1 // mutex -*- C++ -*-
2 
3 // Copyright (C) 2008-2016 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 <mutex>
26 
27 #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
28 #ifndef _GLIBCXX_HAVE_TLS
29 namespace
30 {
31   inline std::unique_lock<std::mutex>*&
__get_once_functor_lock_ptr()32   __get_once_functor_lock_ptr()
33   {
34     static std::unique_lock<std::mutex>* __once_functor_lock_ptr = 0;
35     return __once_functor_lock_ptr;
36   }
37 }
38 #endif
39 
40 namespace std _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 
44 #ifdef _GLIBCXX_HAVE_TLS
45   __thread void* __once_callable;
46   __thread void (*__once_call)();
47 #else
48   // Explicit instantiation due to -fno-implicit-instantiation.
49   template class function<void()>;
50   function<void()> __once_functor;
51 
52   mutex&
53   __get_once_mutex()
54   {
55     static mutex once_mutex;
56     return once_mutex;
57   }
58 
59   // code linked against ABI 3.4.12 and later uses this
60   void
61   __set_once_functor_lock_ptr(unique_lock<mutex>* __ptr)
62   {
63     __get_once_functor_lock_ptr() = __ptr;
64   }
65 
66   // unsafe - retained for compatibility with ABI 3.4.11
67   unique_lock<mutex>&
68   __get_once_functor_lock()
69   {
70     static unique_lock<mutex> once_functor_lock(__get_once_mutex(), defer_lock);
71     return once_functor_lock;
72   }
73 #endif
74 
75   extern "C"
76   {
__once_proxy()77     void __once_proxy()
78     {
79 #ifndef _GLIBCXX_HAVE_TLS
80       function<void()> __once_call = std::move(__once_functor);
81       if (unique_lock<mutex>* __lock = __get_once_functor_lock_ptr())
82       {
83         // caller is using new ABI and provided lock ptr
84         __get_once_functor_lock_ptr() = 0;
85         __lock->unlock();
86       }
87       else
88         __get_once_functor_lock().unlock();  // global lock
89 #endif
90       __once_call();
91     }
92   }
93 
94 _GLIBCXX_END_NAMESPACE_VERSION
95 } // namespace std
96 
97 #endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
98