include/features.h

   1 /* Copyright (C) 1991-2025 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    <https://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    _ISOC23_SOURCE       Extensions to ISO C99 from ISO C23.
  28    _ISOC2X_SOURCE       Old name for _ISOC23_SOURCE.
  29    _ISOC2Y_SOURCE       Extensions to ISO C23 from ISO C2Y.
  30    __STDC_WANT_LIB_EXT2__
  31                         Extensions to ISO C99 from TR 27431-2:2010.
  32    __STDC_WANT_IEC_60559_BFP_EXT__
  33                         Extensions to ISO C11 from TS 18661-1:2014.
  34    __STDC_WANT_IEC_60559_FUNCS_EXT__
  35                         Extensions to ISO C11 from TS 18661-4:2015.
  36    __STDC_WANT_IEC_60559_TYPES_EXT__
  37                         Extensions to ISO C11 from TS 18661-3:2015.
  38    __STDC_WANT_IEC_60559_EXT__
  39                         ISO C23 interfaces defined only in Annex F.
  40
  41    _POSIX_SOURCE        IEEE Std 1003.1.
  42    _POSIX_C_SOURCE      If ==1, like _POSIX_SOURCE; if >=2 add IEEE Std 1003.2;
  43                         if >=199309L, add IEEE Std 1003.1b-1993;
  44                         if >=199506L, add IEEE Std 1003.1c-1995;
  45                         if >=200112L, all of IEEE 1003.1-2004
  46                         if >=200809L, all of IEEE 1003.1-2008
  47    _XOPEN_SOURCE        Includes POSIX and XPG things.  Set to 500 if
  48                         Single Unix conformance is wanted, to 600 for the
  49                         sixth revision, to 700 for the seventh revision.
  50    _XOPEN_SOURCE_EXTENDED XPG things and X/Open Unix extensions.
  51    _LARGEFILE_SOURCE    Some more functions for correct standard I/O.
  52    _LARGEFILE64_SOURCE  Additional functionality from LFS for large files.
  53    _FILE_OFFSET_BITS=N  Select default filesystem interface.
  54    _ATFILE_SOURCE       Additional *at interfaces.
  55    _DYNAMIC_STACK_SIZE_SOURCE Select correct (but non compile-time constant)
  56                         MINSIGSTKSZ, SIGSTKSZ and PTHREAD_STACK_MIN.
  57    _GNU_SOURCE          All of the above, plus GNU extensions.
  58    _DEFAULT_SOURCE      The default set of features (taking precedence over
  59                         __STRICT_ANSI__).
  60
  61    _FORTIFY_SOURCE      Add security hardening to many library functions.
  62                         Set to 1, 2 or 3; 3 performs stricter checks than 2, which
  63                         performs stricter checks than 1.
  64
  65    _REENTRANT, _THREAD_SAFE
  66                         Obsolete; equivalent to _POSIX_C_SOURCE=199506L.
  67
  68    The `-ansi' switch to the GNU C compiler, and standards conformance
  69    options such as `-std=c99', define __STRICT_ANSI__.  If none of
  70    these are defined, or if _DEFAULT_SOURCE is defined, the default is
  71    to have _POSIX_SOURCE set to one and _POSIX_C_SOURCE set to
  72    200809L, as well as enabling miscellaneous functions from BSD and
  73    SVID.  If more than one of these are defined, they accumulate.  For
  74    example __STRICT_ANSI__, _POSIX_SOURCE and _POSIX_C_SOURCE together
  75    give you ISO C, 1003.1, and 1003.2, but nothing else.
  76
  77    These are defined by this file and are used by the
  78    header files to decide what to declare or define:
  79
  80    __GLIBC_USE (F)      Define things from feature set F.  This is defined
  81                         to 1 or 0; the subsequent macros are either defined
  82                         or undefined, and those tests should be moved to
  83                         __GLIBC_USE.
  84    __USE_ISOC11         Define ISO C11 things.
  85    __USE_ISOC99         Define ISO C99 things.
  86    __USE_ISOC95         Define ISO C90 AMD1 (C95) things.
  87    __USE_ISOCXX11       Define ISO C++11 things.
  88    __USE_POSIX          Define IEEE Std 1003.1 things.
  89    __USE_POSIX2         Define IEEE Std 1003.2 things.
  90    __USE_POSIX199309    Define IEEE Std 1003.1, and .1b things.
