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[NativeAOT] Take over native linker invocation from ILC targets #11148

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[NativeAOT] Take over native linker invocation from ILC targets #11148

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97c1414
[NativeAOT] Take over native linker invocation from ILC targets
sbomer Apr 17, 2026
ec129aa
Add Inputs/Outputs and FileWrites for incremental build support
sbomer Apr 17, 2026
db6be18
Merge branch 'main' into dev/sbomer/nativeaot-linker-takeover
sbomer Apr 18, 2026
c496936
Merge branch 'main' into dev/sbomer/nativeaot-linker-takeover
sbomer Apr 21, 2026
2ff10fb
Use response file for linker args on Windows
sbomer Apr 22, 2026
fd6b78e
Set CppLibCreator to llvm-ar for NativeAOT static library builds
sbomer Apr 23, 2026
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74 changes: 72 additions & 2 deletions ...Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,12 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
<!-- ResolvedFileToPublish is not populated until _AndroidComputeIlcCompileInputs, so
proguard generation must run after that target instead of after ILLink. -->
<_GenerateProguardAfterTargets>_AndroidComputeIlcCompileInputs</_GenerateProguardAfterTargets>
<!-- Ask ILC to produce a static library (.a) instead of a shared library (.so).
This gives Android full control over the native linker invocation. -->
<NativeLib>static</NativeLib>
<!-- ILC only sets this for NativeLib=Shared, but we need [UnmanagedCallersOnly] methods
exported as native symbols so JNI can find them via dlsym. -->
<IlcExportUnmanagedEntrypoints>true</IlcExportUnmanagedEntrypoints>
</PropertyGroup>

<!-- Default property values for NativeAOT Debug configuration -->
Expand Down Expand Up @@ -107,10 +113,19 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
<CppCompilerAndLinker>$(_NdkAbi)-linux-android$(_NDKApiLevel)-clang$(_NdkWrapperScriptExt)</CppCompilerAndLinker>
<CppLinker>$(_NdkAbi)-linux-android$(_NDKApiLevel)-clang$(_NdkWrapperScriptExt)</CppLinker>
<ObjCopyName>llvm-objcopy</ObjCopyName>
<!-- Use the NDK's llvm-ar instead of the host 'ar' so that ELF objects are handled
correctly when cross-compiling. -->
<CppLibCreator>llvm-ar</CppLibCreator>

<!-- We must ensure this is `false`, as it would interfere with statically linking libc++ -->
<LinkStandardCPlusPlusLibrary>false</LinkStandardCPlusPlusLibrary>

<!-- Clear LinkerFlavor: the ILC targets set it to 'lld' for android/bionic, but with NativeLib=static
the _LinkerVersion detection is skipped, causing a numeric comparison error in LinkNative.
Since we handle native linking ourselves, LinkerFlavor is not needed.
Context: https://github.com/dotnet/runtime/issues/126978 -->
<LinkerFlavor />

<!-- Example settings from: https://github.com/xamarin/xamarin-macios/blob/c43d4ea40bc777969e3b158cf46446df292d8449/dotnet/targets/Xamarin.Shared.Sdk.targets#L541-L550 -->
<RunILLink>true</RunILLink>
<!--
Expand All @@ -133,7 +148,7 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
</PropertyGroup>
<ItemGroup>
<!-- Android needs a proper soname property or it will refuse to load the library -->
<LinkerArg Include="&quot;-Wl,-soname,lib$(TargetName)$(NativeBinaryExt)&quot;" />
<LinkerArg Include="&quot;-Wl,-soname,lib$(TargetName).so&quot;" />
<LinkerArg Include="-Wl,--error-unresolved-symbols" />
<LinkerArg Include="-Wl,--no-undefined" />

Expand Down Expand Up @@ -258,6 +273,61 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
DependsOnTargets="_GenerateNativeAotAndroidAppAssemblerSources">
</Target>

<!--
With NativeLib=static, ILC's LinkNative target produces a .a archive via `ar`.
We need to link the ILC .o output + all LinkerArg items into a .so ourselves.
This target runs after LinkNative and produces the shared library that Android needs.
-->
<Target Name="_AndroidLinkNativeAotSharedLibrary"
AfterTargets="LinkNative"
Inputs="$(NativeObject);@(NativeLibrary)"
Outputs="$(NativeOutputPath)$(NativeBinaryPrefix)$(TargetName).so">
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@jonathanpeppers jonathanpeppers Apr 17, 2026

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Do managed assemblies also need to be Inputs? Someone could add their own [UnmanagedCallersOnly] and it wouldn't get picked up in an incremental build.

Honestly, this is NativeAOT (Release-mode only), maybe we could just let this always run if LinkNative ran?

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@sbomer sbomer Apr 17, 2026

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I think if someone adds [UCO] it would cause ILC to re-run, produce a new $(NativeObject) and that would make this target run.

These are the same inputs/outputs as the LinkNative target so it should already be running if LinkNative ran. If we remove the Inputs/Outputs, it would always run even if LinkNative was skipped.

