Re: [PATCH 5/5] rust: add improved version of `ForeignOwnable::borrow_mut`

[Tamir Duberstein]

On Thu, Oct 31, 2024 at 6:54 AM Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote:
>
> On Wed, Oct 30, 2024 at 9:46 PM Tamir Duberstein <tamird@xxxxxxxxx> wrote:
> >
> > From: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> >
> > Previously, the `ForeignOwnable` trait had a method called `borrow_mut`
> > that was intended to provide mutable access to the inner value. However,
> > the method accidentally made it possible to change the address of the
> > object being modified, which usually isn't what we want. (And when we
> > want that, it can be done by calling `from_foreign` and `into_foreign`,
> > like how the old `borrow_mut` was implemented.)
> >
> > In this patch, we introduce an alternate definition of `borrow_mut` that
> > solves the previous problem. Conceptually, given a pointer type `P` that
> > implements `ForeignOwnable`, the `borrow_mut` method gives you the same
> > kind of access as an `&mut P` would, except that it does not let you
> > change the pointer `P` itself.
> >
> > This is analogous to how the existing `borrow` method provides the same
> > kind of access to the inner value as an `&P`.
> >
> > Note that for types like `Arc`, having an `&mut Arc<T>` only gives you
> > immutable access to the inner `T`. This is because mutable references
> > assume exclusive access, but there might be other handles to the same
> > reference counted value, so the access isn't exclusive. The `Arc` type
> > implements this by making `borrow_mut` return the same type as `borrow`.
> >
> > Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> > Reviewed-by: Boqun Feng <boqun.feng@xxxxxxxxx>
> > Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx>
> > Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx>
>
> You must add your own SoB at the end when resending other's patches.
>
> Alice

Thanks, I'll add it in v2. Does the order matter?