dotnet · LakshanF · May 7, 2021 · May 2, 2021 · May 3, 2021 · May 4, 2021
diff --git a/docs/workflow/trimming/feature-switches.md b/docs/workflow/trimming/feature-switches.md
@@ -20,6 +20,7 @@ configurations but their defaults might vary as any SDK can set the defaults dif
 | TBD | System.Threading.ThreadPool.EnableDispatchAutoreleasePool | When set to true, creates an NSAutoreleasePool around each thread pool work item on applicable platforms. |
 | CustomResourceTypesSupport | System.Resources.ResourceManager.AllowCustomResourceTypes | Use of custom resource types is disabled when set to false. ResourceManager code paths that use reflection for custom types can be trimmed. |
 | EnableUnsafeBinaryFormatterInDesigntimeLicenseContextSerialization | System.ComponentModel.TypeConverter.EnableUnsafeBinaryFormatterInDesigntimeLicenseContextSerialization | BinaryFormatter serialization support is trimmed when set to false. |
+| BuiltInComInteropSupport | System.Runtime.InteropServices.BuiltInComInterop.IsSupported | Built-in COM support is trimmed when set to false. |
 
 Any feature-switch which defines property can be set in csproj file or
 on the command line as any other MSBuild property. Those without predefined property name

diff --git a/src/coreclr/System.Private.CoreLib/src/ILLink/ILLink.Substitutions.xml b/src/coreclr/System.Private.CoreLib/src/ILLink/ILLink.Substitutions.xml
@@ -3,5 +3,8 @@
     <type fullname="System.StartupHookProvider" feature="System.StartupHookProvider.IsSupported" featurevalue="false">
       <method signature="System.Boolean get_IsSupported()" body="stub" value="false" />
     </type>
+    <type fullname="System.Runtime.InteropServices.Marshal" feature="System.Runtime.InteropServices.BuiltInComInterop.IsSupported" featurevalue="false">
+      <method signature="System.Boolean get_IsBuiltInComSupported()" body="stub" value="false" />
+    </type>
   </assembly>
-</linker>
+</linker>
diff --git a/...stem.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivationContextInternal.cs b/...stem.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivationContextInternal.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.InteropServices;
 
 namespace Internal.Runtime.InteropServices
@@ -39,6 +40,7 @@ public partial struct ComActivationContext
     [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
     public interface IClassFactory
     {
+        [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
         void CreateInstance(
             [MarshalAs(UnmanagedType.Interface)] object? pUnkOuter,
             ref Guid riid,

diff --git a/src/coreclr/System.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivator.cs b/src/coreclr/System.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivator.cs
@@ -35,6 +35,7 @@ internal struct LICINFO
     [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
     internal interface IClassFactory2 : IClassFactory
     {
+        [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
         new void CreateInstance(
             [MarshalAs(UnmanagedType.Interface)] object? pUnkOuter,
             ref Guid riid,
@@ -62,7 +63,7 @@ public partial struct ComActivationContext
         [CLSCompliant(false)]
         public static unsafe ComActivationContext Create(ref ComActivationContextInternal cxtInt)
         {
-            if (!Marshal.IsComSupported)
+            if (!Marshal.IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -92,7 +93,7 @@ public static class ComActivator
         [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
         public static object GetClassFactoryForType(ComActivationContext cxt)
         {
-            if (!Marshal.IsComSupported)
+            if (!Marshal.IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -126,7 +127,7 @@ public static object GetClassFactoryForType(ComActivationContext cxt)
         [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
         public static void ClassRegistrationScenarioForType(ComActivationContext cxt, bool register)
         {
-            if (!Marshal.IsComSupported)
+            if (!Marshal.IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -222,7 +223,7 @@ public static void ClassRegistrationScenarioForType(ComActivationContext cxt, bo
         [UnmanagedCallersOnly]
         public static unsafe int GetClassFactoryForTypeInternal(ComActivationContextInternal* pCxtInt)
         {
-            if (!Marshal.IsComSupported)
+            if (!Marshal.IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -265,7 +266,7 @@ public static unsafe int GetClassFactoryForTypeInternal(ComActivationContextInte
         [UnmanagedCallersOnly]
         public static unsafe int RegisterClassForTypeInternal(ComActivationContextInternal* pCxtInt)
         {
-            if (!Marshal.IsComSupported)
+            if (!Marshal.IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -311,7 +312,7 @@ public static unsafe int RegisterClassForTypeInternal(ComActivationContextIntern
         [UnmanagedCallersOnly]
         public static unsafe int UnregisterClassForTypeInternal(ComActivationContextInternal* pCxtInt)
         {
-            if (!Marshal.IsComSupported)
+            if (!Marshal.IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -364,6 +365,7 @@ private static void Log(string fmt, params object[] args)
             Debug.WriteLine(fmt, args);
         }
 
+        [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
         private static Type FindClassType(Guid clsid, string assemblyPath, string assemblyName, string typeName)
         {
             try
@@ -489,6 +491,7 @@ public static object CreateAggregatedObject(object pUnkOuter, object comObject)
                 }
             }
 
