Make xnanosleep's integer overflow test more robust

[Jim Meyering]

I noticed a new warning, when compiling with
gcc version 4.3.0 20071004 (experimental) (GCC)

    xnanosleep.c:79: warning: assuming signed overflow does not occur
      when assuming that (X + c) < X is always false

Here's what I've just pushed:

2007-10-07  Jim Meyering  <[EMAIL PROTECTED]>

        Make xnanosleep's integer overflow test more robust.
        * lib/xnanosleep.c (xnanosleep): Declare a temporary to be "volatile",
        so that gcc-4.3.0 doesn't optimize away this test for overflow.

...
diff --git a/lib/xnanosleep.c b/lib/xnanosleep.c
index 6a61ddb..22bd53a 100644
--- a/lib/xnanosleep.c
+++ b/lib/xnanosleep.c
@@ -72,7 +72,9 @@ xnanosleep (double seconds)
   /* Normalize the interval length.  nanosleep requires this.  */
   if (BILLION <= ts_sleep.tv_nsec)
     {
-      time_t t = ts_sleep.tv_sec + 1;
+      /* Declare "volatile" so that gcc-4.3.0 doesn't optimize away
+        the overflow test.  */
+      volatile time_t t = ts_sleep.tv_sec + 1;

       /* Detect integer overflow.  */
       overflow |= (t < ts_sleep.tv_sec);
--
1.5.3.4.206.g58ba4