From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID,XPRIO
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,8a3d369650eccae6,start
X-Google-Attributes: gid103376,public
From: "Deepak Haste" <deepak@teamqsi.com>
Subject: Interface with C
Date: 1999/05/20
Message-ID: <7i1n9t$6fs@beast.connix.com>#1/1
X-Deja-AN: 480235679
X-Priority: 3
X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300
Organization: Connix Internet
X-MSMail-Priority: Normal
Newsgroups: comp.lang.ada
Date: 1999-05-20T00:00:00+00:00
List-Id: <comp.lang.ada>

Hello,

I am implementing an ADA routine that interfaces with a Win32 C-library on
an NT. I am trying to import an array into an ADA procedure from a
C -function call.

The C function looks like this

 > DllImport int GetKnownBadComponents_RT(int **bad_components,  ...);

A call to this function would give us the address of the array.

****************************************************************************
***
The corresponding ADA binding looks like this :

 >  type components is array(Integer range <>) of Integer;

------------------------------------------------
>   pragma convention(C,components);
------------------------------------------------

 >  type components_ptr is access components;

 >  function GetKnownBadComponents_RT(bad_components_ptr : in
components_ptr; ..) return Integer;
                                                                           -
- function prototype

****************************************************************************
*
While calling this function from an ada procedure I do:

 >     badcomponents_ptr : components_ptr := new components(0 .. 9);
                                                                           -
- initialized to point to a 10 component array

 >     ret_code := GetKnownBadComponents_RT(badcomponents_ptr,...);
                                                                           -
- the actual function call

 >     for Item in badcomponents_ptr.all'range loop
 >           Put(Integer'Image(badcomponents_ptr.all(Item)));
 >     end loop;
                                                                           -
- display array elements

****************************************************************************
*

Now, I know that the C function does not pass array of size greater than 5.
Also, the inclusion/exclusion of the pragma convention makes it behave
differently. When pragma is excluded, the procedure gives constraint error
at the function call. When included, I get the first element correctly.
However the display loop goes infinite giving out the rest as garbage. Any
suggestions will be greatly appreciated.

Thanks,
Deepak Haste.