On 9/22/06, Oliver Deakin <[EMAIL PROTECTED]> wrote:
> Tim Ellison wrote:
> > Still, it seems strange that you should have to call
DetachCurrentThread
> > explicitly to get this behavior. I would have expected that
> > DestroyJavaVM alone would cause the uncaught exception handler to
fire.
> > Not all apps that embed the VM will know to make this work-around.
> >
>
> Yes, that surprised me too. The bug suggests that the launcher is at
> fault for calling
> ExceptionDescribe() instead of DetachCurrentThread(). However I
would have
> thought that this was not necessary in the case where an exception
> handler has
> been registered, and that the handler would be called during
> DestroyJavaVM()'s
> execution.
>
> Perhaps this is something that could be "fixed" in DRLVM? So if
> DetachCurrentThread() is called, it runs any registered exception
> handlers for that
> thread as usual. However, if DestroyJavaVM is called, it makes sure
that all
> exception handlers are run for every thread.
>
Sure, I checked both cases work fine on my implementation of
InvocationAPI for DRLVM (with DetachCurrentThread and without it). So
the launcher can choose either to detach the main thread or not...
Thanks
Evgueni
> Regards,
> Oliver
>
> > Regards,
> > Tim
> >
> > Oliver Deakin wrote:
> >
> >> Evgueni Brevnov wrote:
> >>
> >>> Oliver,
> >>>
> >>> Yes, I got the same result on RI when starting VM by your simple
> >>> launcher. Assume it is OK not to print an error message and stacke
> >>> trace of an unhandled exception in JavaDestroyVM(). How about
calling
> >>> uncaught exception handler? According to the spec it must be
called if
> >>> terminating thread has an exception. The test shows that the
handler
> >>> is not called when VM is created by our launcher. But if VM is
> >>> created by RI's launcher then everything works fine and the
handler is
> >>> executed. This means that RI's launcher somehow deals with it
(not VM
> >>> itself). It seems for me as a bug in RI. Do you think so?
> >>>
> >> Hi Evgueni,
> >>
> >> I see the same thing - if I run your second Test class (the
> >> UncaughtExceptionHandler
> >> test) with my simple launcher on the RI and J9 I do not see any
output.
> >> i.e. the MyHandler.uncaughtException() method is never called.
> >>
> >> Having a Google around I found a link to a Sun bug registered
for this [1].
> >> All our launcher needs to do is call DetachCurrentThread() on
the main
> >> thread before DestroyJavaVM(), and the UncaughtExceptionHandler
will
> >> be called as expected. (This bug only occurs with exception
handlers
> >> registered to the main thread - I verified this with [2] which
has its
> >> non-main
> >> thread's exception handler called correctly)
> >>
> >> So if you add the line:
> >> (*jvm)->DetachCurrentThread(jvm);
> >> to my simple launcher just before the DestroyJavaVM() call, you
will see
> >> that the MyHandler.uncaughtException() is called for the main
thread, and
> >> the test works as expected.
> >>
> >> This looks like it needs to be added to our launcher - do you
agree?
> >>
> >> What is even more interesting is that if I run your more simple
Test class
> >> (the one that just does 'throw new Error("my");'), with the
> >> DetachCurrentThread()
> >> call added to the simple launcher I get a stack trace printed on
both RI
> >> and J9!
> >> Again it appears that this is only a problem with the main
thread (if
> >> you alter
> >> [2] before so that the handler is not registered, you get the
expected
> >> stack trace).
> >> So it seems that adding DetachCurrentThread to the launcher
fixes both
> >> problems!
> >>
> >> Regards,
> >> Oliver
> >>
> >> [1] http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4992454
> >> [2]
> >> public class Test {
> >> static class MyHandler implements
Thread.UncaughtExceptionHandler {
> >> public void uncaughtException(Thread t, Throwable e) {
> >> System.out.println("My Handler Called!!!");
> >> }
> >> }
> >>
> >> static class MyRunnable implements Runnable {
> >> public void run() {
> >> Thread.currentThread().setUncaughtExceptionHandler(new
> >> MyHandler());
> >> throw new Error("my");
> >> }
> >> }
> >>
> >> public static void main(String [] args) {
> >> Thread t = new Thread(new MyRunnable());
> >> t.start();
> >> try {
> >> t.join();
> >> } catch (InterruptedException e) {
> >> System.out.println("Interrupted!");
> >> }
> >> }
> >> }
> >>
> >>
> >>> Evgueni
> >>>
> >>> On 9/21/06, Oliver Deakin <[EMAIL PROTECTED]> wrote:
> >>>
> >>>> 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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> >>>>
> >>>>
> >>>>
> >>>
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> >>>
> >>>
> >>>
> >
> >
>
> --
> Oliver Deakin
> IBM United Kingdom Limited
>
>
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