/in/foo.cc: In function 'void mul(int*, int&, int)':
/in/foo.cc:43:6: warning: unused variable 'x' [-Wunused-variable]
  int x = 0, len = lena;
      ^
/in/foo.cc: In function 'void div(int*, int&, int)':
/in/foo.cc:97:21: warning: argument to 'sizeof' in 'void* memset(void*, int, size_t)' call is the same expression as the destination; did you mean to dereference it? [-Wsizeof-pointer-memaccess]
  memset(a, 0, sizeof(a));
                     ^