libstdc++-v3/include/std/thread

   1 // <thread> -*- C++ -*-
   2
   3 // Copyright (C) 2008-2020 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 #if __cplusplus < 201103L
  35 # include <bits/c++0x_warning.h>
  36 #else
  37
  38 #include <chrono> // std::chrono::*
  39
  40 #ifdef _GLIBCXX_USE_NANOSLEEP
  41 # include <cerrno>  // errno, EINTR
  42 # include <time.h>  // nanosleep
  43 #endif
  44
  45 #if defined(_GLIBCXX_HAS_GTHREADS)
  46 #include <bits/gthr.h>
  47
  48 #include <memory> // std::unique_ptr
  49 #include <tuple>  // std::tuple
  50
  51 #if __cplusplus > 201703L
  52 # include <compare>     // std::strong_ordering
  53 # include <stop_token>  // std::stop_source, std::stop_token, std::nostopstate
  54 #endif
  55
  56 #include <bits/functional_hash.h> // std::hash
  57 #include <bits/invoke.h>          // std::__invoke
  58
  59 #endif // _GLIBCXX_HAS_GTHREADS
  60
  61 namespace std _GLIBCXX_VISIBILITY(default)
  62 {
  63 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  64
  65   /**
  66    * @defgroup threads Threads
  67    * @ingroup concurrency
  68    *
  69    * Classes for thread support.
  70    * @{
  71    */
  72
  73 #if defined(_GLIBCXX_HAS_GTHREADS)
  74   /// thread
  75   class thread
  76   {
  77   public:
  78     // Abstract base class for types that wrap arbitrary functors to be
  79     // invoked in the new thread of execution.
  80     struct _State
  81     {
  82       virtual ~_State();
  83       virtual void _M_run() = 0;
  84     };
  85     using _State_ptr = unique_ptr<_State>;
  86
  87     typedef __gthread_t                 native_handle_type;
  88
  89     /// thread::id
  90     class id
  91     {
  92       native_handle_type        _M_thread;
  93
  94     public:
  95       id() noexcept : _M_thread() { }
  96
  97       explicit
  98       id(native_handle_type __id) : _M_thread(__id) { }
  99
 100     private:
 101       friend class thread;
 102       friend struct hash<id>;
 103
 104       friend bool
 105       operator==(id __x, id __y) noexcept;
 106
 107 #if __cpp_lib_three_way_comparison
 108       friend strong_ordering
 109       operator<=>(id __x, id __y) noexcept;
 110 #else
 111       friend bool
 112       operator<(id __x, id __y) noexcept;
 113 #endif
 114
 115       template<class _CharT, class _Traits>
 116         friend basic_ostream<_CharT, _Traits>&
 117         operator<<(basic_ostream<_CharT, _Traits>& __out, id __id);
 118     };
 119
 120   private:
 121     id                          _M_id;
 122
 123     // _GLIBCXX_RESOLVE_LIB_DEFECTS
 124     // 2097.  packaged_task constructors should be constrained
 125     // 3039. Unnecessary decay in thread and packaged_task
 126     template<typename _Tp>
 127       using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
 128
 129   public:
 130     thread() noexcept = default;
 131
 132     template<typename _Callable, typename... _Args,
 133              typename = _Require<__not_same<_Callable>>>
 134       explicit
 135       thread(_Callable&& __f, _Args&&... __args)
 136       {
 137         static_assert( __is_invocable<typename decay<_Callable>::type,
 138                                       typename decay<_Args>::type...>::value,
 139           "std::thread arguments must be invocable after conversion to rvalues"
 140           );
 141
 142 #ifdef GTHR_ACTIVE_PROXY
 143         // Create a reference to pthread_create, not just the gthr weak symbol.
 144         auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
 145 #else
 146         auto __depend = nullptr;
 147 #endif
 148         using _Wrapper = _Call_wrapper<_Callable, _Args...>;
 149         // Create a call wrapper with DECAY_COPY(__f) as its target object
 150         // and DECAY_COPY(__args)... as its bound argument entities.
