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The C and C++ Include Header Files

cat -n /usr/include/c++/15/semaphore

     1	// <semaphore> -*- C++ -*-
     2	
     3	// Copyright (C) 2020-2025 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/semaphore
    26	 *  This is a Standard C++ Library header.
    27	 */
    28	
    29	#ifndef _GLIBCXX_SEMAPHORE
    30	#define _GLIBCXX_SEMAPHORE 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 > 201703L
    39	#include <bits/semaphore_base.h>
    40	
    41	#define __glibcxx_want_semaphore
    42	#include <bits/version.h>
    43	
    44	#ifdef __cpp_lib_semaphore // C++ >= 20 && hosted && (atomic_wait || posix_sem)
    45	namespace std _GLIBCXX_VISIBILITY(default)
    46	{
    47	_GLIBCXX_BEGIN_NAMESPACE_VERSION
    48	
    49	  template<ptrdiff_t __least_max_value = __semaphore_impl::_S_max>
    50	    class counting_semaphore
    51	    {
    52	      static_assert(__least_max_value >= 0);
    53	      static_assert(__least_max_value <= __semaphore_impl::_S_max);
    54	
    55	      __semaphore_impl _M_sem;
    56	
    57	    public:
    58	      explicit counting_semaphore(ptrdiff_t __desired) noexcept
    59		: _M_sem(__desired)
    60	      { }
    61	
    62	      ~counting_semaphore() = default;
    63	
    64	      counting_semaphore(const counting_semaphore&) = delete;
    65	      counting_semaphore& operator=(const counting_semaphore&) = delete;
    66	
    67	      static constexpr ptrdiff_t
    68	      max() noexcept
    69	      { return __least_max_value; }
    70	
    71	      void
    72	      release(ptrdiff_t __update = 1) noexcept(noexcept(_M_sem._M_release(1)))
    73	      { _M_sem._M_release(__update); }
    74	
    75	      void
    76	      acquire() noexcept(noexcept(_M_sem._M_acquire()))
    77	      { _M_sem._M_acquire(); }
    78	
    79	      bool
    80	      try_acquire() noexcept(noexcept(_M_sem._M_try_acquire()))
    81	      { return _M_sem._M_try_acquire(); }
    82	
    83	      template<typename _Rep, typename _Period>
    84		bool
    85		try_acquire_for(const std::chrono::duration<_Rep, _Period>& __rtime)
    86		{ return _M_sem._M_try_acquire_for(__rtime); }
    87	
    88	      template<typename _Clock, typename _Dur>
    89		bool
    90		try_acquire_until(const std::chrono::time_point<_Clock, _Dur>& __atime)
    91		{ return _M_sem._M_try_acquire_until(__atime); }
    92	    };
    93	
    94	  using binary_semaphore = std::counting_semaphore<1>;
    95	
    96	_GLIBCXX_END_NAMESPACE_VERSION
    97	} // namespace
    98	#endif // cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE
    99	#endif // __cpp_lib_semaphore
   100	#endif // _GLIBCXX_SEMAPHORE