[bug-gnulib] new module gethrxtime for highres realtime clock; gettime change

[Paul Eggert]

I installed the following patch to gnulib, to incorporate recent
coreutils changes for high-resolution time stamps.  This patch adds a
new function gethrxtime that returns a high-resolution realtime clock.
It also modifies gettime's signature: it now returns void (not int)
since it always succeeds.

2005-02-26  Paul Eggert  <address@hidden>

        * modules/gethrxtime: New file.
        * modules/xnanosleep (Files): Add m4/xnanosleep.m4.
        (Depends-on): Add gethrxtime.
        (configure.ac): Add gl_XNANOSLEEP.
        (Makefile.am): Remove lib_SOURCES line.

        * lib/gethrxtime.h, lib/gethrxtime.c, lib/xtime.h: New files.
        * lib/timespec.h (gettime): Return void, since it always
        succeeds now.  All uses changed.
        * lib/gettime.c (gettime) Likewise.
        [HAVE_NANOTIME]: Prefer nanotime.
        Assume gettimeofday succeeds, as POSIX requires.
        Assime time () succeeds, since other code already does.
        * lib/xnanosleep.c: Include xtime.h and gethrxtime.h, not xalloc.h.
        (timespec_subtract): Remove.
        (NANOSLEEP_BUG_WORKAROUND): New constant.
        (xnanosleep): Use gethrxtime rather than gettime; this simplifies
        things considerably.  Use it only on GNU/Linux hosts, since the
        workaround shouldn't be needed elsewhere.

        * m4/gethrxtime.m4, m4/xnanosleep.m4: New files.
        * m4/gettime.m4 (gl_GETTIME): Check for nanotime.

Index: lib/getdate.y
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/getdate.y,v
retrieving revision 1.95
diff -p -u -r1.95 getdate.y
--- lib/getdate.y       24 Dec 2004 05:29:20 -0000      1.95
+++ lib/getdate.y       26 Feb 2005 08:10:31 -0000
@@ -1,6 +1,8 @@
 %{
 /* Parse a string into an internal time stamp.
-   Copyright (C) 1999, 2000, 2002, 2003, 2004 Free Software Foundation, Inc.
+
+   Copyright (C) 1999, 2000, 2002, 2003, 2004, 2005 Free Software
+   Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1125,8 +1127,7 @@ get_date (struct timespec *result, char 
 
   if (! now)
     {
-      if (gettime (&gettime_buffer) != 0)
-       return false;
+      gettime (&gettime_buffer);
       now = &gettime_buffer;
     }
 
Index: lib/gettime.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/gettime.c,v
retrieving revision 1.3
diff -p -u -r1.3 gettime.c
--- lib/gettime.c       13 May 2004 21:59:46 -0000      1.3
+++ lib/gettime.c       26 Feb 2005 08:10:31 -0000
@@ -1,5 +1,5 @@
 /* gettime -- get the system clock
-   Copyright (C) 2002, 2004 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2004, 2005 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -23,37 +23,31 @@
 
 #include "timespec.h"
 
-/* Get the system time.  */
+/* Get the system time into *TS.  */
 
-int
+void
 gettime (struct timespec *ts)
 {
-#if defined CLOCK_REALTIME && HAVE_CLOCK_GETTIME
+#if HAVE_NANOTIME
+  nanotime (ts);
+#else
+
+# if defined CLOCK_REALTIME && HAVE_CLOCK_GETTIME
   if (clock_gettime (CLOCK_REALTIME, ts) == 0)
-    return 0;
-#endif
+    return;
+# endif
 
-#if HAVE_GETTIMEOFDAY
+# if HAVE_GETTIMEOFDAY
   {
     struct timeval tv;
-    if (gettimeofday (&tv, 0) == 0)
-      {
-       ts->tv_sec = tv.tv_sec;
-       ts->tv_nsec = tv.tv_usec * 1000;
-       return 0;
-      }
+    gettimeofday (&tv, NULL);
+    ts->tv_sec = tv.tv_sec;
+    ts->tv_nsec = tv.tv_usec * 1000;
   }
-#endif
+# else
+  ts->tv_sec = time (NULL);
+  ts->tv_nsec = 0;
+# endif
 
