include/features.h

   1 /* Copyright (C) 1991-2018 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _FEATURES_H
  19 #define _FEATURES_H     1
  20
  21 /* These are defined by the user (or the compiler)
  22    to specify the desired environment:
  23
  24    __STRICT_ANSI__      ISO Standard C.
  25    _ISOC99_SOURCE       Extensions to ISO C89 from ISO C99.
  26    _ISOC11_SOURCE       Extensions to ISO C99 from ISO C11.
  27    __STDC_WANT_LIB_EXT2__
  28                         Extensions to ISO C99 from TR 27431-2:2010.
  29    __STDC_WANT_IEC_60559_BFP_EXT__
  30                         Extensions to ISO C11 from TS 18661-1:2014.
  31    __STDC_WANT_IEC_60559_FUNCS_EXT__
  32                         Extensions to ISO C11 from TS 18661-4:2015.
  33    __STDC_WANT_IEC_60559_TYPES_EXT__
  34                         Extensions to ISO C11 from TS 18661-3:2015.
  35
  36    _POSIX_SOURCE        IEEE Std 1003.1.
  37    _POSIX_C_SOURCE      If ==1, like _POSIX_SOURCE; if >=2 add IEEE Std 1003.2;
  38                         if >=199309L, add IEEE Std 1003.1b-1993;
  39                         if >=199506L, add IEEE Std 1003.1c-1995;
  40                         if >=200112L, all of IEEE 1003.1-2004
  41                         if >=200809L, all of IEEE 1003.1-2008
  42    _XOPEN_SOURCE        Includes POSIX and XPG things.  Set to 500 if
  43                         Single Unix conformance is wanted, to 600 for the
  44                         sixth revision, to 700 for the seventh revision.
  45    _XOPEN_SOURCE_EXTENDED XPG things and X/Open Unix extensions.
  46    _LARGEFILE_SOURCE    Some more functions for correct standard I/O.
  47    _LARGEFILE64_SOURCE  Additional functionality from LFS for large files.
  48    _FILE_OFFSET_BITS=N  Select default filesystem interface.
  49    _ATFILE_SOURCE       Additional *at interfaces.
  50    _GNU_SOURCE          All of the above, plus GNU extensions.
  51    _DEFAULT_SOURCE      The default set of features (taking precedence over
  52                         __STRICT_ANSI__).
  53
  54    _FORTIFY_SOURCE      Add security hardening to many library functions.
  55                         Set to 1 or 2; 2 performs stricter checks than 1.
  56
  57    _REENTRANT, _THREAD_SAFE
  58                         Obsolete; equivalent to _POSIX_C_SOURCE=199506L.
  59
  60    The `-ansi' switch to the GNU C compiler, and standards conformance
  61    options such as `-std=c99', define __STRICT_ANSI__.  If none of
  62    these are defined, or if _DEFAULT_SOURCE is defined, the default is
  63    to have _POSIX_SOURCE set to one and _POSIX_C_SOURCE set to
  64    200809L, as well as enabling miscellaneous functions from BSD and
  65    SVID.  If more than one of these are defined, they accumulate.  For
  66    example __STRICT_ANSI__, _POSIX_SOURCE and _POSIX_C_SOURCE together
  67    give you ISO C, 1003.1, and 1003.2, but nothing else.
  68
  69    These are defined by this file and are used by the
  70    header files to decide what to declare or define:
  71
  72    __GLIBC_USE (F)      Define things from feature set F.  This is defined
  73                         to 1 or 0; the subsequent macros are either defined
  74                         or undefined, and those tests should be moved to
  75                         __GLIBC_USE.
  76    __USE_ISOC11         Define ISO C11 things.
  77    __USE_ISOC99         Define ISO C99 things.
  78    __USE_ISOC95         Define ISO C90 AMD1 (C95) things.
  79    __USE_ISOCXX11       Define ISO C++11 things.
  80    __USE_POSIX          Define IEEE Std 1003.1 things.
  81    __USE_POSIX2         Define IEEE Std 1003.2 things.
  82    __USE_POSIX199309    Define IEEE Std 1003.1, and .1b things.
  83    __USE_POSIX199506    Define IEEE Std 1003.1, .1b, .1c and .1i things.