  91    __USE_POSIX199506    Define IEEE Std 1003.1, .1b, .1c and .1i things.
  92    __USE_XOPEN          Define XPG things.
  93    __USE_XOPEN_EXTENDED Define X/Open Unix things.
  94    __USE_UNIX98         Define Single Unix V2 things.
  95    __USE_XOPEN2K        Define XPG6 things.
  96    __USE_XOPEN2KXSI     Define XPG6 XSI things.
  97    __USE_XOPEN2K8       Define XPG7 things.
  98    __USE_XOPEN2K8XSI    Define XPG7 XSI things.
  99    __USE_LARGEFILE      Define correct standard I/O things.
 100    __USE_LARGEFILE64    Define LFS things with separate names.
 101    __USE_FILE_OFFSET64  Define 64bit interface as default.
 102    __USE_MISC           Define things from 4.3BSD or System V Unix.
 103    __USE_ATFILE         Define *at interfaces and AT_* constants for them.
 104    __USE_DYNAMIC_STACK_SIZE Define correct (but non compile-time constant)
 105                         MINSIGSTKSZ, SIGSTKSZ and PTHREAD_STACK_MIN.
 106    __USE_GNU            Define GNU extensions.
 107    __USE_FORTIFY_LEVEL  Additional security measures used, according to level.
 108
 109    The macros `__GNU_LIBRARY__', `__GLIBC__', and `__GLIBC_MINOR__' are
 110    defined by this file unconditionally.  `__GNU_LIBRARY__' is provided
 111    only for compatibility.  All new code should use the other symbols
 112    to test for features.
 113
 114    All macros listed above as possibly being defined by this file are
 115    explicitly undefined if they are not explicitly defined.
 116    Feature-test macros that are not defined by the user or compiler
 117    but are implied by the other feature-test macros defined (or by the
 118    lack of any definitions) are defined by the file.
 119
 120    ISO C feature test macros depend on the definition of the macro
 121    when an affected header is included, not when the first system
 122    header is included, and so they are handled in
 123    <bits/libc-header-start.h>, which does not have a multiple include
 124    guard.  Feature test macros that can be handled from the first
 125    system header included are handled here.  */
 126
 127
 128 /* Undefine everything, so we get a clean slate.  */
 129 #undef  __USE_ISOC11
 130 #undef  __USE_ISOC99
 131 #undef  __USE_ISOC95
 132 #undef  __USE_ISOCXX11
 133 #undef  __USE_POSIX
 134 #undef  __USE_POSIX2
 135 #undef  __USE_POSIX199309
 136 #undef  __USE_POSIX199506
 137 #undef  __USE_XOPEN
 138 #undef  __USE_XOPEN_EXTENDED
 139 #undef  __USE_UNIX98
 140 #undef  __USE_XOPEN2K
 141 #undef  __USE_XOPEN2KXSI
 142 #undef  __USE_XOPEN2K8
 143 #undef  __USE_XOPEN2K8XSI
 144 #undef  __USE_LARGEFILE
 145 #undef  __USE_LARGEFILE64
 146 #undef  __USE_FILE_OFFSET64
 147 #undef  __USE_MISC
 148 #undef  __USE_ATFILE
 149 #undef  __USE_DYNAMIC_STACK_SIZE
 150 #undef  __USE_GNU
 151 #undef  __USE_FORTIFY_LEVEL
 152 #undef  __KERNEL_STRICT_NAMES
 153 #undef  __GLIBC_USE_ISOC23
 154 #undef  __GLIBC_USE_ISOC2Y
 155 #undef  __GLIBC_USE_DEPRECATED_GETS
 156 #undef  __GLIBC_USE_DEPRECATED_SCANF
 157 #undef  __GLIBC_USE_C23_STRTOL
 158
 159 /* Suppress kernel-name space pollution unless user expressedly asks
 160    for it.  */
 161 #ifndef _LOOSE_KERNEL_NAMES
 162 # define __KERNEL_STRICT_NAMES
 163 #endif
 164
 165 /* Convenience macro to test the version of gcc.
 166    Use like this:
 167    #if __GNUC_PREREQ (2,8)
 168    ... code requiring gcc 2.8 or later ...
