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V12.1 - AccessViolation Clearing MrSid Layer

#1

ThinkGeo Team,

Intermittently I’m seeing System.AccessViolationException from ThinkGeo.Dependency.Gdal.dll.

This is occurring somewhere during the following code:

if (TheFeatureLayer.IsOpen == true)
{
    TheFeatureLayer.Close();
}

TheLayerOverlay.Layers.Clear();

TheMapView.Refresh();

Here’s errors while in Debug Mode:

System.AccessViolationException HResult=0x80004003
Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
Source=
StackTrace:

An unhandled exception of type ‘System.AccessViolationException’ occurred in ThinkGeo.Dependency.Gdal.dll
Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

The program ‘[7216] OriStarRaster.exe’ has exited with code -1073741819 (0xc0000005) ‘Access violation’.

My code has try/catch logic as well as both the LayerOverlay and RasterLayer Drawing/Drawn Exceptions implemented and still not able to catch this exception…

Looks to me like it is a timing issue.

This occurs more often when the application is started directly as opposed to running in Debug Mode.

I should add too that the application has a push button to invoke the above code leaving the application running. I’ve never seen this if I just shut down the application.

This issue might be related to, or aggravated by, LayerOverlay.TileBuffer. It set to 0 the access violation does not occur, but when set to 2 it does occur.

Regards,
Dennis

#2

Thanks Dennis,
Yes. I can reproduce this one. I think this because the MrSidLayer object not full release. You can use MrSidLayer = null; to release the object.

Here is the full code.

 private void Button_Click(object sender, RoutedEventArgs e)
        {
            if (MrSidLayer.IsOpen == true)
            {
                MrSidLayer.Close();
            }
            MrSidLayer = null;
            overLay.Layers.Clear();
            map.Refresh();
        }

Thanks

Frank

#3

hi Frank,

I’m afraid setting the layer to null does not change the situation.

I feel pretty confident this is a timing issue between the UI thread and ThinkGeo drawing threads.

What I think is occurring is that the Close() and Layers.Clear() are invoked while the drawing thread is still active and attempting to access memory that is no longer available.

Dennis

#4

Thanks Dennis,
The MrsidLayer will Gdal which will use unmanaged libary. I did more test. It mostly likely happen when the map still drawing. So I added a check. Make sure the map has done drawing. I attached you the project.
Demo.zip (1.2 MB)

Thanks

Frank