1/* Copyright (C) 1991-2020 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 _ISOC2X_SOURCE Extensions to ISO C99 from ISO C2X. 
28 __STDC_WANT_LIB_EXT2__ 
29 Extensions to ISO C99 from TR 27431-2:2010. 
30 __STDC_WANT_IEC_60559_BFP_EXT__ 
31 Extensions to ISO C11 from TS 18661-1:2014. 
32 __STDC_WANT_IEC_60559_FUNCS_EXT__ 
33 Extensions to ISO C11 from TS 18661-4:2015. 
34 __STDC_WANT_IEC_60559_TYPES_EXT__ 
35 Extensions to ISO C11 from TS 18661-3:2015. 
36 
37 _POSIX_SOURCE IEEE Std 1003.1. 
38 _POSIX_C_SOURCE If ==1, like _POSIX_SOURCE; if >=2 add IEEE Std 1003.2; 
39 if >=199309L, add IEEE Std 1003.1b-1993; 
40 if >=199506L, add IEEE Std 1003.1c-1995; 
41 if >=200112L, all of IEEE 1003.1-2004 
42 if >=200809L, all of IEEE 1003.1-2008 
43 _XOPEN_SOURCE Includes POSIX and XPG things. Set to 500 if 
44 Single Unix conformance is wanted, to 600 for the 
45 sixth revision, to 700 for the seventh revision. 
46 _XOPEN_SOURCE_EXTENDED XPG things and X/Open Unix extensions. 
47 _LARGEFILE_SOURCE Some more functions for correct standard I/O. 
48 _LARGEFILE64_SOURCE Additional functionality from LFS for large files. 
49 _FILE_OFFSET_BITS=N Select default filesystem interface. 
50 _ATFILE_SOURCE Additional *at interfaces. 
51 _GNU_SOURCE All of the above, plus GNU extensions. 
52 _DEFAULT_SOURCE The default set of features (taking precedence over 
53 __STRICT_ANSI__). 
54 
55 _FORTIFY_SOURCE Add security hardening to many library functions. 
56 Set to 1 or 2; 2 performs stricter checks than 1. 
57 
58 _REENTRANT, _THREAD_SAFE 
59 Obsolete; equivalent to _POSIX_C_SOURCE=199506L. 
60 
61 The `-ansi' switch to the GNU C compiler, and standards conformance 
62 options such as `-std=c99', define __STRICT_ANSI__. If none of 
63 these are defined, or if _DEFAULT_SOURCE is defined, the default is 
64 to have _POSIX_SOURCE set to one and _POSIX_C_SOURCE set to 
65 200809L, as well as enabling miscellaneous functions from BSD and 
66 SVID. If more than one of these are defined, they accumulate. For 
67 example __STRICT_ANSI__, _POSIX_SOURCE and _POSIX_C_SOURCE together 
68 give you ISO C, 1003.1, and 1003.2, but nothing else. 
69 
70 These are defined by this file and are used by the 
71 header files to decide what to declare or define: 
72 
73 __GLIBC_USE (F) Define things from feature set F. This is defined 
74 to 1 or 0; the subsequent macros are either defined 
75 or undefined, and those tests should be moved to 
76 __GLIBC_USE. 
77 __USE_ISOC11 Define ISO C11 things. 
78 __USE_ISOC99 Define ISO C99 things. 
79 __USE_ISOC95 Define ISO C90 AMD1 (C95) things. 
80 __USE_ISOCXX11 Define ISO C++11 things. 
81 __USE_POSIX Define IEEE Std 1003.1 things. 
82 __USE_POSIX2 Define IEEE Std 1003.2 things. 
83 __USE_POSIX199309 Define IEEE Std 1003.1, and .1b things. 
84 __USE_POSIX199506 Define IEEE Std 1003.1, .1b, .1c and .1i things. 
85 __USE_XOPEN Define XPG things. 
86 __USE_XOPEN_EXTENDED Define X/Open Unix things. 
87 __USE_UNIX98 Define Single Unix V2 things. 
88 __USE_XOPEN2K Define XPG6 things. 
89 __USE_XOPEN2KXSI Define XPG6 XSI things. 
90 __USE_XOPEN2K8 Define XPG7 things. 
91 __USE_XOPEN2K8XSI Define XPG7 XSI things. 
92 __USE_LARGEFILE Define correct standard I/O things. 
93 __USE_LARGEFILE64 Define LFS things with separate names. 
