StdLib/Include/sys/featuretest.h

   1 /*      $NetBSD: featuretest.h,v 1.8 2005/12/11 12:25:20 christos Exp $ */
   2
   3 /*
   4  * Written by Klaus Klein <kleink@NetBSD.org>, February 2, 1998.
   5  * Public domain.
   6  *
   7  * NOTE: Do not protect this header against multiple inclusion.  Doing
   8  * so can have subtle side-effects due to header file inclusion order
   9  * and testing of e.g. _POSIX_SOURCE vs. _POSIX_C_SOURCE.  Instead,
  10  * protect each CPP macro that we want to supply.
  11  */
  12
  13 /*
  14  * Feature-test macros are defined by several standards, and allow an
  15  * application to specify what symbols they want the system headers to
  16  * expose, and hence what standard they want them to conform to.
  17  * There are two classes of feature-test macros.  The first class
  18  * specify complete standards, and if one of these is defined, header
  19  * files will try to conform to the relevant standard.  They are:
  20  *
  21  * ANSI macros:
  22  * _ANSI_SOURCE                 ANSI C89
  23  *
  24  * POSIX macros:
  25  * _POSIX_SOURCE == 1           IEEE Std 1003.1 (version?)
  26  * _POSIX_C_SOURCE == 1         IEEE Std 1003.1-1990
  27  * _POSIX_C_SOURCE == 2         IEEE Std 1003.2-1992
  28  * _POSIX_C_SOURCE == 199309L   IEEE Std 1003.1b-1993
  29  * _POSIX_C_SOURCE == 199506L   ISO/IEC 9945-1:1996
  30  * _POSIX_C_SOURCE == 200112L   IEEE Std 1003.1-2001
  31  *
  32  * X/Open macros:
  33  * _XOPEN_SOURCE                System Interfaces and Headers, Issue 4, Ver 2
  34  * _XOPEN_SOURCE_EXTENDED == 1  XSH4.2 UNIX extensions
  35  * _XOPEN_SOURCE == 500         System Interfaces and Headers, Issue 5
  36  * _XOPEN_SOURCE == 520         Networking Services (XNS), Issue 5.2
  37  * _XOPEN_SOURCE == 600         IEEE Std 1003.1-2001, XSI option
  38  *
  39  * NetBSD macros:
  40  * _NETBSD_SOURCE == 1          Make all NetBSD features available.
  41  *
  42  * If more than one of these "major" feature-test macros is defined,
  43  * then the set of facilities provided (and namespace used) is the
  44  * union of that specified by the relevant standards, and in case of
  45  * conflict, the earlier standard in the above list has precedence (so
  46  * if both _POSIX_C_SOURCE and _NETBSD_SOURCE are defined, the version
  47  * of rename() that's used is the POSIX one).  If none of the "major"
  48  * feature-test macros is defined, _NETBSD_SOURCE is assumed.
  49  *
  50  * There are also "minor" feature-test macros, which enable extra
  51  * functionality in addition to some base standard.  They should be
  52  * defined along with one of the "major" macros.  The "minor" macros
  53  * are:
  54  *
  55  * _REENTRANT
  56  * _ISOC99_SOURCE
  57  * _LARGEFILE_SOURCE            Large File Support
  58  *              <http://ftp.sas.com/standards/large.file/x_open.20Mar96.html>
  59  */
  60
  61 #if defined(_POSIX_SOURCE) && !defined(_POSIX_C_SOURCE)
  62 #define _POSIX_C_SOURCE 1L
  63 #endif
  64
  65 #if !defined(_ANSI_SOURCE) && !defined(_POSIX_C_SOURCE) && \
  66     !defined(_XOPEN_SOURCE) && !defined(_NETBSD_SOURCE)
  67 #define _NETBSD_SOURCE 1
  68 #endif
  69
  70 #if ((_POSIX_C_SOURCE - 0) >= 199506L || (_XOPEN_SOURCE - 0) >= 500) && \
  71     !defined(_REENTRANT)
  72 #define _REENTRANT
  73 #endif