stdlib/cxa_atexit.c

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