+            [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
             public void CreateInstance(
                 [MarshalAs(UnmanagedType.Interface)] object? pUnkOuter,
                 ref Guid riid,
@@ -524,6 +527,7 @@ public LicenseClassFactory(Guid clsid, Type classType)
                 _classType = classType;
             }
 
+            [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
             public void CreateInstance(
                 [MarshalAs(UnmanagedType.Interface)] object? pUnkOuter,
                 ref Guid riid,

diff --git a/src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.CoreCLR.cs b/src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.CoreCLR.cs
@@ -196,7 +196,7 @@ private static void PrelinkCore(MethodInfo m)
         private static extern void InternalPrelink(RuntimeMethodHandleInternal m);
 
         [DllImport(RuntimeHelpers.QCall)]
-        private static extern bool IsComSupportedInternal();
+        private static extern bool IsBuiltInComSupportedInternal();
 
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern /* struct _EXCEPTION_POINTERS* */ IntPtr GetExceptionPointers();
@@ -236,9 +236,7 @@ private static object PtrToStructureHelper(IntPtr ptr, Type structureType)
         [MethodImpl(MethodImplOptions.InternalCall)]
         internal static extern bool IsPinnable(object? obj);
 
-        internal static bool IsComSupported { get; } = InitializeIsComSupported();
-
-        private static bool InitializeIsComSupported() => IsComSupportedInternal();
+        internal static bool IsBuiltInComSupported { get; } = IsBuiltInComSupportedInternal();
 
 #if TARGET_WINDOWS
         /// <summary>
@@ -296,7 +294,7 @@ public static string GetTypeInfoName(ITypeInfo typeInfo)
         // on Marshal for more consistent API surface.
         internal static Type? GetTypeFromCLSID(Guid clsid, string? server, bool throwOnError)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -443,7 +441,7 @@ public static object GetUniqueObjectForIUnknown(IntPtr unknown)
         [SupportedOSPlatform("windows")]
         public static IntPtr CreateAggregatedObject(IntPtr pOuter, object o)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -457,7 +455,7 @@ public static IntPtr CreateAggregatedObject(IntPtr pOuter, object o)
         [SupportedOSPlatform("windows")]
         public static IntPtr CreateAggregatedObject<T>(IntPtr pOuter, T o) where T : notnull
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -484,7 +482,7 @@ public static IntPtr CreateAggregatedObject<T>(IntPtr pOuter, T o) where T : not
         [SupportedOSPlatform("windows")]
         public static int ReleaseComObject(object o)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -512,7 +510,7 @@ public static int ReleaseComObject(object o)
         [SupportedOSPlatform("windows")]
         public static int FinalReleaseComObject(object o)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -536,7 +534,7 @@ public static int FinalReleaseComObject(object o)
         [SupportedOSPlatform("windows")]
         public static object? GetComObjectData(object obj, object key)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -567,7 +565,7 @@ public static int FinalReleaseComObject(object o)
         [SupportedOSPlatform("windows")]
         public static bool SetComObjectData(object obj, object key, object? data)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -597,7 +595,7 @@ public static bool SetComObjectData(object obj, object key, object? data)
         [return: NotNullIfNotNull("o")]
         public static object? CreateWrapperOfType(object? o, Type t)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -652,7 +650,7 @@ public static bool SetComObjectData(object obj, object key, object? data)
         [SupportedOSPlatform("windows")]
         public static TWrapper CreateWrapperOfType<T, TWrapper>(T? o)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -672,7 +670,7 @@ public static TWrapper CreateWrapperOfType<T, TWrapper>(T? o)
         [SupportedOSPlatform("windows")]
         public static void GetNativeVariantForObject(object? obj, /* VARIANT * */ IntPtr pDstNativeVariant)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -686,7 +684,7 @@ public static void GetNativeVariantForObject(object? obj, /* VARIANT * */ IntPtr
         [SupportedOSPlatform("windows")]
         public static void GetNativeVariantForObject<T>(T? obj, IntPtr pDstNativeVariant)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -697,7 +695,7 @@ public static void GetNativeVariantForObject<T>(T? obj, IntPtr pDstNativeVariant
         [SupportedOSPlatform("windows")]
         public static object? GetObjectForNativeVariant(/* VARIANT * */ IntPtr pSrcNativeVariant)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -711,7 +709,7 @@ public static void GetNativeVariantForObject<T>(T? obj, IntPtr pDstNativeVariant
         [SupportedOSPlatform("windows")]
         public static T? GetObjectForNativeVariant<T>(IntPtr pSrcNativeVariant)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -722,7 +720,7 @@ public static void GetNativeVariantForObject<T>(T? obj, IntPtr pDstNativeVariant
         [SupportedOSPlatform("windows")]
         public static object?[] GetObjectsForNativeVariants(/* VARIANT * */ IntPtr aSrcNativeVariant, int cVars)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -736,7 +734,7 @@ public static void GetNativeVariantForObject<T>(T? obj, IntPtr pDstNativeVariant
         [SupportedOSPlatform("windows")]
         public static T[] GetObjectsForNativeVariants<T>(IntPtr aSrcNativeVariant, int cVars)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -764,10 +762,11 @@ public static T[] GetObjectsForNativeVariants<T>(IntPtr aSrcNativeVariant, int c
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern int GetEndComSlot(Type t);
 
