[Insight-developers] Static initialization in itkImageSource causes early registration of ITKIOFactory

Wed Apr 3 13:21:33 EDT 2013

JC,

The generalization of that is to have a method/object that is required to be called or created before any other methods in the ITK library.

For compatibility reasons it was determined that it was not an option to require that call with the ITKv4 revision.

So the current behavior was created with a lot initial time and on going time to our uses and developers.

Brad

On Apr 3, 2013, at 1:09 PM, Jean-Christophe Fillion-Robin <jchris.fillionr at kitware.com> wrote:

> Ultimately, would be great if the library ITKFactoryRegistration we added in Slicer would be provided by ITK. 
> See https://github.com/Slicer/Slicer/commit/03b8961
> 
> I think it could be a good idea, if ITK could provide such library. It would allow application using ITK and having plugin using ITK to not have to do the same "hack". Code would be centralized and tested within ITK. 
> 
> Let me know what you think. I would be happy to contribute a patch to ITK.
> 
> Thanks
> Jc
> 
> 
> On Wed, Apr 3, 2013 at 12:35 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> Brad,
> 
> Is there a way we can test for this in ITK? Better we find it before our customers.
> 
> Bill
> 
> 
> On Wed, Apr 3, 2013 at 12:11 PM, Jean-Christophe Fillion-Robin <jchris.fillionr at kitware.com> wrote:
> Thanks Brad for looking at the issue so quickly :)
> 
> I reviewed your patch in gerrit and posted comment.
> 
> Thanks
> Jc
> 
> 
> On Wed, Apr 3, 2013 at 11:33 AM, Bradley Lowekamp <blowekamp at mail.nih.gov> wrote:
> Hello JC,
> 
> This is quite an interesting side-effect of the changes I introduced.
> 
> I am glad that you were able to figure this out. For a variety of reasons, it's likely a very bad thing for all that to occur during static initialization in ITK. So it certainly needs to be fixed.
> 
> I agree that lazy initialization is the way to go. Unfortunately it needs to be thread safe so its a little more completed.
> 
> ITKv4 performs the factory initialization when the user creates the first ITK object.  And that changed with this patch, and need to be fixed.
> 
> CONCLUSION:
> 
> Inside ITK, we can not use statically initialized ITK object.
> 
> Brad
> 
> On Apr 3, 2013, at 10:54 AM, Jean-Christophe Fillion-Robin <jchris.fillionr at kitware.com> wrote:
> 
>> Hi Brad, 
>> 
>> Following commit 4c47e7d [1] of February 19th and commit defb9c1 [2] of March 1st, due to static initialization, the initialization of ObjectFactory  now happens when ITK shared library are loaded [3][4].
>> 
>> This caused a regression in Slicer where the ObjectFactory were expected to be loaded while attempting to load an image for the first time. 
>> 
>> In Slicer case, the environment variable ITK_AUTOLOAD_PATH was set during the initialization of the qSlicerCoreApplication, which is now too late.
>> 
>> By commenting line where a new ImageRegionSplitterSlowDimension is instantiated [5][6] and updating the method "GetImageRegionSplitter / GetGlobalDefaultSplitter" to return 0 [7][8], the initialization can happen on demand instead of when ITK libraries are loaded.
>> 
>> An easy solution for us would be to ensure the "ITK_AUTOLOAD_PATH" environment variable is set in the application launcher for Windows and Linux application and set in Info.plist file associated with the application bundle on MacOSX [9]
>> 
>> To provide more details, within Slicer we set the CMake variable ITK_NO_IO_FACTORY_REGISTER_MANAGER before doing an "include(${ITK_USE_FILE}) so that IOFactory are loaded only by calling the method "itkFactoryRegistration" associated with a shared library we named ITKFactoryRegistration. This approach allowed us to disable the automatic registration of factory in selected part of the code. More details here [10]
>> 
>> It seems the new ITK commits 4c47e7d and defb9c1 prevent from completely leveraging the use of ITK_NO_IO_FACTORY_REGISTER_MANAGER variable, the code should probably be updated to consider this.
>> 
>> 
>> Let me know what you think.
>> 
>> Thanks
>> Jc
>> 
>> 
>> [1] https://github.com/Kitware/ITK/commit/4c47e7d
>> [2] https://github.com/Kitware/ITK/commit/defb9c1
>> [3] https://github.com/Kitware/ITK/blob/4c47e7d672bad5d83b92c2df5f293cca618e2740/Modules/Core/Common/src/itkImageSource.cxx#L27
>> [4] https://github.com/Kitware/ITK/blob/4c47e7d672bad5d83b92c2df5f293cca618e2740/Modules/Core/Common/src/itkObjectFactoryBase.cxx#L142-144
>> [5] https://github.com/Kitware/ITK/blob/defb9c1d084c8d55df61947587427839f9968ecf/Modules/IO/ImageBase/src/itkImageIOBase.cxx#L760
>> [6] https://github.com/Kitware/ITK/blob/4c47e7d672bad5d83b92c2df5f293cca618e2740/Modules/Core/Common/src/itkImageSource.cxx#L27
>> [7] https://github.com/Kitware/ITK/blob/defb9c1d084c8d55df61947587427839f9968ecf/Modules/IO/ImageBase/src/itkImageIOBase.cxx#L765
>> [8] https://github.com/Kitware/ITK/blob/4c47e7d672bad5d83b92c2df5f293cca618e2740/Modules/Core/Common/src/itkImageSource.cxx#L32
>> [9] http://www.herzbube.ch/blog/2009/01/how-set-environment-variables-mac-os-x-applications
>> [10] https://github.com/Slicer/Slicer/commit/03b8961
>> 
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