aboutsummaryrefslogtreecommitdiff
path: root/stdlib/cxa_atexit.c
blob: 5a397789596139bd3b646f1ddf9c8adc118b39db (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
/* Copyright (C) 1999-2019 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <stdlib.h>
#include <stdint.h>

#include <libc-lock.h>
#include "exit.h"
#include <sysdep.h>

#undef __cxa_atexit

/* See concurrency notes in stdlib/exit.h where this lock is declared.  */
__libc_lock_define_initialized (, __exit_funcs_lock)


int
attribute_hidden
__internal_atexit (void (*func) (void *), void *arg, void *d,
		   struct exit_function_list **listp)
{
  struct exit_function *new;

  /* As a QoI issue we detect NULL early with an assertion instead
     of a SIGSEGV at program exit when the handler is run (bug 20544).  */
  assert (func != NULL);

  __libc_lock_lock (__exit_funcs_lock);
  new = __new_exitfn (listp);

  if (new == NULL)
    {
      __libc_lock_unlock (__exit_funcs_lock);
      return -1;
    }

#ifdef PTR_MANGLE
  PTR_MANGLE (func);
#endif
  new->func.cxa.fn = (void (*) (void *, int)) func;
  new->func.cxa.arg = arg;
  new->func.cxa.dso_handle = d;
  new->flavor = ef_cxa;
  __libc_lock_unlock (__exit_funcs_lock);
  return 0;
}


/* Register a function to be called by exit or when a shared library
   is unloaded.  This function is only called from code generated by
   the C++ compiler.  */
int
__cxa_atexit (void (*func) (void *), void *arg, void *d)
{
  return __internal_atexit (func, arg, d, &__exit_funcs);
}
libc_hidden_def (__cxa_atexit)


static struct exit_function_list initial;
struct exit_function_list *__exit_funcs = &initial;
uint64_t __new_exitfn_called;

/* Must be called with __exit_funcs_lock held.  */
struct exit_function *
__new_exitfn (struct exit_function_list **listp)
{
  struct exit_function_list *p = NULL;
  struct exit_function_list *l;
  struct exit_function *r = NULL;
  size_t i = 0;

  if (__exit_funcs_done)
    /* Exit code is finished processing all registered exit functions,
       therefore we fail this registration.  */
    return NULL;

  for (l = *listp; l != NULL; p = l, l = l->next)
    {
      for (i = l->idx; i > 0; --i)
	if (l->fns[i - 1].flavor != ef_free)
	  break;

      if (i > 0)
	break;

      /* This block is completely unused.  */
      l->idx = 0;
    }

  if (l == NULL || i == sizeof (l->fns) / sizeof (l->fns[0]))
    {
      /* The last entry in a block is used.  Use the first entry in
	 the previous block if it exists.  Otherwise create a new one.  */
      if (p == NULL)
	{
	  assert (l != NULL);
	  p = (struct exit_function_list *)
	    calloc (1, sizeof (struct exit_function_list));
	  if (p != NULL)
	    {
	      p->next = *listp;
	      *listp = p;
	    }
	}

      if (p != NULL)
	{
	  r = &p->fns[0];
	  p->idx = 1;
	}
    }
  else
    {
      /* There is more room in the block.  */
      r = &l->fns[i];
      l->idx = i + 1;
    }

  /* Mark entry as used, but we don't know the flavor now.  */
  if (r != NULL)
    {
      r->flavor = ef_us;
      ++__new_exitfn_called;
    }

  return r;
}