1// std::thread declarations -*- C++ -*-
2
3// Copyright (C) 2008-2021 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 <exception> // std::terminate
39#include <iosfwd> // std::basic_ostream
40#include <tuple> // std::tuple
41#include <bits/functional_hash.h> // std::hash
42#include <bits/invoke.h> // std::__invoke
43#include <bits/refwrap.h> // not required, but helpful to users
44#include <bits/unique_ptr.h> // std::unique_ptr
45
46#ifdef _GLIBCXX_HAS_GTHREADS
47# include <bits/gthr.h>
48#else
49# include <errno.h>
50# include <bits/functexcept.h>
51#endif
52
53namespace std _GLIBCXX_VISIBILITY(default)
54{
55_GLIBCXX_BEGIN_NAMESPACE_VERSION
56
57 /** @addtogroup threads
58 * @{
59 */
60
61 /// thread
62 class thread
63 {
64 public:
65#ifdef _GLIBCXX_HAS_GTHREADS
66 // Abstract base class for types that wrap arbitrary functors to be
67 // invoked in the new thread of execution.
68 struct _State
69 {
70 virtual ~_State();
71 virtual void _M_run() = 0;
72 };
73 using _State_ptr = unique_ptr<_State>;
74
75 using native_handle_type = __gthread_t;
76#else
77 using native_handle_type = int;
78#endif
79
80 /// thread::id
81 class id
82 {
83 native_handle_type _M_thread;
84
85 public:
86 id() noexcept : _M_thread() { }
87
88 explicit
89 id(native_handle_type __id) : _M_thread(__id) { }
90
91 private:
92 friend class thread;
93 friend struct hash<id>;
94
95 friend bool
96 operator==(id __x, id __y) noexcept;
97
98#if __cpp_lib_three_way_comparison
99 friend strong_ordering
100 operator<=>(id __x, id __y) noexcept;
101#else
102 friend bool
103 operator<(id __x, id __y) noexcept;
104#endif
105
106 template<class _CharT, class _Traits>
107 friend basic_ostream<_CharT, _Traits>&
108 operator<<(basic_ostream<_CharT, _Traits>& __out, id __id);
109 };
110
111 private:
112 id _M_id;
113
114 // _GLIBCXX_RESOLVE_LIB_DEFECTS
115 // 2097. packaged_task constructors should be constrained
116 // 3039. Unnecessary decay in thread and packaged_task
117 template<typename _Tp>
118 using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
119
120 public:
121 thread() noexcept = default;
122
123#ifdef _GLIBCXX_HAS_GTHREADS
124 template<typename _Callable, typename... _Args,
125 typename = _Require<__not_same<_Callable>>>
126 explicit
127 thread(_Callable&& __f, _Args&&... __args)
128 {
129 static_assert( __is_invocable<typename decay<_Callable>::type,
130 typename decay<_Args>::type...>::value,
131 "std::thread arguments must be invocable after conversion to rvalues"
132 );
133
134#ifdef GTHR_ACTIVE_PROXY
135 // Create a reference to pthread_create, not just the gthr weak symbol.
136 auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
137#else
138 auto __depend = nullptr;
139#endif
140 using _Wrapper = _Call_wrapper<_Callable, _Args...>;
141 // Create a call wrapper with DECAY_COPY(__f) as its target object
142 // and DECAY_COPY(__args)... as its bound argument entities.
143 _M_start_thread(_State_ptr(new _State_impl<_Wrapper>(
144 std::forward<_Callable>(__f), std::forward<_Args>(__args)...)),
145 __depend);
146 }
147#endif // _GLIBCXX_HAS_GTHREADS
148
149 ~thread()
150 {
151 if (joinable())
152 std::terminate();
153 }
154
155 thread(const thread&) = delete;
156
157 thread(thread&& __t) noexcept
158 { swap(__t); }
159
160 thread& operator=(const thread&) = delete;
161
162 thread& operator=(thread&& __t) noexcept
163 {
164 if (joinable())
165 std::terminate();
166 swap(__t);
167 return *this;
168 }
169
170 void
171 swap(thread& __t) noexcept
172 { std::swap(_M_id, __t._M_id); }
173
174 bool
175 joinable() const noexcept
176 { return !(_M_id == id()); }
177
178 void
179 join();
180
181 void
182 detach();
183
184 id
185 get_id() const noexcept
186 { return _M_id; }
187
188 /** @pre thread is joinable
189 */
190 native_handle_type
191 native_handle()
192 { return _M_id._M_thread; }
193
194 // Returns a value that hints at the number of hardware thread contexts.
