Re: [PATCH v6 1/3] rust: configfs: introduce rust support for configfs

[Andreas Hindborg <a.hindborg@kernel.org>]

"Miguel Ojeda" <miguel.ojeda.sandonis@gmail.com> writes:

> On Mon, May 5, 2025 at 9:51 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> So I was thinking that because I am initializing a static with a let
>> statement, it would run in const context. But I see that it is not
>> actually guaranteed.
>
> No, that is actually guaranteed, i.e. when initializing a static. But
> you aren't initializing a static here, no? Which static are you
> referring to? If you were, then the "normal" `assert!` would work,
> because it would be a const context.
>
> The `add` calls I see are just in the `let` statement, not
> initializing any static:
>
>             {
>                 const N: usize = 0usize;
>                 unsafe { CONFIGURATION_ATTRS.add::<N, 0,
> _>(&CONFIGURATION_MESSAGE_ATTR) };
>             }
>
> So it also means this comment is wrong:
>
> +        // SAFETY: This function is only called through the `configfs_attrs`
> +        // macro. This ensures that we are evaluating the function in const
> +        // context when initializing a static. As such, the reference created
> +        // below will be exclusive.
>
> Please double-check all this... :)

Oops.

>
>> Right. Which is why I opted for `build_error`. But with the `const`
>> block solution you suggested is better.
>
> I thought you opted for that because you thought the `assert!` would
> only work if not refactored. What I tried to point out was that the
> `assert!` wouldn't have worked even before the refactoring.

I made a mistake in thinking this was in const context. I'll see if I
can fix that.



Best regards,
Andreas Hindborg