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Using Native AOT with Android Bionic

Starting with .NET 8 Preview 7, it's possible to build shared libraries and command line executables for Android.

Not a full Android experience is available - it's only possible to publish for two Bionic RID: linux-bionic-arm64 and linux-bionic-x64. Publishing for Android RIDs (android-arm64/android-x64) is not possible. This limited experience corresponds to building with Android NDK from Native code - the limitations are similar. Interop with Java needs to be done manually through JNI, if necessary.

The minimum API level is 21 at the time of writing the document, but search for AndroidApiLevelMin in this repo for more up-to-date information.

To build for Bionic:

  • Ensure you have Android NDK for your system downloaded and extracted somewhere. We build and test with NDK r23c but anything newer should also work. Double check with the NDK version referenced here, which might be more up-to-date than this document.
  • Update your PATH to include {NDK_ROOT}\toolchains\llvm\prebuilt\{OS_ARCH}\bin. Replace {NDK_ROOT} with the path where you extracted the NDK, and replace {OS_ARCH} with your host OS and architecture (e.g. windows-x86_64 or linux-x86_64). Make sure this entry is first in your path - we need to make sure that running clang will execute clang from this directory.
  • You can either create a new project or use an existing project. For this guide, let's create a new one: 
    $ dotnet new console -o HelloBionic --aot
$ cd HelloBionic
    Note: the --aot parameter added <PublishAot>true</PublishAot> to the new project.
  • Publish the project: 
    $ dotnet publish -r linux-bionic-arm64 -p:DisableUnsupportedError=true -p:PublishAotUsingRuntimePack=true
  • You should have a binary under bin\Release\net10.0\linux-bionic-arm64\publish. Copy it to an Android device. Either adb push or using some GUI.
  • You can probably run it with adb shell, but I used Termux: open Termux, give it access to file system by running termux-setup-storage. This will give you access to phone storage under ~/storage. Copy the binary from ~/storage/... to ~ (internal storage is not executable and you won't be able to run stuff from it). Then chmod +x HelloBionic and ./HelloBionic. You should see Hello World.

Command line apps are not very interesting for Android. The more interesting scenario are shared libraries that can be called into from Java/Kotlin through JNI. This is very similar to building shared libraries in other languages like C/C++/Rust. PublishAot allows building shared libraries that are callable from non-.NET languages. See https://learn.microsoft.com/dotnet/core/deploying/native-aot/interop#native-exports.

For an example of a Native AOT shared library invoked through JNI from Java see https://github.com/josephmoresena/NativeAOT-AndroidHelloJniLib.

Known issues

If you hit error : version script assignment of 'V1.0' to symbol '_init' failed: symbol not defined - this is a known issue with .NET 8 release dotnet#92272, you can add following lines to your csproj to work around:

<ItemGroup Condition="$(RuntimeIdentifier.StartsWith('linux-bionic'))">
  <LinkerArg Include="-Wl,--undefined-version" />
</ItemGroup>

Libssl dependency

Crypto in .NET is implemented on top of OS-provided crypto libraries (we do not build or service crypto algorithm implementations). Since Android doesn't come with the standard openssl library inbox, your app will need to provide it. The runtime code can handle various versions of the openssl library. The library has to be placed next to the app.