BTY, I know you didn't printf your messages.... but pErrorRb leaks in your ARX version and don't release the result of acedGetArgs()
The point of the routine is so an application can get the error code and determine what to do next. Typical error handling. The calling application decides if it wants to print the string message to the screen. As far as finding the leak, thanks.
Well what we ought to, do is get feedback from the lisp community on how best to handle this. I'm kind of warming up to the last error call after I've seen how you did it.
Personally I don't think the methodology will matter to most customisers trying to access your libraries.
The important thing will be that it is documented .. somewhere other than the ARX source.
The quantum or errors I'd expect will be minimal
Most would be garbage in garbage out situations,
followed by user selection errors (ECS or ENTER misuse)
followed closely by assertion traps ( files, datatypes, range values, etc),
... allowing the user (calling function) to handle the error is critical ... the mechanism provided is just mechanics.