/in/foo.cc: In function 'bool cmp(const Row&, const Row&)':
/in/foo.cc:54:37: error: binding reference of type 'std::string&' {aka 'std::__cxx11::basic_string<char>&'} to 'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} discards qualifiers
   54 |             string &sa = a.cells[col];
      |                                     ^
/in/foo.cc:55:37: error: binding reference of type 'std::string&' {aka 'std::__cxx11::basic_string<char>&'} to 'const __gnu_cxx::__alloc_traits<std::allocator<std::__cxx11::basic_string<char> >, std::__cxx11::basic_string<char> >::value_type' {aka 'const std::__cxx11::basic_string<char>'} discards qualifiers
   55 |             string &sb = b.cells[col];
      |                                     ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:102:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::__cxx11::basic_string<char> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  102 |         for (int j = 0; j < headers.size(); j++) {
      |                         ~~^~~~~~~~~~~~~~~~
/in/foo.cc:117:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::__cxx11::basic_string<char> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  117 |     for (int i = 0; i < headers.size(); i++) {
      |                     ~~^~~~~~~~~~~~~~~~
/in/foo.cc:125:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::__cxx11::basic_string<char> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  125 |         for (int i = 0; i < r.cells.size(); i++) {
      |                         ~~^~~~~~~~~~~~~~~~