Suspicious loop condition `i = iend` in ildl.hh:35

https://gitlab.dune-project.org/core/dune-istl/blob/master/dune/istl/ildl.hh#L35:

  template< class Matrix >
  inline static void bildl_subtractBCT ( const Matrix &B, const Matrix &CT, Matrix &A )
  {
    for( auto i = A.begin(), iend = A.end(); i = iend; ++i )
    { // ...

This was reported to me by @michael.haidl, who was annoyed by the compiler warning...