With most optional features (--with-libxml2 --with-libjson etc usw)
the build will fail if you ./configure --with-FEATURE and FEATURE is not
available. This does not work for readline - the failure is ignored.

The following patch fixes the bug and incidentally removes a little bit of
duplicated code.

---
 configure.in | 37 +++++++++++--------------------------
 1 file changed, 11 insertions(+), 26 deletions(-)

diff --git a/configure.in b/configure.in
index 18a08a5..0731005 100644
--- a/configure.in
+++ b/configure.in
@@ -3436,12 +3436,16 @@ AC_SUBST(ISC_PLATFORM_NEEDSTRCASESTR)
 AC_SUBST(READLINE_LIB)
 AC_ARG_WITH(readline,
 	[  --with-readline[=LIBSPEC]    specify readline library [default auto]],
-	readline="$withval", readline="auto")
-case "$readline" in
+	use_readline="$withval", use_readline="auto")
+case "$use_readline" in
 no)	;;
-yes|auto)
+*)
 	saved_LIBS="$LIBS"
-	for readline in -ledit -lreadline
+	case "$use_readline" in
+	yes|auto) readline_libs="-ledit -lreadline" ;;
+	*)        readline_libs="$use_readline" ;;
+	esac
+	for readline in $readline_libs
 	do
 		LIBS="$readline"
 		AC_MSG_NOTICE(checking for readline with $readline)
@@ -3468,29 +3472,10 @@ yes|auto)
 			break
 		fi
 	done
-	LIBS="$saved_LIBS"
-	;;
-*)
-	saved_LIBS="$LIBS"
-	LIBS="$readline"
-	AC_MSG_NOTICE(checking for readline with $readline)
-	AC_CHECK_FUNCS(readline)
-	if test "$ac_cv_func_readline" = "yes"
+	if test "$use_readline" != "auto" &&
+	   test "X$READLINE_LIB" = "X"
 	then
-		READLINE_LIB="$readline"
-	else
-		for lib in -lterminfo -ltermcap -lncurses -lcurses
-		do
-			AC_MSG_NOTICE(checking for readline with $readline $lib)
-			unset ac_cv_func_readline
-			LIBS="$readline $lib"
-			AC_CHECK_FUNCS(readline)
-			if test "$ac_cv_func_readline" = "yes"
-			then
-				READLINE_LIB="$readline $lib"
-				break
-			fi
-		done
+		AC_MSG_ERROR([The readline library was not found.])
 	fi
 	LIBS="$saved_LIBS"
 	;;
-- 
2.1.4