# Crash in WatershedImageFilter

**URL:** https://discourse.itk.org/t/crash-in-watershedimagefilter/2428
**Category:** Engineering
**Tags:** crash-in-windows, watershedimagefilter
**Created:** [November 20, 2019, 2:40pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428 "2019-11-20T14:40:38Z")
**Posts on this page:** 12
**Page:** 1

<div class="post-metadata">

### Author: ![nm97](https://discourse.itk.org/user_avatar/discourse.itk.org/nm97/32/814_2.png) [@nm97](https://discourse.itk.org/u/nm97)
#### Post date: [November 20, 2019, 2:40pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/1 "2019-11-20T14:40:38Z")

</div>

Hi,  
I am trying to run WatershedImageFilter class function with this arguments(image -{0.,0.,0.,0.,1.f/4503599627370496.f,0.,0.}, 1.0(Level), 0.0(Threshold)).

```auto
#include "itkWatershedImageFilter.h"
#include "itkCastImageFilter.h"
#include "itkRelabelComponentImageFilter.h"
#include <vector>
#include <math.h>

int main( int argc, char *argv[] ) {
  typedef float InternalPixelType;

  const unsigned int Dimension = 2;

  typedef itk::Image< float, Dimension > InputImageType;
  typedef itk::Image< double, Dimension > OutputImageType;

  InputImageType::Pointer image = InputImageType::New();

  int width = 7;
  int height = 1;
  InputImageType::SizeType size;
  size[0] = width;
  size[1] = height;

  InputImageType::RegionType region;
  region.SetSize( size );

  image->SetRegions( region );
  image->Allocate();
  constexpr float gyot = (1.f/4503599627370496.f);
  std::vector<float> arr = {0.,0.,0.,0.,gyot,0.,0.};
  memcpy(image->GetBufferPointer(), arr.data(), width * height * sizeof(float));

  typedef itk::WatershedImageFilter<InputImageType> WatershedFilterType;
  typedef itk::Image<itk::IdentifierType, Dimension> FilteredImageType;
  typedef itk::CastImageFilter<FilteredImageType, OutputImageType> CastFilterType; 
  typedef itk::RelabelComponentImageFilter<FilteredImageType, FilteredImageType> RelabelFilterType;

  WatershedFilterType::Pointer watershedFilter = WatershedFilterType::New();

  watershedFilter->SetInput( image );
  watershedFilter->SetLevel( 1.0 );
  watershedFilter->SetThreshold( 0.0 );
  
  typename RelabelFilterType::Pointer relabeler = RelabelFilterType::New();
  relabeler->SetInput(watershedFilter->GetOutput());

  typename CastFilterType::Pointer caster = CastFilterType::New();
  caster->SetInput(relabeler->GetOutput());

  try
    {
      caster->Update();
    }
  catch( itk::ExceptionObject & excep )
    {
    std::cerr << "Exception caught !" << std::endl;
    std::cerr << excep << std::endl;

    return EXIT_FAILURE;
    }

    std::cout << "Success" << std::endl;

    return EXIT_SUCCESS;

}

```

In Linux everything works fine.(Throws `Description: itk::ERROR: itk::watershed::SegmentTreeGenerator::MergeSegments:: An unexpected and fatal error has occurred. This is probably the result of overthresholding of the input image.`)

But in Windows the result of this code is unstable: It may crash, throw exception or give some segmentation(After running that code several times).  
I’m using ITK’s 5.0.0 version.  
Does anyone know about this problem.  
I would be appreciate any help.  
Thanks Hrach.

---

<div class="post-metadata">

### Author: ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [November 20, 2019, 8:08pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/2 "2019-11-20T20:08:55Z")

</div>

We refactored some internal of Watersheds. More information in [this PR](https://github.com/InsightSoftwareConsortium/ITK/pull/187). Maybe that has something to do with the observed behavior?

---

<div class="post-metadata">

### Author: ![nm97](https://discourse.itk.org/user_avatar/discourse.itk.org/nm97/32/814_2.png) [@nm97](https://discourse.itk.org/u/nm97)
#### Post date: [November 21, 2019, 7:16am UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/3 "2019-11-21T07:16:20Z")

</div>

[dzenanz](https://discourse.itk.org/u/dzenanz) I checked and I have this changes in my ITK version.  
And can not figure out what is the reason of this kind of undefined behaviour.  
In contrast of Windows, Linux constantly throws exception.