<PropertyGroup>
<_AndroidNativeAotSharedLibrary>$(NativeOutputPath)$(NativeBinaryPrefix)$(TargetName).so</_AndroidNativeAotSharedLibrary>
</PropertyGroup>
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<ItemGroup>
<_AndroidNativeAotLinkerArgs Include="&quot;$(NativeObject)&quot;" />
<_AndroidNativeAotLinkerArgs Include="-shared" />
<_AndroidNativeAotLinkerArgs Include="-fuse-ld=lld" />
<_AndroidNativeAotLinkerArgs Include="-o &quot;$(_AndroidNativeAotSharedLibrary)&quot;" />
<!-- These flags are in the ILC targets' LinkNative/LinkerArg but conditioned on NativeLib=Shared
or LinkerFlavor=lld, so they're missing when NativeLib=static. Add them back. -->
<_AndroidNativeAotLinkerArgs Include="-Wl,-e,0x0" />
<_AndroidNativeAotLinkerArgs Include="-Wl,-z,max-page-size=16384" />
<_AndroidNativeAotLinkerArgs Include="-Wl,--version-script=&quot;$(ExportsFile)&quot;" Condition="'$(ExportsFile)' != ''" />
<_AndroidNativeAotLinkerArgs Include="-Wl,--export-dynamic" Condition="'$(ExportsFile)' != ''" />
<_AndroidNativeAotLinkerArgs Include="-Wl,--discard-all" />
<_AndroidNativeAotLinkerArgs Include="-Wl,--gc-sections" />
<_AndroidNativeAotLinkerArgs Include="-Wl,-T,&quot;$(NativeIntermediateOutputPath)sections.ld&quot;" />
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<_AndroidNativeAotLinkerArgs Include="@(LinkerArg)" />
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</ItemGroup>

<!-- Linker script to retain the __modules section (required by NativeAOT runtime) -->
<WriteLinesToFile File="$(NativeIntermediateOutputPath)sections.ld" Lines="OVERWRITE_SECTIONS { __modules : { KEEP(*(__modules)) } }" Overwrite="true" />

<MakeDir Directories="$([System.IO.Path]::GetDirectoryName($(_AndroidNativeAotSharedLibrary)))" />
<!-- On Windows, write args to a response file to avoid cmd.exe quoting issues with spaces in paths.
This matches what ILC's LinkNative does. -->
<Exec Command="&quot;$(CppLinker)&quot; @(_AndroidNativeAotLinkerArgs, ' ')"
Condition=" !$([MSBuild]::IsOSPlatform('windows')) " />
<WriteLinesToFile File="$(NativeIntermediateOutputPath)android-link.rsp" Lines="@(_AndroidNativeAotLinkerArgs)" Overwrite="true" Encoding="utf-8"
Condition=" $([MSBuild]::IsOSPlatform('windows')) " />
<Exec Command="&quot;$(CppLinker)&quot; @&quot;$(NativeIntermediateOutputPath)android-link.rsp&quot;"
Condition=" $([MSBuild]::IsOSPlatform('windows')) " />

<ItemGroup>
<!-- Replace the .a that NativeCompile/ComputeLinkedFilesToPublish would publish with our .so -->
<ResolvedFileToPublish Remove="@(ResolvedFileToPublish)" Condition=" '%(Filename)%(Extension)' == '$(TargetName).a' " />
<ResolvedFileToPublish Include="$(_AndroidNativeAotSharedLibrary)">
<RelativePath>$(NativeBinaryPrefix)$(TargetName).so</RelativePath>
<CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
</ResolvedFileToPublish>
<FileWrites Include="$(_AndroidNativeAotSharedLibrary)" />
<FileWrites Include="$(NativeIntermediateOutputPath)sections.ld" />
<FileWrites Include="$(NativeIntermediateOutputPath)android-link.rsp" Condition=" $([MSBuild]::IsOSPlatform('windows')) " />
</ItemGroup>
</Target>

<!--
dotnet/runtime#125629 moved the NativeAOT entry point from ComputeLinkedFilesToPublish
(AfterTargets="ComputeResolvedFilesToPublishList") to NativeCompile (an SDK Publish hook).
Expand All @@ -272,7 +342,7 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
<Target Name="_AndroidFixNativeLibraryFileName" AfterTargets="ComputeFilesToPublish">
<ItemGroup>
<!-- Fix paths to contain lib-prefix -->
<ResolvedFileToPublish Update="@(ResolvedFileToPublish)" ArchiveFileName="lib%(FileName)%(Extension)" Condition=" '%(Filename)%(Extension)' == '$(TargetName)$(NativeBinaryExt)' " />
<ResolvedFileToPublish Update="@(ResolvedFileToPublish)" ArchiveFileName="lib%(FileName)%(Extension)" Condition=" '%(Filename)%(Extension)' == '$(TargetName).so' " />
</ItemGroup>
</Target>

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