Re: Bug#686777: netjack2 + opus custom modes + debian

On Mon, Jul 01, 2013 at 04:40:19PM +0200, Adrian Knoth wrote:
> On 06/30/2013 03:11 AM, Ron wrote:
> 
> Hi!
> 
> I'll limit my response to the aspect of symbols, since Robin has already
> answered the other questions.
> 
> 
> >> Just sketching now:
> >>
> >> libopus0 will provide /usr/lib/libopus.so.0 (business as usual)
> >> libopus-custom-0 will provide /usr/lib/libopus-custom.so.0
> > 
> > The big problem with this is that both of those will provide all of
> > the functions that libopus.so.0 does, only some of the symbols with
> > the same names will have different implementations in the -custom one.
> > 
> > Which means that when jack links to -custom, and jill links to -vanilla,
> > and then some high level audio app or desktop environment or whatever
> > links to both jack and jill ...   hilarity is likely to ensue.
> 
> I've seen colliding symbols with ardour via indirect linking, and it's
> really a PITA to diagnose.
> 
> But here it seems to be very unlikely: only the jack server links
> against libopus(-custom), and this server is a standalone binary that's
> not linking or linked to anything else.
> 
> All the clients link against libjack, and even if they do link against
> libopus, they're not interfering with the server's libopus-custom, since
> client-server communication is done via /dev/shm.
> 
> So I think we can ignore the symbol aspect for all practical cases.
> (Correct me if I'm wrong).

Where does libjacknet.so.0.1.0 fit into all of that?

I don't think we can guarantee that for the forever future something
using the custom modified symbols would be compatible with the normal
builds.  Optimisation work is really only just beginning, and there
are quite a few places where the normal code might diverge in newly
incompatible ways from what is possible when custom is enabled, and
where a symbol collision could be even worse than it is at present.

This could turn into a snowball of ugly pretty easily I fear ...

Which is why I'm really keen to be sure we're not going down this
path for something so tiny that nobody will ever be able to hear it.

  Cheers,
  Ron

1372695106.6347_0.ltw:2,a <20130701161138.GN14785 at audi dot shelbyville dot oz>