Thanks for the information, Ivan. This is pretty disturbing news. As
you've no doubt gleaned from my original post, I want the UDF to
return the binary of a GUID, hence the RETURNS CHAR(16) CHARACTER SET
OCTETS. I'm really not sure about using CSTRING. The last thing I
want Firebird to do is treat the return value as a null-terminated
string in the default character set for the database in question. Do
you have any word on whether Firebird does (or might do) this? Do you
have any further information on the bug you mention? If there's any
chance now or in the future that Firebird will take such liberties,
then I will scrap any idea of creating UDF's that return binary (at
least until this CHAR/VARCHAR failure is fixed).

Awaiting your reply,
Marc Benedict.