/in/foo.cc: In function 'int Mul(int, int, int*)':
/in/foo.cc:32:12: warning: 'len' may be used uninitialized in this function [-Wmaybe-uninitialized]
     return len;
            ^~~
/in/foo.cc:7:13: warning: 'len' may be used uninitialized in this function [-Wmaybe-uninitialized]
         int len;
             ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:44:9: warning: 'len' may be used uninitialized in this function [-Wmaybe-uninitialized]
     int len;
         ^~~