stdlib/cxa_atexit.c

   1 /* Copyright (C) 1999, 2001, 2002, 2005 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <assert.h>
  20 #include <stdlib.h>
  21
  22 #include <bits/libc-lock.h>
  23 #include "exit.h"
  24
  25 #undef __cxa_atexit
  26
  27 /* Register a function to be called by exit or when a shared library
  28    is unloaded.  This function is only called from code generated by
  29    the C++ compiler.  */
  30 int
  31 __cxa_atexit (void (*func) (void *), void *arg, void *d)
  32 {
  33   struct exit_function *new = __new_exitfn ();
  34
  35   if (new == NULL)
  36     return -1;
  37
  38   new->flavor = ef_cxa;
  39   new->func.cxa.fn = (void (*) (void *, int)) func;
  40   new->func.cxa.arg = arg;
  41   new->func.cxa.dso_handle = d;
  42   return 0;
  43 }
  44 INTDEF(__cxa_atexit)
  45
  46
  47 /* We change global data, so we need locking.  */
  48 __libc_lock_define_initialized (static, lock)
  49
  50
  51 static struct exit_function_list initial;
  52 struct exit_function_list *__exit_funcs = &initial;
  53
  54 struct exit_function *
  55 __new_exitfn (void)
  56 {
  57   struct exit_function_list *p = NULL;
  58   struct exit_function_list *l;
  59   struct exit_function *r = NULL;
  60   size_t i = 0;
  61
  62   __libc_lock_lock (lock);
  63
  64   for (l = __exit_funcs; l != NULL; p = l, l = l->next)
  65     {
  66       for (i = l->idx; i > 0; --i)
  67         if (l->fns[i - 1].flavor != ef_free)
  68           break;
  69
  70       if (i > 0)
  71         break;
  72
  73       /* This block is completely unused.  */
  74       l->idx = 0;
  75     }
  76
  77   if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
  78     {
  79       /* The last entry in a block is used.  Use the first entry in
  80          the previous block if it exists.  Otherwise create a new one.  */
  81       if (p == NULL)
  82         {
  83           assert (l != NULL);
  84           p = (struct exit_function_list *)
  85             calloc (1, sizeof (struct exit_function_list));
  86           if (p != NULL)
  87             {
  88               p->next = __exit_funcs;
  89               __exit_funcs = p;
  90             }
  91         }
  92
  93       if (p != NULL)
  94         {
  95           r = &p->fns[0];
  96           p->idx = 1;
  97         }
  98     }
  99   else
 100     {
 101       /* There is more room in the block.  */
 102       r = &l->fns[i];
 103       l->idx = i + 1;
 104     }
 105
 106   /* Mark entry as used, but we don't know the flavor now.  */
 107   if (r != NULL)
 108     r->flavor = ef_us;
 109
 110   __libc_lock_unlock (lock);
 111
 112   return r;
 113 }