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 <bits/c++config.h>
  39
  40 #if defined(_GLIBCXX_HAS_GTHREADS)
  41 #include <bits/gthr.h>
  42
  43 #include <chrono> // std::chrono::*
  44 #include <memory> // std::unique_ptr
  45 #include <tuple>  // std::tuple
  46
  47 #if __cplusplus > 201703L
  48 # include <compare>     // std::strong_ordering
  49 # include <stop_token>  // std::stop_source, std::stop_token, std::nostopstate
  50 #endif
  51
  52 #ifdef _GLIBCXX_USE_NANOSLEEP
  53 # include <cerrno>  // errno, EINTR
  54 # include <time.h>  // nanosleep
  55 #endif
  56
  57 #include <bits/functional_hash.h> // std::hash
  58 #include <bits/invoke.h>          // std::__invoke
  59
  60 namespace std _GLIBCXX_VISIBILITY(default)
  61 {
  62 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  63
  64   /**
  65    * @defgroup threads Threads
  66    * @ingroup concurrency
  67    *
  68    * Classes for thread support.
  69    * @{
  70    */
  71
  72   /// thread
  73   class thread
  74   {
  75   public:
  76     // Abstract base class for types that wrap arbitrary functors to be
  77     // invoked in the new thread of execution.
  78     struct _State
  79     {
  80       virtual ~_State();
  81       virtual void _M_run() = 0;
  82     };
  83     using _State_ptr = unique_ptr<_State>;
  84
  85     typedef __gthread_t                 native_handle_type;
  86
  87     /// thread::id
  88     class id
  89     {
  90       native_handle_type        _M_thread;
  91
  92     public:
  93       id() noexcept : _M_thread() { }
  94
  95       explicit
  96       id(native_handle_type __id) : _M_thread(__id) { }
  97
  98     private:
  99       friend class thread;
 100       friend class hash<id>;
 101
 102       friend bool
 103       operator==(id __x, id __y) noexcept;
 104
 105 #if __cpp_lib_three_way_comparison
 106       friend strong_ordering
 107       operator<=>(id __x, id __y) noexcept;
 108 #else
 109       friend bool
 110       operator<(id __x, id __y) noexcept;
 111 #endif
 112
 113       template<class _CharT, class _Traits>
 114         friend basic_ostream<_CharT, _Traits>&
 115         operator<<(basic_ostream<_CharT, _Traits>& __out, id __id);
 116     };
 117
 118   private:
 119     id                          _M_id;
 120
 121     // _GLIBCXX_RESOLVE_LIB_DEFECTS
 122     // 2097.  packaged_task constructors should be constrained
 123     // 3039. Unnecessary decay in thread and packaged_task
 124     template<typename _Tp>
 125       using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;
 126
 127   public:
 128     thread() noexcept = default;
 129
 130     template<typename _Callable, typename... _Args,
 131              typename = _Require<__not_same<_Callable>>>
 132       explicit
 133       thread(_Callable&& __f, _Args&&... __args)
 134       {
 135         static_assert( __is_invocable<typename decay<_Callable>::type,
 136                                       typename decay<_Args>::type...>::value,
 137           "std::thread arguments must be invocable after conversion to rvalues"
 138           );
 139
 140 #ifdef GTHR_ACTIVE_PROXY
 141         // Create a reference to pthread_create, not just the gthr weak symbol.
