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Thanks for the feedback. Would it be possible for you to share a compiler dump file, which contains the inputs to the R8 compilation? This includes the app's Java class files, keep rules etc., and makes it possible to reproduce the given build.

You can generate such a file by running:

./gradlew assembleRelease --no-daemon -Dcom.android.tools.r8.dumpinputtodirectory=/path/to/dumps

You can share this artifact privately with christofferqa@google.com and sgjesse@google.com.

I just sent you an e-mail with the requested file.

Thank you for the provided sample project. Looking at the input, input has this constructor for com.example.DemoModelB:

  public com.example.DemoModelB(int, int, kotlinx.serialization.internal.SerializationConstructorMarker);
    descriptor: (IILkotlinx/serialization/internal/SerializationConstructorMarker;)V
    flags: (0x1001) ACC_PUBLIC, ACC_SYNTHETIC
    Code:
      stack=3, locals=4, args_size=4
         0: iconst_1
         1: iconst_1
         2: iload_1
         3: iand
         4: if_icmpeq     18
         7: iload_1
         8: iconst_1
         9: getstatic     #79                 // Field com/example/DemoSerializerB.INSTANCE:Lcom/example/DemoSerializerB;
        12: invokevirtual #83                 // Method com/example/DemoSerializerB.getDescriptor:()Lkotlinx/serialization/descriptors/SerialDescriptor;
        15: invokestatic  #89                 // Method kotlinx/serialization/internal/PluginExceptionsKt.throwMissingFieldException:(IILkotlinx/serialization/descriptors/SerialDescriptor;)V
        18: aload_0
        19: iload_1
        20: aload_3
        21: invokespecial #92                 // Method com/example/DemoModelBase."<init>":(ILkotlinx/serialization/internal/SerializationConstructorMarker;)V
        24: aload_0
        25: iload_2
        26: putfield      #13                 // Field id:I
        29: return

The original reference to com/example/DemoSerializerB.INSTANCE is here af pc 9. However the class com.example.DemoSerializerB has no field INSTANCE and no method getDescriptor() (it only has a constructor). Looking at the code it looks as if com.example.DemoModelB$$serializer has the field INSTANCE and method getDescriptor().

To trigger the branch with the access to INSTANCE you can do:

println(demo.test("{}", DemoModelType.B))

Which in debug mode will throw:

java.lang.NoSuchFieldError: No static field INSTANCE of type Lcom/example/DemoSerializerB; in class Lcom/example/DemoSerializerB; or its superclasses

So the code never gets to the throwMissingFieldException which I think is intended.

When R8 see references to missing items it tries to leave it alone to give the same runtime exception. In this case the exception is changed from java.lang.NoSuchFieldError to

java.lang.NoClassDefFoundError: Failed resolution of: LT0/DemoSerializerB;

Changing the runtime exception here is not optimal, but it seems like the Kotlin serialization code has some issues to trigger this.

Opened https://github.com/Kotlin/kotlinx-datetime/issues/514.

Info on reproduction received by email:

To make reproduction easier, I created a demo application here: https://github.com/dmarth/r8-issue-demo Right now there are three commits:

• 764cc890c156bb4ff85cba8237138dc63d77f6c1 The first commit just creates an "Empty Activity" project with the default configuration of Android Studio (2024.3.1 Patch 1).
• 1591e94b84b9a6a110f67604ad287d190eb78345 Then, the code demonstrating the issue is added. So this is probably the most interesting part.
• 6ce2c8285f993d0b222761929b02554f6880f41a This one just adds a dummy signing configuration so the application can actually be installed on a device or in an emulator.

Investigating the DEX file from the resulting APK I get the result described in the issue:

$ ~/Android/Sdk/build-tools/35.0.0/dexdump -d classes.dex | grep -F
DemoSerializer
0694ce: 6204 2504                              |000b: sget-object v4,
LT0/DemoSerializerB;.INSTANCE:LT0/DemoSerializerB; // field@0425

I still need to go through the details, but I am confused by the issue you opened in kotlinx-datetime. Should this be an issue in the kotlinx-serialization repository?

Sorry about using the wrong GitHub project and thank you for pointing it out. (I had kotlinx-datetime open in a tab looking at some other issue, and didn't look close enough). Opened https://github.com/Kotlin/kotlinx.serialization/issues/2974 instead.

The issue is now fixed in kotlinx-serialization, see https://github.com/JetBrains/kotlin/commit/e4d002778f694d42d0cc141e105f28271658032f.

Thanks for investigating this issue and taking care of getting it fixed in kotlinx-serialization.

To my understanding it is not the NoSuchFieldError or its replacement that is thrown in my case. Instead, the exception is raised by the runtime verifier right before the method is invoked.

Quote from my initial message:

However, I get a VerifyError because of the invalid class reference when loading the corresponding DEX file dynamically at runtime. Is there any difference in the verification of DEX files between those that are part of the APK and those that are loaded dynamically?

Do you have any explanation for this behavior? To me it would be understandable if the verifier would reject this (dead) code, but why is this not always the case?