libstdc++
std_thread.h
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1 // std::thread declarations -*- C++ -*-
2 
3 // Copyright (C) 2008-2021 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 /** @file bits/std_thread.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{thread}
28  */
29 
30 #ifndef _GLIBCXX_THREAD_H
31 #define _GLIBCXX_THREAD_H 1
32 
33 #pragma GCC system_header
34 
35 #if __cplusplus >= 201103L
36 #include <bits/c++config.h>
37 
38 #include <exception> // std::terminate
39 #include <iosfwd> // std::basic_ostream
40 #include <tuple> // std::tuple
41 #include <bits/functional_hash.h> // std::hash
42 #include <bits/invoke.h> // std::__invoke
43 #include <bits/refwrap.h> // not required, but helpful to users
44 #include <bits/unique_ptr.h> // std::unique_ptr
45 
46 #ifdef _GLIBCXX_HAS_GTHREADS
47 # include <bits/gthr.h>
48 #else
49 # include <errno.h>
50 # include <bits/functexcept.h>
51 #endif
52 
53 namespace std _GLIBCXX_VISIBILITY(default)
54 {
55 _GLIBCXX_BEGIN_NAMESPACE_VERSION
56 
57  /** @addtogroup threads
58  * @{
59  */
60 
61  /// thread
62  class thread
63  {
64  public:
65 #ifdef _GLIBCXX_HAS_GTHREADS
66  // Abstract base class for types that wrap arbitrary functors to be
67  // invoked in the new thread of execution.
68  struct _State
69  {
70  virtual ~_State();
71  virtual void _M_run() = 0;
72  };
74 
75  using native_handle_type = __gthread_t;
76 #else
77  using native_handle_type = int;
78 #endif
79 
80  /// thread::id
81  class id
82  {
83  native_handle_type _M_thread;
84 
85  public:
86  id() noexcept : _M_thread() { }
87 
88  explicit
89  id(native_handle_type __id) : _M_thread(__id) { }
90 
91  private:
92  friend class thread;
93  friend struct hash<id>;
94 
95  friend bool
96  operator==(id __x, id __y) noexcept;
97 
98 #if __cpp_lib_three_way_comparison
99  friend strong_ordering
100  operator<=>(id __x, id __y) noexcept;
101 #else
102  friend bool
103  operator<(id __x, id __y) noexcept;
104 #endif
105 
106  template<class _CharT, class _Traits>
108  operator<<(basic_ostream<_CharT, _Traits>& __out, id __id);
109  };
110 
111  private:
112  id _M_id;
113 
114  // _GLIBCXX_RESOLVE_LIB_DEFECTS
115  // 2097. packaged_task constructors should be constrained
116  // 3039. Unnecessary decay in thread and packaged_task
117  template<typename _Tp>
118  using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
119 
120  public:
121  thread() noexcept = default;
122 
123 #ifdef _GLIBCXX_HAS_GTHREADS
124  template<typename _Callable, typename... _Args,
125  typename = _Require<__not_same<_Callable>>>
126  explicit
127  thread(_Callable&& __f, _Args&&... __args)
128  {
129  static_assert( __is_invocable<typename decay<_Callable>::type,
130  typename decay<_Args>::type...>::value,
131  "std::thread arguments must be invocable after conversion to rvalues"
132  );
133 
134 #ifdef GTHR_ACTIVE_PROXY
135  // Create a reference to pthread_create, not just the gthr weak symbol.
136  auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
137 #else
138  auto __depend = nullptr;
139 #endif
140  using _Wrapper = _Call_wrapper<_Callable, _Args...>;
141  // Create a call wrapper with DECAY_COPY(__f) as its target object
142  // and DECAY_COPY(__args)... as its bound argument entities.
143  _M_start_thread(_State_ptr(new _State_impl<_Wrapper>(
144  std::forward<_Callable>(__f), std::forward<_Args>(__args)...)),
145  __depend);
146  }
147 #endif // _GLIBCXX_HAS_GTHREADS
148 
149  ~thread()
150  {
151  if (joinable())
152  std::terminate();
153  }
154 
155  thread(const thread&) = delete;
156 
157  thread(thread&& __t) noexcept
158  { swap(__t); }
159 
160  thread& operator=(const thread&) = delete;
161 
162  thread& operator=(thread&& __t) noexcept
163  {
164  if (joinable())
165  std::terminate();
166  swap(__t);
167  return *this;
168  }
169 
170  void
171  swap(thread& __t) noexcept
172  { std::swap(_M_id, __t._M_id); }
173 
174  bool
175  joinable() const noexcept
176  { return !(_M_id == id()); }
177 
178  void
179  join();
180 
181  void
182  detach();
183 
184  id
185  get_id() const noexcept
186  { return _M_id; }
187 
188  /** @pre thread is joinable
189  */
190  native_handle_type
192  { return _M_id._M_thread; }
193 
194  // Returns a value that hints at the number of hardware thread contexts.
