Re: [PATCH v7 6/7] rust: add crate to expose bindings and interfaces

[Junjie Mao]

On 8/15/2024 7:42 PM, Manos Pitsidianakis wrote:
> Add rust/qemu-api, which exposes rust-bindgen generated FFI bindings and
> provides some declaration macros for symbols visible to the rest of
> QEMU.
>
> Co-authored-by: Junjie Mao <junjie.mao@intel.com>
> Co-authored-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Junjie Mao <junjie.mao@intel.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
> ---
[snip]
> +
> +#[macro_export]
> +macro_rules! declare_properties {
> +    ($ident:ident, $($prop:expr),*$(,)*) => {
> +
> +        const fn _calc_prop_len() -> usize {
> +            let mut len = 1;
> +            $({
> +                _ = stringify!($prop);
> +                len += 1;
> +            })*
> +            len
> +        }
> +        const PROP_LEN: usize = _calc_prop_len();
> +
> +        #[no_mangle]
> +        fn _make_properties() -> [$crate::bindings::Property; PROP_LEN] {

#[no_mangle] also makes _make_properties externally visible and thus will cause 
duplicate-symbol-definition errors at link time when multiple devices are enabled.

Since it is only used in the definition of $ident below, shall we just remove 
#[no_mangle] for _make_properties?

---
Best Regards
Junjie Mao

> +            [
> +                $($prop),*,
> +                    unsafe { 
> ::core::mem::MaybeUninit::<$crate::bindings::Property>::zeroed().assume_init() 
> },
> +            ]
> +        }
> +
> +        #[no_mangle]
> +        pub static mut $ident: $crate::device_class::Properties<PROP_LEN> = 
> $crate::device_class::Properties(::std::sync::OnceLock::new(), _make_properties);
> +    };
> +}
> +
> +#[macro_export]
> +macro_rules! vm_state_description {
> +    ($(#[$outer:meta])*
> +     $name:ident,
> +     $(name: $vname:expr,)*
> +     $(unmigratable: $um_val:expr,)*
> +    ) => {
> +        #[used]
> +        $(#[$outer])*
> +        pub static $name: $crate::bindings::VMStateDescription = 
> $crate::bindings::VMStateDescription {
> +            $(name: {
> +                #[used]
> +                static VMSTATE_NAME: &::core::ffi::CStr = $vname;
> +                $vname.as_ptr()
> +            },)*
> +            unmigratable: true,
> +            ..unsafe { 
> ::core::mem::MaybeUninit::<$crate::bindings::VMStateDescription>::zeroed().assume_init()
>  }
> +        };
> +    }
> +}