-  {
-    time_t t = time (0);
-    if (t != (time_t) -1)
-      {
-       ts->tv_sec = t;
-       ts->tv_nsec = 0;
-       return 0;
-      }
-  }
-
-  return -1;
+#endif
 }
Index: lib/timespec.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/timespec.h,v
retrieving revision 1.3
diff -p -u -r1.3 timespec.h
--- lib/timespec.h      31 Mar 2004 07:38:13 -0000      1.3
+++ lib/timespec.h      26 Feb 2005 08:10:31 -0000
@@ -1,6 +1,6 @@
 /* timespec -- System time interface
 
-   Copyright (C) 2000, 2002, 2004 Free Software Foundation, Inc.
+   Copyright (C) 2000, 2002, 2004, 2005 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -65,7 +65,7 @@ struct timespec
 int nanosleep ();
 # endif
 
-int gettime (struct timespec *);
+void gettime (struct timespec *);
 int settime (struct timespec const *);
 
 #endif
Index: lib/xnanosleep.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/xnanosleep.c,v
retrieving revision 1.1
diff -p -u -r1.1 xnanosleep.c
--- lib/xnanosleep.c    6 Aug 2004 22:51:58 -0000       1.1
+++ lib/xnanosleep.c    26 Feb 2005 08:10:31 -0000
@@ -1,5 +1,5 @@
 /* xnanosleep.c -- a more convenient interface to nanosleep
-   Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
+   Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -32,6 +32,10 @@
 #include <sys/types.h>
 #include <time.h>
 
+#include "timespec.h"
+#include "gethrxtime.h"
+#include "xtime.h"
+
 /* The extra casts work around common compiler bugs.  */
 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
@@ -44,44 +48,18 @@
 # define TIME_T_MAX TYPE_MAXIMUM (time_t)
 #endif
 
-#include "timespec.h"
-#include "xalloc.h"
-
-/* Subtract the `struct timespec' values X and Y by computing X - Y.
-   If the difference is negative or zero, return false.
-   Otherwise, return true and store the difference in DIFF.
-   X and Y must have valid ts_nsec values, in the range 0 to 999999999.
-   If the difference would overflow, store the maximum possible difference.  */
-
-static bool
-timespec_subtract (struct timespec *diff,
-                  struct timespec const *x, struct timespec const *y)
-{
-  time_t sec = x->tv_sec - y->tv_sec;
-  long int nsec = x->tv_nsec - y->tv_nsec;
-
-  if (x->tv_sec < y->tv_sec)
-    return false;
-
-  if (sec < 0)
-    {
-      /* The difference has overflowed.  */
-      sec = TIME_T_MAX;
-      nsec = 999999999;
-    }
-  else if (sec == 0 && nsec <= 0)
-    return false;
-
-  if (nsec < 0)
-    {
-      sec--;
-      nsec += 1000000000;
-    }
-
-  diff->tv_sec = sec;
-  diff->tv_nsec = nsec;
-  return true;
-}
+/* POSIX.1-2001 requires that when a process is suspended, then
+   resumed, nanosleep (A, B) returns -1, sets errno to EINTR, and sets
+   *B to the time remaining at the point of resumption.  However, some
+   versions of the Linux kernel incorrectly return the time remaining
+   at the point of suspension.  Work around this bug on GNU/Linux
+   hosts by computing the remaining time here after nanosleep returns,
+   rather than by relying on nanosleep's computation.  */
+#ifdef __linux__
+enum { NANOSLEEP_BUG_WORKAROUND = true };
+#else
+enum { NANOSLEEP_BUG_WORKAROUND = false };
+#endif
 
 /* Sleep until the time (call it WAKE_UP_TIME) specified as
    SECONDS seconds after the time this function is called.
@@ -93,22 +71,29 @@ timespec_subtract (struct timespec *diff
 int
 xnanosleep (double seconds)
 {
-  bool overflow;
+  enum { BILLION = 1000000000 };
+
+  bool overflow = false;
   double ns;
-  struct timespec ts_start;
   struct timespec ts_sleep;
-  struct timespec ts_stop;
+  xtime_t stop = 0;
 
   assert (0 <= seconds);
 
