The wording isn't ambiguous. It explains the criteria for an implementation
to be considered conforming. Your question is not about implementation
conformance, so it at most identifies awkward phrasing, not a genuine
ambiguity.

*Brian Bi*

On Tue, Oct 13, 2026, 10:46 PM jim x via Std-Discussion <
std-discussion_at_[hidden]> wrote:

> I'm trying to express the ambiguity I think about the wording.
>
> It doesn't say that accesses to volatiles *are* atomic.
>
>
> Yes. However, the standard simultaneously permits the implementation to
> define the semantics, which leaves a slot for implementations to define the
> parameterized part of the abstract machine. This leaves room for us to
> think about whether the operations associated with volatile glvalue
> are atomic or non-atomic* because they are parameterized by the
> implementations. *This is my confusion about the wording.
>
> On Tue, Oct 13, 2026 at 10:52 PM Thiago Macieira <thiago_at_[hidden]>
> wrote:
>
>> On Tuesday, 13 October 2026 01:43:01 Pacific Daylight Time jim x wrote:
>> > One of the grounds for your claim that the program exhibits undefined
>> > behavior is that you determined it contains a data race based on
>> > [intro.race] p17. But the very issue is: where does the standard state
>> that
>> > an access to a volatile glvalue is non-atomic? The standard does not
>> even
>> > define the semantics of such accesses and leaves them
>> > implementation-defined, making it even less possible to assert that
>> > accesses to a volatile glvalue are non-atomic. How, then, can you
>> conclude
>> > based on [intro.race] that this program contains a data race?
>>
>> It doesn't say that accesses to volatiles *are* atomic. Therefore, they
>> aren't
>> required to be and thus your example is a data race.
>>
>> jim, you've argued this over and over again. Everyone has the same
>> interpretation of the Standard except you and you keep arguing the same
>> thing
>> over and over again. What do you want to happen? Do you want a Standard
>> text
>> change to clarify things one way or another? If so, please propose it.
>> Are you
>> trying to argue with a vendor about their functionality?
>>
>> --
>> Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
>> Principal Engineer - Intel Data Center - Platform & Sys. Eng.
>>
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