linux-kernel - Re: [PATCH v2 2/5] rust: enable `clippy::ptr_as

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Message-ID: <CAJ-ks9kOLgXrOHucFXHB+DwZEZpZEKhBNmXKh_hB_agrq=2n6g@mail.gmail.com>
Date: Wed, 12 Mar 2025 11:18:54 -0400
From: Tamir Duberstein <tamird@...il.com>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Masahiro Yamada <masahiroy@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nicolas Schier <nicolas@...sle.eu>, Miguel Ojeda <ojeda@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
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	Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Brendan Higgins <brendan.higgins@...ux.dev>, David Gow <davidgow@...gle.com>, 
	Rae Moar <rmoar@...gle.com>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Luis Chamberlain <mcgrof@...nel.org>, Russ Weight <russ.weight@...ux.dev>, Rob Herring <robh@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, 
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	linux-pci@...r.kernel.org, linux-block@...r.kernel.org, 
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/5] rust: enable `clippy::ptr_as_ptr` lint

On Wed, Mar 12, 2025 at 10:40 AM Benno Lossin <benno.lossin@...ton.me> wrote:
>
> On Sun Mar 9, 2025 at 5:00 PM CET, Tamir Duberstein wrote:
> > In Rust 1.51.0, Clippy introduced the `ptr_as_ptr` lint [1]:
> >
> >> Though `as` casts between raw pointers are not terrible,
> >> `pointer::cast` is safer because it cannot accidentally change the
> >> pointer's mutability, nor cast the pointer to other types like `usize`.
> >
> > There are a few classes of changes required:
> > - Modules generated by bindgen are marked
> >   `#[allow(clippy::ptr_as_ptr)]`.
> > - Inferred casts (` as _`) are replaced with `.cast()`.
> > - Ascribed casts (` as *... T`) are replaced with `.cast::<T>()`.
> > - Multistep casts from references (` as *const _ as *const T`) are
> >   replaced with `let x: *const _ = &x;` and `.cast()` or `.cast::<T>()`
>
> Similarly to the other patch, this could be `let x = &raw x;`. (but it's
> fine to leave it as-is for now, we can also make that a
> good-first-issue.)

Yeah, same as the other patch; we can't directly do that here without
introducing some compiler infra or bumping MSRV.

> >   according to the previous rules. The intermediate `let` binding is
> >   required because `(x as *const _).cast::<T>()` results in inference
> >   failure.
> > - Native literal C strings are replaced with `c_str!().as_char_ptr()`.
> >
> > Apply these changes and enable the lint -- no functional change
> > intended.
> >
> > Link: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_as_ptr [1]
> > Signed-off-by: Tamir Duberstein <tamird@...il.com>
>
> Reviewed-by: Benno Lossin <benno.lossin@...ton.me>

Thanks!