NAME

    Alien::Role::Dino - Experimental support for dynamic share Alien
    install

VERSION

    version 0.08

SYNOPSIS

    In your alienfile:

     use alienfile;
     
     share {
       ...
       plugin 'Gather::Dino';
     }

    Apply Alien::Role::Dino to your Alien::Base subclass:

     package Alien::libfoo;
     
     use base qw( Alien::Base );
     use Role::Tiny::With qw( with );
     
     with 'Alien::Role::Dino';
     
     1;

    And finally from the .pm side of your XS module:

     package Foo::XS;
     
     use Alien::libfoo;
     
     our $VERSION = '1.00';
     
     # Note caveat: your Alien is now a run-time
     # dependency of your XS module.
     Alien::libfoo->xs_load(__PACKAGE__, $VERSION);
     
     1;

DESCRIPTION

    Every now and then someone will ask me why thus and such Alien thing
    doesn't work with a dynamic library error. My usual response is can you
    make it work with static libraries? The reason for this is that
    building dynamic libraries for an Alien share install introduce a
    number of challenges, and honestly I don't see the point of using them,
    if you can avoid it. So far I haven't actually seen a situation where
    it couldn't be avoided. Just to be clear: dynamic libraries are fine
    for Alien, and in fact desirable when you are using the system provided
    libraries. You get the patches and security fixes supplied by your
    operating system.

    Okay, so why not build a dynamic library for a share install?

    For this discussion, say you have an alienized library Alien::libfoo
    and an XS module that uses it called Foo::XS (as illustrated in the
    synopsis above).

    Your Alien becomes a run-time dependency.

      When you link your Foo::XS module with a static library from
      Alien::libfoo it gets added into the DLL or .so file that the Perl
      toolchain produces. That means when you later use it, it doesn't need
      anything else. When you try to do the same thing with a dynamic
      library, you need that dynamic library, which is stored in a share
      directory of Alien::libfoo.

      For people who install out of CPAN this is probably not a big deal,
      but for operating system vendors (the people who integrate Perl
      modules into their operating system), it is a hassle because now you
      need this big build tool Alien::Build and the alien Alien::libfoo
      with extra dependencies during runtime. Normally you wouldn't need
      those packages installed for end-user use.

    Upgrades can and will break your XS module.

      Again, when Alien::libfoo builds a static library and it gets linked
      into a DLL or .so for Foo::XS, it doesn't need the original library
      anymore. If you are using a dynamic library and you do the same thing
      it maybe works today, but say tomorrow you upgrade Alien::libfoo and
      it replaces the DLL or .so file with an incompatible API or ABI? Now
      your Foo::XS module has stopped working!

    Dynamic libraries are not portable

      Dynamic libraries are widely supported on most modern operating
      systems, but each system provides a different interface. For example,
      Linux, Windows and OS X all have an environment variable that allows
      you to alter the search path for finding dynamic libraries, but all
      three have different extensions for dynamic libraries (OS X even has
      two!), the environment variables are called something different, and
      WHEN you can change them is different.

      The Perl core has code for loading dynamic libraries as part of its
      XS system on all platforms where you can build XS extensions
      dynamically. Unfortunately that code isn't quite reusable for use by
      Alien. Alien developers have limited time and access to many
      platforms, which means that many platforms will probably never get
      Alien support.

      Static libraries on the other hand pretty much work the same on all
      platforms. Even on Windows which likes to be different, static
      libraries are essentially the same as on Unix.

    So all that said, why have I written this module, which provides
    support for dynamic libraries? Well, maybe I am wrong, maybe it isn't
    that hard. Also, maybe you don't have a choice, maybe you have found a
    library that can ONLY be built using a dynamic library.

    What about you? Should you use this module? It has the worked
    Experimental in the description. The experimental aspect of this module
    should not worry you, because in the situation that your Alien finds
    the library from the system, nothing is different from the core
    Alien::Build. The only place it is different is if you have to do a
    share install, and hopefully you are only using it because you really
    can't build a static library. Thus you haven't really lost anything in
    stability, and at worst your Alien may work in places where it wouldn't
    otherwise.

    So in summary, the experimental aspect shouldn't worry you, the caveats
    above should!

HOW

    How does it work? Use the bundled alienfile plugin
    Alien::Build::Plugin::Gather::Dino. That will find any dynamic library
    paths in your share directory in case they are needed at runtime. Then
    apply this role to you Alien::Base subclass using Role::Tiny::With.
    Instead of using XSLoader or DynaLoader to load your XS module, use the
    xs_load from your Alien. Hopefully the synopsis above makes it clear.

ETYMOLOGY

    This module is named Dino being short for Dinosaur. I really like
    Dinosaurs (also friendly crocodiles and platypuses in case you hadn't
    noticed). "Dino" also has a similar sound to "Dyna" which is frequently
    used as a short name or prefix meaning "dynamic". I didn't want to call
    it "Dyna" or "Dynamic" since it is only building a dynamic library for
    share installs. I didn't want to call it DynaShare because that was
    getting a bit wordy. So Dino.

METHODS

 rpath

     my @dirs = $alien->rpath;

    Returns the list of directories that have non-system dynamic libraries
    in them. On some systems this is needed at compile time, on others it
    is needed at run time.

 xs_load

     $alien->xs_load($package, $version);
     $alien->xs_load($package, $version, @other_dino_aliens);

CAVEATS

    Lots. In summary:

    Your Alien is a run-time dependency and you will annoy system
    integrators

    Your XS can be broken by upgrades to your Alien

    Your platform may not be supported

    Also, this module should start with the caveat section and then go from
    there. Most modules I write are not like that.

    These platforms seem to work: Linux, OS X, Windows, Cygwin, FreeBSD,
    NetBSD, OpenBSD, Debian kFreeBSD.

    Currently has Alien::Autotools as a prerequisite. I hope to remove that
    prereq asap.

SEE ALSO

    alienfile

    Alien::Base

    Alien::Build

    Alien::Build::Plugin::Gather::Dino

AUTHOR

    Graham Ollis <plicease@cpan.org>

COPYRIGHT AND LICENSE

    This software is copyright (c) 2017-2022 by Graham Ollis.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

