linux-kernel - Re: [PATCH v2 11/12] rust: init: add `{pin_}chain` functions to `{Pin}Init<T, E>`

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Message-ID: <e02b8645-4284-7573-966a-6b6654d4a772@proton.me>
Date:   Mon, 24 Jul 2023 21:55:07 +0000
From:   Benno Lossin <benno.lossin@...ton.me>
To:     Martin Rodriguez Reboredo <yakoyoku@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Alex Gaynor <alex.gaynor@...il.com>
Cc:     Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Alice Ryhl <aliceryhl@...gle.com>,
        Andreas Hindborg <nmi@...aspace.dk>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        Asahi Lina <lina@...hilina.net>
Subject: Re: [PATCH v2 11/12] rust: init: add `{pin_}chain` functions to `{Pin}Init<T, E>`

On 7/24/23 18:07, Martin Rodriguez Reboredo wrote:
> On 7/24/23 11:08, Benno Lossin wrote:
>> This is a bit confusing to me, because dropping the value on returning `Err`
>> is a safety requirement of `PinInit`. Could you elaborate why this is
>> surprising? I can of course add it to the documentation, but I do not see
>> how it could be implemented differently. Since if you do not drop the value
>> here, nobody would know that it is still initialized.
> 
> I knew about the requirement of dropping on `Err`, but what has caught my
> attention is that `{pin_}chain` might not abide with it per the doc
> comment as it says that `self` is initialized before calling `f`...
> 
>       /// First initializes the value using `self` then calls the function
>       /// `f` with the initialized value.
> 
> But one can not know what would happen when `f` fails, specially if
> such failure can be ignored or it's only temporarily.
> 
> So then, the best course IMO is to mention that in some way the value is
> still being initialized, kinda setting it up, and that it will be dropped
> when an error is returned. WDYT?

I see, then I will just expand the documentation.

-- 
Cheers,
Benno