Thread: Re: [GENERAL] division by zero
"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?
regards, tom lane
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.
Tom Lane wrote: <snip> > 2. Consider this Apple's problem and file a bug report. Is there a good place to report errors to Apple for this kind of thing? Was chatting to one of the guys in the MacOSX development team at Apple a while ago and can pursue it through there if needed. :-) Regards and best wishes, Justin Clift > 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? > > regards, tom lane -- "My grandfather once told me that there are two kinds of people: those who work and those who take the credit. He told me to try to be in the first group; there was less competition there." - Indira Gandhi
On Saturday, March 8, 2003, at 11:54 PM, Justin Clift wrote: > Tom Lane wrote: > <snip> >> 2. Consider this Apple's problem and file a bug report. > > Is there a good place to report errors to Apple for this kind of thing? The best place I can find is: http://developer.apple.com/bugreporter/index.html Unfortunately, there doesn't seem to be a way to query existing reports... If there is, I can't find it. Also, I can't help but wonder why Apple/DarwinTeam handle integer division by zero this way. There must be a reason, which makes me think that "[considering] this Apple's problem" might not work out for postgres in the end. eric
Hi guys, Was just looking around Google for similar reports of errors and came across this: MacOS X Server Developer Release Notes: Core OS Runtime http://www.geminisolutions.com/WebObjects_4.5/Documentation/Developer/YellowBox/ReleaseNotes/Runtime.html Looks like this is a known problem (as of 1998) and may not have been fixed. Further hits come up when searching on the Apple Developer Connection site too: http://developer.apple.com/cgi-bin/search.pl?&q=divide+by+zero&num=10&lang=lang_en|lang_zh-CN|lang_fr|lang_de|lang_ja&ie=utf8&oe=utf8 (that should be all one line) And this one looks potentially interesting: http://developer.apple.com/technotes/tn2002/tn2053.html (search in this page for "FE_ENABLE_DIVBYZERO") Have asked the member of the Apple MacOS X Server team what he recommends the best way to proceed is. Regards and best wishes, Justin Clift Eric B.Ridge wrote: > On Saturday, March 8, 2003, at 11:54 PM, Justin Clift wrote: > >> Tom Lane wrote: >> <snip> >> >>> 2. Consider this Apple's problem and file a bug report. >> >> >> Is there a good place to report errors to Apple for this kind of thing? > > > The best place I can find is: > http://developer.apple.com/bugreporter/index.html > > Unfortunately, there doesn't seem to be a way to query existing > reports... If there is, I can't find it. > > Also, I can't help but wonder why Apple/DarwinTeam handle integer > division by zero this way. There must be a reason, which makes me think > that "[considering] this Apple's problem" might not work out for > postgres in the end. > > eric > -- "My grandfather once told me that there are two kinds of people: those who work and those who take the credit. He told me to try to be in the first group; there was less competition there." - Indira Gandhi