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Alien-Libarchive-Installer-0.08_06
River stage zero No dependents
/ Alien::Install

NAME

Alien::Install - Install your aliens

VERSION

version 0.08_06

DESCRIPTION

NOTE: This is a work in progress. Everything here is subject to change until it gets released to CPAN (and to a lesser extent after as well).

I'm working on abstracting out all the generic bits out of Alien::Libarchive::Installer to eventually make a Alien::Install distribution. For a few development releases, Alien::Install and other modules under it will be bundled with Alien::Libarchive::Installer. The next production release of Alien::Libarchive::Installer will not have this code bundled with it.

WHY

This distribution is intended as an alternative to Alien::Base as a framework to write Alien modules. Alien modules are intended for specifying dependencies in CPAN for things which are not native to CPAN, such as C libraries. They should either find existing system libraries that fit their specification or download and build the libraries from the internet.

Alien::Base was intended as a framework to make it easier to write Alien modules. When I used Alien::Base to write my first implementation of Alien::Libarchive all seemed well. It worked well with Linux. Then I discovered a number of corner cases, and because I wanted it to work in various environments I ended up having to subclass a lot. In the end I felt like I was writing more work arounds than I was actually using Alien::Base itself. Listed here are some of the problems that I had with Alien::Base.

For this discussion,

libfoo

Is a C library that may be available from your operating system vendor, or it may be downloaded and installed from the Internet.

Alien::Foo

Is an Alien::Base module that makes libfoo available. In some discussions, Alien::Foo may use Alien::Install instead.

Foo::XS

Is an XS module that uses Alien::Foo to determine the compiler and linker flags for libfoo.

Foo::FFI

Is a FFI module that uses Alien::Foo to find the dynamic libraries for libfoo.

No way to force building from source

Alien::Base provides no provision for forcing it to download the source for the target library, even if the system library is available. This can be a problem if the system is very old, has bugs or security issues.

No way to specify specific version

Alien::Base provides no provision requesting a specific version. That means if Alien::Foo decides to use the system libfoo which is version 1.00, but you really need libfoo version 2.00 then you are out of luck.

If Alien::Foo was installed a long time ago from source when the latest version was 1.00 you are also out of luck.

No way to upgrade without reinstalling

Related to the last point, if Alien::Foo is building libfoo from source, there is no way to upgrade libfoo unless you force a reinstall of Alien::Foo, or if the author of Alien::Foo uploads a new version and you specify that newer version.

Fragile upgrades

Because Alien::Base builds and links against shared libraries you need to use Alien::Foo during the runtime of Foo::XS which uses it. In addition, upgrades become extremely fragile. Installing the system version of libfoo after Alien::Foo or upgrading Alien::Foo can break already installed and previously working versions of Foo::XS.

Some of the issues were discussed, but not acted on in this thread:

https://github.com/Perl5-Alien/Alien-Base/pull/30

Depends on pkg-config for system libraries

pkg-config is a common tool for getting the compiler and linker flags for a library. Though common, it is certainly not ubiquitous. Many systems to not come with it installed by default, it is rarely available under Windows. Even if it is available for your platform, many packages do not provide a .pc file which contains the information necessary to use pkg-config.

Some packages provide a .pc file on some platforms but not others. libarchive, for example, provides a libarchive.pc on most platforms, but not on FreeBSD, where libarchive is considered part of the operating system.

Does not work with Windows with dynamic libraries

When using Alien::Base to alienize a libfoo that uses autoconf for windows you have to do a lot of work yourself. Briefly, the problem is that on MSWin32 you need MSYS (my solution was to create Alien::MSYS), and on both MSWin32 and cygwin the DLLs need to be added to the path used by DynaLoader. The problem is that on both MSWin32 and cygwin, the DLLs are in the PATH, not the lib directory.

I was told that this was not necessary and was pointed to two examples that do not work on MSWin32 or cygwin. Also both examples do not use produce dynamic libraries on MSWin32.

https://github.com/Perl5-Alien/Alien-Base/pull/32

AUTHOR

Graham Ollis <plicease@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2014 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.