From 1c3ef1d360c2db1902f5f04415192c123ba4c378 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc=20Dequ=C3=A8nes=20=28Duck=29?= <Duck@DuckCorp.org>
Date: Sat, 19 Oct 2013 11:53:13 +0200
Subject: [PATCH] Really ensure a Yacc alternative is installed at build time

AC_PROG_YACC falls back to YACC = "yacc" if bison or byacc are not
found, but it does not mean it is present.

Closes #294
---
 configure.ac | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/configure.ac b/configure.ac
index c203dc3..63b110d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -12,6 +12,13 @@ AM_PROG_CC_C_O
 AC_PROG_INSTALL
 AM_PROG_LEX
 AC_PROG_YACC
+# AC_PROG_YACC falls back to YACC = "yacc" if bison or byacc are not found, but it does not mean it is present
+AS_IF([test x"$YACC" = "xyacc"], [
+  AC_CHECK_PROG([YACC_EXISTS], [yacc], [yes], [no])
+  AS_IF([test x"$YACC_EXISTS" != xyes], [
+    YACC=${am_missing_run}yacc
+  ])
+])
 
 # Checks for header files.
 AC_FUNC_ALLOCA