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#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
48#define __glibcxx_want_jthread
49#define __glibcxx_want_formatters
50#include <bits/version.h>
51
52#if __cpp_lib_formatters
53# include <format>
54#endif
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 // Convert non-void pointers to const void* for formatted output.
108 using __output_type
109 = __conditional_t<is_pointer<thread::native_handle_type>::value,
110 const void*,
111 thread::native_handle_type>;
112
113 if (__id == thread::id())
114 return __out << "thread::id of a non-executing thread";
115 else
116 return __out << static_cast<__output_type>(__id._M_thread);
117 }
118 /// @}
119
120#ifdef __cpp_lib_jthread // C++ >= 20
121
122 /// @cond undocumented
123#ifndef __STRICT_ANSI__
124 template<typename _Callable, typename... _Args>
125 constexpr bool __pmf_expects_stop_token = false;
126
127 template<typename _Callable, typename _Obj, typename... _Args>
128 constexpr bool __pmf_expects_stop_token<_Callable, _Obj, _Args...>
129 = __and_<is_member_function_pointer<remove_reference_t<_Callable>>,
130 is_invocable<_Callable, _Obj, stop_token, _Args...>>::value;
131#endif
132 /// @endcond
133
134 /** A thread with cancellation and automatic joining.
135 *
136 * Unlike `std::thread`, destroying a joinable `std::jthread` will not
137 * terminate the process. Instead, it will try to request its thread to
138 * stop, then will join it.
139 *
140 * A `std::jthread` has a `std::stop_source` member which will be passed
141 * as the first argument to the callable that runs in the new thread
142 * (as long as the callable will accept that argument). That can then
143 * be used to send a stop request that the new thread can test for.
144 *
145 * @headerfile thread
146 * @since C++20
147 */
148 class jthread
149 {
150 public:
151 using id = thread::id;
152 using native_handle_type = thread::native_handle_type;
153
154 jthread() noexcept
155 : _M_stop_source{nostopstate}
156 { }
157
158 template<typename _Callable, typename... _Args,
159 typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
160 jthread>>>
161 explicit
162 jthread(_Callable&& __f, _Args&&... __args)
163 : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
164 std::forward<_Args>(__args)...)}
165 { }
166
167 jthread(const jthread&) = delete;
168 jthread(jthread&&) noexcept = default;
169
170 ~jthread()
171 {
172 if (joinable())
173 {
174 request_stop();
175 join();
176 }
177 }
178
179 jthread&
180 operator=(const jthread&) = delete;
181
182 jthread&
183 operator=(jthread&& __other) noexcept
184 {
185 std::jthread(std::move(__other)).swap(*this);
186 return *this;
187 }
188
189 void
190 swap(jthread& __other) noexcept
191 {
192 std::swap(_M_stop_source, __other._M_stop_source);
193 std::swap(_M_thread, __other._M_thread);
194 }
195
196 [[nodiscard]] bool
197 joinable() const noexcept
198 {
199 return _M_thread.joinable();
200 }
201
202 void
203 join()
204 {
205 _M_thread.join();
206 }
207
208 void
209 detach()
210 {
211 _M_thread.detach();
212 }
213
214 [[nodiscard]] id
215 get_id() const noexcept
216 {
217 return _M_thread.get_id();
218 }
219
220 [[nodiscard]] native_handle_type
221 native_handle()
222 {
223 return _M_thread.native_handle();
224 }
225
226 [[nodiscard]] static unsigned
227 hardware_concurrency() noexcept
228 {
229 return thread::hardware_concurrency();
230 }
231
232 [[nodiscard]] stop_source
233 get_stop_source() noexcept
234 {
235 return _M_stop_source;
236 }
237
238 [[nodiscard]] stop_token
239 get_stop_token() const noexcept
240 {
241 return _M_stop_source.get_token();
242 }
243
244 bool request_stop() noexcept
