From c6751cfb92e5c5a4cdfc778398f74468123ccdf1 Mon Sep 17 00:00:00 2001
From: Keegan McAllister <mcallister.keegan@gmail.com>
Date: Tue, 10 Apr 2012 22:00:48 -0400
Subject: [PATCH] configure.ac: Fix protoc check

AC_MSG_ERROR inside the variable assignment doesn't work properly.  We get
output like

    checking for protoc... ./configure: line 4524: is: command not found
    no

and then the build continues (and fails) with PROTOC="".

Closes #132 github pull request.
---
 configure.ac | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index f96acec..24f5a13 100644
--- a/configure.ac
+++ b/configure.ac
@@ -13,7 +13,9 @@ AC_CONFIG_HEADERS([config.h])
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_RANLIB
-AC_PATH_PROG([PROTOC], [protoc], [AC_MSG_ERROR([protoc is not found])])
+AC_PATH_PROG([PROTOC], [protoc], [])
+AS_IF([test x"$PROTOC" = x],
+  [AC_MSG_ERROR([cannot find protoc, the Protocol Buffers compiler])])
 
 WARNING_CXXFLAGS=""
 PICKY_CXXFLAGS=""