[SystemSafety] Stupid Software Errors [was: Overflow......]

[David Haworth]

Peter,

On 2015-05-05 09:03:31 +0200, Peter Bernard Ladkin wrote:
> After fifty years of programs not handling date and time correctly,
> even according to their own
> requirements, including the single most expensive anomaly in history
> coming in at well over
> $300bn, it surely requires heroic nonchalance to suggest
> 
> > .... this is a non-issue.

I've also seen my fair share of time/date problems, including
the impending Year 2038 bug (which no-one seems to be worrying
much about).

I also notice that 248 days is pretty well exactly the range of
a 32-bit signed integer incremented as 10ms intervals. So this
is quite emphatically *not* a time/date issue, but an uptime
issue.

Many control systems have specified maximum uptimes. They
often rely on checks and tests performed at startup or shutdown
to detect latent hardware failures. Destructive RAM tests
are a prime example of things that cannot be done properly
during operation.

I also notice that the press reports state that the systems "shut
themselves down", not "crash", which implies (to me at least)
that there is at least some error detection and handling going on.

So, in the absence of any detailed technical information about
the requirements, design, implementation, service documentation,
operational manuals etc. about these systems, I stand
by my opinion until facts emerge that prove me wrong.

There are worse things to worry about.

Dave


-- 
David Haworth B.Sc.(Hons.), OS Kernel Developer    david.haworth at elektrobit.com
Tel: +49 9131 7701-6154     Fax: -6333                  Keys: keyserver.pgp.com
Elektrobit Automotive GmbH           Am Wolfsmantel 46, 91058 Erlangen, Germany
Geschäftsführer: Alexander Kocher, Gregor Zink       Amtsgericht Fürth HRB 4886


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