Messages in this thread Patch in this message |  | | From | Wedson Almeida Filho <> | Date | Fri, 16 Dec 2022 18:26:57 +0000 | Subject | Re: [PATCH] rust: kernel: drop repetition in offset_of macro |
| |
On Fri, 16 Dec 2022 at 17:49, Wei Liu <wei.liu@kernel.org> wrote: > > It doesn't make sense to allow multiple fields to be specified in > offset_of.
Why do you say it doesn't make sense?
Here's what I had in mind: ``` struct Y { z: u32 } struct X { y: Y } offset_of!(X, y.z) ```
Which is something very plausible.
> No functional change. > > Signed-off-by: Wei Liu <wei.liu@kernel.org> > --- > Cc: Miguel Ojeda <ojeda@kernel.org> > Cc: Alex Gaynor <alex.gaynor@gmail.com> > Cc: Wedson Almeida Filho <wedsonaf@gmail.com> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Gary Guo <gary@garyguo.net> > Cc: Björn Roy Baron <bjorn3_gh@protonmail.com> > --- > rust/kernel/lib.rs | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs > index 6a322effa60c..2f3601e4e27e 100644 > --- a/rust/kernel/lib.rs > +++ b/rust/kernel/lib.rs > @@ -208,7 +208,7 @@ impl<'a> Drop for KParamGuard<'a> { > /// ``` > #[macro_export] > macro_rules! offset_of { > - ($type:ty, $($f:tt)*) => {{ > + ($type:ty, $f:tt) => {{ > let tmp = core::mem::MaybeUninit::<$type>::uninit(); > let outer = tmp.as_ptr(); > // To avoid warnings when nesting `unsafe` blocks. > @@ -216,12 +216,14 @@ macro_rules! offset_of { > // SAFETY: The pointer is valid and aligned, just not initialised; `addr_of` ensures that > // we don't actually read from `outer` (which would be UB) nor create an intermediate > // reference. > - let inner = unsafe { core::ptr::addr_of!((*outer).$($f)*) } as *const u8; > + let inner = unsafe { core::ptr::addr_of!((*outer).$f) } as *const u8; > // To avoid warnings when nesting `unsafe` blocks. > #[allow(unused_unsafe)] > // SAFETY: The two pointers are within the same allocation block. > - unsafe { inner.offset_from(outer as *const u8) } > - }} > + unsafe { > + inner.offset_from(outer as *const u8) > + } > + }}; > } > > /// Produces a pointer to an object from a pointer to one of its fields. > -- > 2.35.1 >
|  |