view release on metacpan or  search on metacpan

lib/B/Deparse.pm  view on Meta::CPAN

=item *

The only pragmas to
be completely supported are: C<use warnings>,
C<use strict>, C<use bytes>, C<use integer>
and C<use feature>.

Excepting those listed above, we're currently unable to guarantee that
B::Deparse will produce a pragma at the correct point in the program.
(Specifically, pragmas at the beginning of a block often appear right
before the start of the block instead.)
Since the effects of pragmas are often lexically scoped, this can mean
that the pragma holds sway over a different portion of the program
than in the input file.

=item *

In fact, the above is a specific instance of a more general problem:
we can't guarantee to produce BEGIN blocks or C<use> declarations in
exactly the right place.  So if you use a module which affects compilation
(such as by over-riding keywords, overloading constants or whatever)
then the output code might not work as intended.

=item *

Some constants don't print correctly either with or without B<-d>.
For instance, neither B::Deparse nor Data::Dumper know how to print
dual-valued scalars correctly, as in:

    use constant E2BIG => ($!=7); $y = E2BIG; print $y, 0+$y;

    use constant H => { "#" => 1 }; H->{"#"};

=item *

An input file that uses source filtering probably won't be deparsed into
runnable code, because it will still include the B<use> declaration
for the source filtering module, even though the code that is
produced is already ordinary Perl which shouldn't be filtered again.

=item *

Optimized-away statements are rendered as
'???'.  This includes statements that
have a compile-time side-effect, such as the obscure

    my $x if 0;

which is not, consequently, deparsed correctly.

    foreach my $i (@_) { 0 }
  =>
    foreach my $i (@_) { '???' }

=item *

Lexical (my) variables declared in scopes external to a subroutine
appear in coderef2text output text as package variables.  This is a tricky
problem, as perl has no native facility for referring to a lexical variable
defined within a different scope, although L<PadWalker> is a good start.

See also L<Data::Dump::Streamer>, which combines B::Deparse and
L<PadWalker> to serialize closures properly.

=item *

There are probably many more bugs on non-ASCII platforms (EBCDIC).

=back

=head1 AUTHOR

Stephen McCamant <smcc@CSUA.Berkeley.EDU>, based on an earlier version
by Malcolm Beattie <mbeattie@sable.ox.ac.uk>, with contributions from
Gisle Aas, James Duncan, Albert Dvornik, Robin Houston, Dave Mitchell,
Hugo van der Sanden, Gurusamy Sarathy, Nick Ing-Simmons, and Rafael
Garcia-Suarez.

=cut