 169    #endif
 170    Note: only works for GCC 2.0 and later, because __GNUC_MINOR__ was
 171    added in 2.0.  */
 172 #if defined __GNUC__ && defined __GNUC_MINOR__
 173 # define __GNUC_PREREQ(maj, min) \
 174         ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min))
 175 #else
 176 # define __GNUC_PREREQ(maj, min) 0
 177 #endif
 178
 179 /* Similarly for clang.  Features added to GCC after version 4.2 may
 180    or may not also be available in clang, and clang's definitions of
 181    __GNUC(_MINOR)__ are fixed at 4 and 2 respectively.  Not all such
 182    features can be queried via __has_extension/__has_feature.  */
 183 #if defined __clang_major__ && defined __clang_minor__
 184 # define __glibc_clang_prereq(maj, min) \
 185   ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
 186 #else
 187 # define __glibc_clang_prereq(maj, min) 0
 188 #endif
 189
 190 /* Whether to use feature set F.  */
 191 #define __GLIBC_USE(F)  __GLIBC_USE_ ## F
 192
 193 /* _BSD_SOURCE and _SVID_SOURCE are deprecated aliases for
 194    _DEFAULT_SOURCE.  If _DEFAULT_SOURCE is present we do not
 195    issue a warning; the expectation is that the source is being
 196    transitioned to use the new macro.  */
 197 #if (defined _BSD_SOURCE || defined _SVID_SOURCE) \
 198     && !defined _DEFAULT_SOURCE
 199 # warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
 200 # undef  _DEFAULT_SOURCE
 201 # define _DEFAULT_SOURCE        1
 202 #endif
 203
 204 /* Remap the old name _ISOC2X_SOURCE to _ISOC23_SOURCE.  */
 205 #ifdef _ISOC2X_SOURCE
 206 # undef _ISOC2X_SOURCE
 207 # undef _ISOC23_SOURCE
 208 # define _ISOC23_SOURCE 1
 209 #endif
 210
 211 /* If _GNU_SOURCE was defined by the user, turn on all the other features.  */
 212 #ifdef _GNU_SOURCE
 213 # undef  _ISOC95_SOURCE
 214 # define _ISOC95_SOURCE 1
 215 # undef  _ISOC99_SOURCE
 216 # define _ISOC99_SOURCE 1
 217 # undef  _ISOC11_SOURCE
 218 # define _ISOC11_SOURCE 1
 219 # undef  _ISOC23_SOURCE
 220 # define _ISOC23_SOURCE 1
 221 # undef  _ISOC2Y_SOURCE
 222 # define _ISOC2Y_SOURCE 1
 223 # undef  _POSIX_SOURCE
 224 # define _POSIX_SOURCE  1
 225 # undef  _POSIX_C_SOURCE
 226 # define _POSIX_C_SOURCE        200809L
 227 # undef  _XOPEN_SOURCE
 228 # define _XOPEN_SOURCE  700
 229 # undef  _XOPEN_SOURCE_EXTENDED
 230 # define _XOPEN_SOURCE_EXTENDED 1
 231 # undef  _LARGEFILE64_SOURCE
 232 # define _LARGEFILE64_SOURCE    1
 233 # undef  _DEFAULT_SOURCE
 234 # define _DEFAULT_SOURCE        1
 235 # undef  _ATFILE_SOURCE
 236 # define _ATFILE_SOURCE 1
 237 # undef  _DYNAMIC_STACK_SIZE_SOURCE
 238 # define _DYNAMIC_STACK_SIZE_SOURCE 1
 239 #endif
 240
 241 /* If nothing (other than _GNU_SOURCE and _DEFAULT_SOURCE) is defined,
 242    define _DEFAULT_SOURCE.  */
 243 #if (defined _DEFAULT_SOURCE                                    \
 244      || (!defined __STRICT_ANSI__                               \
 245          && !defined _ISOC99_SOURCE && !defined _ISOC11_SOURCE  \
 246          && !defined _ISOC23_SOURCE && !defined _ISOC2Y_SOURCE  \
 247          && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE  \
 248          && !defined _XOPEN_SOURCE))
 249 # undef  _DEFAULT_SOURCE
 250 # define _DEFAULT_SOURCE        1
 251 #endif
 252
 253 /* This is to enable the ISO C2Y extension.  */
 254 #if (defined _ISOC2Y_SOURCE \
 255      || (defined __STDC_VERSION__ && __STDC_VERSION__ > 202311L))
 256 # define __GLIBC_USE_ISOC2Y     1
 257 #else
 258 # define __GLIBC_USE_ISOC2Y     0
 259 #endif
 260
 261 /* This is to enable the ISO C23 extension.  */
 262 #if (defined _ISOC23_SOURCE || defined _ISOC2Y_SOURCE \
 263      || (defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L))
 264 # define __GLIBC_USE_ISOC23     1
 265 #else
 266 # define __GLIBC_USE_ISOC23     0
 267 #endif
 268
