PVS-Studio warning V567 for VNL

unsigned long vnl_random::lrand32()
{
  ....
  mz_array_position = (++mz_array_position) %
                      vnl_random_array_size;
  return p2;
}

This suspicious code was found in VNL project by PVS-Studio static code analyzer.
Warning message is:
V567 Undefined behavior. The 'mz_array_position' variable is modified while being used twice between sequence points. vnl_random.cxx 174

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/