Re: Would You Fly an Airplane with a Linux-Based Control System?

[snarflemike@yahoo.com (Mike Silva)]

Marius Amado Alves <amado.alves@netcabo.pt> wrote in message news:<mailman.123.1101469316.10401.comp.lang.ada@ada-france.org>...
> Alexander E. Kopilovich wrote:
> >... 
> > - The on-board software detects that one of the accelerometers is out of
> > range (actually, there was FPU exception generated when float-to-integer 
> > conversion exceeded the capacity of the integer), this was interpreted as
> > hardware error and caused the backup processor to take over;...
> > 
> > Do you agree that this addition is enough there?
> 
> No. This whole talk of hardware-generated exception sounds like "FUD". 
> Namely, it sounds like your trying to blame the hardware. The cause was 
> a SOFTWARE enginering error. Yes, a BUG. In the Ada software. And 
> because it's connected to exceptions, the hypothesis that if the thing 
> had been done in an exceptionless language like C the effect might have 
> been different. And yes, maybe less bad. And none of the explanations 
> I've seen so far (here, in books, and in the Internet) disprove this 
> hypothesis.

Even accepting your assertion that your hypothesis has not been
disproven, what conclusion do you draw?  That deliberately ignoring
out-of-range data (not throwing it away, just ignoring it) will
generally lead to safer systems than dealing with out-of-range data in
some pre-determined way that may not always be the right choice
(especially if the system is mis-used in a manner so that out-of-range
data is suddenly legal)?

What, again, is your conclusion?