Bug 537364

Description Andrey Loskutov 2018-07-25 04:28:09 EDT

Found during bug 532632 investigations.

DateTime.dispose() leaks disposed DateTime instances in the Display.widgetTable since bug 394534.

This happens because createHandleForDateTime() assigns the same handle to two fields used in register()/deregister() methods:

handle = textEntryHandle;
containerHandle = textEntryHandle;

To reproduce, simply run snippet below. It inspects Display.widgetTable before/after DateTime disposal and throws an assert if after the disposal the widget is still in the widgetTable.

I plan to provide a patch/test for it.

package snippet;

import java.lang.reflect.Field;

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.DateTime;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Widget;

public class DateTimeLeaks {

	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = createShell(display);
		shell.open();
		
		Widget[] widgetTable = getWidgetTable(display);
		
		Button b = new Button(shell, 0);
		assertExists(widgetTable, b);
		
		DateTime dt = new DateTime(shell, SWT.DATE);
		assertExists(widgetTable, dt);
		
		b.dispose();
		assertNotExists(widgetTable, b);
		
		dt.dispose();
		assertNotExists(widgetTable, dt);
		
		while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) {
				display.sleep();
			}
		}
		display.dispose();
	}
	
	static void assertExists(Widget[] widgetTable, Object o) {
		for (Widget widget : widgetTable) {
			if(widget == o) {
				return;
			}
		}
		throw new AssertionError("Widget table miss: " + o);		
	}
	
	static void assertNotExists(Widget[] widgetTable, Object o) {
		for (Widget widget : widgetTable) {
			if(widget == o) {
				throw new AssertionError("Widget table leaks: " + o);
			}
		}
	}
	
	static Widget[] getWidgetTable(Display display) {
		try {
			Field field = Display.class.getDeclaredField("widgetTable");
			field.setAccessible(true);
			Widget[] widgetTable = (Widget[]) field.get(display);
			return widgetTable;
		} catch (Throwable t) {
			t.printStackTrace();
			return null;
		}
	}
	
	static Shell createShell(Display display) {
		Shell shell = new Shell(display);
		shell.setLayout(new GridLayout());
		shell.setSize(300, 300);
		return shell;
	}

}