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From: "Nick Roberts" <nick.roberts@acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Conditional compilation in Ada?
Date: Tue, 16 Nov 2004 20:41:18 -0000
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Date: 2004-11-16T20:41:18+00:00
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"Marius Amado Alves" <amado.alves@netcabo.pt> wrote in message 
news:mailman.103.1100630792.10401.comp.lang.ada@ada-france.org...
>> Any hints?
>
> Gnatprep.

In a little more detail, declare the things that differ (types, associated 
operations) in two separate packages, say Stuff_For_Playstation and 
Stuff_For_XBox, then put something like this:

Compile_Target := XBox

into a text file called "targspec.txt" (say), and then something like this 
in the appropriate places in your source files:

   with Stuff_For_$Compile_Target;
   ...
   package Target_Specific renames Stuff_For_$Compile_Target;
   ...
      Target_Specific.Reset_Joystick; -- or whatever

and rename every so doctored source file myfile.ads to myfile.adsp (and 
myfile.adb to myfile.adbp) and then run:

   gnatprep myfile.adsp myfile.ads targspec.txt -c -r

for each such source file, and then compile as normal. Documentation for 
gnatprep is in the GNAT User's Guide.

Obviously, you change "Compile_Target := XBox" to "Compile_Target := 
Playstation" to recompile for a different target.

The idea is to minimise the number of times you use a $ macro or #if in your 
source files, within reason, and put as much as possible into the different 
specific packages. Things tend to be easier to debug this way. You may find 
that you do not have to use gnatprep at all, but instead you could just have 
a separate file "target_specific.ads" which contains the two lines:

   with Stuff_For_XBox;
   package Target_Specific renames Stuff_For_XBox;

which you simply change to:


   with Stuff_For_Playstation;
   package Target_Specific renames Stuff_For_Playstation;

in order to recompile for a different target.

-- 
HTH
Nick Roberts