BIND 10 master, updated. 070f123aef2d20da364f3f12d57e9be4e070d854 Merge branch 'master' of ssh://git.bind10.isc.org/var/bind10/git/bind10

[BIND 10 source code commits]

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- Log -----------------------------------------------------------------
commit 070f123aef2d20da364f3f12d57e9be4e070d854
Merge: 7e75d22 578392d
Author: Kean Johnston <kean at isc.org>
Date:   Thu Nov 14 10:07:05 2013 +0200

    Merge branch 'master' of ssh://git.bind10.isc.org/var/bind10/git/bind10

commit 7e75d22f278f460b7b61470c62063b345a1f436c
Merge: d6d7f7d ad5750d
Author: Kean Johnston <kean at isc.org>
Date:   Thu Nov 14 10:03:24 2013 +0200

    Merge branch 'trac3119'

-----------------------------------------------------------------------

Summary of changes:
 configure.ac |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

-----------------------------------------------------------------------
diff --git a/configure.ac b/configure.ac
index 4bed0c6..b109261 100644
--- a/configure.ac
+++ b/configure.ac
@@ -755,7 +755,24 @@ CPPFLAGS_SAVED=$CPPFLAGS
 CPPFLAGS="$BOTAN_INCLUDES $CPPFLAGS"
 LIBS_SAVED="$LIBS"
 LIBS="$LIBS $BOTAN_LIBS"
-AC_CHECK_HEADERS([botan/botan.h],,AC_MSG_ERROR([Missing required header files.]))
+
+# ac_header_preproc is an autoconf symbol (undocumented but stable) that
+# is set if the pre-processor phase passes. Thus by adding a custom
+# failure handler we can detect the difference between a header not existing
+# (or not even passing the pre-processor phase) and a header file resulting
+# in compilation failures.
+AC_CHECK_HEADERS([botan/botan.h],,[
+	if test "x$ac_header_preproc" = "xyes"; then
+		AC_MSG_ERROR([
+botan/botan.h was found but is unusable. The most common cause of this problem
+is attempting to use an updated C++ compiler with older C++ libraries, such as
+the version of Botan that comes with your distribution. If you have updated
+your C++ compiler we highly recommend that you use support libraries such as
+Boost and Botan that were compiled with the same compiler version.])
+	else
+		AC_MSG_ERROR([Missing required header files.])
+	fi]
+)
 AC_LINK_IFELSE(
         [AC_LANG_PROGRAM([#include <botan/botan.h>
                           #include <botan/hash.h>