Universal OS (was Re: Survey of architectures)

[Doug Gwyn]

In article <670016 at hpclscu.HP.COM> shankar at hpclscu.HP.COM (Shankar Unni) writes:
>For instance, SIGFPE (which now has an underground subcode which may mean
>just about anything, depending on what system you are on..) could either have
>an ARCHITECTED subcode, or be changed to a whole new array of codes, for
>different things like Integer Overflow, Divide by zero, Floating-point
>underflow and so on... 

No matter how much work you put into an attempt to specify a fully
general (i.e. portable) floating-point exception status data structure,
I guarantee I can dream up a floating-point architecture that you
haven't accommodated.  There is nothing that forbids implementation-
dependent extensions for SIGFPE handlers, but you need to be aware
that they ARE implementation dependent.

Frankly, I think you should consider SIGFPE a fatal symptom that
indicates that you haven't designed a good enough algorithm; the
correct solution is to fix the algorithm, not interpret the state
of the floating-point processor once it's already too late.  The
simple use of SIGFPE is sufficient for this.