Re: Interfacing Ada with C

["Steve" <nospam_steved94@attbi.com>]

A different way of doing this:

In Ada you should be able to use Interfaces.C.Pointers and then declare your
procedure as follows:

  package Interface_Wide_String is
    new Interfaces.C.Pointers( Interfaces.C.size_T,
                               Interfaces.C.WChar_T,
                               Interfaces.C.WChar_Array,
                               Interfaces.C.Wide_Nul );

  procedure One( Name : in Interface_Wide_String.Pointer );
  pragma Export( C, One );


Within procedure "One" you can use:

    myName : Wide_String := Interfaces.C.To_Ada(
Interface_Wide_String.Value( Name ) );

If you need to look at the string as a wide string.

I haven't tested this, but I think it will work (it compiles anyway).

Steve
(The Duck)


"Paul Anderson" <notme@nowhere.com> wrote in message
news:3e9b28f8$1_4@newsfeed...
> Hi:
>
> I have a need to interface an Ada library with a C program.
> I am having trouble finding the best way to convert
> strings between the two worlds.
>
> I have a declaration:
>
>     procedure One(Name : in Wide_String);
>     pragma Export(C, One, "one");
>
> When I compile I get:
>
> foo.ads:29:42: warning: type of argument "One" is unconstrained array
> foo.ads:29:42: warning: foreign caller must pass bounds explicitly
>
> Fine, except how do I "pass bounds explicitly" when I call
> this function in C?  The prototype for this function in C
> would normally be:
>
>     void one(wide_string w);
>
> which doesn't have a slot for the bounds.  So where does it
> go?
>
> Alternatively, is there an different way of doing this that
> avoids this problem?
>
> I am using gnat-3.15p.
>
> Thanks,
>
> Paul.
>