Work around a Windows crash (for now)

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

diff --git a/libs/ardour/session_ltc.cc b/libs/ardour/session_ltc.cc
index 8acb16dde30ea7f9247aac42958c45f36bbe0596..0cd365e1171714bac7beeb231ece48e6a8e67268 100644 (file)
--- a/libs/ardour/session_ltc.cc
+++ b/libs/ardour/session_ltc.cc
@@ -176,6 +176,21 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                return;
        }
 
+#if 1
+       /* Work around a race-condition on Windows/ PortAudio.
+        * It may happen that we do have a valid ltcport (created
+        * with the session), but no valid port-handle yet:
+        *
+        * Session > New implicitly closes old session and creates
+        * a new session directly after.
+        * re-registers ports fail? delayed? first proc callback only?
+        * reason is still unknown
+        */
+       if (!ltcport->port_handle ()) {
+               return;
+       }
+#endif
+
        /* marks buffer as not written */
        Buffer& buf (ltcport->get_buffer (nframes));