On Feb 13, 2012, at 05:16, robin wrote:
>
> The programming world is littered with "it can't happen" cases.
> Everyone knows Murphy's Law ("If anything can go wrong, it will").
> But not many have heard of Robert's Law? ("Even if it can't go wrong, it
> will".)
>
> So, even it the length were tested prior, one can't assume that all
> will be well when the EX is reached.
>
What boundaries do you place on Robert's Law? Must the programmer
check for overflow after every fixed point operation, even when
it is known a priori that the operands are such that no overflow
is possible? How about:
SR R2,R2 Clear GR2
BO OVERFLOW_ERROR
??? (There's some argument here for using XR instead of SR for
this purpose if an automated style checker mandates the overflow
test.)
Hardware detection of arithmetic exceptions is a boon here. But
one ISV C compiler requires that the generated code be run with
fixed-point overflow interrupts disabled. Shame on the vendor!
-- gil
