JVMTI ExceptionCatch event clarification

[Chris]

Hi,

I hope this is the correct mailing list, if not, please guide me to the 
one I should use.

If I understand the JVMTI ExceptionCatch event correctly, an event 
should be generated if a native method catches an exception. The docs say:

"If the exception is caught in a native method, the event is generated 
as soon as control is returned to a Java programming language method."

I am not able to see this behavior, if a JNI method catches a Java 
exception using the "ExceptionClear" JNI function (or is there another 
way to catch an exception in native code?). My test scenario is as follows:

Java method *main* calls the native method *native0*, which calls the 
Java method *throwing*. *throwing* throws an exception, and *native0* 
clears the exception (by calling "ExceptionClear") before returning. 
According to the documentation, a JVMTI event should be generated, after 
  *native0* returned, but this is not the case. The exception catch 
event is never generated. Please see the reproducing example at the end 
of this mail.

My assumption is, that the example produces an output like:

MAIN
THROW!
CATCH!
THROW!
CATCH!

But the actual output, with an OpenJDK 8, and OpenJDK 11 HotSpot JVM, is:

MAIN
THROW!
THROW!
CATCH!

Java versions (download from adoptopenjdk.net):

openjdk version "1.8.0_212"
OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_212-b03)
OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.212-b03, mixed mode)

openjdk version "11.0.3" 2019-04-16
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.3+7)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.3+7, mixed mode)

running on Arch Linux:

$ uname -srvmo
Linux 5.0.13-arch1-1-ARCH #1 SMP PREEMPT Sun May 5 18:05:41 UTC 2019 
x86_64 GNU/Linux

Could you please elaborate if my assumption about the behavior is correct?
If not, is there a way to get a callback if the "ExceptionClear" 
function catches an Exception in native code (beside using the JNI 
Function Interception feature)?
If my assumption is correct and this is an actual bug, could you please 
point me to the correct place to submit a bug report?

Thanks, Christoph

========================================================================
// Test.java
class Test {
     public static void main(String... args) throws Exception {
         System.out.println("MAIN");
         try {
             native0(true);
         } catch (UnsupportedOperationException t) {}
         try {
             native0(false);
         } catch (UnsupportedOperationException t) {}
     }

     public static void throwing() {
         throw new UnsupportedOperationException();
     }

     public static native void native0(boolean doCatch);
}
========================================================================

========================================================================
// test.cpp
#include <cstdio>
#include <jvmti.h>

void JNICALL
on_exception(jvmtiEnv*, JNIEnv*, jthread, jmethodID, jlocation, jobject,
              jmethodID, jlocation) {
     printf("THROW!\n");
}

void JNICALL
on_exception_catch(jvmtiEnv*, JNIEnv*, jthread, jmethodID, jlocation,
                    jobject) {
     printf("CATCH!\n");
}

JNIEXPORT jint JNICALL
Agent_OnLoad(JavaVM* jvm, char* options, void* reserved) {
     jvmtiEnv* jvmti;
     jvm->GetEnv((void**) &jvmti, JVMTI_VERSION);

     jvmtiCapabilities requiredCaps = {};
     requiredCaps.can_generate_exception_events = 1;
     jvmti->AddCapabilities(&requiredCaps);

     jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                                     JVMTI_EVENT_EXCEPTION, NULL);
     jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                                     JVMTI_EVENT_EXCEPTION_CATCH, NULL);

     jvmtiEventCallbacks eventCallbacks = {};
     eventCallbacks.Exception = on_exception;
     eventCallbacks.ExceptionCatch = on_exception_catch;
     jvmti->SetEventCallbacks(&eventCallbacks, sizeof(eventCallbacks));

     return 0;
}

extern "C" JNIEXPORT void JNICALL
Java_Test_native0(JNIEnv* jni, jclass klass, jboolean do_catch) {
     jmethodID throwingMethod;
     throwingMethod = jni->GetStaticMethodID(klass,"throwing","()V");
     jni->CallStaticVoidMethod(klass, throwingMethod);
     if (jni->ExceptionCheck() == JNI_TRUE && do_catch == JNI_TRUE)
         jni->ExceptionClear();
}
========================================================================