94 __USE_FILE_OFFSET64 Define 64bit interface as default. 
95 __USE_MISC Define things from 4.3BSD or System V Unix. 
96 __USE_ATFILE Define *at interfaces and AT_* constants for them. 
97 __USE_GNU Define GNU extensions. 
98 __USE_FORTIFY_LEVEL Additional security measures used, according to level. 
99 
100 The macros `__GNU_LIBRARY__', `__GLIBC__', and `__GLIBC_MINOR__' are 
101 defined by this file unconditionally. `__GNU_LIBRARY__' is provided 
102 only for compatibility. All new code should use the other symbols 
103 to test for features. 
104 
105 All macros listed above as possibly being defined by this file are 
106 explicitly undefined if they are not explicitly defined. 
107 Feature-test macros that are not defined by the user or compiler 
108 but are implied by the other feature-test macros defined (or by the 
109 lack of any definitions) are defined by the file. 
110 
111 ISO C feature test macros depend on the definition of the macro 
112 when an affected header is included, not when the first system 
113 header is included, and so they are handled in 
114 <bits/libc-header-start.h>, which does not have a multiple include 
115 guard. Feature test macros that can be handled from the first 
116 system header included are handled here. */ 
117 
118 
119/* Undefine everything, so we get a clean slate. */ 
120#undef __USE_ISOC11 
121#undef __USE_ISOC99 
122#undef __USE_ISOC95 
123#undef __USE_ISOCXX11 
124#undef __USE_POSIX 
125#undef __USE_POSIX2 
126#undef __USE_POSIX199309 
127#undef __USE_POSIX199506 
128#undef __USE_XOPEN 
129#undef __USE_XOPEN_EXTENDED 
130#undef __USE_UNIX98 
131#undef __USE_XOPEN2K 
132#undef __USE_XOPEN2KXSI 
133#undef __USE_XOPEN2K8 
134#undef __USE_XOPEN2K8XSI 
135#undef __USE_LARGEFILE 
136#undef __USE_LARGEFILE64 
137#undef __USE_FILE_OFFSET64 
138#undef __USE_MISC 
139#undef __USE_ATFILE 
140#undef __USE_GNU 
141#undef __USE_FORTIFY_LEVEL 
142#undef __KERNEL_STRICT_NAMES 
143#undef __GLIBC_USE_ISOC2X 
144#undef __GLIBC_USE_DEPRECATED_GETS 
145#undef __GLIBC_USE_DEPRECATED_SCANF 
146 
147/* Suppress kernel-name space pollution unless user expressedly asks 
148 for it. */ 
149#ifndef _LOOSE_KERNEL_NAMES 
150# define __KERNEL_STRICT_NAMES 
151#endif 
152 
153/* Convenience macro to test the version of gcc. 
154 Use like this: 
155 #if __GNUC_PREREQ (2,8) 
156 ... code requiring gcc 2.8 or later ... 
157 #endif 
158 Note: only works for GCC 2.0 and later, because __GNUC_MINOR__ was 
159 added in 2.0. */ 
160#if defined __GNUC__ && defined __GNUC_MINOR__ 
161# define __GNUC_PREREQ(maj, min) \ 
162 ((__GNUC__ << 16) + __GNUC_MINOR__ >= ((maj) << 16) + (min)) 
163#else 
164# define __GNUC_PREREQ(maj, min) 0 
165#endif 
166 
167/* Similarly for clang. Features added to GCC after version 4.2 may 
168 or may not also be available in clang, and clang's definitions of 
169 __GNUC(_MINOR)__ are fixed at 4 and 2 respectively. Not all such 
170 features can be queried via __has_extension/__has_feature. */ 
171#if defined __clang_major__ && defined __clang_minor__ 
172# define __glibc_clang_prereq(maj, min) \ 