  84    __USE_XOPEN          Define XPG things.
  85    __USE_XOPEN_EXTENDED Define X/Open Unix things.
  86    __USE_UNIX98         Define Single Unix V2 things.
  87    __USE_XOPEN2K        Define XPG6 things.
  88    __USE_XOPEN2KXSI     Define XPG6 XSI things.
  89    __USE_XOPEN2K8       Define XPG7 things.
  90    __USE_XOPEN2K8XSI    Define XPG7 XSI things.
  91    __USE_LARGEFILE      Define correct standard I/O things.
  92    __USE_LARGEFILE64    Define LFS things with separate names.
  93    __USE_FILE_OFFSET64  Define 64bit interface as default.
  94    __USE_MISC           Define things from 4.3BSD or System V Unix.
  95    __USE_ATFILE         Define *at interfaces and AT_* constants for them.
  96    __USE_GNU            Define GNU extensions.
  97    __USE_FORTIFY_LEVEL  Additional security measures used, according to level.
  98
  99    The macros `__GNU_LIBRARY__', `__GLIBC__', and `__GLIBC_MINOR__' are
 100    defined by this file unconditionally.  `__GNU_LIBRARY__' is provided
 101    only for compatibility.  All new code should use the other symbols
 102    to test for features.
 103
 104    All macros listed above as possibly being defined by this file are
 105    explicitly undefined if they are not explicitly defined.
 106    Feature-test macros that are not defined by the user or compiler
 107    but are implied by the other feature-test macros defined (or by the
 108    lack of any definitions) are defined by the file.
 109
 110    ISO C feature test macros depend on the definition of the macro
 111    when an affected header is included, not when the first system
 112    header is included, and so they are handled in
 113    <bits/libc-header-start.h>, which does not have a multiple include
 114    guard.  Feature test macros that can be handled from the first
 115    system header included are handled here.  */
 116
 117
 118 /* Undefine everything, so we get a clean slate.  */
 119 #undef  __USE_ISOC11
 120 #undef  __USE_ISOC99
 121 #undef  __USE_ISOC95
 122 #undef  __USE_ISOCXX11
 123 #undef  __USE_POSIX
 124 #undef  __USE_POSIX2
 125 #undef  __USE_POSIX199309
 126 #undef  __USE_POSIX199506
 127 #undef  __USE_XOPEN
 128 #undef  __USE_XOPEN_EXTENDED
 129 #undef  __USE_UNIX98
 130 #undef  __USE_XOPEN2K
 131 #undef  __USE_XOPEN2KXSI
 132 #undef  __USE_XOPEN2K8
 133 #undef  __USE_XOPEN2K8XSI
 134 #undef  __USE_LARGEFILE
 135 #undef  __USE_LARGEFILE64
 136 #undef  __USE_FILE_OFFSET64
 137 #undef  __USE_MISC
 138 #undef  __USE_ATFILE
 139 #undef  __USE_GNU
 140 #undef  __USE_FORTIFY_LEVEL
 141 #undef  __KERNEL_STRICT_NAMES
 142 #undef  __GLIBC_USE_DEPRECATED_GETS
 143
 144 /* Suppress kernel-name space pollution unless user expressedly asks
 145    for it.  */
 146 #ifndef _LOOSE_KERNEL_NAMES
 147 # define __KERNEL_STRICT_NAMES
 148 #endif
 149
 150 /* Convenience macro to test the version of gcc.
 151    Use like this:
 152    #if __GNUC_PREREQ (2,8)
 153    ... code requiring gcc 2.8 or later ...
