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Date: Mon, 23 Mar 2026 10:24:51 -0400
From: "Greg Burd" <greg@burd.me>
To: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: "Peter Eisentraut" <peter@eisentraut.org>,
 "Thomas Munro" <thomas.munro@gmail.com>,
 "PostgreSQL Hackers" <pgsql-hackers@lists.postgresql.org>
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Subject: Re: Trying out <stdatomic.h>
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On Mon, Mar 23, 2026, at 10:13 AM, Tom Lane wrote:
> "Greg Burd" <greg@burd.me> writes:
>> On Mon, Mar 23, 2026, at 7:57 AM, Peter Eisentraut wrote:
>>> We currently require MSVC 2019, so before this could be accepted, this 
>>> requirement would need to be adjusted (including documentation, 
>>> buildfarm updates, etc.).
>

Hi Tom, thanks for chiming in. :)

>> Fair point, it does seem that's the minimum supported version (2022).
>
> I don't really see why we'd need to do that?  I would expect any such
> patch to cope gracefully with the lack of <stdatomic.h>, so it could
> continue to support older MSVC by falling back to the older code
> paths.  For MSVC in particular, we'd not even need to maintain the
> older code paths for arches other than x86 and ARM.

Fair, and I agree.

> But even disregarding Windows, I'd look with great suspicion on a
> patch that proposes to rip out all that handwritten code in favor of
> requiring <stdatomic.h>.  That'd be putting a great deal of trust in
> code that's not under our control and frankly we have no reason to
> trust yet, especially not from the standpoint of performance rather
> than just minimum functionality.

Yes, I 100% agree.  That is a valid concern.

> Note that the thread title is
> "Trying out <stdatomic.h>", not "We're marrying <stdatomic.h>
> sight-unseen, and there will be no divorce".

This made me laugh, thank you. :)

> So I want to see a
> patch that treats <stdatomic.h> as an alternative implementation,
> not The Only Way.

Got it.

> As for timing, this is the sort of patch that we usually feel should
> go in near the start of a dev cycle, not near the end.  So I counsel
> making sure that it's in shape for commit early in v20, but not
> expecting that it will get in now, even temporarily.  There are too
> many irons in the fire at this phase of the cycle, and too little
> room to disambiguate "Greg broke it" from "somebody else broke it".

Yep, that's prudent and you're right to point out that the breaking the farm isn't really a good way to test at this stage.

> 			regards, tom lane

best.

-greg