[tools/msbuild] Add support for mergeable libraries. Fixes #20262.

docs/building-apps/build-properties.md

@@ -1702,6 +1702,25 @@ The full path to the `strip` command-line tool.
 
 The default behavior is to use `xcrun strip`.
 
+## StripMergeableLibraries
+
+A boolean property that specifies whether static linking metadata (`LC_ATOM_INFO`)
+is removed from mergeable libraries embedded in the app bundle.
+
+Mergeable libraries are dynamic libraries that also contain metadata for static
+linking. This metadata can roughly double the size of the library. When this
+property is `true`, the metadata is stripped to reduce app size.
+
+The default value is the value of the `Optimize` property, which means `Release`
+builds strip mergeable library metadata by default, while `Debug` builds preserve
+it.
+
+```xml
+<PropertyGroup>
+  <StripMergeableLibraries>true</StripMergeableLibraries>
+</PropertyGroup>
+```
+
 ## SupportedOSPlatformVersion
 
 Specifies the minimum OS version the app can run on.

msbuild/Xamarin.MacDev.Tasks/Tasks/StripMergeableLibraryMetadata.cs

@@ -0,0 +1,127 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+
+using Microsoft.Build.Framework;
+using Xamarin.Messaging.Build.Client;
+
+#nullable enable
+
+namespace Xamarin.MacDev.Tasks {
+	// Strips LC_ATOM_INFO (mergeable library metadata) from frameworks and dylibs in an app bundle.
+	public class StripMergeableLibraryMetadata : XamarinTask, ITaskCallback {
+		#region Inputs
+
+		// The Frameworks directory inside the app bundle.
+		public string FrameworksDirectory { get; set; } = string.Empty;
+
+		// Additional directories to scan for mergeable dylibs (e.g. MonoBundle).
+		public string [] DylibDirectories { get; set; } = [];
+
+		public string StripPath { get; set; } = string.Empty;
+
+		public string StampDirectory { get; set; } = string.Empty;
+
+		[Output]
+		public ITaskItem [] FileWrites { get; set; } = [];
+
+		#endregion
+
+		public override bool Execute ()
+		{
+			if (ShouldExecuteRemotely ())
+				return ExecuteRemotely ();
+
+			StripFrameworks ();
+			StripDylibs ();
+
+			return !Log.HasLoggedErrors;
+		}
+
+		void StripFrameworks ()
+		{
+			if (string.IsNullOrEmpty (FrameworksDirectory) || !Directory.Exists (FrameworksDirectory))
+				return;
+
+			foreach (var framework in Directory.GetDirectories (FrameworksDirectory, "*.framework")) {
+				var name = Path.GetFileNameWithoutExtension (framework);
+				var executable = Path.Combine (framework, name);
+				StripIfMergeable (executable);
+			}
+		}
+
+		void StripDylibs ()
+		{
+			if (DylibDirectories is null)
+				return;
+
+			foreach (var dir in DylibDirectories) {
+				if (string.IsNullOrEmpty (dir) || !Directory.Exists (dir))
+					continue;
+
+				foreach (var dylib in Directory.GetFiles (dir, "*.dylib")) {
+					StripIfMergeable (dylib);
+				}
+			}
+		}
+
+		void StripIfMergeable (string path)
+		{
+			if (!File.Exists (path))
+				return;
+
+			var stamp = GetStampPath (path);
+			if (stamp is not null && File.Exists (stamp) && File.GetLastWriteTimeUtc (stamp) >= File.GetLastWriteTimeUtc (path)) {
+				Log.LogMessage (MessageImportance.Low, $"Skipping unchanged library: {path}");
+				FileWrites = FileWrites.Append (new Microsoft.Build.Utilities.TaskItem (stamp)).ToArray ();
+				return;
+			}
+
+			if (!MachO.IsMergeableLibrary (path)) {
+				Log.LogMessage (MessageImportance.Low, $"Not a mergeable library: {path}");
+				WriteStamp (stamp);
+				return;
+			}
+
+			Log.LogMessage (MessageImportance.Normal, $"Stripping mergeable library metadata from: {path}");
+
+			var args = new List<string> ();
+			var stripExecutable = GetExecutable (args, "strip", StripPath);
+			args.Add ("-no_atom_info");
+			args.Add ("-S");
+			args.Add (Path.GetFullPath (path));
+			ExecuteAsync (stripExecutable, args).Wait ();
+			WriteStamp (stamp);
+		}
+
+		string? GetStampPath (string path)
+		{
+			if (string.IsNullOrEmpty (StampDirectory))
+				return null;
+
+			using var sha = SHA256.Create ();
+			var hash = sha.ComputeHash (Encoding.UTF8.GetBytes (Path.GetFullPath (path)));
+			var name = BitConverter.ToString (hash).Replace ("-", "");
+			return Path.Combine (StampDirectory, name + ".stamp");
+		}
+
+		void WriteStamp (string? stamp)
+		{
+			if (stamp is null)
+				return;
+
+			Directory.CreateDirectory (StampDirectory);
+			File.WriteAllText (stamp, string.Empty);
+			FileWrites = FileWrites.Append (new Microsoft.Build.Utilities.TaskItem (stamp)).ToArray ();
+		}
+
+		public bool ShouldCopyToBuildServer (ITaskItem item) => false;
+
+		public bool ShouldCreateOutputFile (ITaskItem item) => false;
+
+		public IEnumerable<ITaskItem> GetAdditionalItemsToBeCopied () => Enumerable.Empty<ITaskItem> ();
+	}
+}

