This is related to the ITKv4 transition - there are some other related bugs, but I can't look them up right now.

Fixed in r21859
See http://viewvc.slicer.org/viewvc.cgi/Slicer4?view=revision&revision=21859 [^]

BUG: Restore functioning of CLI loadable module by fixing ITKv4 regression

Problem is summarize by the discussion posted on the ITK developer list
reported below.

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Question from Jean-Christophe Fillion-Robin:

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.

[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 [^]
// --------------

// --------------
Answer from Brad Lowekamp:

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.
// --------------

Issues:
http://www.na-mic.org/Bug/view.php?id=3042 [^]
http://www.na-mic.org/Bug/view.php?id=3008 [^]

ITK discussion:
http://comments.gmane.org/gmane.comp.lib.itk.devel/1133 [^]

ITK patch:
http://itk.org/gitweb?p=ITK.git;a=commit;h=1679816baef6b95356d9afdd9bd4a481ca08556c [^]
http://review.source.kitware.com/#/c/10645/ [^]

Fixes 0003008
Fixes 0003042

The problem is still the same with the latest nightly build (Slicer-4.2.0-2013-04-24-win-amd64): Grayscale model maker (and probably all other EXECUTABLE_ONLY modules) still crashes.

Fixed in r21950
See http://viewvc.slicer.org/viewvc.cgi/Slicer4?view=revision&revision=21950

BUG: Ensure ITK IOFactory are registered for EXECUTABLE_ONLY cli modules

The library wrapper are now used when compiling either the [executable] or
[executable + shared library] cli module. It allows to call the
"itk::itkFactoryRegistration();" in both cases.

Associated SlicerExecutionModel commit is:

// ---------------------------------------------------
ENH: Use library wrapper in the "EXECUTABLE_ONLY" case
This will allow custom wrapper to execute some code before the main
entry point in both the [exec + shared lib] and [exec only] cases.

The macro "MODULE_STATIC" has also been introduced and can be tested
within the wrapper to discriminate both cases.

Change the component associated with Archive target from RuntimeLibraries
to Development. That way, static library won't be packaged.
// ---------------------------------------------------

Thanks for the fix! Tested on Slicer 4.2.0-2013-04-30 (Win64) and it works well.

Fix committed to 2145-support-for-installing-extension-from-file branch.