From 86b9e8e39a0b42407c95921ca8262b0a75cad5f2 Mon Sep 17 00:00:00 2001
From: Jan Maria Matejka <mq@ucw.cz>
Date: Tue, 17 Jul 2018 15:30:59 +0200
Subject: M4: generate synchronization lines

This also includes Bison version check. Versions before 3.0 don't
support them in a reliable way and we don't promise to work with
versions older than 2.4.
---
 configure.ac | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'configure.ac')

diff --git a/configure.ac b/configure.ac
index 44184273..9a2e55e2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -157,6 +157,15 @@ test -z "$FLEX"	 && AC_MSG_ERROR([Flex is missing.])
 test -z "$BISON" && AC_MSG_ERROR([Bison is missing.])
 test -z "$M4"	 && AC_MSG_ERROR([M4 is missing.])
 
+AC_MSG_CHECKING([bison version])
+BIRD_CHECK_BISON_VERSION(BISON_VERSION)
+AC_MSG_RESULT([$BISON_VERSION])
+if test "$bird_bison_synclines" = yes; then
+  M4FLAGS="$M4FLAGS -s"
+fi
+
+AC_SUBST([M4FLAGS])
+
 BIRD_CHECK_PROG_FLAVOR_GNU([$M4],
   [],
   [AC_MSG_ERROR([Provided M4 is not GNU M4.])]
-- 
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