stdlib/atexit.c

   1 /* Copyright (C) 1991, 1996 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <libc-lock.h>
  20 #include <stdlib.h>
  21 #include "exit.h"
  22
  23
  24 /* Register FUNC to be executed by `exit'.  */
  25 int
  26 atexit (void (*func) (void))
  27 {
  28   struct exit_function *new = __new_exitfn ();
  29
  30   if (new == NULL)
  31     return -1;
  32
  33   new->flavor = ef_at;
  34   new->func.at = func;
  35   return 0;
  36 }
  37
  38
  39 /* We change global data, so we need locking.  */
  40 __libc_lock_define_initialized (static, lock)
  41
  42
  43 static struct exit_function_list fnlist = { NULL, 0, };
  44 struct exit_function_list *__exit_funcs = &fnlist;
  45
  46 struct exit_function *
  47 __new_exitfn (void)
  48 {
  49   struct exit_function_list *l;
  50   size_t i = 0;
  51
  52   __libc_lock_lock (lock);
  53
  54   for (l = __exit_funcs; l != NULL; l = l->next)
  55     {
  56       for (i = 0; i < l->idx; ++i)
  57         if (l->fns[i].flavor == ef_free)
  58           break;
  59       if (i < l->idx)
  60         break;
  61
  62       if (l->idx < sizeof (l->fns) / sizeof (l->fns[0]))
  63         {
  64           i = l->idx++;
  65           break;
  66         }
  67     }
  68
  69   if (l == NULL)
  70     {
  71       l = (struct exit_function_list *)
  72         malloc (sizeof (struct exit_function_list));
  73       if (l != NULL)
  74         {
  75           l->next = __exit_funcs;
  76           __exit_funcs = l;
  77
  78           l->idx = 1;
  79           i = 0;
  80         }
  81     }
  82
  83   /* Mark entry as used, but we don't know the flavor now.  */
  84   if (l != NULL)
  85     l->fns[i].flavor = ef_us;
  86
  87   __libc_lock_unlock (lock);
  88
  89   return l == NULL ? NULL : &l->fns[i];
  90 }