[runtime] Replace stale object map entries when completing deferred registration

[rolfbjarne]

Addresses review feedback on PR #26424: RegisterNSObject(..., onlyIfNeeded: true) previously bailed out on object_map.ContainsKey(ptr) alone, without checking whether the existing entry's weak GCHandle.Target was still alive. If a native pointer was reused and the previous entry's target had already been collected (without the native object dying through the normal path), the stale entry would block registration of the new wrapper — leaving it unregistered and leaking the old GCHandle.

This change checks existing.Target is not null instead of just key presence. A dead entry is now removed and its handle freed before the new object is registered, matching the behavior already used elsewhere (e.g. UnregisterNSObject(ptr, managed) and NativeObjectHasDied).

🤖 Pull request created by Copilot

[Copilot]

Pull request overview

This PR updates the .NET for Apple platforms runtime and toolchain to make native-handle → managed-wrapper registration more robust in alloc/init edge cases (notably pointer reuse and deferred registration), while also introducing related build/linker/runtime improvements (trusted platform assemblies generation, runtimeconfig merging, and UI-thread-check control via a feature switch), plus new regression tests.

Changes:

• Fixes deferred NSObject registration/handle transitions to avoid stale object_map entries and incorrect unregister behavior when native pointers are reused.
• Reworks UI-thread-check behavior: removes the old “remove-uithread-checks” optimizer path and replaces it with an MSBuild property + ILLink feature switch/substitution approach.
• Adds/updates build-time/runtime infrastructure (TPA list generation, runtimeconfig.dev merge task) and expands coverage with new tests and expected baselines.

