Re: power() function in Windows: "value out of range: underflow"

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Sun, Apr 29, 2018 at 7:24 PM, David Rowley
> <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
>> I think we should back patch and try to be consistent about the
>> power(float8 1.0, 'NaN') and power('NaN', float8 0.0) cases. The
>> archives don't show any complaints about power() with NaN until this
>> one, so I imagine the number of people affected by this is small.

> I agree that this is not likely to affect a lot of people -- but the
> question isn't how many people will be affected but rather, of those
> that are, how many of them will be pleased rather than displeased by a
> change. I would argue that the results have to be unambiguously wrong
> in the back-branches to justify a change there, and this doesn't
> appear to meet that standard. I would guess that the number of people
> who use NaN is very small, but those people have probably adapted
> their application to the behavior they are getting currently.

The point here, I think, is that you get behavior X on approximately 100%
of modern platforms, but (without this patch) behavior Y on some number of
older platforms. People who have tested their app on a modern platform
and then find that it misbehaves on an old one will think this is a bug
fix. People who only run their app on an old platform may think the
pre-patch behavior is fine, in which case they will indeed be upset if
we change it in a minor release. Are there more of the latter than the
former? I don't really know, and you don't either. But I don't think
we should discount the existence of the former category. Deploying
to production on an older release of $system than you develop on
is hardly an unusual scenario.

regards, tom lane