diff --git a/CHANGELOG b/CHANGELOG
index d3779bb5..b4563abc 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -245,9 +245,9 @@ HISTORY
 
   2007-05-11 Frédéric Bernon
   * sockets.c, api_lib.c, api_msg.h, api_msg.c, netifapi.h, netifapi.c, tcpip.c:
-   Include a function pointer instead of a table index in the message to reduce
-   footprint. Disable some part of lwip_send and lwip_sendto if some options are
-   not set (LWIP_TCP, LWIP_UDP, LWIP_RAW).
+    Include a function pointer instead of a table index in the message to reduce
+    footprint. Disable some part of lwip_send and lwip_sendto if some options are
+    not set (LWIP_TCP, LWIP_UDP, LWIP_RAW).
 
   2007-05-10 Simon Goldschmidt
   * *.h (except netif/ppp/*.h): Included patch #5448: include '#ifdef __cplusplus
@@ -311,7 +311,7 @@ HISTORY
     device, and we can use ARP with it to do a "gratuitous ARP" (RFC 3220 "IP Mobility
     Support for IPv4" section 4.6) when interface is "up" with netif_set_up().
 
-  2007-03-26 Frédéric Bernon, Jonathan Larmour  
+  2007-03-26 Frédéric Bernon, Jonathan Larmour
   * opt.h, tcpip.c: New configuration option LWIP_ARP allow to disable ARP init at build
     time if you only use PPP or SLIP. The default is enable. Note we don't have to call 
     etharp_init in your port's initilization sequence if you use tcpip.c, because this call
@@ -340,7 +340,7 @@ HISTORY
     be configured at run time with LWIP_TCP_KEEPALIVE, but don't change this
     unless you know what you're doing (default are RFC1122 compliant). Note
     that TCP_KEEPIDLE and TCP_KEEPINTVL have to be set in seconds.
-  
+
   2007-03-08 Frédéric Bernon
   * tcp.h: Keepalive values can be configured at compile time, but don't change
     this unless you know what you're doing (default are RFC1122 compliant).
@@ -349,7 +349,7 @@ HISTORY
   * sockets.c, api.h, api_lib.c, tcpip.c, sys.h, sys.c, err.c, opt.h:
     Implement LWIP_SO_RCVTIMEO configuration option to enable/disable SO_RCVTIMEO
     on UDP sockets/netconn.
-  
+
   2007-03-08 Simon Goldschmidt
   * snmp_msg.h, msg_in.c: SNMP UDP ports can be configured at compile time.
 
@@ -730,7 +730,7 @@ HISTORY
   2007-03-20 Frédéric Bernon
   * memp.h, stats.c: Fix stats_display function where memp_names table wasn't
     synchronized with memp.h.
-  
+
   2007-03-20 Frédéric Bernon
   * tcpip.c: Initialize tcpip's mbox, and verify if initialized in tcpip_input,
     tcpip_ethinput, tcpip_callback, tcpip_apimsg, to fix a init problem with 
@@ -743,10 +743,10 @@ HISTORY
   2007-03-19 Frédéric Bernon
   * api_msg.h, api_msg.c, tcpip.h, tcpip.c: Add return types to tcpip_apimsg()
     and api_msg_post().
-  
+
   2007-03-19 Frédéric Bernon
   * Remove unimplemented "memp_realloc" function from memp.h.
-  
+
   2007-03-11 Simon Goldschmidt
   * pbuf.c: checked in patch #5796: pbuf_alloc: len field claculation caused
     memory corruption.
@@ -785,15 +785,15 @@ HISTORY
     (protecting ARP layer against concurrent access). You can also disable
     old code using tcp_input with new define ETHARP_TCPIP_INPUT set to 0.
     Older ports have to use tcpip_ethinput.
-  
+
   2007-03-06 Simon Goldschmidt (based on patch from Dmitry Potapov)
   * err.h, err.c: fixed compiler warning "initialization dircards qualifiers
     from pointer target type"
-  
+
   2007-03-05 Frédéric Bernon
   * opt.h, sockets.h: add new configuration options (LWIP_POSIX_SOCKETS_IO_NAMES,
     ETHARP_TRUST_IP_MAC, review SO_REUSE)
-  
+
   2007-03-04 Frédéric Bernon
   * api_msg.c: Remove some compiler warnings : parameter "pcb" was never
     referenced.
@@ -802,7 +802,7 @@ HISTORY
   * api_lib.c: Fix "[patch #5764] api_lib.c cleanup: after patch #5687" (from
     Dmitry Potapov).
     The api_msg struct stay on the stack (not moved to netconn struct).
-  
+
   2007-03-04 Simon Goldschmidt (based on patch from Dmitry Potapov)
   * pbuf.c: Fix BUG#19168 - pbuf_free can cause deadlock (if
     SYS_LIGHTWEIGHT_PROT=1 & freeing PBUF_RAM when mem_sem is not available)
@@ -859,7 +859,7 @@ HISTORY
   2006-08-08 Christiaan Simons
   * etharp.{c,h}: added etharp_find_addr() to read
     (stable) ethernet/IP address pair from ARP table
-  
+
   2006-07-14 Christiaan Simons
   * mib_structs.c: added
   * include/lwip/snmp_structs.h: added
@@ -871,7 +871,7 @@ HISTORY
   * snmp/msg_{in,out}.c added
   * include/lwip/snmp_asn1.h added
   * include/lwip/snmp_msg.h added
-  * doc/snmp_agent.txt added  
+  * doc/snmp_agent.txt added
 
