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Marcus Holland-Moritz > Devel-PPPort-3.20 > Devel::PPPort



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Module Version: 3.20   Source  


Devel::PPPort - Perl/Pollution/Portability


    Devel::PPPort::WriteFile();   # defaults to ./ppport.h


Perl's API has changed over time, gaining new features, new functions, increasing its flexibility, and reducing the impact on the C namespace environment (reduced pollution). The header file written by this module, typically ppport.h, attempts to bring some of the newer Perl API features to older versions of Perl, so that you can worry less about keeping track of old releases, but users can still reap the benefit.

Devel::PPPort contains a single function, called WriteFile. Its only purpose is to write the ppport.h C header file. This file contains a series of macros and, if explicitly requested, functions that allow XS modules to be built using older versions of Perl. Currently, Perl versions from __MIN_PERL__ to __MAX_PERL__ are supported.

This module is used by h2xs to write the file ppport.h.

Why use ppport.h?

You should use ppport.h in modern code so that your code will work with the widest range of Perl interpreters possible, without significant additional work.

You should attempt older code to fully use ppport.h, because the reduced pollution of newer Perl versions is an important thing. It's so important that the old polluting ways of original Perl modules will not be supported very far into the future, and your module will almost certainly break! By adapting to it now, you'll gain compatibility and a sense of having done the electronic ecology some good.

How to use ppport.h

Don't direct the users of your module to download Devel::PPPort. They are most probably no XS writers. Also, don't make ppport.h optional. Rather, just take the most recent copy of ppport.h that you can find (e.g. by generating it with the latest Devel::PPPort release from CPAN), copy it into your project, adjust your project to use it, and distribute the header along with your module.

Running ppport.h

But ppport.h is more than just a C header. It's also a Perl script that can check your source code. It will suggest hints and portability notes, and can even make suggestions on how to change your code. You can run it like any other Perl program:

    perl ppport.h [options] [files]

It also has embedded documentation, so you can use

    perldoc ppport.h

to find out more about how to use it.



WriteFile takes one optional argument. When called with one argument, it expects to be passed a filename. When called with no arguments, it defaults to the filename ppport.h.

The function returns a true value if the file was written successfully. Otherwise it returns a false value.


ppport.h supports Perl versions from __MIN_PERL__ to __MAX_PERL__ in threaded and non-threaded configurations.

Provided Perl compatibility API

The header file written by this module, typically ppport.h, provides access to the following elements of the Perl API that is not available in older Perl releases:


Perl API not supported by ppport.h

There is still a big part of the API not supported by ppport.h. Either because it doesn't make sense to back-port that part of the API, or simply because it hasn't been implemented yet. Patches welcome!

Here's a list of the currently unsupported API, and also the version of Perl below which it is unsupported:



If you find any bugs, Devel::PPPort doesn't seem to build on your system or any of its tests fail, please use the CPAN Request Tracker at to create a ticket for the module.



Version 3.x, Copyright (C) 2004-2010, Marcus Holland-Moritz.

Version 2.x, Copyright (C) 2001, Paul Marquess.

Version 1.x, Copyright (C) 1999, Kenneth Albanowski.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


See h2xs, ppport.h.

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