From 7acab7ac040622b1733ebda4c2faae75166fb36f Mon Sep 17 00:00:00 2001
From: Manodasan Wignarajah <mawign@microsoft.com>
Date: Thu, 9 Sep 2021 11:35:15 -0700
Subject: [PATCH] Fix array marshalers to handle null (#983)

---
 .../UnitTest/TestComponentCSharp_Tests.cs     | 21 ++++++++++++++++--
 src/Tests/UnitTest/TestComponent_Tests.cs     | 22 +++++++++++++++++++
 src/WinRT.Runtime/Marshalers.cs               | 20 +++++++++++++++--
 3 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/src/Tests/UnitTest/TestComponentCSharp_Tests.cs b/src/Tests/UnitTest/TestComponentCSharp_Tests.cs
index 65dd6010b..3319b3a9f 100644
--- a/src/Tests/UnitTest/TestComponentCSharp_Tests.cs
+++ b/src/Tests/UnitTest/TestComponentCSharp_Tests.cs
@@ -118,13 +118,19 @@ public void TestEnums()
             TestObject.EnumsProperty = expectedEnums;
             Assert.Equal(expectedEnums, TestObject.EnumsProperty);
             TestObject.CallForEnums(() => expectedEnums);
-            Assert.Equal(expectedEnums, TestObject.EnumsProperty);
+            Assert.Equal(expectedEnums, TestObject.EnumsProperty);
+
+            TestObject.EnumsProperty = null;
+            Assert.Equal(null, TestObject.EnumsProperty);
 
             var expectedEnumStructs = new EnumStruct[] { new EnumStruct(EnumValue.One), new EnumStruct(EnumValue.Two) };
             TestObject.EnumStructsProperty = expectedEnumStructs;
             Assert.Equal(expectedEnumStructs, TestObject.EnumStructsProperty);
             TestObject.CallForEnumStructs(() => expectedEnumStructs);
-            Assert.Equal(expectedEnumStructs, TestObject.EnumStructsProperty);
+            Assert.Equal(expectedEnumStructs, TestObject.EnumStructsProperty);
+
+            TestObject.EnumStructsProperty = null;
+            Assert.Equal(null, TestObject.EnumStructsProperty);
 
             // Flags
             var expectedFlag = FlagValue.All;
@@ -1167,6 +1173,17 @@ public void TestComposedNonBlittableStruct()
             Assert.True(val.bools.x);
             Assert.False(val.bools.y);
             Assert.True(val.bools.z);
+        }
+
+        [Fact]
+        public void TestBlittableArrays()
+        {
+            int[] arr = new[] { 2, 4, 6, 8 };
+            TestObject.SetInts(arr);
+            Assert.True(TestObject.GetInts().SequenceEqual(arr));
+
+            TestObject.SetInts(null);
+            Assert.Null(TestObject.GetInts());
         }
 
 #if NETCOREAPP2_0
diff --git a/src/Tests/UnitTest/TestComponent_Tests.cs b/src/Tests/UnitTest/TestComponent_Tests.cs
index fc29de985..aec109c45 100644
--- a/src/Tests/UnitTest/TestComponent_Tests.cs
+++ b/src/Tests/UnitTest/TestComponent_Tests.cs
@@ -376,6 +376,17 @@ public void Array_String()
             Assert.True(AllEqual(a, b, c, d));
         }
 
+        [Fact]
+        public void Array_NullStringArray()
+        {
+            string[] a = null;
+            string[] b = null;
+            string[] c;
+            string[] d = Tests.Array12(a, b, out c);
+            Assert.Null(c);
+            Assert.Null(d);
+        }
+
         [Fact]
         public void Array_Blittable()
         {
@@ -437,6 +448,17 @@ public void Array_Stringable()
             Assert.True(AllEqual(a, b, c, d));
         }
 
+        [Fact]
+        public void Array_NullInterfaces()
+        {
+            IStringable[] a = null;
+            IStringable[] b = null;
+            IStringable[] c;
+            IStringable[] d = Tests.Array16(a, b, out c);
+            Assert.Null(c);
+            Assert.Null(d);
+        }
+
         private T[] Array_Call<T>(T[] a, T[] b, out T[] c)
         {
             Assert.True(a.Length == b.Length);
diff --git a/src/WinRT.Runtime/Marshalers.cs b/src/WinRT.Runtime/Marshalers.cs
index 09f292393..7278ea81d 100644
--- a/src/WinRT.Runtime/Marshalers.cs
+++ b/src/WinRT.Runtime/Marshalers.cs
@@ -174,6 +174,10 @@ public static unsafe string[] FromAbiArray(object box)
                 return null;
             }
             var abi = ((int length, IntPtr data))box;
+            if (abi.data == IntPtr.Zero)
+            {
+                return null;
+            }
             string[] array = new string[abi.length];
             var data = (IntPtr*)abi.data.ToPointer();
             for (int i = 0; i < abi.length; i++)
@@ -277,7 +281,7 @@ public struct MarshalBlittable<T>
     {
         public struct MarshalerArray
         {
-            public MarshalerArray(Array array) => _gchandle = GCHandle.Alloc(array, GCHandleType.Pinned);
+            public MarshalerArray(Array array) => _gchandle = array is null ? default : GCHandle.Alloc(array, GCHandleType.Pinned);
             public void Dispose() => _gchandle.Dispose();
 
             public GCHandle _gchandle;
@@ -288,7 +292,7 @@ public struct MarshalerArray
         public static (int length, IntPtr data) GetAbiArray(object box)
         {
             var m = (MarshalerArray)box;
-            return (((Array)m._gchandle.Target).Length, m._gchandle.AddrOfPinnedObject());
+            return m._gchandle.IsAllocated ? (((Array)m._gchandle.Target).Length, m._gchandle.AddrOfPinnedObject()) : (0, IntPtr.Zero);
         }
 
         public static unsafe T[] FromAbiArray(object box)
@@ -298,6 +302,10 @@ public static unsafe T[] FromAbiArray(object box)
                 return null;
             }
             var abi = ((int length, IntPtr data))box;
+            if (abi.data == IntPtr.Zero)
+            {
+                return null;
+            }
             var abiSpan = new ReadOnlySpan<T>(abi.data.ToPointer(), abi.length);
             return abiSpan.ToArray();
         }
@@ -583,6 +591,10 @@ public void Dispose()
                 return null;
             }
             var abi = ((int length, IntPtr data))box;
+            if (abi.data == IntPtr.Zero)
+            {
+                return null;
+            }
             var array = new T[abi.length];
             var data = (byte*)abi.data.ToPointer();
             var abi_element_size = Marshal.SizeOf(AbiType);
@@ -763,6 +775,10 @@ public static unsafe T[] FromAbiArray(object box, Func<IntPtr, T> fromAbi)
                 return null;
             }
             var abi = ((int length, IntPtr data))box;
+            if (abi.data == IntPtr.Zero)
+            {
+                return null;
+            }
             var array = new T[abi.length];
             var data = (IntPtr*)abi.data.ToPointer();
             for (int i = 0; i < abi.length; i++)