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From: mheaney@ni.net (Matthew Heaney)
Subject: Re: pointers to unconstrained arrays
Date: 1997/11/16
Message-ID: <mheaney-ya023680001611972211100001@news.ni.net>#1/1
X-Deja-AN: 290062957
References: <346FC90F.3EEC@vsl.com.au>
Organization: Estormza Software
Newsgroups: comp.lang.ada
Date: 1997-11-16T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <346FC90F.3EEC@vsl.com.au>, Andrew Kelly <andrewk@vsl.com.au> wrote:

>procedure allocate_buffer (
>        low, high : in integer;
>        buffer_address : system.address;
>        buffer_ptr : out buffer_ptr_type) is

[snip]

>        -- return pointer to buffer     
>        buffer_ptr := buffer'access;
>end allocate_buffer;

You can't do this, and for a very good reason.  You're pointing to a
locally-declared buffer.

>
>
>
>-- unconstrained_array_ptr_test
>        my_buffer_ptr : buffer_ptr_type;
>
>begin 
>        allocate_buffer(1, 5, system.ItoA(16#B000#), my_buffer_ptr);

Why not do this

   Buffer : Buffer_Type (1 .. 5);
   for Buffer'Address use System.ItoA (16#B000#);
begin

and then refer to Buffer directly?  If you're going to call Allocate_Buffer
with hard-coded parameters, and declare a buffer access type to indirectly
refer to the buffer, you might as well just declare a buffer directly,
using the parameters you passed to the call.

--------------------------------------------------------------------
Matthew Heaney
Software Development Consultant
<mailto:matthew_heaney@acm.org>
(818) 985-1271