FEATURE_TEST_MACROS(7)	   Linux Programmer's Manual	FEATURE_TEST_MACROS(7)



NAME
       feature_test_macros - feature test macros

DESCRIPTION
       Feature	test  macros  allow  the programmer to control the definitions
       that are exposed by system header files when a program is compiled.

       NOTE: In order to be effective, a feature test macro  must  be  defined
       before including any header files.  This can be done either in the com-
       pilation command (cc -DMACRO=value) or by defining the macro within the
       source code before including any headers.

       Some feature test macros are useful for creating portable applications,
       by preventing nonstandard definitions from being exposed.  Other macros
       can  be	used to expose nonstandard definitions that are not exposed by
       default.

       The precise effects of each of the feature test macros described	 below
       can  be	ascertained by inspecting the <features.h> header file.	 Note:
       applications do not need	 to  directly  include	<features.h>;  indeed,
       doing so is actively discouraged.  See NOTES.

   Specification of feature test macro requirements in manual pages
       When a function requires that a feature test macro is defined, the man-
       ual page SYNOPSIS typically includes a note of the following form (this
       example from the acct(2) manual page):

	       #include <unistd.h>

	       int acct(const char *filename);

	   Feature Test Macro Requirements for glibc (see
	   feature_test_macros(7)):

	       acct(): _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)

       The  ||	means  that in order to obtain the declaration of acct(2) from
       <unistd.h>, either of the following  macro  definitions	must  be  made
       before including any header files:

	      #define _BSD_SOURCE
	      #define _XOPEN_SOURCE	   /* or any value < 500 */

       Alternatively,  equivalent  definitions can be included in the compila-
       tion command:

	      cc -D_BSD_SOURCE
	      cc -D_XOPEN_SOURCE	   # Or any value < 500

       Note that, as described below, some feature test macros are defined  by
       default,	 so  that it may not always be necessary to explicitly specify
       the feature test macro(s) shown in the SYNOPSIS.

       In a few cases, manual pages use a shorthand for expressing the feature
       test macro requirements (this example from readahead(2)):

	      #define _GNU_SOURCE
	      #include <fcntl.h>

	      ssize_t readahead(int fd, off64_t *offset, size_t count);

       This format is employed in cases where only a single feature test macro
       can be used to expose the function declaration, and that macro  is  not
       defined by default.

   Feature test macros understood by glibc
       The  paragraphs	below  explain	how feature test macros are handled in
       Linux glibc 2.x, x > 0.

       First, though a summary of a few details for the impatient:

       *  The macros that you most likely need to use in  modern  source  code
	  are  _POSIX_C_SOURCE	(for  definitions  from	 various  versions  of
	  POSIX.1), _XOPEN_SOURCE (for definitions from	 various  versions  of
	  SUS),	 _GNU_SOURCE  (for  GNU	 and/or	 Linux	specific  stuff),  and
	  _DEFAULT_SOURCE (to get definitions that would normally be  provided
	  by default).

       *  Certain  macros are defined with default values.  Thus, although one
	  or more macros may be indicated as being required in the SYNOPSIS of
	  a man page, it may not be necessary to define them explicitly.  Full
	  details of the defaults are given later in this man page.

       *  Defining _XOPEN_SOURCE with a value of 600 or greater	 produces  the
	  same	effects as defining _POSIX_C_SOURCE with a value of 200112L or
	  greater.  Where one sees

	      _POSIX_C_SOURCE >= 200112L


	  in the feature test macro requirements in  the  SYNOPSIS  of	a  man
	  page, it is implicit that the following has the same effect:

	      _XOPEN_SOURCE >= 600


       *  Defining  _XOPEN_SOURCE  with a value of 700 or greater produces the
	  same effects as defining _POSIX_C_SOURCE with a value of 200809L  or
	  greater.  Where one sees

	      _POSIX_C_SOURCE >= 200809L


	  in  the  feature  test  macro	 requirements in the SYNOPSIS of a man
	  page, it is implicit that the following has the same effect:

	      _XOPEN_SOURCE >= 700


       Linux glibc understands the following feature test macros:

       __STRICT_ANSI__
	       ISO Standard C.	This macro is  implicitly  defined  by	gcc(1)
	       when invoked with, for example, the -std=c99 or -ansi flag.