msbuild/Xamarin.MacDev.Tasks/Tasks/SymbolStrip.cs

@@ -29,6 +29,9 @@ public class SymbolStrip : XamarinParallelTask, ITaskCallback {
 
 		// This can also be specified as metadata on the Executable item (as 'Kind')
 		public string Kind { get; set; } = string.Empty;
+
+		// Whether to strip mergeable library metadata (LC_ATOM_INFO) from frameworks and dylibs.
+		public bool StripMergeableLibraries { get; set; }
 		#endregion
 
 		bool GetIsFrameworkOrDynamicLibrary (ITaskItem item)
@@ -66,6 +69,11 @@ void ExecuteStrip (ITaskItem item)
 				// Only remove debug symbols from frameworks.
 				args.Add ("-S");
 				args.Add ("-x");
+				if (StripMergeableLibraries) {
+					// Remove atom info (LC_ATOM_INFO) from mergeable libraries to reduce size.
+					// This is a no-op for non-mergeable libraries.
+					args.Add ("-no_atom_info");
+				}
 			}
 
 			args.Add (Path.GetFullPath (item.ItemSpec));

msbuild/Xamarin.Shared/Xamarin.Shared.props

@@ -132,6 +132,10 @@ Copyright (C) 2020 Microsoft. All rights reserved.
 		<NoSymbolStrip Condition="'$(NoSymbolStrip)' == '' And '$(SdkIsSimulator)' == 'true'">true</NoSymbolStrip>
 		<NoSymbolStrip Condition="'$(NoSymbolStrip)' == ''">false</NoSymbolStrip>
 
+		<!-- StripMergeableLibraries: remove static linking metadata (LC_ATOM_INFO) from mergeable libraries to reduce app size -->
+		<!-- Default to true when optimizing (typically Release builds) -->
+		<StripMergeableLibraries Condition="'$(StripMergeableLibraries)' == ''">$(Optimize)</StripMergeableLibraries>
+
 		<!-- NoDSymUtil -->
 		<!-- Xamarin.Mac never had an equivalent for MtouchNoDSymUtil and never produced them -> now, produce them by default when archiving -->
 		<NoDSymUtil Condition="'$(NoDSymUtil)' == '' And '$(_PlatformName)' != 'macOS'">$(MtouchNoDSymUtil)</NoDSymUtil>

