stdlib/cxa_atexit.c

   1 /* Copyright (C) 1999-2016 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 #include <stdint.h>
  21
  22 #include <libc-lock.h>
  23 #include "exit.h"
  24 #include <atomic.h>
  25 #include <sysdep.h>
  26
  27 #undef __cxa_atexit
  28
  29
  30 int
  31 attribute_hidden
  32 __internal_atexit (void (*func) (void *), void *arg, void *d,
  33                    struct exit_function_list **listp)
  34 {
  35   struct exit_function *new = __new_exitfn (listp);
  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
  51
  52 /* Register a function to be called by exit or when a shared library
  53    is unloaded.  This function is only called from code generated by
  54    the C++ compiler.  */
  55 int
  56 __cxa_atexit (void (*func) (void *), void *arg, void *d)
  57 {
  58   return __internal_atexit (func, arg, d, &__exit_funcs);
  59 }
  60 libc_hidden_def (__cxa_atexit)
  61
  62
  63 /* We change global data, so we need locking.  */
  64 __libc_lock_define_initialized (static, lock)
  65
  66
  67 static struct exit_function_list initial;
  68 struct exit_function_list *__exit_funcs = &initial;
  69 uint64_t __new_exitfn_called;
  70
  71 struct exit_function *
  72 __new_exitfn (struct exit_function_list **listp)
  73 {
  74   struct exit_function_list *p = NULL;
  75   struct exit_function_list *l;
  76   struct exit_function *r = NULL;
  77   size_t i = 0;
  78
  79   __libc_lock_lock (lock);
  80
  81   for (l = *listp; l != NULL; p = l, l = l->next)
  82     {
  83       for (i = l->idx; i > 0; --i)
  84         if (l->fns[i - 1].flavor != ef_free)
  85           break;
  86
  87       if (i > 0)
  88         break;
  89
  90       /* This block is completely unused.  */
  91       l->idx = 0;
  92     }
  93
  94   if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
  95     {
  96       /* The last entry in a block is used.  Use the first entry in
  97          the previous block if it exists.  Otherwise create a new one.  */
  98       if (p == NULL)
  99         {
 100           assert (l != NULL);
 101           p = (struct exit_function_list *)
 102             calloc (1, sizeof (struct exit_function_list));
 103           if (p != NULL)
 104             {
 105               p->next = *listp;
 106               *listp = p;
 107             }
 108         }
 109
 110       if (p != NULL)
 111         {
 112           r = &p->fns[0];
 113           p->idx = 1;
 114         }
 115     }
 116   else
 117     {
 118       /* There is more room in the block.  */
 119       r = &l->fns[i];
 120       l->idx = i + 1;
 121     }
 122
 123   /* Mark entry as used, but we don't know the flavor now.  */
 124   if (r != NULL)
 125     {
 126       r->flavor = ef_us;
 127       ++__new_exitfn_called;
 128     }
 129
 130   __libc_lock_unlock (lock);
 131
 132   return r;
 133 }