 151         _M_start_thread(_State_ptr(new _State_impl<_Wrapper>(
 152               std::forward<_Callable>(__f), std::forward<_Args>(__args)...)),
 153             __depend);
 154       }
 155
 156     ~thread()
 157     {
 158       if (joinable())
 159         std::terminate();
 160     }
 161
 162     thread(const thread&) = delete;
 163
 164     thread(thread&& __t) noexcept
 165     { swap(__t); }
 166
 167     thread& operator=(const thread&) = delete;
 168
 169     thread& operator=(thread&& __t) noexcept
 170     {
 171       if (joinable())
 172         std::terminate();
 173       swap(__t);
 174       return *this;
 175     }
 176
 177     void
 178     swap(thread& __t) noexcept
 179     { std::swap(_M_id, __t._M_id); }
 180
 181     bool
 182     joinable() const noexcept
 183     { return !(_M_id == id()); }
 184
 185     void
 186     join();
 187
 188     void
 189     detach();
 190
 191     id
 192     get_id() const noexcept
 193     { return _M_id; }
 194
 195     /** @pre thread is joinable
 196      */
 197     native_handle_type
 198     native_handle()
 199     { return _M_id._M_thread; }
 200
 201     // Returns a value that hints at the number of hardware thread contexts.
 202     static unsigned int
 203     hardware_concurrency() noexcept;
 204
 205   private:
 206     template<typename _Callable>
 207       struct _State_impl : public _State
 208       {
 209         _Callable               _M_func;
 210
 211         template<typename... _Args>
 212           _State_impl(_Args&&... __args)
 213           : _M_func{{std::forward<_Args>(__args)...}}
 214           { }
 215
 216         void
 217         _M_run() { _M_func(); }
 218       };
 219
 220     void
 221     _M_start_thread(_State_ptr, void (*)());
 222
 223 #if _GLIBCXX_THREAD_ABI_COMPAT
 224   public:
 225     struct _Impl_base;
 226     typedef shared_ptr<_Impl_base>      __shared_base_type;
 227     struct _Impl_base
 228     {
 229       __shared_base_type        _M_this_ptr;
 230       virtual ~_Impl_base() = default;
 231       virtual void _M_run() = 0;
 232     };
 233
 234   private:
 235     void
 236     _M_start_thread(__shared_base_type, void (*)());
 237
 238     void
 239     _M_start_thread(__shared_base_type);
 240 #endif
 241
 242   private:
 243     // A call wrapper that does INVOKE(forwarded tuple elements...)
 244     template<typename _Tuple>
 245       struct _Invoker
 246       {
 247         _Tuple _M_t;
 248
 249         template<typename>
 250           struct __result;
 251         template<typename _Fn, typename... _Args>
 252           struct __result<tuple<_Fn, _Args...>>
 253           : __invoke_result<_Fn, _Args...>
 254           { };
 255
 256         template<size_t... _Ind>
 257           typename __result<_Tuple>::type
 258           _M_invoke(_Index_tuple<_Ind...>)
 259           { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
 260
 261         typename __result<_Tuple>::type
 262         operator()()
 263         {
 264           using _Indices
 265             = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
 266           return _M_invoke(_Indices());
 267         }
 268       };
 269
 270   public:
 271     template<typename... _Tp>
 272       using _Call_wrapper = _Invoker<tuple<typename decay<_Tp>::type...>>;
 273   };
 274
 275   inline void
 276   swap(thread& __x, thread& __y) noexcept
 277   { __x.swap(__y); }
 278
 279   inline bool
 280   operator==(thread::id __x, thread::id __y) noexcept
 281   {
 282     // pthread_equal is undefined if either thread ID is not valid, so we
 283     // can't safely use __gthread_equal on default-constructed values (nor
 284     // the non-zero value returned by this_thread::get_id() for
 285     // single-threaded programs using GNU libc). Assume EqualityComparable.
