LabVIEW
Deny Access function with invalid file refnum causes LabVIEW to crash
Hi folks,
I have LabVIEW 8.5, and today encountered something interesting that consistently causes LabVIEW to crash. Essentially, if you find the "Deny Access" function under the advanced file IO palette and wire up an invalid refnum, Windows (XP in my case) reports that LabVIEW has to close. I checked in task manager, and the LabVIEW process is still active and using a disproportionate amount of the CPU.
To reproduce the issue, simply drop the function on your block diagram, create a constant from the refnum input terminal, and run the VI. Has anyone else seen this behavior?
Thanks,
Jim
I have LabVIEW 8.5, and today encountered something interesting that consistently causes LabVIEW to crash. Essentially, if you find the "Deny Access" function under the advanced file IO palette and wire up an invalid refnum, Windows (XP in my case) reports that LabVIEW has to close. I checked in task manager, and the LabVIEW process is still active and using a disproportionate amount of the CPU.
To reproduce the issue, simply drop the function on your block diagram, create a constant from the refnum input terminal, and run the VI. Has anyone else seen this behavior?
Thanks,
Jim
LabVIEW user groep 
Hi Carla,
I'm glad to help, and thanks for looking into it. The way I ran into the bug was while I was working on an action engine VI to log certain text values (see attached picture). While logging, I didn't want other programs to access the file. When a new file had to be generated, I wanted to stop denying access and close the reference. However, if the value on the shift register was invalid, LabVIEW crashed instead of throwing an error (I guess a crash qualifies as an error).
If you look at the attached picture, my workaround was to use the "Not A Number/Path/Refnum?" function. If the reference is bad, I don't try to use the "Deny Access" funtion or close the file. That worked just fine and seems like a good solution for now.
Jim
I'm glad to help, and thanks for looking into it. The way I ran into the bug was while I was working on an action engine VI to log certain text values (see attached picture). While logging, I didn't want other programs to access the file. When a new file had to be generated, I wanted to stop denying access and close the reference. However, if the value on the shift register was invalid, LabVIEW crashed instead of throwing an error (I guess a crash qualifies as an error).
If you look at the attached picture, my workaround was to use the "Not A Number/Path/Refnum?" function. If the reference is bad, I don't try to use the "Deny Access" funtion or close the file. That worked just fine and seems like a good solution for now.
Jim
