[Insight-developers] FW: BRAINSCut Warning

[Williams, Norman K]

[Note, after writing this up I logged it as a bug.
https://issues.itk.org/jira/browse/ITK-3021]

One of our developers has encountered a compiler warning using ITK that
seems to me to be

A) a real problem and
B) fixable

In file included from
/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/inclu
de/ITK-4.4/itkImportImageContainer.h:182:
.../ITKv4-install/include/ITK-4.4/itkImportImageContainer.hxx:73:15:
warning: destination for this 'memcpy' call is a pointer to dynamic class
'itk::HammerTissueAttributeVector';
vtable pointer will be
      overwritten [-Wdynamic-class-memaccess]
      memcpy( temp, m_ImportPointer, m_Size * sizeof( TElement ) );
      ~~~~~~  ^
/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/inclu
de/ITK-4.4/itkImage.hxx:57:13: note: in instantiation of member function
'itk::ImportImageContainer<unsigned long,
itk::HammerTissueAttributeVector>::Reserve'
requested here
  m_Buffer->Reserve(num);

Use of memcpy to move a C++ array is a terrible idea.  It might work OK if
A) the object class has no virtual methods B) All class members are plain
ordinary data (e.g. scalars, arrays of scalars)  - OR - C) the object
class' member variables are either POD or class objects satisfying
conditions A&B.

I think the memcpy should be replaced by a 'for' loop that copies array
elements one at a time. This will cause a compiler error if there is no
operator= defined for the Pixel type, but if that is the case, using
memcpy is double plus bad.

This will silence the warnings and preserve C++ object semantics, and the
perfomance penalty is not terrible.  Particularly since the
ImportImageContainer only uses memcpy in the case of growing or shrinking
the container, which I can't imagine happens in the normal course of ITK
usage.

--
Kent Williams norman-k-williams at uiowa.edu






On 4/8/13 12:08 PM, "Kim, Eun Young" <eunyoung-kim at uiowa.edu> wrote:

>Kent,
>
>
>Hans told me to remove the warning, but not sure if that is even
>possible.
>Well, if there seems no simple solution, we could talk to Hans later. :)
>
>
>Code:
>BRAINSTools/BRAINSCut/BRAINSFeatureCreators/HammerAttributeCreator
>
>
>Warning:
>[eunyokim at wundt HammerAttributeCreator (myMaster +)]$ make -C
>../../../../releaseBuild/BRAINSTools-build/BRAINSCut/BRAINSFeatureCreators
>/HammerAttributeCreator/
>Scanning dependencies of target HammerAttributeCreatorLib
>Building CXX object
>BRAINSCut/BRAINSFeatureCreators/HammerAttributeCreator/CMakeFiles/HammerAt
>tributeCreatorLib.dir/HammerAttributeCreator.cxx.o
>In file included from
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/BRAINSTools/BRAINSCut/BRAINSFea
>tureCreators/HammerAttributeCreator/HammerAttributeCreator.cxx:11:
>In file included from
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkImage.h:22:
>In file included from
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkImportImageContainer.h:182:
>.../ITKv4-install/include/ITK-4.4/itkImportImageContainer.hxx:73:15:
>warning: destination for this 'memcpy' call is a pointer to dynamic class
>'itk::HammerTissueAttributeVector';
> vtable pointer will be
>      overwritten [-Wdynamic-class-memaccess]
>      memcpy( temp, m_ImportPointer, m_Size * sizeof( TElement ) );
>      ~~~~~~  ^
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkImage.hxx:57:13: note: in instantiation of member function
>'itk::ImportImageContainer<unsigned long,
>itk::HammerTissueAttributeVector>::Reserve'
> requested here
>  m_Buffer->Reserve(num);
>            ^
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkImage.h:91:15: note: in instantiation of member function
>'itk::Image<itk::HammerTissueAttributeVector, 3>::Allocate'
> requested here
>  itkNewMacro(Self);
>              ^
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkMacro.h:165:21: note: expanded from macro 'itkNewMacro'
>  itkSimpleNewMacro(x)                                         \
>                    ^
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkMacro.h:175:22: note: expanded from macro
>'itkSimpleNewMacro'
>      smartPtr = new x;                                        \
>                     ^
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkImageSource.hxx:67:24: note: in instantiation of member
>function 'itk::Image<itk::HammerTissueAttributeVector, 3>::New'
> requested here
>  return TOutputImage::New().GetPointer();
>                       ^
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/BRAINSTools/BRAINSCut/BRAINSFea
>tureCreators/HammerAttributeCreator/HammerAttributeCreator.cxx:113:25:
>note: in instantiation of member function
>      'itk::ImageSource<itk::Image<itk::HammerTissueAttributeVector, 3>
>>::MakeOutput' requested here
>  modelAttributeFilter->SetStrength(Strength);
>                        ^
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/ITKv4-install/incl
>ude/ITK-4.4/itkImportImageContainer.hxx:73:15: note: explicitly cast the
>pointer to silence this warning
>      memcpy( temp, m_ImportPointer, m_Size * sizeof( TElement ) );
>              ^
>              (void*)
>1 warning generated.
>Linking CXX shared library
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/bin/libHammerAttri
>buteCreatorLib.dylib
>Built target HammerAttributeCreatorLib
>Linking CXX executable
>/ipldev/scratch/eunyokim/src/BRAINS2013Apr/releaseBuild/bin/HammerAttribut
>eCreator
>Built target HammerAttributeCreator
>
>
>
>Just please take a look at the code when you have time.
>
>
>Thank you!
>
>
>Regina



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