Problem: When an error occurs inside some DAQmx VIs, the error source (the string component of the error cluster) does not contain the call chain. This means that it is impossible to know the location where the error occurred based on looking at the error message.
Real-world example: The other day I encountered DAQmx error -200477 on a cRIO-9045 that uses DAQmx to acquire data from several different C-Series modules. The real-time application that was running on the cRIO contained an error handling module, which correctly logged the error to file. I saw the following when using PuTTY and the linux 'cat' command to display the contents of the error log file.
Notice that the error message does not contain any information as to where in the codebase this error actually occurred. This meant that I had to spend a few minutes inspecting the moderately large codebase before identifying the likely location of the error. Running subsequent tests I was able to confirm that that was the location of the error. The error was soon understood and fixed.
Root-cause: The root-cause of the issue (lack of call chain information) is the DAQmx Fill In Error Info.vi. In the real-world example above the error was occurring inside the DAQmx Timing (Sample Clock).vi.
The block diagram of this VI is seen below:
Any LabVIEW errors generated inside that VI are generated by the DAQmx Fill In Error Info.vi. This VI is, of course, essentially a simple translator between the return type (I32) output of the Call Library Function Node and a native LabVIEW error. That VI has an unwired input named depth whose default value is 1. This means that only the last link of the call chain is inserted into the error message.
Solution: Always insert the complete call chain inside all DAQmx error messages.
