1 // std::thread declarations -*- C++ -*-
2
3 // Copyright (C) 2008-2023 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
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 using native_handle_type = __gthread_t;
83 #else
84 using native_handle_type = int;
85 #endif
86
87 /** A std::thread::id is a unique identifier for a thread.
88 *
89 * @headerfile thread
90 * @since C++11
91 */
92 class id
93 {
94 native_handle_type _M_thread;
95
96 public:
97 id() noexcept : _M_thread() { }
98
99 explicit
100 id(native_handle_type __id) : _M_thread(__id) { }
101
102 private:
103 friend class thread;
104 friend struct hash<id>;
105
106 friend bool
107 operator==(id __x, id __y) noexcept;
108
109 #if __cpp_lib_three_way_comparison
110 friend strong_ordering
111 operator<=>(id __x, id __y) noexcept;
112 #else
113 friend bool
114 operator<(id __x, id __y) noexcept;
115 #endif
116
117 template<class _CharT, class _Traits>
118 friend basic_ostream<_CharT, _Traits>&
119 operator<<(basic_ostream<_CharT, _Traits>& __out, id __id);
120 };
121
122 private:
123 id _M_id;
124
125 // _GLIBCXX_RESOLVE_LIB_DEFECTS
126 // 2097. packaged_task constructors should be constrained
127 // 3039. Unnecessary decay in thread and packaged_task
128 template<typename _Tp>
129 using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
130
131 public:
132 thread() noexcept = default;
133
134 #ifdef _GLIBCXX_HAS_GTHREADS
135 private:
136 // This adds to user code that creates std:thread objects (because
137 // it is called by the template ctor below) strong references to
138 // pthread_create and pthread_join, which ensures they are both
139 // linked in even during static linking. We can't depend on
140 // gthread calls to bring them in, because those may use weak
141 // references.
142 static void
143 _M_thread_deps_never_run() {
144 #ifdef GTHR_ACTIVE_PROXY
145 reinterpret_cast<void (*)(void)>(&pthread_create)();
146 reinterpret_cast<void (*)(void)>(&pthread_join)();
147 #endif
148 }
149
150 public:
151 template<typename _Callable, typename... _Args,
152 typename = _Require<__not_same<_Callable>>>
153 explicit
154 thread(_Callable&& __f, _Args&&... __args)
155 {
156 static_assert( __is_invocable<typename decay<_Callable>::type,
157 typename decay<_Args>::type...>::value,
158 "std::thread arguments must be invocable after conversion to rvalues"
159 );
160
161 using _Wrapper = _Call_wrapper<_Callable, _Args...>;
162 // Create a call wrapper with DECAY_COPY(__f) as its target object
163 // and DECAY_COPY(__args)... as its bound argument entities.
164 _M_start_thread(_State_ptr(new _State_impl<_Wrapper>(
165 std::forward<_Callable>(__f), std::forward<_Args>(__args)...)),
166 _M_thread_deps_never_run);
167 }
168 #endif // _GLIBCXX_HAS_GTHREADS
169
170 ~thread()
171 {
172 if (joinable())
173 std::__terminate();
174 }
175
176 thread(const thread&) = delete;
177
178 thread(thread&& __t) noexcept
179 { swap(__t); }
180
181 thread& operator=(const thread&) = delete;
182
183 thread& operator=(thread&& __t) noexcept
184 {
185 if (joinable())
186 std::__terminate();
187 swap(__t);
188 return *this;
189 }
190
191 void
192 swap(thread& __t) noexcept
193 { std::swap(_M_id, __t._M_id); }
194
195 bool
196 joinable() const noexcept
197 { return !(_M_id == id()); }
198
199 void
200 join();
201
202 void
203 detach();
204
205 id
206 get_id() const noexcept
207 { return _M_id; }
208
209 /** @pre thread is joinable
210 */
211 native_handle_type
212 native_handle()
213 { return _M_id._M_thread; }
214
215 // Returns a value that hints at the number of hardware thread contexts.
216 static unsigned int
217 hardware_concurrency() noexcept;
218
219 #ifdef _GLIBCXX_HAS_GTHREADS
220 #ifndef _GLIBCXX_THREAD_IMPL
221 private:
222 #endif
223 // Abstract base class for types that wrap arbitrary functors to be
224 // invoked in the new thread of execution.