 154    #endif
 155    Note: only works for GCC 2.0 and later, because __GNUC_MINOR__ was
 156    added in 2.0.  */
 157 #if defined __GNUC__ && defined __GNUC_MINOR__
 158 # define __GNUC_PREREQ(maj, min) \
 159         ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
 160 #else
 161 # define __GNUC_PREREQ(maj, min) 0
 162 #endif
 163
 164 /* Similarly for clang.  Features added to GCC after version 4.2 may
 165    or may not also be available in clang, and clang's definitions of
 166    __GNUC(_MINOR)__ are fixed at 4 and 2 respectively.  Not all such
 167    features can be queried via __has_extension/__has_feature.  */
 168 #if defined __clang_major__ && defined __clang_minor__
 169 # define __glibc_clang_prereq(maj, min) \
 170   ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
 171 #else
 172 # define __glibc_clang_prereq(maj, min) 0
 173 #endif
 174
 175 /* Whether to use feature set F.  */
 176 #define __GLIBC_USE(F)  __GLIBC_USE_ ## F
 177
 178 /* _BSD_SOURCE and _SVID_SOURCE are deprecated aliases for
 179    _DEFAULT_SOURCE.  If _DEFAULT_SOURCE is present we do not
 180    issue a warning; the expectation is that the source is being
 181    transitioned to use the new macro.  */
 182 #if (defined _BSD_SOURCE || defined _SVID_SOURCE) \
 183     && !defined _DEFAULT_SOURCE
 184 # warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
 185 # undef  _DEFAULT_SOURCE
 186 # define _DEFAULT_SOURCE        1
 187 #endif
 188
 189 /* If _GNU_SOURCE was defined by the user, turn on all the other features.  */
 190 #ifdef _GNU_SOURCE
 191 # undef  _ISOC95_SOURCE
 192 # define _ISOC95_SOURCE 1
 193 # undef  _ISOC99_SOURCE
 194 # define _ISOC99_SOURCE 1
 195 # undef  _ISOC11_SOURCE
 196 # define _ISOC11_SOURCE 1
 197 # undef  _POSIX_SOURCE
 198 # define _POSIX_SOURCE  1
 199 # undef  _POSIX_C_SOURCE
 200 # define _POSIX_C_SOURCE        200809L
 201 # undef  _XOPEN_SOURCE
 202 # define _XOPEN_SOURCE  700
 203 # undef  _XOPEN_SOURCE_EXTENDED
 204 # define _XOPEN_SOURCE_EXTENDED 1
 205 # undef  _LARGEFILE64_SOURCE
 206 # define _LARGEFILE64_SOURCE    1
 207 # undef  _DEFAULT_SOURCE
 208 # define _DEFAULT_SOURCE        1
 209 # undef  _ATFILE_SOURCE
 210 # define _ATFILE_SOURCE 1
 211 #endif
 212
 213 /* If nothing (other than _GNU_SOURCE and _DEFAULT_SOURCE) is defined,
 214    define _DEFAULT_SOURCE.  */
 215 #if (defined _DEFAULT_SOURCE                                    \
 216      || (!defined __STRICT_ANSI__                               \
 217          && !defined _ISOC99_SOURCE && !defined _ISOC11_SOURCE  \
 218          && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE  \
 219          && !defined _XOPEN_SOURCE))
 220 # undef  _DEFAULT_SOURCE
 221 # define _DEFAULT_SOURCE        1
 222 #endif
 223
 224 /* This is to enable the ISO C11 extension.  */
 225 #if (defined _ISOC11_SOURCE \
 226      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L))
 227 # define __USE_ISOC11   1
 228 #endif
 229
 230 /* This is to enable the ISO C99 extension.  */
 231 #if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE \
 232      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L))
 233 # define __USE_ISOC99   1
 234 #endif
 235
 236 /* This is to enable the ISO C90 Amendment 1:1995 extension.  */
 237 #if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE \
 238      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199409L))
 239 # define __USE_ISOC95   1
 240 #endif
 241
 242 #ifdef __cplusplus
 243 /* This is to enable compatibility for ISO C++17.  */
 244 # if __cplusplus >= 201703L
 245 #  define __USE_ISOC11  1
 246 # endif
 247 /* This is to enable compatibility for ISO C++11.
