[pulseaudio-discuss] PulseAudio autospawn fails on macOS 10.13 (High Sierra)

[René J.V. Bertin]

On Saturday April 07 2018 18:42:27 Tanu Kaskinen wrote:

Hi,

> I cc'd a few people who have contributed to PulseAudio's macOS support

I have a vague memory that PulseAudio has little to do on Mac, something I tend to agree with. I use a lot of FOSS applications but none that work only with PA, so while I have libpulse installed for dependency reasons, I do not have the pulseaudio daemon itself.
I also recall that back when I still did use PA for some applications, I had to launch the daemon manually.

I think there are several alternatives to look at
- get rid of all unsafe API calls between fork and exec; this is what we did with KDE's KInit framework for instance. I have not had any feedback (yet) that the result doesn't work on 10.13 .
  Why would PA need to call ObjC APIs while auto-spawning?
- The PA daemon can be launched manually so there's apparently no reason to spawn it with fork+exec; the system() call should do nicely too.
- Supposing that having a sound daemon is not a crucial aspect: integrate the actual sound playing functionality into libpulse on Mac.
- Use LaunchServices with a similar approach as used for the session D-Bus or even by XQuartz. These use a mechanism where the daemon (agent) is registered as an on-demand service which is accessible via a named socket. The socket name is published in an env. variable (DISPLAY for XQuartz), and launchd will start the daemon when an application connects to the socket. I don't know the exact details and to what extent it will be possible to use a self-determined socket name that is not exported via an env. variable but that shouldn't be too hard to find out (or adapt to, if indeed use of an env. variable is obligatory).

The LaunchServices approach is undoubtedly the cleanest solution, but I don't see anything wrong to using system() either.

> environment variables from libpulse (it's not thread-safe, and messing

If all else fails ... What is the chance that multiple threads would try to spawn the PA daemon at the same time? A mutex should make that impossible. There's of course the possibility that another thread would also be spawning or launching a child process and I understand that OBJC_DISABLE_INITIALIZE_FORK_SAFETY has to be set before calling fork() (so the exec() variants that take an environment argument aren't a solution) - there must be a way for a thread to preempt all others for a short duration?

I'd say have fun...

R