1// <thread> -*- C++ -*-
2
3// Copyright (C) 2008-2024 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#if __cplusplus > 202002L
46# include <format>
47#endif
48
49#include <bits/std_thread.h> // std::thread, get_id, yield
50#include <bits/this_thread_sleep.h> // std::this_thread::sleep_for, sleep_until
51
52#define __glibcxx_want_jthread
53#define __glibcxx_want_formatters
54#include <bits/version.h>
55
56namespace std _GLIBCXX_VISIBILITY(default)
57{
58_GLIBCXX_BEGIN_NAMESPACE_VERSION
59
60 /**
61 * @defgroup threads Threads
62 * @ingroup concurrency
63 * @since C++11
64 *
65 * Classes for thread support.
66 * @{
67 */
68
69 // std::thread is defined in <bits/std_thread.h>
70
71 /// @relates std::thread::id @{
72
73#if __cpp_lib_three_way_comparison
74 inline strong_ordering
75 operator<=>(thread::id __x, thread::id __y) noexcept
76 { return __x._M_thread <=> __y._M_thread; }
77#else
78 inline bool
79 operator!=(thread::id __x, thread::id __y) noexcept
80 { return !(__x == __y); }
81
82 inline bool
83 operator<(thread::id __x, thread::id __y) noexcept
84 {
85 // Pthreads doesn't define any way to do this, so we just have to
86 // assume native_handle_type is LessThanComparable.
87 return __x._M_thread < __y._M_thread;
88 }
89
90 inline bool
91 operator<=(thread::id __x, thread::id __y) noexcept
92 { return !(__y < __x); }
93
94 inline bool
95 operator>(thread::id __x, thread::id __y) noexcept
96 { return __y < __x; }
97
98 inline bool
99 operator>=(thread::id __x, thread::id __y) noexcept
100 { return !(__x < __y); }
101#endif // __cpp_lib_three_way_comparison
102
103 template<class _CharT, class _Traits>
104 inline basic_ostream<_CharT, _Traits>&
105 operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
106 {
107 if (__id == thread::id())
108 return __out << "thread::id of a non-executing thread";
109 else
110 return __out << __id._M_thread;
111 }
112 /// @}
113
114#ifdef __cpp_lib_jthread // C++ >= 20
115
116 /// @cond undocumented
117#ifndef __STRICT_ANSI__
118 template<typename _Callable, typename... _Args>
119 constexpr bool __pmf_expects_stop_token = false;
120
121 template<typename _Callable, typename _Obj, typename... _Args>
122 constexpr bool __pmf_expects_stop_token<_Callable, _Obj, _Args...>
123 = __and_<is_member_function_pointer<remove_reference_t<_Callable>>,
124 is_invocable<_Callable, _Obj, stop_token, _Args...>>::value;
125#endif
126 /// @endcond
127
128 /** A thread with cancellation and automatic joining.
129 *
130 * Unlike `std::thread`, destroying a joinable `std::jthread` will not
131 * terminate the process. Instead, it will try to request its thread to
132 * stop, then will join it.
133 *
134 * A `std::jthread` has a `std::stop_source` member which will be passed
135 * as the first argument to the callable that runs in the new thread
136 * (as long as the callable will accept that argument). That can then
137 * be used to send a stop request that the new thread can test for.