 286     return __x._M_thread == __y._M_thread;
 287   }
 288
 289 #if __cpp_lib_three_way_comparison
 290   inline strong_ordering
 291   operator<=>(thread::id __x, thread::id __y) noexcept
 292   { return __x._M_thread <=> __y._M_thread; }
 293 #else
 294   inline bool
 295   operator!=(thread::id __x, thread::id __y) noexcept
 296   { return !(__x == __y); }
 297
 298   inline bool
 299   operator<(thread::id __x, thread::id __y) noexcept
 300   {
 301     // Pthreads doesn't define any way to do this, so we just have to
 302     // assume native_handle_type is LessThanComparable.
 303     return __x._M_thread < __y._M_thread;
 304   }
 305
 306   inline bool
 307   operator<=(thread::id __x, thread::id __y) noexcept
 308   { return !(__y < __x); }
 309
 310   inline bool
 311   operator>(thread::id __x, thread::id __y) noexcept
 312   { return __y < __x; }
 313
 314   inline bool
 315   operator>=(thread::id __x, thread::id __y) noexcept
 316   { return !(__x < __y); }
 317 #endif // __cpp_lib_three_way_comparison
 318
 319   // DR 889.
 320   /// std::hash specialization for thread::id.
 321   template<>
 322     struct hash<thread::id>
 323     : public __hash_base<size_t, thread::id>
 324     {
 325       size_t
 326       operator()(const thread::id& __id) const noexcept
 327       { return std::_Hash_impl::hash(__id._M_thread); }
 328     };
 329
 330   template<class _CharT, class _Traits>
 331     inline basic_ostream<_CharT, _Traits>&
 332     operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
 333     {
 334       if (__id == thread::id())
 335         return __out << "thread::id of a non-executing thread";
 336       else
 337         return __out << __id._M_thread;
 338     }
 339 #endif // _GLIBCXX_HAS_GTHREADS
 340
 341   /** @namespace std::this_thread
 342    *  @brief ISO C++ 2011 namespace for interacting with the current thread
 343    *
 344    *  C++11 30.3.2 [thread.thread.this] Namespace this_thread.
 345    */
 346   namespace this_thread
 347   {
 348 #if defined _GLIBCXX_HAS_GTHREADS
 349     /// get_id
 350     inline thread::id
 351     get_id() noexcept
 352     {
 353 #ifdef __GLIBC__
 354       // For the GNU C library pthread_self() is usable without linking to
 355       // libpthread.so but returns 0, so we cannot use it in single-threaded
 356       // programs, because this_thread::get_id() != thread::id{} must be true.
 357       // We know that pthread_t is an integral type in the GNU C library.
 358       if (!__gthread_active_p())
 359         return thread::id(1);
 360 #endif
 361       return thread::id(__gthread_self());
 362     }
 363 #endif // _GLIBCXX_HAS_GTHREADS
 364
 365     /// yield
 366     inline void
 367     yield() noexcept
 368     {
 369 #if defined _GLIBCXX_HAS_GTHREADS && defined _GLIBCXX_USE_SCHED_YIELD
 370       __gthread_yield();
 371 #endif
 372     }
 373
 374     void
 375     __sleep_for(chrono::seconds, chrono::nanoseconds);
 376
 377     /// sleep_for
 378     template<typename _Rep, typename _Period>
 379       inline void
 380       sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
 381       {
 382         if (__rtime <= __rtime.zero())
 383           return;
 384         auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
 385         auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
 386 #ifdef _GLIBCXX_USE_NANOSLEEP
 387         struct ::timespec __ts =
 388           {
 389             static_cast<std::time_t>(__s.count()),
 390             static_cast<long>(__ns.count())
 391           };
 392         while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
 393           { }
 394 #else
 395         __sleep_for(__s, __ns);
 396 #endif
 397       }
 398
 399     /// sleep_until
 400     template<typename _Clock, typename _Duration>
 401       inline void
 402       sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
 403       {
 404 #if __cplusplus > 201703L
 405         static_assert(chrono::is_clock_v<_Clock>);
 406 #endif
 407         auto __now = _Clock::now();
