linux-kernel - Re: [PATCH RESEND v5] rust: str: Use `core::CStr`, remove the custom `CStr` implementation

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Message-ID: <CAH5fLghOFYxwCOGrk8NYX0V9rgrJJ70YOa+dY1O0pbNB-CoK=w@mail.gmail.com>
Date: Wed, 21 Aug 2024 14:08:44 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Michal Rostecki <vadorovsky@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, 
	Brendan Higgins <brendan.higgins@...ux.dev>, David Gow <davidgow@...gle.com>, 
	Rae Moar <rmoar@...gle.com>, FUJITA Tomonori <fujita.tomonori@...il.com>, 
	Trevor Gross <tmgross@...ch.edu>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, Martin Rodriguez Reboredo <yakoyoku@...il.com>, 
	Finn Behrens <me@...enk.dev>, Manmohan Shukla <manmshuk@...il.com>, 
	Valentin Obst <kernel@...entinobst.de>, Yutaro Ohno <yutaro.ono.418@...il.com>, 
	Asahi Lina <lina@...hilina.net>, Danilo Krummrich <dakr@...hat.com>, Tiago Lam <tiagolam@...il.com>, 
	Charalampos Mitrodimas <charmitro@...teo.net>, Tejun Heo <tj@...nel.org>, Roland Xu <mu001999@...look.com>, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com, 
	netdev@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH RESEND v5] rust: str: Use `core::CStr`, remove the custom
 `CStr` implementation

On Mon, Aug 19, 2024 at 5:39 PM Michal Rostecki <vadorovsky@...il.com> wrote:
>
> From: Michal Rostecki <vadorovsky@...il.com>
>
> `CStr` became a part of `core` library in Rust 1.75. This change replaces
> the custom `CStr` implementation with the one from `core`.
>
> `core::CStr` behaves generally the same as the removed implementation,
> with the following differences:
>
> - It does not implement `Display`.
> - It does not provide `from_bytes_with_nul_unchecked_mut` method.
> - It has `as_ptr()` method instead of `as_char_ptr()`, which also returns
>   `*const c_char`.
>
> The first two differences are handled by providing the `CStrExt` trait,
> with `display()` and `from_bytes_with_nul_unchecked_mut()` methods.
> `display()` returns a `CStrDisplay` wrapper, with a custom `Display`
> implementation.
>
> `DerefMut` implementation for `CString` is removed here, as it's not
> being used anywhere.
>
> Signed-off-by: Michal Rostecki <vadorovsky@...il.com>

A few comments:

* I would probably add CStrExt to the kernel prelude.
* I would probably remove `from_bytes_with_nul_unchecked_mut` and keep
`DerefMut for CString` instead of the other way around.
* Perhaps we should remove the `c_str!` macro and use c"" instead?

Alice