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The C and C++ Include Header Files

cat -n /usr/include/x86_64-linux-gnu/bits/fcntl-linux-fortify.h

     1	/* Checking macros for fcntl functions.  Linux version.
     2	   Copyright (C) 2025-2026 Free Software Foundation, Inc.
     3	   This file is part of the GNU C Library.
     4	
     5	   The GNU C Library is free software; you can redistribute it and/or
     6	   modify it under the terms of the GNU Lesser General Public
     7	   License as published by the Free Software Foundation; either
     8	   version 2.1 of the License, or (at your option) any later version.
     9	
    10	   The GNU C Library is distributed in the hope that it will be useful,
    11	   but WITHOUT ANY WARRANTY; without even the implied warranty of
    12	   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13	   Lesser General Public License for more details.
    14	
    15	   You should have received a copy of the GNU Lesser General Public
    16	   License along with the GNU C Library; if not, see
    17	   <https://www.gnu.org/licenses/>.  */
    18	
    19	#ifndef	_FCNTL_H
    20	# error "Never include <bits/fcntl-linux-fortify.h> directly; use <fcntl.h> instead."
    21	#endif
    22	
    23	#ifdef __USE_GNU
    24	
    25	extern int __REDIRECT (__openat2_alias, (int __dfd, const char *__filename,
    26						 const struct open_how *__how,
    27						 size_t __usize), openat2)
    28	     __nonnull ((2, 3));
    29	
    30	#if !__fortify_use_clang
    31	__errordecl (__openat2_invalid_size,
    32		     "the specified size is larger than sizeof (struct open_how)");
    33	#endif
    34	
    35	__fortify_function int
    36	openat2 (int __dfd, const char *__filename, const struct open_how *__how,
    37		 size_t __usize)
    38	     __fortify_clang_warning (__builtin_constant_p (__usize)
    39				      && __usize > sizeof (struct open_how),
    40				      "the specified size is larger than sizeof (struct open_how)")
    41	{
    42	#if !__fortify_use_clang
    43	  if (__builtin_constant_p (__usize) && __usize > sizeof (struct open_how))
    44	    __openat2_invalid_size ();
    45	#endif
    46	  return __openat2_alias (__dfd, __filename, __how, __usize);
    47	}
    48	
    49	#endif /* use GNU */