Submitted by: @pcisar

Votes: 2

SFID: 807992#⁠
Submitted By: pcisar

To be really useful and not a nuisance as they are
now, some descriptor based udfs (like *nvl) should be
able to report a compatible data type and the engine
should check and accept the conversion if possible or
otherwise complain. Example:

invl takes two integers. It should be used with
integers. There's another int64nvl that works with
int64 quantities and returns int64. If the user misses
the right input parameter type, trash is returned:

SQL> select i64nvl(1,1) from rdb$database;

           I64NVL

=====================
2012179293274113

It happens because the engine assumes the return
descriptor costains a pointer to an int64 and doesn't
check the returned descriptor and in this case, the
values passed are integers. Hence, a developer
currently should check the precision of a numeric
argument or do explicit casts to avoid those traps.
Ideally, the engine should inspect the return
descriptor and see if it can be converted to the
declared UDF's return type, otherwise raise an
exception. In this case, an int can be safely
converted to a greater type, int64.

Also, the current behavior that may result from mixing
a return value by descriptor and FREE_IT is undefined.
What should the engine deallocate, the value, the DSC
or both?