Messages in this thread | | | Date | Fri, 24 Mar 2023 08:39:35 +0000 | From | Benno Lossin <> | Subject | Re: [PATCH v2 3/5] rust: add pin-init API |
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On 23.03.23 07:30, Boqun Feng wrote: > On Tue, Mar 21, 2023 at 07:50:00PM +0000, Benno Lossin wrote: > [...] >> +/// # Syntax >> +/// >> +/// As already mentioned in the examples above, inside of `pin_init!` a `struct` initializer with >> +/// the following modifications is expected: >> +/// - Fields that you want to initialize in-place have to use `<-` instead of `:`. >> +/// - In front of the initializer you can write `&this in` to have access to a [`NonNull<Self>`] >> +/// pointer named `this` inside of the initializer. >> +/// >> +/// For instance: >> +/// >> +/// ```rust >> +/// # use kernel::pin_init; >> +/// # use macros::pin_data; >> +/// # use core::{ptr::addr_of_mut, marker::PhantomPinned}; >> +/// #[pin_data] >> +/// struct Buf { >> +/// ptr: *mut u8, >> +/// buf: [u8; 64], > > Say we have an extra field, > > a: u8, > >> +/// #[pin] >> +/// pin: PhantomPinned, >> +/// } >> +/// pin_init!(&this in Buf { >> +/// buf: [0; 64], >> +/// ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() }, > > And I think we want to disallow: > > a: unsafe { (*addr_of!(*this.as_ptr().buf))[0] } > > , right? Because we don't want `pin_init!` to provide any initialization > order guarantee? If so, maybe add one or two sentences to call it out. > > If not sure, I think we can leave it as it is, until someone really uses > this pattern ;-)
The `pin_init!` macro initializes everything in the order specified, so if `a` is the last field you initialize, the code above is fine. I think we could guarantee this. I will add a comment.
-- Cheers, Benno
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