MPSC channel assertion error

[TomPridham]

i am interfacing with the Windows Events api via the windows-rs crate. it requires that i pass a callback that will get called anytime a new event is posted. i am running into an odd intermittent error on the following line: https://docs.rs/tokio/1.14.0/src/tokio/sync/mpsc/chan.rs.html#243. in our real app it doesn't crash the entire process, but in the minimal repro it does. not sure what the difference there is. but the error we get is thread 'main' panicked at 'assertion failed: self.inner.semaphore.is_idle()', C:\Users\_\.cargo\registry\src\github.com-1ecc6299db9ec823\tokio-1.14.0\src\sync\mpsc\chan.rs:252:13
the repro is here: https://github.com/TomPridham/windows-events-rust
if anyone has some insight into what i am doing wrong here, it would be much appreciated

[Darksonn]

Does that callback get called more than once? Because your use of Box::from_raw is deallocating the Box after the first time its called.

[TomPridham]

oh, duh. somehow i missed that it took ownership and deallocated it. changing that line to this gets things working correctly. thanks so much!

-    let sender = unsafe { Box::from_raw(p_context as *mut UnboundedSender<String>) };
+    let sender = unsafe {
+        (p_context as *mut UnboundedSender<String>)
+            .as_ref()
+            .unwrap()
+    };