Re: Fix overflow in DecodeInterval

Joseph Koshakow <koshy44(at)gmail(dot)com> writes:
> Ok I actually remember now, the issue is with the rounding
> code in AdjustFractMicroseconds.
> ...
> I believe it's possible for `frac -= usec;` to result in a value greater
> than 1 or less than -1 due to the lossiness of int64 to double
> conversions.

I think it's not, at least not for the interesting range of possible
values in this code. Given that abs(frac) < 1 to start with, the
abs value of usec can't exceed the value of scale, which is at most
USECS_PER_DAY so it's at most 37 or so bits, which is well within
the exact range for any sane implementation of double. It would
take a very poor floating-point implementation to not get the right
answer here. (And we're largely assuming IEEE-compliant floats these
days.)

Anyway, the other issue indeed turns out to be easy to fix.
Attached is a v11 that deals with that. If the cfbot doesn't
complain about it, I'll push this later today.

regards, tom lane