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Subject: Re: [PATCH 04/13] Kbuild: Rust support
To:     Willy Tarreau <w@1wt.eu>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc:     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@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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 <20210416202215.GA11236@1wt.eu>
From:   Connor Kuehl <ckuehl@redhat.com>
Message-ID: <efe80452-fac9-247a-1e2b-a73553f605e8@redhat.com>
Date:   Fri, 16 Apr 2021 15:34:50 -0500
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On 4/16/21 3:22 PM, Willy Tarreau wrote:
> So it simply does the equivalent of:
> 
>   #define EINVAL -1234
> 
>   struct result {
>      int status;
>      int error;
>   };

Result and Option types are more like a union with a tag that
describes which variant it is.

struct foo_result {
    /* if ok, then access foo_or_err.successful_foo
     *        else, access foo_or_err.error
     */
    bool ok;
    union {
        struct foo successful_foo;
        int error;
    } foo_or_err;
};

> [..]
> 
> So it simply returns a pair of values instead of a single one, which

It will only return 1 value.