Re: [Qt-jambi-interest] Exceptions and crash after update to Qt Jambi 4.5.x
Gregor Mückl wrote: which are tedious to find and debug. So I do not think that this workaround would be actually feasible as a short or medium term solution, even if we figure out a way to make it work. Hi, Gregor. The following patch should hopefully solve your problem: http://qt.gitorious.org/qt-jambi/qt-jambi/commit/41f7c11ddb75e4a98092fc8bd0f03a41a043edc6 You may get away with just the .java-patch for the crash, but if you want to get rid of the messages to the console as well, you have to patch the native code as well, and thus build the Qt Jambi native libraries from source. -- Eskil ___ Qt-jambi-interest mailing list Qt-jambi-interest@trolltech.com http://lists.trolltech.com/mailman/listinfo/qt-jambi-interest
Re: [Qt-jambi-interest] Exceptions and crash after update to Qt Jambi 4.5.x
Gregor Mückl wrote:
Caused by: java.lang.ClassNotFoundException:
eu.moonlight3d.ml3d.ui.mainwindow.view.Viewport$ProjectionType
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 16 more
After that I get a VM crash. I find it strange that the NoClassDefFoundError
is
thrown, although the class is definitely there and must have been loaded. It
must be noted, however, that the class in question is loaded through a
classloader that is created at runtime, after Qt Jambi has been loaded and
initialised through the default system classloader.
A further indication that this would be the case is that everything works
fine
when I start the program from Eclipse, where the contents of the plugins is
(improperly) added to the system classpath at VM startup.
So, could it be that the Jambi internals fail to query the correct class
definition because they are looking for it in the wrong classloader? If so,
is
there a workaround for this? I need my own classloader to be able to load
plugins.
The method in your stack trace is attempting to build a meta object for
your class so that its functions and properties can be accessed from C++
applications (e.g. in Qt Jambi Designer.) It will look in the class path
for any class used in the signature of one of the methods. It should of
course not crash if the classes cannot be resolved, this is a bug. I
have made a task to fix this for the next patch release of Qt Jambi.
Meanwhile, could you try annotating the methods that cause trouble with
the QtBlockedSlot annotation, like this:
@QtBlockedSlot
void fooBar(ClassNotOnClassPath cnocp) {
}
I don't know if this is an acceptable work-around to you, but it might
avoid the function call which causes the exception, so it might be worth
a try until the bug has been fixed.
-- Eskil
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Re: [Qt-jambi-interest] Exceptions and crash after update to Qt Jambi 4.5.x
On Monday 24 August 2009, Eskil Abrahamsen Blomfeldt wrote:
Gregor Mückl wrote:
Caused by: java.lang.ClassNotFoundException:
eu.moonlight3d.ml3d.ui.mainwindow.view.Viewport$ProjectionType
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 16 more
After that I get a VM crash. I find it strange that the
NoClassDefFoundError is thrown, although the class is definitely there
and must have been loaded. It must be noted, however, that the class in
question is loaded through a classloader that is created at runtime,
after Qt Jambi has been loaded and initialised through the default system
classloader.
A further indication that this would be the case is that everything works
fine when I start the program from Eclipse, where the contents of the
plugins is (improperly) added to the system classpath at VM startup.
So, could it be that the Jambi internals fail to query the correct class
definition because they are looking for it in the wrong classloader? If
so, is there a workaround for this? I need my own classloader to be able
to load plugins.
The method in your stack trace is attempting to build a meta object for
your class so that its functions and properties can be accessed from C++
applications (e.g. in Qt Jambi Designer.) It will look in the class path
for any class used in the signature of one of the methods. It should of
course not crash if the classes cannot be resolved, this is a bug. I
have made a task to fix this for the next patch release of Qt Jambi.
Meanwhile, could you try annotating the methods that cause trouble with
the QtBlockedSlot annotation, like this:
@QtBlockedSlot
void fooBar(ClassNotOnClassPath cnocp) {
}
I don't know if this is an acceptable work-around to you, but it might
avoid the function call which causes the exception, so it might be worth
a try until the bug has been fixed.
-- Eskil
Hi Eskil!
Thank you for this workaround. However, It only makes the other exceptions
disappear, but not the one on Viewport$ProjectionType which causes the crash.
I added the @QtBlockedSlot annotation to all methods in Viewport (the affected
class) which contains the enum in its signature, but this does not seem to
have any effect on this particular exception, I'm afraid.
