From 9cc2988ec7e935b39853e1cc33b4977da4a69825 Mon Sep 17 00:00:00 2001
From: Raph Levien <raph.levien@gmail.com>
Date: Fri, 2 Aug 2019 19:08:53 -0700
Subject: [PATCH] Fix technical undefined behavior

I believe that the current drop implementation has technical undefined
behavior, because holds a reference to the `IUnknown` object while that
object is in the process of being deallocated. This patch retrieves the
function pointer, drops the reference, then does the release.
---
 src/com.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/com.rs b/src/com.rs
index d94d3d3..15aa814 100644
--- a/src/com.rs
+++ b/src/com.rs
@@ -69,7 +69,11 @@ impl<T> Debug for ComPtr<T> {
 }
 impl<T> Drop for ComPtr<T> {
     fn drop(&mut self) {
-        unsafe { self.as_unknown().Release(); }
+        unsafe {
+            let ptr = self.as_raw() as *mut IUnknown;
+            let release_fn = (*(*ptr).lpVtbl).Release;
+            release_fn(ptr);
+        }
     }
 }
 impl<T> PartialEq<ComPtr<T>> for ComPtr<T> where T: Interface {