| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
| Cc: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: 64-bit integer subtraction bug on some platforms |
| Date: | 2023-11-08 16:08:05 |
| Message-ID: | 685674.1699459685@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> writes:
> On Wed, 2023-11-08 at 11:58 +0000, Dean Rasheed wrote:
>> This should overflow, since the correct result (+9223372036854775808)
>> is out of range. However, on platforms without integer overflow
>> builtins or 128-bit integers, pg_sub_s64_overflow() does the
>> following:
>> ...
>> which fails to spot the fact that overflow is also possible when a ==
>> 0. So on such platforms, it returns the wrong result.
>>
>> Patch attached.
> The patch looks good to me.
+1: good catch, fix looks correct.
regards, tom lane
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