[fpc-pascal] Empty record inside another record ?

[Daniël Mantione]

Op Fri, 15 Feb 2008, schreef Skybuck Flying:

> To me it seems like some kind of trick, to extend a record at runtime.
>
> The empty record field, functions as a sort of offset/label/pointer if you 
> will to the new fields that will will be extended to the record by simply 
> allocating more memory then the size of the record.
>
> Then this "label"/"field" can be used as a sort of offset, by typecasting it 
> to some extension record type.
>
> Could be pretty handy, quite impressive trick.
>
> However, is it safe to use ?

Empty records are valid Pascal.

> I cannot find anything in the documentation about this ?

Nothing in the documentation says it is forbidden either. The reason 
it is not explicetely mentioned is because there exists a 
much better method, objects:

type  base_structure=object
         field1:byte;
       end;

       extended_structure=object(base_structure)
         field2:byte;
       end;

Daniël