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Date:   Thu, 18 May 2023 11:51:40 -0300
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From:   Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Subject: Re: [PATCH v1 2/7] rust: add offset_of! macro
To:     Alice Ryhl <aliceryhl@google.com>, rust-for-linux@vger.kernel.org
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Tejun Heo <tj@kernel.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=c3=b6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
References: <20230517203119.3160435-1-aliceryhl@google.com>
 <20230517203119.3160435-3-aliceryhl@google.com>
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On 5/17/23 17:31, Alice Ryhl wrote:
> From: Wedson Almeida Filho <walmeida@microsoft.com>
> 
> This macro is used to compute the offset of a field in a struct.
> 
> This commit enables two unstable features that are necessary for using
> the macro in a constant. However, this is not a problem as the macro
> will become available from the Rust standard library soon [1]. The
> unstable features can be disabled again once that happens.
> 
> The macro in this patch does not support sub-fields. That is, you cannot
> write `offset_of!(MyStruct, field.sub_field)` to get the offset of
> `sub_field` with `field`'s type being a struct with a field called
> `sub_field`. This is because `field` might be a `Box<SubStruct>`, which
> means that you would be trying to compute the offset to something in an
> entirely different allocation. There's no easy way to fix the current
> macro to support subfields, but the version being added to the standard
> library should support it, so the limitation is temporary and not a big
> deal.
> 
> Link: https://github.com/rust-lang/rust/issues/106655 [1]
> Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
> Co-developed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
> [...]

Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>