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From: "Matthew Heaney" <matthew_heaney@acm.org>
Subject: Re: Question about interfacing C and Ada95
Date: 1999/11/09
Message-ID: <3828affe_3@news1.prserv.net>#1/1
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Newsgroups: comp.lang.ada
Date: 1999-11-09T00:00:00+00:00
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The following Ada code works correctly with the C code you posted in 
your last message.

If you prefer to use functions (instead of procedures), in order to
return the Error_Code as the return value of the function, it's simple
enough to do that.


--STX
with Text_IO;       use Text_IO;
with Interfaces.C;  use Interfaces;
with System;

procedure get is

   type Access_Int_Type is access all C.Int;
   pragma Convention (C, Access_Int_Type);

   type Access_C_Float_Type is access all C.C_Float;
   pragma Convention (C, Access_C_Float_Type);

   type Instance_Type is access all System.Address;
   pragma Convention (C, Instance_Type);

   Error_Code : aliased C.Int;

   Instance : aliased System.Address;

   Val : aliased C.C_Float;

   procedure Create_Object
     (Instance   : in Instance_Type;
      Error_Code : in Access_Int_Type);

   pragma Import (C, Create_Object, "createObject");

   procedure Get_Float
     (Instance   : in Instance_Type;
      Val        : in Access_C_Float_Type;
      Error_Code : in Access_Int_Type);

   pragma Import (C, Get_Float, "getFloat");

begin -- get

   Create_Object (Instance'Access, Error_Code'Access);

   Put_Line (C.Int'Image (Error_Code));

   Get_Float (Instance'Access, Val'Access, Error_Code'Access);

   Put_Line (C.Int'Image (Error_Code));
   Put_Line (C.C_Float'Image (Val));

end get;