Re: ABI Compatibility (was Re: Installation woes for the average user...)

[Richard Frith-Macdonald]

On 20 May 2009, at 11:53, Yavor Doganov wrote:

> On Wed, May 20, 2009 at 11:24:39AM +0100, Richard Frith-Macdonald  
> wrote:
> > I think what you are describing (as the correct way to do things) is
> > what GNUstep already tries to do ... see
> > http://mediawiki.gnustep.org/index.php/GNUstep_release_policy for the
> > actual release policy details.
>
> On the contrary -- this very policy is the problem.
>
> The SONAME of a shared library should be bumped if and only if there  
> is
> ABI break, not because of publicity reasons, big API additions, or
> anything else.

That's a matter of opinion.  The GNUstep policy reserves the right to  
change the soname solely for publicity reasons, but afaik has never  
done so.  In practice pretty much all soname changes are related to  
ABI changes.

>  You can continue to version stable releases with even
> numbers and unstable releases with odd numbers and release them in any
> order you feel apropriate; the SONAME has absolutely nothing to do  
> with
> the package version.
>
> > > > How you version the releases and what is considered
> > > > "stable" and "unstable" is completely orthogonal to the library
> > > > versioning.
> >
> > is technically true, it's not what people expect in practice, and
> > therefor not policy.  The policy is to keep the main so version  
> > numbers
> > in sync with the main release version numbers, because that matches
> > normal expectations.
>
> Name just one library -- just one -- on your GNU system that behaves
> this way.

Hmm ... looks like you are right on that one ... I remember that user  
expectations were an argument years ago, back when the policy was  
originally formed, but perhaps that's changed (or perhaps it was never  
valid, just assumed).

> Consider what would happen if glibc or glib/gtk+ bump the
> soname every six months...  I find it incredibly hard to believe that
> this is "normal expectation".

Er ... frequency of release of binary incompatible code is a  
completely different issue from version numbering.

The fact is, most GNUstep libraries are still having to change.  Even  
the base library needs to break binary compatibility occasionally in  
order to improve MacOS-X compatibility.

> > However, I don't think there have been any recent releases which  
> > should
> > have changed the so number for any of the libraries.
>
> I've made an experiment some time ago by altering the symlinks without
> recompiling anything.  Every GNUstep app in Debian worked out of the  
> box
> (of course that's not a 100% proof that the new Base/GUI were ABI
> compatible).

I agree ... not even close to proof.

Most ABI changes are minor and won't effect most applications ... but  
we still need to change the soname because we don't know whether there  
are apps out there which will break.