/in/foo.cc: In function 'std::__cxx11::string gjd(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:22:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<a.length(); i++) {
               ~^~~~~~~~~~~
/in/foo.cc:25:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<b.length(); i++) {
               ~^~~~~~~~~~~
/in/foo.cc:45:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(start=0; start<num.size(); start++) {
               ~~~~~^~~~~~~~~~~
/in/foo.cc:49:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=start; i<num.size(); i++) {
                   ~^~~~~~~~~~~
/in/foo.cc: In function 'std::__cxx11::string gjd2(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:73:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(i<a1.size()) c +=a1[i];
      ~^~~~~~~~~~
/in/foo.cc:74:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(i<b1.size()) c +=b1[i];
      ~^~~~~~~~~~
/in/foo.cc: In function 'std::__cxx11::string gjd(std::__cxx11::string, std::__cxx11::string)':
/in/foo.cc:29:6: warning: 'start' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int start;
      ^~~~~