[Foundation] Don't dispose tagged pointers. Fixes #21425.

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -156,8 +156,19 @@
 
 		<!-- Directory to store project specific stamp files used by certain targets for incremental builds -->
 		<_MaciOSStampDirectory>$(IntermediateOutputPath)stamp\</_MaciOSStampDirectory>
+
+		<!-- Our own runtime features -->
+
+		<!-- Set default DisposeTaggedPointers value, we stop disposing them by default in .NET 10 -->
+		<!-- The default logic here must match the default logic in NSObject.DisposeTaggedPointers -->
+		<DisposeTaggedPointers Condition="'$(DisposeTaggedPointers)' == '' And $([MSBuild]::VersionGreaterThanOrEquals($(TargetFrameworkVersion), 10.0))">false</DisposeTaggedPointers>
+		<DisposeTaggedPointers Condition="'$(DisposeTaggedPointers)' == ''">true</DisposeTaggedPointers>
 	</PropertyGroup>
 
+	<ItemGroup>
+		<RuntimeHostConfigurationOption Include="Foundation.NSObject.DisposeTaggedPointers" Condition="'$(DisposeTaggedPointers)' != ''" Value="$(DisposeTaggedPointers)" Trim="true" />
+	</ItemGroup>
+
 	<PropertyGroup>
 		<TargetPlatformSupported Condition=" '$(TargetPlatformIdentifier)' == '$(_PlatformName)' ">true</TargetPlatformSupported>
 	</PropertyGroup>

src/Foundation/NSObject2.cs

@@ -991,14 +991,64 @@ internal void ClearHandle ()
 			handle = NativeHandle.Zero;
 		}
 
+		// This option is changed by setting the DisposeTaggedPointers MSBuild property in the project file.
+		static bool? dispose_tagged_pointers;
+		static bool DisposeTaggedPointers {
+			get {
+				if (!dispose_tagged_pointers.HasValue) {
+					if (AppContext.TryGetSwitch ("Foundation.NSObject.DisposeTaggedPointers", out var dtp)) {
+						dispose_tagged_pointers = dtp;
+					} else {
+						// The default logic here must match how we set the default value for the DisposeTaggedPointers MSBuild property.
+#if NET10_0_OR_GREATER
+						dispose_tagged_pointers = false;
+#else
+						dispose_tagged_pointers = true;
+#endif
+					}
+				}
+				return dispose_tagged_pointers.Value;
+			}
+		}
+
 		/// <include file="../../docs/api/Foundation/NSObject.xml" path="/Documentation/Docs[@DocId='M:Foundation.NSObject.Dispose(System.Boolean)']/*" />
 		protected virtual void Dispose (bool disposing)
 		{
 			if (disposed)
 				return;
 			disposed = true;
 
-			if (handle != NativeHandle.Zero) {
+			var isTaggedPointerThatShouldNotBeDisposed = false;
+			if (!DisposeTaggedPointers) {
+				/* Tagged pointers are limited to 64bit, which is all we support anyway.
+				 *
+				 * The bit that identifies if a pointer is a tagged pointer is:
+				 *
+				 * Arm64 (everywhere): most significant bit
+				 * Simulators (both on arm64 and x64 desktops): most significant bit
+				 * Desktop/x64 (macOS + Mac Catalyst): least significant bit
+				 *
+				 * Ref: https://github.com/apple-oss-distributions/objc4/blob/89543e2c0f67d38ca5211cea33f42c51500287d5/runtime/objc-internal.h#L603-L672
+				 */
+#if __MACOS__ || __MACCATALYST__
+				ulong _OBJC_TAG_MASK;
+				if (Runtime.IsARM64CallingConvention) {
+					_OBJC_TAG_MASK = 1UL << 63;
+				} else {
+					_OBJC_TAG_MASK = 1UL;
+				}
+#else
+				const ulong _OBJC_TAG_MASK = 1UL << 63;
+#endif
+
+				unchecked {
+					var ulongHandle = (ulong) (IntPtr) handle;
+					var isTaggedPointer = (ulongHandle & _OBJC_TAG_MASK) == _OBJC_TAG_MASK;
+					isTaggedPointerThatShouldNotBeDisposed = isTaggedPointer;
+				}
+			}
+
+			if (!isTaggedPointerThatShouldNotBeDisposed && handle != NativeHandle.Zero) {
 				if (disposing) {
 					ReleaseManagedRef ();
 				} else {

