indirect(3) User Contributed Perl Documentation indirect(3)NAMEindirect - Lexically warn about using the indirect object syntax.
VERSION
Version 0.24
SYNOPSIS
# In a script
no indirect;
my $x = new Apple 1, 2, 3; # warns
{
use indirect;
my $y = new Pear; # ok
{
no indirect hook => sub { die "You really wanted $_[0]\->$_[1] at $_[2]:$_[3]" };
my $z = new Pineapple 'fresh'; # croaks 'You really wanted Pineapple->new at blurp.pm:13'
}
}
try { ... }; # warns
no indirect ':fatal'; # or 'FATAL', or ':Fatal' ...
if (defied $foo) { ... } # croaks, note the typo
# From the command-line
perl -M-indirect -e 'my $x = new Banana;' # warns
# Or each time perl is ran
export PERL5OPT="-M-indirect"
perl -e 'my $y = new Coconut;' # warns
DESCRIPTION
When enabled (or disabled as some may prefer to say, since you actually
turn it on by calling "no indirect"), this pragma warns about indirect
object syntax constructs that may have slipped into your code.
This syntax is now considered harmful, since its parsing has many
quirks and its use is error prone (when "swoosh" is not defined,
"swoosh $x" actually compiles to "$x->swoosh"). In
http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-fatal
<http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-
fatal>, Matt S. Trout gives an example of an indirect construct that
can cause a particularly bewildering error.
It 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.
METHODS
"unimport [ hook => $hook | ':fatal', 'FATAL', ... ]"
Magically called when "no indirect @opts" is encountered. Turns the
module on. The policy to apply depends on what is first found in @opts
:
· If it is a string that matches "/^:?fatal$/i", the compilation will
croak on the first indirect syntax met.
· If the key/value pair "hook => $hook" comes first, $hook will be
called for each error with a string representation of the object as
$_[0], the method name as $_[1], the current file as $_[2] and the
line number as $_[3]. If and only if the object is actually a
block, $_[0] is assured to start by '{'.
· Otherwise, a warning will be emitted for each indirect construct.
"import"
Magically called at each "use indirect". Turns the module off.
FUNCTIONS
"msg $object, $method, $file, $line"
Returns the default error message generated by "indirect" when an
invalid construct is reported.
CONSTANTS
"I_THREADSAFE"
True iff the module could have been built with thread-safety features
enabled.
"I_FORKSAFE"
True iff this module could have been built with fork-safety features
enabled. This will always be true except on Windows where it's false
for perl 5.10.0 and below .
DIAGNOSTICS
"Indirect call of method "%s" on object "%s" at %s line %d."
The default warning/exception message thrown when an indirect call on
an object is found.
"Indirect call of method "%s" on a block at %s line %d."
The default warning/exception message thrown when an indirect call on a
block is found.
ENVIRONMENT
"PERL_INDIRECT_PM_DISABLE"
If this environment variable is set to true when the pragma is used for
the first time, the XS code won't be loaded and, although the
'indirect' lexical hint will be set to true in the scope of use, the
pragma itself won't do anything. In this case, the pragma will always
be considered to be thread-safe, and as such "I_THREADSAFE" will be
true. This is useful for disabling "indirect" in production
environments.
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.
CAVEATS
The implementation was tweaked to work around several limitations of
vanilla "perl" pragmas : it's thread safe, and does not suffer from a
"perl 5.8.x-5.10.0" bug that causes all pragmas to propagate into
"require"d scopes.
Before "perl" 5.12, "meth $obj" (no semicolon) at the end of a file is
not seen as an indirect object syntax, 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.
DEPENDENCIES
perl 5.8.1.
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.
XSLoader (standard since perl 5.006).
AUTHOR
Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
You can contact me by mail or on "irc.perl.org" (vincent).
BUGS
Please report any bugs or feature requests to "bug-indirect at
rt.cpan.org", or through the web interface at
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=indirect>. I will be
notified, and then you'll automatically be notified of progress on your
bug as I make changes.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc indirect
Tests code coverage report is available at
<http://www.profvince.com/perl/cover/indirect>.
ACKNOWLEDGEMENTS
Bram, for motivation and advices.
Andrew Main and Florian Ragwitz, for testing on real-life code and
reporting issues.
COPYRIGHT & LICENSE
Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.14.1 2011-07-17 indirect(3)