Default/Static interface method desugar remapping not working in .NET 7 #7663
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Area: Bindings
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radimitrov
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Area: App Runtime
grendello
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Area: Bindings
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Simplified test case |
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Default and static methods are not supported by Android before API Level 24: We thought we had worked around it for .NET 7, but there seems to be a bug preventing it from working like we expected. We will continue to investigate that. The workaround is to target API-24+ by setting this in your project file: <SupportedOSPlatformVersion>24</SupportedOSPlatformVersion> |
jpobst
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On the investigation front, consider var val = IStaticMethodsInterface.Value;which results in a crash: However, if I manually do what the binding should be doing -- I still need to verify + review that the binding is doing this -- then it works: static void TryInvokeStaticInterfaceMethod()
{
Console.WriteLine ("# jonp: trying to get class `com/xamarin/android/StaticMethodsInterface$-CC`…");
var t = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface$-CC");
Console.WriteLine ($"# jonp: t={t}");
Console.WriteLine ("# jonp: trying to get static method `getValue()I`…");
var m = t.GetStaticMethod ("getValue", "()I");
Console.WriteLine ($"# jonp: m={m}");
Console.WriteLine ("# jonp: Invoking static method `getValue()I`…");
var r = Java.Interop.JniEnvironment.StaticMethods.CallStaticIntMethod (t.PeerReference, m);
Console.WriteLine ($"# jonp: r={r}");
}Invoking TODO: figure out why the current binding infrastructure isn't doing what the above manual binding does. |
The answer is because we don't pass the
What we do is more like: var from = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface");
var to = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface$-CC");
var m = to.GetStaticMethod ("getValue", "()I");
// Note: needs to use `to.PeerReference`, *not* `from.PeerReference`
var r = Java.Interop.JniEnvironment.StaticMethods.CallStaticIntMethod (from.PeerReference, m); |
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On the investigation front, consider var foo = new MyDefaultClass ();
var val2 = (foo as IDefaultMethodsInterface).Bar;which results in a crash: This is also due to desugaring, which is enabled when When desugaring is enabled, things fail because nothing is where we expect it; if you use and look for the
Rephrased, when attempting to non-virtually invoke DefaultMethodsInterface instance = …
int b = instance.getBar();when Desugaring is present, we need to instead invoke a DefaultMethodsInterface instance = …
int b = DefaultMethodsInterface$-CC.getBar(instance);This actually feels reminiscent of the " |
jonpryor
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Jan 20, 2023
Context: xamarin/xamarin-android#7663 (comment) TODO: what's going on?
jonpryor
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Jan 20, 2023
Context: xamarin/xamarin-android#7663 (comment) TODO: what's going on?
jonpryor
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Context: xamarin/xamarin-android#7663 (comment) TODO: what's going on?
jonpryor
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Jan 25, 2023
Context: 1f27ab5 Context: xamarin/xamarin-android@f6f11a5 Context: xamarin/xamarin-android#7663 (comment) Commit 1f27ab5 added partial support for [desugaring][0], which rewrites Java bytecode so that [default interface methods][1] and [static methods in interfaces][2] can be supported on pre-Android 7.0 (API-24) devices, as the pre-API-24 ART runtime does not directly support those bytecode constructs. The hope was that commit 1f27ab5 in concert with xamarin/xamarin-android@f6f11a5a would allow static methods on interfaces to work, by having `Java.Interop.JniPeerMembers.JniStaticMethods.GetMethodInfo()` call `JniRuntime.JniTypeManager.GetStaticMethodFallbackTypes()`. xamarin/xamarin-android would then override `GetStaticMethodFallbackTypes()`, allowing `GetMethodInfo()` to instead resolve the static method from the fallback type, allowing the static method invocation to work. > TODO: Update xamarin-android to override > `GetStaticMethodFallbackTypes()`, to return > `$"{jniSimpleReference}$-CC"`. What *actually* happened? Not enough testing happened, such that when it was *actually* attempted, it blew up bigly: JNI DETECTED ERROR IN APPLICATION: can't call static int com.xamarin.android.StaticMethodsInterface$-CC.getValue() with class java.lang.Class<com.xamarin.android.StaticMethodsInterface> in call to CallStaticIntMethodA from void crc641149b9fe658fbe8e.MainActivity.n_onCreate(android.os.Bundle) Oops. What went wrong? The problem is that [`JNIEnv::CallStatic*Method()`][3] requires that we provide the `jclass clazz` value for the type that declares the static method, but we're providing the wrong class! Specifically, consider this Java interface: public interface StaticMethodsInterface { static int getValue() { return 3; } } In a desugared environment, this is transformed into the *pair* of types: public interface StaticMethodsInterface { } public class StaticMethodsInterface$-CC { public static int getValue() { return 3; } } `GetStaticMethodFallbackTypes("StaticMethodsInterface")` returns `StaticMethodsInterface$-CC`, allowing `GetMethodInfo()` to lookup `StaticMethodsInterface$-CC` and resolve the method `getValue.