From 3b5803ec9aba483278fd5faad74a49f10bb052d8 Mon Sep 17 00:00:00 2001
From: Dirk Ziegelmeier <dirk@ziegelmeier.net>
Date: Tue, 23 Feb 2016 15:49:58 +0100
Subject: [PATCH] sys.h: Avoid un #defined LWIP_COMPAT_MUTEX macro (usually
 #defined in arch/sys_arch.h)

---
 src/include/lwip/sys.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/include/lwip/sys.h b/src/include/lwip/sys.h
index ca37de81..86d0f3b3 100644
--- a/src/include/lwip/sys.h
+++ b/src/include/lwip/sys.h
@@ -99,6 +99,10 @@ typedef void (*lwip_thread_fn)(void *arg);
 
 /** Define LWIP_COMPAT_MUTEX if the port has no mutexes and binary semaphores
     should be used instead */
+#ifndef LWIP_COMPAT_MUTEX
+#define LWIP_COMPAT_MUTEX 0
+#endif
+
 #if LWIP_COMPAT_MUTEX
 /* for old ports that don't have mutexes: define them to binary semaphores */
 #define sys_mutex_t                   sys_sem_t