/in/ex6.c: In function 'findBook':
/in/ex6.c:10:5: error: this 'for' clause does not guard... [-Werror=misleading-indentation]
     for(; head!= NULL && head->number != number ; head = head->next);
     ^~~
/in/ex6.c:11:6: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
      return head;
      ^~~~~~
cc1: all warnings being treated as errors