linux-kernel - Re: [PATCH 04/13] Kbuild: Rust support

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Date:   Fri, 16 Apr 2021 23:19:18 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Willy Tarreau <w@....eu>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux@...r.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Geoffrey Thomas <geofft@...reload.com>,
        Finn Behrens <me@...enk.de>,
        Adam Bratschi-Kaye <ark.email@...il.com>,
        Wedson Almeida Filho <wedsonaf@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 04/13] Kbuild: Rust support

On Fri, Apr 16, 2021 at 10:22 PM Willy Tarreau <w@....eu> wrote:
>
> So it simply does the equivalent of:
>
>   struct result {
>      int status;
>      int error;
>   };

Not exactly, it is more like a tagged union, as Connor mentioned.

However, and this is the critical bit: it is a compile-time error to
access the inactive variants (in safe code). In C, it is on you to
keep track which one is the current one.

>      kill_foo();   // only for rust, C doesn't need it

Please note that `kill_foo()` is not needed in Rust -- it was an
example of possible cleanup (since Al mentioned resources/cleanup)
using RAII.

Cheers,
Miguel