NAME¶
indirect - Lexically warn about using the indirect method call syntax.
VERSION¶
Version 0.33
SYNOPSIS¶
In a script :
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
DESCRIPTION¶
When enabled, this pragma warns about indirect method calls that are present in
your code.
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)". In
<
http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-fatal>,
Matt S. Trout gives an example of an undesirable indirect method call on a
block that can cause a particularly bewildering error.
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.
METHODS¶
"unimport"¶
no indirect;
no indirect 'fatal';
no indirect hook => sub { my ($obj, $name, $file, $line) = @_; ... };
no indirect 'global';
no indirect 'global, 'fatal';
no indirect 'global', hook => sub { ... };
Magically called when "no indirect @opts" is encountered. Turns the
module on. The policy to apply depends on what is first found in @opts :
- •
- If it is a string that matches "/^:?fatal$/i", the compilation
will croak when the first indirect method call is found.
This option is mutually exclusive with the 'hook' option.
- •
- 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, $_[0] is
assured to start by '{'.
This option is mutually exclusive with the 'fatal' option.
- •
- If none of "fatal" and "hook" are specified, a warning
will be emitted for each indirect method call.
- •
- If @opts contains a string that matches "/^:?global$/i", the
pragma will be globally enabled for all code compiled after the
current "no indirect" statement, except for code that is in the
lexical scope of "use indirect". This option may come
indifferently before or after the "fatal" or "hook"
options, in the case they are also passed to "unimport".
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
}
"import"¶
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).
FUNCTIONS¶
"msg"¶
my $msg = msg($object, $method, $file, $line);
Returns the default error message that "indirect" generates when an
indirect method call 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 method 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 method 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 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.
Indirect constructs that appear in code "eval"'d during the global
destruction phase of a spawned thread or pseudo-fork (the processes used
internally for the "fork" emulation on Windows) are not reported.
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.
Carp (standard since perl 5), XSLoader (since perl 5.6.0).
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 2008,2009,2010,2011,2012,2013,2014 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.