225 struct _State
226 {
227 virtual ~_State();
228 virtual void _M_run() = 0;
229 };
230 using _State_ptr = unique_ptr<_State>;
231
232 private:
233 template<typename _Callable>
234 struct _State_impl : public _State
235 {
236 _Callable _M_func;
237
238 template<typename... _Args>
239 _State_impl(_Args&&... __args)
240 : _M_func(std::forward<_Args>(__args)...)
241 { }
242
243 void
244 _M_run() { _M_func(); }
245 };
246
247 void
248 _M_start_thread(_State_ptr, void (*)());
249
250 #if _GLIBCXX_THREAD_ABI_COMPAT
251 public:
252 struct _Impl_base;
253 typedef shared_ptr<_Impl_base> __shared_base_type;
254 struct _Impl_base
255 {
256 __shared_base_type _M_this_ptr;
257 virtual ~_Impl_base() = default;
258 virtual void _M_run() = 0;
259 };
260
261 private:
262 void
263 _M_start_thread(__shared_base_type, void (*)());
264
265 void
266 _M_start_thread(__shared_base_type);
267 #endif
268
269 private:
270 // A call wrapper that does INVOKE(forwarded tuple elements...)
271 template<typename _Tuple>
272 struct _Invoker
273 {
274 template<typename... _Args>
275 explicit
276 _Invoker(_Args&&... __args)
277 : _M_t(std::forward<_Args>(__args)...)
278 { }
279
280 _Tuple _M_t;
281
282 template<typename>
283 struct __result;
284 template<typename _Fn, typename... _Args>
285 struct __result<tuple<_Fn, _Args...>>
286 : __invoke_result<_Fn, _Args...>
287 { };
288
289 template<size_t... _Ind>
290 typename __result<_Tuple>::type
291 _M_invoke(_Index_tuple<_Ind...>)
292 { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
293
294 typename __result<_Tuple>::type
295 operator()()
296 {
297 using _Indices
298 = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
299 return _M_invoke(_Indices());
300 }
301 };
302
303 public:
304 /// @cond undocumented
305 template<typename... _Tp>
306 using _Call_wrapper = _Invoker<tuple<typename decay<_Tp>::type...>>;
307 /// @endcond
308 #endif // _GLIBCXX_HAS_GTHREADS
309 };
310
311 #ifndef _GLIBCXX_HAS_GTHREADS
312 inline void thread::join() { std::__throw_system_error(EINVAL); }
313 inline void thread::detach() { std::__throw_system_error(EINVAL); }
314 inline unsigned int thread::hardware_concurrency() noexcept { return 0; }
315 #endif
316
317 /// @relates std::thread
318 inline void
319 swap(thread& __x, thread& __y) noexcept
320 { __x.swap(__y); }
321
322 /// @relates std::thread::id
323 inline bool
324 operator==(thread::id __x, thread::id __y) noexcept
325 {
326 // pthread_equal is undefined if either thread ID is not valid, so we
327 // can't safely use __gthread_equal on default-constructed values (nor
328 // the non-zero value returned by this_thread::get_id() for
329 // single-threaded programs using GNU libc). Assume EqualityComparable.
330 return __x._M_thread == __y._M_thread;
331 }
332
333 // N.B. other comparison operators are defined in <thread>
334
335 // DR 889.
336 /// std::hash specialization for thread::id.
337 template<>
338 struct hash<thread::id>
339 : public __hash_base<size_t, thread::id>
340 {
341 size_t
342 operator()(const thread::id& __id) const noexcept
343 { return std::_Hash_impl::hash(__id._M_thread); }
344 };
345
346 namespace this_thread
347 {
348 /// The unique identifier of the current thread.
349 inline thread::id
350 get_id() noexcept
351 {
352 #ifndef _GLIBCXX_HAS_GTHREADS
353 return thread::id(1);
354 #elif defined _GLIBCXX_NATIVE_THREAD_ID
355 return thread::id(_GLIBCXX_NATIVE_THREAD_ID);
356 #else
357 return thread::id(__gthread_self());
358 #endif
359 }
360
361 /// Allow the implementation to schedule a different thread.
362 inline void
363 yield() noexcept
364 {
365 #if defined _GLIBCXX_HAS_GTHREADS && defined _GLIBCXX_USE_SCHED_YIELD
366 __gthread_yield();
367 #endif
368 }
369
370 } // namespace this_thread
371
372 /// @}
373
374 _GLIBCXX_END_NAMESPACE_VERSION
375 } // namespace
376 #endif // C++11
377
378 #endif // _GLIBCXX_THREAD_H