Code Runs on Linux but not macOS High Sierra

ROOT
8 
{
  // name this ROOT macro file "RunMe.cxx" and then debug everything using:
  // valgrind --tool=memcheck --leak-check=full --suppressions=`root-config --etcdir`/valgrind-root.supp `root-config --bindir`/root.exe -b -n -q -l RunMe.cxx
  // valgrind --tool=exp-sgcheck --suppressions=`root-config --etcdir`/valgrind-root.supp `root-config --bindir`/root.exe -b -n -q -l RunMe.cxx
  // note: study valgrind's output messages from running the "iterate"
  gROOT->LoadMacro("testprog.C++g");
  std::cout << " ... starting iterate() ..." << std::endl;
  gROOT->Macro("iterate.C");
  std::cout << " ... finished iterate() ..." << std::endl;
}