From: Alice Ryhl <aliceryhl@google.com>
To: Trevor Gross <tmgross@umich.edu>
Cc: mattgilbride@google.com, "Miguel Ojeda" <ojeda@kernel.org>,
"Alex Gaynor" <alex.gaynor@gmail.com>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Boqun Feng" <boqun.feng@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <benno.lossin@proton.me>,
"Andreas Hindborg" <a.hindborg@samsung.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Arve Hjønnevåg" <arve@android.com>,
"Todd Kjos" <tkjos@android.com>,
"Martijn Coenen" <maco@android.com>,
"Joel Fernandes" <joel@joelfernandes.org>,
"Carlos Llamas" <cmllamas@google.com>,
"Suren Baghdasaryan" <surenb@google.com>,
"Christian Brauner" <brauner@kernel.org>,
"Rob Landley" <rob@landley.net>,
"Davidlohr Bueso" <dave@stgolabs.net>,
"Michel Lespinasse" <michel@lespinasse.org>,
rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/6] rust: add `container_of!` macro
Date: Mon, 12 Feb 2024 10:56:43 +0100 [thread overview]
Message-ID: <CAH5fLgjP98pS1wsP=YXP5Yr79Y62VF7XPKjbj+G75B3SOFt80g@mail.gmail.com> (raw)
In-Reply-To: <CALNs47vgryKctpsP9EV_SsVF8TX8kfwzQ4KCLy9vr5FS_vBq6A@mail.gmail.com>
On Sat, Feb 10, 2024 at 9:05 AM Trevor Gross <tmgross@umich.edu> wrote:
>
> On Mon, Feb 5, 2024 at 9:50 AM <mattgilbride@google.com> wrote:
> > +macro_rules! container_of {
> > + ($ptr:expr, $type:ty, $($f:tt)*) => {{
> > + let ptr = $ptr as *const _ as *const u8;
> > + let offset: usize = ::core::mem::offset_of!($type, $($f)*);
>
> `offset_of` will be stable in 1.77 BUT only for a single field [1]. I
> don't know if there are other blockers in the kernel already, but if
> this could be changed to call `offset_of!` recursively then it will
> work with the stable version.
>
> We might want an `offset_of_many!(a, b, c)` macro somewhere if there
> are other places that need this nesting.
>
> [1]: https://github.com/rust-lang/rust/pull/118799
Rust Binder *does* need that in one place. Creating a nested
offset_of! is kind of tricky, because you have to fail to compile when
you're following a pointer with the Deref trait. I haven't figured out
how to do that yet.
> > + ptr.sub(offset) as *const $type
>
> Instead of casting to and from `u8`, you should be able to use `byte_sub`
Casting to and from u8 also has the side-effect of making it not work
when the target type is !Sized. Not allowing this might be desirable.
Alice
next prev parent reply other threads:[~2024-02-12 9:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-05 15:50 [PATCH 0/6] Red-black tree abstraction needed by Rust Binder mattgilbride
2024-02-05 15:50 ` [PATCH 1/6] rust: add `container_of!` macro mattgilbride
2024-02-09 13:10 ` Alice Ryhl
2024-02-10 8:05 ` Trevor Gross
2024-02-12 9:56 ` Alice Ryhl [this message]
2024-02-05 15:50 ` [PATCH 2/6] rust: rbtree: add red-black tree implementation backed by the C version mattgilbride
2024-02-09 13:04 ` Alice Ryhl
2024-02-05 15:50 ` [PATCH 3/6] rust: rbtree: add `RBTreeIterator` mattgilbride
2024-02-09 13:06 ` Alice Ryhl
2024-02-05 15:50 ` [PATCH 4/6] rust: rbtree: add `RBTreeIteratorMut` mattgilbride
2024-02-09 13:06 ` Alice Ryhl
2024-02-05 15:50 ` [PATCH 5/6] rust: rbtree: add `RBTreeCursor` mattgilbride
2024-02-09 13:06 ` Alice Ryhl
2024-02-05 15:50 ` [PATCH 6/6] rust: rbtree: add `RBTree::entry` mattgilbride
2024-02-09 13:07 ` Alice Ryhl
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