 269 /* This is to enable the ISO C11 extension.  */
 270 #if (defined _ISOC11_SOURCE || defined _ISOC23_SOURCE   \
 271      || defined _ISOC2Y_SOURCE                          \
 272      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L))
 273 # define __USE_ISOC11   1
 274 #endif
 275
 276 /* This is to enable the ISO C99 extension.  */
 277 #if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE                   \
 278      || defined _ISOC23_SOURCE || defined _ISOC2Y_SOURCE                \
 279      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L))
 280 # define __USE_ISOC99   1
 281 #endif
 282
 283 /* This is to enable the ISO C90 Amendment 1:1995 extension.  */
 284 #if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE                   \
 285      || defined _ISOC23_SOURCE || defined _ISOC2Y_SOURCE                \
 286      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199409L))
 287 # define __USE_ISOC95   1
 288 #endif
 289
 290 #ifdef __cplusplus
 291 /* This is to enable compatibility for ISO C++17.  */
 292 # if __cplusplus >= 201703L
 293 #  define __USE_ISOC11  1
 294 # endif
 295 /* This is to enable compatibility for ISO C++11.
 296    Check the temporary macro for now, too.  */
 297 # if __cplusplus >= 201103L || defined __GXX_EXPERIMENTAL_CXX0X__
 298 #  define __USE_ISOCXX11        1
 299 #  define __USE_ISOC99  1
 300 # endif
 301 #endif
 302
 303 /* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE
 304    is defined, use POSIX.1-2008 (or another version depending on
 305    _XOPEN_SOURCE).  */
 306 #ifdef _DEFAULT_SOURCE
 307 # if !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE
 308 #  define __USE_POSIX_IMPLICITLY        1
 309 # endif
 310 # undef  _POSIX_SOURCE
 311 # define _POSIX_SOURCE  1
 312 # undef  _POSIX_C_SOURCE
 313 # define _POSIX_C_SOURCE        200809L
 314 #endif
 315
 316 #if ((!defined __STRICT_ANSI__                                  \
 317       || (defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) >= 500)) \
 318      && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE)
 319 # define _POSIX_SOURCE  1
 320 # if defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 500
 321 #  define _POSIX_C_SOURCE       2
 322 # elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 600
 323 #  define _POSIX_C_SOURCE       199506L
 324 # elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 700
 325 #  define _POSIX_C_SOURCE       200112L
 326 # else
 327 #  define _POSIX_C_SOURCE       200809L
 328 # endif
 329 # define __USE_POSIX_IMPLICITLY 1
 330 #endif
 331
 332 /* Some C libraries once required _REENTRANT and/or _THREAD_SAFE to be
 333    defined in all multithreaded code.  GNU libc has not required this
 334    for many years.  We now treat them as compatibility synonyms for
 335    _POSIX_C_SOURCE=199506L, which is the earliest level of POSIX with
 336    comprehensive support for multithreaded code.  Using them never
 337    lowers the selected level of POSIX conformance, only raises it.  */
 338 #if ((!defined _POSIX_C_SOURCE || (_POSIX_C_SOURCE - 0) < 199506L) \
 339      && (defined _REENTRANT || defined _THREAD_SAFE))
 340 # define _POSIX_SOURCE   1
 341 # undef  _POSIX_C_SOURCE
 342 # define _POSIX_C_SOURCE 199506L
 343 #endif
 344
 345 #if (defined _POSIX_SOURCE                                      \
 346      || (defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 1)       \
 347      || defined _XOPEN_SOURCE)
 348 # define __USE_POSIX    1
 349 #endif
 350
 351 #if defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 2 || defined _XOPEN_SOURCE
 352 # define __USE_POSIX2   1
 353 #endif
 354
 355 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199309L
 356 # define __USE_POSIX199309      1
 357 #endif
 358
