/in/foo.cc: In function 'void add(std::vector<int>&, std::vector<int>)':
/in/foo.cc:8:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < b.size(); ++i) {
                       ^
/in/foo.cc:9:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if (i < a.size()) {
               ^