src/ILLink.Substitutions.MacCatalyst.xml

@@ -1,5 +1,9 @@
 <linker>
   <assembly fullname="Microsoft.MacCatalyst">
+    <type fullname="Foundation.NSObject">
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="false" value="false" />
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="true" value="true" />
+    </type>
     <type fullname="ObjCRuntime.Dlfcn">
       <method signature="System.Void WarnOnce()" body="stub" feature="System.Diagnostics.Debugger.IsSupported" featurevalue="false" />
     </type>

src/ILLink.Substitutions.ios.xml

@@ -1,5 +1,9 @@
 <linker>
   <assembly fullname="Microsoft.iOS">
+    <type fullname="Foundation.NSObject">
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="false" value="false" />
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="true" value="true" />
+    </type>
     <type fullname="ObjCRuntime.Dlfcn">
       <method signature="System.Void WarnOnce()" body="stub" feature="System.Diagnostics.Debugger.IsSupported" featurevalue="false" />
     </type>

src/ILLink.Substitutions.macOS.xml

@@ -1,5 +1,9 @@
 <linker>
   <assembly fullname="Microsoft.macOS">
+    <type fullname="Foundation.NSObject">
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="false" value="false" />
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="true" value="true" />
+    </type>
     <type fullname="ObjCRuntime.Dlfcn">
       <method signature="System.Void WarnOnce()" body="stub" feature="System.Diagnostics.Debugger.IsSupported" featurevalue="false" />
     </type>

src/ILLink.Substitutions.tvos.xml

@@ -1,5 +1,9 @@
 <linker>
   <assembly fullname="Microsoft.tvOS">
+    <type fullname="Foundation.NSObject">
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="false" value="false" />
+      <method signature="System.Boolean get_DisposeTaggedPointers()" body="stub" feature="Foundation.NSObject.DisposeTaggedPointers" featurevalue="true" value="true" />
+    </type>
     <type fullname="ObjCRuntime.Dlfcn">
       <method signature="System.Void WarnOnce()" body="stub" feature="System.Diagnostics.Debugger.IsSupported" featurevalue="false" />
     </type>

tests/common/shared-dotnet.mk

@@ -83,7 +83,7 @@ endif
 PLATFORM_UPPERCASE:=$(shell echo $(PLATFORM) | tr 'a-z' 'A-Z')
 
 ifneq ($(RUNTIMEIDENTIFIERS)$(RUNTIMEIDENTIFIER),)
-$(error "Don't set RUNTIMEIDENTIFIER or RUNTIMEIDENTIFIERS, set RID instead")
+$(error "Don't set RUNTIMEIDENTIFIER or RUNTIMEIDENTIFIERS, set RID instead (RUNTIMEIDENTIFIER=$(RUNTIMEIDENTIFIER), RUNTIMEIDENTIFIERS=$(RUNTIMEIDENTIFIERS))")
 endif
 
 ifeq ($(RID),)

