The C and C++ Include Header Files

/usr/include/c++/11/cfloat


$ cat -n /usr/include/c++/11/cfloat

     1	// -*- C++ -*- forwarding header.
     2	
     3	// Copyright (C) 1997-2021 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/cfloat
    26	 *  This is a Standard C++ Library file.  You should @c \#include this file
    27	 *  in your programs, rather than any of the @a *.h implementation files.
    28	 *
    29	 *  This is the C++ version of the Standard C Library header @c float.h,
    30	 *  and its contents are (mostly) the same as that header, but are all
    31	 *  contained in the namespace @c std (except for names which are defined
    32	 *  as macros in C).
    33	 */
    34	
    35	//
    36	// ISO C++ 14882: 18.2.2  Implementation properties: C library
    37	//
    38	
    39	#pragma GCC system_header
    40	
    41	#include <bits/c++config.h>
    42	#include <float.h>
    43	
    44	#ifndef _GLIBCXX_CFLOAT
    45	#define _GLIBCXX_CFLOAT 1
    46	
    47	#if __cplusplus >= 201103L
    48	#  ifndef DECIMAL_DIG
    49	#    define DECIMAL_DIG __DECIMAL_DIG__
    50	#  endif
    51	#  ifndef FLT_EVAL_METHOD
    52	#    define FLT_EVAL_METHOD __FLT_EVAL_METHOD__
    53	#  endif
    54	#endif
    55	
    56	#endif