ProjectionType is actually an enum that only appears in the signature of a
getter and a setter, following the conventions for Java properties. Could it
be that (a) the runtime tries to map the getter and setter to a Qt property
and because the type cannot be discoverd and (b) this is not prevented by the
annotation because the issue is not about the discovery of slots in the class
at all?
Seeing how Qt Jambi throws exceptions when there are undiscoverable classes
and enums used in subclasses of QWidget (which happens a *lot* in my code), I
would have to add that annotation in hundreds of places in the source code,
which are tedious to find and debug. So I do not think that this workaround
would be actually feasible as a short or medium term solution, even if we
figure out a way to make it work.
Maybe you should simply add an interface to Qt Jambi which allows registration
of custom classloaders for use by the runtime for all of its reflection magic.
This would nicely side-step the issues that we are discussing here. Custom
classloaders are used quite commonly in complex Java projects (like OSGi based
software).
Regards,
Gregor
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[Qt-jambi-interest] Exceptions and crash after update to Qt Jambi 4.5.x
Hi! I tried to update the version of Qt Jambi that I use to 4.5.x, but it looks like some internal changes since 4.4.3_01 give me serious trouble. During startup of my application I get a sequence of exceptions and then a hard crash, probably as a result of the exceptions. This happens with both 4.5.0_01 and 4.5.2_01, but with the latter I get more verbose output. The stack traces that get logged are the following: QtJambi: Exception pending in native code Exception in thread main java.lang.NoClassDefFoundError: eu/moonlight3d/ml3d/ui/mainwindow/view/Viewport at com.trolltech.qt.internal.MetaObjectTools.internalTypeName(Native Method) at com.trolltech.qt.internal.MetaObjectTools.buildMetaData(MetaObjectTools.java:434) at com.trolltech.qt.gui.QWidget.__qt_QWidget_QWidget_WindowFlags(Native Method) at com.trolltech.qt.gui.QWidget.init(QWidget.java:77) at com.trolltech.qt.gui.QWidget.init(QWidget.java:69) at eu.moonlight3d.ml3d.ui.mainwindow.view.ViewWindowSpace.init(Unknown Source) at eu.moonlight3d.ml3d.ui.mainwindow.MainWindow.init(Unknown Source) at eu.moonlight3d.ml3d.ui.mainwindow.MainWindowFactory.createNew(Unknown Source) at eu.moonlight3d.framework.ui.UIManager.getMainWidget(UIManager.java:344) at eu.moonlight3d.framework.ui.ApplicationWindow.init(ApplicationWindow.java:80) at eu.moonlight3d.framework.State.createMainWindow(State.java:367) at eu.moonlight3d.framework.State.runInteractive(State.java:241) at eu.moonlight3d.ml3d.ML3D.main(Unknown Source) Caused by: java.lang.ClassNotFoundException: eu.moonlight3d.ml3d.ui.mainwindow.view.Viewport at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 13 more QtJambi: Exception pending in native code in file 'qtdynamicmetaobject.cpp':116 Exception in thread main java.lang.NoClassDefFoundError: eu/moonlight3d/ml3d/ui/mainwindow/view/Viewport at com.trolltech.qt.internal.MetaObjectTools.internalTypeName(Native Method) at com.trolltech.qt.internal.MetaObjectTools.buildMetaData(MetaObjectTools.java:434) at com.trolltech.qt.gui.QWidget.__qt_QWidget_QWidget_WindowFlags(Native Method) at com.trolltech.qt.gui.QWidget.init(QWidget.java:77) at com.trolltech.qt.gui.QWidget.init(QWidget.java:69) at eu.moonlight3d.ml3d.ui.mainwindow.view.ViewWindowSpace.init(Unknown Source) at eu.moonlight3d.ml3d.ui.mainwindow.MainWindow.init(Unknown Source) at eu.moonlight3d.ml3d.ui.mainwindow.MainWindowFactory.createNew(Unknown Source) at eu.moonlight3d.framework.ui.UIManager.getMainWidget(UIManager.java:344) at eu.moonlight3d.framework.ui.ApplicationWindow.init(ApplicationWindow.java:80) at eu.moonlight3d.framework.State.createMainWindow(State.java:367) at eu.moonlight3d.framework.State.runInteractive(State.java:241) at eu.moonlight3d.ml3d.ML3D.main(Unknown Source) Caused by: java.lang.ClassNotFoundException: eu.moonlight3d.ml3d.ui.mainwindow.view.Viewport at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
