If I attempt to use the rtrim udf multiple times in the same
statement as in
this example

select rtrim(rr.rdb$owner_name),
rtrim(rr.rdb$relation_name)
from rdb$relations rr
where rr.rdb$system_flag = 0;

then I will get this error

Invalid token.
invalid request BLR at offset 31.
Implementation limit exceeded.
block size exceeds implementation restriction.

It will work if one of the "rtrim" references is removed.

Here is my udf registration

declare external function rtrim cstring(32767)
returns cstring(32767) free_it entry_point 'IB_UDF_rtrim'
module_name 'ib_udf';

Is this by design?

Thanks.