[Jack-Devel] Shared memory and static variables

Hi,

I have not posted to this list before, but I am a long time user of
Jack. I'm also a developer, and I'm thinking about making a patch for
Jack, but I thought I would ask some opinions/advice from the Jack
developers first, particularly whether you would ever approve the patch
I'm thinking of.

The reasons for writing the patch are rather technical (it's not a new
feature, sorry!), so bear with me. I am the author of the Jack2DSSI
plugin wrapper (http://jack2dssi.sf.net/). It (ab)uses the Jack API (and
some private API) to create an internal Jack server, which it then wraps
in a DSSI plugin. This way, any Jack client can become a plugin.

Here is the problem: You cannot launch more than one instance of the
plugin. I *think* that the reason is that the shared memory structure
that Jack uses is pointed to by some global variables (registry_id and
registry_info), and this means that the second server will mess up the
pointers of the first server. It was probably never designed to run more
than one server in one process.

What I would like to do is to refactor some code in the shm.c file &
friends, so that it would not rely on these global variables. Most
likely this would involve adding some function parameters here and there
to pass the pointers on the stack, rather than as global variables; I
haven't worked out all the details yet.

Since this touches with the very heart of Jack's interprocess
communication mechanism, I won't be surprised if there is some
skepticism towards this change, especially since it (seemingly) only
benefits one application. On the other hand, removing global variables
is usually a good thing to do if one can.

So there you have it. I hope that made sense. My questions are:

1. Do you know of a strong reason that this should not be done? (e.g.
"breaking the API is unavoidable")

2. Do you think you'd approve a patch like that if it was written and
reviewed properly?


Cheers!

-- 
Kristian

1379443664.31035_0.ltw:2, <5238A3BF.3070204 at amlie dot name>