[lwip-users] using errno properly

[Rishi Khan]

Does anyone have an example of how to use errno correctly in lwip?  
When I do this, it gives me undefined reference to __errno:
#include "lwip/opt.h"
#include "lwip/init.h"
#include "lwip/sys.h"
#include "lwip/tcp.h"
#include "lwip/inet_chksum.h"
#include "lwip/tcpip.h"
#include "lwip/stats.h"
#include "lwip/sockets.h"
#include "lwip/ip_addr.h"

...

      len =  lwip_recv(connect_sock, buf, 10000, 0);
      if (len <= 0)
      {
        if (errno == ESHUTDOWN) break;
        else if ((errno == ENOMEM) || (errno == ENOBUFS)) continue;
        else kprintf("RECV error: %d. See lwip/api/sockets.c. 
\n",errno);
      }
----

This gives me:
my_file.o:  Undefined reference to:  __errno

Any ideas what is wrong??

My sys_arch.c has "#include <errno.h>" just like the unixsim port

Thanks
Rishi