Re: Elaboration order handling (Was: Bug in 'gnatmake')

[Adam Beneschan <adam@irvine.com>]

On Wednesday, June 19, 2013 6:09:24 PM UTC-7, Jeffrey Carter wrote:
> Since we're discussing elaboration order, there's a case that I wonder about:
> 
> with B;
> 
> package A is
>     function F (I : Integer) return B.Thing;
> 
>     function R return Integer;
> end A;
> 
> package body A is
>     function F (I : Integer) return B.Thing is
>        -- null;
>     begin -- F
>        return B.To_Thing (I);
>     end F;
> 
>     function R return Integer is
>        -- null;
>     begin -- R
>        return 7;
>     end R;
> 
> end A;
> 
> package B is
>     type Thing is private;
> 
>     function To_Thing (I : Integer) return Thing;
> private -- B
>     type Thing is new Integer;
> end B;
> 
> with A;
> 
> package body B is
>     function To_Thing (I : Integer) return Thing is
>        -- null;
>     begin -- To_Thing
>        return Thing (I);
>     end To_Thing;
> 
>     C : constant Integer := A.R;
> end B;
> 
> It seems to me there's a valid elaboration order for these:
> 
> * spec of B
> * spec of A
> * body of A
> * body of B
> 
> I've never been able to get such code to bind, though. Is there some way to get 
> this accepted, or is it illegal Ada?

It's legal Ada (and should run without raising Program_Error).  It looks like http://docs.adacore.com/gnat-unw-docs/html/gnat_ugn_36.html, especially C.10, discusses this sort of situation, but I don't know if you looked there already.

                                -- Adam