/in/foo.cc: In function 'int main()':
/in/foo.cc:14:21: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   14 |   for (int i = 0; i < strlen(a); i++) {
      |                   ~~^~~~~~~~~~~
/in/foo.cc:13:7: warning: unused variable 'len' [-Wunused-variable]
   13 |   int len = strlen(a);
      |       ^~~