Creating PV on uninitialized waveform record fails in ca.py

[rokstefanic]

Set-up:

• IOC with a waveform record (name WF_SP) in the db: record(waveform, "WF_SP") { field(DESC, "Sequence") field(FTVL, "LONG") field(NELM, "10") }
• no operation is done on the waveform after the IOC starts so it is totally uninitialized

Issue description:

When creating a PV as the following: pv1= PV(pvname = 'WF_SP', callback = onChanges, auto_monitor=True, form='ctrl');

The following error is reported and callback is not called: Traceback (most recent call last): File "_ctypes/callbacks.c", line 314, in 'calling callback function' File "/usr/local/lib/python2.7/dist-packages/pyepics-3.2.1-py2.7.egg/epics/ca.py", line 436, in _onMonitorEvent tmpv = value[0] IndexError: invalid index

This means that callback should be called with no value(?) and count set to 0(?), but one could still use other information from other callback arguments and kwargs.

The same issue does not happen when this is done on an uninitialized longout record (I guess this is true also for other types)

Best Regards, Rok

[rokstefanic]

I am sorry for mixing the repo - the issue was meant for pyepics repository and not epicapp.

I am sorry again.