stdlib/cxa_atexit.c

   1 /* Copyright (C) 1999,2001,2002,2005,2006,2009 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <assert.h>
  19 #include <stdlib.h>
  20
  21 #include <bits/libc-lock.h>
  22 #include "exit.h"
  23 #include <atomic.h>
  24 #include <sysdep.h>
  25
  26 #undef __cxa_atexit
  27
  28
  29 int
  30 attribute_hidden
  31 __internal_atexit (void (*func) (void *), void *arg, void *d,
  32                    struct exit_function_list **listp)
  33 {
  34   struct exit_function *new = __new_exitfn (listp);
  35
  36   if (new == NULL)
  37     return -1;
  38
  39 #ifdef PTR_MANGLE
  40   PTR_MANGLE (func);
  41 #endif
  42   new->func.cxa.fn = (void (*) (void *, int)) func;
  43   new->func.cxa.arg = arg;
  44   new->func.cxa.dso_handle = d;
  45   atomic_write_barrier ();
  46   new->flavor = ef_cxa;
  47   return 0;
  48 }
  49
  50
  51 /* Register a function to be called by exit or when a shared library
  52    is unloaded.  This function is only called from code generated by
  53    the C++ compiler.  */
  54 int
  55 __cxa_atexit (void (*func) (void *), void *arg, void *d)
  56 {
  57   return __internal_atexit (func, arg, d, &__exit_funcs);
  58 }
  59 INTDEF(__cxa_atexit)
  60
  61
  62 /* We change global data, so we need locking.  */
  63 __libc_lock_define_initialized (static, lock)
  64
  65
  66 static struct exit_function_list initial;
  67 struct exit_function_list *__exit_funcs = &initial;
  68 uint64_t __new_exitfn_called;
  69
  70 struct exit_function *
  71 __new_exitfn (struct exit_function_list **listp)
  72 {
  73   struct exit_function_list *p = NULL;
  74   struct exit_function_list *l;
  75   struct exit_function *r = NULL;
  76   size_t i = 0;
  77
  78   __libc_lock_lock (lock);
  79
  80   for (l = *listp; l != NULL; p = l, l = l->next)
  81     {
  82       for (i = l->idx; i > 0; --i)
  83         if (l->fns[i - 1].flavor != ef_free)
  84           break;
  85
  86       if (i > 0)
  87         break;
  88
  89       /* This block is completely unused.  */
  90       l->idx = 0;
  91     }
  92
  93   if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
  94     {
  95       /* The last entry in a block is used.  Use the first entry in
  96          the previous block if it exists.  Otherwise create a new one.  */
  97       if (p == NULL)
  98         {
  99           assert (l != NULL);
 100           p = (struct exit_function_list *)
 101             calloc (1, sizeof (struct exit_function_list));
 102           if (p != NULL)
 103             {
 104               p->next = *listp;
 105               *listp = p;
 106             }
 107         }
 108
 109       if (p != NULL)
 110         {
 111           r = &p->fns[0];
 112           p->idx = 1;
 113         }
 114     }
 115   else
 116     {
 117       /* There is more room in the block.  */
 118       r = &l->fns[i];
 119       l->idx = i + 1;
 120     }
 121
 122   /* Mark entry as used, but we don't know the flavor now.  */
 123   if (r != NULL)
 124     {
 125       r->flavor = ef_us;
 126       ++__new_exitfn_called;
 127     }
 128
 129   __libc_lock_unlock (lock);
 130
 131   return r;
 132 }