From cdaee9de09c7f0a0d41ca82ad198faad77622aa1 Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@tuebingen.mpg.de>
Date: Thu, 11 Jan 2018 09:05:13 +0100
Subject: [PATCH] build: Error out early if flex or bison are not found.

The configure script tests for these executables, but we happily
proceed even if they are not found. For the m4 executable we got
the check right, however. Introduce a general helper that calls
AC_PATH_PROG() to locate an executable and aborts if it is not found.
---
 configure.ac | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/configure.ac b/configure.ac
index 1a375e9f..499571a7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -46,20 +46,21 @@ AC_DEFUN([LIB_SUBST_FLAGS], [
 	AC_SUBST($1_cppflags)
 	AC_SUBST($1_ldflags)
 ])
+AC_DEFUN([REQUIRE_EXECUTABLE], [
+        AC_PATH_PROG(m4_toupper([$1]), [$1])
+        test -z "$m4_toupper([$1])" && AC_MSG_ERROR(
+		[$1 is required to build this package])
+])
 
 AC_USE_SYSTEM_EXTENSIONS
 AC_C_BIGENDIAN()
-
-AC_PATH_PROG([BISON], [bison])
-AC_PATH_PROG([FLEX], [flex])
-
-AC_PATH_PROG([M4], [m4])
-test -z "$M4" && AC_MSG_ERROR(
-	[The m4 macro processor is required to build this package])
-
 AC_PROG_CC
 AC_PROG_CPP
 
+REQUIRE_EXECUTABLE([bison])
+REQUIRE_EXECUTABLE([flex])
+REQUIRE_EXECUTABLE([m4])
+
 executables="recv filter audioc write afh play"
 ########################################################################### osl
 STASH_FLAGS
-- 
2.39.2