/in/foo.cc: In instantiation of 'void BubbleSort(T&) [with T = std::vector<int>]':
/in/foo.cc:54:21:   required from here
/in/foo.cc:29:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < array.size() - 1; i++) {
                     ~~^~~~~~~~~~~~~~~~~~
/in/foo.cc:31:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < array.size() - 1 - i; j++) {
                         ~~^~~~~~~~~~~~~~~~~~~~~~