Null deref in GpxLayer.java:755

[glebius]

Under certain circumstances trkPnt.customColoring is Null. To reproduce the problem, the following is required:

1) draw.rawgps.large=1
2) LiveGPSPlugin enabled and connected to gpsd. Hint: use gpsfake from gpsd package to reproduce on a computer without GPS receiver.

I haven't yet investigated the problem very good, but my current guess is the following: there is a race between GpxLayer.paint() and the LiveGPSPlugin adding new points to the GPX.

In line 552 there is cycle

for (Collection<WayPoint> segment : data.getLinesIterable(null))

, that adds customColoring to every trackpoint.

Later in line 631 we have same iterator that fills in visibleSegments linked list. And later in that list in line 755 we encounter a trackpoint without customColoring initialized. So, I guess, that between iterator in line 552 and iterator in line 631 the "data" is modified with new points.

[glebius]

Another possibility is that computeCacheInSync is true while should be false. This may lead to trackpoint w/o customColoring initialized.

[Don-vip]

What's the operational impact? An exception, an absence of track coloring?

[anonymous]

Exception, LiveGPSPlugin is unusable. A workaround is draw.rawgps.large=0.

[akks]

Got and fixed this exception while refactoring GpxLayer (thought I introduced it but according to this ticket it was already here)

Should be fixed in 7319/josm, see #5662 (fixing regressions now).
Could you please try it again and close the ticket if fixed?

[Don-vip]

glebius can you please tell us if we can close this ticket? Thanks.

[glebius]

A new instant failure in GpxLayer with LiveGPS (josm 7337, modules updated):

java.lang.NullPointerException
        at org.openstreetmap.josm.gui.layer.gpx.GpxDrawHelper.drawPoints(GpxDrawHelper.java:459)
        at org.openstreetmap.josm.gui.layer.gpx.GpxDrawHelper.drawAll(GpxDrawHelper.java:204)
        at org.openstreetmap.josm.gui.layer.GpxLayer.paint(GpxLayer.java:285)
        at livegps.LiveGpsLayer.paint(LiveGpsLayer.java:108)
        at org.openstreetmap.josm.gui.MapView.paintLayer(MapView.java:536)
        at org.openstreetmap.josm.gui.MapView.paint(MapView.java:631)
        at javax.swing.JComponent.paintChildren(JComponent.java:887)
        at javax.swing.JComponent.paint(JComponent.java:1063)
        at javax.swing.JComponent.paintChildren(JComponent.java:887)
        at javax.swing.JSplitPane.paintChildren(JSplitPane.java:1047)
        at javax.swing.JComponent.paint(JComponent.java:1063)
        at javax.swing.JComponent.paintChildren(JComponent.java:887)
        at javax.swing.JComponent.paint(JComponent.java:1063)
        at javax.swing.JComponent.paintToOffscreen(JComponent.java:5219)
        at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1529)
        at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1452)
        at javax.swing.RepaintManager.paint(RepaintManager.java:1249)
        at javax.swing.JComponent._paintImmediately(JComponent.java:5167)
        at javax.swing.JComponent.paintImmediately(JComponent.java:4978)
        at javax.swing.RepaintManager$3.run(RepaintManager.java:808)
        at javax.swing.RepaintManager$3.run(RepaintManager.java:796)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:769)
        at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:718)
        at javax.swing.RepaintManager.access$1100(RepaintManager.java:62)
        at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1677)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:312)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
        at java.awt.EventQueue.access$200(EventQueue.java:103)
        at java.awt.EventQueue$3.run(EventQueue.java:694)
        at java.awt.EventQueue$3.run(EventQueue.java:692)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Several large GPX points are drawn before exception, thus I suppose, that original problem is fixed. Sorry, ENOTIME for more detailed analysis. Should I open new ticket or can we continue in this one?

[Don-vip]

it's ok to keep this one, thanks.

[Don-vip]

In 7340/josm:

see #10269 - fix NPE (robustness. trkPnt.customColoring should probably not be null)

[Don-vip]

The NPE is fixed but the root cause is probably at another place. akks, can you please have a look at it tomorrow? If I manage to fix the two other points on my TODO list, we could release the tested version on Tuesday morning I think :)

[glebius]

Tested 7340. The crash is fixed, thanks!

However, now the GPX layer produced by LiveGPS plugin has a bug. Unless the entire GPS trace fits the mapping window, the trace blinks and is colored white. If the mapping window is zoomed to a larger area and the entire trace is visible, then problem goes away.

[Don-vip]

Thanks for the feedback.
I prefer to close this ticket now, can you please create a new one for remaining bugs? Thanks.

[akks]

In 7345/josm:

see #10269: avoid null color values in GpxLayer for sure

[akks]

Had not a chance to fix it in time... After looging to the code: the source of problem should be in LiveGPS - it creates new WayPoint objects with customColoring=null and the color cache is not updated every time (elsewhere it would be too slow). This gives coloring problems and previous NPEs.

I have no GPSd with emulated tracks and can not debug the plugin, unfortunately.

The last commit may help a little with strange color effects.

[glebius]

New ticket with instructions to reproduce #10321. Let's continue discussion there.

[glebius]

The last commit did help. Thanks, akks! Will close #10321.