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The C and C++ Include Header Files

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

     1	// <execution> -*- C++ -*-
     2	
     3	// Copyright (C) 2018-2025 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	#ifndef _GLIBCXX_EXECUTION
    26	#define _GLIBCXX_EXECUTION 1
    27	
    28	#ifdef _GLIBCXX_SYSHDR
    29	#pragma GCC system_header
    30	#endif
    31	
    32	#include <bits/requires_hosted.h> // execution policies are hosted only
    33	
    34	#define __glibcxx_want_parallel_algorithm
    35	#define __glibcxx_want_execution
    36	#include <bits/version.h>
    37	
    38	// C++ >= 17 && HOSTED
    39	#if defined(__cpp_lib_parallel_algorithm) || defined(__cpp_lib_execution)
    40	# include <bits/c++config.h>
    41	# include <pstl/glue_execution_defs.h>
    42	
    43	# define _PSTL_EXECUTION_POLICIES_DEFINED 1
    44	
    45	// Algorithm implementation
    46	# if _PSTL_ALGORITHM_FORWARD_DECLARED
    47	#  include <pstl/glue_algorithm_impl.h>
    48	# endif
    49	
    50	// Numeric implementation
    51	# if _PSTL_NUMERIC_FORWARD_DECLARED
    52	#  include <pstl/glue_numeric_impl.h>
    53	# endif
    54	
    55	// Memory implementation
    56	# if _PSTL_NUMERIC_FORWARD_DECLARED
    57	#  include <pstl/glue_memory_impl.h>
    58	# endif
    59	
    60	#endif // C++17
    61	
    62	#endif /* _GLIBCXX_EXECUTION */