Re: Document reasonable portability targets

[Paul Eggert]

Thanks, Bruno.

The change to gnulib.texi looks good, but my kneejerk reaction to the
proposed change to gnulib-intro.texi is that although much of what's
proposed is useful, it divides software into categories pretty strictly
and this strictness might cause confusion and problems.  For example,
I test gnulib code on Solaris more often than every six months, so in
that sense Solaris is more important than what its "major" listing
would imply.  Conversely, some free software is maintained for more
than three years after release by organizations like Red Hat and
Ubuntu.  Overally I suspect it'd be better to keep support levels a little
fuzzy, and not to try to define terms like "essential" and "minor".

Instead, how about something like the following:

@node Target Platforms
@section Target Platforms

Gnulib works on a number of platforms that we call the "reasonable
portability targets".

GNU platforms, such as glibc, have the highest priority.  Next come
other free-software platforms, such as Cygwin and FreeBSD.  Then come
proprietary platforms that fit well in the Unix/POSIX tradition, such
as MacOS X and Solaris.  Then other proprietary platforms that are a bit
of a stretch, such as mingw.  And last comes proprietary platforms
that would be so much of a distraction to support that Gnulib
deliberately does not support them, such as MS-DOS.

Once the original distributor of a platform version stops supporting it,
it is typically no longer important to Gnulib as well.  However,
already-existing Gnulib code for now-obsolete platform versions is
typically left in place unless it would significantly impede
maintenance on modern platforms.

The exact set of platforms and platform versions, and their level of
support, is open to judgment and depends on how much work developers
are willing and able to contribute.  Volunteers to help support
other platforms are welcome, but should keep in mind that Gnulib's
goal is to support production applications, not computer museum
pieces or software research projects.

Here is a list of platform versions, written in 2011, that indicates
a reasonable set of priorities for Gnulib:

[at this point insert the list of platforms from Bruno's email,
starting with glibc systems]