2 indirect - Lexically warn about using the indirect method call syntax.
10 no indirect; # lexically enables the pragma
11 my $x = new Apple 1, 2, 3; # warns
13 use indirect; # lexically disables the pragma
14 my $y = new Pear; # legit, does not warn
16 # lexically specify an hook called for each indirect construct
17 no indirect hook => sub {
18 die "You really wanted $_[0]\->$_[1] at $_[2]:$_[3]"
20 my $z = new Pineapple 'fresh'; # croaks 'You really wanted...'
23 try { ... }; # warns if try() hasn't been declared in this package
25 no indirect 'fatal'; # or ':fatal', 'FATAL', ':Fatal' ...
26 if (defied $foo) { ... } # croaks, note the typo
30 # Globally enable the pragma from the command-line
31 perl -M-indirect=global -e 'my $x = new Banana;' # warns
33 # Globally enforce the pragma each time perl is executed
34 export PERL5OPT="-M-indirect=global,fatal"
35 perl -e 'my $y = new Coconut;' # croaks
38 When enabled, this pragma warns about indirect method calls that are
41 The indirect syntax is now considered harmful, since its parsing has
42 many quirks and its use is error prone : when the subroutine "foo" has
43 not been declared in the current package, "foo $x" actually compiles to
44 "$x->foo", and "foo { key => 1 }" to "'key'->foo(1)". In
45 <http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-fatal>,
46 Matt S. Trout gives an example of an undesirable indirect method call on
47 a block that can cause a particularly bewildering error.
49 This pragma currently does not warn for core functions ("print", "say",
50 "exec" or "system"). This may change in the future, or may be added as
51 optional features that would be enabled by passing options to
54 This module is not a source filter.
60 no indirect hook => sub { my ($obj, $name, $file, $line) = @_; ... };
62 no indirect 'global, 'fatal';
63 no indirect 'global', hook => sub { ... };
65 Magically called when "no indirect @opts" is encountered. Turns the
66 module on. The policy to apply depends on what is first found in @opts :
68 * If it is a string that matches "/^:?fatal$/i", the compilation will
69 croak when the first indirect method call is found.
71 This option is mutually exclusive with the 'hook' option.
73 * If the key/value pair "hook => $hook" comes first, $hook will be
74 called for each error with a string representation of the object as
75 $_[0], the method name as $_[1], the current file as $_[2] and the
76 line number as $_[3]. If and only if the object is actually a block,
77 $_[0] is assured to start by '{'.
79 This option is mutually exclusive with the 'fatal' option.
81 * If none of "fatal" and "hook" are specified, a warning will be
82 emitted for each indirect method call.
84 * If @opts contains a string that matches "/^:?global$/i", the pragma
85 will be globally enabled for all code compiled after the current "no
86 indirect" statement, except for code that is in the lexical scope of
87 "use indirect". This option may come indifferently before or after
88 the "fatal" or "hook" options, in the case they are also passed to
91 The global policy applied is the one resulting of the "fatal" or
92 "hook" options, thus defaults to a warning when none of those are
95 no indirect 'global'; # warn for any indirect call
96 no indirect qw<global fatal>; # die on any indirect call
97 no indirect 'global', hook => \&hook # custom global action
99 Note that if another policy is installed by a "no indirect"
100 statement further in the code, it will overrule the global policy :
102 no indirect 'global'; # warn globally
104 no indirect 'fatal'; # throw exceptions for this lexical scope
106 require Some::Module; # the global policy will apply for the
107 # compilation phase of this module
113 Magically called at each "use indirect". Turns the module off.
115 As explained in "unimport"'s description, an "use indirect" statement
116 will lexically override a global policy previously installed by "no
117 indirect 'global', ..." (if there's one).
121 my $msg = msg($object, $method, $file, $line);
123 Returns the default error message that "indirect" generates when an
124 indirect method call is reported.
128 True iff the module could have been built with thread-safety features
132 True iff this module could have been built with fork-safety features
133 enabled. This will always be true except on Windows where it's false for
134 perl 5.10.0 and below .
137 "Indirect call of method "%s" on object "%s" at %s line %d."
138 The default warning/exception message thrown when an indirect method
139 call on an object is found.
141 "Indirect call of method "%s" on a block at %s line %d."
142 The default warning/exception message thrown when an indirect method
143 call on a block is found.
146 "PERL_INDIRECT_PM_DISABLE"
147 If this environment variable is set to true when the pragma is used for
148 the first time, the XS code won't be loaded and, although the 'indirect'
149 lexical hint will be set to true in the scope of use, the pragma itself
150 won't do anything. In this case, the pragma will always be considered to
151 be thread-safe, and as such "I_THREADSAFE" will be true. This is useful
152 for disabling "indirect" in production environments.
154 Note that clearing this variable after "indirect" was loaded has no
155 effect. If you want to re-enable the pragma later, you also need to
156 reload it by deleting the 'indirect.pm' entry from %INC.
159 The implementation was tweaked to work around several limitations of
160 vanilla "perl" pragmas : it's thread safe, and does not suffer from a
161 "perl 5.8.x-5.10.0" bug that causes all pragmas to propagate into
164 Before "perl" 5.12, "meth $obj" (no semicolon) at the end of a file is
165 not seen as an indirect method call, although it is as soon as there is
166 another token before the end (as in "meth $obj;" or "meth $obj 1"). If
167 you use "perl" 5.12 or greater, those constructs are correctly reported.
169 With 5.8 perls, the pragma does not propagate into "eval STRING". This
170 is due to a shortcoming in the way perl handles the hints hash, which is
171 addressed in perl 5.10.
173 The search for indirect method calls happens before constant folding.
174 Hence "my $x = new Class if 0" will be caught.
179 A C compiler. This module may happen to build with a C++ compiler as
180 well, but don't rely on it, as no guarantee is made in this regard.
182 Carp (standard since perl 5), XSLoader (since perl 5.006).
185 Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
187 You can contact me by mail or on "irc.perl.org" (vincent).
190 Please report any bugs or feature requests to "bug-indirect at
191 rt.cpan.org", or through the web interface at
192 <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=indirect>. I will be
193 notified, and then you'll automatically be notified of progress on your
194 bug as I make changes.
197 You can find documentation for this module with the perldoc command.
201 Tests code coverage report is available at
202 <http://www.profvince.com/perl/cover/indirect>.
205 Bram, for motivation and advices.
207 Andrew Main and Florian Ragwitz, for testing on real-life code and
211 Copyright 2008,2009,2010,2011,2012,2013 Vincent Pit, all rights
214 This program is free software; you can redistribute it and/or modify it
215 under the same terms as Perl itself.