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The C and C++ Include Header Files

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

     1	// <cfenv> -*- C++ -*-
     2	
     3	// Copyright (C) 2007-2025 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/cfenv
    26	 *  This is a Standard C++ Library header.
    27	 */
    28	
    29	#ifndef _GLIBCXX_CFENV
    30	#define _GLIBCXX_CFENV 1
    31	
    32	#ifdef _GLIBCXX_SYSHDR
    33	#pragma GCC system_header
    34	#endif
    35	
    36	#if __cplusplus < 201103L
    37	# include <bits/c++0x_warning.h>
    38	#else
    39	
    40	#include <bits/c++config.h>
    41	
    42	#if _GLIBCXX_HAVE_FENV_H
    43	# include <fenv.h>
    44	#endif
    45	
    46	#ifdef _GLIBCXX_USE_C99_FENV
    47	
    48	#undef feclearexcept
    49	#undef fegetexceptflag
    50	#undef feraiseexcept
    51	#undef fesetexceptflag
    52	#undef fetestexcept
    53	#undef fegetround
    54	#undef fesetround
    55	#undef fegetenv
    56	#undef feholdexcept
    57	#undef fesetenv
    58	#undef feupdateenv
    59	
    60	namespace std
    61	{
    62	  // types
    63	  using ::fenv_t;
    64	  using ::fexcept_t;
    65	
    66	  // functions
    67	  using ::feclearexcept;
    68	  using ::fegetexceptflag;
    69	  using ::feraiseexcept;
    70	  using ::fesetexceptflag;
    71	  using ::fetestexcept;
    72	
    73	  using ::fegetround;
    74	  using ::fesetround;
    75	
    76	  using ::fegetenv;
    77	  using ::feholdexcept;
    78	  using ::fesetenv;
    79	  using ::feupdateenv;
    80	} // namespace std
    81	
    82	#endif // _GLIBCXX_USE_C99_FENV
    83	
    84	#endif // C++11
    85	
    86	#endif // _GLIBCXX_CFENV