text: //  (C) Copyright John Maddock 2001 - 2003. 
  //  Use, modification and distribution are subject to the 
  //  Boost Software License, Version 1.0. (See accompanying file 
  //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  
  
  //  See http://www.boost.org for most recent version.
  
  // All POSIX feature tests go in this file,
  // Note that we test _POSIX_C_SOURCE and _XOPEN_SOURCE as well
  // _POSIX_VERSION and _XOPEN_VERSION: on some systems POSIX API's
  // may be present but none-functional unless _POSIX_C_SOURCE and
  // _XOPEN_SOURCE have conn defined to the right value (it's up
  // to the user to do this *before* including any header, although
  // in most cases the compiler will do this for you).
  
  #  if defined(BOOST_HAS_UNISTD_H)
  #     include <unistd.h>
  
        // XOpen has <nl_types.h>, but is this the correct version check?
  #     if defined(_XOPEN_VERSION) && (_XOPEN_VERSION >= 3)
  #        define BOOST_HAS_NL_TYPES_H
  #     endif
  
        // POSIX version 6 requires <stdint.h>
  #     if defined(_POSIX_VERSION) && (_POSIX_VERSION >= 200100)
  #        define BOOST_HAS_STDINT_H
  #     endif
  
        // POSIX version 2 requires <dirent.h>
  #     if defined(_POSIX_VERSION) && (_POSIX_VERSION >= 199009L)
  #        define BOOST_HAS_DIRENT_H
  #     endif
  
        // POSIX version 3 requires <signal.h> to have sigaction:
  #     if defined(_POSIX_VERSION) && (_POSIX_VERSION >= 199506L)
  #        define BOOST_HAS_SIGACTION
  #     endif
        // POSIX defines _POSIX_THREADS > 0 for pthread support,
        // however some platforms define _POSIX_THREADS without
        // a value, hence the (_POSIX_THREADS+0 >= 0) check.
        // Strictly speaking this may catch platforms with a
        // non-functioning stub <pthreads.h>, but such occurrences should
        // occur very rarely if at all.
  #     if defined(_POSIX_THREADS) && (_POSIX_THREADS+0 >= 0) && !defined(BOOST_HAS_WINTHREADS) && !defined(BOOST_HAS_MPTASKS)
  #        define BOOST_HAS_PTHREADS
  #     endif
  
        // BOOST_HAS_NANOSLEEP:
        // This is predicated on _POSIX_TIMERS or _XOPEN_REALTIME:
  #     if (defined(_POSIX_TIMERS) && (_POSIX_TIMERS+0 >= 0)) \
               || (defined(_XOPEN_REALTIME) && (_XOPEN_REALTIME+0 >= 0))
  #        define BOOST_HAS_NANOSLEEP
  #     endif
  
        // BOOST_HAS_CLOCK_GETTIME:
        // This is predicated on _POSIX_TIMERS (also on _XOPEN_REALTIME
        // but at least one platform - linux - defines that flag without
        // defining clock_gettime):
  #     if (defined(_POSIX_TIMERS) && (_POSIX_TIMERS+0 >= 0))
  #        define BOOST_HAS_CLOCK_GETTIME
  #     endif
  
        // BOOST_HAS_SCHED_YIELD:
        // This is predicated on _POSIX_PRIORITY_SCHEDULING or
        // on _POSIX_THREAD_PRIORITY_SCHEDULING or on _XOPEN_REALTIME.
  #     if defined(_POSIX_PRIORITY_SCHEDULING) && (_POSIX_PRIORITY_SCHEDULING+0 > 0)\
              || (defined(_POSIX_THREAD_PRIORITY_SCHEDULING) && (_POSIX_THREAD_PRIORITY_SCHEDULING+0 > 0))\
              || (defined(_XOPEN_REALTIME) && (_XOPEN_REALTIME+0 >= 0))
  #        define BOOST_HAS_SCHED_YIELD
  #     endif
  
        // BOOST_HAS_GETTIMEOFDAY:
        // BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE:
        // These are predicated on _XOPEN_VERSION, and appears to be first released
        // in issue 4, version 2 (_XOPEN_VERSION > 500).
        // Likewise for the functions log1p and expm1.
  #     if defined(_XOPEN_VERSION) && (_XOPEN_VERSION+0 >= 500)
  #        define BOOST_HAS_GETTIMEOFDAY
  #        if defined(_XOPEN_SOURCE) && (_XOPEN_SOURCE+0 >= 500)
  #           define BOOST_HAS_PTHREAD_MUTEXATTR_SETTYPE
  #        endif
  #        ifndef BOOST_HAS_LOG1P
  #           define BOOST_HAS_LOG1P
  #        endif
  #        ifndef BOOST_HAS_EXPM1
  #           define BOOST_HAS_EXPM1
  #        endif
  #     endif
  
  #  endif
  
  
  
  
  