 142         auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
 143 #else
 144         auto __depend = nullptr;
 145 #endif
 146         // A call wrapper holding tuple{DECAY_COPY(__f), DECAY_COPY(__args)...}
 147         using _Invoker_type = _Invoker<__decayed_tuple<_Callable, _Args...>>;
 148
 149         _M_start_thread(_S_make_state<_Invoker_type>(
 150               std::forward<_Callable>(__f), std::forward<_Args>(__args)...),
 151             __depend);
 152       }
 153
 154     ~thread()
 155     {
 156       if (joinable())
 157         std::terminate();
 158     }
 159
 160     thread(const thread&) = delete;
 161
 162     thread(thread&& __t) noexcept
 163     { swap(__t); }
 164
 165     thread& operator=(const thread&) = delete;
 166
 167     thread& operator=(thread&& __t) noexcept
 168     {
 169       if (joinable())
 170         std::terminate();
 171       swap(__t);
 172       return *this;
 173     }
 174
 175     void
 176     swap(thread& __t) noexcept
 177     { std::swap(_M_id, __t._M_id); }
 178
 179     bool
 180     joinable() const noexcept
 181     { return !(_M_id == id()); }
 182
 183     void
 184     join();
 185
 186     void
 187     detach();
 188
 189     id
 190     get_id() const noexcept
 191     { return _M_id; }
 192
 193     /** @pre thread is joinable
 194      */
 195     native_handle_type
 196     native_handle()
 197     { return _M_id._M_thread; }
 198
 199     // Returns a value that hints at the number of hardware thread contexts.
 200     static unsigned int
 201     hardware_concurrency() noexcept;
 202
 203   private:
 204     template<typename _Callable>
 205       struct _State_impl : public _State
 206       {
 207         _Callable               _M_func;
 208
 209         template<typename... _Args>
 210           _State_impl(_Args&&... __args)
 211           : _M_func{{std::forward<_Args>(__args)...}}
 212           { }
 213
 214         void
 215         _M_run() { _M_func(); }
 216       };
 217
 218     void
 219     _M_start_thread(_State_ptr, void (*)());
 220
 221     template<typename _Callable, typename... _Args>
 222       static _State_ptr
 223       _S_make_state(_Args&&... __args)
 224       {
 225         using _Impl = _State_impl<_Callable>;
 226         return _State_ptr{new _Impl{std::forward<_Args>(__args)...}};
 227       }
 228 #if _GLIBCXX_THREAD_ABI_COMPAT
 229   public:
 230     struct _Impl_base;
 231     typedef shared_ptr<_Impl_base>      __shared_base_type;
 232     struct _Impl_base
 233     {
 234       __shared_base_type        _M_this_ptr;
 235       virtual ~_Impl_base() = default;
 236       virtual void _M_run() = 0;
 237     };
 238
 239   private:
 240     void
 241     _M_start_thread(__shared_base_type, void (*)());
 242
 243     void
 244     _M_start_thread(__shared_base_type);
 245 #endif
 246
 247   private:
 248     // A call wrapper that does INVOKE(forwarded tuple elements...)
 249     template<typename _Tuple>
 250       struct _Invoker
 251       {
 252         _Tuple _M_t;
 253
 254         template<typename>
 255           struct __result;
 256         template<typename _Fn, typename... _Args>
 257           struct __result<tuple<_Fn, _Args...>>
 258           : __invoke_result<_Fn, _Args...>
 259           { };
 260
 261         template<size_t... _Ind>
 262           typename __result<_Tuple>::type
 263           _M_invoke(_Index_tuple<_Ind...>)
 264           { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
 265
 266         typename __result<_Tuple>::type
 267         operator()()
 268         {
 269           using _Indices
 270             = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
 271           return _M_invoke(_Indices());
 272         }
 273       };
 274
 275     template<typename... _Tp>
 276       using __decayed_tuple = tuple<typename decay<_Tp>::type...>;
 277
 278   public:
 279     // Returns a call wrapper that stores
 280     // tuple{DECAY_COPY(__callable), DECAY_COPY(__args)...}.
 281     template<typename _Callable, typename... _Args>
 282       static _Invoker<__decayed_tuple<_Callable, _Args...>>
 283       __make_invoker(_Callable&& __callable, _Args&&... __args)
 284       {
 285         return { __decayed_tuple<_Callable, _Args...>{
 286             std::forward<_Callable>(__callable), std::forward<_Args>(__args)...
