Re: [BUGS] BUG #14722: Segfault in tuplesort_heap_siftup, 32 bit overflow

Heikki Linnakangas <hlinnaka@iki.fi> writes:
> On 07/06/2017 01:14 AM, Andres Freund wrote:
>> On 2017-07-05 18:03:56 -0400, Tom Lane wrote:
>>> I don't like s/int/int64/g as a fix for this.  That loop is probably
>>> a hot spot, and this fix is going to be expensive on any machine where
>>> int64 isn't the native word width.  How about something like this instead:

> Another option to use "unsigned int", on the assumption that UINT_MAX >= 
> INT_MAX * 2 + 1.

Ah, that seems like a fine idea.

> And to eliminate that assumption, we can use (UINT_MAX 
> - 1) / 2 as the maximum size of the memtuples array, rather than INT_MAX.

Uh ... what assumption?  That's certainly true on any twos-complement
machine.  Besides, if you're worried about hypothetical portability
issues, I'm not sure it's any better to assume that (UINT_MAX - 1) / 2
fits in a signed int.
        regards, tom lane


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