[runtime] Redirect to our objc_msgSend wrapper functions when needed for .NET code. (#10932)

This makes the mono_dllmap_insert function unnecessary for .NET, so remove it.

Ref: https://github.com/dotnet/runtime/issues/48110
Ref: https://github.com/dotnet/runtime/issues/43204
Ref: #10504

runtime/exports.t4

@@ -323,7 +323,9 @@
 			"const char *", "func",
 			"const char *", "tdll",
 			"const char *", "tfunc"
-		),
+		) {
+			Mode = DotNetMode.OnlyLegacy,
+		},
 
 		#endregion
 

runtime/runtime-internal.h

@@ -31,6 +31,11 @@ extern "C" {
 
 void *xamarin_marshal_return_value (SEL sel, MonoType *mtype, const char *type, MonoObject *retval, bool retain, MonoMethod *method, MethodDescription *desc, GCHandle *exception_gchandle);
 
+void xamarin_dyn_objc_msgSend ();
+void xamarin_dyn_objc_msgSendSuper ();
+void xamarin_dyn_objc_msgSend_stret ();
+void xamarin_dyn_objc_msgSendSuper_stret ();
+
 #ifdef __cplusplus
 }
 #endif

runtime/runtime.m

@@ -1354,7 +1354,9 @@ xamarin_initialize ()
 	xamarin_initialize_dynamic_runtime (NULL);
 #endif
 
+#if !DOTNET
 	xamarin_insert_dllmap ();
+#endif
 
 	MONO_ENTER_GC_UNSAFE;
 
@@ -2449,6 +2451,8 @@ xamarin_create_product_exception_with_inner_exception (int code, GCHandle inner_
 		return exception_gchandle;
 	return handle;
 }
+
+#if !DOTNET
 void
 xamarin_insert_dllmap ()
 {
@@ -2467,6 +2471,7 @@ xamarin_insert_dllmap ()
 	LOG (PRODUCT ": Added dllmap for objc_msgSend");
 #endif // defined (__i386__) || defined (__x86_64__)
 }
+#endif // !DOTNET
 
 #if DOTNET
 void
@@ -2499,6 +2504,20 @@ xamarin_pinvoke_override (const char *libraryName, const char *entrypointName)
 
 	if (!strcmp (libraryName, "__Internal")) {
 		symbol = dlsym (RTLD_DEFAULT, entrypointName);
+#if defined (__i386__) || defined (__x86_64__)
+	} else if (!strcmp (libraryName, "/usr/lib/libobjc.dylib")) {
+		if (xamarin_marshal_objectivec_exception_mode != MarshalObjectiveCExceptionModeDisable) {
+			if (!strcmp (entrypointName, "objc_msgSend")) {
+				symbol = (void *) &xamarin_dyn_objc_msgSend;
+			} else if (!strcmp (entrypointName, "objc_msgSendSuper")) {
+				symbol = (void *) &xamarin_dyn_objc_msgSendSuper;
+			} else if (!strcmp (entrypointName, "objc_msgSend_stret")) {
+				symbol = (void *) &xamarin_dyn_objc_msgSend_stret;
+			} else if (!strcmp (entrypointName, "objc_msgSendSuper_stret")) {
+				symbol = (void *) &xamarin_dyn_objc_msgSendSuper_stret;
+			}
+		}
+#endif // defined (__i386__) || defined (__x86_64__)
 	}
 
 	return symbol;

tests/monotouch-test/ObjCRuntime/ExceptionsTest.cs

@@ -96,10 +96,6 @@ namespace MonoTouchFixtures.ObjCRuntime {
 			Assert.Ignore ("This test only works in debug mode in the simulator.");
 #endif
 
-#if NET && (__MACOS__ || __MACCATALYST__)
-			Assert.Ignore ("Exception marshalling hasn't been completely implemented on macOS/Mac Catalyst yet, due to removal of the dllmap support");
-#endif
-
 			InstallHandlers ();
 
 			try {
@@ -149,10 +145,6 @@ namespace MonoTouchFixtures.ObjCRuntime {
 #endif
 			var hasDebugger = global::System.Diagnostics.Debugger.IsAttached;
 
-#if NET && (__MACOS__ || __MACCATALYST__)
-			Assert.Ignore ("Exception marshalling hasn't been completely implemented on macOS/Mac Catalyst yet, due to removal of the dllmap support");
-#endif
-
 			InstallHandlers ();
 			try {
 				using (var e = new ManagedExceptionTest ()) {

tests/monotouch-test/dotnet/macOS/monotouch-test.csproj

@@ -15,7 +15,6 @@
     <DefineConstants>$(DefineConstants);MONOMAC;XAMMAC_TESTS</DefineConstants>
     <DefineConstants Condition="'$(Configuration)' == 'Debug'">$(DefineConstants);DEBUG;DYNAMIC_REGISTRAR</DefineConstants>
     <RootTestsDirectory>..\..\..</RootTestsDirectory>
-    <MonoBundlingExtraArgs>--marshal-objectivec-exceptions:disable</MonoBundlingExtraArgs>
   </PropertyGroup>
 
   <ItemGroup>

tools/common/Application.cs

@@ -1359,14 +1359,7 @@ namespace Xamarin.Bundler {
 						break;
 					case ApplePlatform.MacOSX:
 					case ApplePlatform.MacCatalyst:
-#if NET
-						// Mono doesn't support dllmaps for Mac Catalyst / macOS in .NET for now:
-						// macOS: https://github.com/dotnet/runtime/issues/43204
-						// Mac Catalyst: https://github.com/dotnet/runtime/issues/48110
-						MarshalObjectiveCExceptions = MarshalObjectiveCExceptionMode.Disable;
-#else
 						MarshalObjectiveCExceptions = EnableDebug ? MarshalObjectiveCExceptionMode.ThrowManagedException : MarshalObjectiveCExceptionMode.Disable;
-#endif
 						break;
 					default:
 						throw ErrorHelper.CreateError (71, Errors.MX0071 /* Unknown platform: {0}. This usually indicates a bug in {1}; please file a bug report at https://github.com/xamarin/xamarin-macios/issues/new with a test case. */, Platform, ProductName);

tools/common/Target.cs

@@ -613,12 +613,7 @@ namespace Xamarin.Bundler {
 			sw.WriteLine ("\txamarin_executable_name = \"{0}\";", App.AssemblyName);
 			if (!App.IsDefaultMarshalManagedExceptionMode)
 				sw.WriteLine ("\txamarin_marshal_managed_exception_mode = MarshalManagedExceptionMode{0};", App.MarshalManagedExceptions);
-#if NET
-			// We require support for dllmap, which isn't in .NET/macOS yet (https://github.com/dotnet/runtime/issues/43204), so disable
-			sw.WriteLine ("\txamarin_marshal_objectivec_exception_mode = MarshalObjectiveCExceptionModeDisable;");
-#else
 			sw.WriteLine ("\txamarin_marshal_objectivec_exception_mode = MarshalObjectiveCExceptionMode{0};", App.MarshalObjectiveCExceptions);
-#endif
 			if (App.DisableLldbAttach.HasValue ? App.DisableLldbAttach.Value : !App.EnableDebug)
 				sw.WriteLine ("\txamarin_disable_lldb_attach = true;");
 			if (App.DisableOmitFramePointer ?? App.EnableDebug)