Reviewed changes

Copilot reviewed 1 out of 1 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tools/linker/OptimizeGeneratedCode.cs	Removes EnsureUIThread optimizer.
tools/dotnet-linker/Steps/TrimmableRegistrarStep.cs	Emit lookup method conditionally.
tools/dotnet-linker/Steps/GenerateMainStep.cs	Populate TPA list for build.
tools/dotnet-linker/LinkerConfiguration.cs	Adds new linker config keys.
tools/dotnet-linker/DocumentionComments.cs	Adds name-only doc signature helper.
tools/dotnet-linker/AppBundleRewriter.cs	Avoid trimmer crash in DDA signatures.
tools/common/Target.cs	Emit TPA name array + escaping.
tools/common/StaticRegistrar.cs	Adds namespace validation call.
tools/common/Optimizations.cs	Deprecates remove-uithread-checks optimization path.
tools/common/ErrorHelper.tools.cs	Log warnings as warnings in MSBuild.
tools/common/Application.cs	Stores TPA generation state/list.
tools/api-tools/mono-api-html/MultiplexedFormatter.cs	Fix placeholder leakage in output.
tools/api-tools/mono-api-html-tests/mono-api-html-tests.csproj	New test project for mono-api-html.
tools/api-tools/mono-api-html-tests/ApiDiffTests.cs	Regression test for placeholder leakage.
tools/api-tools/api-tools.slnx	Adds slnx including new tests.
tests/xharness/Jenkins/TestVariationsFactory.cs	Fixes variations naming/selection.
tests/test-libraries/libtest.m	Adds native helpers for alloc/init scenarios.
tests/test-libraries/libtest.h	Exposes new native test helpers.
tests/msbuild/Xamarin.MacDev.Tasks.Tests/TaskTests/MergeRuntimeConfigFilesTaskTest.cs	Tests runtimeconfig merge task.
tests/monotouch-test/ObjCRuntime/InitCallbackProbeTest.cs	Probe tests for init-time behavior.
tests/monotouch-test/ObjCRuntime/AllocInitRaceTest.cs	Deterministic alloc/init reuse regression.
tests/linker/link all/PreserveTest.cs	Updates preserved signature expectation.
tests/dotnet/UnitTests/Extensions.cs	Updates filtered-warning strings.
tests/dotnet/UnitTests/expected/TVOS-NativeAOT-TrimmableStatic-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/TVOS-NativeAOT-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/TVOS-MonoVM-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/TVOS-MonoVM-preservedapis.txt	Updates expected preserved APIs.
tests/dotnet/UnitTests/expected/TVOS-MonoVM-interpreter-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/TVOS-MonoVM-interpreter-preservedapis.txt	Updates expected preserved APIs.
tests/dotnet/UnitTests/expected/MacOSX-NativeAOT-TrimmableStatic-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacOSX-NativeAOT-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacOSX-CoreCLR-Interpreter-TrimmableStatic-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacOSX-CoreCLR-Interpreter-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacCatalyst-NativeAOT-TrimmableStatic-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacCatalyst-NativeAOT-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacCatalyst-MonoVM-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacCatalyst-MonoVM-preservedapis.txt	Updates expected preserved APIs.
tests/dotnet/UnitTests/expected/MacCatalyst-MonoVM-interpreter-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/MacCatalyst-MonoVM-interpreter-preservedapis.txt	Updates expected preserved APIs.
tests/dotnet/UnitTests/expected/iOS-NativeAOT-TrimmableStatic-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/iOS-NativeAOT-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/iOS-MonoVM-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/iOS-MonoVM-preservedapis.txt	Updates expected preserved APIs.
tests/dotnet/UnitTests/expected/iOS-MonoVM-interpreter-size.txt	Updates expected app size.
tests/dotnet/UnitTests/expected/iOS-MonoVM-interpreter-preservedapis.txt	Updates expected preserved APIs.
tests/dotnet/UnitTests/EnsureUIThreadChecksTest.cs	New test for UI-thread-check switch.
tests/dotnet/EnsureUIThreadApp/tvOS/EnsureUIThreadApp.csproj	New app for UI-thread-check test.
tests/dotnet/EnsureUIThreadApp/shared.csproj	Shared test app settings.
tests/dotnet/EnsureUIThreadApp/macOS/EnsureUIThreadApp.csproj	New app for UI-thread-check test.
tests/dotnet/EnsureUIThreadApp/MacCatalyst/EnsureUIThreadApp.csproj	New app for UI-thread-check test.
tests/dotnet/EnsureUIThreadApp/iOS/EnsureUIThreadApp.csproj	New app for UI-thread-check test.
tests/dotnet/EnsureUIThreadApp/EnsureUIThreadApp.cs	References EnsureUIThread for linking.
tests/dotnet/EnsureUIThreadApp/Directory.Build.props	Imports test props.
tests/cecil-tests/Documentation.KnownFailures.txt	Updates known failures list.
tests/bindings-test/ApiDefinition.cs	Adds bindings for new test types.
tests/assembly-preparer/RelocateRegistrarTrampolinesTests.cs	Adds generic trampoline relocation coverage.
