Re: [PATCH 4/5] rust: alloc: add Vec::clear

Alice Ryhl
2025-03-12T07:05:17Z

On Tue, Mar 11, 2025 at 03:40:51PM +0100, Danilo Krummrich wrote:
> On Tue, Mar 11, 2025 at 02:25:15PM +0000, Alice Ryhl wrote:
> > Our custom Vec type is missing the stdlib method `clear`, thus add it.
> > It will be used in the miscdevice sample.
> >
> > Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> > ---
> > rust/kernel/alloc/kvec.rs | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
> > index ae9d072741cedbb34bed0be0c20cc75472aa53be..2d213ede2873cef87116a5527e8e24008c970a58 100644
> > --- a/rust/kernel/alloc/kvec.rs
> > +++ b/rust/kernel/alloc/kvec.rs
> > @@ -395,6 +395,33 @@ pub fn into_raw_parts(self) -> (*mut T, usize, usize) {
> > (ptr, len, capacity)
> > }
> >
> > + /// Clears the vector, removing all values.
> > + ///
> > + /// Note that this method has no effect on the allocated capacity
> > + /// of the vector.
> > + ///
> > + /// # Examples
> > + ///
> > + /// ```
> > + /// let mut v = kernel::kvec![1, 2, 3]?;
> > + ///
> > + /// v.clear();
> > + ///
> > + /// assert!(v.is_empty());
> > + /// # Ok::<(), Error>(())
> > + /// ```
> > + #[inline]
> > + pub fn clear(&mut self) {
> > + let elems: *mut [T] = self.as_mut_slice();
> > +
> > + // INVARIANT: This call changes the number of elements to zero.
> > + self.len = 0;
>
> Please use self.set_len() instead, such that we have to cover all safety
> requirements enforced by self.set_len().

Will do.

> With that,
>
> Acked-by: Danilo Krummrich <dakr@kernel.org> # for char-misc
>
> in case you want to take it through the char-misc tree.
>
> Ironically, self.set_len() lacks your invariant comment and corresponding safety
> requirement, I will send a patch to fix this up, unless you want to. :-)

Go for it.

Alice