linux-kernel - Re: [PATCH v2 06/12] rust: init: add `..Zeroable::zeroed()` syntax for zeroing all missing fields

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Message-ID: <20230720132540.3543838-1-aliceryhl@google.com>
Date:   Thu, 20 Jul 2023 13:25:40 +0000
From:   Alice Ryhl <aliceryhl@...gle.com>
To:     benno.lossin@...ton.me
Cc:     alex.gaynor@...il.com, aliceryhl@...gle.com,
        bjorn3_gh@...tonmail.com, boqun.feng@...il.com, gary@...yguo.net,
        lina@...hilina.net, linux-kernel@...r.kernel.org, nmi@...aspace.dk,
        ojeda@...nel.org, rust-for-linux@...r.kernel.org,
        wedsonaf@...il.com
Subject: Re: [PATCH v2 06/12] rust: init: add `..Zeroable::zeroed()` syntax
 for zeroing all missing fields

Benno Lossin <benno.lossin@...ton.me> writes:
> Add the struct update syntax to the init macros, but only for
> `..Zeroable::zeroed()`. Adding this at the end of the struct initializer
> allows one to omit fields from the initializer, these fields will be
> initialized with 0x00 set to every byte. Only types that implement the
> `Zeroable` trait can utilize this.
> 
> Suggested-by: Asahi Lina <lina@...hilina.net>
> Signed-off-by: Benno Lossin <benno.lossin@...ton.me>

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>

> +    (make_initializer:
> +        @slot($slot:ident),
> +        @type_name($t:ident),
> +        @munch_fields(..Zeroable::zeroed() $(,)?),
> +        @acc($($acc:tt)*),
> +    ) => {
> +        // Endpoint, nothing more to munch, create the initializer. Since the users specified
> +        // `..Zeroable::zeroed()`, the slot will already have been zeroed and all field that have
> +        // not been overwritten are thus zero and initialized. We still check that all fields are
> +        // actually accessible by using the struct update syntax ourselves.
> +        // Since we are in the `if false` branch, this will never get executed. We abuse `slot` to
> +        // get the correct type inference here:

Didn't you just change it to a closure rather than an `if else`?

Regardless, I'm happy with this change.

Alice