# How to address const correctness build issues associated with ITKUltrasound module ?

**URL:** https://discourse.itk.org/t/how-to-address-const-correctness-build-issues-associated-with-itkultrasound-module/4949
**Category:** Engineering
**Created:** [April 27, 2022, 3:33pm UTC](https://discourse.itk.org/t/how-to-address-const-correctness-build-issues-associated-with-itkultrasound-module/4949 "2022-04-27T15:33:59Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![jcfr](https://discourse.itk.org/user_avatar/discourse.itk.org/jcfr/32/2526_2.png) [@jcfr](https://discourse.itk.org/u/jcfr)
#### Post date: [April 27, 2022, 3:33pm UTC](https://discourse.itk.org/t/how-to-address-const-correctness-build-issues-associated-with-itkultrasound-module/4949/1 "2022-04-27T15:33:59Z")

</div>

Issues are summarized in [https://github.com/KitwareMedical/ITKUltrasound/pull/198](https://github.com/KitwareMedical/ITKUltrasound/pull/198) and also copied below for convenience.

These are errors reported when building SlicerITKUltrasound based of [PR SlicerITKUltrasound#78](https://github.com/KitwareMedical/SlicerITKUltrasound/pull/78)

```auto
In file included from /home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.h:105,
                 from /home/jcfr/Projects/SlicerITKUltrasound/GenerateDisplacementFromTimeSeries/GenerateDisplacementFromTimeSeries.cxx:38:
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx: In instantiation of ‘void itk::BlockMatching::StrainWindowBlockAffineTransformCommand<TStrainWindowDisplacemenCalculator, TBlockAffineTransformMetricImageFilter, TStrainImageFilter>::Execute(const itk::Object*, const itk::EventObject&) [with TStrainWindowDisplacemenCalculator = itk::BlockMatching::StrainWindowDisplacementCalculator<itk::Image<float, 2>, itk::Image<itk::Vector<float, 2>, 2>, float>; TBlockAffineTransformMetricImageFilter = itk::BlockMatching::BlockAffineTransformMetricImageFilter<itk::Image<unsigned char, 2>, itk::Image<unsigned char, 2>, itk::Image<float, 2>, float>; TStrainImageFilter = itk::StrainImageFilter<itk::Image<itk::Vector<float, 2>, 2>, float, float>]’:
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx:49:1: required from here
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx:73:5: error: invalid conversion from ‘const OutputImageType*’ {aka ‘const itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*’} to ‘itk::BlockMatching::BlockAffineTransformMetricImageFilter<itk::Image<unsigned char, 2>, itk::Image<unsigned char, 2>, itk::Image<float, 2>, float>::StrainImageType*’ {aka ‘itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*’} [-fpermissive]
   73 | m_BlockAffineTransformMetricImageFilter->SetStrainImage(strainWindower->GetStrainImageFilter()->GetOutput());
      | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      | |
      | const OutputImageType* {aka const itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*}
In file included from /home/jcfr/Projects/Slicer-Release/ITK/Modules/IO/ImageBase/include/itkImageFileReaderException.h:22,
                 from /home/jcfr/Projects/Slicer-Release/ITK/Modules/IO/ImageBase/include/itkImageFileReader.h:20,
                 from /home/jcfr/Projects/SlicerITKUltrasound/GenerateDisplacementFromTimeSeries/GenerateDisplacementFromTimeSeries.cxx:19:
/home/jcfr/Projects/Slicer-Release/ITK/Modules/Core/Common/include/itkMacro.h:1097:33: note: initializing argument 1 of ‘void itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::SetStrainImage(itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::StrainImageType*) [with TFixedImage = itk::Image<unsigned char, 2>; TMovingImage = itk::Image<unsigned char, 2>; TMetricImage = itk::Image<float, 2>; TStrainValueType = float; itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::StrainImageType = itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>]’
 1097 | virtual void Set##name(type * _arg) \
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingBlockAffineTransformMetricImageFilter.h:104:3: note: in expansion of macro ‘itkSetObjectMacro’
  104 | itkSetObjectMacro(StrainImage, StrainImageType);
      | ^ ~~~~~~~~~~~~~~~~

