 <http://www.profvince.com/perl/cover/indirect>.
159
161 Bram, for motivation and advices.
162 Andrew Main and Florian Ragwitz, for testing on real-life code and
164 reporting issues.
165
167 Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
168 This program is free software; you can redistribute it and/or modify it
170 under the same terms as Perl itself.
171perl v5.12.3 2011-07-17 indirect(3)