-  if (gettime (&ts_start) != 0)
-    return -1;
+  if (NANOSLEEP_BUG_WORKAROUND)
+    {
+      xtime_t now = gethrxtime ();
+      double increment = XTIME_PRECISION * seconds;
+      xtime_t incr = increment;
+      stop = now + incr + (incr < increment);
+      overflow = (stop < now);
+    }
 
   /* Separate whole seconds from nanoseconds.
      Be careful to detect any overflow.  */
   ts_sleep.tv_sec = seconds;
-  ns = 1e9 * (seconds - ts_sleep.tv_sec);
-  overflow = ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= 1e9);
+  ns = BILLION * (seconds - ts_sleep.tv_sec);
+  overflow |= ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= BILLION);
   ts_sleep.tv_nsec = ns;
 
   /* Round up to the next whole number, if necessary, so that we
@@ -119,7 +104,7 @@ xnanosleep (double seconds)
   ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
 
   /* Normalize the interval length.  nanosleep requires this.  */
-  if (1000000000 <= ts_sleep.tv_nsec)
+  if (BILLION <= ts_sleep.tv_nsec)
     {
       time_t t = ts_sleep.tv_sec + 1;
 
@@ -127,45 +112,34 @@ xnanosleep (double seconds)
       overflow |= (t < ts_sleep.tv_sec);
 
       ts_sleep.tv_sec = t;
-      ts_sleep.tv_nsec -= 1000000000;
+      ts_sleep.tv_nsec -= BILLION;
     }
 
-  /* Compute the time until which we should sleep.  */
-  ts_stop.tv_sec = ts_start.tv_sec + ts_sleep.tv_sec;
-  ts_stop.tv_nsec = ts_start.tv_nsec + ts_sleep.tv_nsec;
-  if (1000000000 <= ts_stop.tv_nsec)
+  for (;;)
     {
-      ++ts_stop.tv_sec;
-      ts_stop.tv_nsec -= 1000000000;
-    }
-
-  /* Detect integer overflow.  */
-  overflow |= (ts_stop.tv_sec < ts_start.tv_sec
-              || (ts_stop.tv_sec == ts_start.tv_sec
-                  && ts_stop.tv_nsec < ts_start.tv_nsec));
+      if (overflow)
+       {
+         ts_sleep.tv_sec = TIME_T_MAX;
+         ts_sleep.tv_nsec = BILLION - 1;
+       }
 
-  if (overflow)
-    {
-      /* Fix ts_sleep and ts_stop, which may be garbage due to overflow.  */
-      ts_sleep.tv_sec = ts_stop.tv_sec = TIME_T_MAX;
-      ts_sleep.tv_nsec = ts_stop.tv_nsec = 999999999;
-    }
-
-  while (nanosleep (&ts_sleep, NULL) != 0)
-    {
-      if (errno != EINTR || gettime (&ts_start) != 0)
+      if (nanosleep (&ts_sleep, NULL) == 0)
+       break;
+      if (errno != EINTR)
        return -1;
 
-      /* POSIX.1-2001 requires that when a process is suspended, then
-        resumed, nanosleep (A, B) returns -1, sets errno to EINTR,
-        and sets *B to the time remaining at the point of resumption.
-        However, some versions of the Linux kernel incorrectly return
-        the time remaining at the point of suspension.  Work around
-        this bug by computing the remaining time here, rather than by
-        relying on nanosleep's computation.  */
-
-      if (! timespec_subtract (&ts_sleep, &ts_stop, &ts_start))
-       break;
+      if (NANOSLEEP_BUG_WORKAROUND)
+       {
+         xtime_t now = gethrxtime ();
+         if (stop <= now)
+           break;
+         else
+           {
+             xtime_t remaining = stop - now;
+             ts_sleep.tv_sec = xtime_nonnegative_sec (remaining);
+             ts_sleep.tv_nsec = xtime_nonnegative_nsec (remaining);
+           }
+       }
     }
 
