linux-kernel - Re: [PATCH v3] rust: check type of `$ptr` in `container

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Message-ID: <aAtbAVW8XXHTdDBe@google.com>
Date: Fri, 25 Apr 2025 09:50:57 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Tamir Duberstein <tamird@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...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@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] rust: check type of `$ptr` in `container_of!`

On Thu, Apr 24, 2025 at 09:47:52AM -0400, Tamir Duberstein wrote:
> > > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> > > index 1df11156302a..d14ed86efb68 100644
> > > --- a/rust/kernel/lib.rs
> > > +++ b/rust/kernel/lib.rs
> > > @@ -198,9 +198,15 @@ fn panic(info: &core::panic::PanicInfo<'_>) -> ! {
> > >  /// ```
> > >  #[macro_export]
> > >  macro_rules! container_of {
> > > -    ($ptr:expr, $type:ty, $($f:tt)*) => {{
> > > -        let offset: usize = ::core::mem::offset_of!($type, $($f)*);
> > > -        $ptr.byte_sub(offset).cast::<$type>()
> > > +    ($field_ptr:expr, $Container:ty, $($fields:tt)*) => {{
> >
> > It's rather unusual to use an uppercase C in the name of this parameter.
> 
> I took the parameter name from `offset_of`:
> https://doc.rust-lang.org/stable/std/mem/macro.offset_of.html.

https://github.com/rust-lang/rust/pull/140285