       _POSIX_C_SOURCE
	       Defining	 this  macro causes header files to expose definitions
	       as follows:

	       o  The value 1 exposes definitions conforming  to  POSIX.1-1990
		  and ISO C (1990).

	       o  The  value 2 or greater additionally exposes definitions for
		  POSIX.2-1992.

	       o  The value 199309L or greater	additionally  exposes  defini-
		  tions for POSIX.1b (real-time extensions).

	       o  The  value  199506L  or greater additionally exposes defini-
		  tions for POSIX.1c (threads).

	       o  (Since glibc 2.3.3) The value 200112L or  greater  addition-
		  ally	exposes	 definitions corresponding to the POSIX.1-2001
		  base specification  (excluding  the  XSI  extension).	  This
		  value	 also  causes  C95  (since  glibc 2.12) and C99 (since
		  glibc 2.10) features to be  exposed  (in  other  words,  the
		  equivalent of defining _ISOC99_SOURCE).

	       o  (Since glibc 2.10) The value 200809L or greater additionally
		  exposes definitions corresponding to the  POSIX.1-2008  base
		  specification (excluding the XSI extension).

       _POSIX_SOURCE
	       Defining	 this  obsolete	 macro with any value is equivalent to
	       defining _POSIX_C_SOURCE with the value 1.

	       Since this macro is obsolete, its usage is generally not	 docu-
	       mented  when  discussing feature test macro requirements in the
	       man pages.

       _XOPEN_SOURCE
	       Defining this macro causes header files to  expose  definitions
	       as follows:

	       o  Defining  with  any  value exposes definitions conforming to
		  POSIX.1, POSIX.2, and XPG4.

	       o  The value 500 or greater  additionally  exposes  definitions
		  for SUSv2 (UNIX 98).

	       o  (Since  glibc	 2.2)  The  value  600 or greater additionally
		  exposes  definitions	for  SUSv3   (UNIX   03;   i.e.,   the
		  POSIX.1-2001	base specification plus the XSI extension) and
		  C99 definitions.

	       o  (Since glibc 2.10) The value	700  or	 greater  additionally
		  exposes  definitions	for SUSv4 (i.e., the POSIX.1-2008 base
		  specification plus the XSI extension).

	       If __STRICT_ANSI__ is not defined, or _XOPEN_SOURCE is  defined
	       with  a	value  greater	than  or  equal	 to  500  and  neither
	       _POSIX_SOURCE nor _POSIX_C_SOURCE is explicitly	defined,  then
	       the following macros are implicitly defined:

	       o  _POSIX_SOURCE is defined with the value 1.

	       o  _POSIX_C_SOURCE  is  defined,	 according  to	the  value  of
		  _XOPEN_SOURCE:

		  _XOPEN_SOURCE < 500
			 _POSIX_C_SOURCE is defined with the value 2.

		  500 <= _XOPEN_SOURCE < 600
			 _POSIX_C_SOURCE is defined with the value 199506L.

		  600 <= _XOPEN_SOURCE < 700
			 _POSIX_C_SOURCE is defined with the value 200112L.

		  700 <= _XOPEN_SOURCE (since glibc 2.10)
			 _POSIX_C_SOURCE is defined with the value 200809L.

	       In addition, defining _XOPEN_SOURCE with	 a  value  of  500  or
	       greater	  produces    the    same    effects	as    defining
	       _XOPEN_SOURCE_EXTENDED.

       _XOPEN_SOURCE_EXTENDED
	       If this macro is defined, and _XOPEN_SOURCE  is	defined,  then
	       expose  definitions  corresponding  to  the XPG4v2 (SUSv1) UNIX
	       extensions (UNIX 95).  Defining _XOPEN_SOURCE with a  value  of
	       500   or	 more  also  produces  the  same  effect  as  defining
	       _XOPEN_SOURCE_EXTENDED.	Use of _XOPEN_SOURCE_EXTENDED  in  new
	       source code should be avoided.

	       Since  defining	_XOPEN_SOURCE  with a value of 500 or more has
	       the same effect as defining _XOPEN_SOURCE_EXTENDED, the	latter
	       (obsolete) feature test macro is generally not described in the
	       SYNOPSIS in man pages.

