Symbol versioning

[Stefan (metze) Metzmacher]

Hi Jerry,

>> I discussed that again with Volker, Karolin and Michael
>> again and added it, but I also added a --enable-symbol-versioning
>> which defaults to yes if gnu ld is used.
> 
> Metze, these off list discussion to decide things are not good.
> No offense.  I know you all work together in the same office, but....

Yes, you're absolutely right.

>> We can still use a different way and update the library version
>> and have compat libraries to handle updates
> 
> So now we have two different mechanisms to maintain.  Wonderful.

The things I would like to have are these:

- Make it possible to use an old smbd with a newer winbindd
- Make it possible to use a new smbd against an older winbindd

Using symbol versioning makes that easy, as the binary always
links against the same library soname. So a new smbd would still
load with an old libwbclient, because the soname of the new library
is the same and smbd only uses functions of the old interface
and has references to the old versioned symbols only.
Other tools like wbinfo would not be able to load with an old
library as it will also have references to new functions.

But as we've currently symbol versioning only when using gnu ld
it's not available on every platform we support.

We could also work with compat libraries (as you proposed, but)
in both directions, one compat library that provides the old interfaces
against a new library and also a library that provides the new interface
against an old library implementing the new functions as stubs
returning WBC_ERR_NOT_IMPLEMENTED.

I'm currently doing some testing with compat libraries and
they may have also some portability problems, I'll continue
some testing tomorrow and will come back with the results then.

If the compat libraries support all we need, we can think about
removing symbol versioning and create a rc2 release...ok?

metze

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