Re: Elaboration in GNAT

[dewar@gnat.com (Robert Dewar)]

Robert A Duff <bobduff@shell01.TheWorld.com> wrote in message news:<wcc1ygx50tn.fsf@shell01.TheWorld.com>...
> True, but is it not also the case that these bugs are 
> relatively
> innocuous?  That is, if you forget your pragmas, then 
> your program
> usually blows up during elaboration (and you fix it), or 
> else it doesn't
> blow up (using this compiler).  That is, it's more of a 
> *portability*
> problem, than a problem of programs malfunctioning when 
> users use them.

In a large program, one with thousands of units, and millions of lines
of code, it can take weeks or months
of fiddling to find all the pragma Elaborate's that are
required, when you have to do a complete build to find
just one of them. Often in such a situation it may be
better to aim for the static solution off the bat.

> Ideally, all elaboration problems would be detected at 
> compile time (or
> link time), and there would be no constraints on the 
> structure of a
> program due to elaboration-order issues.  Ada (even with 
> GNAT's default
> mode) does not achieve that, unfortunately.

I understand that this is theoretically true, but in practice with
GNAT's static model problems do not arise.
We have not had one customer using the static model ever
run into any elaboration problems at all. So from a 
pragmatic point of view, the problem is solved.