       _ISOC99_SOURCE (since glibc 2.1.3)
	       Exposes declarations consistent with the ISO C99 standard.

	       Earlier glibc 2.1.x versions  recognized	 an  equivalent	 macro
	       named  _ISOC9X_SOURCE  (because	the  C99 standard had not then
	       been finalized).	 Although the use of this macro	 is  obsolete,
	       glibc continues to recognize it for backward compatibility.

	       Defining	 _ISOC99_SOURCE	 also exposes ISO C (1990) Amendment 1
	       ("C95") definitions.  (The primary change in  C95  was  support
	       for international character sets.)

	       Invoking	 the  C compiler with the option -std=c99 produces the
	       same effects as defining this macro.

       _ISOC11_SOURCE (since glibc 2.16)
	       Exposes declarations consistent	with  the  ISO	C11  standard.
	       Defining	 this  macro  also  enables C99 and C95 features (like
	       _ISOC99_SOURCE).

	       Invoking the C compiler with the option -std=c11	 produces  the
	       same effects as defining this macro.

       _LARGEFILE64_SOURCE
	       Expose definitions for the alternative API specified by the LFS
	       (Large File Summit) as a "transitional extension" to the Single
	       UNIX    Specification.	 (See	<http://opengroup.org/platform
	       /lfs.html>.)  The alternative API consists  of  a  set  of  new
	       objects	(i.e.,	functions  and types) whose names are suffixed
	       with  "64"  (e.g.,  off64_t  versus  off_t,  lseek64()	versus
	       lseek(),	 etc.).	  New  programs	 should not employ this macro;
	       instead _FILE_OFFSET_BITS=64 should be employed.

       _LARGEFILE_SOURCE
	       This macro was historically used to  expose  certain  functions
	       (specifically fseeko(3) and ftello(3)) that address limitations
	       of earlier APIs (fseek(3) and ftell(3)) that use long  int  for
	       file   offsets.	  This	 macro	 is   implicitly   defined  if
	       _XOPEN_SOURCE is defined with a value greater than or equal  to
	       500.   New  programs  should  not  employ  this macro; defining
	       _XOPEN_SOURCE as just described or  defining  _FILE_OFFSET_BITS
	       with  the  value	 64  is the preferred mechanism to achieve the
	       same result.

       _FILE_OFFSET_BITS
	       Defining this macro with the value  64  automatically  converts
	       references  to  32-bit functions and data types related to file
	       I/O and filesystem operations into references to	 their	64-bit
	       counterparts.  This is useful for performing I/O on large files
	       (> 2 Gigabytes) on 32-bit systems.  (Defining this  macro  per-
	       mits  correctly written programs to use large files with only a
	       recompilation being required.)

	       64-bit systems naturally permit file sizes greater than 2 Giga-
	       bytes, and on those systems this macro has no effect.

       _BSD_SOURCE (deprecated since glibc 2.20)
	       Defining	 this  macro  with  any	 value	causes header files to
	       expose BSD-derived definitions.

	       In glibc versions up to and including 2.18, defining this macro
	       also  causes BSD definitions to be preferred in some situations
	       where standards conflict, unless one or more  of	 _SVID_SOURCE,
	       _POSIX_SOURCE,	       _POSIX_C_SOURCE,		_XOPEN_SOURCE,
	       _XOPEN_SOURCE_EXTENDED, or _GNU_SOURCE  is  defined,  in	 which
	       case   BSD  definitions	are  disfavored.   Since  glibc	 2.19,
	       _BSD_SOURCE no longer causes BSD definitions to be preferred in
	       case of conflicts.

	       Since  glibc  2.20,  this  macro is deprecated.	It now has the
	       same effect as defining _DEFAULT_SOURCE, but generates  a  com-
	       pile-time  warning  (unless  _DEFAULT_SOURCE  is also defined).
	       Use _DEFAULT_SOURCE  instead.   To  allow  code	that  requires
	       _BSD_SOURCE  in	glibc  2.19 and earlier and _DEFAULT_SOURCE in
	       glibc 2.20 and later to compile without warnings,  define  both
	       _BSD_SOURCE and _DEFAULT_SOURCE.

       _SVID_SOURCE (deprecated since glibc 2.20)
	       Defining	 this  macro  with  any	 value	causes header files to
	       expose System V-derived definitions.  (SVID == System V	Inter-
	       face Definition; see standards(7).)

