[dotnet] Add support for selecting whether to create P/Invoke wrapper…

…s or not. Fixes #4940. (#14961)

* This is a potential mitigation for slower transition to native code when
  exception marshalling is enabled (#14812).
* A minor modification was required in the linker, to make sure any modified
  assemblies are saved.

Fixes #4940.

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -493,6 +493,7 @@
 				PlatformAssembly=$(_PlatformAssemblyName).dll
 				RelativeAppBundlePath=$(_RelativeAppBundlePath)
 				Registrar=$(_BundlerRegistrar)
+				RequirePInvokeWrappers=$(_RequirePInvokeWrappers)
 				RuntimeConfigurationFile=$(_RuntimeConfigurationFile)
 				SdkDevPath=$(_SdkDevPath)
 				SdkRootDirectory=$(_XamarinSdkRootDirectory)

msbuild/Xamarin.MacDev.Tasks.Core/Tasks/ParseBundlerArgumentsTaskBase.cs

@@ -46,6 +46,9 @@ public abstract class ParseBundlerArgumentsTaskBase : XamarinTask {
 		[Output]
 		public string Registrar { get; set; }
 
+		[Output]
+		public string RequirePInvokeWrappers { get; set; }
+
 		// This is input too
 		[Output]
 		public string NoStrip { get; set; }
@@ -148,6 +151,9 @@ public override bool Execute ()
 					case "package-debug-symbols":
 						PackageDebugSymbols = string.IsNullOrEmpty (value) ? "true" : value;
 						break;
+					case "require-pinvoke-wrappers":
+						RequirePInvokeWrappers = string.IsNullOrEmpty (value) ? "true" : value;
+						break;
 					case "registrar":
 						value = hasValue ? value : nextValue; // requires a value, which might be the next option
 						Registrar = value;

msbuild/Xamarin.Shared/Xamarin.Shared.targets

@@ -1782,6 +1782,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 			<Output TaskParameter="Optimize" PropertyName="_BundlerOptimize"/>
 			<Output TaskParameter="PackageDebugSymbols" PropertyName="PackageDebugSymbols" />
 			<Output TaskParameter="Registrar" PropertyName="_BundlerRegistrar" />
+			<Output TaskParameter="RequirePInvokeWrappers" PropertyName="_RequirePInvokeWrappers" />
 			<Output TaskParameter="Verbosity" PropertyName="_BundlerVerbosity" />
 			<Output TaskParameter="XmlDefinitions" ItemName="_BundlerXmlDefinitions" />
 			<Output TaskParameter="NoStrip" PropertyName="EnableAssemblyILStripping" />

tools/common/Application.cs

@@ -611,8 +611,16 @@ public string Name {
 			get { return Path.GetFileNameWithoutExtension (AppDirectory); }
 		}
 
+		bool? requires_pinvoke_wrappers;
 		public bool RequiresPInvokeWrappers {
 			get {
+				if (requires_pinvoke_wrappers.HasValue)
+					return requires_pinvoke_wrappers.Value;
+
+				// By default this is disabled for .NET
+				if (Driver.IsDotNet)
+					return false;
+
 				if (Platform == ApplePlatform.MacOSX)
 					return false;
 
@@ -624,6 +632,9 @@ public bool RequiresPInvokeWrappers {
 
 				return MarshalObjectiveCExceptions == MarshalObjectiveCExceptionMode.ThrowManagedException || MarshalObjectiveCExceptions == MarshalObjectiveCExceptionMode.Abort;
 			}
+			set {
+				requires_pinvoke_wrappers = value;
+			}
 		}
 
 		public string PlatformName {

tools/common/Driver.cs

@@ -253,6 +253,9 @@ static bool ParseOptions (Application app, Mono.Options.OptionSet options, strin
 			options.Add ("rid=", "The runtime identifier we're building for", v => {
 				app.RuntimeIdentifier = v;
 			}, true /* hidden - this is only for build-time --runregistrar support */);
+			options.Add ("require-pinvoke-wrappers:", v => {
+				app.RequiresPInvokeWrappers = ParseBool (v, "--require-pinvoke-wrappers");
+			});
 
 
 			// Keep the ResponseFileSource option at the end.

tools/dotnet-linker/LinkerConfiguration.cs

@@ -57,6 +57,8 @@ public class LinkerConfiguration {
 
 		Dictionary<string, List<MSBuildItem>> msbuild_items = new Dictionary<string, List<MSBuildItem>> ();
 
+		internal PInvokeWrapperGenerator PInvokeWrapperGenerationState;
+
 		public static LinkerConfiguration GetInstance (LinkContext context, bool createIfNotFound = true)
 		{
 			if (!configurations.TryGetValue (context, out var instance) && createIfNotFound) {
@@ -231,6 +233,11 @@ public static LinkerConfiguration GetInstance (LinkContext context, bool createI
 				case "Registrar":
 					Application.ParseRegistrar (value);
 					break;
+				case "RequirePInvokeWrappers":
+					if (!TryParseOptionalBoolean (value, out var require_pinvoke_wrappers))
+						throw new InvalidOperationException ($"Unable to parse the {key} value: {value} in {linker_file}");
+					Application.RequiresPInvokeWrappers = require_pinvoke_wrappers.Value;
+					break;
 				case "RuntimeConfigurationFile":
 					Application.RuntimeConfigurationFile = value;
 					break;
@@ -401,6 +408,7 @@ public void Write ()
 				Console.WriteLine ($"    RelativeAppBundlePath: {RelativeAppBundlePath}");
 				Console.WriteLine ($"    Registrar: {Application.Registrar} (Options: {Application.RegistrarOptions})");
 				Console.WriteLine ($"    RuntimeConfigurationFile: {Application.RuntimeConfigurationFile}");
+				Console.WriteLine ($"    RequirePInvokeWrappers: {Application.RequiresPInvokeWrappers}");
 				Console.WriteLine ($"    SdkDevPath: {Driver.SdkRoot}");
 				Console.WriteLine ($"    SdkRootDirectory: {SdkRootDirectory}");
 				Console.WriteLine ($"    SdkVersion: {SdkVersion}");

