linux-kernel - Re: [PATCH v2] rust: num: bounded: mark _

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Message-Id: <DEOKZ255N1YJ.1U9OX5KDWQGY2@nvidia.com>
Date: Wed, 03 Dec 2025 21:29:36 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "Hsiu Che Yu" <yu.whisper.personal@...il.com>, "Alexandre Courbot"
 <acourbot@...dia.com>
Cc: <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>,
 "Miguel Ojeda" <ojeda@...nel.org>, "Yury Norov" <yury.norov@...il.com>,
 "Boqun Feng" <boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Benno Lossin"
 <lossin@...nel.org>, "Andreas Hindborg" <a.hindborg@...nel.org>, "Alice
 Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>, "Danilo
 Krummrich" <dakr@...nel.org>
Subject: Re: [PATCH v2] rust: num: bounded: mark __new as unsafe

On Tue Dec 2, 2025 at 12:25 PM JST, Hsiu Che Yu wrote:
> The `Bounded::__new()` constructor relies on the caller to ensure the
> value can be represented within N bits. Failing to uphold this
> requirement breaks the type invariant. Mark it as unsafe and document
> this requirement in a Safety section to make the contract explicit.
>
> Update all call sites to use unsafe blocks and change their comments
> from `INVARIANT:` to `SAFETY:`, as they are now justifying unsafe
> operations rather than establishing type invariants.
>
> Fixes: 01e345e82ec3a ("rust: num: add Bounded integer wrapping type")
> Reported-by: Miguel Ojeda <ojeda@...nel.org>

Wasn't it Alice who said that `__new` should be unsafe?

Although Miguel did create the bug. In any case, maybe add a `Link:` tag
to this:

https://lore.kernel.org/all/aS1qC_ol2XEpZ44b@google.com/

> Closes: https://github.com/Rust-for-Linux/linux/issues/1211
>
> Signed-off-by: Hsiu Che Yu <yu.whisper.personal@...il.com>

The empty line is not needed.

With this,

Acked-by: Alexandre Courbot <acourbot@...dia.com>