[PATCH 13/26] rust: qom: automatically use Drop trait to implement instance_finalize

[Paolo Bonzini]

Replace the customizable INSTANCE_FINALIZE with a generic function
that drops the Rust object.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/qemu-api/src/definitions.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
index 0467e6290e0..d64a581a5cc 100644
--- a/rust/qemu-api/src/definitions.rs
+++ b/rust/qemu-api/src/definitions.rs
@@ -8,6 +8,13 @@
 
 use crate::bindings::{Object, ObjectClass, TypeInfo};
 
+unsafe extern "C" fn drop_object<T: ObjectImpl>(obj: *mut Object) {
+    // SAFETY: obj is an instance of T, since drop_object<T>
+    // is called from QOM core as the instance_finalize function
+    // for class T
+    unsafe { std::ptr::drop_in_place(obj.cast::<T>()) }
+}
+
 /// Trait a type must implement to be registered with QEMU.
 pub trait ObjectImpl: ClassInitImpl + Sized {
     type Class;
@@ -16,7 +23,6 @@ pub trait ObjectImpl: ClassInitImpl + Sized {
     const ABSTRACT: bool = false;
     const INSTANCE_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
     const INSTANCE_POST_INIT: Option<unsafe extern "C" fn(obj: *mut Object)> = 
None;
-    const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = 
None;
 
     const TYPE_INFO: TypeInfo = TypeInfo {
         name: Self::TYPE_NAME.as_ptr(),
@@ -29,7 +35,7 @@ pub trait ObjectImpl: ClassInitImpl + Sized {
         instance_align: core::mem::align_of::<Self>(),
         instance_init: Self::INSTANCE_INIT,
         instance_post_init: Self::INSTANCE_POST_INIT,
-        instance_finalize: Self::INSTANCE_FINALIZE,
+        instance_finalize: Some(drop_object::<Self>),
         abstract_: Self::ABSTRACT,
         class_size: core::mem::size_of::<Self::Class>(),
         class_init: <Self as ClassInitImpl>::CLASS_INIT,
-- 
2.47.1