And what's the value in the RDB$MECHANISM column in the
RDB$FUNCTION_ARGUMENTS table? 2?

--
Martijn Tonies
InterBase Workbench - the developer tool for InterBase and Firebird
http://www.interbaseworkbench.com

Upscene Productions
http://www.upscene.com

"This is an object-oriented system.
If we change anything, the users object."



"Doug Chamberlin" <dchamberlin@...> wrote in message
news:4.3.2.7.2.20010904175236.020b6540@......

> At 9/4/2001 04:25 PM (Tuesday), Martijn Tonies wrote:
> > > > where can I find information about UDFs arguments 'by descriptor'?
>
> "By Descriptor" is an alternative method of passing an argument to a
> function. Where "by reference" passes a pointer to the argument and "by
> value" passes the argument value itself (usually on the stack or in a
> register) "by descriptor" passes a pointer to a descriptor block in

memory.

> The descriptor block usually contains a type identifier, a value or

pointer

> to a value, and any other useful info. In this case the "other useful

info"

> would be a NULL flag.
>
> I first encountered descriptors in VMS where, IIRC, they were often used
> for passing strings. The descriptor held the buffer size of a string

buffer

> as well as the "used size". This was often more useful than passing a
> pointer to a char array (a la C) since the called function could safely
> utilize the string buffer as it needed without having to treat the

incoming

> string as readonly.
>
> If we had a standard descriptor definition and FB could be told to pass
> arguments to UDFs using it then the UDFs could detect NULLs being passed.
> This would be a big improvement! If UDFs could also return values via
> descriptors they could return NULL states as well.
>
>
>
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