X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fxnanosleep.c;h=b4dbdc1cf025d510a5d55cf56bb2f4252b74cdf3;hb=7ba06c8ff37d8725cb824c64b94be41b9294ffb7;hp=6a61ddb0c3359b805b05a1a35eba05d7bbb44730;hpb=57fdfd3f8ec62b105c53bcdf6f127c35c7fe7391;p=gnulib.git

diff --git a/lib/xnanosleep.c b/lib/xnanosleep.c
index 6a61ddb0c..b4dbdc1cf 100644
--- a/lib/xnanosleep.c
+++ b/lib/xnanosleep.c
@@ -1,7 +1,6 @@
 /* xnanosleep.c -- a more convenient interface to nanosleep
 
-   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007 Free Software
-   Foundation, Inc.
+   Copyright (C) 2002-2007, 2009-2010 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
@@ -49,57 +48,70 @@ xnanosleep (double seconds)
 {
   enum { BILLION = 1000000000 };
 
-  bool overflow = false;
-  double ns;
+  /* For overflow checking, use naive comparison if possible, widening
+     to long double if double is not wide enough.  Otherwise, use <=,
+     not <, to avoid problems when TIME_T_MAX is less than SECONDS but
+     compares equal to SECONDS after loss of precision when coercing
+     from time_t to long double.  This mishandles near-maximal values
+     in some rare (perhaps theoretical) cases but that is better than
+     undefined behavior.  */
+  bool overflow = ((time_t) ((double) TIME_T_MAX / 2) == TIME_T_MAX / 2
+                   ? TIME_T_MAX < seconds
+                   : (time_t) ((long double) TIME_T_MAX / 2) == TIME_T_MAX / 2
+                   ? TIME_T_MAX < (long double) seconds
+                   : TIME_T_MAX <= (long double) seconds);
+
   struct timespec ts_sleep;
 
   assert (0 <= seconds);
 
-  /* Separate whole seconds from nanoseconds.
-     Be careful to detect any overflow.  */
-  ts_sleep.tv_sec = seconds;
-  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
-     always sleep for at least the requested amount of time.  Assuming
-     the default rounding mode, we don't have to worry about the
-     rounding error when computing 'ns' above, since the error won't
-     cause 'ns' to drop below an integer boundary.  */
-  ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
-
-  /* Normalize the interval length.  nanosleep requires this.  */
-  if (BILLION <= ts_sleep.tv_nsec)
+  /* Separate whole seconds from nanoseconds.  */
+  if (! overflow)
     {
-      time_t t = ts_sleep.tv_sec + 1;
-
-      /* Detect integer overflow.  */
-      overflow |= (t < ts_sleep.tv_sec);
-
-      ts_sleep.tv_sec = t;
-      ts_sleep.tv_nsec -= BILLION;
+      time_t floor_seconds = seconds;
+      double ns = BILLION * (seconds - floor_seconds);
+      ts_sleep.tv_sec = floor_seconds;
+
+      /* Round up to the next whole number, if necessary, so that we
+         always sleep for at least the requested amount of time.  Assuming
+         the default rounding mode, we don't have to worry about the
+         rounding error when computing 'ns' above, since the error won't
+         cause 'ns' to drop below an integer boundary.  */
+      ts_sleep.tv_nsec = ns;
+      ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns);
+
+      /* Normalize the interval length.  nanosleep requires this.  */
+      if (BILLION <= ts_sleep.tv_nsec)
+        {
+          if (ts_sleep.tv_sec == TIME_T_MAX)
+            overflow = true;
+          else
+            {
+              ts_sleep.tv_sec++;
+              ts_sleep.tv_nsec -= BILLION;
+            }
+        }
     }
 
   for (;;)
     {
       if (overflow)
-	{
-	  ts_sleep.tv_sec = TIME_T_MAX;
-	  ts_sleep.tv_nsec = BILLION - 1;
-	}
+        {
+          ts_sleep.tv_sec = TIME_T_MAX;
+          ts_sleep.tv_nsec = BILLION - 1;
+        }
 
       /* Linux-2.6.8.1's nanosleep returns -1, but doesn't set errno
-	 when resumed after being suspended.  Earlier versions would
-	 set errno to EINTR.  nanosleep from linux-2.6.10, as well as
-	 implementations by (all?) other vendors, doesn't return -1
-	 in that case;  either it continues sleeping (if time remains)
-	 or it returns zero (if the wake-up time has passed).  */
+         when resumed after being suspended.  Earlier versions would
+         set errno to EINTR.  nanosleep from linux-2.6.10, as well as
+         implementations by (all?) other vendors, doesn't return -1
+         in that case;  either it continues sleeping (if time remains)
+         or it returns zero (if the wake-up time has passed).  */
       errno = 0;
       if (nanosleep (&ts_sleep, NULL) == 0)
-	break;
+        break;
       if (errno != EINTR && errno != 0)
-	return -1;
+        return -1;
     }
 
   return 0;