/in/foo.cc: In function 'int multiply(char*, char*)':
/in/foo.cc:5:6: warning: unused variable 'lena' [-Wunused-variable]
  int lena=strlen(a),lenb=strlen(b);
      ^~~~
/in/foo.cc:5:21: warning: unused variable 'lenb' [-Wunused-variable]
  int lena=strlen(a),lenb=strlen(b);
                     ^~~~
/in/foo.cc:6:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^