Re: random() function produces wrong range

Tom Lane writes:
> I thought about that last night. We could do a configure test. Since
> it'd be probing random() results there'd be a small probability of
> failure, but if we wire in an assumption that the max value must be
> 2^(15 + n*16)-1 for some n, ten or so probes would give us a failure
> probability on the order of 2^-160, which ought to satisfy anyone.
>
> However, in the absence of any hard evidence that there are platforms
> where the value is different from 2^31-1, it's probably just a waste of
> configuration cycles at the moment.
>
> I suggest we add a config.h constant like
>
> /* The local random() function yields values 0 .. MAX_RANDOM_VALUE */
> #define MAX_RANDOM_VALUE <2^31-1>
>
> and use that in the code. Then, if we ever find a platform where
> random() does actually produce 64-bit results, it'll be time enough
> to crank up a real configure test to set the value.
>
> Comments?

If any platform *does* produced 64-bit results, it won't be compliant
with SUSv2 which states explicitly that the resulting range is up to
2^31-1. Since most portability problems are with older platforms which
haven't caught up, I'd be hopeful that any new 64-bit-int platforms
would get it right from the outset. Maybe I'm being over-optimistic :-)

--Malcolm

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