Re: Crosspost: Help wanted from comp.compilers

["John R. Strohm" <strohm@airmail.net>]

"Jeffrey Carter" <spam@spam.com> wrote in message
news:3F14B061.1040802@spam.com...
> John R. Strohm wrote:
> >
> > Now, it was EASY to build systems that had horrendous recompilation
> > problems.  Usually, in order to build such a system, you had to screw up
> > some fairly basic software engineering things.  For example, if you
build a
> > system-wide "types" package, then every time you touch that package, you
get
> > to recompile the world.  If you build a system-wide "magic numbers"
package,
> > same problem.  Observe that the exact same problems arise in C/C++.  The
> > answer is, of course, DON'T DO THAT.
>
> These are fairly benign problems. I know of at least one current DoD
> project that has a system-wide "variables" package. This software is
> flying in a state-of-the-art military aircraft. Not only do most
> upgrades involve modifying this package, and hence recompiling the
> entire system, but the system is 100% coupled with 0% cohesion.
> Understanding the system from scratch is at least as expensive as
> redesigning and rewriting the entire system; that's the choice they will
> face if the couple of developers, who have been there from the beginning
> and have the entire system in their heads, ever quit or are killed going
> out to lunch together.

I am not at all surprised to hear this.

Sometimes you run into that kind of overcoupling and undercohesion because
of timeline/fairness concerns.  The system designer has to guarantee that
every task DOES get his assigned timeslice, every time, or things can go to
hell in a handcart in a hell of a hurry.  You want a horrible example?
Calculate a dive toss delivery, and see just how small your release time
window really is.  And EVERYTHING has to run, in the right order, to
calculate the delivery and decide when to tell the latches to let go of the
bomb.  And then the actual release message has to get out to the latches on
the rack...

I am curious, though.  Can you say what project it is?