	       Since  glibc 2.20, this macro is deprecated in the same fashion
	       as _BSD_SOURCE.

       _DEFAULT_SOURCE (since glibc 2.19)
	       This macro can be defined to ensure that the "default"  defini-
	       tions  are  provided  even when the defaults would otherwise be
	       disabled, as happens  when  individual  macros  are  explicitly
	       defined,	 or  the  compiler is invoked in one of its "standard"
	       modes (e.g., cc -std=c99).   Defining  _DEFAULT_SOURCE  without
	       defining	 other	individual  macros or invoking the compiler in
	       one of its "standard" modes has no effect.

	       The  "default"	definitions   comprise	 those	 required   by
	       POSIX.1-2008 and ISO C99, as well as various definitions origi-
	       nally derived from BSD and System V.  On glibc  2.19  and  ear-
	       lier,  these  defaults were approximately equivalent to explic-
	       itly defining the following:

		   cc -D_BSD_SOURCE -D_SVID_SOURCE -D_POSIX_C_SOURCE=200809

       _ATFILE_SOURCE (since glibc 2.4)
	       Defining this macro with	 any  value  causes  header  files  to
	       expose  declarations  of	 a  range of functions with the suffix
	       "at"; see openat(2).  Since glibc  2.10,	 this  macro  is  also
	       implicitly  defined  if _POSIX_C_SOURCE is defined with a value
	       greater than or equal to 200809L.

       _GNU_SOURCE
	       Defining	 this  macro  (with  any  value)  implicitly   defines
	       _ATFILE_SOURCE,	     _LARGEFILE64_SOURCE,      _ISOC99_SOURCE,
	       _XOPEN_SOURCE_EXTENDED, _POSIX_SOURCE, _POSIX_C_SOURCE with the
	       value  200809L  (200112L in glibc versions before 2.10; 199506L
	       in glibc versions before 2.5; 199309L in glibc versions	before
	       2.1)  and  _XOPEN_SOURCE	 with the value 700 (600 in glibc ver-
	       sions before 2.10; 500 in glibc versions before 2.2).  In addi-
	       tion, various GNU-specific extensions are also exposed.

	       Since  glibc  2.19, defining _GNU_SOURCE also has the effect of
	       implicitly defining _DEFAULT_SOURCE.  In glibc versions	before
	       2.20,  defining	_GNU_SOURCE  also had the effect of implicitly
	       defining _BSD_SOURCE and _SVID_SOURCE.

       _REENTRANT
	       Historically, on various C libraries it was necessary to define
	       this  macro  in	all multithreaded code.	 (Some C libraries may
	       still require this.)  In glibc, this macro also exposed defini-
	       tions of certain reentrant functions.

	       However,	 glibc has been thread-safe by default for many years;
	       since glibc 2.3, the only effect	 of  defining  _REENTRANT  has
	       been  to	 enable	 one  or two of the same declarations that are
	       also enabled  by	 defining  _POSIX_C_SOURCE  with  a  value  of
	       199606L or greater.

	       _REENTRANT  is now obsolete.  In glibc 2.25 and later, defining
	       _REENTRANT is equivalent to defining _POSIX_C_SOURCE  with  the
	       value 199606L.  If a higher POSIX conformance level is selected
	       by  any	other	means	(such	as   _POSIX_C_SOURCE   itself,
	       _XOPEN_SOURCE,  _DEFAULT_SOURCE, or _GNU_SOURCE), then defining
	       _REENTRANT has no effect.

	       This macro  is  automatically  defined  if  one	compiles  with
	       cc -pthread.

       _THREAD_SAFE
	       Synonym	for the (deprecated) _REENTRANT, provided for compati-
	       bility with some other implementations.

       _FORTIFY_SOURCE (since glibc 2.3.4)
	       Defining this macro causes some lightweight checks to  be  per-
	       formed  to  detect  some	 buffer overflow errors when employing
	       various string and memory manipulation functions (for  example,
	       memcpy(3),  memset(3),  stpcpy(3),  strcpy(3), strncpy(3), str-
	       cat(3),	strncat(3),  sprintf(3),   snprintf(3),	  vsprintf(3),
	       vsnprintf(3),  gets(3),	and  wide character variants thereof).
	       For some functions, argument consistency is checked; for	 exam-
	       ple, a check is made that open(2) has been supplied with a mode
	       argument when the specified flags  include  O_CREAT.   Not  all
	       problems are detected, just some common cases.

