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From: Per Sandberg <per.sandberg@bredband.net>
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Newsgroups: comp.lang.ada
Subject: Re: conditionnal compilation
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NNTP-Posting-Date: Thu, 14 May 2009 05:14:16 UTC
Date: Thu, 14 May 2009 06:20:13 +0200
Xref: g2news2.google.com comp.lang.ada:5834
Date: 2009-05-14T06:20:13+02:00
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More on the above them when using GNAT project files:

When the number of target specific files is moderate:
--------------------------------------------------------------------
project my is
   -- Both the spec and body of My_Unit is target specific
   -- But i would recommend to keep the target specific parts
   --  as isolated as possible.
   type OS_Type is ("Windows_NT","Linux");
   OS : OS_Type := external("OS","Linux");
   package Naming is
     case OS is
       when "Linux" =>
          for Implementation("My.Unit") use "my-unit__Linux.adb";
          for Specification ("My.Unit") use "my-unit__Linux.ads";
       when "Windows_NT" =>
          for Implementation("My.Unit") use "my-unit__Win32.adb";
          for Specification ("My.Unit") use "my-unit__Win32.ads";
     end case;
   end Naming;
end my;
---------------------------------------------------------------------

When the number of target specific files is a bit larger:
--------------------------------------------------------------------
project my is
   -- The target specific files are kept in separate directories.
   type OS_Type is ("Windows_NT","Linux");
   OS : OS_Type := external("OS","Linux");
   for Source_Dirs use ("src");
     case OS is
       when "Linux" =>
          For Source_Dirs use project'Source_Dirs & ("src/Linux");
       when "Windows_NT" =>
          For Source_Dirs use project'Source_Dirs & ("src/Win32");
     end case;
end my;
--------------------------------------------------------------------

I would advice to one of the above schema's since they keep things 
understandable and try to stay with the first since Ada is usually is 
very portable.

But if conditional compilation is a requirement (in my opinion a very 
stupid one and this one is very compiler specific) you could read about 
it in:
  The GNAT users guide chapters:
    16. Preprocessing Using gnatprep
    3.2.17 Integrated Preprocessing	
The chapter references may not be 100% correct but anyway.

/Project files are an engineers best friend.
/Per


guerrier.cachalot@gmail.com wrote:
> Hi my friends
> Now that I know Ada has not built'in support for conditional
> compilation such a full-featured preprocessor, I would like know what
> should I use instead ?
> I precise I'm just a little beginner who doesn't want to compile
> anything .
> What really happend when I specify "--no-ssl" at some Ada-written
> program compilation ?