173 ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min)) 
174#else 
175# define __glibc_clang_prereq(maj, min) 0 
176#endif 
177 
178/* Whether to use feature set F. */ 
179#define __GLIBC_USE(F) __GLIBC_USE_ ## F 
180 
181/* _BSD_SOURCE and _SVID_SOURCE are deprecated aliases for 
182 _DEFAULT_SOURCE. If _DEFAULT_SOURCE is present we do not 
183 issue a warning; the expectation is that the source is being 
184 transitioned to use the new macro. */ 
185#if (defined _BSD_SOURCE || defined _SVID_SOURCE) \ 
186 && !defined _DEFAULT_SOURCE 
187# warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE" 
188# undef _DEFAULT_SOURCE 
189# define _DEFAULT_SOURCE 1 
190#endif 
191 
192/* If _GNU_SOURCE was defined by the user, turn on all the other features. */ 
193#ifdef _GNU_SOURCE 
194# undef _ISOC95_SOURCE 
195# define _ISOC95_SOURCE 1 
196# undef _ISOC99_SOURCE 
197# define _ISOC99_SOURCE 1 
198# undef _ISOC11_SOURCE 
199# define _ISOC11_SOURCE 1 
200# undef _ISOC2X_SOURCE 
201# define _ISOC2X_SOURCE 1 
202# undef _POSIX_SOURCE 
203# define _POSIX_SOURCE 1 
204# undef _POSIX_C_SOURCE 
205# define _POSIX_C_SOURCE 200809L 
206# undef _XOPEN_SOURCE 
207# define _XOPEN_SOURCE 700 
208# undef _XOPEN_SOURCE_EXTENDED 
209# define _XOPEN_SOURCE_EXTENDED 1 
210# undef _LARGEFILE64_SOURCE 
211# define _LARGEFILE64_SOURCE 1 
212# undef _DEFAULT_SOURCE 
213# define _DEFAULT_SOURCE 1 
214# undef _ATFILE_SOURCE 
215# define _ATFILE_SOURCE 1 
216#endif 
217 
218/* If nothing (other than _GNU_SOURCE and _DEFAULT_SOURCE) is defined, 
219 define _DEFAULT_SOURCE. */ 
220#if (defined _DEFAULT_SOURCE \ 
221 || (!defined __STRICT_ANSI__ \ 
222 && !defined _ISOC99_SOURCE && !defined _ISOC11_SOURCE \ 
223 && !defined _ISOC2X_SOURCE \ 
224 && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE \ 
225 && !defined _XOPEN_SOURCE)) 
226# undef _DEFAULT_SOURCE 
227# define _DEFAULT_SOURCE 1 
228#endif 
229 
230/* This is to enable the ISO C2X extension. */ 
231#if (defined _ISOC2X_SOURCE \ 
232 || (defined __STDC_VERSION__ && __STDC_VERSION__ > 201710L)) 
233# define __GLIBC_USE_ISOC2X 1 
234#else 
235# define __GLIBC_USE_ISOC2X 0 
236#endif 
237 
238/* This is to enable the ISO C11 extension. */ 
239#if (defined _ISOC11_SOURCE || defined _ISOC2X_SOURCE \ 
240 || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L)) 
241# define __USE_ISOC11 1 
242#endif 
243 
244/* This is to enable the ISO C99 extension. */ 
245#if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE \ 
246 || defined _ISOC2X_SOURCE \ 
247 || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L)) 
248# define __USE_ISOC99 1 
249#endif 
250 
251/* This is to enable the ISO C90 Amendment 1:1995 extension. */ 
252#if (defined _ISOC99_SOURCE || defined _ISOC11_SOURCE \ 
253 || defined _ISOC2X_SOURCE \ 
254 || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 199409L)) 
255# define __USE_ISOC95 1 
256#endif 
257 
258#ifdef __cplusplus 
259/* This is to enable compatibility for ISO C++17. */ 
260# if __cplusplus >= 201703L 
261# define __USE_ISOC11 1 
262# endif 
263/* This is to enable compatibility for ISO C++11. 
