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.
57 "unimport [ 'global', hook => $hook | 'fatal' ]"
58 Magically called when "no indirect @opts" is encountered. Turns the
59 module on. The policy to apply depends on what is first found in @opts :
61 * If it is a string that matches "/^:?fatal$/i", the compilation will
62 croak when the first indirect method call is found.
64 This option is mutually exclusive with the 'hook' option.
66 * If the key/value pair "hook => $hook" comes first, $hook will be
67 called for each error with a string representation of the object as
68 $_[0], the method name as $_[1], the current file as $_[2] and the
69 line number as $_[3]. If and only if the object is actually a block,
70 $_[0] is assured to start by '{'.
72 This option is mutually exclusive with the 'fatal' option.
74 * If none of "fatal" and "hook" are specified, a warning will be
75 emitted for each indirect method call.
77 * If @opts contains a string that matches "/^:?global$/i", the pragma
78 will be globally enabled for all code compiled after the current "no
79 indirect" statement, except for code that is in the lexical scope of
80 "use indirect". This option may come indifferently before or after
81 the "fatal" or "hook" options, in the case they are also passed to
84 The global policy applied is the one resulting of the "fatal" or
85 "hook" options, thus defaults to a warning when none of those are
88 no indirect 'global'; # warn for any indirect call
89 no indirect qw<global fatal>; # die on any indirect call
90 no indirect 'global', hook => \&hook # custom global action
92 Note that if another policy is installed by a "no indirect"
93 statement further in the code, it will overrule the global policy :
95 no indirect 'global'; # warn globally
97 no indirect 'fatal'; # throw exceptions for this lexical scope
99 require Some::Module; # the global policy will apply for the
100 # compilation phase of this module
104 Magically called at each "use indirect". Turns the module off.
106 As explained in "unimport"'s description, an "use indirect" statement
107 will lexically override a global policy previously installed by "no
108 indirect 'global', ..." (if there's one).
111 "msg $object, $method, $file, $line"
112 Returns the default error message that "indirect" generates when an
113 indirect method call is reported.
117 True iff the module could have been built with thread-safety features
121 True iff this module could have been built with fork-safety features
122 enabled. This will always be true except on Windows where it's false for
123 perl 5.10.0 and below .
126 "Indirect call of method "%s" on object "%s" at %s line %d."
127 The default warning/exception message thrown when an indirect method
128 call on an object is found.
130 "Indirect call of method "%s" on a block at %s line %d."
131 The default warning/exception message thrown when an indirect method
132 call on a block is found.
135 "PERL_INDIRECT_PM_DISABLE"
136 If this environment variable is set to true when the pragma is used for
137 the first time, the XS code won't be loaded and, although the 'indirect'
138 lexical hint will be set to true in the scope of use, the pragma itself
139 won't do anything. In this case, the pragma will always be considered to
140 be thread-safe, and as such "I_THREADSAFE" will be true. This is useful
141 for disabling "indirect" in production environments.
143 Note that clearing this variable after "indirect" was loaded has no
144 effect. If you want to re-enable the pragma later, you also need to
145 reload it by deleting the 'indirect.pm' entry from %INC.
148 The implementation was tweaked to work around several limitations of
149 vanilla "perl" pragmas : it's thread safe, and does not suffer from a
150 "perl 5.8.x-5.10.0" bug that causes all pragmas to propagate into
153 Before "perl" 5.12, "meth $obj" (no semicolon) at the end of a file is
154 not seen as an indirect method call, although it is as soon as there is
155 another token before the end (as in "meth $obj;" or "meth $obj 1"). If
156 you use "perl" 5.12 or greater, those constructs are correctly reported.
158 With 5.8 perls, the pragma does not propagate into "eval STRING". This
159 is due to a shortcoming in the way perl handles the hints hash, which is
160 addressed in perl 5.10.
162 The search for indirect method calls happens before constant folding.
163 Hence "my $x = new Class if 0" will be caught.
168 A C compiler. This module may happen to build with a C++ compiler as
169 well, but don't rely on it, as no guarantee is made in this regard.
171 Carp (standard since perl 5), XSLoader (since perl 5.006).
174 Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
176 You can contact me by mail or on "irc.perl.org" (vincent).
179 Please report any bugs or feature requests to "bug-indirect at
180 rt.cpan.org", or through the web interface at
181 <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=indirect>. I will be
182 notified, and then you'll automatically be notified of progress on your
183 bug as I make changes.
186 You can find documentation for this module with the perldoc command.
190 Tests code coverage report is available at
191 <http://www.profvince.com/perl/cover/indirect>.
194 Bram, for motivation and advices.
196 Andrew Main and Florian Ragwitz, for testing on real-life code and
200 Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
202 This program is free software; you can redistribute it and/or modify it
203 under the same terms as Perl itself.