msbuild/Xamarin.Shared/Xamarin.Shared.targets

@@ -100,6 +100,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 	<UsingTask Runtime="$(_TaskRuntime)" TaskName="Xamarin.MacDev.Tasks.SmartCopy" AssemblyFile="$(_TaskAssemblyName)" />
 	<UsingTask Runtime="$(_TaskRuntime)" TaskName="Xamarin.MacDev.Tasks.SpotlightIndexer" AssemblyFile="$(_TaskAssemblyName)" />
 	<UsingTask Runtime="$(_TaskRuntime)" TaskName="Xamarin.MacDev.Tasks.StripFrameworkHeaders" AssemblyFile="$(_TaskAssemblyName)" />
+	<UsingTask Runtime="$(_TaskRuntime)" TaskName="Xamarin.MacDev.Tasks.StripMergeableLibraryMetadata" AssemblyFile="$(_TaskAssemblyName)" />
 	<UsingTask Runtime="$(_TaskRuntime)" TaskName="Xamarin.MacDev.Tasks.SymbolStrip" AssemblyFile="$(_TaskAssemblyName)" />
 	<UsingTask Runtime="$(_TaskRuntime)" TaskName="Xamarin.MacDev.Tasks.TextureAtlas" AssemblyFile="$(_TaskAssemblyName)" />
 	<UsingTask Runtime="$(_TaskRuntime)" TaskName="Xamarin.MacDev.Tasks.UnpackLibraryResources" AssemblyFile="$(_TaskAssemblyName)" />
@@ -3247,6 +3248,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 			_ComputeXCFrameworkDSyms;
 			_CopyXCFrameworkDSyms;
 			_NativeStripFiles;
+			_StripMergeableLibraryMetadata;
 			_NotifySpotlight;
 		</_PostProcessAppBundleDependsOn>
 	</PropertyGroup>
@@ -3395,6 +3397,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 			Executable="$(_AppContainerDir)%(_NativeStripItems.Identity)"
 			Kind="%(_NativeStripItems.Kind)"
 			MaxDegreeOfParallelism="$(SymbolStripMaxDegreeOfParallelism)"
+			StripMergeableLibraries="$(StripMergeableLibraries)"
 			StripPath="$(StripPath)"
 			SymbolFile="%(_NativeStripItems.SymbolFile)"
 			SymbolFileLocalPath="%(_NativeStripItems.SymbolFileLocalPath)"
@@ -3423,6 +3426,29 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 		/>
 	</Target>
 
+	<!--
+		Strip mergeable library metadata (LC_ATOM_INFO) from frameworks and dylibs in the app bundle.
+		This runs independently of the regular symbol stripping, because symbol stripping
+		may be disabled (e.g. simulator builds, debug builds, macOS/MacCatalyst).
+	-->
+	<Target
+		Name="_StripMergeableLibraryMetadata"
+		Condition="'$(_PostProcess)' == 'true' And '$(StripMergeableLibraries)' == 'true'"
+		DependsOnTargets="_PreparePostProcessing"
+		>
+
+		<StripMergeableLibraryMetadata
+			SessionId="$(BuildSessionId)"
+			Condition="'$(IsMacEnabled)' == 'true'"
+			FrameworksDirectory="$(_AppFrameworksPath)"
+			DylibDirectories="$(_AppBundlePath);$(_AppContentsPath)"
+			StampDirectory="$(DeviceSpecificIntermediateOutputPath)mergeable-library-metadata"
+			StripPath="$(StripPath)"
+			>
+			<Output TaskParameter="FileWrites" ItemName="FileWrites" />
+		</StripMergeableLibraryMetadata>
+	</Target>
+
 	<!-- make sure spotlight indexes everything we've built -->
 	<Target
 		Name="_NotifySpotlight"

tests/dotnet/NativeMergeableDylibReferencesApp/AppDelegate.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Runtime.InteropServices;
+
+using Foundation;
+
+namespace NativeMergeableDylibReferencesApp {
+	public class Program {
+		[DllImport ("libMergeableFramework.dylib")]
+		static extern int theUltimateAnswer ();
+
+		static int Main (string [] args)
+		{
+			Console.WriteLine ($"Mergeable Dynamic library: {theUltimateAnswer ()}");
+
+			GC.KeepAlive (typeof (NSObject)); // prevent linking away the platform assembly
+
+			Console.WriteLine (Environment.GetEnvironmentVariable ("MAGIC_WORD"));
+
+			return 0;
+		}
+	}
+}

