Re: Ada equivalent for C-pointer?

[Martin Krischik <martin@krischik.com>]

Pascal Obry wrote:

> 
> Nick Roberts <nick.roberts@acm.org> writes:
> 
>> For example, if there is a C function defined thus:
>> 
>>    int wibble(int *n);
>> 
>> then in Ada you can declare:
>> 
>>    function Wibble (Number: in out Interfaces.C.int);
>>    pragma Import(C,Wibble,"wibble");
>> 
>> and it should work. (Obviously, you must link the C functions in
>> somehow.)
> 
> I don't think so. Here Number will be passed by value, no? And you also
> need the returned value ;)

No all out and in out parameter are passed as pointer when pragma Import(C
is used - thats unless you use C_Pass_By_Copy. I have written quite a lot
of code interfaceing with C.

Read: 

http://en.wikibooks.org/wiki/Programming:Ada:Types:access#C_compatible_pointer

> So, you probably want:
> 
>     function Wibble (Number: access Interfaces.C.int) return
>     Interfaces.C.int; pragma Import(C,Wibble,"wibble");

No! you don't want that! You would need aliased data then!

Martin

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