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

[Bill Lorensen]

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