From a1df0c5d77cb992343b322ee3fd0ec6c019c6216 Mon Sep 17 00:00:00 2001
From: Dirk Ziegelmeier <dirk@ziegelmeier.net>
Date: Tue, 31 Jan 2017 08:35:54 +0100
Subject: [PATCH] Fix build failue in err.h reported by Axel Lin In file
 included from ../../../../lwip/src/include/lwip/sockets.h:49:0,              
    from ../../../../lwip/src/core/init.c:47:
 ../../../../lwip/src/include/lwip/errno.h:46:5: error: "LWIP_PROVIDE_ERRNO"
 is not defined [-Werror=undef]  #if LWIP_PROVIDE_ERRNO     
 ^~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors ../Common.mk:93:
 recipe for target 'init.o' failed make: *** [init.o] Error 1

---
 src/include/lwip/opt.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index e9a81821..0ca2dd01 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -1744,13 +1744,19 @@
 #define LWIP_SOCKET                     1
 #endif
 
-/* LWIP_SOCKET_SET_ERRNO==1: Set errno when socket functions cannot complete
+/** LWIP_SOCKET_SET_ERRNO==1: Set errno when socket functions cannot complete
  * successfully, as required by POSIX. Default is POSIX-compliant.
  */
 #if !defined LWIP_SOCKET_SET_ERRNO || defined __DOXYGEN__
 #define LWIP_SOCKET_SET_ERRNO           1
 #endif
 
+/** LWIP_PROVIDE_ERRNO==1: Let lwIP provide ERRNO values.
+ */
+#if !defined LWIP_PROVIDE_ERRNO || defined __DOXYGEN__
+#define LWIP_PROVIDE_ERRNO              0
+#endif
+
 /**
  * LWIP_COMPAT_SOCKETS==1: Enable BSD-style sockets functions names through defines.
  * LWIP_COMPAT_SOCKETS==2: Same as ==1 but correctly named functions are created.