   return 0;
Index: m4/gettime.m4
===================================================================
RCS file: /cvsroot/gnulib/gnulib/m4/gettime.m4,v
retrieving revision 1.3
diff -p -u -r1.3 gettime.m4
--- m4/gettime.m4       23 Jan 2005 08:06:57 -0000      1.3
+++ m4/gettime.m4       26 Feb 2005 08:10:32 -0000
@@ -1,13 +1,16 @@
-# gettime.m4 serial 3
-dnl Copyright (C) 2002, 2004 Free Software Foundation, Inc.
+# gettime.m4 serial 5
+dnl Copyright (C) 2002, 2004, 2005 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_GETTIME],
 [
+  AC_LIBSOURCES([gettime.c])
+  AC_LIBOBJ([gettime])
+
   dnl Prerequisites of lib/gettime.c.
   AC_REQUIRE([gl_CLOCK_TIME])
   AC_REQUIRE([gl_TIMESPEC])
-  AC_CHECK_FUNCS_ONCE(gettimeofday)
+  AC_CHECK_FUNCS_ONCE(gettimeofday nanotime)
 ])
Index: modules/xnanosleep
===================================================================
RCS file: /cvsroot/gnulib/gnulib/modules/xnanosleep,v
retrieving revision 1.2
diff -p -u -r1.2 xnanosleep
--- modules/xnanosleep  22 Sep 2004 15:11:04 -0000      1.2
+++ modules/xnanosleep  26 Feb 2005 08:10:32 -0000
@@ -4,15 +4,16 @@ a more convenient interface to nanosleep
 Files:
 lib/xnanosleep.h
 lib/xnanosleep.c
+m4/xnanosleep.m4
 
