Re: [OT] Re: Teaching new tricks to an old dog (C++ -->Ada)

["Paul E. Bennett" <peb@amleth.demon.co.uk>]

Martin Krischik wrote:

> <ver�ffentlicht & per Mail versendet>
> 
> Paul E. Bennett wrote:
> 
>> Ludovic Brenta wrote:
>> 
>>> * when the compiler cannot check some code statically, it inserts
>>>   run-time checks which are guaranteed to catch all errors by raising
>>>   exceptions.  In C++ you must code these checks by hand, and of
>>>   course at some point you'll forget one crucial check which will cost
>>>   you days in debugging.
>> 
>> I think the fallacy of that statement has been proven already (in a very
>> expensive way).
> 
> You mean the case where some managers decided to use some software written
> for one pice of hardware on another - incompatible - pice of hardware -
> without retesting?
> 
> In my book that was a management bug - If the managers had ordered to run
> the testsuite only once the problem would have shown. The hardware was so
> incompatible it would have failed all the time.
> 
> Last not least: Runtime check where disabled for that incident. So if
> anything: this incident speak in favor of runtime checks.
> 
> Read up your facts: http://en.wikipedia.org/wiki/Ariane_5_Flight_501
 
Yes, I have read that and the full report. However, I think my comment 
still stands. You stated "when the compiler cannot check some code 
statically, it inserts run-time checks which are guaranteed to catch all 
errors by raising exceptions". The code had to be compiled, for the new 
hardware, to be installed in the guidance system and hence should have had 
the run-time checks in place if static checking could not be done. You have 
admitted in your response that these checks were not active (by management 
decision) so the Ada compiler was circumvented and prohibited from adding 
these checks.

Considering that the proposition in this thread has been "Ada protects you 
from making silly mistakes" I consider that your take is counter to the 
evidence. I still maintain that language is immaterial to the safety of the 
system, relying on decent rigourously applied development processes, 
reviews and testing. Therefore, I tend to look at the development processes 
and their "real" CMM rating. I guess the Ariane team went down a few 
notches on that project.

-- 
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Paul E. Bennett ....................<email://peb@amleth.demon.co.uk>
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