245 {
246 return _M_stop_source.request_stop();
247 }
248
249 friend void swap(jthread& __lhs, jthread& __rhs) noexcept
250 {
251 __lhs.swap(__rhs);
252 }
253
254 private:
255 template<typename _Callable, typename... _Args>
256 static thread
257 _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
258 {
259#ifndef __STRICT_ANSI__
260 if constexpr (__pmf_expects_stop_token<_Callable, _Args...>)
261 return _S_create_pmf(__ssrc, __f, std::forward<_Args>(__args)...);
262 else
263#endif
264 if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
265 decay_t<_Args>...>)
266 return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
267 std::forward<_Args>(__args)...};
268 else
269 {
270 static_assert(is_invocable_v<decay_t<_Callable>,
271 decay_t<_Args>...>,
272 "std::jthread arguments must be invocable after"
273 " conversion to rvalues");
274 return thread{std::forward<_Callable>(__f),
275 std::forward<_Args>(__args)...};
276 }
277 }
278
279#ifndef __STRICT_ANSI__
280 template<typename _Callable, typename _Obj, typename... _Args>
281 static thread
282 _S_create_pmf(stop_source& __ssrc, _Callable __f, _Obj&& __obj,
283 _Args&&... __args)
284 {
285 return thread{__f, std::forward<_Obj>(__obj), __ssrc.get_token(),
286 std::forward<_Args>(__args)...};
287 }
288#endif
289
290 stop_source _M_stop_source;
291 thread _M_thread;
292 };
293#endif // __cpp_lib_jthread
294
295#ifdef __cpp_lib_formatters // C++ >= 23
296 template<typename _CharT>
297 requires is_pointer_v<thread::native_handle_type>
298 || is_integral_v<thread::native_handle_type>
299 class formatter<thread::id, _CharT>
300 {
301 public:
302 constexpr typename basic_format_parse_context<_CharT>::iterator
303 parse(basic_format_parse_context<_CharT>& __pc)
304 {
305 __format::_Spec<_CharT> __spec{};
306 const auto __last = __pc.end();
307 auto __first = __pc.begin();
308
309 auto __finalize = [this, &__spec] {
310 _M_spec = __spec;
311 };
312
313 auto __finished = [&] {
314 if (__first == __last || *__first == '}')
315 {
316 __finalize();
317 return true;
318 }
319 return false;
320 };
321
322 if (__finished())
323 return __first;
324
325 __first = __spec._M_parse_fill_and_align(__first, __last);
326 if (__finished())
327 return __first;
328
329 __first = __spec._M_parse_width(__first, __last, __pc);
330 if (__finished())
331 return __first;
332
333 __throw_format_error("format error: invalid format-spec for "
334 "std::thread::id");
335 }
336
337 template<typename _Out>
338 typename basic_format_context<_Out, _CharT>::iterator
339 format(thread::id __id, basic_format_context<_Out, _CharT>& __fc) const
340 {
341 basic_string_view<_CharT> __sv;
342 if constexpr (is_same_v<_CharT, char>)
343 __sv = "{}thread::id of a non-executing thread";
344 else
345 __sv = L"{}thread::id of a non-executing thread";
346 basic_string<_CharT> __str;
347 if (__id == thread::id())
348 __sv.remove_prefix(2);
349 else
350 {
351 using _FmtStr = __format::_Runtime_format_string<_CharT>;
352 // Convert non-void pointers to const void* for formatted output.
353 using __output_type
354 = __conditional_t<is_pointer_v<thread::native_handle_type>,
355 const void*,
356 thread::native_handle_type>;
357 auto __o = static_cast<__output_type>(__id._M_thread);
358 __sv = __str = std::format(_FmtStr(__sv.substr(0, 2)), __o);
359 }
360 return __format::__write_padded_as_spec(__sv, __sv.size(),
361 __fc, _M_spec,
362 __format::_Align_right);
363 }
364
365 private:
366 __format::_Spec<_CharT> _M_spec;
367 };
368#endif // __cpp_lib_formatters
369
370 /// @} group threads
371
372_GLIBCXX_END_NAMESPACE_VERSION
373} // namespace
374#endif // C++11
375#endif // _GLIBCXX_THREAD
376