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From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
To: Alice Ryhl <aliceryhl@google.com>
Cc: Andrew Ballance <andrewjballance@gmail.com>,
	Joel Fernandes <joelagnelf@nvidia.com>,
	 rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
	 John Hubbard <jhubbard@nvidia.com>,
	Alexandre Courbot <acourbot@nvidia.com>,
	Timur Tabi <ttabi@nvidia.com>,
	 Alistair Popple <apopple@nvidia.com>,
	Miguel Ojeda <ojeda@kernel.org>
Subject: Re: Printing with overflow checks can cause modpost errors
Date: Fri, 12 Sep 2025 12:08:12 +0200	[thread overview]
Message-ID: <CANiq72=89-22iORBttRtNeMN1ZHzH=MRvqfS5qPufHsMx8C0ng@mail.gmail.com> (raw)
In-Reply-To: <CAH5fLgiP2DRcGy04YdsWS9+N1=_CCNEtAGrCn31vUHjnDLW9xw@mail.gmail.com>

On Fri, Sep 12, 2025 at 11:45 AM Alice Ryhl <aliceryhl@google.com> wrote:
>
> I believe this code is using an immutable reference and not just a
> pointer, so it would be UB to use it to write to `offset`, and so it
> would be valid to assume it has not changed. But I think that in most
> scenarios, Rust only optimizes using that information when the
> reference appears as a function argument, which is not the case here.

I understood Andrew as talking about the C side, i.e. a guarantee
coming from the C side.

Callers can guarantee in other ways, but I wanted to clarify that the
C const pointer doesn't really do anything.

Cheers,
Miguel

  reply	other threads:[~2025-09-12 10:08 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-11 21:31 Printing with overflow checks can cause modpost errors Joel Fernandes
2025-09-12  0:27 ` Andrew Ballance
2025-09-12  2:53   ` Joel Fernandes
2025-09-12  4:08     ` Andrew Ballance
2025-09-12  8:27       ` Miguel Ojeda
2025-09-12  9:45         ` Alice Ryhl
2025-09-12 10:08           ` Miguel Ojeda [this message]
2025-09-16 10:32       ` Joel Fernandes
2025-09-16 10:48         ` Joel Fernandes
2025-09-16 18:52           ` Joel Fernandes
2025-09-17 23:18             ` Timur Tabi

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