 287         } };
 288       }
 289   };
 290
 291   inline void
 292   swap(thread& __x, thread& __y) noexcept
 293   { __x.swap(__y); }
 294
 295   inline bool
 296   operator==(thread::id __x, thread::id __y) noexcept
 297   {
 298     // pthread_equal is undefined if either thread ID is not valid, so we
 299     // can't safely use __gthread_equal on default-constructed values (nor
 300     // the non-zero value returned by this_thread::get_id() for
 301     // single-threaded programs using GNU libc). Assume EqualityComparable.
 302     return __x._M_thread == __y._M_thread;
 303   }
 304
 305 #if __cpp_lib_three_way_comparison
 306   inline strong_ordering
 307   operator<=>(thread::id __x, thread::id __y) noexcept
 308   { return __x._M_thread <=> __y._M_thread; }
 309 #else
 310   inline bool
 311   operator!=(thread::id __x, thread::id __y) noexcept
 312   { return !(__x == __y); }
 313
 314   inline bool
 315   operator<(thread::id __x, thread::id __y) noexcept
 316   {
 317     // Pthreads doesn't define any way to do this, so we just have to
 318     // assume native_handle_type is LessThanComparable.
 319     return __x._M_thread < __y._M_thread;
 320   }
 321
 322   inline bool
 323   operator<=(thread::id __x, thread::id __y) noexcept
 324   { return !(__y < __x); }
 325
 326   inline bool
 327   operator>(thread::id __x, thread::id __y) noexcept
 328   { return __y < __x; }
 329
 330   inline bool
 331   operator>=(thread::id __x, thread::id __y) noexcept
 332   { return !(__x < __y); }
 333 #endif // __cpp_lib_three_way_comparison
 334
 335   // DR 889.
 336   /// std::hash specialization for thread::id.
 337   template<>
 338     struct hash<thread::id>
 339     : public __hash_base<size_t, thread::id>
 340     {
 341       size_t
 342       operator()(const thread::id& __id) const noexcept
 343       { return std::_Hash_impl::hash(__id._M_thread); }
 344     };
 345
 346   template<class _CharT, class _Traits>
 347     inline basic_ostream<_CharT, _Traits>&
 348     operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
 349     {
 350       if (__id == thread::id())
 351         return __out << "thread::id of a non-executing thread";
 352       else
 353         return __out << __id._M_thread;
 354     }
 355
 356   /** @namespace std::this_thread
 357    *  @brief ISO C++ 2011 namespace for interacting with the current thread
 358    *
 359    *  C++11 30.3.2 [thread.thread.this] Namespace this_thread.
 360    */
 361   namespace this_thread
 362   {
 363     /// get_id
 364     inline thread::id
 365     get_id() noexcept
 366     {
 367 #ifdef __GLIBC__
 368       // For the GNU C library pthread_self() is usable without linking to
 369       // libpthread.so but returns 0, so we cannot use it in single-threaded
 370       // programs, because this_thread::get_id() != thread::id{} must be true.
 371       // We know that pthread_t is an integral type in the GNU C library.
