Re: Ariane 5 failure

[bobduff@world.std.com (Robert A Duff)]

In article <324F1157.625C@dynamite.com.au>,
Alan Brain  <aebrain@dynamite.com.au> wrote:
>Brain's law:
>"Software Bugs and Hardware Faults are no excuse for the Program not to
>work".   
>
>So: it costs peanuts, and may save your hide.

This reasoning doesn't sound right to me.  The hardware part, I mean.
The reason checks-on costs only 5% or so is that compilers aggressively
optimize out almost all of the checks.  When the compiler proves that a
check can't fail, it assumes that the hardware is perfect.  So, hardware
faults and cosmics rays and so forth are just as likely to destroy the
RTS, or cause the program to take a wild jump, or destroy the call
stack, or whatever -- as opposed to getting  a Constraint_Error a
reocovering gracefully.  After all, the compiler doesn't range-check the
return address just before doing a return instruction!

- Bob