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From:   Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date:   Sat, 17 Apr 2021 17:38:56 +0200
Message-ID: <CANiq72=G+JdHiLovGv=5Yi_7smyrinWFfEQH31x=KPP4=nKKGQ@mail.gmail.com>
Subject: Re: [PATCH 04/13] Kbuild: Rust support
To:     Willy Tarreau <w@1wt.eu>
Cc:     Connor Kuehl <ckuehl@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Miguel Ojeda <ojeda@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux <rust-for-linux@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Geoffrey Thomas <geofft@ldpreload.com>,
        Finn Behrens <me@kloenk.de>,
        Adam Bratschi-Kaye <ark.email@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        Michael Ellerman <mpe@ellerman.id.au>
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On Sat, Apr 17, 2021 at 6:24 AM Willy Tarreau <w@1wt.eu> wrote:
>
> My concern was to know what field to look at to reliably detect an error
> from the C side after a sequence doing C -> Rust -> C when the inner C
> code uses NULL to mark an error and the upper C code uses NULL as a valid
> value and needs to look at an error code instead to rebuild a result. But

I see, thanks for clarifying. I don't think we want to change anything
on either of the C sides (at least for the foreseeable future). So the
Rust code in-between must respect whatever conventions both C sides
already use, even if they happen to be different on each side.

Thus the C side will not know there was a `Result` inside the Rust
side and so it does not need to worry about which field to look at.

Cheers,
Miguel