From 184800782f1cde808e8f7244938a8456333a39c7 Mon Sep 17 00:00:00 2001
From: Dana Robinson <derobins@hdfgroup.org>
Date: Wed, 3 Feb 2016 14:16:36 -0500
Subject: [svn-r29038] Minor fix to configure.ac that fixes a broken
 --enable-clear-file-buffers option.

Fixes HDFFV-9676

Tested on: jam (just a smoke check to ensure that the library builds
                and passes tests when the feature is disabled)
---
 configure                | 12 ++++++------
 configure.ac             |  8 ++++----
 release_docs/RELEASE.txt | 18 ++++++++++++++++++
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/configure b/configure
index 4418586b..bc7ed45 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.ac Id: configure.ac 28970 2016-01-25 21:23:12Z hdftest .
+# From configure.ac Id: configure.ac 29022 2016-01-31 20:03:27Z hdftest .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.69 for HDF5 1.8.17-snap11.
 #
@@ -26469,6 +26469,11 @@ fi
 
 
 case "X-$CLEARFILEBUF" in
+  X-no)
+      CLEARFILEBUF=no
+      { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+    ;;
   *)
       CLEARFILEBUF=yes
       { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
@@ -26477,11 +26482,6 @@ $as_echo "yes" >&6; }
 $as_echo "#define CLEAR_MEMORY 1" >>confdefs.h
 
     ;;
-  X-no)
-      CLEARFILEBUF=no
-      { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-    ;;
 esac
 
 ## ----------------------------------------------------------------------
diff --git a/configure.ac b/configure.ac
index 65e1ff6..2933a7d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1897,6 +1897,10 @@ AC_ARG_ENABLE([clear-file-buffers],
               [CLEARFILEBUF=$enableval])
 
 case "X-$CLEARFILEBUF" in
+  X-no)
+      CLEARFILEBUF=no
+      AC_MSG_RESULT([no])
+    ;;
   *)
       CLEARFILEBUF=yes
       AC_MSG_RESULT([yes])
@@ -1904,10 +1908,6 @@ case "X-$CLEARFILEBUF" in
                 [Define if the memory buffers being written to disk should be
                 cleared before writing.])
     ;;
-  X-no)
-      CLEARFILEBUF=no
-      AC_MSG_RESULT([no])
-    ;;
 esac
 
 ## ----------------------------------------------------------------------
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 933bac5..c8fc391 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -126,6 +126,24 @@ Bug Fixes since HDF5-1.8.16
 
       (DER, 2015/12/08, HDFFV-9627)
 
+    - The --enable-clear-file-buffers configure option was non-functional so
+      the feature was always enabled (its default value).
+
+      Regardless of the configure flag, the setting was always enabled when
+      the autotools were used to configure HDF5. This was due to the "no"
+      option being processed after the "*" option in configure.ac so "*"
+      matched first. CMake was unaffected.
+
+      The option now works correctly.
+
+      NOTE that builders are always advised to leave this option enabled.
+      When disabled, buffers that are written to disk may contain the
+      memory's previous contents, which may include secure information.
+      The performance overhead of the feature (a single memset call per
+      allocation) is minimal.
+
+      (DER, 2016/02/03, HDFFV-9676)
+
     Library
     -------
     - Fixed some format string warnings that prevent compiling with
-- 
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