From: Paolo Bonzini <pbonzini@redhat.com>
To: Junjie Mao <junjie.mao@hotmail.com>
Cc: qemu-devel@nongnu.org, manos.pitsidianakis@linaro.org,
zhao1.liu@intel.com, berrange@redhat.com
Subject: Re: [PATCH 15/23] rust: introduce alternative implementation of offset_of!
Date: Mon, 4 Nov 2024 17:03:10 +0100 [thread overview]
Message-ID: <f13766c1-12e2-46b2-a139-c926824c50e0@redhat.com> (raw)
In-Reply-To: <SY0P300MB1026D525F3022164941671B895502@SY0P300MB1026.AUSP300.PROD.OUTLOOK.COM>
On 11/3/24 10:54, Junjie Mao wrote:
>
> Paolo Bonzini <pbonzini@redhat.com> writes:
>
>> From: Junjie Mao <junjie.mao@hotmail.com>
>>
>> offset_of! was stabilized in Rust 1.77.0. Use an alternative implemenation
>> that was found on the Rust forums, and whose author agreed to license as
>> MIT for use in QEMU.
>>
>> The alternative allows only one level of field access, but apart
>> from this can be used just by replacing core::mem::offset_of! with
>> qemu_api::offset_of!.
>>
>> The actual implementation of offset_of! is done in a declarative macro,
>> but for simplicity and to avoid introducing an extra level of indentation,
>> the trigger is a procedural macro #[derive(offsets)].
>>
>> The procedural macro is perhaps a bit overengineered, but it helps
>> introducing some idioms that will be useful in the future as well.
>>
>> Signed-off-by: Junjie Mao <junjie.mao@hotmail.com>
>> Co-developed-by: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>
> Generally looks good to me. Thanks for integrating this!
>
> It seems Rust does not have builtin support for unit tests expecting
> compilation failures. There is a crate (named trybuild [1]) for that
> purpose but it requires introducing a dozen of new dependencies (see
> below). Do you think it worth the effort? If so, I can take a closer
> look and cook something for initial review (probably post 9.2).
>
> trybuild v1.0.101
> ├── glob v0.3.1
> ├── serde v1.0.210
> ├── serde_derive v1.0.210 (proc-macro)
> │ ├── proc-macro2 v1.0.84 (*)
> │ ├── quote v1.0.36 (*)
> │ └── syn v2.0.66 (*)
> ├── serde_json v1.0.132
> │ ├── itoa v1.0.11
> │ ├── memchr v2.7.4
> │ ├── ryu v1.0.18
> │ └── serde v1.0.210
> ├── target-triple v0.1.3
> ├── termcolor v1.4.1
> └── toml v0.8.19
> ├── serde v1.0.210
> ├── serde_spanned v0.6.8
> │ └── serde v1.0.210
> ├── toml_datetime v0.6.8
> │ └── serde v1.0.210
> └── toml_edit v0.22.22
> ├── indexmap v2.6.0
> │ ├── equivalent v1.0.1
> │ └── hashbrown v0.15.0
> ├── serde v1.0.210
> ├── serde_spanned v0.6.8 (*)
> ├── toml_datetime v0.6.8 (*)
> └── winnow v0.6.20
>
> [1] https://docs.rs/trybuild/latest/trybuild/
>
> [snip]
>> diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib.rs
>> index a4bc5d01ee8..c2ea22101e4 100644
>> --- a/rust/qemu-api-macros/src/lib.rs
>> +++ b/rust/qemu-api-macros/src/lib.rs
>> @@ -3,8 +3,34 @@
>> // SPDX-License-Identifier: GPL-2.0-or-later
>>
>> use proc_macro::TokenStream;
>> -use quote::quote;
>> -use syn::{parse_macro_input, DeriveInput};
>> +use proc_macro2::Span;
>> +use quote::{quote, quote_spanned};
>> +use syn::{
>> + parse_macro_input, parse_quote, punctuated::Punctuated, token::Comma, Data, DeriveInput, Field,
>> + Fields, Ident, Type, Visibility,
>> +};
>> +
>> +struct CompileError(String, Span);
>> +
>> +impl From<CompileError> for proc_macro2::TokenStream {
>> + fn from(err: CompileError) -> Self {
>> + let CompileError(msg, span) = err;
>> + quote_spanned! { span => compile_error!(#msg); }
>
> The documentation [2] says "there should be no space before the =>
> token" and that is by intention to tell that `span` is "evaluated in the
> context of proc macro" while those after the arm "in the generated
> code". Should we follow that convention (even though the extra white
> space does not impact building)?
Ah, forgot to reply about this. Personally I think it's clear enough
with the "=>", but if there's agreement on removing the space I don't
oppose it.
