Fix crossgenning of sparse COM interface types on non-Windows and add test

src/coreclr/src/zap/zapimage.cpp

@@ -1894,7 +1894,6 @@ void ZapImage::TryCompileMethodStub(LPVOID pContext, CORINFO_METHOD_HANDLE hStub
 //-----------------------------------------------------------------------------
 BOOL ZapImage::IsVTableGapMethod(mdMethodDef md)
 {
-#ifdef FEATURE_COMINTEROP
     HRESULT hr;
     DWORD dwAttributes;
 
@@ -1916,9 +1915,6 @@ BOOL ZapImage::IsVTableGapMethod(mdMethodDef md)
 
     // If we make it to here we have a vtable gap method.
     return TRUE;
-#else
-    return FALSE;
-#endif // FEATURE_COMINTEROP
 }
 
 //-----------------------------------------------------------------------------

src/tests/Interop/COM/NETClients/VtableGap/App.manifest

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
+  <assemblyIdentity
+    type="win32"
+    name="NetPrimitivesClient"
+    version="1.0.0.0" />
+
+  <dependency>
+    <dependentAssembly>
+      <!-- RegFree COM -->
+      <assemblyIdentity
+          type="win32"
+          name="COMNativeServer.X"
+          version="1.0.0.0"/>
+    </dependentAssembly>
+  </dependency>
+
+</assembly>

src/tests/Interop/COM/NETClients/VtableGap/ErrorTests.cs

@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace NetClient
+{
+    using System;
+    using System.Runtime.InteropServices;
+    using TestLibrary;
+
+    class ErrorTests
+    {
+        private readonly Server.Contract.IErrorMarshalTesting_VtableGap server;
+        public ErrorTests()
+        {
+            this.server = (Server.Contract.IErrorMarshalTesting_VtableGap)new Server.Contract.Servers.ErrorMarshalTestingClass();
+        }
+
+        public void Run()
+        {
+            this.VerifyReturnHResult();
+        }
+
+        private void VerifyReturnHResult()
+        {
+            Console.WriteLine($"Verify preserved function signature");
+
+            var hrs = new[]
+            {
+                    unchecked((int)0x80004001),
+                    unchecked((int)0x80004003),
+                    unchecked((int)0x80070005),
+                    unchecked((int)0x80070057),
+                    unchecked((int)0x8000ffff),
+                    -1,
+                    1,
+                    2
+                };
+
+            foreach (var hr in hrs)
+            {
+                Assert.AreEqual(hr, this.server.Return_As_HResult_Struct(hr).hr);
+            }
+        }
+    }
+}

src/tests/Interop/COM/NETClients/VtableGap/NETClientVtableGap.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <ApplicationManifest>App.manifest</ApplicationManifest>
+    <!-- ilasm round-trip testing blocked on ILAsm supporting embedding resources. See https://github.com/dotnet/runtime/issues/11412 -->
+    <IlasmRoundTripIncompatible>true</IlasmRoundTripIncompatible>
+    <!-- This test would require the runincontext.exe to include App.manifest describing the COM interfaces -->
+    <UnloadabilityIncompatible>true</UnloadabilityIncompatible>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="Program.cs" />
+    <Compile Include="ErrorTests.cs" />
+    <Compile Include="../../ServerContracts/Server.CoClasses.cs" />
+    <Compile Include="../../ServerContracts/Server.Contracts.cs" />
+    <Compile Include="../../ServerContracts/ServerGuids.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Condition="'$(TargetsWindows)' == 'true'" Include="../../NativeServer/CMakeLists.txt" />
+    <ProjectReference Include="$(TestSourceDir)Common/CoreCLRTestLibrary/CoreCLRTestLibrary.csproj" />
+  </ItemGroup>
+</Project>

src/tests/Interop/COM/NETClients/VtableGap/Program.cs

@@ -0,0 +1,48 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace NetClient
+{
+    using System;
+    using System.Threading;
+    using System.Runtime.InteropServices;
+    using TestLibrary;
+
+    class Program
+    {
+        static int Main(string[] doNotUse)
+        {
+            // RegFree COM is not supported on Windows Nano
+            if (TestLibrary.Utilities.IsWindowsNanoServer)
+            {
+                return 100;
+            }
+
+            // COM is not supported off Windows.
+            // However, we want to test non-Windows crossgen on vtable gap members
+            // so we still build and run this test on non-Windows so the crossgen test
+            // runs exercise that path.
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                return 100;
+            }
+
+            try
+            {
+                RunTests();
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine($"Test Failure: {e}");
+                return 101;
+            }
+
+            return 100;
+        }
+
+        private static void RunTests()
+        {
+            new ErrorTests().Run();
+        }
+    }
+}

src/tests/Interop/COM/ServerContracts/Server.Contracts.cs

@@ -203,6 +203,16 @@ public interface IErrorMarshalTesting
         HResult Return_As_HResult_Struct(int hresultToReturn);
     }
 
+    [ComImport]
+    [Guid("592386A5-6837-444D-9DE3-250815D18556")]
+    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
+    public interface IErrorMarshalTesting_VtableGap
+    {
+        void _VtblGap1_2();
+        [PreserveSig]
+        HResult Return_As_HResult_Struct(int hresultToReturn);
+    }
+
     public enum IDispatchTesting_Exception
     {
         Disp,