DllNotFoundException from Android emulator when calling into a native dll

[AArnott]

Android application type

.NET Android (net7.0-android, net8.0-android, etc.)

Affected platform version

VS 2022 Update 9, net8.0-android

Description

When my new Avalonia Android project consumes a native library, at runtime it throws DllNotFoundException.
These native libraries come by way of NuGet. I've tried Nerdbank.Zcash and libgit2sharp. Both of these carry a runtimes folder. The Nerdbank.Zcash package in particular carries a runtimes/android-x64/native/libnerdbank_zcash_rust.so file.
I can see that the file is included in the apk. But the android emulator still fails.

More details and diagnostic efforts are described in AArnott/Avalonia-WithNativeDependency#1

Steps to Reproduce

A minimal repro is available here: https://github.com/AArnott/Avalonia-WithNativeDependency
Be sure to switch the solution platform to x64, since in AnyCPU, no native binary is included in the deployed app.

In effect:

1. Create a new Avalonia Android app. Bump its target framework from net7.0-android to net8.0-android.
2. Add a PackageReference to Nerdbank.Zcash
3. Add code that exercises the native library, for example these two lines.

Run the app in the android emulator. (I haven't tried a real android device).

Did you find any workaround?

Nothing yet.

Relevant log output

No response

[AArnott]

I just tested this on a physical android device. It works fine. Yay.
So... why is the emulator broken?

More trivia: the emulator is running x86_64, and that's the ABI of the binary selected for inclusion in the app as well.

[maxkatz6]

Would be useful to know what's a typical approach diagnosing DllNotFoundException issues on Android. Supposedly it can happen when ABI is wrong or there is other problem with .so file.

[grendello]

@AArnott I don't think Avalonia use much of our infrastructure, so this issue might probably be better filed in Avalonia, but can you provide the APK/AAB archives you get? I'd like to examine what's in them as produced on your machine.

[dellis1972]

Looking at the Nuget package for Nerdbank.Zcash 0.2.68-beta it does not contain any andorid runtimes. only linux-x64?

[dellis1972]

see https://nuget.info/packages/Nerdbank.Zcash/0.2.68-beta

[akoeplinger]

@dellis1972 you need to get the latest version from the nuget feed: https://github.com/AArnott/Avalonia-WithNativeDependency/blob/master/nuget.config#L7

[dellis1972]

ok. My guess then is its trying to use an x64 binary on an x86 or arm image on the emulator (as it works on a device).

[grendello]

@AArnott also, a detailed exception message and stack trace would be necessary to see what might be going on. Try these commands to get the logcat output (including our runtime logging, not sure if it works with Avalonia):

$ adb shell setprop debug.mono.log default,assembly,timing=bare,mono_log_level=debug,mono_log_mask=all
$ adb logcat -G 64M
$ adb logcat -c
# Start the app here, wait for it to crash, then wait 15s and
$ adb logcat -d > log.txt

Attach the resulting log.txt to this issue please.

[jonpryor]

Running the sample in an emulator, two issues stand out:

@AArnott: First, the emulator doesn't like libnerdbank_zcash_rust.so:

I monodroid-assembly: Failed to load shared library '/data/app/com.CompanyName.AvaloniaTest-D9SFv_VrlfJEnJE_eJbnFQ==/lib/x86_64/libnerdbank_zcash_rust.so'. dlopen
 failed: cannot locate symbol "__extenddftf2" referenced by "/data/app/com.CompanyName.AvaloniaTest-D9SFv_VrlfJEnJE_eJbnFQ==/lib/x86_64/libnerdbank_zcash_rust.so"...

i.e. "something is wrong" with libnerdbank_zcash_rust.so. Some cursory searches find:

• NDK version compatibility mozilla/rust-android-gradle#105
• [bug] cargo tauri android dev -> cannot locate symbol __extenddftf2 tauri-apps/tauri#7413
• flutter run fails on x86_64 emulator breez/c-breez#553 (comment)

@grendello: The other issue is that commit 1aa0ea7 appears to have a bug, as my adb logcat contains:

I DOTNET  : JavaProxyThrowable: translation threw an exception: Java.Lang.NullPointerException: Declaring class is null
I DOTNET  :    at Java.Interop.JniEnvironment.InstanceMethods.CallNonvirtualVoidMethod(JniObjectReference instance, JniObjectReference type, JniMethodInfo method, JniArgumentValue* args)
I DOTNET  :    at Java.Interop.JniPeerMembers.JniInstanceMethods.FinishCreateInstance(String constructorSignature, IJavaPeerable self, JniArgumentValue* parameter s)
I DOTNET  :    at Java.Lang.StackTraceElement..ctor(String declaringClass, String methodName, String fileName, Int32 lineNumber)
I DOTNET  :    at Android.Runtime.JavaProxyThrowable.TranslateStackTrace()
I DOTNET  :    at Android.Runtime.JavaProxyThrowable.Create(Exception innerException)
I DOTNET  :   --- End of managed Java.Lang.NullPointerException stack trace ---
I DOTNET  : java.lang.NullPointerException: Declaring class is null
I DOTNET  :      at java.util.Objects.requireNonNull(Objects.java:228)
I DOTNET  :      at java.lang.StackTraceElement.<init>(StackTraceElement.java:71)
I DOTNET  :      at crc6431345fe65afe8d98.AvaloniaMainActivity_1.n_onCreate(Native Method)

Looks like this line (and others?) cannot be null:

https://github.com/xamarin/xamarin-android/blob/e41a31b9520dd1a4dbfe8162cf49fed7052dc69f/src/Mono.Android/Android.Runtime/JavaProxyThrowable.cs#L74