	       If  _FORTIFY_SOURCE  is	set  to	 1, with compiler optimization
	       level 1 (gcc -O1) and above, checks that shouldn't  change  the
	       behavior	 of  conforming	 programs  are	performed.  With _FOR-
	       TIFY_SOURCE set to 2, some more checking	 is  added,  but  some
	       conforming programs might fail.

	       Some of the checks can be performed at compile time (via macros
	       logic implemented in header  files),  and  result  in  compiler
	       warnings;  other checks take place at run time, and result in a
	       run-time error if the check fails.

	       Use of this macro requires  compiler  support,  available  with
	       gcc(1) since version 4.0.

   Default definitions, implicit definitions, and combining definitions
       If  no  feature	test macros are explicitly defined, then the following
       feature test macros are defined by default: _BSD_SOURCE (in glibc  2.19
       and earlier), _SVID_SOURCE (in glibc 2.19 and earlier), _DEFAULT_SOURCE
       (since glibc 2.19), _POSIX_SOURCE, and _POSIX_C_SOURCE=200809L (200112L
       in  glibc  versions  before 2.10; 199506L in glibc versions before 2.4;
       199309L in glibc versions before 2.1).

       If   any	   of	 __STRICT_ANSI__,    _ISOC99_SOURCE,	_POSIX_SOURCE,
       _POSIX_C_SOURCE, _XOPEN_SOURCE, _XOPEN_SOURCE_EXTENDED, _BSD_SOURCE (in
       glibc 2.19 and earlier), or _SVID_SOURCE (in glibc 2.19 and earlier) is
       explicitly defined, then _BSD_SOURCE, _SVID_SOURCE, and _DEFAULT_SOURCE
       are not defined by default.

       If _POSIX_SOURCE and _POSIX_C_SOURCE are not  explicitly	 defined,  and
       either  __STRICT_ANSI__ is not defined or _XOPEN_SOURCE is defined with
       a value of 500 or more, then

       *  _POSIX_SOURCE is defined with the value 1; and

       *  _POSIX_C_SOURCE is defined with one of the following values:

	  o  2, if _XOPEN_SOURCE is defined with a value less than 500;

	  o  199506L, if _XOPEN_SOURCE is defined with a value greater than or
	     equal to 500 and less than 600; or

	  o  (since  glibc  2.4)  200112L,  if _XOPEN_SOURCE is defined with a
	     value greater than or equal to 600 and less than 700.

	  o  (Since glibc 2.10) 200809L, if _XOPEN_SOURCE is  defined  with  a
	     value greater than or equal to 700.

	  o  Older  versions of glibc do not know about the values 200112L and
	     200809L for _POSIX_C_SOURCE, and the setting of this  macro  will
	     depend on the glibc version.

	  o  If	   _XOPEN_SOURCE   is	undefined,   then   the	  setting   of
	     _POSIX_C_SOURCE depends on the glibc version: 199506L,  in	 glibc
	     versions  before  2.4; 200112L, in glibc 2.4 to 2.9; and 200809L,
	     since glibc 2.10.

       Multiple macros can be defined; the results are additive.

CONFORMING TO
       POSIX.1 specifies _POSIX_C_SOURCE, _POSIX_SOURCE, and _XOPEN_SOURCE.

       _XOPEN_SOURCE_EXTENDED was specified by XPG4v2 (aka SUSv1), but is  not
       present	in SUSv2 and later.  _FILE_OFFSET_BITS is not specified by any
       standard, but is employed on some other implementations.

       _BSD_SOURCE,	_SVID_SOURCE,	  _DEFAULT_SOURCE,     _ATFILE_SOURCE,
       _GNU_SOURCE, _FORTIFY_SOURCE, _REENTRANT, and _THREAD_SAFE are specific
       to Linux (glibc).

NOTES
       <features.h> is a Linux/glibc-specific header file.  Other systems have
       an  analogous  file,  but typically with a different name.  This header
       file is automatically included by other header files as required: it is
       not  necessary to explicitly include it in order to employ feature test
       macros.

