1 // std::thread declarations -*- C++ -*-
2
3 // Copyright (C) 2008-2022 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 <iosfwd> // std::basic_ostream
39 #include <tuple> // std::tuple
40 #include <bits/functional_hash.h> // std::hash
41 #include <bits/invoke.h> // std::__invoke
42 #include <bits/refwrap.h> // not required, but helpful to users
43 #include <bits/unique_ptr.h> // std::unique_ptr
44
45 #ifdef _GLIBCXX_HAS_GTHREADS
46 # include <bits/gthr.h>
47 #else
48 # include <errno.h>
49 # include <bits/functexcept.h>
50 #endif
51
_GLIBCXX_VISIBILITY(default)52 namespace std _GLIBCXX_VISIBILITY(default)
53 {
54 _GLIBCXX_BEGIN_NAMESPACE_VERSION
55
56 /** @addtogroup threads
57 * @{
58 */
59
60 /** A std::thread represents a new thread of execution.
61 *
62 * The default constructor creates an object that does not own a thread.
63 * The `thread(F&&, Args&&...)` constructor invokes a callable in a new
64 * thread, and owns that new thread. A `std::thread` that owns a thread
65 * is *joinable*. Joining a thread waits for it to finish executing,
66 * which happens when the callable running in that thread returns.
67 *
68 * A `std::thread` cannot be copied, but can be moved. Moving a joinable
69 * object transfers ownership of its thread to another object.
70 *
71 * A joinable `std::thread` must be explicitly joined (or detached) before
72 * it is destroyed or assigned to. Attempting to destroy a joinable thread
73 * will terminate the whole process.
74 *
75 * @headerfile thread
76 * @since C++11
77 */
78 class thread
79 {
80 public:
81 #ifdef _GLIBCXX_HAS_GTHREADS
82 // Abstract base class for types that wrap arbitrary functors to be
83 // invoked in the new thread of execution.
84 struct _State
85 {
86 virtual ~_State();
87 virtual void _M_run() = 0;
88 };
89 using _State_ptr = unique_ptr<_State>;
90
91 using native_handle_type = __gthread_t;
92 #else
93 using native_handle_type = int;
94 #endif
95
96 /** A std::thread::id is a unique identifier for a thread.
97 *
98 * @headerfile thread
99 * @since C++11
100 */
101 class id
102 {
103 native_handle_type _M_thread;
104
105 public:
106 id() noexcept : _M_thread() { }
107
108 explicit
109 id(native_handle_type __id) : _M_thread(__id) { }
110
111 private:
112 friend class thread;
113 friend struct hash<id>;
114
115 friend bool
116 operator==(id __x, id __y) noexcept;
117
118 #if __cpp_lib_three_way_comparison
119 friend strong_ordering
120 operator<=>(id __x, id __y) noexcept;
121 #else
122 friend bool
123 operator<(id __x, id __y) noexcept;
124 #endif
125
126 template<class _CharT, class _Traits>
127 friend basic_ostream<_CharT, _Traits>&
128 operator<<(basic_ostream<_CharT, _Traits>& __out, id __id);
129 };
130
131 private:
132 id _M_id;
133
134 // _GLIBCXX_RESOLVE_LIB_DEFECTS
135 // 2097. packaged_task constructors should be constrained
136 // 3039. Unnecessary decay in thread and packaged_task
137 template<typename _Tp>
138 using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
139
140 public:
141 thread() noexcept = default;
142
143 #ifdef _GLIBCXX_HAS_GTHREADS
144 template<typename _Callable, typename... _Args,
145 typename = _Require<__not_same<_Callable>>>
146 explicit
147 thread(_Callable&& __f, _Args&&... __args)
148 {
149 static_assert( __is_invocable<typename decay<_Callable>::type,
150 typename decay<_Args>::type...>::value,
151 "std::thread arguments must be invocable after conversion to rvalues"
152 );
153
154 #ifdef GTHR_ACTIVE_PROXY
155 // Create a reference to pthread_create, not just the gthr weak symbol.
156 auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
157 #else
158 auto __depend = nullptr;
159 #endif
160 using _Wrapper = _Call_wrapper<_Callable, _Args...>;
161 // Create a call wrapper with DECAY_COPY(__f) as its target object
162 // and DECAY_COPY(__args)... as its bound argument entities.
163 _M_start_thread(_State_ptr(new _State_impl<_Wrapper>(
164 std::forward<_Callable>(__f), std::forward<_Args>(__args)...)),
165 __depend);
166 }
167 #endif // _GLIBCXX_HAS_GTHREADS
168
169 ~thread()
170 {
171 if (joinable())
172 std::__terminate();
173 }
174
175 thread(const thread&) = delete;
176
177 thread(thread&& __t) noexcept
178 { swap(__t); }
179
180 thread& operator=(const thread&) = delete;
181
182 thread& operator=(thread&& __t) noexcept
183 {
184 if (joinable())
185 std::__terminate();
186 swap(__t);
187 return *this;
188 }
189
190 void
191 swap(thread& __t) noexcept
192 { std::swap(_M_id, __t._M_id); }
193
194 bool
195 joinable() const noexcept
196 { return !(_M_id == id()); }
197
198 void
199 join();
200
201 void
202 detach();
203
204 id
205 get_id() const noexcept
206 { return _M_id; }
207
208 /** @pre thread is joinable
209 */
210 native_handle_type
211 native_handle()
212 { return _M_id._M_thread; }
213
214 // Returns a value that hints at the number of hardware thread contexts.
