From bcc3c6b61b3d1ff411578182c0d5c2604223ab61 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Tue, 21 Jun 2016 15:38:00 +0200
Subject: [PATCH] Detect too-old libunistring at configure-time.

* configure.ac: Detect too-old libunistring at configure-time.  Fixes
  #17399.
---
 configure.ac | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/configure.ac b/configure.ac
index b1bd7f1a8..c9c1795c2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -891,6 +891,13 @@ if test "x$LTLIBUNISTRING" = "x"; then
   AC_MSG_ERROR([GNU libunistring is required, please install it.])
 fi
 
+dnl Sloppy check to make sure people aren't trying to use too-old libunistring.
+case "$LIBUNISTRING_VERSION" in
+  0.9.0 | 0.9.1 | 0.9.2 )
+  AC_MSG_ERROR([libunistring too old.  Please install a recent libunistring (>= 0.9.3).])
+  ;;
+esac
+
 GUILE_LIBUNISTRING_WITH_ICONV_SUPPORT
 if test "x$ac_cv_libunistring_with_iconv_support" != "xyes"; then
   AC_MSG_ERROR([No iconv support.  Please recompile libunistring with iconv enabled.])