features.h

   1 /* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #ifndef _FEATURES_H
  20
  21 #define _FEATURES_H     1
  22
  23 /* These are defined by the user (or the compiler)
  24    to specify the desired environment:
  25
  26    __STRICT_ANSI__      ANSI Standard C.
  27    _POSIX_SOURCE        IEEE Std 1003.1.
  28    _POSIX_C_SOURCE      If ==1, like _POSIX_SOURCE; if ==2 add IEEE Std 1003.2.
  29    _BSD_SOURCE          ANSI, POSIX, and 4.3BSD things.
  30    _SVID_SOURCE         ANSI, POSIX, and SVID things.
  31    _GNU_SOURCE          All of the above, plus GNU extensions.
  32
  33    The `-ansi' switch to the GNU C compiler defines __STRICT_ANSI__.
  34    If none of these are defined, the default is _GNU_SOURCE.
  35    If more than one of these are defined, they accumulate.
  36    For example __STRICT_ANSI__, _POSIX_SOURCE and _POSIX_C_SOURCE
  37    together give you ANSI C, 1003.1, and 1003.2, but nothing else.
  38
  39    These are defined by this file and are used by the
  40    header files to decide what to declare or define:
  41
  42    __USE_POSIX          Define IEEE Std 1003.1 things.
  43    __USE_POSIX2         Define IEEE Std 1003.2 things.
  44    __USE_BSD            Define 4.3BSD things.
  45    __USE_SVID           Define SVID things.
  46    __USE_MISC           Define things common to BSD and System V Unix.
  47    __USE_GNU            Define GNU extensions.
  48    __FAVOR_BSD          Favor 4.3BSD things in cases of conflict.
  49
  50    The macro `__GNU_LIBRARY__' is defined by this file unconditionally.
  51
  52    All macros defined by this file are defined as 1.
  53    All macros listed above as possibly being defined by this file are
  54    explicitly undefined if they are not explicitly defined.
  55    Feature-test macros that are not defined by the user or compiler
  56    but are implied by the other feature-test macros defined (or by the
  57    lack of any definitions) are defined by the file.  */
  58
  59
  60 /* Undefine everything, so we get a clean slate.  */
  61 #undef  __USE_POSIX
  62 #undef  __USE_POSIX2
  63 #undef  __USE_BSD
  64 #undef  __USE_SVID
  65 #undef  __USE_MISC
  66 #undef  __USE_GNU
  67 #undef  __FAVOR_BSD
  68
  69
  70 /* If nothing is defined, define _GNU_SOURCE.  */
  71 #if (!defined(_GNU_SOURCE) && !defined(__STRICT_ANSI__) && \
  72      !defined(_POSIX_SOURCE) && !defined(_POSIX_C_SOURCE) && \
  73      !defined(_BSD_SOURCE) && !defined(_SVID_SOURCE))
  74 #define _GNU_SOURCE     1
  75 #endif
  76
  77
  78 /* Always use ANSI things.  */
  79 #define __USE_ANSI      1
  80
  81
  82 /* If _BSD_SOURCE was defined by the user, favor BSD over POSIX.  */
  83 #ifdef  _BSD_SOURCE
  84 #define __FAVOR_BSD     1
  85 #endif
  86
  87
  88 /* If nothing (other than _GNU_SOURCE) is defined,
  89    define _BSD_SOURCE and _SVID_SOURCE.  */
  90 #if (!defined(__STRICT_ANSI__) && !defined(_POSIX_SOURCE) && \
  91      !defined(_POSIX_C_SOURCE) && !defined(_BSD_SOURCE) && \
  92      !defined(_SVID_SOURCE))
  93 #define _BSD_SOURCE     1
  94 #define _SVID_SOURCE    1
  95 #endif
  96
  97 /* If none of the ANSI/POSIX macros are defined, use POSIX.1 and POSIX.2.  */
  98 #if (!defined(__STRICT_ANSI__) && !defined(_POSIX_SOURCE) && \
  99      !defined(_POSIX_C_SOURCE))
 100 #define _POSIX_SOURCE   1
 101 #define _POSIX_C_SOURCE 2
 102 #endif
 103
 104 #if     defined(_POSIX_SOURCE) || _POSIX_C_SOURCE >= 1
 105 #define __USE_POSIX     1
 106 #endif
 107
 108 #if     defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 2
 109 #define __USE_POSIX2    1
 110 #endif
 111
 112 #if defined(_BSD_SOURCE) || defined(_SVID_SOURCE)
 113 #define __USE_MISC      1
 114 #endif
 115
 116 #ifdef  _BSD_SOURCE
 117 #define __USE_BSD       1
 118 #endif
 119
 120 #ifdef  _SVID_SOURCE
 121 #define __USE_SVID      1
 122 #endif
 123
 124 #ifdef  _GNU_SOURCE
 125 #define __USE_GNU       1
 126 #endif
 127
 128
 129 #undef  __GNU_LIBRARY__
 130 #define __GNU_LIBRARY__ 1
 131
 132
 133 #if     !defined(__GNUC__) || __GNUC__ < 2
 134 /* In GCC version 2, (__extension__ EXPR) will not complain
 135    about GCC extensions used in EXPR under -ansi or -pedantic.  */
 136 #define __extension__
 137 #endif
 138
 139
 140 /* This is here only because every header file already includes this one.  */
 141 #include <sys/cdefs.h>
 142
 143 #endif  /* __features.h  */