 372       if (!__gthread_active_p())
 373         return thread::id(1);
 374 #endif
 375       return thread::id(__gthread_self());
 376     }
 377
 378     /// yield
 379     inline void
 380     yield() noexcept
 381     {
 382 #ifdef _GLIBCXX_USE_SCHED_YIELD
 383       __gthread_yield();
 384 #endif
 385     }
 386
 387     void
 388     __sleep_for(chrono::seconds, chrono::nanoseconds);
 389
 390     /// sleep_for
 391     template<typename _Rep, typename _Period>
 392       inline void
 393       sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
 394       {
 395         if (__rtime <= __rtime.zero())
 396           return;
 397         auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
 398         auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
 399 #ifdef _GLIBCXX_USE_NANOSLEEP
 400         __gthread_time_t __ts =
 401           {
 402             static_cast<std::time_t>(__s.count()),
 403             static_cast<long>(__ns.count())
 404           };
 405         while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
 406           { }
 407 #else
 408         __sleep_for(__s, __ns);
 409 #endif
 410       }
 411
 412     /// sleep_until
 413     template<typename _Clock, typename _Duration>
 414       inline void
 415       sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
 416       {
 417         auto __now = _Clock::now();
 418         if (_Clock::is_steady)
 419           {
 420             if (__now < __atime)
 421               sleep_for(__atime - __now);
 422             return;
 423           }
 424         while (__now < __atime)
 425           {
 426             sleep_for(__atime - __now);
 427             __now = _Clock::now();
 428           }
 429       }
 430   }
 431
 432   // @} group threads
 433
 434 #ifdef __cpp_lib_jthread
 435
 436   class jthread
 437   {
 438   public:
 439     using id = thread::id;
 440     using native_handle_type = thread::native_handle_type;
 441
 442     jthread() noexcept
 443     : _M_stop_source{nostopstate}
 444     { }
 445
 446     template<typename _Callable, typename... _Args,
 447              typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
 448                                                jthread>>>
 449       explicit
 450       jthread(_Callable&& __f, _Args&&... __args)
 451       : _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
 452                             std::forward<_Args>(__args)...)}
 453       { }
 454
 455     jthread(const jthread&) = delete;
 456     jthread(jthread&&) noexcept = default;
 457
 458     ~jthread()
 459     {
 460       if (joinable())
 461         {
 462           request_stop();
 463           join();
 464         }
 465     }
 466
 467     jthread&
 468     operator=(const jthread&) = delete;
 469
 470     jthread&
 471     operator=(jthread&&) noexcept = default;
 472
 473     void
 474     swap(jthread& __other) noexcept
 475     {
 476       std::swap(_M_stop_source, __other._M_stop_source);
 477       std::swap(_M_thread, __other._M_thread);
 478     }
 479
 480     [[nodiscard]] bool
 481     joinable() const noexcept
 482     {
 483       return _M_thread.joinable();
 484     }
 485
 486     void
 487     join()
 488     {
 489       _M_thread.join();
 490     }
 491
 492     void
 493     detach()
 494     {
 495       _M_thread.detach();
 496     }
 497
 498     [[nodiscard]] id
 499     get_id() const noexcept
 500     {
 501       return _M_thread.get_id();
 502     }
 503
 504     [[nodiscard]] native_handle_type
 505     native_handle()
 506     {
 507       return _M_thread.native_handle();
 508     }
 509
 510     [[nodiscard]] static unsigned
 511     hardware_concurrency() noexcept
 512     {
 513       return thread::hardware_concurrency();
 514     }
 515
 516     [[nodiscard]] stop_source
 517     get_stop_source() noexcept
 518     {
 519       return _M_stop_source;
 520     }
 521
 522     [[nodiscard]] stop_token
 523     get_stop_token() const noexcept
 524     {
 525       return _M_stop_source.get_token();
 526     }
 527
 528     bool request_stop() noexcept
 529     {
 530       return _M_stop_source.request_stop();
 531     }
 532
 533     friend void swap(jthread& __lhs, jthread& __rhs) noexcept
 534     {
 535       __lhs.swap(__rhs);
 536     }
 537
 538   private:
 539     template<typename _Callable, typename... _Args>
 540       static thread
 541       _S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
 542       {
 543         if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
 544                                     decay_t<_Args>...>)
 545           return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
 546                         std::forward<_Args>(__args)...};
 547         else
 548           {
 549             static_assert(is_invocable_v<decay_t<_Callable>,
 550                                          decay_t<_Args>...>,
 551                           "std::thread arguments must be invocable after"
 552                           " conversion to rvalues");
 553             return thread{std::forward<_Callable>(__f),
 554                           std::forward<_Args>(__args)...};
 555           }
 556       }
 557
 558     stop_source _M_stop_source;
 559     thread _M_thread;
 560   };
 561 #endif // __cpp_lib_jthread
 562 _GLIBCXX_END_NAMESPACE_VERSION
 563 } // namespace
 564 #endif // _GLIBCXX_HAS_GTHREADS
 565 #endif // C++11
 566 #endif // _GLIBCXX_THREAD