 Depends-on:
 timespec
-xalloc
+gethrxtime
 
 configure.ac:
+gl_XNANOSLEEP
 
 Makefile.am:
-lib_SOURCES += xnanosleep.h xnanosleep.c
 
 Include:
 "xnanosleep.h"
@@ -22,4 +23,3 @@ GPL
 
 Maintainer:
 Paul Eggert, Jim Meyering
-
--- /dev/null   2003-03-18 13:55:57 -0800
+++ modules/gethrxtime  2005-02-26 00:05:28 -0800
@@ -0,0 +1,26 @@
+Description:
+Get high resolution real time.
+
+Files:
+lib/xtime.h
+lib/gethrxtime.c
+m4/gethrxtime.m4
+m4/clock_time.m4
+m4/longlong.m4
+
+Depends-on:
+extensions
+
+configure.ac:
+gl_GETHRXTIME
+
+Makefile.am:
+
+Include:
+#include "xtime.h"
+
+License:
+GPL
+
+Maintainer:
+Paul Eggert
--- /dev/null   2003-03-18 13:55:57 -0800
+++ lib/xtime.h 2005-02-25 23:50:44 -0800
@@ -0,0 +1,87 @@
+/* xtime -- extended-resolution integer time stamps
+
+   Copyright (C) 2005 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* Written by Paul Eggert.  */
+
+#ifndef XTIME_H_
+#define XTIME_H_ 1
+
+/* xtime_t is a signed type used for time stamps.  It is an integer
+   type that is a count of nanoseconds -- except for obsolescent hosts
+   without sufficiently-wide integers, where it is a count of
+   seconds.  */
+#if HAVE_LONG_LONG
+typedef long long int xtime_t;
+# define XTIME_PRECISION 1000000000LL
+#else
+# include <limits.h>
+typedef long int xtime_t;
+# if LONG_MAX >> 31 >> 31 == 0
+#  define XTIME_PRECISION 1L
+# else
+#  define XTIME_PRECISION 1000000000L
+# endif
+#endif
+
+/* Return an extended time value that contains S seconds and NS
+   nanoseconds, without any overflow checking.  */
+static inline xtime_t
+xtime_make (xtime_t s, int ns)
+{
+  if (XTIME_PRECISION == 1)
+    return s;
+  else
+    return XTIME_PRECISION * s + ns;
+}
+
+/* Return the number of seconds in T, which must be nonnegative.  */
+static inline xtime_t
+xtime_nonnegative_sec (xtime_t t)
+{
+  return t / XTIME_PRECISION;
+}
+
+/* Return the number of seconds in T.  */
+static inline xtime_t
+xtime_sec (xtime_t t)
+{
+  return (XTIME_PRECISION == 1
+         ? t
+         : t < 0
+         ? (t + XTIME_PRECISION - 1) / XTIME_PRECISION - 1
+         : xtime_nonnegative_sec (t));
+}
+
+/* Return the number of nanoseconds in T, which must be nonnegative.  */
+static inline int
+xtime_nonnegative_nsec (xtime_t t)
+{
+  return t % XTIME_PRECISION;
+}
+
+/* Return the number of nanoseconds in T.  */
+static inline int
+xtime_nsec (xtime_t t)
+{
+  int ns = t % XTIME_PRECISION;
+  if (ns < 0)
+    ns += XTIME_PRECISION;
+  return ns;
+}
+
+#endif
--- /dev/null   2003-03-18 13:55:57 -0800
+++ lib/gethrxtime.h    2005-02-25 23:50:27 -0800
@@ -0,0 +1,37 @@
+/* gethrxtime -- get high resolution real time
+
+   Copyright (C) 2005 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* Written by Paul Eggert.  */
+
+#ifndef GETHRXTIME_H_
+#define GETHRXTIME_H_ 1
+
+#include "xtime.h"
+
+/* Get the current time, as a count of the number of nanoseconds since
+   an arbitrary epoch (e.g., the system boot time).  This clock can't
+   be set, is always increasing, and is nearly linear.  */
+
+#if HAVE_ARITHMETIC_HRTIME_T && HAVE_DECL_GETHRTIME
+# include <time.h>
+static inline xtime_t gethrxtime (void) { return gethrtime (); }
+#else
+xtime_t gethrxtime (void);
+#endif
+
+#endif
--- /dev/null   2003-03-18 13:55:57 -0800
+++ lib/gethrxtime.c    2005-02-25 23:50:37 -0800
@@ -0,0 +1,80 @@
+/* gethrxtime -- get high resolution real time
+
+   Copyright (C) 2005 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* Written by Paul Eggert.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "gethrxtime.h"
+
+#include <sys/types.h>
+#if TIME_WITH_SYS_TIME
+# include <sys/time.h>
+# include <time.h>
+#else
+# if HAVE_SYS_TIME_H
+#  include <sys/time.h>
+# else
+#  include <time.h>
+# endif
+#endif
+
+/* Get the time of a high-resolution clock, preferably one that is not
+   subject to resetting or drifting.  */
+
+xtime_t
+gethrxtime (void)
+{
+#if HAVE_NANOUPTIME
+  {
+    struct timespec ts;
+    nanouptime (&ts);
