Re: init_htab causes SIGFPE (or worse) due to miscalculation for large nbuckets

On Mon, 2012-12-10 at 20:27 -0500, Tom Lane wrote:
> Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> > It looks like all of the callers, except two, immediately shift the
> > result. So perhaps it would be better to make a new function (something
> > like "ceil_pow2") that returns the lowest power of two greater than or
> > equal to the input, and it can return a long (bounded to +LONG_MAX).
>
> That does seem like a good idea. We need one for an int-sized result
> too, to fix the original problem in init_htab. So I propose these
> functions:

Looks good to me. One other corner case in the version of the patch I
was working on was that nbuckets is compared to num_partitions, which is
a long. We can assert that it is less than or equal to INT_MAX in
hash_create.

Aside from that, I'll drop my version of the patch, which doesn't have
any useful differences from yours.

Regards,
Jeff Davis