Re: [PATCH v2 00/16] rust: QObject and QAPI bindings

Paolo Bonzini
2026-02-19T16:29:50Z

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Il gio 19 feb 2026, 14:39 Markus Armbruster <armbru@redhat.com> ha scritto:

> Paolo Bonzini <pbonzini@redhat.com> writes:
>
> > This adds two related parts of the Rust bindings:
> >
> > - QAPI code generator that creates Rust structs from the JSON
> > description. The structs are *not* ABI compatible with the
> > C ones, instead they use native Rust data types.
> >
> > - QObject bindings and (de)serialization support, which can be used to
> > convert QObjects to and from QAPI structs.
>
> To and from generated Rust structs, I presume.
>

Yes, or enums—and actually any (de)serializable Rust type, of which QAPI
structs should be the most common case.

> As an example of how this would be used, the marshaling functions for
> > QMP commands would look like this:
> >
> > fn qmp_marshal_query_stats(args: *mut QDict,
> > retp: *mut *mut QObject, errp: *mut *mut Error)
> > {
> > let qobj = unsafe { QObject::cloned_from_raw(args.cast()) };
> >
> > let result = from_qobject::<StatsFilter>(qobj)
> > .map_err(anyhow::Error::from)
> > .and_then(qmp_query_stats)
> > .and_then(|ret|
> to_qobject::<Vec<StatsResult>>(ret).map_err(anyhow::Error::from));
> >
> > match qmp_marshal_query_stats_rs(qobj) {
> > Ok(ret) => unsafe { *retp = ret.into_raw(); },
> > Err(e) => unsafe { crate::Error::from(e).propagate(errp) },
> > }
> > }
>
> Scoring 0.23 UOUPNBL (uses of unsafe per non-blank line). SCNR!
>

Well, that's why you automatically generate this! You could also use only
one or two unsafe blocks but I preferred to mark explicitly the code that
requires it.

Paolo

> > Despite the long v1->v2, the changes are mostly cosmetic; there are a few
> > small differences in the detection of types to be wrapped with Box<>,
> > because Vec<> is now considered to break cycles.
> >
> > Available at branch rust-next of https://gitlab.com/bonzini/qemu (which
> > is now almost empty other than this series, yay).
> >
> > Paolo
>
>

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