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Path: utzoo!attcan!uunet!husc6!think!ames!ncar!noao!nud!mcdchg!clyde!rjs@moss.ATT.COM
From: rjs@moss.ATT.COM
Newsgroups: comp.lang.ada
Subject: Re: Conditional compilation
Message-ID: <28255@clyde.ATT.COM>
Date: 17 Jun 88 14:48:27 GMT
References: <909*haug@vax.runit.unit.uninett>
Sender: nuucp@clyde.ATT.COM
Reply-To: rjs@moss.UUCP (Robert Snyder)
Organization: AT&T Bell Laboratories, Whippany NJ
List-Id: <comp.lang.ada>

In article <909*haug@vax.runit.unit.uninett>
haug%vax.runit.unit.uninett@TOR.NTA.NO (Steinar Haug) asks:
>I'm developing programs for both DEC VAX (VAX/VMS Ada compiler) and
>SUN-3 (Alsys Ada compiler). I need to use some form of conditional
>compilation.
>
>The LRM contains a reference [10.6] to conditional compilation but
>it seems rather cryptic and it is not obvious to me how I could use
>it in practice.
>
This seems to be the type of mechansim that 10.6 is referring to:

-- At the beginning of your source, or in a separate package that you
-- include in any module that needs to conditionally compile based on
-- the target, make the following declarations.

type MACHINE_NAME is (VAX, SUN3);
TARGET : constant MACHINE_NAME := VAX;  -- Change this line to compile
                                          -- for a different target


-- Then wherever you need to conditionally compile code based on the 
-- target machine, use the following:

case TARGET is
  when VAX =>
	-- VAX specific code goes here.
  when SUN3 =>
	-- SUN-3 specific code goes here.
end case;


Of course this solution assumes that you can put all your conditional
stuff in a case statement.  The compiler is allowed to not generate any
of the code for the obviously FALSE case.
Good Luck.

	Robert Snyder
	{ihnp4|clyde}!moss!rjs
	(201) 386-4467
The above statements are my own thoughts and observations and are not
intended to represent my employer's position on the subject(s).