 408         if (_Clock::is_steady)
 409           {
 410             if (__now < __atime)
 411               sleep_for(__atime - __now);
 412             return;
 413           }
 414         while (__now < __atime)
 415           {
 416             sleep_for(__atime - __now);
 417             __now = _Clock::now();
 418           }
 419       }
 420   }
 421
 422 #ifdef __cpp_lib_jthread
 423
 424   class jthread
 425   {
 426   public:
 427     using id = thread::id;
 428     using native_handle_type = thread::native_handle_type;
 429
 430     jthread() noexcept
 431     : _M_stop_source{nostopstate}
 432     { }
 433
 434     template<typename _Callable, typename... _Args,
 435              typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
 436                                                jthread>>>
 437       explicit
 438       jthread(_Callable&& __f, _Args&&... __args)
 439       : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
 440                             std::forward<_Args>(__args)...)}
 441       { }
 442
 443     jthread(const jthread&) = delete;
 444     jthread(jthread&&) noexcept = default;
 445
 446     ~jthread()
 447     {
 448       if (joinable())
 449         {
 450           request_stop();
 451           join();
 452         }
 453     }
 454
 455     jthread&
 456     operator=(const jthread&) = delete;
 457
 458     jthread&
 459     operator=(jthread&&) noexcept = default;
 460
 461     void
 462     swap(jthread& __other) noexcept
 463     {
 464       std::swap(_M_stop_source, __other._M_stop_source);
 465       std::swap(_M_thread, __other._M_thread);
 466     }
 467
 468     [[nodiscard]] bool
 469     joinable() const noexcept
 470     {
 471       return _M_thread.joinable();
 472     }
 473
 474     void
 475     join()
 476     {
 477       _M_thread.join();
 478     }
 479
 480     void
 481     detach()
 482     {
 483       _M_thread.detach();
 484     }
 485
 486     [[nodiscard]] id
 487     get_id() const noexcept
 488     {
 489       return _M_thread.get_id();
 490     }
 491
 492     [[nodiscard]] native_handle_type
 493     native_handle()
 494     {
 495       return _M_thread.native_handle();
 496     }
 497
 498     [[nodiscard]] static unsigned
 499     hardware_concurrency() noexcept
 500     {
 501       return thread::hardware_concurrency();
 502     }
 503
 504     [[nodiscard]] stop_source
 505     get_stop_source() noexcept
 506     {
 507       return _M_stop_source;
 508     }
 509
 510     [[nodiscard]] stop_token
 511     get_stop_token() const noexcept
 512     {
 513       return _M_stop_source.get_token();
 514     }
 515
 516     bool request_stop() noexcept
 517     {
 518       return _M_stop_source.request_stop();
 519     }
 520
 521     friend void swap(jthread& __lhs, jthread& __rhs) noexcept
 522     {
 523       __lhs.swap(__rhs);
 524     }
 525
 526   private:
 527     template<typename _Callable, typename... _Args>
 528       static thread
 529       _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
 530       {
 531         if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
 532                                     decay_t<_Args>...>)
 533           return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
 534                         std::forward<_Args>(__args)...};
 535         else
 536           {
 537             static_assert(is_invocable_v<decay_t<_Callable>,
 538                                          decay_t<_Args>...>,
 539                           "std::thread arguments must be invocable after"
 540                           " conversion to rvalues");
 541             return thread{std::forward<_Callable>(__f),
 542                           std::forward<_Args>(__args)...};
 543           }
 544       }
 545
 546     stop_source _M_stop_source;
 547     thread _M_thread;
 548   };
 549 #endif // __cpp_lib_jthread
 550
 551   // @} group threads
 552
 553 _GLIBCXX_END_NAMESPACE_VERSION
 554 } // namespace
 555 #endif // C++11
 556 #endif // _GLIBCXX_THREAD