Comment by plg

  $ gcc -o test test.c mill.c
  mill.c:221:13: error: conflicting types for 'wait'
   static void wait(int fd, short events) {
               ^
  In file included from /usr/include/stdlib.h:65:0,
                   from mill.c:33:
  /usr/include/sys/wait.h:248:7: note: previous declaration of 'wait' was here
   pid_t wait(int *) __DARWIN_ALIAS_C(wait);
         ^