linux-kernel - Re: [PATCH v2 3/4] rust: pci: impl TryFrom<&Device> for &pci::Device

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Message-ID: <CANiq72=s3rQwRt-TOr0_n=EKHwJSQSGmKfu_4TtoEhSTc2Fvqg@mail.gmail.com>
Date: Fri, 21 Mar 2025 19:59:08 +0100
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: kernel test robot <lkp@...el.com>, bhelgaas@...gle.com, gregkh@...uxfoundation.org, 
	rafael@...nel.org, ojeda@...nel.org, alex.gaynor@...il.com, 
	boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com, 
	benno.lossin@...ton.me, a.hindborg@...nel.org, aliceryhl@...gle.com, 
	tmgross@...ch.edu, llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev, 
	linux-pci@...r.kernel.org, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] rust: pci: impl TryFrom<&Device> for &pci::Device

On Fri, Mar 21, 2025 at 6:44 PM Danilo Krummrich <dakr@...nel.org> wrote:
>
> This requires an unsafe block for compilers < 1.82. For compilers >= 1.82 it
> turns into a warning *if* using an unsafe block.
>
> *Not* requiring unsafe for this seems like the correct thing -- was this a
> bugfix in the compiler?
>
> I guess to make it work for all compiler versions supported by the kernel we
> have to use unsafe and suppress the warning?

It was a feature, but it has been fairly annoying -- it affected
several series, e.g. the latest KUnit one as well as:

    https://lore.kernel.org/rust-for-linux/CANiq72kuebpOa4aPxmTXNMA0eo-SLL+Ht9u1SGHymXBF5_92eA@mail.gmail.com/

Please see:

    https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html#safely-addressing-unsafe-statics

So, yeah, we use `allow(unused_unsafe)` (no `expect`, since it depends
on the version).

I hope that helps.

Cheers,
Miguel