195 static unsigned int
196 hardware_concurrency() noexcept;
197
198#ifdef _GLIBCXX_HAS_GTHREADS
199 private:
200 template<typename _Callable>
201 struct _State_impl : public _State
202 {
203 _Callable _M_func;
204
205 template<typename... _Args>
206 _State_impl(_Args&&... __args)
207 : _M_func{{std::forward<_Args>(__args)...}}
208 { }
209
210 void
211 _M_run() { _M_func(); }
212 };
213
214 void
215 _M_start_thread(_State_ptr, void (*)());
216
217#if _GLIBCXX_THREAD_ABI_COMPAT
218 public:
219 struct _Impl_base;
220 typedef shared_ptr<_Impl_base> __shared_base_type;
221 struct _Impl_base
222 {
223 __shared_base_type _M_this_ptr;
224 virtual ~_Impl_base() = default;
225 virtual void _M_run() = 0;
226 };
227
228 private:
229 void
230 _M_start_thread(__shared_base_type, void (*)());
231
232 void
233 _M_start_thread(__shared_base_type);
234#endif
235
236 private:
237 // A call wrapper that does INVOKE(forwarded tuple elements...)
238 template<typename _Tuple>
239 struct _Invoker
240 {
241 _Tuple _M_t;
242
243 template<typename>
244 struct __result;
245 template<typename _Fn, typename... _Args>
246 struct __result<tuple<_Fn, _Args...>>
247 : __invoke_result<_Fn, _Args...>
248 { };
249
250 template<size_t... _Ind>
251 typename __result<_Tuple>::type
252 _M_invoke(_Index_tuple<_Ind...>)
253 { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
254
255 typename __result<_Tuple>::type
256 operator()()
257 {
258 using _Indices
259 = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
260 return _M_invoke(_Indices());
261 }
262 };
263
264 public:
265 template<typename... _Tp>
266 using _Call_wrapper = _Invoker<tuple<typename decay<_Tp>::type...>>;
267#endif // _GLIBCXX_HAS_GTHREADS
268 };
269
270#ifndef _GLIBCXX_HAS_GTHREADS
271 inline void thread::join() { std::__throw_system_error(EINVAL); }
272 inline void thread::detach() { std::__throw_system_error(EINVAL); }
273 inline unsigned int thread::hardware_concurrency() noexcept { return 0; }
274#endif
275
276 inline void
277 swap(thread& __x, thread& __y) noexcept
278 { __x.swap(__y); }
279
280 inline bool
281 operator==(thread::id __x, thread::id __y) noexcept
282 {
283 // pthread_equal is undefined if either thread ID is not valid, so we
284 // can't safely use __gthread_equal on default-constructed values (nor
285 // the non-zero value returned by this_thread::get_id() for
286 // single-threaded programs using GNU libc). Assume EqualityComparable.
287 return __x._M_thread == __y._M_thread;
288 }
289
290 // N.B. other comparison operators are defined in <thread>
291
292 // DR 889.
293 /// std::hash specialization for thread::id.
294 template<>
295 struct hash<thread::id>
296 : public __hash_base<size_t, thread::id>
297 {
298 size_t
299 operator()(const thread::id& __id) const noexcept
300 { return std::_Hash_impl::hash(__id._M_thread); }
301 };
302
303 namespace this_thread
304 {
305 /// this_thread::get_id
306 inline thread::id
307 get_id() noexcept
308 {
309#ifndef _GLIBCXX_HAS_GTHREADS
310 return thread::id(1);
311#elif defined _GLIBCXX_NATIVE_THREAD_ID
312 return thread::id(_GLIBCXX_NATIVE_THREAD_ID);
313#else
314 return thread::id(__gthread_self());
315#endif
316 }
317
318 /// this_thread::yield
319 inline void
320 yield() noexcept
321 {
322#if defined _GLIBCXX_HAS_GTHREADS && defined _GLIBCXX_USE_SCHED_YIELD
323 __gthread_yield();
324#endif
325 }
326
327 } // namespace this_thread
328
329 /// @}
330
331_GLIBCXX_END_NAMESPACE_VERSION
332} // namespace
333#endif // C++11
334
335#endif // _GLIBCXX_THREAD_H
336