libstdc++
thread
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1// <thread> -*- C++ -*-
2
3// Copyright (C) 2008-2025 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#ifdef _GLIBCXX_SYSHDR
33#pragma GCC system_header
34#endif
35
36#include <bits/requires_hosted.h> // concurrency
37
38#if __cplusplus < 201103L
39# include <bits/c++0x_warning.h>
40#else
41
42#if __cplusplus > 201703L
43# include <compare> // std::strong_ordering
44# include <stop_token> // std::stop_source, std::stop_token, std::nostopstate
45#endif
46
47#include <bits/std_thread.h> // std::thread, get_id, yield
48#include <bits/this_thread_sleep.h> // std::this_thread::sleep_for, sleep_until
49
50#define __glibcxx_want_jthread
51#define __glibcxx_want_formatters
52#include <bits/version.h>
53
54#if __cpp_lib_formatters
55# include <format>
56#endif
57
58namespace std _GLIBCXX_VISIBILITY(default)
59{
60_GLIBCXX_BEGIN_NAMESPACE_VERSION
61
62 /**
63 * @defgroup threads Threads
64 * @ingroup concurrency
65 * @since C++11
66 *
67 * Classes for thread support.
68 * @{
69 */
70
71 // std::thread is defined in <bits/std_thread.h>
72
73 /// @relates std::thread::id @{
74
75#if __cpp_lib_three_way_comparison
76 inline strong_ordering
77 operator<=>(thread::id __x, thread::id __y) noexcept
78 { return __x._M_thread <=> __y._M_thread; }
79#else
80 inline bool
81 operator!=(thread::id __x, thread::id __y) noexcept
82 { return !(__x == __y); }
83
84 inline bool
85 operator<(thread::id __x, thread::id __y) noexcept
86 {
87 // Pthreads doesn't define any way to do this, so we just have to
88 // assume native_handle_type is LessThanComparable.
89 return __x._M_thread < __y._M_thread;
90 }
91
92 inline bool
93 operator<=(thread::id __x, thread::id __y) noexcept
94 { return !(__y < __x); }
95
96 inline bool
97 operator>(thread::id __x, thread::id __y) noexcept
98 { return __y < __x; }
99
100 inline bool
101 operator>=(thread::id __x, thread::id __y) noexcept
102 { return !(__x < __y); }
103#endif // __cpp_lib_three_way_comparison
104
105 template<class _CharT, class _Traits>
106 inline basic_ostream<_CharT, _Traits>&
107 operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
108 {
109 // Convert non-void pointers to const void* for formatted output.
110 using __output_type
111 = __conditional_t<is_pointer<thread::native_handle_type>::value,
112 const void*,
113 thread::native_handle_type>;
114
115 if (__id == thread::id())
116 return __out << "thread::id of a non-executing thread";
117 else
118 return __out << static_cast<__output_type>(__id._M_thread);
119 }
120 /// @}
121
122#ifdef __cpp_lib_jthread // C++ >= 20
123
124 /// @cond undocumented
125#ifndef __STRICT_ANSI__
126 template<typename _Callable, typename... _Args>
127 constexpr bool __pmf_expects_stop_token = false;
128
129 template<typename _Callable, typename _Obj, typename... _Args>
130 constexpr bool __pmf_expects_stop_token<_Callable, _Obj, _Args...>
131 = __and_<is_member_function_pointer<remove_reference_t<_Callable>>,
132 is_invocable<_Callable, _Obj, stop_token, _Args...>>::value;
133#endif
134 /// @endcond
135
136 /** A thread with cancellation and automatic joining.
137 *
138 * Unlike `std::thread`, destroying a joinable `std::jthread` will not
139 * terminate the process. Instead, it will try to request its thread to
140 * stop, then will join it.
141 *
142 * A `std::jthread` has a `std::stop_source` member which will be passed
143 * as the first argument to the callable that runs in the new thread
144 * (as long as the callable will accept that argument). That can then
145 * be used to send a stop request that the new thread can test for.
