It isn't 100% clear that we should use the list's data lock, but it seems quite likely
that this is the correct design, because of the interlock between data being present
and automation state
This would crash (throw) if ardour was started with an invalid backend
(alsa with no devices avaliable) and then changec to an alredy running
jack. The invalid backend at the start would leave the buffer
size combo empty and switching to the running jack backend did not populate
buffer size list.
We can't use Lua to construct a PBD::SystemExec Obejct. Lifetime of the
object is bound to the Lua interpreter or local function scope.
Destroying the C++ object terminates the process.
Additionally to adding a dedicated method, we also override the existing
os.execute Lua libary method with a rt-save (vfork, close filedescriptors)
wrapper.
Prepare for a method consistent with access_action():
* separate group + action names
* no action string parsing overhead.
* no fatal, abort () call for invalid actions
This hopefully fixes an issue with port-registration (new session)
being skipped because PortAudioBackend::available() still false
until the first callback.
The root-cause is likely PortAudio backend specific async
port-registration, re-establish ports after session creation and
after the first callback and it's apparently a race-condition:
crash is not 100% reproducible.
#10 0x00007ffb156df18a in msvcrt!abort () from C:\Windows\System32\msvcrt.dll
#11 0x0000000012597832 in _wassert (_Message=_Message@entry=0x2eaf96f0 L"_port_handle",
_File=0x2 <error: Cannot access memory at address 0x2>, _File@entry=0x346a1430 L"../libs/ardour/audio_port.cc",
_Line=80) at ../../mingw-w64-crt/misc/wassert.c:54
#12 0x00000000125978e8 in _assert (_Message=0x1282f7e9 "_port_handle",
_File=0x1282f7a0 "../libs/ardour/audio_port.cc", _Line=80) at ../../mingw-w64-crt/misc/wassert.c:30
#13 0x00000000120d1a51 in ARDOUR::AudioPort::get_audio_buffer (this=0x34a95a70, nframes=256)
at ../libs/ardour/audio_port.cc:80
#14 0x00000000126724f9 in ARDOUR::AudioPort::get_buffer (this=<optimized out>, nframes=<optimized out>)
at ../libs/ardour/ardour/audio_port.h:43
#15 0x0000000012435421 in ARDOUR::Session::ltc_tx_send_time_code_for_cycle (this=this@entry=0x37666310,
start_frame=0, end_frame=end_frame@entry=256, target_speed=0, current_speed=0, nframes=nframes@entry=256)
at ../libs/ardour/session_ltc.cc:180
#16 0x000000001245209f in ARDOUR::Session::no_roll (this=this@entry=0x37666310, nframes=256)
at ../libs/ardour/session_process.cc:145
#17 0x0000000012453051 in ARDOUR::Session::fail_roll (this=this@entry=0x37666310, nframes=<optimized out>)
at ../libs/ardour/session_process.cc:128
#18 0x0000000012459ebd in ARDOUR::Session::process_without_events (this=this@entry=0x37666310,
nframes=nframes@entry=256) at ../libs/ardour/session_process.cc:897
#19 0x000000001245a462 in ARDOUR::Session::process_with_events (this=0x37666310, nframes=256)
at ../libs/ardour/session_process.cc:425
#20 0x0000000012451bc5 in ARDOUR::Session::process (this=0x37666310, nframes=nframes@entry=256)
at ../libs/ardour/session_process.cc:78
#21 0x00000000120e79fd in ARDOUR::AudioEngine::process_callback (this=0x23316e30, nframes=256)
at ../libs/ardour/audioengine.cc:376
#22 0x00000000285390fe in ARDOUR::PortAudioBackend::blocking_process_main (this=this@entry=0x29e67750,
interleaved_input_data=interleaved_input_data@entry=0x115e8790,
interleaved_output_data=interleaved_output_data@entry=0x115e0050)
at ../libs/backends/portaudio/portaudio_backend.cc:1962
#23 0x0000000028539b75 in ARDOUR::PortAudioBackend::process_callback (this=this@entry=0x29e67750, input=0x115e8790,
output=0x115e0050, frame_count=<optimized out>, timeInfo=0x3d17fd70, statusFlags=statusFlags@entry=0)
at ../libs/backends/portaudio/portaudio_backend.cc:775
#24 0x0000000028539c16 in ARDOUR::PortAudioBackend::portaudio_callback (input=<optimized out>,
output=<optimized out>, frame_count=<optimized out>, time_info=<optimized out>, status_flags=0,
user_data=0x29e67750) at ../libs/backends/portaudio/portaudio_backend.cc:721
#25 0x00000000632c528f in NonAdaptingProcess () from C:\Program Files\Mixbus32C-4\bin\libportaudio-2.dll
#26 0x00000000632c73b2 in PaUtil_EndBufferProcessing () from C:\Program Files\Mixbus32C-4\bin\libportaudio-2.dll
#27 0x00000000632d129c in ProcessingThreadProc () from C:\Program Files\Mixbus32C-4\bin\libportaudio-2.dll