 359 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199506L
 360 # define __USE_POSIX199506      1
 361 #endif
 362
 363 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200112L
 364 # define __USE_XOPEN2K          1
 365 # undef __USE_ISOC95
 366 # define __USE_ISOC95           1
 367 # undef __USE_ISOC99
 368 # define __USE_ISOC99           1
 369 #endif
 370
 371 #if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200809L
 372 # define __USE_XOPEN2K8         1
 373 # undef  _ATFILE_SOURCE
 374 # define _ATFILE_SOURCE 1
 375 #endif
 376
 377 #ifdef  _XOPEN_SOURCE
 378 # define __USE_XOPEN    1
 379 # if (_XOPEN_SOURCE - 0) >= 500
 380 #  define __USE_XOPEN_EXTENDED  1
 381 #  define __USE_UNIX98  1
 382 #  undef _LARGEFILE_SOURCE
 383 #  define _LARGEFILE_SOURCE     1
 384 #  if (_XOPEN_SOURCE - 0) >= 600
 385 #   if (_XOPEN_SOURCE - 0) >= 700
 386 #    define __USE_XOPEN2K8      1
 387 #    define __USE_XOPEN2K8XSI   1
 388 #   endif
 389 #   define __USE_XOPEN2K        1
 390 #   define __USE_XOPEN2KXSI     1
 391 #   undef __USE_ISOC95
 392 #   define __USE_ISOC95         1
 393 #   undef __USE_ISOC99
 394 #   define __USE_ISOC99         1
 395 #  endif
 396 # else
 397 #  ifdef _XOPEN_SOURCE_EXTENDED
 398 #   define __USE_XOPEN_EXTENDED 1
 399 #  endif
 400 # endif
 401 #endif
 402
 403 #ifdef _LARGEFILE_SOURCE
 404 # define __USE_LARGEFILE        1
 405 #endif
 406
 407 #ifdef _LARGEFILE64_SOURCE
 408 # define __USE_LARGEFILE64      1
 409 #endif
 410
 411 #if defined _FILE_OFFSET_BITS && _FILE_OFFSET_BITS == 64
 412 # define __USE_FILE_OFFSET64    1
 413 #endif
 414
 415 #include <features-time64.h>
 416
 417 #if defined _DEFAULT_SOURCE
 418 # define __USE_MISC     1
 419 #endif
 420
 421 #ifdef  _ATFILE_SOURCE
 422 # define __USE_ATFILE   1
 423 #endif
 424
 425 #ifdef  _DYNAMIC_STACK_SIZE_SOURCE
 426 # define __USE_DYNAMIC_STACK_SIZE       1
 427 #endif
 428
 429 #ifdef  _GNU_SOURCE
 430 # define __USE_GNU      1
 431 #endif
 432
 433 #if defined _FORTIFY_SOURCE && _FORTIFY_SOURCE > 0
 434 # if !defined __OPTIMIZE__ || __OPTIMIZE__ <= 0
 435 #  warning _FORTIFY_SOURCE requires compiling with optimization (-O)
 436 # elif !__GNUC_PREREQ (4, 1)
 437 #  warning _FORTIFY_SOURCE requires GCC 4.1 or later
 438 # elif _FORTIFY_SOURCE > 2 && (__glibc_clang_prereq (9, 0)                    \
 439                                || __GNUC_PREREQ (12, 0))
 440
 441 #  if _FORTIFY_SOURCE > 3
 442 #   warning _FORTIFY_SOURCE > 3 is treated like 3 on this platform
 443 #  endif
 444 #  define __USE_FORTIFY_LEVEL 3
 445 # elif _FORTIFY_SOURCE > 1
 446 #  if _FORTIFY_SOURCE > 2
 447 #   warning _FORTIFY_SOURCE > 2 is treated like 2 on this platform
 448 #  endif
 449 #  define __USE_FORTIFY_LEVEL 2
 450 # else
 451 #  define __USE_FORTIFY_LEVEL 1
 452 # endif
 453 #endif
 454 #ifndef __USE_FORTIFY_LEVEL
 455 # define __USE_FORTIFY_LEVEL 0
 456 #endif
 457
 458 /* The function 'gets' existed in C89, but is impossible to use
 459    safely.  It has been removed from ISO C11 and ISO C++14.  Note: for
 460    compatibility with various implementations of <cstdio>, this test
 461    must consider only the value of __cplusplus when compiling C++.  */
 462 #if defined __cplusplus ? __cplusplus >= 201402L : defined __USE_ISOC11
 463 # define __GLIBC_USE_DEPRECATED_GETS 0
 464 #else
 465 # define __GLIBC_USE_DEPRECATED_GETS 1
 466 #endif
 467
 468 /* GNU formerly extended the scanf functions with modified format
 469    specifiers %as, %aS, and %a[...] that allocate a buffer for the
 470    input using malloc.  This extension conflicts with ISO C99, which
 471    defines %a as a standalone format specifier that reads a floating-
 472    point number; moreover, POSIX.1-2008 provides the same feature
 473    using the modifier letter 'm' instead (%ms, %mS, %m[...]).
