linux-kernel - Re: [PATCH 04/19] rust: enable `clippy::undocumented_unsafe

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Message-ID: <CANiq72kEMtB8SBeTJKtRhw5stwieq6ULk6N_X4dyDcCz_2mDag@mail.gmail.com>
Date: Thu, 3 Oct 2024 20:45:40 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Trevor Gross <tmgross@...ch.edu>
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>, 
	Alice Ryhl <aliceryhl@...gle.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH 04/19] rust: enable `clippy::undocumented_unsafe_blocks` lint

On Sun, Sep 29, 2024 at 6:33 AM Trevor Gross <tmgross@...ch.edu> wrote:
>
> There are a couple places where the attributes move like this - did
> this come from an older clippy version? clippy used to warn about this
> but accepts it by default since [1]. (Still works of course, I just
> think it looks nicer to have the attributes next to their statements).

I started this series about a long time ago, but I don't think old
Clippy is the reason -- I took a look again at this a couple months
ago and created this issue about it due to these lines of code,
including some examples and test cases:

    https://github.com/rust-lang/rust-clippy/issues/13189

For instance:

    // SAFETY: ...
    #[allow(clippy::unnecessary_cast)]
    return Err(unsafe { Error::from_errno_unchecked(err as core::ffi::c_int) });

This will not work, i.e. it does not see the `// SAFETY:`. However,
putting the `#[allow]` on top to let the comment be closer will work
(like in the patch). This will also work:

    return Err(
        // SAFETY: ...
        #[allow(clippy::unnecessary_cast)]
        unsafe { Error::from_errno_unchecked(err as core::ffi::c_int) }
    );

There has been no reply in the issue so far, but if you have any
comments/insights on whether those cases should or should not work,
that would be great.

Cheers,
Miguel