no indirect; # lexically enables the pragma my $x = new Apple 1, 2, 3; # warns { use indirect; # lexically disables the pragma my $y = new Pear; # legit, does not warn { # lexically specify an hook called for each indirect construct no indirect hook => sub { die "You really wanted $_[0]\->$_[1] at $_[2]:$_[3]" }; my $z = new Pineapple 'fresh'; # croaks 'You really wanted...' } } try { ... }; # warns if try() hasn't been declared in this package no indirect 'fatal'; # or ':fatal', 'FATAL', ':Fatal' ... if (defied $foo) { ... } # croaks, note the typo
Global uses :
# Globally enable the pragma from the command-line perl -M-indirect=global -e 'my $x = new Banana;' # warns # Globally enforce the pragma each time perl is executed export PERL5OPT="-M-indirect=global,fatal" perl -e 'my $y = new Coconut;' # croaks
The indirect syntax is now considered harmful, since its parsing has many quirks and its use is error prone : when the subroutine "foo" has not been declared in the current package, "foo $x" actually compiles to "$x->foo", and "foo { key => 1 }" to "'key'->foo(1)". Please refer to the ``REFERENCES'' section for a more complete list of reasons for avoiding this construct.
This pragma currently does not warn for core functions ("print", "say", "exec" or "system"). This may change in the future, or may be added as optional features that would be enabled by passing options to "unimport".
This module is not a source filter.
no indirect; no indirect 'fatal'; no indirect hook => sub { my ($obj, $name, $file, $line) = @_; ... }; no indirect 'global'; no indirect 'global, 'fatal'; no indirect 'global', hook => sub { ... };
Magically called when "no indirect @opts" is encountered. Turns the module on. The policy to apply depends on what is first found in @opts :
This option is mutually exclusive with the 'hook' option.
This option is mutually exclusive with the 'fatal' option.
The global policy applied is the one resulting of the "fatal" or "hook" options, thus defaults to a warning when none of those are specified :
no indirect 'global'; # warn for any indirect call no indirect qw<global fatal>; # die on any indirect call no indirect 'global', hook => \&hook # custom global action
Note that if another policy is installed by a "no indirect" statement further in the code, it will overrule the global policy :
no indirect 'global'; # warn globally { no indirect 'fatal'; # throw exceptions for this lexical scope ... require Some::Module; # the global policy will apply for the # compilation phase of this module }
use indirect;
Magically called at each "use indirect". Turns the module off.
As explained in ``unimport'''s description, an "use indirect" statement will lexically override a global policy previously installed by "no indirect 'global', ..." (if there's one).
my $msg = msg($object, $method, $file, $line);
Returns the default error message that "indirect" generates when an indirect method call is reported.
Note that clearing this variable after "indirect" was loaded has no effect. If you want to re-enable the pragma later, you also need to reload it by deleting the 'indirect.pm' entry from %INC.
Before "perl" 5.12, "meth $obj" (no semicolon) at the end of a file is not seen as an indirect method call, although it is as soon as there is another token before the end (as in "meth $obj;" or "meth $obj 1"). If you use "perl" 5.12 or greater, those constructs are correctly reported.
With 5.8 perls, the pragma does not propagate into "eval STRING". This is due to a shortcoming in the way perl handles the hints hash, which is addressed in perl 5.10.
The search for indirect method calls happens before constant folding. Hence "my $x = new Class if 0" will be caught.
This historical post to the "perl5-porters" mailing list raised awareness about the perils of this syntax.
In this blog post, the author gives an example of an undesirable indirect method call on a block that causes a particularly bewildering error.
A C compiler. This module may happen to build with a C++ compiler as well, but don't rely on it, as no guarantee is made in this regard.
Carp (standard since perl 5), XSLoader (since perl 5.6.0).
You can contact me by mail or on "irc.perl.org" (vincent).
perldoc indirect
Andrew Main and Florian Ragwitz, for testing on real-life code and reporting issues.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.