stdlib/cxa_atexit.c

   1 /* Copyright (C) 1999-2017 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 <sysdep.h>
  25
  26 #undef __cxa_atexit
  27
  28 /* See concurrency notes in stdlib/exit.h where this lock is declared.  */
  29 __libc_lock_define_initialized (, __exit_funcs_lock)
  30
  31
  32 int
  33 attribute_hidden
  34 __internal_atexit (void (*func) (void *), void *arg, void *d,
  35                    struct exit_function_list **listp)
  36 {
  37   struct exit_function *new;
  38
  39   __libc_lock_lock (__exit_funcs_lock);
  40   new = __new_exitfn (listp);
  41
  42   if (new == NULL)
  43     {
  44       __libc_lock_unlock (__exit_funcs_lock);
  45       return -1;
  46     }
  47
  48 #ifdef PTR_MANGLE
  49   PTR_MANGLE (func);
  50 #endif
  51   new->func.cxa.fn = (void (*) (void *, int)) func;
  52   new->func.cxa.arg = arg;
  53   new->func.cxa.dso_handle = d;
  54   new->flavor = ef_cxa;
  55   __libc_lock_unlock (__exit_funcs_lock);
  56   return 0;
  57 }
  58
  59
  60 /* Register a function to be called by exit or when a shared library
  61    is unloaded.  This function is only called from code generated by
  62    the C++ compiler.  */
  63 int
  64 __cxa_atexit (void (*func) (void *), void *arg, void *d)
  65 {
  66   return __internal_atexit (func, arg, d, &__exit_funcs);
  67 }
  68 libc_hidden_def (__cxa_atexit)
  69
  70
  71 static struct exit_function_list initial;
  72 struct exit_function_list *__exit_funcs = &initial;
  73 uint64_t __new_exitfn_called;
  74
  75 /* Must be called with __exit_funcs_lock held.  */
  76 struct exit_function *
  77 __new_exitfn (struct exit_function_list **listp)
  78 {
  79   struct exit_function_list *p = NULL;
  80   struct exit_function_list *l;
  81   struct exit_function *r = NULL;
  82   size_t i = 0;
  83
  84   if (__exit_funcs_done)
  85     /* Exit code is finished processing all registered exit functions,
  86        therefore we fail this registration.  */
  87     return NULL;
  88
  89   for (l = *listp; l != NULL; p = l, l = l->next)
  90     {
  91       for (i = l->idx; i > 0; --i)
  92         if (l->fns[i - 1].flavor != ef_free)
  93           break;
  94
  95       if (i > 0)
  96         break;
  97
  98       /* This block is completely unused.  */
  99       l->idx = 0;
 100     }
 101
 102   if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
 103     {
 104       /* The last entry in a block is used.  Use the first entry in
 105          the previous block if it exists.  Otherwise create a new one.  */
 106       if (p == NULL)
 107         {
 108           assert (l != NULL);
 109           p = (struct exit_function_list *)
 110             calloc (1, sizeof (struct exit_function_list));
 111           if (p != NULL)
 112             {
 113               p->next = *listp;
 114               *listp = p;
 115             }
 116         }
 117
 118       if (p != NULL)
 119         {
 120           r = &p->fns[0];
 121           p->idx = 1;
 122         }
 123     }
 124   else
 125     {
 126       /* There is more room in the block.  */
 127       r = &l->fns[i];
 128       l->idx = i + 1;
 129     }
 130
 131   /* Mark entry as used, but we don't know the flavor now.  */
 132   if (r != NULL)
 133     {
 134       r->flavor = ef_us;
 135       ++__new_exitfn_called;
 136     }
 137
 138   return r;
 139 }