From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2BF0C64ED6 for ; Sun, 26 Feb 2023 20:59:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229585AbjBZU7n (ORCPT ); Sun, 26 Feb 2023 15:59:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56418 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229445AbjBZU7n (ORCPT ); Sun, 26 Feb 2023 15:59:43 -0500 Received: from mail-yw1-x1130.google.com (mail-yw1-x1130.google.com [IPv6:2607:f8b0:4864:20::1130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDFC113D52; Sun, 26 Feb 2023 12:59:37 -0800 (PST) Received: by mail-yw1-x1130.google.com with SMTP id 00721157ae682-53852143afcso125741997b3.3; Sun, 26 Feb 2023 12:59:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=/a3uSDlfsqZGmv0N4D8ujOHHg7vKPERtZBqNuW3pgYs=; b=qHaN8xbcrctTIZLJmLgSzE/JjYY4a5wt8mpHQixH3Cpthj7X6bTegUsDqKK3X0ezqc t+3FqVF1QElwmSLcZPo4U0OLbPpjqX/OOHrr6TrhgQcZA3ObniMc6HOvXCMAcrBx1eKz RCZCnNnTQwADm//81Y/FuvuNZBO/iq7QX4hd87kr4dPO8uS+FrCtjzd+mciO/pW/byUd FGzem7IH+wT96mdSI8IR3w72Xe4yAEwq0JQT4m34E7CxQ5jnY0G/BmhU8mqUmwiXVP19 9vJef43XC0BjzKkLz5kep6z8dJSDCahWVeDymF6Xn6gOrtfX71S7Ht4U5zdwniWh4hCc sCgw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=/a3uSDlfsqZGmv0N4D8ujOHHg7vKPERtZBqNuW3pgYs=; b=GMlMvnjXhgNMWNffEinqS0zBP5ZFW2GpNR1Dgkplvoppx/mDTU4WvkbKFxNh8PWcVU +OeTc7awnD9tHtUITNCd22WwxTSShSGlhsdvuPHa4Jhx/9C8I6Nanv+NOaSQH1hBSE93 X79XLGf9tAD+L59DMeB+xpx/2YsP4JdfZa52iEWgECAhoTaASLAjyjend0eMNdfIYRhy 8t3DMaRZjqfVbtnfLDvUEjex33vP/XrDH2N54ofsXqHHDELuVFDMqiFsXTrQqU328Gen UMj7nbT1yYeFDj6bYu+XachOWQV/3qtp1Ww/5w93MZ4hID5dqzKXyV+OuCc61AmE84Pv w94w== X-Gm-Message-State: AO0yUKUyzHzK0qeCmEYLsA2FQIifVymSG2YccT0fQYMgFOSUc34qEZ3D jSxDsnw4Vj30NWS1EVNifprdVD2CaHpt7asP+to= X-Google-Smtp-Source: AK7set/61TNdgiOUotaSqBJ3oG75bxwjctCYlnS41y9hd20++fxhpwwM2eiH4YykdQu4/DE7h9xuedSgKUzR30dWaCU= X-Received: by 2002:a05:690c:c1a:b0:533:9d13:a067 with SMTP id cl26-20020a05690c0c1a00b005339d13a067mr6032856ywb.3.1677445177037; Sun, 26 Feb 2023 12:59:37 -0800 (PST) MIME-Version: 1.0 References: <20230224-rust-error-v1-0-f8f9a9a87303@asahilina.net> <20230224-rust-error-v1-5-f8f9a9a87303@asahilina.net> <20230225222340.34d749ee.gary@garyguo.net> <20230226133606.583cd1d8.gary@garyguo.net> In-Reply-To: From: Miguel Ojeda Date: Sun, 26 Feb 2023 21:59:25 +0100 Message-ID: Subject: Re: [PATCH 5/5] rust: error: Add from_kernel_result!() macro To: Boqun Feng Cc: Gary Guo , Asahi Lina , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Sven Van Asbroeck , Fox Chen , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, asahi@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: rust-for-linux@vger.kernel.org On Sun, Feb 26, 2023 at 7:17=E2=80=AFPM Boqun Feng w= rote: > > My preference to function instead of macro here is because I want to > avoid the extra level of abstraction and make things explict, so that > users and reviewers can understand the API behavior solely based on > Rust's types, functions and closures: they are simpler than macros, at > least to me ;-) There is one extra problem with the macro: `rustfmt` does not format the contents if called with braces (as we currently do). So when I was cleaning some things up for v8, one of the things I did was run manually `rustfmt` on the blocks by removing the macro invocation, in commit 77a1a8c952e1 ("rust: kernel: apply `rustfmt` to `from_kernel_result!` blocks"). Having said that, it does format it when called with parenthesis wrapping the block, so we could do that if we end up with the macro. > First, I think the macro version here is just a poor-man's try block, in > other words, I'd expect explicit use of try blocks intead of > `from_kernel_result` when the feature is ready. If that's the case, we > need to change the use sites anyway. Yeah, if we eventually get a better language feature that fits well, then we should use it. > Do both implementation share the same behavior? Yeah, a `return` will return to the outer caller in the case of a `try` block, while it returns to the closure (macro) in the other case. Or do you mean something else? In that case, I think one could use use a labeled block to `break` out, not sure if `try` blocks will allow an easier way. We have a case of such a `return` within the closure at `rust/rust` in `file.rs`: from_kernel_result! { let off =3D match whence as u32 { bindings::SEEK_SET =3D> SeekFrom::Start(offset.try_into()?), bindings::SEEK_CUR =3D> SeekFrom::Current(offset), bindings::SEEK_END =3D> SeekFrom::End(offset), _ =3D> return Err(EINVAL), }; ... Ok(off as bindings::loff_t) } Cheers, Miguel