.NET 9 Project won't start on Android with 16kb page size enabled

[phillippschmedt]

Description

When creating a fresh .NET 9 MAUI project and trying to deploy it on an android 15 device with 16kb page size enabled the app won't start. Problem happens on emulator and real device.

Steps to Reproduce

1. Create an android 16kb emulator as described here: https://developer.android.com/guide/practices/page-sizes#16kb-emulator
2. Create a new .NET 9 MAUI project
3. Try to start on the emulator

Link to public reproduction project repository

https://github.com/phillippschmedt/Android16KBProblems

Version with bug

9.0.40 SR4

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

No response

Affected platforms

Android

Affected platform versions

Android 15 16Kb enabled emulator or real device with 16kb enabled (pixel 8a, pixel 8)

Did you find any workaround?

No

Relevant log output

[borrrden]

I'm curious about this as well. Is there some way to signal using 16k page aligned libraries? I find the following in my APK to be unaligned (all of the AOT ones are aligned, but these are prebuilt before the app by Microsoft, I believe) when compiling for .NET 8 via .NET 9.0.200

• libSystem.Security.Cryptography.Native.Android.so
• libmonodroid.so
• libmono-component-marshal-ilgen.so
• libmonosgen-2.0.so
• libSystem.IO.Compression.Native.so
• libSystem.Native.so

I do indeed so that at least Microsoft.NETCore.App.Runtime.Mono.android-arm64/8.0.13/runtimes/android-arm64/native/libmonosgen-2.0.so is not properly aligned but 9.0.2 is so that might be a clue. Does this require actually TARGETING .NET 9 (net9.0-android) or is it enough to build with the .NET 9 tooling?

[amirvenus]

Are you sure this is a Maui bug?

Would you be able to reproduce with a plain .net for Android app (NOT Maui)?

[phillippschmedt]

@amirvenus I am only using .NET MAUI. I can't talk about anything else, sorry.

[borrrden]

I would bet this is not MAUI specific.

[devluminix]

We are also facing this issue in a .NET 9 MAUI project. What timeline can we expect for a fix? Android best practice says:

Starting November 1st, 2025, all new apps and updates to existing apps submitted to Google Play and targeting Android 15+ devices must support 16 KB page sizes.

[jonathanpeppers]

For those on .NET 8, upgrade to .NET 9, as .NET 8 is out of support on mobile:

• https://aka.ms/maui-support-policy

@devluminix what .so file are you getting the warning for? The messages above either say .NET 8, or don't list the warning message.

There should be a build warning for any non-16kb aligned .so files.

[devluminix]

@jonathanpeppers dug a little deeper and actually do not notice any issues with the .so files packages in the com.companyname.mauiapp1-Signed.apk (by following Google/Android command line procedure described).

However there is still a crash when trying to start a vanilla .NET MAUI App. Here is the repro procedure which triggers the crash:

• Start Visual Studio 2022 community 17.14.3 > From the launcher menu, choose Create a new project > Choose .NET MAUI App template > Configure a location on disk > Pick .NET 9.0 (Standard Term Support) and optionally check Include sample content
• Within the created project, change nothing
• Stick with Debug|AnyCPU configuration, but choose an Android API 35 emulator enabled for 16KB pages
• Either run debugger attached or not
• Watch the Android logcat and you will see something like:

06-02 12:25:32.059 14557 14557 D nativeloader: Load /data/app/~~WU8rxcUnCdOtgxHv3iLHQQ==/com.companyname.mauiapp1-uRt5TZeyzMf_HiFHfDZ3Xw==/lib/arm64/libmonodroid.so using ns clns-7 from class loader (caller=/data/app/~~WU8rxcUnCdOtgxHv3iLHQQ==/com.companyname.mauiapp1-uRt5TZeyzMf_HiFHfDZ3Xw==/base.apk!classes2.dex): ok 06-02 12:25:32.060 14557 14557 W monodroid: Failed to create directory '/data/user/0/com.companyname.mauiapp1/files/.override/arm64-v8a'. File exists 06-02 12:25:32.060 14557 14557 W monodroid: Creating public update directory: /data/user/0/com.companyname.mauiapp1/files/.__override__/arm64-v8a 06-02 12:25:32.060 14557 14557 W nyname.mauiapp1: Attempt to remove non-JNI local reference 06-02 12:25:32.060 14557 14557 W monodroid: runtime args empty
06-02 12:25:32.060 14557 14557 F monodroid: No assemblies found in '/data/user/0/com.companyname.mauiapp1/files/.override/arm64-v8a' or ''. Assuming this is part of Fast Deployment. Exiting...
06-02 12:25:32.060 14557 14557 F monodroid: ALL entries in APK named lib/arm64-v8a/ MUST be STORED. Gradle's minification may COMPRESS such entries. 06-02 12:25:32.060 14557 14557 F monodroid: Abort at monodroid-glue.cc:740:3 ('MonoDomain *xamarin::android::internal::MonodroidRuntime::create_domain(JNIEnv *, jstring_array_wrapper &, bool, bool)')
--------- beginning of crash 06-02 12:25:32.061 14557 14557 F libc : Fatal signal 6 (SIGABRT), code -1 (SI_QUEUE) in tid 14557 (nyname.mauiapp1), pid 14557 (nyname.mauiapp1)

Interestingly, if I uncheck Use fast deployment in project properties and then uninstall/clean/rebuild/redeploy, it all works, and I see the .NET MAUI sample app running just fine.

So possibly there is something wrong in Debug with Fast deployment with .NET MAUI for Android 35.