Re: Customer balks at Ada -- any hope?

["Ken Garlington" <Ken.Garlington@computer.org>]

"fdebruin" <fdebruin@xs4.xs4all.nl> wrote in message
news:8l40kb$7na$1@xs4.xs4all.nl...
> Kieran Mckey <kieran.mckey@baesystems.com> writes:
>
> >compiler switches. You should design the system so that the code will
> >meet performance requirements regardless of whether run-time checks are
> >enabled or not.
> >
> Sometimes, you don't have that luxury.
>
> For example, on-board systems for spacecrafts usually have very limited
> resources available and you're faced with restricitions w.r.t. the
> selection of processor and memory size avaible.

Don't forget another aspect of run-time checks that is particularly
important to embedded systems: Run-time checks are completely worthless...
unless you have a proper course of action to take when they occur.

For example, consider the Ariane 5 case. Let's assume that run-time checking
was completely enabled, and a Constraint_Error was therefore raised on the
floating-point to integer conversion (instead of the machine interrupt).
Unless there had been a local exception handler to take an appropriate
action (and it's somewhat of an open question as to the right action,
although saturating the output would have been the obvious choice), then the
exception would have propagated to the gloabl exception handler -- and the
exact same outcome would have occurred. Adding these local exception
handlers, of course, will use up some resources (memory, programmer time,
etc.) so they're certainly not "free".