webassembly在GraalVM中从Java调用wasm代码时如何使用回调

Question

在https://www.graalvm.org/reference-manual/wasm/#embedding-webassembly-programs之后 我尝试使用回调返回到Java代码中

编译成example.wasm的锈迹代码：

#[no_mangle]
pub extern fn greet(print: extern fn(u8)) {
    print(42)
}

使用GraalVM polyglot API嵌入WASM的Java代码：

byte[] binary = readBytes("example.wasm");
Context.Builder contextBuilder = Context.newBuilder("wasm");
Source.Builder sourceBuilder = Source.newBuilder("wasm", ByteSequence.create(binary), "example");
Source source = sourceBuilder.build();
Context context = contextBuilder.build();

context.eval(source);

Consumer<Value> print = (Value val) -> System.out.println("Callback called: " + val);
Value greetFunction = context.getBindings("wasm").getMember("main").getMember("greet");
greetFunction.execute(print);

但是，运行此程序时，我会遇到以下异常：

Exception in thread "main" java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:108)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:58)
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88)
Caused by: org.graalvm.polyglot.PolyglotException: java.lang.ClassCastException: class com.oracle.truffle.polyglot.HostObject cannot be cast to class java.lang.Integer (com.oracle.truffle.polyglot.HostObject is in module org.graalvm.truffle of loader 'app'; java.lang.Integer is in module java.base of loader 'bootstrap')
    at org.graalvm.wasm.nodes.WasmRootNode.moveArgumentsToLocals(WasmRootNode.java:173)
    at org.graalvm.wasm.nodes.WasmRootNode.executeWithContext(WasmRootNode.java:122)
    at org.graalvm.wasm.nodes.WasmRootNode.execute(WasmRootNode.java:103)
    at <wasm>.greet(Unknown)
    at org.graalvm.sdk/org.graalvm.polyglot.Value.execute(Value.java:834)
    at org.example.wasmhost.WasmHostApplication.main(WasmHostApplication.java:57)
    ... 8 more

我的java是：

$ java -version
openjdk version "11.0.11" 2021-04-20
OpenJDK Runtime Environment GraalVM CE 21.1.0 (build 11.0.11+8-jvmci-21.1-b05)
OpenJDK 64-Bit Server VM GraalVM CE 21.1.0 (build 11.0.11+8-jvmci-21.1-b05, mixed mode, sharing)