Cleaning freespace on Seagate external drive crashes at end

[Rishu73]

I captured the errors in a debugger, so I have call stacks and the like:

Output:
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\Eraser.Util.FileSystem.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\WinSxS\amd64_microsoft.vc90.crt_1fc8b3b9a1e18e3b_9.0.30729.6161_none_08e61857a83bc251\msvcm90.dll', Symbols loaded.
A first chance exception of type 'System.IO.IOException' occurred in Eraser.Util.dll

Additional information: Could not lock volume.


Callstack:
Eraser.Util.dll!Eraser.Util.VolumeLock.VolumeLock(System.IO.FileStream stream) + 0x145 bytes
Eraser.Util.dll!Eraser.Util.VolumeInfo.LockVolume(System.IO.FileStream stream) + 0x26 bytes
Eraser.DefaultPlugins.dll!Eraser.DefaultPlugins.FatFileSystem.EraseDirectoryStructures(Eraser.Util.VolumeInfo info, Eraser.Manager.FileSystemEntriesEraseProgress callback) + 0x13d bytes
Eraser.Manager.dll!Eraser.Manager.DirectExecutor.EraseUnusedSpace(Eraser.Manager.Task task, Eraser.Manager.UnusedSpaceTarget target, Eraser.Manager.DirectExecutor.TaskProgressManager progress) + 0x899 bytes
Eraser.Manager.dll!Eraser.Manager.DirectExecutor.Main() + 0x3f6 bytes
mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x9b bytes
mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() + 0x4d bytes


Crash:

Output:
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_64\mscorlib\2.0.0.0__b77a5c561934e089\mscorlib.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\Eraser.exe'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\Eraser.Manager.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_MSIL\System.Windows.Forms\2.0.0.0__b77a5c561934e089\System.Windows.Forms.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_MSIL\System\2.0.0.0__b77a5c561934e089\System.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_MSIL\System.Drawing\2.0.0.0__b03f5f7f11d50a3a\System.Drawing.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_MSIL\Microsoft.VisualBasic\8.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualBasic.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\Eraser.Util.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\Plugins\Eraser.DefaultPlugins.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_MSIL\System.Core\3.5.0.0__b77a5c561934e089\System.Core.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\en\Eraser.resources.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\BevelLine.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_MSIL\System.Xml\2.0.0.0__b77a5c561934e089\System.Xml.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\Plugins\en\Eraser.DefaultPlugins.resources.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\en\Eraser.Manager.resources.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\assembly\GAC_MSIL\System.Configuration\2.0.0.0__b03f5f7f11d50a3a\System.Configuration.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Program Files\Eraser\Eraser.Util.FileSystem.dll'
'Eraser.exe' (Managed (v2.0.50727)): Loaded 'C:\Windows\WinSxS\amd64_microsoft.vc90.crt_1fc8b3b9a1e18e3b_9.0.30729.6161_none_08e61857a83bc251\msvcm90.dll', Symbols loaded.
An unhandled exception of type 'System.NullReferenceException' occurred in Eraser.Util.dll

Additional information: Object reference not set to an instance of an object.

Callstack:
Eraser.Util.dll!Eraser.Util.VolumeLock.Dispose(bool disposing) + 0x24 bytes
Eraser.Util.dll!Eraser.Util.VolumeLock.Finalize() + 0x19 bytes

[Joel]

Thanks! VolumeLock wasn't implemented properly; if the volume was not locked, an exception would be thrown (correct) but the deterministic cleanup code did not handle the situation correctly (which was wrong). I've fixed this in r2780.