zomg pointers

crates/libs/core/src/dynamic_cast.rs

@@ -51,8 +51,7 @@ pub struct IDynamicCast_Vtbl {
 impl IDynamicCast_Vtbl {
     pub const fn new<Identity: IUnknownImpl<Impl = Impl> + Any + 'static, Impl: IDynamicCast_Impl, const OFFSET: isize>() -> Self {
         unsafe extern "Rust" fn as_any<Identity: IUnknownImpl<Impl = Impl> + Any + 'static, Impl: IDynamicCast_Impl, const OFFSET: isize>(this: *mut c_void) -> *const dyn Any {
-            let this_inner = (this as *mut *mut c_void).offset(OFFSET) as *mut Impl; // <-- this is the "inner" object pointer, e.g. MyApp
-            let this_outer = this_inner.sub(Identity::INNER_OFFSET_IN_POINTERS) as *const Identity; // <-- this is the "outer" object pointer, e.g. MyApp_Impl
+            let this_outer = (this as *mut *mut c_void).offset(OFFSET) as *mut Identity; // <-- this is the "outer" object pointer, e.g. MyApp_Impl
             let outer_any: &dyn Any = &(*this_outer); // <-- this cast works because of the + Any + 'static constraints
             outer_any as *const dyn Any
         }

crates/tests/implement_core/src/com_object.rs

@@ -20,8 +20,11 @@ unsafe trait IBar: IUnknown {
     fn say_hello(&self);
 }
 
+const APP_SIGNATURE: [u8; 8] = *b"cafef00d";
+
 #[implement(IFoo, IBar, IDynamicCast)]
 struct MyApp {
+    signature: [u8; 8],
     x: u32,
     tombstone: Arc<Tombstone>,
 }
@@ -64,6 +67,7 @@ impl core::fmt::Display for MyApp {
 impl Default for MyApp {
     fn default() -> Self {
         Self {
+            signature: APP_SIGNATURE,
             x: 0,
             tombstone: Arc::new(Tombstone::default()),
         }
@@ -110,6 +114,7 @@ impl MyApp {
     fn new(x: u32) -> ComObject<Self> {
         ComObject::new(Self {
             x,
+            signature: APP_SIGNATURE,
             tombstone: Arc::new(Tombstone::default()),
         })
     }
@@ -342,14 +347,14 @@ fn to_object() {
 
     let second_app = app_outer.to_object();
     assert!(!tombstone.is_dead());
+    assert_eq!(second_app.signature, APP_SIGNATURE);
 
     println!("x = {}", unsafe { second_app.get_x() });
 
     drop(second_app);
     assert!(!tombstone.is_dead());
 
     drop(app);
-
     assert!(tombstone.is_dead());
 }
 
@@ -362,9 +367,11 @@ fn dynamic_cast() {
     assert!(!idyn.is::<SendableThing>());
     assert!(idyn.is::<MyApp>());
 
-    let _dyn_app: &MyApp_Impl = idyn.downcast_ref::<MyApp>().unwrap();
+    let dyn_app_ref: &MyApp_Impl = idyn.downcast_ref::<MyApp>().unwrap();
+    assert_eq!(dyn_app_ref.signature, APP_SIGNATURE);
 
-    let _dyn_owned: ComObject<MyApp> = unknown.cast_impl().unwrap();
+    let dyn_app_owned: ComObject<MyApp> = unknown.cast_impl().unwrap();
+    assert_eq!(dyn_app_owned.signature, APP_SIGNATURE);
 }
 
 // This tests that we can place a type that is not Send in a ComObject.