Re: Interfacing between Ada and C: records and structs

[Shark8 <onewingedshark@gmail.com>]

> Digging into the POSIX module:
> 
> 
> 
> private
> 
>   type Dummy is tagged null record;
> 
>   type Mutex is record
> 
>     Mutex : aliased POSIX.C.pthread_mutex_t;
> 
>     D : Dummy;
> 
>   end record
> 
> 
> 
> > 
> 
> > Have you checked that in Ada, pthread_mutex_t'Size is 192?
> 
> > 
> 
> 
> 
> In the POSIX.C package:
> 
> ALIGNMENT : constant := Natural'Min(Standard'Maximum_Alignment, 8);
> 
> type pthread_mutex_t'Alignment use ALIGNMENT;
> 
> type pthread_mutex_t'Size use 192;
> 
> 
> 
> However, when I write a simple test program I get 256 bits from 'Size, I'm not sure why...

Try adding Pragma Pack( DATA_STRUCTURE ); to the record.