Re: division by zero

On Sat, 8 Mar 2003, Tom Lane wrote:

> "Eric B. Ridge" <ebr@tcdi.com> writes:
> > select 1/0; fails as expected on my x86 Linux box, so yer right, it's
> > just my little Mac.  "I switched because Mac's can divide by zero."
>
> I checked into this, and indeed OS X 10.2 is behaving funny: integer
> divide by zero doesn't raise any signal, it just returns a bogus answer.
> They're within their rights to do so according to the ANSI C spec
> (wherein division by zero is stated to have undefined behavior).
> But since other BSD-derived Unixen all seem to raise SIGFPE, I can't
> help wondering if this shouldn't be considered a bug.
>
> I think we have three possible responses:
>
> 1. Put explicit tests for zero into the integer division SQL function
> routines.
>
> 2. Consider this Apple's problem and file a bug report.
>
> 3. Both.
>
> I don't care for answer #1 alone, because it would only catch zero
> divides in the specific places we put in tests; internal errors would
> likely go uncaught.  So I think a complaint to Apple is in order.
> I'm not sure whether to also put in zero-divide guards.  Comments?

We probably should put in guards since relying on sane behavior for
division by zero is probably unsafe from a portability standpoint.  This
could hide some internal error on a system that has this problem (since we
could otherwise put it into a regression test) but those systems are
currently broken if the internal error occurs anyway.