Re: How to nicely distribute a simple Ada library?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sun, 4 Dec 2011 11:19:49 +0000 (UTC), Natasha Kerensikova wrote:

> I have found the packaging policies for Debian, which is very complete
> and useful, and for Fedora, which seems nice too but less interesting
> for upstream. And I would like to eventually maintain a FreeBSD port.

AFAIK, Ada on Fedora is maintained again. E.g. it has GtkAda 2.18 for gcc
4.6 which Debian still lacks.

> So my first question is, since the policies say to include in the
> package all the body and specification files required to compile
> something against the library, but not the others, how can I know which
> files are required and which are not?

You should maintain dependencies.

Your library under Linux would have at least two packages: binary and
developing dependant on different sets of packages.

> The policies also ask for a .gpr file used for building programs against
> the library, which seems different from the .gpr file used to build the
> library itself. Should I, as upstream, try to provide both of them, or
> should I leave the former .gpr file to the packager?

I used to generate the .gpr files for building my libraries. I wrote a
script which took the original .gpr file and patched it in order to produce
a build-gpr.

> I gather that packaging systems have their own way to perform the
> installation, but how can I provide an installation mechanism that does
> not depend on a distribution?

There is no one, AFAIK.

Fedora and Debian packaging systems is an utter mess. For my packages I
wrote a set of scripts generating the corresponding inputs for both
packaging systems. They have little in common. Furthermore, since GNAT
distributions on both systems suffer various problems (bugs), to overcome
them you might need workarounds, which then would depend on the target
system. (I stopped packaging my stuff until Linux distributions mature.
Presently I cannot compile much of it either under Fedora or under Debian.)

You should likely try to package your stuff manually first, in order to
understand the scale of the problem you are face. RPM (Fedora) is
considerable easier than Debian packager to start. IMO, packaging is as
twice harder than developing and testing a medium sized Ada library. You
should really consider if the adventure is worth the efforts...

> I would rather avoid automess tools, they
> feel extremely overkill compared to the simplicity and presumed
> portability of my libraries. I can write a `make install` in pure
> makefile language, but is there another more idiomatic way of doing it?

Well, but that is not the standard way how packages are distributed in
Linux.

I wrote a small tool to integrate a library into GNAT GPS without
packaging. But it is rather intended for custom libraries distributed in
sources. If you plan to distribute your library on "industrial scale", you
have to package it properly.

> What about windows or mac platforms?

For Windows you need to create an *.msi file. If you have a MS Developing
Studio, that is relatively simply to do, at least comparing to the
exercises needed for RPM and Debian packages.

> And while all the above assumes a GNAT toolchain, there are probably
> people using other compiles. I guess I cannot really support all Ada
> compilers that exist (especially those to which I don't have access), so
> the burden for porting the library to their toolchain is probably
> theirs, but is there any step I should to make it easier for them?

From a packaged library I would expect a full integration into GNAT GPS.
That means placing files on certain GNAT-specific locations depending on
the GNAT installation at hand.

OK, Linux does not really support GPS, or, for that matter, gprbuild
either. Under Debian there exists a GPS package, but it was not gcc 4.6,
last time I checked it.

> And lastly, is there anything else I should know to make my libraries
> easier to use for packagers and users?

1. Always provide gpr files. Whatever configuration you need should be done
using project variables.

2. Don't use any tools (e.g. make, autoconf, etc). Many nice Ada libraries
became unusable because in 2-3 years the makefile stopped working and
nobody knew how to fix it.

3. Don't use preprocessor! [Since AdaCore introduced it, there are troubles
installing Win32Ada]. If you need to tune the source, take the varying part
of it, make it a proper Ada package. Place two versions of this package
into separate subdirectories. Make a scenario variable to select the file
in the .gpr file.

4. Never set linker options using pragmas! Linker options belong to the
.gpr file.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de