 474
 475    We now follow C99 unless GNU extensions are active and the compiler
 476    is specifically in C89 or C++98 mode (strict or not).  For
 477    instance, with GCC, -std=gnu11 will have C99-compliant scanf with
 478    or without -D_GNU_SOURCE, but -std=c89 -D_GNU_SOURCE will have the
 479    old extension.  */
 480 #if (defined __USE_GNU                                                  \
 481      && (defined __cplusplus                                            \
 482          ? (__cplusplus < 201103L && !defined __GXX_EXPERIMENTAL_CXX0X__) \
 483          : (!defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L)))
 484 # define __GLIBC_USE_DEPRECATED_SCANF 1
 485 #else
 486 # define __GLIBC_USE_DEPRECATED_SCANF 0
 487 #endif
 488
 489 /* ISO C23 added support for a 0b or 0B prefix on binary constants as
 490    inputs to strtol-family functions (base 0 or 2).  This macro is
 491    used to condition redirection in headers to allow that redirection
 492    to be disabled when building those functions, despite _GNU_SOURCE
 493    being defined.  */
 494 #if __GLIBC_USE (ISOC23)
 495 # define __GLIBC_USE_C23_STRTOL 1
 496 #else
 497 # define __GLIBC_USE_C23_STRTOL 0
 498 #endif
 499
 500 /* Get definitions of __STDC_* predefined macros, if the compiler has
 501    not preincluded this header automatically.  */
 502 #include <stdc-predef.h>
 503
 504 /* This macro indicates that the installed library is the GNU C Library.
 505    For historic reasons the value now is 6 and this will stay from now
 506    on.  The use of this variable is deprecated.  Use __GLIBC__ and
 507    __GLIBC_MINOR__ now (see below) when you want to test for a specific
 508    GNU C library version and use the values in <gnu/lib-names.h> to get
 509    the sonames of the shared libraries.  */
 510 #undef  __GNU_LIBRARY__
 511 #define __GNU_LIBRARY__ 6
 512
 513 /* Major and minor version number of the GNU C library package.  Use
 514    these macros to test for features in specific releases.  */
 515 #define __GLIBC__       2
 516 #define __GLIBC_MINOR__ 41
 517
 518 #define __GLIBC_PREREQ(maj, min) \
 519         ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min))
 520
 521 /* This is here only because every header file already includes this one.  */
 522 #ifndef __ASSEMBLER__
 523 # ifndef _SYS_CDEFS_H
 524 #  include <sys/cdefs.h>
 525 # endif
 526
 527 /* If we don't have __REDIRECT, prototypes will be missing if
 528    __USE_FILE_OFFSET64 but not __USE_LARGEFILE[64]. */
 529 # if defined __USE_FILE_OFFSET64 && !defined __REDIRECT
 530 #  define __USE_LARGEFILE       1
 531 #  define __USE_LARGEFILE64     1
 532 # endif
 533
 534 #endif  /* !ASSEMBLER */
 535
 536 /* Decide whether we can define 'extern inline' functions in headers.  */
 537 #if __GNUC_PREREQ (2, 7) && defined __OPTIMIZE__ \
 538     && !defined __OPTIMIZE_SIZE__ && !defined __NO_INLINE__ \
 539     && defined __extern_inline
 540 # define __USE_EXTERN_INLINES   1
 541 #endif
 542
 543
 544 /* This is here only because every header file already includes this one.
 545    Get the definitions of all the appropriate `__stub_FUNCTION' symbols.
 546    <gnu/stubs.h> contains `#define __stub_FUNCTION' when FUNCTION is a stub
 547    that will always return failure (and set errno to ENOSYS).  */
 548 #include <gnu/stubs.h>
 549
 550
 551 #endif  /* features.h  */