tests/dotnet/DisposeTaggedPointersTestApp/AppDelegate.cs

@@ -0,0 +1,93 @@
+using System;
+using System.Runtime.InteropServices;
+
+using Foundation;
+
+namespace DisposeTaggedPointersTestApp {
+	public class Program {
+		static int Main (string [] args)
+		{
+			var testCaseString = Environment.GetEnvironmentVariable ("TEST_CASE");
+			if (string.IsNullOrEmpty (testCaseString)) {
+				Console.WriteLine ($"The environment variable TEST_CASE wasn't set.");
+				return 2;
+			}
+#if NET10_0_OR_GREATER
+			var taggedPointersDisposedByDefault = false;
+#else
+			var taggedPointersDisposedByDefault = true;
+#endif
+			switch (testCaseString) {
+			case "DisableWithAppContext":
+				AppContext.SetSwitch ("Foundation.NSObject.DisposeTaggedPointers", false);
+				if (ThrowsObjectDisposedExceptions ()) {
+					Console.WriteLine ($"❌ {testCaseString}: Failure: unexpected ObjectDisposedException when DisposeTaggedPointers=false");
+					return 1;
+				}
+
+				Console.WriteLine ($"✅ {testCaseString}: Success");
+				return 0;
+			case "EnableWithAppContext":
+				AppContext.SetSwitch ("Foundation.NSObject.DisposeTaggedPointers", true);
+				if (!ThrowsObjectDisposedExceptions ()) {
+					Console.WriteLine ($"❌ {testCaseString}: Failure: unexpected lack of ObjectDisposedException when DisposeTaggedPointers=true");
+					return 1;
+				}
+
+				Console.WriteLine ($"✅ {testCaseString}: Success");
+				return 0;
+			case "DisableWithMSBuildPropertyTrimmed":
+				if (ThrowsObjectDisposedExceptions ()) {
+					Console.WriteLine ($"❌ {testCaseString}: Failure: unexpected ObjectDisposedException when DisposeTaggedPointers=false");
+					return 1;
+				}
+
+				Console.WriteLine ($"✅ {testCaseString}: Success");
+				return 0;
+			case "EnableWithMSBuildPropertyTrimmed":
+				if (!ThrowsObjectDisposedExceptions ()) {
+					Console.WriteLine ($"❌ {testCaseString}: Failure: unexpected lack of ObjectDisposedException when DisposeTaggedPointers=true");
+					return 1;
+				}
+
+				Console.WriteLine ($"✅ {testCaseString}: Success");
+				return 0;
+			case "DisableWithMSBuildPropertyUntrimmed": {
+				var throws = ThrowsObjectDisposedExceptions ();
+				if (throws == taggedPointersDisposedByDefault) {
+					Console.WriteLine ($"❌ {testCaseString}: Failure: unexpected ObjectDisposedException when DisposeTaggedPointers=false");
+					return 1;
+				}
+
+				Console.WriteLine ($"✅ {testCaseString}: Success");
+				return 0;
+			}
+			case "EnableWithMSBuildPropertyUntrimmed": {
+				var throws = ThrowsObjectDisposedExceptions ();
+				if (throws != taggedPointersDisposedByDefault) {
+					Console.WriteLine ($"❌ {testCaseString}: Failure: unexpected lack of ObjectDisposedException when DisposeTaggedPointers=true");
+					return 1;
+				}
+
+				Console.WriteLine ($"✅ {testCaseString}: Success");
+				return 0;
+			}
+			case "Default": {
+				var throws = ThrowsObjectDisposedExceptions ();
+				if (throws != taggedPointersDisposedByDefault) {
+					Console.WriteLine ($"❌ {testCaseString}: Failure: Expected ObjectDisposedException: {taggedPointersDisposedByDefault} Threw ObjectDisposedException: {throws}");
+					return 1;
+				}
+
+				Console.WriteLine ($"✅ {testCaseString}: Success");
+				return 0;
+			}
+			default:
+				Console.WriteLine ($"❌ Unknown test case: {testCaseString}");
+				return 2;
+			}
+		}
+
+		static bool ThrowsObjectDisposedExceptions () => MonoTouchFixtures.ObjCRuntime.TaggedPointerTest.ThrowsObjectDisposedExceptions ();
+	}
+}

tests/dotnet/DisposeTaggedPointersTestApp/Directory.Build.props

@@ -0,0 +1,7 @@
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+	<PropertyGroup Condition="'$(SetAppendRuntimeIdentifierToOutputPathToFalse)' == 'true'">
+		<!-- Used by the AppendRuntimeIdentifierToOutputPath_* tests -->
+		<AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
+	</PropertyGroup>
+	<Import Project="$(MSBuildThisFileDirectory)../../Directory.Build.props" />
+</Project>

tests/dotnet/DisposeTaggedPointersTestApp/MacCatalyst/DisposeTaggedPointersTestApp.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/DisposeTaggedPointersTestApp/MacCatalyst/Makefile

@@ -0,0 +1 @@
+include ../shared.mk

tests/dotnet/DisposeTaggedPointersTestApp/Makefile

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

tests/dotnet/DisposeTaggedPointersTestApp/iOS/DisposeTaggedPointersTestApp.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/DisposeTaggedPointersTestApp/iOS/Makefile

@@ -0,0 +1 @@
+include ../shared.mk

tests/dotnet/DisposeTaggedPointersTestApp/macOS/DisposeTaggedPointersTestApp.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/DisposeTaggedPointersTestApp/macOS/Makefile