215 static unsigned int
216 hardware_concurrency() noexcept;
217
218 #ifdef _GLIBCXX_HAS_GTHREADS
219 private:
220 template<typename _Callable>
221 struct _State_impl : public _State
222 {
223 _Callable _M_func;
224
225 template<typename... _Args>
226 _State_impl(_Args&&... __args)
227 : _M_func(std::forward<_Args>(__args)...)
228 { }
229
230 void
231 _M_run() { _M_func(); }
232 };
233
234 void
235 _M_start_thread(_State_ptr, void (*)());
236
237 #if _GLIBCXX_THREAD_ABI_COMPAT
238 public:
239 struct _Impl_base;
240 typedef shared_ptr<_Impl_base> __shared_base_type;
241 struct _Impl_base
242 {
243 __shared_base_type _M_this_ptr;
244 virtual ~_Impl_base() = default;
245 virtual void _M_run() = 0;
246 };
247
248 private:
249 void
250 _M_start_thread(__shared_base_type, void (*)());
251
252 void
253 _M_start_thread(__shared_base_type);
254 #endif
255
256 private:
257 // A call wrapper that does INVOKE(forwarded tuple elements...)
258 template<typename _Tuple>
259 struct _Invoker
260 {
261 template<typename... _Args>
262 explicit
263 _Invoker(_Args&&... __args)
264 : _M_t(std::forward<_Args>(__args)...)
265 { }
266
267 _Tuple _M_t;
268
269 template<typename>
270 struct __result;
271 template<typename _Fn, typename... _Args>
272 struct __result<tuple<_Fn, _Args...>>
273 : __invoke_result<_Fn, _Args...>
274 { };
275
276 template<size_t... _Ind>
277 typename __result<_Tuple>::type
278 _M_invoke(_Index_tuple<_Ind...>)
279 { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
280
281 typename __result<_Tuple>::type
282 operator()()
283 {
284 using _Indices
285 = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
286 return _M_invoke(_Indices());
287 }
288 };
289
290 public:
291 /// @cond undocumented
292 template<typename... _Tp>
293 using _Call_wrapper = _Invoker<tuple<typename decay<_Tp>::type...>>;
294 /// @endcond
295 #endif // _GLIBCXX_HAS_GTHREADS
296 };
297
298 #ifndef _GLIBCXX_HAS_GTHREADS
299 inline void thread::join() { std::__throw_system_error(EINVAL); }
300 inline void thread::detach() { std::__throw_system_error(EINVAL); }
301 inline unsigned int thread::hardware_concurrency() noexcept { return 0; }
302 #endif
303
304 /// @relates std::thread
305 inline void
306 swap(thread& __x, thread& __y) noexcept
307 { __x.swap(__y); }
308
309 /// @relates std::thread::id
310 inline bool
311 operator==(thread::id __x, thread::id __y) noexcept
312 {
313 // pthread_equal is undefined if either thread ID is not valid, so we
314 // can't safely use __gthread_equal on default-constructed values (nor
315 // the non-zero value returned by this_thread::get_id() for
316 // single-threaded programs using GNU libc). Assume EqualityComparable.
317 return __x._M_thread == __y._M_thread;
318 }
319
320 // N.B. other comparison operators are defined in <thread>
321
322 // DR 889.
323 /// std::hash specialization for thread::id.
324 template<>
325 struct hash<thread::id>
326 : public __hash_base<size_t, thread::id>
327 {
328 size_t
329 operator()(const thread::id& __id) const noexcept
330 { return std::_Hash_impl::hash(__id._M_thread); }
331 };
332
333 namespace this_thread
334 {
335 /// The unique identifier of the current thread.
336 inline thread::id
337 get_id() noexcept
338 {
339 #ifndef _GLIBCXX_HAS_GTHREADS
340 return thread::id(1);
341 #elif defined _GLIBCXX_NATIVE_THREAD_ID
342 return thread::id(_GLIBCXX_NATIVE_THREAD_ID);
343 #else
344 return thread::id(__gthread_self());
345 #endif
346 }
347
348 /// Allow the implementation to schedule a different thread.
349 inline void
350 yield() noexcept
351 {
352 #if defined _GLIBCXX_HAS_GTHREADS && defined _GLIBCXX_USE_SCHED_YIELD
353 __gthread_yield();
354 #endif
355 }
356
357 } // namespace this_thread
358
359 /// @}
360
361 _GLIBCXX_END_NAMESPACE_VERSION
362 } // namespace
363 #endif // C++11
364
365 #endif // _GLIBCXX_THREAD_H
366