Реализация функции wait

/* Copyright (C) 1991-2013 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
 
   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.
 
   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.
 
   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */
 
#include <sys/wait.h>
#include <errno.h>
#include <sys/resource.h>
#include <stddef.h>
#include <sysdep-cancel.h>
 
/* Wait for a child to die.  When one does, put its status in *STAT_LOC
   and return its process ID.  For errors, return (pid_t) -1.  */
pid_t
__libc_wait (__WAIT_STATUS_DEFN stat_loc)
{
  if (SINGLE_THREAD_P)
    return INLINE_SYSCALL (wait4, 4, WAIT_ANY, stat_loc, 0,
               (struct rusage *) NULL);
 
  int oldtype = LIBC_CANCEL_ASYNC ();
 
  pid_t result = INLINE_SYSCALL (wait4, 4, WAIT_ANY, stat_loc, 0,
                 (struct rusage *) NULL);
 
  LIBC_CANCEL_RESET (oldtype);
 
  return result;
}
 
weak_alias (__libc_wait, __wait)
weak_alias (__libc_wait, wait)