[mono][aot] Emit marhsalling exception when dealing with MONO_MARSHAL_CONV_OBJECT_IUNKNOWN

src/mono/mono/metadata/marshal-shared.c

@@ -1225,6 +1225,11 @@ mono_marshal_shared_emit_object_to_ptr_conv (MonoMethodBuilder *mb, MonoType *ty
 		mono_mb_emit_byte (mb, CEE_STIND_I);
 		break;
 	}
+	case MONO_MARSHAL_CONV_OBJECT_IUNKNOWN: {
+		char *msg = g_strdup_printf ("Marshaling not supported for COM type MONO_MARSHAL_CONV_OBJECT_IUNKNOWN.");
+		mono_marshal_shared_mb_emit_exception_marshal_directive (mb, msg);
+		break;
+	}
 
 	default: {
 		g_error ("marshalling conversion %d not implemented", conv);

src/mono/wasm/Wasm.Build.Tests/PInvokeTableGeneratorTests.cs

@@ -719,6 +719,44 @@ void GenerateSourceFiles(string outputPath, int baseArg)
             return (buildArgs, output);
         }
 
+        private void EnsureComInteropCompiles(BuildArgs buildArgs, RunHost host, string id)
+        {
+            string programText = @"
+                using System;
+                using System.Runtime.CompilerServices;
+                using System.Runtime.InteropServices;
+                using System.Runtime.InteropServices.ComTypes;
+
+                public class Test
+                {
+                    public static int Main(string[] args)
+                    {
+                        var s = new STGMEDIUM();
+                        ReleaseStgMedium(ref s);
+                        return 42;
+                    }
+
+                    [DllImport(""ole32.dll"")]
+                    internal static extern void ReleaseStgMedium(ref STGMEDIUM medium);
+                }
+
+            ";
+
+            buildArgs = ExpandBuildArgs(buildArgs);
+
+            (string libraryDir, string output) = BuildProject(buildArgs,
+                                        id: id,
+                                        new BuildProjectOptions(
+                                            InitProject: () =>
+                                            {
+                                                File.WriteAllText(Path.Combine(_projectDir!, "Program.cs"), programText);
+                                            },
+                                            Publish: buildArgs.AOT,
+                                            DotnetWasmFromRuntimePack: true));
+
+            Assert.Contains("Generated app bundle at " + libraryDir, output);
+        }
+
         private void EnsureWasmAbiRulesAreFollowed(BuildArgs buildArgs, RunHost host, string id)
         {
             string programText = @"
@@ -885,6 +923,11 @@ public void EnsureWasmAbiRulesAreFollowedInAOT(BuildArgs buildArgs, RunHost host
         public void EnsureWasmAbiRulesAreFollowedInInterpreter(BuildArgs buildArgs, RunHost host, string id) =>
             EnsureWasmAbiRulesAreFollowed(buildArgs, host, id);
 
+        [Theory]
+        [BuildAndRun(host: RunHost.Chrome, aot: true)]
+        public void EnsureComInteropCompilesInAOT(BuildArgs buildArgs, RunHost host, string id) =>
+            EnsureComInteropCompiles(buildArgs, host, id);
+
         [Theory]
         [BuildAndRun(host: RunHost.Chrome, aot: false)]
         public void UCOWithSpecialCharacters(BuildArgs buildArgs, RunHost host, string id)

src/mono/wasm/Wasm.Build.Tests/README.md

@@ -14,7 +14,7 @@ being generated.
 
 - Running:
 
-Linux/macOS: `$ make -C src/mono/wasm run-build-tests`
+Linux/macOS: `$ make -C src/mono/(browser|wasi) run-build-tests`
 Windows: `.\dotnet.cmd build .\src\mono\wasm\Wasm.Build.Tests\Wasm.Build.Tests.csproj -c Release -t:Test -p:TargetOS=browser -p:TargetArchitecture=wasm`
 
 - Specific tests can be run via `XUnitClassName`, and `XUnitMethodName`