From 97c141418f13cec9758ed5847898b98ca70384be Mon Sep 17 00:00:00 2001
From: Sven Boemer <sbomer@gmail.com>
Date: Fri, 17 Apr 2026 10:27:19 -0700
Subject: [PATCH 1/4] [NativeAOT] Take over native linker invocation from ILC
 targets

Set NativeLib=static so ILC produces a .a archive via ar instead of invoking
the linker directly. Add _AndroidLinkNativeAotSharedLibrary target that runs
after LinkNative and links the ILC .o output into a .so using the NDK clang
wrapper. This gives Android full control over the native linker invocation,
following the same approach used by macios.

Reproduce the flags that LinkNative and SetupOSSpecificProps would have
provided for NativeLib=Shared:
- -shared, -Wl,-e,0x0, -Wl,-z,max-page-size=16384 (from LinkerArg)
- --version-script, --export-dynamic, --discard-all, --gc-sections (from
  CustomLinkerArg inside LinkNative)
- -fuse-ld=lld (from LinkerArg via LinkerFlavor)
- sections.ld linker script to retain the __modules section

Set IlcExportUnmanagedEntrypoints=true so ILC exports [UnmanagedCallersOnly]
methods as native symbols, required for JNI entry points.

Clear LinkerFlavor inside _AndroidBeforeIlcCompile to work around an ILC
targets bug where _LinkerVersion detection is skipped for NativeLib=Static
but the numeric comparison in LinkNative still evaluates.
Context: https://github.com/dotnet/runtime/issues/126978

The resulting linker command line is identical to the original.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../Microsoft.Android.Sdk.NativeAOT.targets   | 59 ++++++++++++++++++-
 1 file changed, 57 insertions(+), 2 deletions(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
index ddf8348d9e9..72c62edf700 100644
--- a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
+++ b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
@@ -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 -->
@@ -111,6 +117,12 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
       <!-- 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>
       <!--
@@ -133,7 +145,7 @@ 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" />
 
@@ -258,6 +270,49 @@ 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">
+    <PropertyGroup>
+      <_AndroidNativeAotSharedLibrary>$(NativeOutputPath)$(NativeBinaryPrefix)$(TargetName).so</_AndroidNativeAotSharedLibrary>
+    </PropertyGroup>
+    <ItemGroup>
+      <_AndroidNativeAotLinkerArgs Include="&quot;$(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;$(NativeIntermediateOutputPath)sections.ld&quot;" />
+      <_AndroidNativeAotLinkerArgs Include="@(LinkerArg)" />
+    </ItemGroup>
+
+    <!-- Linker script to retain the __modules section (required by NativeAOT runtime) -->
+    <WriteLinesToFile File="$(NativeIntermediateOutputPath)sections.ld" Lines="OVERWRITE_SECTIONS { __modules : { KEEP(*(__modules)) } }" Overwrite="true" />
+
+    <MakeDir Directories="$([System.IO.Path]::GetDirectoryName($(_AndroidNativeAotSharedLibrary)))" />
+    <Exec Command="&quot;$(CppLinker)&quot; @(_AndroidNativeAotLinkerArgs, ' ')" />
+
+    <ItemGroup>
+      <!-- Replace the .a that NativeCompile/ComputeLinkedFilesToPublish would publish with our .so -->
+      <ResolvedFileToPublish Remove="@(ResolvedFileToPublish)" Condition=" '%(Filename)%(Extension)' == '$(TargetName).a' " />
+      <ResolvedFileToPublish Include="$(_AndroidNativeAotSharedLibrary)">
+        <RelativePath>$(NativeBinaryPrefix)$(TargetName).so</RelativePath>
+        <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
+      </ResolvedFileToPublish>
+    </ItemGroup>
+  </Target>
+
   <!--
     dotnet/runtime#125629 moved the NativeAOT entry point from ComputeLinkedFilesToPublish
     (AfterTargets="ComputeResolvedFilesToPublishList") to NativeCompile (an SDK Publish hook).
@@ -272,7 +327,7 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
   <Target Name="_AndroidFixNativeLibraryFileName" AfterTargets="ComputeFilesToPublish">
     <ItemGroup>
       <!-- Fix paths to contain lib-prefix -->
-      <ResolvedFileToPublish Update="@(ResolvedFileToPublish)" ArchiveFileName="lib%(FileName)%(Extension)" Condition=" '%(Filename)%(Extension)' == '$(TargetName)$(NativeBinaryExt)' " />
+      <ResolvedFileToPublish Update="@(ResolvedFileToPublish)" ArchiveFileName="lib%(FileName)%(Extension)" Condition=" '%(Filename)%(Extension)' == '$(TargetName).so' " />
     </ItemGroup>
   </Target>
 