+        [RequiresUnreferencedCode("Built-in COM support is not trim compatible", Url = "https://aka.ms/dotnet-illink/com")]
         [SupportedOSPlatform("windows")]
         public static object BindToMoniker(string monikerName)
         {
-            if (!IsComSupported)
+            if (!IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }
@@ -780,12 +779,19 @@ public static object BindToMoniker(string monikerName)
             return obj;
         }
 
+        // Revist after https://github.com/mono/linker/issues/1989 is fixed
+        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2050:UnrecognizedReflectionPattern",
+            Justification = "The calling method is annotated with RequiresUnreferencedCode")]
         [DllImport(Interop.Libraries.Ole32, PreserveSig = false)]
         private static extern void CreateBindCtx(uint reserved, out IBindCtx ppbc);
 
+        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2050:UnrecognizedReflectionPattern",
+            Justification = "The calling method is annotated with RequiresUnreferencedCode")]
         [DllImport(Interop.Libraries.Ole32, PreserveSig = false)]
         private static extern void MkParseDisplayName(IBindCtx pbc, [MarshalAs(UnmanagedType.LPWStr)] string szUserName, out uint pchEaten, out IMoniker ppmk);
 
+        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2050:UnrecognizedReflectionPattern",
+            Justification = "The calling method is annotated with RequiresUnreferencedCode")]
         [DllImport(Interop.Libraries.Ole32, PreserveSig = false)]
         private static extern void BindMoniker(IMoniker pmk, uint grfOpt, ref Guid iidResult, [MarshalAs(UnmanagedType.Interface)] out object ppvResult);
 

diff --git a/src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs b/src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs
@@ -3680,7 +3680,7 @@ private extern object InvokeDispMethod(
             Type[] aArgsTypes,
             Type retType)
         {
-            if (!Marshal.IsComSupported)
+            if (!Marshal.IsBuiltInComSupported)
             {
                 throw new NotSupportedException(SR.NotSupported_COM);
             }

diff --git a/src/coreclr/vm/ecalllist.h b/src/coreclr/vm/ecalllist.h
@@ -758,7 +758,7 @@ FCFuncStart(gInteropMarshalFuncs)
     FCFuncElement("OffsetOfHelper", MarshalNative::OffsetOfHelper)
 
     QCFuncElement("InternalPrelink", MarshalNative::Prelink)
-    QCFuncElement("IsComSupportedInternal", MarshalNative::IsComSupported)
+    QCFuncElement("IsBuiltInComSupportedInternal", MarshalNative::IsBuiltInComSupported)
     FCFuncElement("GetExceptionForHRInternal", MarshalNative::GetExceptionForHR)
     FCFuncElement("GetDelegateForFunctionPointerInternal", MarshalNative::GetDelegateForFunctionPointerInternal)
     FCFuncElement("GetFunctionPointerForDelegateInternal", MarshalNative::GetFunctionPointerForDelegateInternal)

diff --git a/src/coreclr/vm/eeconfig.cpp b/src/coreclr/vm/eeconfig.cpp
@@ -683,7 +683,7 @@ HRESULT EEConfig::sync()
         bLogCCWRefCountChange = true;
 
     fEnableRCWCleanupOnSTAShutdown = (CLRConfig::GetConfigValue(CLRConfig::INTERNAL_EnableRCWCleanupOnSTAShutdown) != 0);
-    m_fBuiltInCOMInteropSupported = Configuration::GetKnobBooleanValue(W("System.Runtime.InteropServices.Marshal.IsComSupported"), true);
+    m_fBuiltInCOMInteropSupported = Configuration::GetKnobBooleanValue(W("System.Runtime.InteropServices.BuiltInComInterop.IsSupported"), true);
 #endif // FEATURE_COMINTEROP
 
 #ifdef _DEBUG

diff --git a/src/coreclr/vm/marshalnative.cpp b/src/coreclr/vm/marshalnative.cpp
@@ -69,10 +69,10 @@ VOID QCALLTYPE MarshalNative::Prelink(MethodDesc * pMD)
     END_QCALL;
 }
 
-// IsComSupported
+// IsBuiltInComSupported
 // Built-in COM support is only checked from the native side to ensure the runtime
 // is in a consistent state
-BOOL QCALLTYPE MarshalNative::IsComSupported()
+BOOL QCALLTYPE MarshalNative::IsBuiltInComSupported()
 {
     QCALL_CONTRACT;
 

diff --git a/src/coreclr/vm/marshalnative.h b/src/coreclr/vm/marshalnative.h
@@ -20,7 +20,7 @@ class MarshalNative
 {
 public:
     static VOID QCALLTYPE Prelink(MethodDesc * pMD);
-    static BOOL QCALLTYPE IsComSupported();
+    static BOOL QCALLTYPE IsBuiltInComSupported();
 
     //====================================================================
     // These methods convert between an HR and and a managed exception.