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

From: Martin Krischik (martin_at_krischik.com)
Date: 11/30/04 

Date: Tue, 30 Nov 2004 14:24:54 +0100

Preben Randhol wrote:

> In article Marius Amado Alves wrote:
>>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.
>
> I'm confused. Didn't they turn off all exceptions checks?

They turned of a few select runtime checks. They had proof that on an Ariane
4 they would not be needed as the Arinane 4 will never exceed the max.
values.

However, as Alexander pointed out, with the software checks disabled some
hardware checks from the floating point unit kicked in instead and crashed
the hole programm.

You must understande that modern CPUs there support hardware exceptions and
modern programming laguages support software exceptions. And they have
nothing to do with each other.

On as side note: The new M$ C and C++ compiler automaticly convert hardware
exceptions into software exceptions - which I have to confess make things a
lot easier.

With Regards

Martin 

-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com

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