@@ -0,0 +1 @@
+include ../shared.mk

tests/dotnet/DisposeTaggedPointersTestApp/shared.csproj

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project>
+	<PropertyGroup>
+		<OutputType>Exe</OutputType>
+
+		<ApplicationTitle>DisposeTaggedPointersTestApp</ApplicationTitle>
+		<ApplicationId>com.xamarin.disposetaggedpointerstestapp</ApplicationId>
+
+		<UseInterpreter>true</UseInterpreter> <!-- to speed up the test run -->
+	</PropertyGroup>
+
+	<Import Project="../../common/shared-dotnet.csproj" />
+
+	<ItemGroup>
+		<Compile Include="../*.cs" />
+		<Compile Include="../../../monotouch-test/ObjCRuntime/TaggedPointerTest.Shared.cs" />
+	</ItemGroup>
+</Project>

tests/dotnet/DisposeTaggedPointersTestApp/shared.mk

@@ -0,0 +1,44 @@
+TOP=../../../..
+TESTNAME=DisposeTaggedPointersTestApp
+include $(TOP)/tests/common/shared-dotnet.mk
+
+export RUNTIMEIDENTIFIER=
+export RUNTIMEIDENTIFIERS=
+
+.stamp-restore:
+	$(Q) $(DOTNET) restore
+	$(Q) touch $@
+
+define Test
+clean-$(2):
+	$(Q) rm -f .stamp-build-$(2)
+	$(Q) rm -rf bin/$(1) obj/$(1)
+CLEAN_TARGETS+=clean-$(2)
+
+.stamp-build-$(2): .stamp-restore
+	$(MAKE) build CONFIG=$(1) BUILD_ARGUMENTS="/tl:off $(3)"
+	$(Q) touch $$@
+BUILD_TARGETS+=.stamp-build-$(2)
+
+run-$(2): export TEST_CASE=$(1)
+run-$(2): .stamp-build-$(2)
+	$(MAKE) run-bare CONFIG=$(1)
+RUN_TARGETS+=run-$(2)
+
+test-$(2): run-$(2)
+endef
+
+$(eval $(call Test,Default,default))
+$(eval $(call Test,DisableWithAppContext,disablewithappcontext))
+$(eval $(call Test,EnableWithAppContext,enablewithappcontext))
+$(eval $(call Test,DisableWithMSBuildPropertyUntrimmed,disablewithmsbuildpropertyuntrimmed,/p:DisposeTaggedPointers=false /p:_LinkMode=None))
+$(eval $(call Test,EnableWithMSBuildPropertyUntrimmed,enablewithmsbuildpropertyuntrimmed,/p:DisposeTaggedPointers=true /p:_LinkMode=None))
+$(eval $(call Test,DisableWithMSBuildPropertyTrimmed,disablewithmsbuildpropertytrimmed,/p:DisposeTaggedPointers=false /p:_LinkMode=SdkOnly))
+$(eval $(call Test,EnableWithMSBuildPropertyTrimmed,enablewithmsbuildpropertytrimmed,/p:DisposeTaggedPointers=true /p:_LinkMode=SdkOnly))
+
+build-all: $(BUILD_TARGETS)
+clean-all:: $(CLEAN_TARGETS)
+	$(Q) rm -f .stamp-* *.binlog
+test-all run-tests run-all run: $(RUN_TARGETS)
+
+.PHONY: $(TEST_CASES)

tests/dotnet/DisposeTaggedPointersTestApp/tvOS/DisposeTaggedPointersTestApp.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/DisposeTaggedPointersTestApp/tvOS/Makefile

@@ -0,0 +1 @@
+include ../shared.mk

tests/dotnet/UnitTests/ProjectTest.cs

@@ -3727,6 +3727,31 @@ public void InvalidSupportedOSPlatformVersion (ApplePlatform platform, string ru
 			AssertErrorMessages (errors, $"The SupportedOSPlatformVersion value '{version}' in the project file is lower than the minimum value '{minVersion}'.");
 		}
 
+
+		[TestCase (ApplePlatform.MacOSX)]
+		[TestCase (ApplePlatform.MacCatalyst)]
+		public void DisposeTaggedPointersTest (ApplePlatform platform)
+		{
+			var project = "DisposeTaggedPointersTestApp";
+			Configuration.IgnoreIfIgnoredPlatform (platform);
+
+			var project_path = GetProjectPath (project, platform: platform);
+			Clean (project_path);
+
+			var arguments = new string [] {
+				"-C", Path.GetDirectoryName (project_path)!,
+				"clean-all"
+			};
+			AssertExecute ("make", arguments, out var _);
+
+			arguments = new string [] {
+				"-C", Path.GetDirectoryName (project_path)!,
+				"test-all",
+				"-j",
+			};
+			AssertExecute ("make", arguments, out var _);
+		}
+
 		// macOS doesn't support UseNativeHttpHandler / any of our native http handlers being the default http handler.
 		[Test]
 		[TestCase (ApplePlatform.MacCatalyst, "NSUrlSessionHandler", "true")]