ENH: ITKv5 override consistency

Provide remove virtual and override

Use clang-tidy to add ITK_OVERRIDE, and to remove
redundant virtual on functions.

cd ../ITK;
clang-tidy -p ITK-clangtidy $find Modules/[A-J]*  -name *.cxx |fgrep -v ThirdParty) -checks=-*,modernize-use-override  -header-filter=.* -fix
clang-tidy -p ITK-clangtidy $(find Modules/[K-Z]*  -name *.cxx |fgrep -v ThirdParty) -checks=-*,modernize-use-override  -header-filter=.* -fix

https://stackoverflow.com/questions/39932391/virtual-override-or-both-c

When you override a function you don't technically need to write either virtual
or override.

The original base class declaration needs the keyword virtual to mark it as virtual.

In the derived class the function is virtual by way of having the ¹same type as
the base class function.

However, an override can help avoid bugs by producing a compilation error when
the intended override isn't technically an override. E.g. that the function
type isn't exactly like the base class function. Or that a maintenance of the
base class changes that function's type, e.g. adding a defaulted argument.

In the same way, a virtual keyword in the derived class can make such a bug
more subtle, by ensuring that the function is still is virtual in further
derived classes.

So the general advice is,

virtual for the base class function declaration.
This is technically necessary.

Use override (only) for a derived class' override.
This helps with maintenance.

Author: hjmjohnson

include/itkCoocurrenceTextureFeaturesImageFilter.h

@@ -208,7 +208,7 @@ class ITK_TEMPLATE_EXPORT CoocurrenceTextureFeaturesImageFilter
   typedef typename NeighborhoodIteratorType::NeighborIndexType             NeighborIndexType;
 
   CoocurrenceTextureFeaturesImageFilter();
-  virtual ~CoocurrenceTextureFeaturesImageFilter() {}
+  ~CoocurrenceTextureFeaturesImageFilter() ITK_OVERRIDE {}
 
   bool IsInsideNeighborhood(const OffsetType &iteratedOffset);
   void ComputeFeatures(const vnl_matrix<unsigned int> &hist, const unsigned int totalNumberOfFreq,
@@ -219,14 +219,14 @@ class ITK_TEMPLATE_EXPORT CoocurrenceTextureFeaturesImageFilter
                                 double & marginalMean,
                                 double & marginalDevSquared,
                                 double & pixelVariance);
-  virtual void PrintSelf( std::ostream & os, Indent indent ) const ITK_OVERRIDE;
+  void PrintSelf( std::ostream & os, Indent indent ) const ITK_OVERRIDE;
 
   /** This method causes the filter to generate its output. */
-  virtual void BeforeThreadedGenerateData() ITK_OVERRIDE;
-  virtual void AfterThreadedGenerateData() ITK_OVERRIDE;
-  virtual void ThreadedGenerateData(const OutputRegionType & outputRegionForThread,
+  void BeforeThreadedGenerateData() ITK_OVERRIDE;
+  void AfterThreadedGenerateData() ITK_OVERRIDE;
+  void ThreadedGenerateData(const OutputRegionType & outputRegionForThread,
                                     ThreadIdType threadId) ITK_OVERRIDE;
-  virtual void GenerateOutputInformation() ITK_OVERRIDE;
+  void GenerateOutputInformation() ITK_OVERRIDE;
 
 private:
   typename DigitizedImageType::Pointer  m_DigitizedInputImage;

include/itkFirstOrderTextureFeaturesImageFilter.h

@@ -93,7 +93,7 @@ class ITK_TEMPLATE_EXPORT FirstOrderTextureFeaturesImageFilter:
   {
   }
 
-  void GenerateOutputInformation()
+  void GenerateOutputInformation() ITK_OVERRIDE
   {
     // this methods is overloaded so that if the output image is a
     // VectorImage then the correct number of components are set.
@@ -112,7 +112,7 @@ class ITK_TEMPLATE_EXPORT FirstOrderTextureFeaturesImageFilter:
   }
 
 
-  ~FirstOrderTextureFeaturesImageFilter() {}
+  ~FirstOrderTextureFeaturesImageFilter() ITK_OVERRIDE {}
 private:
   FirstOrderTextureFeaturesImageFilter(const Self &); //purposely not implemented
   void operator=(const Self &);                  //purposely not implemented

include/itkRunLengthTextureFeaturesImageFilter.h

@@ -232,7 +232,7 @@ class ITK_TEMPLATE_EXPORT RunLengthTextureFeaturesImageFilter
   typedef typename NeighborhoodIteratorType::NeighborIndexType             NeighborIndexType;
 
   RunLengthTextureFeaturesImageFilter();
-  virtual ~RunLengthTextureFeaturesImageFilter() {}
+  ~RunLengthTextureFeaturesImageFilter() ITK_OVERRIDE {}
 
   void NormalizeOffsetDirection(OffsetType &offset);
   bool IsInsideNeighborhood(const OffsetType &iteratedOffset);
@@ -241,14 +241,14 @@ class ITK_TEMPLATE_EXPORT RunLengthTextureFeaturesImageFilter
                           const OffsetType &offset, const unsigned int &pixelDistance);
   void ComputeFeatures( vnl_matrix<unsigned int> &hist, const unsigned int &totalNumberOfRuns,
                        typename TOutputImage::PixelType &outputPixel);
-  virtual void PrintSelf( std::ostream & os, Indent indent ) const ITK_OVERRIDE;
+  void PrintSelf( std::ostream & os, Indent indent ) const ITK_OVERRIDE;
 
   /** This method causes the filter to generate its output. */
-  virtual void BeforeThreadedGenerateData() ITK_OVERRIDE;
-  virtual void AfterThreadedGenerateData() ITK_OVERRIDE;
-  virtual void ThreadedGenerateData(const OutputRegionType & outputRegionForThread,
+  void BeforeThreadedGenerateData() ITK_OVERRIDE;
+  void AfterThreadedGenerateData() ITK_OVERRIDE;
+  void ThreadedGenerateData(const OutputRegionType & outputRegionForThread,
                                     ThreadIdType threadId) ITK_OVERRIDE;
-  virtual void GenerateOutputInformation() ITK_OVERRIDE;
+  void GenerateOutputInformation() ITK_OVERRIDE;
 
 private:
   typename DigitizedImageType::Pointer  m_DigitizedInputImage;