Re: [PATCH 04/14] rust: add Serialize implementation for QObject

On Wed, Oct 01, 2025 at 10:00:41AM +0200, Paolo Bonzini wrote:
> Date: Wed,  1 Oct 2025 10:00:41 +0200
> From: Paolo Bonzini <[email protected]>
> Subject: [PATCH 04/14] rust: add Serialize implementation for QObject
> X-Mailer: git-send-email 2.51.0
> 
> This allows QObject to be converted to other formats, for example
> JSON via serde_json.
> 
> This is not too useful, since QObjects are consumed by
> C code or deserialized into structs, but it can be used for testing
> and it is part of the full implementation of a serde format.
> 
> Co-authored-by: Marc-André Lureau <[email protected]>
> Signed-off-by: Marc-André Lureau <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>
> ---
>  rust/Cargo.lock                    |  1 +
>  rust/util/Cargo.toml               |  1 +
>  rust/util/meson.build              |  3 +-
>  rust/util/src/qobject/mod.rs       |  4 +-
>  rust/util/src/qobject/serialize.rs | 59 ++++++++++++++++++++++++++++++
>  5 files changed, 65 insertions(+), 3 deletions(-)
>  create mode 100644 rust/util/src/qobject/serialize.rs

...

> +impl Serialize for QObject {
> +    #[inline]
> +    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
> +    where
> +        S: ::serde::Serializer,
> +    {
> +        match_qobject! { (self) =>
> +            () => serializer.serialize_unit(),
> +            bool(b) => serializer.serialize_bool(b),
> +            i64(i) => serializer.serialize_i64(i),
> +            u64(u) => serializer.serialize_u64(u),
> +            f64(f) => serializer.serialize_f64(f),
> +            CStr(cstr) => cstr.to_str().map_or_else(
> +                |_| Err(ser::Error::custom("invalid UTF-8 in QString")),
> +                |s| serializer.serialize_str(s),
> +            ),
> +            QList(l) => {
> +                let mut node_ptr = unsafe { l.head.tqh_first };
> +                let mut state = serializer.serialize_seq(None)?;
> +                while !node_ptr.is_null() {
> +                    let node = unsafe { &*node_ptr };
> +                    let elem = unsafe { ManuallyDrop::new(QObject::from_raw(addr_of!(*node.value))) };
> +                    state.serialize_element(&*elem)?;

QObject here is always valid so it's not necessary to concern about it
is destroied by C side, and so that it's not necessary to use
cloned_from_raw here.

Reviewed-by: Zhao Liu <[email protected]>