Re: Fix typo 586/686 in atomics/arch-x86.h

From: Daniel Gustafsson <daniel(at)yesql(dot)se>
To: John Naylor <johncnaylorls(at)gmail(dot)com>
Cc: Jakub Wartak <jakub(dot)wartak(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Andres Freund <andres(at)anarazel(dot)de>
Subject: Re: Fix typo 586/686 in atomics/arch-x86.h
Date: 2025-12-19 09:04:40
Message-ID: 1B700BBA-B5F0-49D1-8F8F-51F377825FC4@yesql.se
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> On 19 Dec 2025, at 08:23, John Naylor <johncnaylorls(at)gmail(dot)com> wrote:
>
> On Fri, Nov 28, 2025 at 4:00 PM Daniel Gustafsson <daniel(at)yesql(dot)se> wrote:
>>
>>> On 28 Nov 2025, at 09:44, Jakub Wartak <jakub(dot)wartak(at)enterprisedb(dot)com> wrote:
>>>
>>> That's a typo in src/include/port/atomics/arch-x86.h, isn't it ?:
>>> if defined(__i568__) || defined(__i668__) || /* gcc i586+ */
>>> If yes, then a patch is attached. Not that it harms something or
>>> somebody has such old hardware, but I've just spotted it while looking
>>> for something else.
>>
>> That indeed looks like a clear typo, but if noone has complained since 2017
>> then maybe removing the checks is the right course of action?
>
> I believe CI tests with -m32, so as long as we do that we should
> probably make that work the way we think it does.

It does, but will this affect that? Does gcc change the CPU arch to 32bit era
hardware when using -m32? I was under the impression that it built code that
can run in 32-bit mode on the underlying hardware unless a specific target arch
was defined - but this is outside my wheelhouse so I might well be uninformed.

Regardless, applying this shouldn't affect anything unless compiling on Pentium
Pro or pre-MMX Pentium instruction sets, so it seems quite harmless and as the
intention was to support it the best course of action is probably to just apply
this.

--
Daniel Gustafsson

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