Exception in DAQmxCreateAIVoltageChan with DAQmx v7.4

Question

I have a C++ module whose purpose is to probe a user's system for available NI-DAQmx devices and their channels and ports. It used to work with the 7.1 driver set but now, with 7.4, it doesn't. Instead, when the channel name "/ai16" is passed to the DAQmxCreateAIVoltageChan function, it coughs up the following exception.
First-chance exception in [The process using my DLL.] (NIESXU.DLL): 0xC0000005: Access Violation.
This only occurs with strings on the type "/aiX" where X is any number outside the range of channels present. Complete nonsense names don't bother it, it just fails like you'd expect. I'm testing with a PCI-6014 at the moment that has only 15 AI channels so this used to just return the DAQmxErrorPhysicalChanDoesNotExist error that I trap to know when to stop counting. I catch the exception, of course, but I'd like it to not get thrown in the first place. What's happening with this now and can it be solved?
The relevant code section follows:
DAQmxCreateTask("Analog Input Counting", &taskHandle);
while(1)
str.Format("%s/ai%d", devices[i].name, devices[i].ai++);
status = DAQmxCreateAIVoltageChan(taskHandle, str, "", DAQmx_Val_Diff,
-10.0, 10.0, DAQmx_Val_Volts, NULL);
if(status != DAQmxErrorPhysicalChanDoesNotExist)
// Snipped for space. Fills out a large structure and updates a list.
else break;
devices[i].ai--;
DAQmxClearTask(taskHandle);

Answer 1

Hello,
I just ran some example code and called DAQmxCreateAIVoltageChan(taskHandle,"Dev4/ai16","",DAQmx_Val_Cfg_Default,-10.0,10.0,DAQmx_Val_Volts,NULL) with a PCI-6014 and NI-DAQ 7.4, and wasn't able to reproduce the DAQ exception. What happens if you try to call that function with the "Dev4/ai16" hard-coded?
Try running the example at: C:\Program Files\National Instruments\NI-DAQ\Examples\DAQmx ANSI C\Analog In\Measure Voltage\Acq-Int Clk. Modify the DAQmxCreateAIVoltageChan() function to "ai16" and see if the exception is still given.
If these steps still produce a DAQ Exception, try uninstalling and reinstalling DAQ.
Let me know if these steps do not help.
Regards,
Sean C.