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From: "Jean-Pierre Rosen" <rosen.adalog@wanadoo.fr>
Subject: Re: ifdef replacement for GNAT
Date: 1998/04/14
Message-ID: <6gv6l3$73e$1@peuplier.wanadoo.fr>#1/1
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References: <352287EE.1CFB@tolstoy.mdc.com> <352B8208.41C6@tolstoy.mdc.com>
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Organization: Adalog
Newsgroups: comp.lang.ada
Date: 1998-04-14T00:00:00+00:00
List-Id: <comp.lang.ada>


Robert Dewar a �crit dans le message ...
>Dirk asks
>
><<How is an Ada project (GNAT) being kept portable among various Unices
>and say, Win32? Assume there is something special to be done in all
>environments. Without using a nonstandard tool like gnatprep that is.
>>>
>
>The Steelman requirements prohibited the inclusion of preprocessing in
>the Ada language, which may surprise you. What may surprise you more is
>that I and many others think this is a *good thing*.
>
>We provide gnatprep for our users, but we do NOT use it ourselves in
>the GNAT system.
>
>The proper approach for achieving target dependence is to follow two steps
>
>  (a) encapsulte the target dependence down to the minimum level
>
>  (b) Provide separate target dependent units for these remaining functions
>

Note that library packages renaming can be handy in managing this approach.
You define for example:

package My_Interface_Unix is...
package My_Interface_Win32 is...

and then:
with My_Interface_Win32;
package My_Interface renames My_Interface_Win32;

and use My_Interface all over the place.

If you change operating system, you only need to change the renaming in only
one place. Not more work than changing a #define.
--
----------------------------------------------------------------------------
                  J-P. Rosen (Rosen.Adalog@wanadoo.fr)
      Visit Adalog's web site at http://perso.wanadoo.fr/adalog