264 Check the temporary macro for now, too. */ 
265# if __cplusplus >= 201103L || defined __GXX_EXPERIMENTAL_CXX0X__ 
266# define __USE_ISOCXX11 1 
267# define __USE_ISOC99 1 
268# endif 
269#endif 
270 
271/* If none of the ANSI/POSIX macros are defined, or if _DEFAULT_SOURCE 
272 is defined, use POSIX.1-2008 (or another version depending on 
273 _XOPEN_SOURCE). */ 
274#ifdef _DEFAULT_SOURCE 
275# if !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE 
276# define __USE_POSIX_IMPLICITLY 1 
277# endif 
278# undef _POSIX_SOURCE 
279# define _POSIX_SOURCE 1 
280# undef _POSIX_C_SOURCE 
281# define _POSIX_C_SOURCE 200809L 
282#endif 
283 
284#if ((!defined __STRICT_ANSI__ \ 
285 || (defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) >= 500)) \ 
286 && !defined _POSIX_SOURCE && !defined _POSIX_C_SOURCE) 
287# define _POSIX_SOURCE 1 
288# if defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 500 
289# define _POSIX_C_SOURCE 2 
290# elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 600 
291# define _POSIX_C_SOURCE 199506L 
292# elif defined _XOPEN_SOURCE && (_XOPEN_SOURCE - 0) < 700 
293# define _POSIX_C_SOURCE 200112L 
294# else 
295# define _POSIX_C_SOURCE 200809L 
296# endif 
297# define __USE_POSIX_IMPLICITLY 1 
298#endif 
299 
300/* Some C libraries once required _REENTRANT and/or _THREAD_SAFE to be 
301 defined in all multithreaded code. GNU libc has not required this 
302 for many years. We now treat them as compatibility synonyms for 
303 _POSIX_C_SOURCE=199506L, which is the earliest level of POSIX with 
304 comprehensive support for multithreaded code. Using them never 
305 lowers the selected level of POSIX conformance, only raises it. */ 
306#if ((!defined _POSIX_C_SOURCE || (_POSIX_C_SOURCE - 0) < 199506L) \ 
307 && (defined _REENTRANT || defined _THREAD_SAFE)) 
308# define _POSIX_SOURCE 1 
309# undef _POSIX_C_SOURCE 
310# define _POSIX_C_SOURCE 199506L 
311#endif 
312 
313#if (defined _POSIX_SOURCE \ 
314 || (defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 1) \ 
315 || defined _XOPEN_SOURCE) 
316# define __USE_POSIX 1 
317#endif 
318 
319#if defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 2 || defined _XOPEN_SOURCE 
320# define __USE_POSIX2 1 
321#endif 
322 
323#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199309L 
324# define __USE_POSIX199309 1 
325#endif 
326 
327#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 199506L 
328# define __USE_POSIX199506 1 
329#endif 
330 
331#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200112L 
332# define __USE_XOPEN2K 1 
333# undef __USE_ISOC95 
334# define __USE_ISOC95 1 
335# undef __USE_ISOC99 
336# define __USE_ISOC99 1 
337#endif 
338 
339#if defined _POSIX_C_SOURCE && (_POSIX_C_SOURCE - 0) >= 200809L 
340# define __USE_XOPEN2K8 1 
341# undef _ATFILE_SOURCE 
342# define _ATFILE_SOURCE 1 
343#endif 
344 
345#ifdef _XOPEN_SOURCE 
346# define __USE_XOPEN 1 
347# if (_XOPEN_SOURCE - 0) >= 500 
348# define __USE_XOPEN_EXTENDED 1 
349# define __USE_UNIX98 1 
350# undef _LARGEFILE_SOURCE 
351# define _LARGEFILE_SOURCE 1 
352# if (_XOPEN_SOURCE - 0) >= 600 
353# if (_XOPEN_SOURCE - 0) >= 700 
354# define __USE_XOPEN2K8 1 
355# define __USE_XOPEN2K8XSI 1 
356# endif 
357# define __USE_XOPEN2K 1 
358# define __USE_XOPEN2KXSI 1 
359# undef __USE_ISOC95 
360# define __USE_ISOC95 1 
361# undef __USE_ISOC99 
362# define __USE_ISOC99 1 
363# endif 
364# else 
365# ifdef _XOPEN_SOURCE_EXTENDED 
366# define __USE_XOPEN_EXTENDED 1 
367# endif 
368# endif 
369#endif 
370 
371#ifdef _LARGEFILE_SOURCE 
372# define __USE_LARGEFILE 1 
373#endif 
374 
375#ifdef _LARGEFILE64_SOURCE 
376# define __USE_LARGEFILE64 1 
377#endif 
378 
379#if defined _FILE_OFFSET_BITS && _FILE_OFFSET_BITS == 64 
380# define __USE_FILE_OFFSET64 1 
381#endif 
382 
383#if defined _DEFAULT_SOURCE 
384# define __USE_MISC 1 
385#endif 
386 
387#ifdef _ATFILE_SOURCE 
388# define __USE_ATFILE 1 
389#endif 
390 
391#ifdef _GNU_SOURCE 
392# define __USE_GNU 1 
393#endif 
394 
395#if defined _FORTIFY_SOURCE && _FORTIFY_SOURCE > 0 \ 
396 && __GNUC_PREREQ (4, 1) && defined __OPTIMIZE__ && __OPTIMIZE__ > 0 
397# if _FORTIFY_SOURCE > 1 
398# define __USE_FORTIFY_LEVEL 2 
399# else 
400# define __USE_FORTIFY_LEVEL 1 
401# endif 
402#else 
403# define __USE_FORTIFY_LEVEL 0 
404#endif 
405 
406/* The function 'gets' existed in C89, but is impossible to use 
407 safely. It has been removed from ISO C11 and ISO C++14. Note: for 
408 compatibility with various implementations of <cstdio>, this test 
409 must consider only the value of __cplusplus when compiling C++. */ 
410#if defined __cplusplus ? __cplusplus >= 201402L : defined __USE_ISOC11 
411# define __GLIBC_USE_DEPRECATED_GETS 0 
412#else 
413# define __GLIBC_USE_DEPRECATED_GETS 1 
414#endif 
415 
416/* GNU formerly extended the scanf functions with modified format 
417 specifiers %as, %aS, and %a[...] that allocate a buffer for the 
418 input using malloc. This extension conflicts with ISO C99, which 
419 defines %a as a standalone format specifier that reads a floating- 
420 point number; moreover, POSIX.1-2008 provides the same feature 
421 using the modifier letter 'm' instead (%ms, %mS, %m[...]). 
