[Kde-java] java threads + events + segfaults

[Richard Dale]

Hi Benji

On Thursday 13 April 2006 10:48, Benji Weber wrote:
> Greetings,
>
> The below code produces segfaults such as
>
> #
> # An unexpected error has been detected by HotSpot Virtual Machine:
> #
> #  SIGSEGV (0xb) at pc=0x00002aaaaaf88849, pid=1270, tid=1078753600
> #
> # Java VM: Java HotSpot(TM) 64-Bit Server VM (1.5.0_06-b05 mixed mode)
> # Problematic frame:
> # C  [libqtjava.so.1.0.0+0x261849] 
> Java_org_kde_qt_QCustomEvent_finalize+0x49 #
> # An error report file with more information is saved as hs_err_pid1270.log
> #
> # If you would like to submit a bug report, please visit:
> #   http://java.sun.com/webapps/bugreport/crash.jsp
> #
>
> After clicking the segfaults button, at some point after the message
> box has shown, moving/resizing the window tends to speed this up.
>
> If one stops the Event from being garbage collected as the "won't
> segfault" button does then there is no problem.
>
> Presumably this is an issue with qtjava?
>
> Benji
> ========================
>
> import org.kde.qt.*;
>
> public class ThreadTest extends QWidget
> {
> 	ThreadTest()
> 	{
>  		QVBoxLayout mainLayout = new QVBoxLayout(this,12,12,"MainLayout");
> 		mainLayout.setAutoAdd(true);
> 		QPushButton pushButton = new QPushButton("Segfaults",this,"Hello");
> //this will segfault at some point after message box shown - resizing
> or moving the window often triggers this
> 		QObject.connect( pushButton, SIGNAL( "clicked( )" ), this, SLOT(
> "onClick()" ) );
> 		QPushButton anotherPushButton = new QPushButton("won't
> segfault",this,"Hello2"); //this won't
> 		QObject.connect( anotherPushButton, SIGNAL( "clicked( )" ), this,
> SLOT( "onClick2()" ) );
> 	}
>
> 	private void onClick()
> 	{
> 		DoSomething doSomething = new DoSomething("test","test",this);
> 		doSomething.start();
> 	}
>
> 	private void onClick2()
> 	{
> 		DoSomethingElse doSomething = new DoSomethingElse("test","test",this);
> 		doSomething.start();
> 	}
>
>
> 	public static void main(String[] args)
> 	{
> 		QApplication myapp = new QApplication(args);
> 		ThreadTest mywidget = new ThreadTest();
> 		mywidget.setGeometry(50, 500, 400, 400);
>
> 		myapp.setMainWidget(mywidget);
> 		mywidget.show();
> 		myapp.exec();
> 		return;
> 	}
>
> 	public void customEvent(QCustomEvent evt)
> 	{
> 		System.out.println("got custom event");
> 		if (evt.type() == 65432)
> 		{
> 			MessageEvent event = (MessageEvent) evt;
> 			System.out.println(event.getTitle());
> 			QMessageBox.critical(this,event.getTitle(), event.getText());
> 		}
> 	}
>
> 	static {
> 		qtjava.initialize();
> 	}
> }
>
> class DoSomething extends Thread
> {
> 	private String text;
> 	private String title;
> 	private QWidget caller;
>
> 	public DoSomething(String title, String text,QWidget caller)
> 	{
> 		this.caller = caller;
> 		this.text = text;
> 		this.title = title;
> 	}
> 	public void run()
> 	{
> 		System.out.println("Thread running");
> 		MessageEvent event = new MessageEvent(title,text);
> 		QApplication.postEvent(caller,event);
> 		System.out.println("Thread finishing");
> 	}
> }
>
> class DoSomethingElse extends Thread
> {
> 	private String text;
> 	private String title;
> 	private QWidget caller;
>
> 	public DoSomethingElse(String title, String text,QWidget caller)
> 	{
> 		this.caller = caller;
> 		this.text = text;
> 		this.title = title;
> 	}
> 	public void run()
> 	{
> 		System.out.println("Thread running");
> 		MessageEvent event = new MessageEvent(title,text);
> 		QApplication.postEvent(caller,event);
> 		dont.gc(event);
> 		System.out.println("Thread finishing");
> 	}
> }
>
> class dont //xxx
> {
> 	private static java.util.ArrayList dump = new java.util.ArrayList();
> 	static void gc(java.lang.Object o)
> 	{
> 		dump.add(o);
> 	}
> }
>
> class MessageEvent extends QCustomEvent
> {
> 	private String title;
> 	private String text;
> 	public MessageEvent(String title, String text)
> 	{
> 		super(65432);
> 		this.title = title;
> 		this.text = text;
> 	}
>
> 	public String getTitle(){return title;}
> 	public String getText(){return text;}
> }
I think you'd be better off using the pretty much undocumented QtUtils class 
for this. Have a look at the code in QtUtils.cpp and QtUtils.java, and see if 
it seems to be what you want. I'm afraid I didn't write it and don't know 
much about it, but I think it does work and allows you to coordinate Java 
threads with a Qt one.

Regards
-- Richard