title: How to fix "struct 'FILE' has no member named'__pad'" error when using $make in apue.3e in ubuntu-18.10
body: <p>I'm a newbie in learning APUE. And there are some errors I don't know how to fix when I'm using $make in apue.3e folder. By the way, I use ubuntu-18.10.</p>
  
  <pre><code>buf.c:104:13: note: in expansion of macro ‘_flag’
    return(fp-&gt;_flag &amp; _IOLBF);
               ^~~~~
  buf.c: In function ‘buffer_size’:
  buf.c:92:15: error: ‘FILE’ {aka ‘struct _IO_FILE’} has no member named ‘__pad’; did you mean ‘__pad5’?
   #define _base __pad[2]
                 ^~~~~
  buf.c:111:13: note: in expansion of macro ‘_base’
    return(fp-&gt;_base - fp-&gt;_ptr);
               ^~~~~
  buf.c:91:14: error: ‘FILE’ {aka ‘struct _IO_FILE’} has no member named ‘__pad’; did you mean ‘__pad5’?
   #define _ptr __pad[1]
                ^~~~~
  buf.c:111:25: note: in expansion of macro ‘_ptr’
    return(fp-&gt;_base - fp-&gt;_ptr);
                           ^~~~
  buf.c: In function ‘is_unbuffered’:
  buf.c:99:1: warning: control reaches end of non-void function [-Wreturn-type]
   }
   ^
  buf.c: In function ‘is_linebuffered’:
  buf.c:105:1: warning: control reaches end of non-void function [-Wreturn-type]
   }
   ^
  buf.c: In function ‘buffer_size’:
  buf.c:115:1: warning: control reaches end of non-void function [-Wreturn-type]
   }
  </code></pre>