Merge from Gnulib

This incorporates:
2017-10-29 timespec: prefer ‘assume’ to ‘assure’
2017-10-27 timespec.h: use "assure" to avoid a spurious warning
2017-10-09 getopt-posix: Fix build failure if ac_cv_header_getopt_h=no
* build-aux/config.guess, build-aux/config.sub:
* lib/timespec.h, lib/unistd.in.h:
Copy from Gnulib.

1 files changed, 15 insertions, 7 deletions

diff --git a/lib/timespec.h b/lib/timespec.h
index 3831301578e..cc34067374f 100644
--- a/lib/timespec.h
+++ b/lib/timespec.h
@@ -33,6 +33,8 @@ _GL_INLINE_HEADER_BEGIN
 extern "C" {
 #endif
 
+#include "verify.h"
+
 /* Resolution of timespec timestamps (in units per second), and log
    base 10 of the resolution.  */
 
@@ -67,23 +69,29 @@ make_timespec (time_t s, long int ns)
    any platform of interest to the GNU project, since all such
    platforms have 32-bit int or wider.
 
-   Replacing "(int) (a.tv_nsec - b.tv_nsec)" with something like
+   Replacing "a.tv_nsec - b.tv_nsec" with something like
    "a.tv_nsec < b.tv_nsec ? -1 : a.tv_nsec > b.tv_nsec" would cause
    this function to work in some cases where the above assumption is
    violated, but not in all cases (e.g., a.tv_sec==1, a.tv_nsec==-2,
    b.tv_sec==0, b.tv_nsec==999999999) and is arguably not worth the
    extra instructions.  Using a subtraction has the advantage of
    detecting some invalid cases on platforms that detect integer
-   overflow.
-
-   The (int) cast avoids a gcc -Wconversion warning.  */
+   overflow.  */
 
 _GL_TIMESPEC_INLINE int _GL_ATTRIBUTE_PURE
 timespec_cmp (struct timespec a, struct timespec b)
 {
-  return (a.tv_sec < b.tv_sec ? -1
-          : a.tv_sec > b.tv_sec ? 1
-          : (int) (a.tv_nsec - b.tv_nsec));
+  if (a.tv_sec < b.tv_sec)
+    return -1;
+  if (a.tv_sec > b.tv_sec)
+    return 1;
+
+  /* Pacify gcc -Wstrict-overflow (bleeding-edge circa 2017-10-02).  See:
+     http://lists.gnu.org/archive/html/bug-gnulib/2017-10/msg00006.html  */
+  assume (-1 <= a.tv_nsec && a.tv_nsec <= 2 * TIMESPEC_RESOLUTION);
+  assume (-1 <= b.tv_nsec && b.tv_nsec <= 2 * TIMESPEC_RESOLUTION);
+
+  return a.tv_nsec - b.tv_nsec;
 }
 
 /* Return -1, 0, 1, depending on the sign of A.  A.tv_nsec must be