422 
423 We now follow C99 unless GNU extensions are active and the compiler 
424 is specifically in C89 or C++98 mode (strict or not). For 
425 instance, with GCC, -std=gnu11 will have C99-compliant scanf with 
426 or without -D_GNU_SOURCE, but -std=c89 -D_GNU_SOURCE will have the 
427 old extension. */ 
428#if (defined __USE_GNU \ 
429 && (defined __cplusplus \ 
430 ? (__cplusplus < 201103L && !defined __GXX_EXPERIMENTAL_CXX0X__) \ 
431 : (!defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L))) 
432# define __GLIBC_USE_DEPRECATED_SCANF 1 
433#else 
434# define __GLIBC_USE_DEPRECATED_SCANF 0 
435#endif 
436 
437/* Get definitions of __STDC_* predefined macros, if the compiler has 
438 not preincluded this header automatically. */ 
439#include <stdc-predef.h> 
440 
441/* This macro indicates that the installed library is the GNU C Library. 
442 For historic reasons the value now is 6 and this will stay from now 
443 on. The use of this variable is deprecated. Use __GLIBC__ and 
444 __GLIBC_MINOR__ now (see below) when you want to test for a specific 
445 GNU C library version and use the values in <gnu/lib-names.h> to get 
446 the sonames of the shared libraries. */ 
447#undef __GNU_LIBRARY__ 
448#define __GNU_LIBRARY__ 6 
449 
450/* Major and minor version number of the GNU C library package. Use 
451 these macros to test for features in specific releases. */ 
452#define __GLIBC__ 2 
453#define __GLIBC_MINOR__ 31 
454 
455#define __GLIBC_PREREQ(maj, min) \ 
456 ((__GLIBC__ << 16) + __GLIBC_MINOR__ >= ((maj) << 16) + (min)) 
457 
458/* This is here only because every header file already includes this one. */ 
459#ifndef __ASSEMBLER__ 
460# ifndef _SYS_CDEFS_H 
461# include <sys/cdefs.h> 
462# endif 
463 
464/* If we don't have __REDIRECT, prototypes will be missing if 
465 __USE_FILE_OFFSET64 but not __USE_LARGEFILE[64]. */ 
466# if defined __USE_FILE_OFFSET64 && !defined __REDIRECT 
467# define __USE_LARGEFILE 1 
468# define __USE_LARGEFILE64 1 
469# endif 
470 
471#endif /* !ASSEMBLER */ 
472 
473/* Decide whether we can define 'extern inline' functions in headers. */ 
474#if __GNUC_PREREQ (2, 7) && defined __OPTIMIZE__ \ 
475 && !defined __OPTIMIZE_SIZE__ && !defined __NO_INLINE__ \ 
476 && defined __extern_inline 
477# define __USE_EXTERN_INLINES 1 
478#endif 
479 
480 
481/* This is here only because every header file already includes this one. 
482 Get the definitions of all the appropriate `__stub_FUNCTION' symbols. 
483 <gnu/stubs.h> contains `#define __stub_FUNCTION' when FUNCTION is a stub 
484 that will always return failure (and set errno to ENOSYS). */ 
485#include <gnu/stubs.h> 
486 
487 
488#endif /* features.h */ 
489