message: BOOST_UNREACHABLE_RETURN + comment
diff: #include <gudhi/Bitmap_cubical_complex/counter.h>
  +#include <boost/config.hpp>
  +
  #include <iostream>
  #include <vector>
  #include <string>
  @@ -115,6 +117,7 @@ class Bitmap_cubical_complex_base {
  * returned. Note that the input parameter can be a cell of any dimension (vertex, edge, etc).
  * On the other hand, the output is always indicating the position of
  * a top-dimensional cube in the data structure.
  + * \pre The filtration values are assigned as per `impose_lower_star_filtration()`.
  **/
  inline size_t get_top_dimensional_coface_of_a_cell(size_t splx);
  @@ -621,7 +624,7 @@ size_t Bitmap_cubical_complex_base<T>::get_top_dimensional_coface_of_a_cell(size
  }
  }
  }
  - return splx;
  + BOOST_UNREACHABLE_RETURN(-2);
  }
  template <typename T>
  