linux-kernel - Re: [PATCH v3 1/4] rust: alloc: add Vec::len() <= Vec::capacity invariant

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Message-ID: <CAH5fLgh+DsT0=6mxbX+=bx2rb7y35a2cSeg=0FqaO-FgTJ4tEw@mail.gmail.com>
Date: Wed, 16 Apr 2025 16:41:28 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Tamir Duberstein <tamird@...il.com>
Cc: Danilo Krummrich <dakr@...nel.org>, Andrew Ballance <andrewjballance@...il.com>, 
	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>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] rust: alloc: add Vec::len() <= Vec::capacity invariant

On Mon, Apr 7, 2025 at 4:52 PM Tamir Duberstein <tamird@...il.com> wrote:
>
> Document the invariant that the vector's length is always less than or
> equal to its capacity. This is already implied by these other
> invariants:
>
> - `self.len` always represents the exact number of elements stored in
>   the vector.
> - `self.layout` represents the absolute number of elements that can be
>   stored within the vector without re-allocation.
>
> but it doesn't hurt to spell it out. Note that the language references
> `self.capacity` rather than `self.layout.len` as the latter is zero for
> a vector of ZSTs.
>
> Update a safety comment touched by this patch to correctly reference
> `realloc` rather than `alloc` and replace "leaves" with "leave" to
> improve grammar.
>
> Signed-off-by: Tamir Duberstein <tamird@...il.com>

This change has a conflict with the spare_capacity_mut patch in alloc-next.

Alice