From ec129aa6b5a20e67b3e0b1be39aa047054c57389 Mon Sep 17 00:00:00 2001
From: Sven Boemer <sbomer@gmail.com>
Date: Fri, 17 Apr 2026 11:15:44 -0700
Subject: [PATCH 2/4] Add Inputs/Outputs and FileWrites for incremental build
 support

Add Inputs/Outputs to _AndroidLinkNativeAotSharedLibrary so incremental
builds can skip relinking when inputs haven't changed. Add FileWrites
for the .so and sections.ld so Clean can account for generated files.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../targets/Microsoft.Android.Sdk.NativeAOT.targets         | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
index 72c62edf700..b5baf486522 100644
--- a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
+++ b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
@@ -276,7 +276,9 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
     This target runs after LinkNative and produces the shared library that Android needs.
   -->
   <Target Name="_AndroidLinkNativeAotSharedLibrary"
-      AfterTargets="LinkNative">
+      AfterTargets="LinkNative"
+      Inputs="$(NativeObject);@(NativeLibrary)"
+      Outputs="$(NativeOutputPath)$(NativeBinaryPrefix)$(TargetName).so">
     <PropertyGroup>
       <_AndroidNativeAotSharedLibrary>$(NativeOutputPath)$(NativeBinaryPrefix)$(TargetName).so</_AndroidNativeAotSharedLibrary>
     </PropertyGroup>
@@ -310,6 +312,8 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
         <RelativePath>$(NativeBinaryPrefix)$(TargetName).so</RelativePath>
         <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
       </ResolvedFileToPublish>
+      <FileWrites Include="$(_AndroidNativeAotSharedLibrary)" />
+      <FileWrites Include="$(NativeIntermediateOutputPath)sections.ld" />
     </ItemGroup>
   </Target>
 

From 2ff10fb2a7ce47bf163db58187d0fd4454790994 Mon Sep 17 00:00:00 2001
From: Sven Boemer <sbomer@gmail.com>
Date: Wed, 22 Apr 2026 14:58:17 -0700
Subject: [PATCH 3/4] Use response file for linker args on Windows
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

On Windows, ILC's LinkNative writes linker args to a response file instead
of passing them inline — cmd.exe has quoting issues with spaces in paths.
Match that behavior in _AndroidLinkNativeAotSharedLibrary.

Fixes NativeAOT build failures for projects with spaces or special characters
in their names (e.g. CheckProjectWithSpaceInNameWorks tests).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../targets/Microsoft.Android.Sdk.NativeAOT.targets    | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
index 591704295f9..bd60e38889a 100644
--- a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
+++ b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
@@ -303,7 +303,14 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
     <WriteLinesToFile File="$(NativeIntermediateOutputPath)sections.ld" Lines="OVERWRITE_SECTIONS { __modules : { KEEP(*(__modules)) } }" Overwrite="true" />
 
     <MakeDir Directories="$([System.IO.Path]::GetDirectoryName($(_AndroidNativeAotSharedLibrary)))" />
-    <Exec Command="&quot;$(CppLinker)&quot; @(_AndroidNativeAotLinkerArgs, ' ')" />
+    <!-- On Windows, write args to a response file to avoid cmd.exe quoting issues with spaces in paths.
+         This matches what ILC's LinkNative does. -->
+    <Exec Command="&quot;$(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 -->
@@ -314,6 +321,7 @@ This file contains the NativeAOT-specific MSBuild logic for .NET for Android.
       </ResolvedFileToPublish>
       <FileWrites Include="$(_AndroidNativeAotSharedLibrary)" />
       <FileWrites Include="$(NativeIntermediateOutputPath)sections.ld" />
+      <FileWrites Include="$(NativeIntermediateOutputPath)android-link.rsp" Condition=" $([MSBuild]::IsOSPlatform('windows')) " />
     </ItemGroup>
   </Target>
 

From fd6b78ecb2e232f68ce1b8cf7e6f3433d41cdbf9 Mon Sep 17 00:00:00 2001
From: Sven Boemer <sbomer@gmail.com>
Date: Fri, 24 Apr 2026 06:08:49 +0800
Subject: [PATCH 4/4] Set CppLibCreator to llvm-ar for NativeAOT static library
 builds

ILC's LinkNative target defaults CppLibCreator to the host 'ar', which
does not understand ELF objects when cross-compiling for Android. On
macOS this caused Xcode's ranlib to emit spurious 'empty table of
contents' warnings for every ABI.

Set CppLibCreator to llvm-ar (from the NDK toolchain, already on PATH)
so the archiver can correctly process ELF .o files.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../targets/Microsoft.Android.Sdk.NativeAOT.targets            | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
index bd60e38889a..8de77b2c654 100644
--- a/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
+++ b/src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeAOT.targets
@@ -113,6 +113,9 @@ 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>