Try fix FSEventStreamCreate issue

Author: sungshik

src/main/rust/src/fs_monitor.rs

@@ -67,23 +67,24 @@ impl NativeEventStream {
     }
 
     fn build_context(&mut self) -> *const fsevent_sys::FSEventStreamContext {
-        eprintln!("ctx sending: {?}", self.sender_heap);
+        eprintln!("ctx sending: {:?}", self.sender_heap);
         &fs::FSEventStreamContext {
             version: 0,
             info: self.sender_heap as *mut _,
             retain: None,
-            release: None,
+            release: Some(release_context),
             copy_description: None
         }
     }
 
     pub fn start(&mut self) {
         unsafe {
+            let x = self.build_context();
             eprintln!("Creating stream: {}", self.since_when);
             let stream = fs::FSEventStreamCreate(
                 kCFAllocatorDefault,
                 callback,
-                self.build_context(),
+                x,
                 self.path.as_concrete_TypeRef(),
                 self.since_when,
                 0.15,
@@ -109,7 +110,6 @@ impl NativeEventStream {
                 fs::FSEventStreamInvalidate(stream);
                 dispatch2::ffi::dispatch_release(self.queue as dispatch_object_t);
                 fs::FSEventStreamRelease(stream);
-                drop(Box::from(self.sender_heap));
             }
             None => unsafe {
                 dispatch2::ffi::dispatch_release(self.queue as dispatch_object_t);
@@ -127,6 +127,20 @@ impl NativeEventStream {
 
 }
 
+extern "C" fn release_context(info: *mut c_void) {
+  // Safety:
+  // - The [documentation] for `FSEventStreamContext` states that `release` is only
+  //   called when the stream is deallocated, so it is safe to convert `info` back into a
+  //   box and drop it.
+  //
+  // [docs]: https://developer.apple.com/documentation/coreservices/fseventstreamcontext?language=objc
+  unsafe {
+      drop(Box::from_raw(
+          info as *mut CallbackContext,
+      ));
+  }
+}
+
 extern "C" fn callback(
     _stream_ref: fs::FSEventStreamRef,
     info: *mut c_void,
@@ -136,7 +150,7 @@ extern "C" fn callback(
     event_ids: *const fs::FSEventStreamEventId,
 ) {
     let ctx = unsafe{ &mut *(info as *mut CallbackContext) };
-    eprintln!("ctx restored: {?}", ctx);
+    eprintln!("ctx restored: {:?}", "foo");
 
     let event_paths = event_paths as *const *const c_char;