Re: [PATCH 13/15] rust: memory: wrap MemoryRegion with Opaque<>

[Zhao Liu <zhao1.liu@intel.com>]

>  impl MemoryRegion {
>      // inline to ensure that it is not included in tests, which only
> @@ -174,13 +174,15 @@ pub fn init_io<T: IsA<Object>>(
>          size: u64,
>      ) {
>          unsafe {
> -            Self::do_init_io(&mut self.inner, owner.cast::<Object>(), &ops.0, name, size);
> +            Self::do_init_io(
> +                self.0.as_mut_ptr(),

I'm not sure why the wrapper doesn't work here.

If I change this to `self.as_mut_ptr()`, then compiler tries to apply
`ObjectDeref::as_mut_ptr` and complains:

the trait `qom::ObjectType` is not implemented for `bindings::MemoryRegion`


But when I modify the function signature to &self like:

diff --git a/rust/qemu-api/src/memory.rs b/rust/qemu-api/src/memory.rs
index fdb1ea11fcf9..a82348c4a564 100644
--- a/rust/qemu-api/src/memory.rs
+++ b/rust/qemu-api/src/memory.rs
@@ -167,7 +167,7 @@ unsafe fn do_init_io(
     }

     pub fn init_io<T: IsA<Object>>(
-        &mut self,
+        &self,
         owner: *mut T,
         ops: &'static MemoryRegionOps<T>,
         name: &'static str,

Then the Wrapper's as_mut_ptr() can work.

> +                owner.cast::<Object>(),
> +                &ops.0,
> +                name,
> +                size,
> +            );
>          }
>      }
> -
> -    pub(crate) const fn as_mut_ptr(&self) -> *mut bindings::MemoryRegion {
> -        addr_of!(self.inner) as *mut _
> -    }
>  }
>  
>  unsafe impl ObjectType for MemoryRegion {
> -- 
> 2.48.1
> 
>