JNI Error with .NET 10 / Android 16

[db2222]

We are trying to upgrade from net9.0-android35.0 to net10.0-android36.1.

Now the app constantly crashes with JNI errors.

Via Logcat this is the logged error:

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116] JNI ERROR (app bug): local reference table overflow (max=512)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116] local reference table dump:

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]   Last 10 entries (of 512):

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       511: 0x12d79240 java.lang.String "X-Android-Sent-M... (21 chars)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       510: 0x70f0adb8 java.lang.String "X-Android-Sent-M... (21 chars)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       509: 0x70cfe030 java.lang.String "http/1.1"

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       508: 0x70f09a98 java.lang.String "X-Android-Select... (27 chars)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       507: 0x12c858a8 java.lang.String "NETWORK 200"

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       506: 0x12e66e98 java.lang.String "X-Android-Respon... (25 chars)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       505: 0x12e0ac40 java.lang.String "1763372369418"

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       504: 0x70f09a50 java.lang.String "X-Android-Receiv... (25 chars)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       503: 0x12d792c0 java.lang.String "Jetty(9.4.54.v20... (23 chars)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       502: 0x12cb9180 java.lang.String "Server"

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]   Summary:

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116]       512 of java.lang.String (436 unique instances)

11-17 10:39:29.446 10683 11588 F art     : art/runtime/indirect_reference_table.cc:116] 

I have unsuccessfully tried:

• Deactivated AndroidEnableMarshalMethods as I assumed it could have to do with this.
• Tried it with net10.0-android36.0.
• Checked for potential memory leaks.
• etc.

What I fundamentally don't understand why HTTP requests now cause this problem.

Isn't this part of the .NET code which implicitly deals with memory management?
This is how it used to be in the past.

Currently it is too much of a blackbox and unknown for me to narrow it down.

Is it a bug? Or do we have to re-program certain parts as the logic with .NET 10 or Android 16 changed?
But I wouldn't assume such a breaking change, or have I missed something?

Thank you for any help/hints!

[Eli018]

Hello!

Thank you for sharing the details. Based on the logs, the
art/runtime/indirect_reference_table.cc:116 error is usually related to an accumulation of JNI references inside the Android Runtime (ART). This often happens after internal changes in .NET for Android or in Android 16, especially when the app performs multiple HTTP requests.

The steps you already tried — disabling AndroidEnableMarshalMethods, switching to net10.0-android36.0, and checking for memory leaks — all make sense and suggest that the issue is not coming from your application code, but from recent changes in the platform itself.

This could indeed be:

a bug introduced in .NET 10 for Android, or

a side effect of the new memory-management behavior in Android 16 during HTTP operations.

To help narrow it down, here are a few questions:

1. Does the error occur with any HTTP endpoint, or only a specific one?

2. Have you tried switching the HttpClientHandler (e.g., using SocketsHttpHandler)?

3. Does it happen after several consecutive requests, or even on the first one?

4. Are you using System.Text.Json or another serializer?

If you can share a minimal reproducible example, I can help analyse it further.

Thank you!

[db2222]

It always happens during a specific request after several have been executed.
However, we have to create a database which has a specific order of data types from the server.
Therefore I strongly assume that it not has to do with that request, as the base logic is the same between the different data types.
My guess is that the amount of requests accumulate until that threshold of 512 is reached as the references aren't cleaned up.
But I will double check tomorrow when I'm back at work if that request/response maybe is larger than others.

Also I will try if a different HttpClientHandler changes the behaviour.

We are using Json.NET for our own code.

It is a bit difficult for to me to post a simple example.
The app of my company is complex and closed-source.
I hope I will come around to it the next days to maybe create a dummy project.
Currently I have lots of different tasks all at once so I'm a bit low on time 😅

Is there anything else I can quickly check to help narrow it down?
Maybe some specific debug/log settings?

Thank you.

[jonathanpeppers]

I would build a small sample that makes web requests in the same way as your real application w/ Newtonsoft.Json, etc.

Then share here, thanks!

[db2222]

Finally I have found time to continue to investigate.

The problem occurs only on Android 7 devices. I have checked with a real device and an emulator.

Android 8 and Android 16 on the other hand are ok.

These are legacy devices that some customers still might have.

My question is if Microsoft still offers support for API level 24? Meaning SupportedOSPlatformVersion.

According to https://learn.microsoft.com/en-us/dotnet/maui/whats-new/dotnet-10?view=net-maui-10.0#recommended-minimum-supported-android-api this seems to be the case.

[db2222]

I have tried it with SocketsHttpHandler instead of HttpClientHandler and then no JNI errors occur!

Are there critical things to consider when doing this switch?

[jonpryor]

Offhand, one of the following is likely happening::

1. There's a bug in dotnet/android and JNIEnv::DeleteLocalRef() isn't called when it should be. LREF logs would be helpful; see also: https://github.com/dotnet/android/blob/main/Documentation/guides/internals/debug-jni-objrefs.md
2. there's a bug in Android 7 in which JNIEnv::DeleteLocalRef() doesn't work properly.

(2) feels very unlikely, but would explain why it happens on Android 7 devices but not others.

LREF logs would help in investigating this.

[db2222]

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Does this log help narrow it down?
At least a pattern is noticeable.

I can't post the whole log as I would need to clarify if my company does allow it.

[db2222]

The issue seems to be that the dispose creates another local reference. That can't be wanted, or do I totally misunderstand something?

[db2222]

@jonpryor @jonathanpeppers
Is the given log helpful?

There seems to be a bug that dispose creates new references (see stacktrace with CopyHeaders/ToEnumerator_Dispose/ConstructPeer).

Just as a heads up. I might not be able to answer for the next couple of days.