NI has established "user" error code ranges:
-8999 through -8000
5000 through 9999
500,000 through 599,999.
Unfortunately, I can't count the number of "error 5xxx" constants that I've seen. We should stop that; it leads to confusion at best.
In an ideal world every developer or organization would have their own reserved error code ranges, but I accept that's not reasonable. That said, has anyone considered creating an informal list that organizations/individuals can publish their preferred error code ranges in? I think it might be useful. For example, if I'm at Company X and I see Company Y likes to use the range 501,000 to 501,999 then I'd probably choose not to use that range to avoid potential confusion to some extent.
It wouldn't be fail-safe or enforceable, but I think it would be valuable; is anyone else on board with the idea? If so, we'd need to decide on where to publish them, but the LabVIEW Wiki would be one obvious choice in my opinion.