tests/dotnet/NativeMergeableDylibReferencesApp/MacCatalyst/NativeMergeableDylibReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-maccatalyst</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>

tests/dotnet/NativeMergeableDylibReferencesApp/Makefile

@@ -0,0 +1,2 @@
+TOP=../../..
+include $(TOP)/tests/common/shared-dotnet-test.mk

tests/dotnet/NativeMergeableDylibReferencesApp/iOS/NativeMergeableDylibReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-ios</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>

tests/dotnet/NativeMergeableDylibReferencesApp/macOS/NativeMergeableDylibReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-macos</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>

tests/dotnet/NativeMergeableDylibReferencesApp/shared.csproj

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project>
+	<PropertyGroup>
+		<OutputType>Exe</OutputType>
+
+		<ApplicationTitle>NativeMergeableDylibReferencesApp</ApplicationTitle>
+		<ApplicationId>com.xamarin.nativemergeabledylibreferences</ApplicationId>
+		<ApplicationVersion>1.0</ApplicationVersion>
+	</PropertyGroup>
+
+	<Import Project="../../common/shared-dotnet.csproj" />
+
+	<ItemGroup>
+		<NativeReference Include="..\..\..\test-libraries\.libs\$(NativeLibName)\libMergeableFramework.dylib" Kind="Dynamic" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<Compile Include="../*.cs" />
+	</ItemGroup>
+</Project>

tests/dotnet/NativeMergeableDylibReferencesApp/tvOS/NativeMergeableDylibReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-tvos</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>

tests/dotnet/NativeMergeableFrameworkReferencesApp/AppDelegate.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Runtime.InteropServices;
+
+using Foundation;
+
+namespace NativeMergeableFrameworkReferencesApp {
+	public class Program {
+		[DllImport ("XMergeableTest.framework/XMergeableTest")]
+		static extern int theUltimateAnswer ();
+
+		static int Main (string [] args)
+		{
+			Console.WriteLine ($"Mergeable Framework: {theUltimateAnswer ()}");
+
+			GC.KeepAlive (typeof (NSObject)); // prevent linking away the platform assembly
+
+			Console.WriteLine (Environment.GetEnvironmentVariable ("MAGIC_WORD"));
+
+			return 0;
+		}
+	}
+}

tests/dotnet/NativeMergeableFrameworkReferencesApp/MacCatalyst/NativeMergeableFrameworkReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-maccatalyst</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>

tests/dotnet/NativeMergeableFrameworkReferencesApp/Makefile

@@ -0,0 +1,2 @@
+TOP=../../..
+include $(TOP)/tests/common/shared-dotnet-test.mk

tests/dotnet/NativeMergeableFrameworkReferencesApp/iOS/NativeMergeableFrameworkReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-ios</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>

tests/dotnet/NativeMergeableFrameworkReferencesApp/macOS/NativeMergeableFrameworkReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-macos</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>

tests/dotnet/NativeMergeableFrameworkReferencesApp/shared.csproj

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project>
+	<PropertyGroup>
+		<OutputType>Exe</OutputType>
+
+		<ApplicationTitle>NativeMergeableFrameworkReferencesApp</ApplicationTitle>
+		<ApplicationId>com.xamarin.nativemergeableframeworkreferences</ApplicationId>
+		<ApplicationVersion>1.0</ApplicationVersion>
+	</PropertyGroup>
+
+	<Import Project="../../common/shared-dotnet.csproj" />
+
+	<ItemGroup>
+		<NativeReference Include="..\..\..\test-libraries\.libs\$(NativeLibName)\XMergeableTest.framework" Kind="Framework" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<Compile Include="../*.cs" />
+	</ItemGroup>
+</Project>

tests/dotnet/NativeMergeableFrameworkReferencesApp/tvOS/NativeMergeableFrameworkReferencesApp.csproj

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-tvos</TargetFramework>
+	</PropertyGroup>
+	<Import Project="..\shared.csproj" />
+</Project>