 248    Check the temporary macro for now, too.  */
 249 # if __cplusplus >= 201103L || defined __GXX_EXPERIMENTAL_CXX0X__
 250 #  define __USE_ISOCXX11        1
 251 #  define __USE_ISOC99  1
 252 # endif
 253 #endif
 254
 255 /* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE
 256    is defined, use POSIX.1-2008 (or another version depending on
 257    _XOPEN_SOURCE).  */
 258 #ifdef _DEFAULT_SOURCE
 259 # if !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE
 260 #  define __USE_POSIX_IMPLICITLY        1
 261 # endif
 262 # undef  _POSIX_SOURCE
 263 # define _POSIX_SOURCE  1
 264 # undef  _POSIX_C_SOURCE
 265 # define _POSIX_C_SOURCE        200809L
 266 #endif
 267
 268 #if ((!defined __STRICT_ANSI__                                  \
 269       || (defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) >= 500)) \
 270      && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE)
 271 # define _POSIX_SOURCE  1
 272 # if defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 500
 273 #  define _POSIX_C_SOURCE       2
 274 # elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 600
 275 #  define _POSIX_C_SOURCE       199506L
 276 # elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 700
 277 #  define _POSIX_C_SOURCE       200112L
 278 # else
 279 #  define _POSIX_C_SOURCE       200809L
 280 # endif
 281 # define __USE_POSIX_IMPLICITLY 1
 282 #endif
 283
 284 /* Some C libraries once required _REENTRANT and/or _THREAD_SAFE to be
 285    defined in all multithreaded code.  GNU libc has not required this
 286    for many years.  We now treat them as compatibility synonyms for
 287    _POSIX_C_SOURCE=199506L, which is the earliest level of POSIX with
 288    comprehensive support for multithreaded code.  Using them never
 289    lowers the selected level of POSIX conformance, only raises it.  */
 290 #if ((!defined _POSIX_C_SOURCE || (_POSIX_C_SOURCE - 0) < 199506L) \
 291      && (defined _REENTRANT || defined _THREAD_SAFE))
 292 # define _POSIX_SOURCE   1
 293 # undef  _POSIX_C_SOURCE
 294 # define _POSIX_C_SOURCE 199506L
 295 #endif
 296
 297 #if (defined _POSIX_SOURCE                                      \
 298      || (defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 1)       \
 299      || defined _XOPEN_SOURCE)
 300 # define __USE_POSIX    1
 301 #endif
 302
 303 #if defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 2 || defined _XOPEN_SOURCE
 304 # define __USE_POSIX2   1
 305 #endif
 306
 307 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199309L
 308 # define __USE_POSIX199309      1
 309 #endif
 310
 311 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199506L
 312 # define __USE_POSIX199506      1
 313 #endif
 314
 315 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200112L
 316 # define __USE_XOPEN2K          1
 317 # undef __USE_ISOC95
 318 # define __USE_ISOC95           1
 319 # undef __USE_ISOC99
 320 # define __USE_ISOC99           1
 321 #endif
 322
 323 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200809L
 324 # define __USE_XOPEN2K8         1
 325 # undef  _ATFILE_SOURCE
 326 # define _ATFILE_SOURCE 1
 327 #endif
 328
 329 #ifdef  _XOPEN_SOURCE
 330 # define __USE_XOPEN    1
 331 # if (_XOPEN_SOURCE - 0) >= 500
 332 #  define __USE_XOPEN_EXTENDED  1
 333 #  define __USE_UNIX98  1
 334 #  undef _LARGEFILE_SOURCE
 335 #  define _LARGEFILE_SOURCE     1
 336 #  if (_XOPEN_SOURCE - 0) >= 600
 337 #   if (_XOPEN_SOURCE - 0) >= 700
 338 #    define __USE_XOPEN2K8      1
 339 #    define __USE_XOPEN2K8XSI   1
 340 #   endif
 341 #   define __USE_XOPEN2K        1
 342 #   define __USE_XOPEN2KXSI     1
 343 #   undef __USE_ISOC95
 344 #   define __USE_ISOC95         1
 345 #   undef __USE_ISOC99
 346 #   define __USE_ISOC99         1
 347 #  endif
 348 # else
