1// <thread> -*- 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 include/thread
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_THREAD
30#define _GLIBCXX_THREAD 1
31
32#pragma GCC system_header
33
34#include <bits/requires_hosted.h> // concurrency
35
36#if __cplusplus < 201103L
37# include <bits/c++0x_warning.h>
38#else
39
40#if __cplusplus > 201703L
41# include <compare> // std::strong_ordering
42# include <stop_token> // std::stop_source, std::stop_token, std::nostopstate
43#endif
44
45#include <bits/std_thread.h> // std::thread, get_id, yield
46#include <bits/this_thread_sleep.h> // std::this_thread::sleep_for, sleep_until
47
48namespace std _GLIBCXX_VISIBILITY(default)
49{
50_GLIBCXX_BEGIN_NAMESPACE_VERSION
51
52 /**
53 * @defgroup threads Threads
54 * @ingroup concurrency
55 * @since C++11
56 *
57 * Classes for thread support.
58 * @{
59 */
60
61 // std::thread is defined in <bits/std_thread.h>
62
63 /// @relates std::thread::id @{
64
65#if __cpp_lib_three_way_comparison
66 inline strong_ordering
67 operator<=>(thread::id __x, thread::id __y) noexcept
68 { return __x._M_thread <=> __y._M_thread; }
69#else
70 inline bool
71 operator!=(thread::id __x, thread::id __y) noexcept
72 { return !(__x == __y); }
73
74 inline bool
75 operator<(thread::id __x, thread::id __y) noexcept
76 {
77 // Pthreads doesn't define any way to do this, so we just have to
78 // assume native_handle_type is LessThanComparable.
79 return __x._M_thread < __y._M_thread;
80 }
81
82 inline bool
83 operator<=(thread::id __x, thread::id __y) noexcept
84 { return !(__y < __x); }
85
86 inline bool
87 operator>(thread::id __x, thread::id __y) noexcept
88 { return __y < __x; }
89
90 inline bool
91 operator>=(thread::id __x, thread::id __y) noexcept
92 { return !(__x < __y); }
93#endif // __cpp_lib_three_way_comparison
94
95 template<class _CharT, class _Traits>
96 inline basic_ostream<_CharT, _Traits>&
97 operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
98 {
99 if (__id == thread::id())
100 return __out << "thread::id of a non-executing thread";
101 else
102 return __out << __id._M_thread;
103 }
104 /// @}
105
106#ifdef __cpp_lib_jthread
107
108 /// @cond undocumented
109#ifndef __STRICT_ANSI__
110 template<typename _Callable, typename... _Args>
111 constexpr bool __pmf_expects_stop_token = false;
112
113 template<typename _Callable, typename _Obj, typename... _Args>
114 constexpr bool __pmf_expects_stop_token<_Callable, _Obj, _Args...>
115 = __and_<is_member_function_pointer<remove_reference_t<_Callable>>,
116 is_invocable<_Callable, _Obj, stop_token, _Args...>>::value;
117#endif
118 /// @endcond
119
120 /** A thread with cancellation and automatic joining.
121 *
122 * Unlike `std::thread`, destroying a joinable `std::jthread` will not
123 * terminate the process. Instead, it will try to request its thread to
124 * stop, then will join it.
125 *
126 * A `std::jthread` has a `std::stop_source` member which will be passed
127 * as the first argument to the callable that runs in the new thread
128 * (as long as the callable will accept that argument). That can then
129 * be used to send a stop request that the new thread can test for.
130 *
131 * @headerfile thread
132 * @since C++20
133 */
134 class jthread
135 {
136 public:
137 using id = thread::id;
138 using native_handle_type = thread::native_handle_type;
139
140 jthread() noexcept
141 : _M_stop_source{nostopstate}
142 { }
143
144 template<typename _Callable, typename... _Args,
145 typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
146 jthread>>>
147 explicit
148 jthread(_Callable&& __f, _Args&&... __args)
149 : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
150 std::forward<_Args>(__args)...)}
151 { }
152
153 jthread(const jthread&) = delete;
154 jthread(jthread&&) noexcept = default;
155
156 ~jthread()
157 {
158 if (joinable())
159 {
160 request_stop();
161 join();
162 }
163 }
164
165 jthread&
166 operator=(const jthread&) = delete;
167
168 jthread&
169 operator=(jthread&& __other) noexcept
170 {
171 std::jthread(std::move(__other)).swap(*this);
172 return *this;
173 }
174
175 void
176 swap(jthread& __other) noexcept
177 {
178 std::swap(_M_stop_source, __other._M_stop_source);
179 std::swap(_M_thread, __other._M_thread);
180 }
181
182 [[nodiscard]] bool
183 joinable() const noexcept
184 {
185 return _M_thread.joinable();
186 }
187
188 void
189 join()
190 {
191 _M_thread.join();
192 }
193
194 void
195 detach()
196 {
197 _M_thread.detach();
198 }
199
200 [[nodiscard]] id
201 get_id() const noexcept
202 {
203 return _M_thread.get_id();
204 }
205
206 [[nodiscard]] native_handle_type
207 native_handle()
208 {
209 return _M_thread.native_handle();
210 }
211
212 [[nodiscard]] static unsigned
213 hardware_concurrency() noexcept
214 {
215 return thread::hardware_concurrency();
216 }
217
218 [[nodiscard]] stop_source
219 get_stop_source() noexcept
220 {
221 return _M_stop_source;
222 }
223
224 [[nodiscard]] stop_token
225 get_stop_token() const noexcept
226 {
227 return _M_stop_source.get_token();
228 }
229
230 bool request_stop() noexcept
231 {
232 return _M_stop_source.request_stop();
233 }
234
235 friend void swap(jthread& __lhs, jthread& __rhs) noexcept
236 {
237 __lhs.swap(__rhs);
238 }
239
240 private:
241 template<typename _Callable, typename... _Args>
242 static thread
243 _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
244 {
245#ifndef __STRICT_ANSI__
246 if constexpr (__pmf_expects_stop_token<_Callable, _Args...>)
247 return _S_create_pmf(__ssrc, __f, std::forward<_Args>(__args)...);
248 else
249#endif
250 if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
251 decay_t<_Args>...>)
252 return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
253 std::forward<_Args>(__args)...};
254 else
255 {
256 static_assert(is_invocable_v<decay_t<_Callable>,
257 decay_t<_Args>...>,
258 "std::jthread arguments must be invocable after"
259 " conversion to rvalues");
260 return thread{std::forward<_Callable>(__f),
261 std::forward<_Args>(__args)...};
262 }
263 }
264
265#ifndef __STRICT_ANSI__
266 template<typename _Callable, typename _Obj, typename... _Args>
267 static thread
268 _S_create_pmf(stop_source& __ssrc, _Callable __f, _Obj&& __obj,
269 _Args&&... __args)
270 {
271 return thread{__f, std::forward<_Obj>(__obj), __ssrc.get_token(),
272 std::forward<_Args>(__args)...};
273 }
274#endif
275
276 stop_source _M_stop_source;
277 thread _M_thread;
278 };
279#endif // __cpp_lib_jthread
280
281 /// @} group threads
282
283_GLIBCXX_END_NAMESPACE_VERSION
284} // namespace
285#endif // C++11
286#endif // _GLIBCXX_THREAD
287

source code of include/c++/13/thread