/in/foo.cc: In function 'int main()':
/in/foo.cc:15:21: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   15 |   for (int i = 0; i <= strlen(c) - 1; i++) {
      |                   ~~^~~~~~~~~~~~~~~~