tests/assembly-preparer/PreserveSmartEnumConversionsTest.cs	Updates DDA signature expectation.
tests/assembly-preparer/PreserveBlockCodeHandlerTests.cs	Updates DDA signature expectation.
tests/assembly-preparer/OptimizeGeneratedCodeHandlerTests.cs	Removes/adjusts EnsureUIThread optimization tests.
tests/assembly-preparer/BaseClass.cs	Adds extra csproj injection parameter.
system-dependencies.sh	Adds retrying runtime download logic.
src/VideoToolbox/VTDefs.cs	Improves enum docs.
src/VideoSubscriberAccount/VSAccountProviderAuthenticationScheme.cs	Improves extension docs.
src/UIKit/UIApplication.cs	Moves UI-thread-check wiring to feature switch.
src/SceneKit/Defs.cs	Improves enum docs.
src/SafariServices/SSEnums.cs	Improves enum docs.
src/PdfKit/Enums.cs	Improves enum docs + adds missing member docs.
src/ObjCRuntime/TypeMaps.cs	Makes LookupUnmanagedFunction virtual default.
src/MapKit/MKEnums.cs	Fixes doc typo and removes noise.
src/ILLink.Substitutions.tvOS.xml	Adds feature switch + stubs EnsureUIThread.
src/ILLink.Substitutions.macOS.xml	Adds feature switch + stubs EnsureUIThread.
src/ILLink.Substitutions.MacCatalyst.xml	Adds feature switch + stubs EnsureUIThread.
src/ILLink.Substitutions.iOS.xml	Adds feature switch + stubs EnsureUIThread.
src/Foundation/NSObject2.cs	Deferred registration + ownership-aware unregister.
src/Foundation/Enum.cs	Improves enum/member docs.
src/EventKitUI/Defs.cs	Improves enum/member docs.
src/CoreVideo/CVEnums.cs	Improves enum/member docs.
src/CoreTelephony/CTEnums.cs	Adds enum member docs + new member doc.
src/CoreMotion/Defs.cs	Removes doc noise.
src/AVFoundation/Enums.cs	Improves enum/member docs.
src/AudioUnit/AUEnums.cs	Improves enum/member docs.
src/AppKit/NSApplication.cs	Moves UI-thread-check wiring to feature switch.
src/AppKit/Enums.cs	Improves enum/member docs.
scripts/changelog/README.md	Adds changelog tool README.
scripts/changelog/Program.cs	New changelog tool implementation.
scripts/changelog/fragment.mk	Adds script integration fragment.
scripts/changelog/changelog.csproj	Adds changelog tool project.
runtime/xamarin/main.h	Adds TPA/multi-RID runtime globals.
runtime/runtime.m	Uses build-time TPA list when present.
NuGet.config	Removes an old feed entry.
msbuild/Xamarin.Shared/Xamarin.Shared.targets	Includes .exe in assembly lists + inputs.
msbuild/Xamarin.MacDev.Tasks/Tasks/MergeRuntimeConfigFiles.cs	New task to merge runtimeconfig files.
msbuild/Xamarin.MacDev.Tasks/Tasks/DetectSdkLocation.cs	Updates deprecation warning text.
msbuild/Xamarin.Localization.MSBuild/MSBStrings.resx	Updates warnings + adds new errors.
macios/Localize/loc/zh-Hant/macios/tools/mtouch/Errors.resx.lcl	Localization change (generated file).
macios/Localize/loc/tr/macios/msbuild/Xamarin.Localization.MSBuild/MSBStrings.resx.lcl	Localization change (generated file).
macios/Localize/loc/ko/macios/msbuild/Xamarin.Localization.MSBuild/MSBStrings.resx.lcl	Localization change (generated file).
macios/Localize/loc/ja/macios/msbuild/Xamarin.Localization.MSBuild/MSBStrings.resx.lcl	Localization change (generated file).
eng/Version.Details.xml	Updates xharness dependency.
eng/Version.Details.props	Updates xharness dependency version.
dotnet/targets/Xamarin.Shared.Sdk.targets	New MSBuild properties/targets for features.
dotnet/targets/Xamarin.Shared.Sdk.props	Changes default registrar/prepare behavior.
docs/website/optimizations.md	Documents EnsureUIThread optimization change.
docs/building-apps/build-properties.md	Documents new MSBuild properties.
Directory.Build.props	Updates SystemSecurityCryptographyXml version.
.github/workflows/zizmor.yml	Updates zizmor action pin.
.github/workflows/maestro-changelog.yml	Switches to in-repo changelog tool.

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[vs-mobiletools-engineering-service2]

⚠️ AppSizeTest expected files changed ⚠️

The AppSizeTest detected changes in the expected app size files.

To update the expected files, add a comment with the following command:

/apply-gist https://gist.github.com/vs-mobiletools-engineering-service2/6cd516e5fa2bff7aa3d83c9acaac4cea

Updated files

• iOS-MonoVM-preservedapis.txt
• TVOS-MonoVM-preservedapis.txt
• TVOS-MonoVM-size.txt

Pipeline on Agent
Hash: 10c252b1adc4b145d2fb3844dc8d191df935cbf3 [PR build]

[rolfbjarne]

/apply-gist https://gist.github.com/vs-mobiletools-engineering-service2/6cd516e5fa2bff7aa3d83c9acaac4cea

[github-actions]

✅ Applied expected app size files from gist.

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: ed317df8ec42c842565cc37888ce94a027e35d21 [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build #ed317df] Test results 🚀

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✅ All tests passed on VSTS: test results.

🎉 All 264 tests passed 🎉

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