Re: Strange mix of SO version for libpari.so

[Bill Allombert <Bill.Allombert@math.u-bordeaux1.fr>]

On Sun, Dec 16, 2012 at 09:30:50AM +0100, Jan Engelhardt wrote:
> 
> On Friday 2012-11-30 11:55, Bill Allombert wrote:
> >On Fri, Nov 30, 2012 at 03:27:04AM +0100, Jan Engelhardt wrote:
> >> 
> >> Compiling pari-2.5.3 (the problem goes back to at least 2.5.0) produces 
> >> a libpari.so.2.5.3, but uses -Wl,-soname,libpari.so.3. What is the 
> >> reason that this obvious mismatch has been put into the Makefile?
> >
> >There is no mismatch: libpari.so.2.5.3 is the filename, and
> >libpari.so.3 is the SONAME. They do not have to be identical.
> >[...]
> >See this FAQ entry <http://pari.math.u-bordeaux.fr/faq.html#versionnum>
> >and especially the link
> ><http://pari.math.u-bordeaux.fr/archives/pari-dev-0206/msg00092.html>
> 
> Indeed they need not be; packaging pari for openSUSE merely raised
> eyebrows because the filename is non-standard.

If standard is defined by 'what would libtool do', then yes. Unfortunately,
a lot of developper misunderstand how libtool versioning works, and we get lots
of libraries with ridiculous versions, but 'standard' filenames. Hardly an
improvement.

> An overview:
> 
> (1.)
> The overwhelming majority of all distro-provided libraries one usually
> has installed in /usr/lib follows libfoo.so.x -> libfoo.so.x.y, not
> libfoo.so.x -> libfoo.so.2.(x/2+1).z.
> 
> So if pari followed common practice, it would just use
>  pari 2.5.0: libpari.so.3 -> libpari.so.3.0.0
>  pari 2.5.1: libpari.so.3 -> libpari.so.3.0.1
>  etc.

The assumption that the soname and the library version are related is very
unwise.

> (2.)
> Recognizing that there may exist some people who find using
> libpari.so.3.0.x for 2.5.x odd, unfitting or simply undesired,
> there is another way exercised:
> 
> 09:17 nakamura:/usr/lib64 > ls -log libasm* libdw* libelf*
> -rwxr-xr-x 1  31408 Jul 16 05:57 libasm-0.153.so
> lrwxrwxrwx 1     15 Sep 21 13:17 libasm.so.1 -> libasm-0.153.so
> -rwxr-xr-x 1 224576 Jul 16 05:57 libdw-0.153.so
> lrwxrwxrwx 1     14 Sep 21 13:18 libdw.so.1 -> libdw-0.153.so
> -rwxr-xr-x 1  84536 Jul 16 05:57 libelf-0.153.so
> lrwxrwxrwx 1     15 Sep 21 09:25 libelf.so.1 -> libelf-0.153.so
> 
> so the filename would be "libpari-2.5.3.so". (Using this name has
> a side-effect: using -lpari-2.5.3 becomes available. Whether that
> actually is useful, I don't know.)

Yes, this is confusing. The '*.so' namespace should be reserved to the API
symlink used by -l and should matching the header files.
Having the compiler seeing -lpari-2.5.3 as valid is actively harmful.
Someone might start to believe it is a good idea to use it without realizing
that the headers files used are for another major version.

Cheers,
Bill.