Conditional compilation of debug traces without cpp

[guillaume.portail@grospied.enanglais.com]

Hi,

I have pieces of code like this (please just follow the general idea and 
forgive syntax errors) :

package Debug is
   procedure Put_Line (M : in String);
end;

package body Debug is
   Enabled : constant Boolean := False;
   procedure Put_Line (M : in String) is
   begin
     if Enabled then
       Real_Put_Line (M);
     end;
   end;
end;

Many other units, many calls like :
   ...
   Debug.Put_Line ("PC was here, A = ", A_Type'Image(A));  -- (1)
   ...

Debug.Enabled is a compile time constant, so with a bit of -O3 pragma 
Inline or other (-gnatN), the binary implementation of Debug.Put_Line 
will be null. But never will be the elaboration of the many calls to it. 
I guess that the elaboration of theses calls is always required by the 
language, think of :
   Debug.Put_Line ("PC was here, A = " & A_Function_Call(12));  -- (2)
   Debug.Put_Line ("PC was here, A = " & A_Function_Call(1/0)); -- (3)
For my need, A_Function_Call is only for debugging purpose here, it has 
no side effect (it is a function).

How may I organize the code to obtain the effect of having Debug.* calls 
being nulls when Debug.Enabled is False ?

For your information, this is easy using cpp :

#if _DEBUG
#define DEBUG(x)	real_put_line x
#else
#define DEBUG(x)	0
...
   if (foo)
   {
     a = something;
     DEBUG(("PC was here, A=%d", b()+a));
   }
   else
     DEBUG(("no foo"));
...

And I would like not to use cpp or gnatprep, etc.

What is the trick ?
--
Thierry Bernier