       According to which of the above feature test macros are defined,	 <fea-
       tures.h>	 internally  defines  various other macros that are checked by
       other glibc header files.  These macros	have  names  prefixed  by  two
       underscores  (e.g.,  __USE_MISC).   Programs  should never define these
       macros directly: instead, the appropriate feature  test	macro(s)  from
       the list above should be employed.

EXAMPLE
       The  program  below can be used to explore how the various feature test
       macros are set depending on the glibc version  and  what	 feature  test
       macros  are  explicitly	set.  The following shell session, on a system
       with glibc 2.10, shows some examples of what we would see:

	   $ cc ftm.c
	   $ ./a.out
	   _POSIX_SOURCE defined
	   _POSIX_C_SOURCE defined: 200809L
	   _BSD_SOURCE defined
	   _SVID_SOURCE defined
	   _ATFILE_SOURCE defined
	   $ cc -D_XOPEN_SOURCE=500 ftm.c
	   $ ./a.out
	   _POSIX_SOURCE defined
	   _POSIX_C_SOURCE defined: 199506L
	   _XOPEN_SOURCE defined: 500
	   $ cc -D_GNU_SOURCE ftm.c
	   $ ./a.out
	   _POSIX_SOURCE defined
	   _POSIX_C_SOURCE defined: 200809L
	   _ISOC99_SOURCE defined
	   _XOPEN_SOURCE defined: 700
	   _XOPEN_SOURCE_EXTENDED defined
	   _LARGEFILE64_SOURCE defined
	   _BSD_SOURCE defined
	   _SVID_SOURCE defined
	   _ATFILE_SOURCE defined
	   _GNU_SOURCE defined

   Program source

       /* ftm.c */

       #include <stdio.h>
       #include <unistd.h>
       #include <stdlib.h>

       int
       main(int argc, char *argv[])
       {
       #ifdef _POSIX_SOURCE
	   printf("_POSIX_SOURCE defined\n");
       #endif

       #ifdef _POSIX_C_SOURCE
	   printf("_POSIX_C_SOURCE defined: %ldL\n", (long) _POSIX_C_SOURCE);
       #endif

       #ifdef _ISOC99_SOURCE
	   printf("_ISOC99_SOURCE defined\n");
       #endif

       #ifdef _ISOC11_SOURCE
	   printf("_ISOC11_SOURCE defined\n");
       #endif

       #ifdef _XOPEN_SOURCE
	   printf("_XOPEN_SOURCE defined: %d\n", _XOPEN_SOURCE);
       #endif

       #ifdef _XOPEN_SOURCE_EXTENDED
	   printf("_XOPEN_SOURCE_EXTENDED defined\n");
       #endif

       #ifdef _LARGEFILE64_SOURCE
	   printf("_LARGEFILE64_SOURCE defined\n");
       #endif

       #ifdef _FILE_OFFSET_BITS
	   printf("_FILE_OFFSET_BITS defined: %d\n", _FILE_OFFSET_BITS);
       #endif

       #ifdef _BSD_SOURCE
	   printf("_BSD_SOURCE defined\n");
       #endif

       #ifdef _SVID_SOURCE
	   printf("_SVID_SOURCE defined\n");
       #endif

       #ifdef _DEFAULT_SOURCE
	   printf("_DEFAULT_SOURCE defined\n");
       #endif

       #ifdef _ATFILE_SOURCE
	   printf("_ATFILE_SOURCE defined\n");
       #endif

       #ifdef _GNU_SOURCE
	   printf("_GNU_SOURCE defined\n");
       #endif

       #ifdef _REENTRANT
	   printf("_REENTRANT defined\n");
       #endif

       #ifdef _THREAD_SAFE
	   printf("_THREAD_SAFE defined\n");
       #endif

       #ifdef _FORTIFY_SOURCE
	   printf("_FORTIFY_SOURCE defined\n");
       #endif

	   exit(EXIT_SUCCESS);
       }

SEE ALSO
       libc(7), standards(7)

       The section "Feature Test Macros" under info libc.

       /usr/include/features.h

COLOPHON
       This page is part of release 4.10 of the Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       https://www.kernel.org/doc/man-pages/.



Linux				  2016-12-12		FEATURE_TEST_MACROS(7)