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<div class="post-metadata">

### Author: ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [November 21, 2019, 3:33pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/4 "2019-11-21T15:33:21Z")

</div>

For me, it consistently crashes in Visual Studio. I am looking into it.

---

<div class="post-metadata">

### Author: ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [November 21, 2019, 3:56pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/5 "2019-11-21T15:56:28Z")

</div>

The problem is that on [line 169](https://github.com/InsightSoftwareConsortium/ITK/blob/2074c2f9e5ed3f087d0e2059f8e0e8992fcad7ef/Modules/Segmentation/Watersheds/include/itkWatershedSegmentTreeGenerator.hxx#L169), `(*segment_ptr).second.edge_list` is empty, so `.front()` causes a crash. This probably indicates there is a problem in the previous filter in the pipeline, the [WatershedSegmenter](https://github.com/InsightSoftwareConsortium/ITK/blob/2074c2f9e5ed3f087d0e2059f8e0e8992fcad7ef/Modules/Segmentation/Watersheds/include/itkWatershedSegmenter.hxx).

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<div class="post-metadata">

### Author: ![nm97](https://discourse.itk.org/user_avatar/discourse.itk.org/nm97/32/814_2.png) [@nm97](https://discourse.itk.org/u/nm97)
#### Post date: [November 21, 2019, 6:05pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/6 "2019-11-21T18:05:50Z")

</div>

In 4.13.0 I have tested and there is no crash, either it compiles till the end or throws exception(An unexpected fatal error has occurred. This is probably the result of the overthresholding of the input image).  
Is this fixed in 5.1.0 version?

---

<div class="post-metadata">

### Author: ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [November 21, 2019, 6:08pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/7 "2019-11-21T18:08:19Z")

</div>

> [@nm97](#):
>
> Is this fixed in 5.1.0 version?

No. I did my test with a recent master version, so this crash has not been fixed.

---

<div class="post-metadata">

### Author: ![nm97](https://discourse.itk.org/user_avatar/discourse.itk.org/nm97/32/814_2.png) [@nm97](https://discourse.itk.org/u/nm97)
#### Post date: [November 21, 2019, 6:15pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/8 "2019-11-21T18:15:29Z")

</div>

Than you.  
How can I catch this, to not have a crash in the program?

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<div class="post-metadata">

### Author: ![nm97](https://discourse.itk.org/user_avatar/discourse.itk.org/nm97/32/814_2.png) [@nm97](https://discourse.itk.org/u/nm97)
#### Post date: [November 21, 2019, 6:25pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/9 "2019-11-21T18:25:23Z")

</div>

And I want to figure out why doesn’t this crash in Linux?

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<div class="post-metadata">

### Author: ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [November 21, 2019, 6:40pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/10 "2019-11-21T18:40:03Z")

</div>

Try running it in debug mode, maybe some assertions will be triggered.

As de-referencing a null pointer is undefined behavior, compiler usually assumes it will not happen and does optimizations under that assumption. This frequently leeds to no crash occurring in release mode even though it should. And different compilers do different optimizations, so undefined behavior manifests itself differently.

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<div class="post-metadata">

### Author: ![nm97](https://discourse.itk.org/user_avatar/discourse.itk.org/nm97/32/814_2.png) [@nm97](https://discourse.itk.org/u/nm97)
#### Post date: [November 25, 2019, 8:36pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/11 "2019-11-25T20:36:31Z")

</div>

@dzenanz I have tested the same code in 4.13.0 and 5.0.0 with static builds.  
In 4.13.0 it either throws exception or returns the image.  
In contrast of 4.13.0, 5.0.0 time to time crashes the program.  
Which files have been changed in 5.0.0 , which can cause this kind of behaviour?

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<div class="post-metadata">

### Author: ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)
#### Post date: [November 25, 2019, 9:01pm UTC](https://discourse.itk.org/t/crash-in-watershedimagefilter/2428/12 "2019-11-25T21:01:04Z")

</div>

There was a huge number of changes.

```bash
Dzenan@Ryzenator MINGW64 /c/Dev/ITK-git/Modules/Segmentation/Watersheds (master)
$ git diff 520a249306831f1acbc266caabc28a4a94e692de..833c1b8c47fa33364da00f089694144b3e419a75 . > c:/a/watersheds4_5.diff

```

[watersheds4\_5.diff](https://discourse.itk.org/uploads/short-url/obwycnlsKig61GXcVmRvLXE9Eek.diff) (322.3 KB)  
But as I said earlier, the most likely culprit is [PR187](https://github.com/InsightSoftwareConsortium/ITK/pull/187).