()I`. However, when `JniPeerMembers.JniStaticMethods.Invoke*Method()` is later invoked, the `jclass` value for `StaticMethodsInterface` is provided, *not* the value for `StaticMethodsInterface$-CC`. It's as if we do: var from = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface"); var to = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface$-CC"); var m = to.GetStaticMethod ("getValue", "()I"); var r = Java.Interop.JniEnvironment.StaticMethods.CallStaticIntMethod (from.PeerReference, m); The problem is that we need to use `to.PeerReference`, *not* `from.PeerReference`! Fix `GetMethodInfo()` so that when a method is resolved from a fallback type, the type instance is stored in the `JniMethodInfo.StaticRedirect` field, and then update the `Invoke*Method()` methods so that `JniMethodInfo.StaticRedirect` is passed to `JNIEnv::CallStatic*Method()` if it is set, before defaulting to `JniPeerMembers.JniPeerType`. "Optimization opportunity": the approach taken does not attempt to cache the `JniType` instances which correspond to the fallback types. Consequently, it is possible that multiple GREFs could be consumed for the `JniMethodInfo.StaticRedirect` instances, as each instance will be unique. This was done for expediency, and because @jonpryor doesn't know if this will be an actual problem in practice. Unrelatedly, fix the `JniPeerMembers (string, Type, bool)` constructor so that it participates in type remapping. Without this change, interface types cannot be renamed by the 1f27ab5 infrastructure. [0]: https://developer.android.com/studio/write/java8-support#library-desugaring [1]: https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html [2]: https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html#static [3]: https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/functions.html#CallStatic_type_Method_routines
jonpryor
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Feb 16, 2023
Context: 1f27ab5 Context: xamarin/xamarin-android@f6f11a5 Context: xamarin/xamarin-android#7663 (comment) Commit 1f27ab5 added partial support for [desugaring][0], which rewrites Java bytecode so that [default interface methods][1] and [static methods in interfaces][2] can be supported on pre-Android 7.0 (API-24) devices, as the pre-API-24 ART runtime does not directly support those bytecode constructs. The hope was that commit 1f27ab5 in concert with xamarin/xamarin-android@f6f11a5a would allow static methods on interfaces to work, by having `Java.Interop.JniPeerMembers.JniStaticMethods.GetMethodInfo()` call `JniRuntime.JniTypeManager.GetStaticMethodFallbackTypes()`. xamarin/xamarin-android would then override `GetStaticMethodFallbackTypes()`, allowing `GetMethodInfo()` to instead resolve the static method from the fallback type, allowing the static method invocation to work. > TODO: Update xamarin-android to override > `GetStaticMethodFallbackTypes()`, to return > `$"{jniSimpleReference}$-CC"`. What *actually* happened? Not enough testing happened, such that when it was *actually* attempted, it blew up bigly: JNI DETECTED ERROR IN APPLICATION: can't call static int com.xamarin.android.StaticMethodsInterface$-CC.getValue() with class java.lang.Class<com.xamarin.android.StaticMethodsInterface> in call to CallStaticIntMethodA from void crc641149b9fe658fbe8e.MainActivity.n_onCreate(android.os.Bundle) Oops. What went wrong? The problem is that [`JNIEnv::CallStatic*Method()`][3] requires that we provide the `jclass clazz` value for the type that declares the static method, but we're providing the wrong class! Specifically, consider this Java interface: public interface StaticMethodsInterface { static int getValue() { return 3; } } In a desugared environment, this is transformed into the *pair* of types: public interface StaticMethodsInterface { } public class StaticMethodsInterface$-CC { public static int getValue() { return 3; } } `GetStaticMethodFallbackTypes("StaticMethodsInterface")` returns `StaticMethodsInterface$-CC`, allowing `GetMethodInfo()` to lookup `StaticMethodsInterface$-CC` and resolve the method `getValue.()I`. However, when `JniPeerMembers.JniStaticMethods.Invoke*Method()` is later invoked, the `jclass` value for `StaticMethodsInterface` is provided, *not* the value for `StaticMethodsInterface$-CC`. It's as if we do: var from = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface"); var to = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface$-CC"); var m = to.GetStaticMethod ("getValue", "()I"); var r = Java.Interop.JniEnvironment.StaticMethods.CallStaticIntMethod (from.PeerReference, m); The problem is that we need to use `to.PeerReference`, *not* `from.PeerReference`! Fix `GetMethodInfo()` so that when a method is resolved from a fallback type, the type instance is stored in the `JniMethodInfo.StaticRedirect` field, and then update the `Invoke*Method()` methods so that `JniMethodInfo.StaticRedirect` is passed to `JNIEnv::CallStatic*Method()` if it is set, before defaulting to `JniPeerMembers.JniPeerType`. "Optimization opportunity": the approach taken does not attempt to cache the `JniType` instances which correspond to the fallback types. Consequently, it is possible that multiple GREFs could be consumed for the `JniMethodInfo.StaticRedirect` instances, as each instance will be unique. This was done for expediency, and because @jonpryor doesn't know if this will be an actual problem in practice. Unrelatedly, fix the `JniPeerMembers (string, Type, bool)` constructor so that it participates in type remapping. Without this change, interface types cannot be renamed by the 1f27ab5 infrastructure. [0]: https://developer.android.com/studio/write/java8-support#library-desugaring [1]: https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html [2]: https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html#static [3]: https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/functions.html#CallStatic_type_Method_routines
