From 0389931aad668447b8e7c363d028cb363f1f6a03 Mon Sep 17 00:00:00 2001
From: Jan Maria Matejka <mq@ucw.cz>
Date: Tue, 14 Aug 2018 14:36:44 +0200
Subject: [PATCH] Bison: A bit more verbose error messages in config.

---
 aclocal.m4     | 2 ++
 conf/Makefile  | 2 +-
 configure.ac   | 5 +++++
 tools/Rules.in | 1 +
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/aclocal.m4 b/aclocal.m4
index 2cf4da1f..05e46d38 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -151,9 +151,11 @@ AC_DEFUN([BIRD_CHECK_BISON_VERSION],
       ;;
     2.*)
       bird_bison_synclines=no
+      bird_bison_enhanced_error=no
       ;;
     3.* | 4.* | 5.* | 6.* | 7.* | 8.* | 9.*)
       bird_bison_synclines=yes
+      bird_bison_enhanced_error=yes
       ;;
     *)
       AC_MSG_ERROR([Couldn't parse Bison version $$1. Call the developers for help.])
diff --git a/conf/Makefile b/conf/Makefile
index 0eee95ec..f9e9b929 100644
--- a/conf/Makefile
+++ b/conf/Makefile
@@ -12,7 +12,7 @@ BISON_DEBUG=-t
 endif
 
 cf-parse.tab.c: cf-parse.y
-	$(BISON) -bcf-parse -dv -pcf_ $(BISON_DEBUG) cf-parse.y
+	$(BISON) $(BISONFLAGS) -bcf-parse -dv -pcf_ $(BISON_DEBUG) cf-parse.y
 
 cf-parse.y: $(conf-fragments) $(conf-src)/gen_parser.m4
 	$(M4) $(M4FLAGS) -P $(conf-src)/gen_parser.m4 $(conf-fragments) >cf-parse.y
diff --git a/configure.ac b/configure.ac
index 750d7449..645fdf0d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -185,7 +185,12 @@ if test "$bird_bison_synclines" = yes; then
   M4FLAGS="$M4FLAGS -s"
 fi
 
+if test "$bird_bison_enhanced_error" = yes; then
+  BISONFLAGS="$BISONFLAGS -Dparse.lac=full -Dparse.error=verbose"
+fi
+
 AC_SUBST([M4FLAGS])
+AC_SUBST([BISONFLAGS])
 
 BIRD_CHECK_PROG_FLAVOR_GNU([$M4],
   [],
diff --git a/tools/Rules.in b/tools/Rules.in
index 92c61615..3f4aa4f7 100644
--- a/tools/Rules.in
+++ b/tools/Rules.in
@@ -23,6 +23,7 @@ CPPFLAGS=-I$(root-rel) -I$(srcdir) @CPPFLAGS@
 CFLAGS=$(CPPFLAGS) @CFLAGS@
 LDFLAGS=@LDFLAGS@
 M4FLAGS=@M4FLAGS@
+BISONFLAGS=@BISONFLAGS@
 LIBS=@LIBS@
 CLIENT_LIBS=@CLIENT_LIBS@
 CC=@CC@