Add commentary for Time::HiRes patches

diff --git a/NEWS b/NEWS
index 3c50ff8a6b4ffdd099c8366bbfc75ddbc3d1f784..818ba1f4a1e1100e833675e863feb5788952603e 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,10 @@ GNU Autoconf NEWS - User visible changes.
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
 ** Backward incompatibilities
+
+*** Autoconf now requires perl 5.8 (2002) or later.
+  Generated 'configure' scripts continue to run without perl.
+
 ** New features
 ** Obsolete features and new warnings
 
@@ -15,6 +19,12 @@ GNU Autoconf NEWS - User visible changes.
 
 ** Notable bug fixes
 
+*** Autoconf caches now use finer-grained timestamps.
+
+  Autoconf now uses floating-point numbers rather than integers to
+  represent cache file timestamps, thus avoiding some problems where
+  automake incorrectly decides not to regenerate stale caches.
+
 * Noteworthy changes in release 2.71 (2021-01-28) [stable]
 
 ** Bug fixes, including:

diff --git a/THANKS b/THANKS
index 6ebe7dbd92590a12f126bb19be38a8802d0ffeb8..ec89a9f7a0d3d8431c57175229e76b6f4e78ffc6 100644 (file)
--- a/THANKS
+++ b/THANKS
@@ -33,6 +33,7 @@ Anaïs Bouque                anais.bouque@fr.thalesgroup.com
 Anders Kaseorg              andersk@MIT.EDU
 Andreas Buening             andreas.buening@nexgo.de
 Andreas Jaeger              aj@suse.de
+Andreas K. Hüttel           dilfridge@gentoo.org
 Andreas Schott              schott@rzg.mpg.de
 Andreas Schwab              schwab@linux-m68k.org
 Andreas Waechter            andreasw@watson.ibm.com

diff --git a/lib/Autom4te/FileUtils.pm b/lib/Autom4te/FileUtils.pm
index 27a5fd911a5362b5521cd8cc8f96a8163a3cd677..60b66cd67bea2ec7e3382a6c0c5c2dbe8936257a 100644 (file)
--- a/lib/Autom4te/FileUtils.pm
+++ b/lib/Autom4te/FileUtils.pm
@@ -119,6 +119,11 @@ sub mtime ($)
     $atime,$mtime,$ctime,$blksize,$blocks) = stat ($file)
     or fatal "cannot stat $file: $!";
 
+  # Unfortunately Time::HiRes converts timestamps to floating-point, and the
+  # rounding error can be several nanoseconds for circa-2021 timestamps.
+  # Perhaps some day Perl will support accurate file timestamps.  For now, do
+  # the best we can without going outside Perl.
+
   return $mtime;
 }