From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 1 Sep 2021 00:34:46 +0000 (-0700)
Subject: Add commentary for Time::HiRes patches
X-Git-Tag: v2.72c~79
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e8c2d79ec42c70b6e4fa282bc0c024bf42f0585f;p=thirdparty%2Fautoconf.git

Add commentary for Time::HiRes patches
---

diff --git a/NEWS b/NEWS
index 3c50ff8a..818ba1f4 100644
--- 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 6ebe7dbd..ec89a9f7 100644
--- 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 27a5fd91..60b66cd6 100644
--- 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;
 }