Hi Evgueni,
I wrote a simple launcher [1] that does the following:
1) Calls CreateJavaVM
2) Runs the main method of your Test class below
3) Calls DestroyJavaVM
Note that it does *not* call env->ExceptionDescribe() before destroying
the VM.
I tested this launcher against the RI and J9 and found that no stack
trace or
error details are printed.
So I would say that it is standard behaviour for the VM not to output any
information about uncaught exceptions when shutting down, and that the
launcher
is expected to call ExceptionDescribe() if it wants any details to be
printed.
So from what you have said below, IMHO we need to:
- Change DRLVM to not print stack trace if there is an uncaught
exception at
shutdown.
- If necessary, change the launcher to make sure ExceptionDescribe() is
called
before DestroyJavaVM().
Does that sound right?
Regards,
Oliver
[1]
#include <jni.h>
main() {
JNIEnv *env;
JavaVM *jvm;
jint result;
jclass cls;
jmethodID mid;
JavaVMInitArgs vmargs;
vmargs.version = 0x00010002;
vmargs.nOptions = 0;
vmargs.ignoreUnrecognized = JNI_TRUE;
result=JNI_CreateJavaVM(&jvm, (void**)&env, &vmargs);
if (result<0) {
fprintf(stderr, "Cannot create JavaVM\n");
exit(1);
}
cls = (*env)->FindClass(env, "TestClass");
if(cls == NULL)
{
printf("ERROR: FindClass failed.\n");
goto destroy;
}
mid = (*env)->GetStaticMethodID(env, cls, "main",
"([Ljava/lang/String;)V");
if(mid==NULL)
{
printf("ERROR: GetStaticMethodID call failed.\n");
goto destroy;
}
(*env)->CallStaticVoidMethod(env, cls, mid, NULL);
destroy:
(*jvm)->DestroyJavaVM(jvm);
}
Evgueni Brevnov wrote:
Hi All,
I'm almost done with the implementation of Invocation API for DRLVM.
While testing it I ran into a problem when an exception is printed
twice. I created a simple application which just throws an error and
it is not handled by any exception handler:
public class Test {
public static void main(String [] args) {
throw new Error("my");
}
}
In this case the launcher calls env->ExceptionDescribe() before
destroying VM. Then it calls DestroyJavaVM() which identifies
unhanded exception and calls an uncaught exception handler (see
java.lang.Thread.getUncaughtExceptionHandler()) for the current
thread. By default the handler prints the exception one more time.
That's definitely differs from RI where the exception is printed out
only once.
To identify where the problem is I created another simple test and
runs it on RI and DRLVM:
public class Test {
static class MyHandler implements Thread.UncaughtExceptionHandler {
public void uncaughtException(Thread t, Throwable e) {
System.out.println("My Handler Called!!!");
}
}
public static void main(String [] args) {
Thread.currentThread().setUncaughtExceptionHandler(new
MyHandler());
throw new Error("my");
}
}
Here is the output:
RI: java.exe Test
My Handler Called!!!
DRLVM: java.exe Test
java/lang/Error : my
at Test.main (Test.java: 12)
My Handler Called!!!
As you can see RI doesn't print exception stack trace at all. But
DRLVM does. To be precise the launcher does. So we need to fix the
launcher.....
Note: The behaviour of DRLVM you have may differ from listed above
since all experiments were done on my local workspace with Invocation
API implemented.
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Oliver Deakin
IBM United Kingdom Limited
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