Re: Interfacing to C: big structures

["Alex R. Mosteo" <amosteo@unizar.es>]

Robert A Duff wrote:
> "Alex R. Mosteo" <amosteo@unizar.es> writes:
> 
>> 2. Create an Ada type as
>>
>> type S is new Ada.Streams.Stream_Element_Array
>>                 (1 .. Stream_Offset (Size_Of_S));
>> pragma Pack (S); -- Not sure if this is even needed.
>>
>> Note that this type gets its size at elaboration time, and thus this is
>> what fixes this type if the C corresponding struct changes.
> 
> Nice trick.
> 
> But I think you need to make sure the alignment is correct.

I'm out of my expertise here, but why it's that necessary? In the end
you're passing S address to the C subprograms and I don't see how
alignment may have influence (but, again, I don't know about this).