Error: this statement may fall through [-Werror=implicit-fallthrough=]

Question

I am trying to compile mitk on ubuntu and I got this error:

error: this statement may fall through [-Werror=implicit-fallthrough=]

Here there is a part of code:

      /** Get memory offset for a given image index */
      unsigned int GetOffset(const IndexType & idx) const
      {
       const unsigned int * imageDims = m_ImageDataItem->m_Dimensions;

        unsigned int offset = 0;
        switch(VDimension)
        {
        case 4:
         offset = offset + idx[3]*imageDims[0]*imageDims[1]*imageDims[2];
        case 3:
        offset = offset + idx[2]*imageDims[0]*imageDims[1];
        case 2:
        offset  = offset + idx[0] + idx[1]*imageDims[0];
         break;
        }

        return offset;
      }

I would be appreciate for any help please.

Answer 1

I am trying to compile mitk on ubuntu and I got this error :

error: this statement may fall through [-Werror=implicit-fallthrough=]

Here there is a part of code :

      /** Get memory offset for a given image index */
      unsigned int GetOffset(const IndexType & idx) const
      {
       const unsigned int * imageDims = m_ImageDataItem->m_Dimensions;

        unsigned int offset = 0;
        switch(VDimension)
        {
        case 4:
         offset = offset + idx[3]*imageDims[0]*imageDims[1]*imageDims[2];
        case 3:
        offset = offset + idx[2]*imageDims[0]*imageDims[1];
        case 2:
        offset  = offset + idx[0] + idx[1]*imageDims[0];
         break;
        }

        return offset;
      }

I would be appreciate for any help please.

Answer 2

I am trying to compile mitk on ubuntu and I got this error :

error: this statement may fall through [-Werror=implicit-fallthrough=]

Here there is a part of code :

      /** Get memory offset for a given image index */
      unsigned int GetOffset(const IndexType & idx) const
      {
       const unsigned int * imageDims = m_ImageDataItem->m_Dimensions;

        unsigned int offset = 0;
        switch(VDimension)
        {
        case 4:
         offset = offset + idx[3]*imageDims[0]*imageDims[1]*imageDims[2];
        case 3:
        offset = offset + idx[2]*imageDims[0]*imageDims[1];
        case 2:
        offset  = offset + idx[0] + idx[1]*imageDims[0];
         break;
        }

        return offset;
      }

I would be appreciate for any help please.

Answer 3

I am trying to compile mitk on ubuntu and I got this error :

error: this statement may fall through [-Werror=implicit-fallthrough=]

Here there is a part of code :

      /** Get memory offset for a given image index */
      unsigned int GetOffset(const IndexType & idx) const
      {
       const unsigned int * imageDims = m_ImageDataItem->m_Dimensions;

        unsigned int offset = 0;
        switch(VDimension)
        {
        case 4:
         offset = offset + idx[3]*imageDims[0]*imageDims[1]*imageDims[2];
        case 3:
        offset = offset + idx[2]*imageDims[0]*imageDims[1];
        case 2:
        offset  = offset + idx[0] + idx[1]*imageDims[0];
         break;
        }

        return offset;
      }

I would be appreciate for any help please.

Answer 4

Assuming the code is correct, just add -Wno-implicit-fallthrough to the compiler flags if you can. This is often CFLAGS or CXXFLAGS in the Makefile.

As others have said, the code for cases 4, 3, and 2 will be executed in that order when VDimension is 4 because there are no break statements to stop it. If that's the intended behavior (and I suspect it is) then the compiler is annoyingly warning you that the switch statement is doing exactly what it should do.