The C and C++ Include Header Files

/usr/include/c++/11/ctgmath


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

     1	// <ctgmath> -*- C++ -*-
     2	
     3	// Copyright (C) 2007-2021 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/ctgmath
    26	 *  This is a Standard C++ Library header.
    27	 */
    28	
    29	#pragma GCC system_header
    30	
    31	#ifndef _GLIBCXX_CTGMATH
    32	#define _GLIBCXX_CTGMATH 1
    33	
    34	#if __cplusplus < 201103L
    35	#  include <bits/c++0x_warning.h>
    36	#else
    37	#  include <cmath>
    38	extern "C++" {
    39	#  include <complex>
    40	}
    41	#endif
    42	
    43	#endif 
    44