Re: Elaboration circularity with generics

[Adam Beneschan <adam@irvine.com>]

On Jan 16, 1:29 pm, Maciej Sobczak <see.my.homep...@gmail.com> wrote:
> On Jan 16, 3:34 pm, Robert A Duff <bobd...@shell01.TheWorld.com>
> wrote:
>
> > > In such a case I would consider it to be a compiler bug.
>
> > I don't see any compiler bug here.
>
> What I'm concerned about is portability. If the compiler is allowed to
> refuse my program even though there is no paragraph saying that my
> program is illegal, then perhaps some other compiler will compile it
> without any trouble. Which means that my program will not be portable,
> even though it might not touch any implementation limits or other
> similarly valid reasons.

The problem is that without any additional Elaborate pragmas, a
compiler *could* compile the program, but it would be useless as it
would raise Program_Error right away.  Another compiler might build
the program and choose a different elaboration order that doesn't
raise Program_Error.  Neither of these compilers would be wrong, since
the language doesn't specify the exact elaboration order when there is
more than one that obeys the Elaborate pragmas and other language
rules.  So your program as written isn't portable at all; and even
though technically a compiler should accept the program, if you're
concerned about portability then you should be grateful that GNAT (in
its non-standard mode) rejected the program and alerted you to the
portability problem in your code.  I don't think you have a legitimate
complaint about GNAT here, at least not on portability grounds.

                             -- Adam