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From: aschwarz@acm.org (skidmarks)
Newsgroups: comp.lang.ada
Subject: Re: Conditional compilation in Ada?
Date: 23 Nov 2004 07:42:21 -0800
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Date: 2004-11-23T07:42:21-08:00
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> 
> 
> Package one body is
> 
> Debug_Flag  : Boolean := TRUE;  // Note: this is a variable
>                                  // and placed in the spec file.
> 
> function Is_Debug return Boolean is
> begin -- Is_Debug
>     return Debug_Flag;
> end Is_Debug;
> pragma inline( Is_Debug );
> 

Sorry. I just read the original post. The advantage of using constants
is that the compiler (should) remove the conditional branch which is
never executed, viz.

     Debug_Flag := constant Boolean := TRUE;

     if ( Debug_Flag ) then null; // always executed
                       else null; // never executed and the compiler
will
     end if;                      // remove the code

The function 'Is_Debug' with a pragma inline should have the same
effect.

Since the flag conditions the branch, it is possible to compile all
required code variants and select them at run-time by using a variable
flag instead of a constant. If you are willing to perform multiple
builds, then a constant flag achieves much the same effect as a C/C++
conditional compilation. And, of course, the Is_Debug is thrown in as
a 'plus'.

art