Re: C code to Ada

[Jeffrey Carter <jrcarter@acm.org>]

James S. Rogers wrote:
> I looked in the GNAT file i-cstrea.ads. It defines the following
> (just an excerpt from the file)
> 
>    subtype voids is System.Address;
>    --  Corresponds to the C type void*
> 
> It appears that you can correctly use System.Address on to
> bind to a C void*.

In C, "pointer" and "address" are used interchangeably, so you can 
generally use System.Address for any C pointer. You can also do 
something like

type Void_Ptr is access all Integer;
pragma Convention (C, Void_Ptr);

and use Void_Ptr for void*. Integer is just a placeholder; it doesn't 
matter what the type designates, since you're never going to dereference 
values of the type, just get them from and pass them to C functions 
(sort of like private types). This has the advantage that Void_Ptr has 
the form of a C pointer even if System.Address doesn't.

If you like things a little thicker, you can define

    type Handle is private;
private
    type Handle is access all Integer;
    pragma Convention (C, Handle);

and use Handle for void*.

-- 
Jeff Carter
"Nobody expects the Spanish Inquisition!"
Monty Python's Flying Circus