Bug: t8_vtk_writer.h is not "C-safe" for T8_ENABLE_VTK #2171
Description
Bug report
Describe the bug
Although being a .h file, the header t8_vtk_writer.h is not "C-safe" if T8_ENABLE_VTK is set, because in that case it includes vtkUnstructuredGrid.h, which requires C++.
It is not an urgent problem, because it is currently not included from any pure C file, but I stumbled over it when trying to (found a good workaround, though).
Note also that unlinke Clang, gcc does not necessarily throw an error, but I'd argue it still is not want we want to do in a C header file.
Possible solution
Move all vtk-library-related functionality (i.e., C++ functionality) to t8_vtk_writer.hxx
Estimated priority
"Priority: low" Should be solved eventually