+    return xtime_make (ts.tv_sec, ts.tv_nsec);
+  }
+#else
+
+# if defined CLOCK_MONOTONIC && HAVE_CLOCK_GETTIME
+  {
+    struct timespec ts;
+    if (clock_gettime (CLOCK_MONOTONIC, &ts) == 0)
+      return xtime_make (ts.tv_sec, ts.tv_nsec);
+  }
+# endif
+
+#if HAVE_MICROUPTIME
+  {
+    struct timeval tv;
+    microuptime (&tv);
+    return xtime_make (tv.tv_sec, 1000 * tv.tv_usec);
+  }
+
+  /* No monotonically increasing clocks are available; fall back on a
+     clock that might jump backwards, since it's the best we can do.  */
+# elif HAVE_GETTIMEOFDAY && XTIME_PRECISION != 1
+  {
+    struct timeval tv;
+    gettimeofday (&tv, NULL);
+    return xtime_make (tv.tv_sec, 1000 * tv.tv_usec);
+  }
+# else
+  return xtime_make (time (NULL), 0);
+# endif
+#endif
+}
--- /dev/null   2003-03-18 13:55:57 -0800
+++ m4/gethrxtime.m4    2005-02-25 23:51:53 -0800
@@ -0,0 +1,76 @@
+# gethrxtime.m4 serial 2
+dnl Copyright (C) 2005 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl Written by Paul Eggert.
+
+AC_DEFUN([gl_GETHRXTIME],
+[
+  AC_LIBSOURCES([gethrxtime.c, gethrxtime.h, xtime.h])
+  AC_REQUIRE([gl_ARITHMETIC_HRTIME_T])
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_REQUIRE([gl_XTIME])
+  AC_CHECK_DECLS([gethrtime], [], [], [#include <time.h>])
+  case $ac_cv_have_decl_gethrtime,$gl_cv_arithmetic_hrtime_t in
+  yes,yes) ;;
+  *)
+    AC_LIBOBJ([gethrxtime])
+    gl_PREREQ_GETHRXTIME;;
+  esac
+])
+
+# Test whether hrtime_t is an arithmetic type.
+# It is not arithmetic in older Solaris c89 (which insists on
+# not having a long long int type).
+AC_DEFUN([gl_ARITHMETIC_HRTIME_T],
+[
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_CACHE_CHECK([for arithmetic hrtime_t], gl_cv_arithmetic_hrtime_t,
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM([#include <time.h>],
+         [hrtime_t x = 0; return x/x;])],
+       [gl_cv_arithmetic_hrtime_t=yes],
+       [gl_cv_arithmetic_hrtime_t=no])])
+  if test $gl_cv_arithmetic_hrtime_t = yes; then
+    AC_DEFINE([HAVE_ARITHMETIC_HRTIME_T], 1,
+      [Define if you have an arithmetic hrtime_t type.])
+  fi
+])
+
+# Prerequisites of lib/xtime.h.
+AC_DEFUN([gl_XTIME],
+[
+  AC_REQUIRE([AC_C_INLINE])
+  AC_REQUIRE([gl_AC_TYPE_LONG_LONG])
+  :
+])
+
+# Prerequisites of lib/gethrxtime.c.
+AC_DEFUN([gl_PREREQ_GETHRXTIME],
+[
+  AC_REQUIRE([AC_HEADER_TIME])
+  AC_REQUIRE([gl_CLOCK_TIME])
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_CHECK_FUNCS_ONCE(gettimeofday microuptime nanouptime)
+
+  if test $ac_cv_func_nanouptime != yes; then
+    LIB_GETHRXTIME=
+    AC_CACHE_CHECK([whether CLOCK_MONOTONIC is defined],
+      gl_cv_have_CLOCK_MONOTONIC,
+      [AC_EGREP_CPP([have_CLOCK_MONOTONIC],
+       [
+#        include <time.h>
+#        ifdef CLOCK_MONOTONIC
+         have_CLOCK_MONOTONIC
+#        endif
+       ],
+       gl_cv_have_CLOCK_MONOTONIC=yes,
+       gl_cv_have_CLOCK_MONOTONIC=no)])
+    if test $gl_cv_have_CLOCK_MONOTONIC = yes; then
+      LIB_GETHRXTIME=$LIB_CLOCK_GETTIME
+    fi
+    AC_SUBST([LIB_GETHRXTIME])
+  fi
+])
--- /dev/null   2003-03-18 13:55:57 -0800
+++ m4/xnanosleep.m4    2005-02-25 23:51:40 -0800
@@ -0,0 +1,35 @@
+# xnanosleep.m4 serial 1
+dnl Copyright (C) 2005 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl Written by Paul Eggert.
+
+AC_DEFUN([gl_XNANOSLEEP],
+[
+  AC_LIBSOURCES([xnanosleep.c, xnanosleep.h])
+  AC_LIBOBJ([xnanosleep])
+
+  dnl Prerequisites of lib/xnanosleep.c.
+  AC_REQUIRE([gl_PREREQ_GETHRXTIME])
+
+  LIB_XNANOSLEEP=
+  case $LIB_GETHRXTIME in
+  ?*)
+    AC_CACHE_CHECK([whether __linux__ is defined],
+      gl_cv_have___linux__,
+      [AC_EGREP_CPP([have___linux__],
+       [
+#        ifdef __linux__
+         have___linux__
+#        endif
+       ],
+       gl_cv_have___linux__=yes,
+       gl_cv_have___linux__=no)])
+    if test $gl_cv_have___linux__ = yes; then
+      LIB_XNANOSLEEP=$LIB_GETHRXTIME
+    fi;;
+  esac
+  AC_SUBST([LIB_XNANOSLEEP])
+])