```

```auto
In file included from /home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.h:105,
                 from /home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingDisplacementPipeline.h:42,
                 from /home/jcfr/Projects/SlicerITKUltrasound/GenerateDisplacementFromFrames/GenerateDisplacementFromFrames.cxx:25:
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx: In instantiation of ‘void itk::BlockMatching::StrainWindowBlockAffineTransformCommand<TStrainWindowDisplacemenCalculator, TBlockAffineTransformMetricImageFilter, TStrainImageFilter>::Execute(const itk::Object*, const itk::EventObject&) [with TStrainWindowDisplacemenCalculator = itk::BlockMatching::StrainWindowDisplacementCalculator<itk::Image<float, 2>, itk::Image<itk::Vector<float, 2>, 2>, float>; TBlockAffineTransformMetricImageFilter = itk::BlockMatching::BlockAffineTransformMetricImageFilter<itk::Image<float, 2>, itk::Image<float, 2>, itk::Image<float, 2>, float>; TStrainImageFilter = itk::StrainImageFilter<itk::Image<itk::Vector<float, 2>, 2>, float, float>]’:
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx:49:1: required from here
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingStrainWindowBlockAffineTransformCommand.hxx:73:5: error: invalid conversion from ‘const OutputImageType*’ {aka ‘const itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*’} to ‘itk::BlockMatching::BlockAffineTransformMetricImageFilter<itk::Image<float, 2>, itk::Image<float, 2>, itk::Image<float, 2>, float>::StrainImageType*’ {aka ‘itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*’} [-fpermissive]
   73 | m_BlockAffineTransformMetricImageFilter->SetStrainImage(strainWindower->GetStrainImageFilter()->GetOutput());
      | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      | |
      | const OutputImageType* {aka const itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>*}
In file included from /home/jcfr/Projects/Slicer-Release/ITK/Modules/IO/ImageBase/include/itkImageFileReaderException.h:22,
                 from /home/jcfr/Projects/Slicer-Release/ITK/Modules/IO/ImageBase/include/itkImageFileReader.h:20,
                 from /home/jcfr/Projects/SlicerITKUltrasound/GenerateDisplacementFromFrames/GenerateDisplacementFromFrames.cxx:19:
/home/jcfr/Projects/Slicer-Release/ITK/Modules/Core/Common/include/itkMacro.h:1097:33: note: initializing argument 1 of ‘void itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::SetStrainImage(itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::StrainImageType*) [with TFixedImage = itk::Image<float, 2>; TMovingImage = itk::Image<float, 2>; TMetricImage = itk::Image<float, 2>; TStrainValueType = float; itk::BlockMatching::BlockAffineTransformMetricImageFilter<TFixedImage, TMovingImage, TMetricImage, TStrainValueType>::StrainImageType = itk::Image<itk::SymmetricSecondRankTensor<float, 2>, 2>]’
 1097 | virtual void Set##name(type * _arg) \
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingBlockAffineTransformMetricImageFilter.h:104:3: note: in expansion of macro ‘itkSetObjectMacro’
  104 | itkSetObjectMacro(StrainImage, StrainImageType);
      | ^ ~~~~~~~~~~~~~~~~

```

```auto
In file included from /home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.h:202,
                 from /home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingDisplacementPipeline.h:39,
                 from /home/jcfr/Projects/SlicerITKUltrasound/GenerateDisplacementFromFrames/GenerateDisplacementFromFrames.cxx:25:
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.hxx: In instantiation of ‘void itk::BlockMatching::OptimizingInterpolationDisplacementCalculator<TMetricImage, TDisplacementImage, TCoordRep>::SetMetricImagePixel(const PointType&, const IndexType&, itk::BlockMatching::OptimizingInterpolationDisplacementCalculator<TMetricImage, TDisplacementImage, TCoordRep>::MetricImageType*) [with TMetricImage = itk::Image<float, 2>; TDisplacementImage = itk::Image<itk::Vector<float, 2>, 2>; TCoordRep = double; itk::BlockMatching::OptimizingInterpolationDisplacementCalculator<TMetricImage, TDisplacementImage, TCoordRep>::PointType = itk::Point<double, 2>; itk::BlockMatching::OptimizingInterpolationDisplacementCalculator<TMetricImage, TDisplacementImage, TCoordRep>::IndexType = itk::Index<2>; itk::BlockMatching::OptimizingInterpolationDisplacementCalculator<TMetricImage, TDisplacementImage, TCoordRep>::MetricImageType = itk::Image<float, 2>]’:
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.hxx:41:1: required from here
/home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.hxx:95:5: error: passing ‘const InterpolatorType’ {aka ‘const itk::InterpolateImageFunction<itk::Image<float, 2>, double>’} as ‘this’ argument discards qualifiers [-fpermissive]
   95 | m_CostFunction->GetInterpolator()->SetInputImage(metricImage);
      | ^ ~~~~~~~~~~~~~
In file included from /home/jcfr/Projects/Slicer-Release/ITK/Modules/Core/ImageFunction/include/itkImageFunction.h:229,
                 from /home/jcfr/Projects/Slicer-Release/ITK/Modules/Core/ImageFunction/include/itkInterpolateImageFunction.h:21,
                 from /home/jcfr/Projects/Slicer-Release/ITK/Modules/Core/ImageFunction/include/itkWindowedSincInterpolateImageFunction.h:23,
                 from /home/jcfr/Projects/SlicerITKUltrasound-Release/ITKUltrasound/include/itkBlockMatchingDisplacementPipeline.h:26,
                 from /home/jcfr/Projects/SlicerITKUltrasound/GenerateDisplacementFromFrames/GenerateDisplacementFromFrames.cxx:25:
/home/jcfr/Projects/Slicer-Release/ITK/Modules/Core/ImageFunction/include/itkImageFunction.hxx:57:1: note: in call to ‘void itk::ImageFunction<TInputImage, TOutput, TCoordRep>::SetInputImage(const InputImageType*) [with TInputImage = itk::Image<float, 2>; TOutput = double; TCoordRep = double; itk::ImageFunction<TInputImage, TOutput, TCoordRep>::InputImageType = itk::Image<float, 2>]’
   57 | ImageFunction<TInputImage, TOutput, TCoordRep>::SetInputImage(const InputImageType * ptr)
      | ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