195  static unsigned int
196  hardware_concurrency() noexcept;
197 
198 #ifdef _GLIBCXX_HAS_GTHREADS
199  private:
200  template<typename _Callable>
201  struct _State_impl : public _State
202  {
203  _Callable _M_func;
204 
205  template<typename... _Args>
206  _State_impl(_Args&&... __args)
207  : _M_func{{std::forward<_Args>(__args)...}}
208  { }
209 
210  void
211  _M_run() { _M_func(); }
212  };
213 
214  void
215  _M_start_thread(_State_ptr, void (*)());
216 
217 #if _GLIBCXX_THREAD_ABI_COMPAT
218  public:
219  struct _Impl_base;
220  typedef shared_ptr<_Impl_base> __shared_base_type;
221  struct _Impl_base
222  {
223  __shared_base_type _M_this_ptr;
224  virtual ~_Impl_base() = default;
225  virtual void _M_run() = 0;
226  };
227 
228  private:
229  void
230  _M_start_thread(__shared_base_type, void (*)());
231 
232  void
233  _M_start_thread(__shared_base_type);
234 #endif
235 
236  private:
237  // A call wrapper that does INVOKE(forwarded tuple elements...)
238  template<typename _Tuple>
239  struct _Invoker
240  {
241  _Tuple _M_t;
242 
243  template<typename>
244  struct __result;
245  template<typename _Fn, typename... _Args>
246  struct __result<tuple<_Fn, _Args...>>
247  : __invoke_result<_Fn, _Args...>
248  { };
249 
250  template<size_t... _Ind>
251  typename __result<_Tuple>::type
252  _M_invoke(_Index_tuple<_Ind...>)
253  { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
254 
255  typename __result<_Tuple>::type
256  operator()()
257  {
258  using _Indices
259  = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
260  return _M_invoke(_Indices());
261  }
262  };
263 
264  public:
265  template<typename... _Tp>
266  using _Call_wrapper = _Invoker<tuple<typename decay<_Tp>::type...>>;
267 #endif // _GLIBCXX_HAS_GTHREADS
268  };
269 
270 #ifndef _GLIBCXX_HAS_GTHREADS
271  inline void thread::join() { std::__throw_system_error(EINVAL); }
272  inline void thread::detach() { std::__throw_system_error(EINVAL); }
273  inline unsigned int thread::hardware_concurrency() { return 0; }
274 #endif
275 
276  inline void
277  swap(thread& __x, thread& __y) noexcept
278  { __x.swap(__y); }
279 
280  inline bool
281  operator==(thread::id __x, thread::id __y) noexcept
282  {
283  // pthread_equal is undefined if either thread ID is not valid, so we
284  // can't safely use __gthread_equal on default-constructed values (nor
285  // the non-zero value returned by this_thread::get_id() for
286  // single-threaded programs using GNU libc). Assume EqualityComparable.
287  return __x._M_thread == __y._M_thread;
288  }
289 
290  // N.B. other comparison operators are defined in <thread>
291 
292  // DR 889.
293  /// std::hash specialization for thread::id.
294  template<>
295  struct hash<thread::id>
296  : public __hash_base<size_t, thread::id>
297  {
298  size_t
299  operator()(const thread::id& __id) const noexcept
300  { return std::_Hash_impl::hash(__id._M_thread); }
301  };
302 
303  namespace this_thread
304  {
305  /// this_thread::get_id
306  inline thread::id
307  get_id() noexcept
308  {
309 #ifndef _GLIBCXX_HAS_GTHREADS
310  return thread::id(1);
311 #elif defined _GLIBCXX_NATIVE_THREAD_ID
312  return thread::id(_GLIBCXX_NATIVE_THREAD_ID);
313 #else
314  return thread::id(__gthread_self());
315 #endif
316  }
317 
318  /// this_thread::yield
319  inline void
320  yield() noexcept
321  {
322 #if defined _GLIBCXX_HAS_GTHREADS && defined _GLIBCXX_USE_SCHED_YIELD
323  __gthread_yield();
324 #endif
325  }
326 
327  } // namespace this_thread
328 
329  /// @}
330 
331 _GLIBCXX_END_NAMESPACE_VERSION
332 } // namespace
333 #endif // C++11
334 
335 #endif // _GLIBCXX_THREAD_H
auto_ptr & operator=(auto_ptr &__a)
auto_ptr assignment operator.
Definition: auto_ptr.h:47
bool operator==(const error_code &__lhs, const error_code &__rhs) noexcept
Create an error_condition representing a standard errc condition.
Definition: system_error:344
constexpr __invoke_result< _Callable, _Args... >::type __invoke(_Callable &&__fn, _Args &&... __args) noexcept(__is_nothrow_invocable< _Callable, _Args... >::value)
Invoke a callable object.
Definition: invoke.h:90
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:101
void swap(any &__x, any &__y) noexcept
Exchange the states of two any objects.
Definition: any:412
void terminate() noexcept
void swap(shared_lock< _Mutex > &__x, shared_lock< _Mutex > &__y) noexcept
Swap specialization for shared_lock.
Definition: shared_mutex:851
ISO C++ entities toplevel namespace is std.
void yield() noexcept
this_thread::yield
Definition: std_thread.h:320
thread::id get_id() noexcept
this_thread::get_id
Definition: std_thread.h:307
Template class basic_ostream.
Definition: ostream:59
Primary class template hash.
thread
Definition: std_thread.h:63
native_handle_type native_handle()
Definition: std_thread.h:191
thread::id
Definition: std_thread.h:82
20.7.1.2 unique_ptr for single objects.
Definition: unique_ptr.h:243