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

[Jean-Christophe Fillion-Robin]

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
>
>
> <https://github.com/Kitware/ITK/blob/4c47e7d672bad5d83b92c2df5f293cca618e2740/Modules/Core/Common/src/itkImageSource.cxx#L27>
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