On Mon, Feb 23, 2026 at 2:13 AM Joel Fernandes <[email protected]> wrote: > > Hi Eliot, > > On 2/20/2026 3:16 AM, Eliot Courtney wrote: > > On Thu Feb 19, 2026 at 5:55 AM JST, Joel Fernandes wrote: > >> +/// Create a C doubly-circular linked list interface `CList` from a raw > >> `list_head` pointer. > >> +/// > >> +/// This macro creates a `CList<T, OFFSET>` that can iterate over items > >> of type `$rust_type` > >> +/// linked via the `$field` field in the underlying C struct `$c_type`. > >> +/// > >> +/// # Arguments > >> +/// > >> +/// - `$head`: Raw pointer to the sentinel `list_head` object (`*mut > >> bindings::list_head`). > >> +/// - `$rust_type`: Each item's rust wrapper type. > >> +/// - `$c_type`: Each item's C struct type that contains the embedded > >> `list_head`. > >> +/// - `$field`: The name of the `list_head` field within the C struct. > >> +/// > >> +/// # Safety > >> +/// > >> +/// This is an unsafe macro. The caller must ensure: > >> +/// > >> +/// - `$head` is a valid, initialized sentinel `list_head` pointing to a > >> list that remains > >> +/// unmodified for the lifetime of the rust `CList`. > >> +/// - The list contains items of type `$c_type` linked via an embedded > >> `$field`. > >> +/// - `$rust_type` is `#[repr(transparent)]` over `$c_type` or has > >> compatible layout. > >> +/// > >> +/// # Examples > >> +/// > >> +/// Refer to the examples in this module's documentation. > >> +#[macro_export] > >> +macro_rules! clist_create { > >> + ($head:expr, $rust_type:ty, $c_type:ty, $($field:tt).+) => {{ > >> + // Compile-time check that field path is a list_head. > >> + let _: fn(*const $c_type) -> *const $crate::bindings::list_head = > >> + |p| &raw const (*p).$($field).+; > >> + > >> + // Calculate offset and create `CList`. > >> + const OFFSET: usize = ::core::mem::offset_of!($c_type, > >> $($field).+); > >> + $crate::ffi::clist::CList::<$rust_type, OFFSET>::from_raw($head) > >> + }}; > >> +} > > > > This uses offset_of! in a way that requires the offset_of_nested > > feature, so it doesn't build in rust 1.78.0. The feature is already > > added to rust_allowed_features, so I think it's ok to add > > #![feature(offset_of_nested)]. > > Maybe I am missing something, but why should the feature be gated behind > that if all compiler versions (>= 1.78) support it either in a stable way > or via an unstable feature flag?
The rust_allowed_features list only applies to drivers and such. It doesn't apply to the Rust crates in the rust/ directory, which need to use #![feature] annotations manually. Alice