```

cc: @dzenanz @matt.mccormick

---

<div class="post-metadata">

### Author: ![jcfr](https://discourse.itk.org/user_avatar/discourse.itk.org/jcfr/32/2526_2.png) [@jcfr](https://discourse.itk.org/u/jcfr)
#### Post date: [April 27, 2022, 7:33pm UTC](https://discourse.itk.org/t/how-to-address-const-correctness-build-issues-associated-with-itkultrasound-module/4949/2 "2022-04-27T19:33:03Z")

</div>

To follow up, the issue has been addressed adding relevant `const_cast` and switching to use `itkSetConstObjectMacro`

```diff
diff --git a/include/itkBlockMatchingBlockAffineTransformMetricImageFilter.h b/include/itkBlockMatchingBlockAffineTransformMetricImageFilter.h
index 18d4ded..bdd20e7 100644
--- a/include/itkBlockMatchingBlockAffineTransformMetricImageFilter.h
+++ b/include/itkBlockMatchingBlockAffineTransformMetricImageFilter.h
@@ -79,7 +79,7 @@ public:
 
   /** Type of the strain image. */
   using StrainImageType = Image<SymmetricSecondRankTensor<TStrainValueType, ImageDimension>, ImageDimension>;
- using StrainImagePointerType = typename StrainImageType::Pointer;
+ using StrainImagePointerType = typename StrainImageType::ConstPointer;
   using StrainInterpolatorType = LinearInterpolateImageFunction<StrainImageType, double>;
 
   /** Type of the transform. */
@@ -101,7 +101,7 @@ public:
   itkGetConstObjectMacro(MetricImageFilter, Superclass);
 
   /** Set/Get the strain image used to modify the fixed image block. */
- itkSetObjectMacro(StrainImage, StrainImageType);
+ itkSetConstObjectMacro(StrainImage, StrainImageType);
   itkGetConstObjectMacro(StrainImage, StrainImageType);
 
 protected:
diff --git a/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.hxx b/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.hxx
index d65cad7..fa751a5 100644
--- a/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.hxx
+++ b/include/itkBlockMatchingOptimizingInterpolationDisplacementCalculator.hxx
@@ -92,7 +92,7 @@ OptimizingInterpolationDisplacementCalculator<TMetricImage, TDisplacementImage,
     for (unsigned int i = 0; i < ImageDimension; i++)
       parameters[i] += 0.1;
     m_CostFunction->Initialize(parameters);
- m_CostFunction->GetInterpolator()->SetInputImage(metricImage);
+ const_cast<InterpolatorType*>(m_CostFunction->GetInterpolator())->SetInputImage(metricImage);
     m_Optimizer->StartOptimization();
 
     parameters = m_Optimizer->GetCurrentPosition();

```

---

<div class="post-metadata">

### Author: ![Niels\_Dekker](https://discourse.itk.org/letter_avatar_proxy/v4/letter/n/9d8465/32.png) [@Niels\_Dekker](https://discourse.itk.org/u/Niels_Dekker)
#### Post date: [April 28, 2022, 1:52pm UTC](https://discourse.itk.org/t/how-to-address-const-correctness-build-issues-associated-with-itkultrasound-module/4949/3 "2022-04-28T13:52:39Z")

</div>

Is there no way to get “modifiable” access to the interpolator? Possibly by something like `m_CostFunction->GetModifiableInterpolator()`?

`const_cast` should be used reluctantly, of course, as it breaks const-correctness, and it may in some cases cause undefined behavior.

My two cents, Niels