/in/foo.cc: In function 'void qsort(int, int)':
/in/foo.cc:7:17: error: return-statement with a value, in function returning 'void' [-fpermissive]
  if(l>r) return 0;
                 ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:25:6: warning: unused variable 'midd' [-Wunused-variable]
  int midd=(n+1)/2;
      ^~~~
/in/foo.cc:26:11: error: 'i' was not declared in this scope
  s+=abs(a[i]-midd);
           ^
/in/foo.cc:26:14: error: 'midd' was not declared in this scope
  s+=abs(a[i]-midd);
              ^~~~