2 files changed, 85 insertions, 20 deletions

diff --git a/mono/metadata/cominterop.c b/mono/metadata/cominterop.c
index 9ec1d0f10c3..d0e2241063c 100644
--- a/mono/metadata/cominterop.c
+++ b/mono/metadata/cominterop.c
@@ -173,6 +173,31 @@ typedef struct {
 	MonoCCW* ccw;
 } MonoCCWInterface;
 
+/*
+ * COM Callable Wrappers
+ *
+ * CCWs may be called on threads that aren't attached to the runtime, they can
+ * then run managed code or the method implementations may use coop handles.
+ * Use the macros below to setup the thread state.
+ *
+ * For managed methods, the runtime marshaling wrappers handle attaching and
+ * coop state switching.
+ */
+
+#define MONO_CCW_CALL_ENTER do {					\
+	gpointer dummy;							\
+	gpointer orig_domain = mono_threads_attach_coop (mono_domain_get (), &dummy); \
+	MONO_ENTER_GC_UNSAFE;						\
+	HANDLE_FUNCTION_ENTER ();					\
+	do {} while (0)
+
+#define MONO_CCW_CALL_EXIT				\
+	HANDLE_FUNCTION_RETURN ();			\
+	MONO_EXIT_GC_UNSAFE;				\
+	mono_threads_detach_coop (orig_domain, &dummy); \
+	} while (0)
+
+
 /* IUnknown */
 static int STDCALL cominterop_ccw_addref (MonoCCWInterface* ccwe);
 
@@ -2568,12 +2593,9 @@ static int STDCALL
 cominterop_ccw_addref (MonoCCWInterface* ccwe)
 {
 	int result;
-	gpointer dummy;
-	gpointer orig_domain = mono_threads_attach_coop (mono_domain_get (), &dummy);
-	MONO_ENTER_GC_UNSAFE;
+	MONO_CCW_CALL_ENTER;
 	result = cominterop_ccw_addref_impl (ccwe);
-	MONO_EXIT_GC_UNSAFE;
-	mono_threads_detach_coop (orig_domain, &dummy);
+	MONO_CCW_CALL_EXIT;
 	return result;
 }
 
@@ -2602,12 +2624,9 @@ static int STDCALL
 cominterop_ccw_release (MonoCCWInterface* ccwe)
 {
 	int result;
-	gpointer dummy;
-	gpointer orig_domain = mono_threads_attach_coop (mono_domain_get (), &dummy);
-	MONO_ENTER_GC_UNSAFE;
+	MONO_CCW_CALL_ENTER;
 	result = cominterop_ccw_release_impl (ccwe);
-	MONO_EXIT_GC_UNSAFE;
-	mono_threads_detach_coop (orig_domain, &dummy);
+	MONO_CCW_CALL_EXIT;
 	return result;
 }
 
@@ -2654,12 +2673,9 @@ static int STDCALL
 cominterop_ccw_queryinterface (MonoCCWInterface* ccwe, const guint8* riid, gpointer* ppv)
 {
 	int result;
-	gpointer dummy;
-	gpointer orig_domain = mono_threads_attach_coop (mono_domain_get (), &dummy);
-	MONO_ENTER_GC_UNSAFE;
+	MONO_CCW_CALL_ENTER;
 	result = cominterop_ccw_queryinterface_impl (ccwe, riid, ppv);
-	MONO_EXIT_GC_UNSAFE;
-	mono_threads_detach_coop (orig_domain, &dummy);
+	MONO_CCW_CALL_EXIT;
 	return result;
 }
 
@@ -2777,12 +2793,9 @@ cominterop_ccw_get_ids_of_names (MonoCCWInterface* ccwe, gpointer riid,
 											 guint32 lcid, gint32 *rgDispId)
 {
 	int result;
-	gpointer dummy;
-	gpointer orig_domain = mono_threads_attach_coop (mono_domain_get(), &dummy);
-	MONO_ENTER_GC_UNSAFE;
+	MONO_CCW_CALL_ENTER;
 	result = cominterop_ccw_get_ids_of_names_impl (ccwe, riid, rgszNames, cNames, lcid, rgDispId);
-	MONO_EXIT_GC_UNSAFE;
-	mono_threads_detach_coop (orig_domain, &dummy);
+	MONO_CCW_CALL_EXIT;
 	return result;
 }
 
diff --git a/mono/tests/cominterop.cs b/mono/tests/cominterop.cs
index 11cb68bcdbc..3ff018efa71 100644
--- a/mono/tests/cominterop.cs
+++ b/mono/tests/cominterop.cs
@@ -659,6 +659,9 @@ public class Tests
 				}
 			}
 
+			if (CallableWrapperLeakTest () != 0)
+			    return 209;
+
 			#endregion // COM Callable Wrapper Tests
 
 			#region SAFEARRAY tests
@@ -1630,6 +1633,55 @@ public class Tests
                 return 2;
             return 0;
         }
+
+	// Doesn't matter what this is
+	internal class CallableWrapperLeakTestClass {
+	}
+
+	public static int CallableWrapperLeakTest () {
+		bool ok = true;
+		GCHandle h = HideFromGC (() => {
+			var o = new CallableWrapperLeakTestClass();
+			var weakHandle = GCHandle.Alloc (o, GCHandleType.Weak);
+			var pUnk = Marshal.GetIUnknownForObject (o);
+			int c = Marshal.Release(pUnk);
+			o = null;
+			if (c != 0) {
+				Console.Error.WriteLine ("Expected IUnknown refcount on a CCW to be 0 after Release, was {0}", c);
+				ok = false;
+			}
+			return weakHandle;
+		});
+		if (!ok)
+			return 1;
+		GC.Collect();
+		GC.WaitForPendingFinalizers();
+		GC.Collect();
+		GC.WaitForPendingFinalizers();
+		HideFromGC(() => {
+			var o = h.Target;
+			if (o != null) {
+				Console.Error.WriteLine ("Expected weak handle to be null after GC, but the object (of type {0}) was retained", o.GetType());
+				ok = false;
+			}
+			return "done"; // doesn't matter
+		});
+		if (!ok)
+			return 2;
+		return 0;
+	}
+
+	[MethodImpl (MethodImplOptions.NoInlining)]
+	private static T HideFromGC<T> (Func<T> f) => HideFromGC (20, f);
+
+	[MethodImpl (MethodImplOptions.NoInlining)]
+	private static T HideFromGC<T> (int rec, Func<T> f) {
+		if (rec <= 0)
+			return f ();
+		else
+			return HideFromGC (rec - 1, f);
+	}
+
 }
 
 public class TestVisible