1// Support for pointer abstractions -*- C++ -*-
2
3// Copyright (C) 2011-2020 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25#include <memory>
26
27#include "mutex_pool.h"
28
29namespace __gnu_internal _GLIBCXX_VISIBILITY(hidden)
30{
31  /* Returns different instances of __mutex depending on the passed index
32   * in order to limit contention.
33   */
34  __gnu_cxx::__mutex&
35  get_mutex(unsigned char i)
36  {
37    // increase alignment to put each lock on a separate cache line
38    struct alignas(64) M : __gnu_cxx::__mutex { };
39    static M m[mask + 1];
40    return m[i];
41  }
42}
43
44namespace std _GLIBCXX_VISIBILITY(default)
45{
46_GLIBCXX_BEGIN_NAMESPACE_VERSION
47
48  bad_weak_ptr::~bad_weak_ptr() noexcept = default;
49
50  char const*
51  bad_weak_ptr::what() const noexcept
52  { return "bad_weak_ptr"; }
53
54#ifdef __GTHREADS
55  namespace
56  {
57    inline unsigned char key(const void* addr)
58    { return _Hash_impl::hash(addr) & __gnu_internal::mask; }
59  }
60
61  _Sp_locker::_Sp_locker(const void* p) noexcept
62  {
63    if (__gthread_active_p())
64      {
65	_M_key1 = _M_key2 = key(p);
66        __gnu_internal::get_mutex(_M_key1).lock();
67      }
68    else
69      _M_key1 = _M_key2 = __gnu_internal::invalid;
70  }
71
72  _Sp_locker::_Sp_locker(const void* p1, const void* p2) noexcept
73  {
74    if (__gthread_active_p())
75      {
76	_M_key1 = key(p1);
77	_M_key2 = key(p2);
78	if (_M_key2 < _M_key1)
79	  __gnu_internal::get_mutex(_M_key2).lock();
80	__gnu_internal::get_mutex(_M_key1).lock();
81	if (_M_key2 > _M_key1)
82	  __gnu_internal::get_mutex(_M_key2).lock();
83      }
84    else
85      _M_key1 = _M_key2 = __gnu_internal::invalid;
86  }
87
88  _Sp_locker::~_Sp_locker()
89  {
90    if (_M_key1 != __gnu_internal::invalid)
91      {
92	__gnu_internal::get_mutex(_M_key1).unlock();
93	if (_M_key2 != _M_key1)
94	  __gnu_internal::get_mutex(_M_key2).unlock();
95      }
96  }
97#endif
98
99  bool
100  _Sp_make_shared_tag::_S_eq(const type_info& ti) noexcept
101  {
102#if __cpp_rtti
103    return ti == typeid(_Sp_make_shared_tag);
104#else
105    // If libstdc++ itself is built with -fno-rtti then just assume that
106    // make_shared and allocate_shared will never be used with -frtti.
107    return false;
108#endif
109  }
110
111_GLIBCXX_END_NAMESPACE_VERSION
112} // namespace
113