From e1e044da017af74d69cf30c2af0006bc628e2c07 Mon Sep 17 00:00:00 2001
From: Robert Edmonds <edmonds@fsi.io>
Date: Fri, 28 Mar 2014 13:23:37 -0400
Subject: [PATCH] configure.ac: search the pkg-config exec_prefix for the
 protobuf compiler

protoc may not be on the default PATH, so augment $PATH with the
executable path registered by pkg-config for the protobuf package.

additionally declare PROTOC as a precious variable, thus allowing it to
be explicitly set by the user at ./configure time.

based on a patch from Andrei Nigmatulin.
---
 configure.ac | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index fea83c5..d8009b9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,7 +47,9 @@ if test "x$enable_protoc" != "xno"; then
                    [AC_MSG_ERROR([required protobuf header file not found])])
   CPPFLAGS="$save_CPPFLAGS"
 
-  AC_PATH_PROG(PROTOC, protoc)
+  AC_ARG_VAR([PROTOC], [protobuf compiler command])
+  AC_PATH_PROG([PROTOC], [protoc], [],
+               [`$PKG_CONFIG --variable=exec_prefix protobuf`/bin:$PATH])
   if test -z "$PROTOC"; then
     AC_MSG_ERROR([Please install the protobuf compiler from https://code.google.com/p/protobuf/.])
   fi