146 *
147 * @headerfile thread
148 * @since C++20
149 */
150 class jthread
151 {
152 public:
153 using id = thread::id;
154 using native_handle_type = thread::native_handle_type;
155
156 jthread() noexcept
157 : _M_stop_source{nostopstate}
158 { }
159
160 template<typename _Callable, typename... _Args,
161 typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
162 jthread>>>
163 explicit
164 jthread(_Callable&& __f, _Args&&... __args)
165 : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
166 std::forward<_Args>(__args)...)}
167 { }
168
169 jthread(const jthread&) = delete;
170 jthread(jthread&&) noexcept = default;
171
172 ~jthread()
173 {
174 if (joinable())
175 {
176 request_stop();
177 join();
178 }
179 }
180
181 jthread&
182 operator=(const jthread&) = delete;
183
184 jthread&
185 operator=(jthread&& __other) noexcept
186 {
187 std::jthread(std::move(__other)).swap(*this);
188 return *this;
189 }
190
191 void
192 swap(jthread& __other) noexcept
193 {
194 std::swap(_M_stop_source, __other._M_stop_source);
195 std::swap(_M_thread, __other._M_thread);
196 }
197
198 [[nodiscard]] bool
199 joinable() const noexcept
200 {
201 return _M_thread.joinable();
202 }
203
204 void
205 join()
206 {
207 _M_thread.join();
208 }
209
210 void
211 detach()
212 {
213 _M_thread.detach();
214 }
215
216 [[nodiscard]] id
217 get_id() const noexcept
218 {
219 return _M_thread.get_id();
220 }
221
222 [[nodiscard]] native_handle_type
223 native_handle()
224 {
225 return _M_thread.native_handle();
226 }
227
228 [[nodiscard]] static unsigned
229 hardware_concurrency() noexcept
230 {
231 return thread::hardware_concurrency();
232 }
233
234 [[nodiscard]] stop_source
235 get_stop_source() noexcept
236 {
237 return _M_stop_source;
238 }
239
240 [[nodiscard]] stop_token
241 get_stop_token() const noexcept
242 {
243 return _M_stop_source.get_token();
244 }
245
246 bool request_stop() noexcept
247 {
248 return _M_stop_source.request_stop();
249 }
250
251 friend void swap(jthread& __lhs, jthread& __rhs) noexcept
252 {
253 __lhs.swap(__rhs);
254 }
255
256 private:
257 template<typename _Callable, typename... _Args>
258 static thread
259 _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
260 {
261#ifndef __STRICT_ANSI__
262 if constexpr (__pmf_expects_stop_token<_Callable, _Args...>)
263 return _S_create_pmf(__ssrc, __f, std::forward<_Args>(__args)...);
264 else
265#endif
266 if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
267 decay_t<_Args>...>)
268 return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
269 std::forward<_Args>(__args)...};
270 else
271 {
272 static_assert(is_invocable_v<decay_t<_Callable>,
273 decay_t<_Args>...>,
274 "std::jthread arguments must be invocable after"
275 " conversion to rvalues");
276 return thread{std::forward<_Callable>(__f),
277 std::forward<_Args>(__args)...};
278 }
279 }
280
281#ifndef __STRICT_ANSI__
282 template<typename _Callable, typename _Obj, typename... _Args>
283 static thread
284 _S_create_pmf(stop_source& __ssrc, _Callable __f, _Obj&& __obj,
285 _Args&&... __args)
286 {
287 return thread{__f, std::forward<_Obj>(__obj), __ssrc.get_token(),
288 std::forward<_Args>(__args)...};
289 }
290#endif
291
292 stop_source _M_stop_source;
293 thread _M_thread;
294 };
295#endif // __cpp_lib_jthread
296
297#ifdef __cpp_lib_formatters // C++ >= 23
298 template<typename _CharT>
299 requires is_pointer_v<thread::native_handle_type>
300 || is_integral_v<thread::native_handle_type>
301 class formatter<thread::id, _CharT>
302 {
303 public:
304 constexpr typename basic_format_parse_context<_CharT>::iterator
305 parse(basic_format_parse_context<_CharT>& __pc)
306 {
307 __format::_Spec<_CharT> __spec{};
308 const auto __last = __pc.end();
309 auto __first = __pc.begin();
310
311 auto __finalize = [this, &__spec] {
312 _M_spec = __spec;
313 };
314
315 auto __finished = [&] {
316 if (__first == __last || *__first == '}')
317 {
318 __finalize();
319 return true;
320 }
321 return false;
322 };
323
324 if (__finished())
325 return __first;
326
327 __first = __spec._M_parse_fill_and_align(__first, __last);
328 if (__finished())
329 return __first;
330
331 __first = __spec._M_parse_width(__first, __last, __pc);
332 if (__finished())
333 return __first;
334
335 __throw_format_error("format error: invalid format-spec for "
336 "std::thread::id");
337 }
338
339 template<typename _Out>
340 typename basic_format_context<_Out, _CharT>::iterator
341 format(thread::id __id, basic_format_context<_Out, _CharT>& __fc) const
342 {
343 basic_string_view<_CharT> __sv;
344 if constexpr (is_same_v<_CharT, char>)
345 __sv = "{}thread::id of a non-executing thread";
346 else
347 __sv = L"{}thread::id of a non-executing thread";
348 basic_string<_CharT> __str;
349 if (__id == thread::id())
350 __sv.remove_prefix(2);
351 else
352 {
353 using _FmtStr = __format::_Runtime_format_string<_CharT>;
354 // Convert non-void pointers to const void* for formatted output.
355 using __output_type
356 = __conditional_t<is_pointer_v<thread::native_handle_type>,
357 const void*,
358 thread::native_handle_type>;
359 auto __o = static_cast<__output_type>(__id._M_thread);
360 __sv = __str = std::format(_FmtStr(__sv.substr(0, 2)), __o);
361 }
362 return __format::__write_padded_as_spec(__sv, __sv.size(),
363 __fc, _M_spec,
364 __format::_Align_right);
365 }
366
367 private:
368 __format::_Spec<_CharT> _M_spec;
369 };
370#endif // __cpp_lib_formatters
371
372 /// @} group threads
373
374_GLIBCXX_END_NAMESPACE_VERSION
375} // namespace
376#endif // C++11
377#endif // _GLIBCXX_THREAD
constexpr bool operator<=(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition chrono.h:859
constexpr bool operator>=(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition chrono.h:873
constexpr bool operator<(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition chrono.h:826
constexpr bool operator>(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition chrono.h:866
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition move.h:138
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition move.h:72
ISO C++ entities toplevel namespace is std.
std::basic_ostream< _CharT, _Traits > & operator<<(std::basic_ostream< _CharT, _Traits > &__os, const bitset< _Nb > &__x)
Global I/O operators for bitsets.
Definition bitset:1692
thread::id get_id() noexcept
The unique identifier of the current thread.
Definition std_thread.h:361