138 *
139 * @headerfile thread
140 * @since C++20
141 */
142 class jthread
143 {
144 public:
145 using id = thread::id;
146 using native_handle_type = thread::native_handle_type;
147
148 jthread() noexcept
149 : _M_stop_source{nostopstate}
150 { }
151
152 template<typename _Callable, typename... _Args,
153 typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
154 jthread>>>
155 explicit
156 jthread(_Callable&& __f, _Args&&... __args)
157 : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
158 std::forward<_Args>(__args)...)}
159 { }
160
161 jthread(const jthread&) = delete;
162 jthread(jthread&&) noexcept = default;
163
164 ~jthread()
165 {
166 if (joinable())
167 {
168 request_stop();
169 join();
170 }
171 }
172
173 jthread&
174 operator=(const jthread&) = delete;
175
176 jthread&
177 operator=(jthread&& __other) noexcept
178 {
179 std::jthread(std::move(__other)).swap(*this);
180 return *this;
181 }
182
183 void
184 swap(jthread& __other) noexcept
185 {
186 std::swap(_M_stop_source, __other._M_stop_source);
187 std::swap(_M_thread, __other._M_thread);
188 }
189
190 [[nodiscard]] bool
191 joinable() const noexcept
192 {
193 return _M_thread.joinable();
194 }
195
196 void
197 join()
198 {
199 _M_thread.join();
200 }
201
202 void
203 detach()
204 {
205 _M_thread.detach();
206 }
207
208 [[nodiscard]] id
209 get_id() const noexcept
210 {
211 return _M_thread.get_id();
212 }
213
214 [[nodiscard]] native_handle_type
215 native_handle()
216 {
217 return _M_thread.native_handle();
218 }
219
220 [[nodiscard]] static unsigned
221 hardware_concurrency() noexcept
222 {
223 return thread::hardware_concurrency();
224 }
225
226 [[nodiscard]] stop_source
227 get_stop_source() noexcept
228 {
229 return _M_stop_source;
230 }
231
232 [[nodiscard]] stop_token
233 get_stop_token() const noexcept
234 {
235 return _M_stop_source.get_token();
236 }
237
238 bool request_stop() noexcept
239 {
240 return _M_stop_source.request_stop();
241 }
242
243 friend void swap(jthread& __lhs, jthread& __rhs) noexcept
244 {
245 __lhs.swap(__rhs);
246 }
247
248 private:
249 template<typename _Callable, typename... _Args>
250 static thread
251 _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
252 {
253#ifndef __STRICT_ANSI__
254 if constexpr (__pmf_expects_stop_token<_Callable, _Args...>)
255 return _S_create_pmf(__ssrc, __f, std::forward<_Args>(__args)...);
256 else
257#endif
258 if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
259 decay_t<_Args>...>)
260 return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
261 std::forward<_Args>(__args)...};
262 else
263 {
264 static_assert(is_invocable_v<decay_t<_Callable>,
265 decay_t<_Args>...>,
266 "std::jthread arguments must be invocable after"
267 " conversion to rvalues");
268 return thread{std::forward<_Callable>(__f),
269 std::forward<_Args>(__args)...};
270 }
271 }
272
273#ifndef __STRICT_ANSI__
274 template<typename _Callable, typename _Obj, typename... _Args>
275 static thread
276 _S_create_pmf(stop_source& __ssrc, _Callable __f, _Obj&& __obj,
277 _Args&&... __args)
278 {
279 return thread{__f, std::forward<_Obj>(__obj), __ssrc.get_token(),
280 std::forward<_Args>(__args)...};
281 }
282#endif
283
284 stop_source _M_stop_source;
285 thread _M_thread;
286 };
287#endif // __cpp_lib_jthread
288
289#ifdef __cpp_lib_formatters // C++ >= 23
290
291 template<typename _CharT>
292 class formatter<thread::id, _CharT>
293 {
294 public:
295 constexpr typename basic_format_parse_context<_CharT>::iterator
296 parse(basic_format_parse_context<_CharT>& __pc)
297 {
298 __format::_Spec<_CharT> __spec{};
299 const auto __last = __pc.end();
300 auto __first = __pc.begin();
301
302 auto __finalize = [this, &__spec] {
303 _M_spec = __spec;
304 };
305
306 auto __finished = [&] {
307 if (__first == __last || *__first == '}')
308 {
309 __finalize();
310 return true;
311 }
312 return false;
313 };
314
315 if (__finished())
316 return __first;
317
318 __first = __spec._M_parse_fill_and_align(__first, __last);
319 if (__finished())
320 return __first;
321
322 __first = __spec._M_parse_width(__first, __last, __pc);
323 if (__finished())
324 return __first;
325
326 __throw_format_error("format error: invalid format-spec for "
327 "std::thread::id");
328 }
329
330 template<typename _Out>
331 typename basic_format_context<_Out, _CharT>::iterator
332 format(thread::id __id, basic_format_context<_Out, _CharT>& __fc) const
333 {
334 std::basic_ostringstream<_CharT> __os;
335 __os << __id;
336 auto __str = __os.view();
337 return __format::__write_padded_as_spec(__str, __str.size(),
338 __fc, _M_spec,
339 __format::_Align_right);
340 }
341
342 private:
343 __format::_Spec<_CharT> _M_spec;
344 };
345#endif // __cpp_lib_formatters
346
347 /// @} group threads
348
349_GLIBCXX_END_NAMESPACE_VERSION
350} // namespace
351#endif // C++11
352#endif // _GLIBCXX_THREAD
353