 349 #  ifdef _XOPEN_SOURCE_EXTENDED
 350 #   define __USE_XOPEN_EXTENDED 1
 351 #  endif
 352 # endif
 353 #endif
 354
 355 #ifdef _LARGEFILE_SOURCE
 356 # define __USE_LARGEFILE        1
 357 #endif
 358
 359 #ifdef _LARGEFILE64_SOURCE
 360 # define __USE_LARGEFILE64      1
 361 #endif
 362
 363 #if defined _FILE_OFFSET_BITS && _FILE_OFFSET_BITS == 64
 364 # define __USE_FILE_OFFSET64    1
 365 #endif
 366
 367 #if defined _DEFAULT_SOURCE
 368 # define __USE_MISC     1
 369 #endif
 370
 371 #ifdef  _ATFILE_SOURCE
 372 # define __USE_ATFILE   1
 373 #endif
 374
 375 #ifdef  _GNU_SOURCE
 376 # define __USE_GNU      1
 377 #endif
 378
 379 #if defined _FORTIFY_SOURCE && _FORTIFY_SOURCE > 0
 380 # if !defined __OPTIMIZE__ || __OPTIMIZE__ <= 0
 381 #  warning _FORTIFY_SOURCE requires compiling with optimization (-O)
 382 # elif !__GNUC_PREREQ (4, 1)
 383 #  warning _FORTIFY_SOURCE requires GCC 4.1 or later
 384 # elif _FORTIFY_SOURCE > 1
 385 #  define __USE_FORTIFY_LEVEL 2
 386 # else
 387 #  define __USE_FORTIFY_LEVEL 1
 388 # endif
 389 #endif
 390 #ifndef __USE_FORTIFY_LEVEL
 391 # define __USE_FORTIFY_LEVEL 0
 392 #endif
 393
 394 /* The function 'gets' existed in C89, but is impossible to use
 395    safely.  It has been removed from ISO C11 and ISO C++14.  Note: for
 396    compatibility with various implementations of <cstdio>, this test
 397    must consider only the value of __cplusplus when compiling C++.  */
 398 #if defined __cplusplus ? __cplusplus >= 201402L : defined __USE_ISOC11
 399 # define __GLIBC_USE_DEPRECATED_GETS 0
 400 #else
 401 # define __GLIBC_USE_DEPRECATED_GETS 1
 402 #endif
 403
 404 /* Get definitions of __STDC_* predefined macros, if the compiler has
 405    not preincluded this header automatically.  */
 406 #include <stdc-predef.h>
 407
 408 /* This macro indicates that the installed library is the GNU C Library.
 409    For historic reasons the value now is 6 and this will stay from now
 410    on.  The use of this variable is deprecated.  Use __GLIBC__ and
 411    __GLIBC_MINOR__ now (see below) when you want to test for a specific
 412    GNU C library version and use the values in <gnu/lib-names.h> to get
 413    the sonames of the shared libraries.  */
 414 #undef  __GNU_LIBRARY__
 415 #define __GNU_LIBRARY__ 6
 416
 417 /* Major and minor version number of the GNU C library package.  Use
 418    these macros to test for features in specific releases.  */
 419 #define __GLIBC__       2
 420 #define __GLIBC_MINOR__ 27
 421
 422 #define __GLIBC_PREREQ(maj, min) \
 423         ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
 424
 425 /* This is here only because every header file already includes this one.  */
 426 #ifndef __ASSEMBLER__
 427 # ifndef _SYS_CDEFS_H
 428 #  include <sys/cdefs.h>
 429 # endif
 430
 431 /* If we don't have __REDIRECT, prototypes will be missing if
 432    __USE_FILE_OFFSET64 but not __USE_LARGEFILE[64]. */
 433 # if defined __USE_FILE_OFFSET64 && !defined __REDIRECT
 434 #  define __USE_LARGEFILE       1
 435 #  define __USE_LARGEFILE64     1
 436 # endif
 437
 438 #endif  /* !ASSEMBLER */
 439
 440 /* Decide whether we can define 'extern inline' functions in headers.  */
 441 #if __GNUC_PREREQ (2, 7) && defined __OPTIMIZE__ \
 442     && !defined __OPTIMIZE_SIZE__ && !defined __NO_INLINE__ \
 443     && defined __extern_inline
 444 # define __USE_EXTERN_INLINES   1
 445 #endif
 446
 447
 448 /* This is here only because every header file already includes this one.
 449    Get the definitions of all the appropriate `__stub_FUNCTION' symbols.
 450    <gnu/stubs.h> contains `#define __stub_FUNCTION' when FUNCTION is a stub
 451    that will always return failure (and set errno to ENOSYS).  */
 452 #include <gnu/stubs.h>
 453
 454
 455 #endif  /* features.h  */