tools/dotnet-linker/Steps/GenerateMainStep.cs

@@ -55,6 +55,24 @@ protected override void TryEndProcess ()
 				if (app.EnableDebug)
 					item.Metadata.Add ("Arguments", "-DDEBUG");
 				items.Add (item);
+
+				if (app.RequiresPInvokeWrappers) {
+					var state = Configuration.PInvokeWrapperGenerationState;
+					if (state.Started) {
+						// The generator is 'started' by the linker, which means it may not
+						// be started if the linker was not executed due to re-using cached results.
+						state.End ();
+					}
+					item = new MSBuildItem {
+						Include = state.SourcePath,
+						Metadata = {
+							{ "Arch", abi.AsArchString () },
+						},
+					};
+					if (app.EnableDebug)
+						item.Metadata.Add ("Arguments", "-DDEBUG");
+					items.Add (item);
+				}
 			}
 
 			Configuration.WriteOutputForMSBuild ("_MainFile", items);

tools/linker/MonoTouch.Tuner/ListExportedSymbols.cs

@@ -18,27 +18,56 @@ namespace Xamarin.Linker.Steps
 	public class ListExportedSymbols : BaseStep
 	{
 		PInvokeWrapperGenerator state;
+#if !NET
 		bool skip_sdk_assemblies;
+#endif
+
+		PInvokeWrapperGenerator State {
+			get {
+#if NET
+				if (state is null && DerivedLinkContext.App.RequiresPInvokeWrappers) {
+					Configuration.PInvokeWrapperGenerationState = new PInvokeWrapperGenerator () {
+						App = DerivedLinkContext.App,
+						SourcePath = Path.Combine (Configuration.CacheDirectory, "pinvokes.mm"),
+						HeaderPath = Path.Combine (Configuration.CacheDirectory, "pinvokes.h"),
+						Registrar = DerivedLinkContext.StaticRegistrar,
+					};
+					state = Configuration.PInvokeWrapperGenerationState;
+				}
+#endif
+				return state;
+			}
+		}
+
+#if NET
+		public LinkerConfiguration Configuration {
+			get {
+				return LinkerConfiguration.GetInstance (Context);
+			}
+		}
+#endif
 
 		public DerivedLinkContext DerivedLinkContext {
 			get {
 #if NET
-				return LinkerConfiguration.GetInstance (Context).DerivedLinkContext;
+				return Configuration.DerivedLinkContext;
 #else
 				return (DerivedLinkContext) Context;
 #endif
 			}
 		}
 
-		public ListExportedSymbols () : this (null)
+#if NET
+		public ListExportedSymbols ()
 		{
 		}
-
+#else
 		internal ListExportedSymbols (PInvokeWrapperGenerator state, bool skip_sdk_assemblies = false)
 		{
 			this.state = state;
 			this.skip_sdk_assemblies = skip_sdk_assemblies;
 		}
+#endif
 
 		protected override void ProcessAssembly (AssemblyDefinition assembly)
 		{
@@ -64,23 +93,34 @@ protected override void ProcessAssembly (AssemblyDefinition assembly)
 			if (!hasSymbols)
 				return;
 
+			var modified = false;
 			foreach (var type in assembly.MainModule.Types)
-				ProcessType (type);
+				modified |= ProcessType (type);
+
+			// Make sure the linker saves any changes in the assembly.
+			if (modified) {
+				var action = Context.Annotations.GetAction (assembly);
+				if (action == AssemblyAction.Copy)
+					Context.Annotations.SetAction (assembly, AssemblyAction.Save);
+			}
 		}
 
-		void ProcessType (TypeDefinition type)
+		bool ProcessType (TypeDefinition type)
 		{
+			var modified = false;
 			if (type.HasNestedTypes) {
 				foreach (var nested in type.NestedTypes)
-					ProcessType (nested);
+					modified |= ProcessType (nested);
 			}
 
 			if (type.HasMethods) {
 				foreach (var method in type.Methods)
-					ProcessMethod (method);
+					modified |= ProcessMethod (method);
 			}
 
 			AddRequiredObjectiveCType (type);
+
+			return modified;
 		}
 
 		void AddRequiredObjectiveCType (TypeDefinition type)
@@ -106,20 +146,23 @@ void AddRequiredObjectiveCType (TypeDefinition type)
 			}
 		}
 
-		void ProcessMethod (MethodDefinition method)
+		bool ProcessMethod (MethodDefinition method)
 		{
+			var modified = false;
+
 			if (method.IsPInvokeImpl && method.HasPInvokeInfo && method.PInvokeInfo != null) {
 				var pinfo = method.PInvokeInfo;
 				bool addPInvokeSymbol = false;
 
-				if (state != null) {
+				if (State != null) {
 					switch (pinfo.EntryPoint) {
 					case "objc_msgSend":
 					case "objc_msgSendSuper":
 					case "objc_msgSend_stret":
 					case "objc_msgSendSuper_stret":
 					case "objc_msgSend_fpret":
-						state.ProcessMethod (method);
+						State.ProcessMethod (method);
+						modified = true;
 						break;
 					default:
 						break;
@@ -181,6 +224,8 @@ void ProcessMethod (MethodDefinition method)
 					DerivedLinkContext.RequiredSymbols.AddField ((string) symbol).AddMember (property);
 				}
 			}
+
+			return modified;
 		}
 	}
 }