Re: transition: proposal libpt2.6.5->libpt2.6.6 & libopal3.6.6->libopal3.6.7

[Craig Southeren <craigs@postincrement.com>]

On 24/04/10 2:56 PM, Mark Purcell wrote:
> On Saturday 24 April 2010 13:26:20 Craig Southeren wrote:
>    
> > As one of the maintainers of the upstream (opal&  ptlib), please feel
> > free to email me if I can help
> >      
> Craig,
>
> Thanks for the offer.
>
> I do have one question/ request of upstream.
>
> Does the soname for ptlib/ opal need to change with every release?
>
> Generally this isn't considered best practise:
> http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html#AEN135
> http://www.netfort.gr.jp/~dancer/column/libpkg-guide/libpkg-guide.html#sonameapiabi
> http://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html
>
> Are subsequent minor versions of the libs really not binary (ABI) compatible?
>
> The problem for distributions is that every time the soname changes all depends of
> that library then need to be rebuilt and everyone needs to download all of the
> rebuilt binary packages.
>
> In contrast if the soname is only bumped when binary compatibility is broken then
> we only need to rebuild as necessary.
>
> In this particular case I wouldn't need to coordinate the transition from ptlib
> 2.6.5 ->  2.6.6 as I suspect they are binary compatible.
>
> Mark
>    
This issue is common with C++ libraries. The second part ofsSection 3.6 
of the following page (which you also reference above) does
a good job of describing the issues

http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html

Given these constraints, and with an API as rich and complex as Opal and 
PTLib, binary compatibility between revisions is not something we strive 
for.

However, we do try very hard to maintain source compatibility across 
minor revisions. An API change that would break comptibility in a big 
way is usually a trigger
for a new major revision.

I hope this gives some insight into our thinking

   Craig

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