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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 12/4/25 15:15, Zhao Liu wrote: >> diff --git a/rust/util/src/qobject/mod.rs b/rust/util/src/qobject/mod.rs >> new file mode 100644 >> index 00000000000..f43d87a3b66 >> --- /dev/null >> +++ b/rust/util/src/qobject/mod.rs >> @@ -0,0 +1,309 @@ >> +//! `QObject` bindings >> +//! >> +//! This module implements bindings for QEMU's `QObject` data structure. >> +//! The bindings integrate with `serde`, which take the role of visitors >> +//! in Rust code. >> + >> +#![deny(clippy::unwrap_used)] > > Are there are any specific considerations for this lint rule? It ensures that all conversion errors (e.g. from try_into()) are propagated. >> +pub struct QObject(&'static UnsafeCell); > > It seems Opaque<> feels more natural than UnsafeCell<>. > > Opaque::from_raw() requires *mut T, but QObject::from_raw() and > QObject::clone_from_raw() mainly play with C bindings which usually use > *mut pointer. So it seems unnecessary to convert *mut to *const in the > middle. > > And furthermore, I think QObject(Opaque) is better > than QObject(&'static Opaque). From a semantic view, > C's QObject is a struct, while Rust's QObject is a reference, which seems > somewhat mismatched. > > I'm not sure yet if there may be gaps when remove &'static, but it > looks like using &'static Opaque<> instead of &'static UnsafeCell<> is > Okay in code? I am using UnsafeCell because the QObject here is always valid, i.e. MaybeUninit is explicitly not necessary. Opaque explicitly allows it to be invalid, here instead the API is "create via C code or FFI and only then create the QObject". However, while it is possible to use Opaque<> instead of UnsafeCell<>, it is not possible to make this a simple wrapper because QObject is unmovable and reference counted. That is, QObject is the equivalent of (for example) Owned. > These 2 methods are the clone, but it seems they're actually similar to > Owned<>, i.e., increase refcnt when Rust side wants to "own" or ensure > to use this safely. > > However, there indeed isn't a non-object version of Owned for now, so I > think this kind of clone should be okay. Hmm, for long-term, is it > valuable to consider a more generic Owned<>? Linux has ARef<> I think. But it seems overkill for now. >> +impl FromIterator for QObject >> +where >> + Self: From, >> +{ >> + fn from_iter>(it: I) -> Self { > > nit: maybe the name "iter" is better than "it"? Sure. >> + match qnum__.kind { >> + $($crate::bindings::QNUM_I64 => break { >> + let $i64var = unsafe { qnum__.u.i64_ }; >> + $i64 >> + },)? >> + $($crate::bindings::QNUM_U64 => break { >> + let $u64var = unsafe { qnum__.u.u64_ }; >> + $u64 >> + },)? >> + $($crate::bindings::QNUM_DOUBLE => break { >> + let $f64var = unsafe { qnum__.u.dbl }; >> + $f64 >> + },)? >> + _ => {} > > I think this doesn't handle a special case: qobj's QNUM type doesn't > macth the value type, for example, qobj is QNUM_U64 but value is i64. > > Though external code won't use this macro, I think panic may be better > than {}?> > Thurther, there're 2 match blocks. Could we merge them as one? Yes, that works because all callers specify all three of i64/u64/f64. Paolo