Re: How would Ariane 5 have behaved if overflow checking were notturned off?

["Vinzent Hoefler" <0439279208b62c95f1880bf0f8776eeb@t-domaingrabbing.de>]

robin wrote:

> Vinzent Hoefler <0439279208b62c95f1880bf0f8776eeb@t-domaingrabbing.de> wrote in message ...
>> Elias Salomão Helou Neto wrote:
>
>>> Since then I have been wondering. If compiler checking where actually
>>> turned on, what would have happened?
>
>> The same, according to the specification.
>
>>> How could it avoid the disaster?
>
>> Not at all.
>
> On the contrary., an error handler would have performed
> something useful.

Precisely what? The _only_ reasonable action at that point was to assume
a hardware error and shutdown the computer. For Ariane 4, that is.

> The crux of the matter is that the data bus would not have been
> loaded with an error number [which was then treated as guidance data].

AFAIK this was required in case both systems died. And as we know, they
did exactly that. I'd assume the possibility of two hardware errors at
the same time were considered remote.

>> By handling it exactly the way it was supposed to be:
>
>> Assuming a hardware error and leave control to the redundant subsystem.
>
> That was the major blunder that they made,
> namely, treating a programming error as a hardware error.
> By doing that, they guaranteed failure of the mission.

Again. In the Ariane 4 it would have been exactly that. A hardware error.
There was no freaking way, Ariane 4 could have exceeded the safe range.

>>> Which one, if any, is close to reality?
>
>> As it has been mentioned here many times before, the software behaved
>> exactly as specified and it is very unlikely that _any_ error handling
>> could have avoided the problem
>
> An error handler would have rescued the mission.

Only if were not behaving according to the specification. That means if
it were buggy - and that's exactly what you snipped from my previous
response.


Vinzent.

-- 
A C program is like a fast dance on a newly waxed dance floor by people carrying
razors.
    --  Waldi Ravens