jonpryor
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Feb 22, 2023
Context: 1f27ab5 Context: xamarin/xamarin-android@f6f11a5 Context: xamarin/xamarin-android#7663 (comment) Commit 1f27ab5 added partial support for [desugaring][0], which rewrites Java bytecode so that [default interface methods][1] and [static methods in interfaces][2] can be supported on pre-Android 7.0 (API-24) devices, as the pre-API-24 ART runtime does not directly support those bytecode constructs. The hope was that commit 1f27ab5 in concert with xamarin/xamarin-android@f6f11a5a would allow static methods on interfaces to work, by having `Java.Interop.JniPeerMembers.JniStaticMethods.GetMethodInfo()` call `JniRuntime.JniTypeManager.GetStaticMethodFallbackTypes()`. xamarin/xamarin-android would then override `GetStaticMethodFallbackTypes()`, allowing `GetMethodInfo()` to instead resolve the static method from the fallback type, allowing the static method invocation to work. > TODO: Update xamarin-android to override > `GetStaticMethodFallbackTypes()`, to return > `$"{jniSimpleReference}$-CC"`. What *actually* happened? Not enough testing happened, such that when it was *actually* attempted, it blew up bigly: JNI DETECTED ERROR IN APPLICATION: can't call static int com.xamarin.android.StaticMethodsInterface$-CC.getValue() with class java.lang.Class<com.xamarin.android.StaticMethodsInterface> in call to CallStaticIntMethodA from void crc641149b9fe658fbe8e.MainActivity.n_onCreate(android.os.Bundle) Oops. What went wrong? The problem is that [`JNIEnv::CallStatic*Method()`][3] requires that we provide the `jclass clazz` value for the type that declares the static method, but we're providing the wrong class! Specifically, consider this Java interface: public interface StaticMethodsInterface { static int getValue() { return 3; } } In a desugared environment, this is transformed into the *pair* of types: public interface StaticMethodsInterface { } public class StaticMethodsInterface$-CC { public static int getValue() { return 3; } } `GetStaticMethodFallbackTypes("StaticMethodsInterface")` returns `StaticMethodsInterface$-CC`, allowing `GetMethodInfo()` to lookup `StaticMethodsInterface$-CC` and resolve the method `getValue.()I`. However, when `JniPeerMembers.JniStaticMethods.Invoke*Method()` is later invoked, the `jclass` value for `StaticMethodsInterface` is provided, *not* the value for `StaticMethodsInterface$-CC`. It's as if we do: var from = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface"); var to = new Java.Interop.JniType ("com/xamarin/android/StaticMethodsInterface$-CC"); var m = to.GetStaticMethod ("getValue", "()I"); var r = Java.Interop.JniEnvironment.StaticMethods.CallStaticIntMethod (from.PeerReference, m); The problem is that we need to use `to.PeerReference`, *not* `from.PeerReference`! Fix `GetMethodInfo()` so that when a method is resolved from a fallback type, the type instance is stored in the `JniMethodInfo.StaticRedirect` field, and then update the `Invoke*Method()` methods so that `JniMethodInfo.StaticRedirect` is passed to `JNIEnv::CallStatic*Method()` if it is set, before defaulting to `JniPeerMembers.JniPeerType`. "Optimization opportunity": the approach taken does not attempt to cache the `JniType` instances which correspond to the fallback types. Consequently, it is possible that multiple GREFs could be consumed for the `JniMethodInfo.StaticRedirect` instances, as each instance will be unique. This was done for expediency, and because @jonpryor doesn't know if this will be an actual problem in practice. Unrelatedly, fix the `JniPeerMembers(string, Type, bool)` constructor so that it participates in type remapping. Without this change, interface types cannot be renamed by the 1f27ab5 infrastructure. [0]: https://developer.android.com/studio/write/java8-support#library-desugaring [1]: https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html [2]: https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html#static [3]: https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/functions.html#CallStatic_type_Method_routines
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We believe desugar remapping is now fully supported in |
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Android application type
Android for .NET (net6.0-android, etc.)
Affected platform version
VS 2022, net7.0-android
Description
App crashes at runtime for debug build with a JNI error related to default/static Java interface method binding. Doesn't matter if the debugger is attached. Might be related to #7125 but reverting to the old binding behaviour with
<AndroidBoundInterfacesContainStaticAndDefaultInterfaceMethods>false</AndroidBoundInterfacesContainStaticAndDefaultInterfaceMethods>didn't help. Same fortruevalue.Steps to Reproduce
Bind any Java library with a default static interface method.
Did you find any workaround?
Release build
Relevant log output
The text was updated successfully, but these errors were encountered: