We use openroberta on several (old) laptops with lubuntu.
After the upgrade to 18.10 (cosmic) we could no longer compile programs for Calliope.
The server log reported a missing "cstddef" library.
After long research we found the following post:
With this information the following workaround helped for us:
We then start the server with this script:
Hope this post helps others with the same problem.