Paolo
next prev parent reply other threads:[~2024-11-04 16:03 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-25 16:01 [PATCH v3 00/23] rust: fix CI + allow older versions of rustc and bindgen Paolo Bonzini
2024-10-25 16:01 ` [PATCH 01/23] rust: add definitions for vmstate Paolo Bonzini
2024-10-25 16:01 ` [PATCH 02/23] rust/pl011: fix default value for migrate-clock Paolo Bonzini
2024-10-25 16:01 ` [PATCH 03/23] rust/pl011: add support for migration Paolo Bonzini
2024-10-25 16:01 ` [PATCH 04/23] rust/pl011: move CLK_NAME static to function scope Paolo Bonzini
2024-10-25 16:01 ` [PATCH 05/23] rust/pl011: add TYPE_PL011_LUMINARY device Paolo Bonzini
2024-10-31 14:58 ` Zhao Liu
2024-10-25 16:01 ` [PATCH 06/23] rust/pl011: remove commented out C code Paolo Bonzini
2024-10-25 16:01 ` [PATCH 07/23] rust/pl011: Use correct masks for IBRD and FBRD Paolo Bonzini
2024-10-25 16:01 ` [PATCH 08/23] rust: patch bilge-impl to allow compilation with 1.63.0 Paolo Bonzini
2024-10-25 16:01 ` [PATCH 09/23] rust: fix cfgs of proc-macro2 for 1.63.0 Paolo Bonzini
2024-10-25 16:01 ` [PATCH 10/23] rust: use std::os::raw instead of core::ffi Paolo Bonzini
2024-10-25 16:01 ` [PATCH 11/23] rust: introduce a c_str macro Paolo Bonzini
2024-10-31 10:39 ` Zhao Liu
2024-10-25 16:01 ` [PATCH 12/23] rust: silence unknown warnings for the sake of old compilers Paolo Bonzini
2024-10-25 16:01 ` [PATCH 13/23] rust: synchronize dependencies between subprojects and Cargo.lock Paolo Bonzini
2024-10-31 11:31 ` Zhao Liu
2024-11-01 10:14 ` Junjie Mao
2024-11-01 15:30 ` Paolo Bonzini
2024-11-02 2:13 ` Junjie Mao
2024-10-25 16:01 ` [PATCH 14/23] rust: create a cargo workspace Paolo Bonzini
2024-10-31 13:46 ` Zhao Liu
2024-11-01 10:21 ` Junjie Mao
2024-10-25 16:02 ` [PATCH 15/23] rust: introduce alternative implementation of offset_of! Paolo Bonzini
2024-11-03 9:54 ` Junjie Mao
2024-11-04 16:02 ` Paolo Bonzini
2024-11-04 16:03 ` Paolo Bonzini [this message]
2024-11-04 16:03 ` Paolo Bonzini
2024-11-05 2:07 ` Junjie Mao
2024-10-25 16:02 ` [PATCH 16/23] rust: do not use MaybeUninit::zeroed() Paolo Bonzini
2024-10-25 16:02 ` [PATCH 17/23] rust: clean up detection of the language Paolo Bonzini
2024-10-25 16:02 ` [PATCH 18/23] rust: allow version 1.63.0 of rustc Paolo Bonzini
2024-10-25 16:02 ` [PATCH 19/23] rust: do not use --generate-cstr Paolo Bonzini
2024-10-25 20:03 ` Michael Tokarev
2024-10-25 20:06 ` Pierrick Bouvier
2024-10-25 20:10 ` Michael Tokarev
2024-10-25 20:12 ` Pierrick Bouvier
2024-10-25 20:11 ` Paolo Bonzini
2024-10-25 16:02 ` [PATCH 20/23] rust: allow older version of bindgen Paolo Bonzini
2024-10-25 16:02 ` [PATCH 21/23] rust: make rustfmt optional Paolo Bonzini
2024-10-25 16:02 ` [PATCH 22/23] dockerfiles: install bindgen from cargo on Ubuntu 22.04 Paolo Bonzini
2024-10-25 18:51 ` Pierrick Bouvier
2024-10-25 19:35 ` Paolo Bonzini
2024-10-25 19:47 ` Pierrick Bouvier
2024-10-25 20:08 ` Paolo Bonzini
2024-10-25 20:14 ` Pierrick Bouvier
2024-10-25 20:21 ` Paolo Bonzini
2024-10-25 20:08 ` Pierrick Bouvier
2024-10-25 16:02 ` [PATCH 23/23] ci: enable rust in the Debian and Ubuntu system build job Paolo Bonzini
2024-10-25 18:55 ` Pierrick Bouvier
2024-10-25 18:58 ` Pierrick Bouvier
2024-10-25 19:27 ` Paolo Bonzini
2024-10-25 19:33 ` Pierrick Bouvier
2024-10-25 20:08 ` Pierrick Bouvier
2024-10-25 16:23 ` [PATCH v3 00/23] rust: fix CI + allow older versions of rustc and bindgen Manos Pitsidianakis
2024-10-31 16:28 ` Paolo Bonzini
2024-10-27 7:01 ` Michael Tokarev
2024-10-27 8:00 ` Paolo Bonzini
2024-10-27 9:38 ` Michael Tokarev
2024-10-27 9:42 ` Michael Tokarev
2024-10-27 9:57 ` Michael Tokarev
2024-10-27 12:39 ` Paolo Bonzini
2024-10-28 9:21 ` Daniel P. Berrangé
2024-10-28 12:26 ` Alex Bennée
2024-10-28 12:41 ` Paolo Bonzini
2024-10-30 16:52 ` Paolo Bonzini
2024-10-31 16:41 ` Zhao Liu
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