[Portaudio] pa_mac_core fails with non-duplex I+O on same device

Evan Balster evan at imitone.com
Thu Dec 15 23:50:09 EST 2016

Hey, all ---

I've noticed a defect in pa_mac_core which manifests when opening separate
input and output streams on the same device.  It appears to manifest as a
hang or deadlock, and I don't yet have a backtrace for it.  This does not
appear to affect duplex streams.

I suspect the root of the problem lies in the fact that both streams'
callbacks originate in the same thread (presumably belonging to the
driver).  This broke assumptions in my software and caused a crash relating
to thread-local variables.  After fixing my own application, I found that
pa_mac_core was still having sporadic lockups in Pa_OpenStream.

I've been aware of this for a while but wanted to mention it.  I'll
probably take some time to get a trace soon, when I have access to the
peripheral that lets me repro this.

– Evan Balster
creator of imitone <http://imitone.com>

P.S.  As of this month, I'm shipping my app with an increasingly intricate
series of error reporting systems.  In the long run, I'll probably be
getting minidumps from my users.  Failures in PortAudio under win32 are
numerous enough that I have a support page
<http://imitone.com/munity/viewtopic.php?pid=753#p753> offering alternative
builds, but in the future I hope to isolate and report the points of
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