   2006-03-29 Christiaan Simons
   * inet.c, inet.h: Added platform byteswap support.
@@ -879,7 +879,7 @@ HISTORY
     optional LWIP_PLATFORM_HTONS(), LWIP_PLATFORM_HTONL() macros.
 
   ++ Bug fixes:
-  
+
   2006-11-30 Christiaan Simons
   * dhcp.c: Fixed false triggers of request_timeout.
 
@@ -901,7 +901,7 @@ HISTORY
 
   2006-08-07 Christiaan Simons
   * api_msg.c: Flushing TCP output in do_close() (bug #15926).
-    
+
   2006-06-27 Christiaan Simons
   * api_msg.c: Applied patch for cold case (bug #11135).
     In accept_function() ensure newconn->callback is always initialized.
@@ -935,7 +935,7 @@ HISTORY
   2005-12-20  Leon Woestenberg <leon.woestenberg@gmx.net>
   * tcp.c: Remove PCBs which stay in LAST_ACK state too long. Patch
     submitted by Mitrani Hiroshi.
-    
+
   2005-12-15  Christiaan Simons
   * inet.c: Disabled the added summing routine to preserve code space.
 
@@ -951,7 +951,7 @@ HISTORY
   2005-11-25  Christiaan Simons
   * udp.c tcp.c: Removed SO_REUSE hack. Should reside in socket code only.
   * *.c: introduced cc.h LWIP_DEBUG formatters matching the u16_t, s16_t,
-    u32_t, s32_t typedefs. This solves most debug word-length assumes.  
+    u32_t, s32_t typedefs. This solves most debug word-length assumes.
 
   2005-07-17 Leon Woestenberg <leon.woestenberg@gmx.net>
   * inet.c: Fixed unaligned 16-bit access in the standard checksum
@@ -980,7 +980,7 @@ HISTORY
     ETHARP_MAX_PENDING now should be at least 2. This prevents
     the counter from reaching 0 right away (which would allow
     too little time for ARP responses to be received).
-    
+
   2004-11-25 Leon Woestenberg <leon.woestenberg@gmx.net>
   * dhcp.c: Decline messages were not multicast but unicast.
   * etharp.c: ETHARP_CREATE is renamed to ETHARP_TRY_HARD.
@@ -1038,7 +1038,7 @@ HISTORY
     of raw_recv() in raw.h and so avoid compiler error.
   * sockets.c: Added trivial (int) cast to keep compiler happier.
   * ip.c, netif.c Changed debug statements to use the tidier ip4_addrN() macros.
-  
+
 (STABLE-1_0_0)
 
   ++ Changes:
@@ -1078,7 +1078,7 @@ HISTORY
     is not queued, and gets lost. Fixed the case where the packets destination
     address is already known; we now always queue the packet and perform an ARP
     request.
-  
+
 (STABLE-0_7_0)
 
   ++ Bug fixes:
diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index 89bb605d..570e9bf2 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -39,14 +39,16 @@
 /* This is the part of the API that is linked with
    the application */
 
-#include <string.h>
 #include "lwip/opt.h"
+
+#if LWIP_NETCONN /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/api.h"
 #include "lwip/api_msg.h"
 #include "lwip/tcpip.h"
 #include "lwip/memp.h"
 
-#if !NO_SYS
+#include <string.h>
 
 /**
  * Create a new netconn (of a specific type) that has a callback function.
@@ -185,9 +187,12 @@ netconn_peer(struct netconn *conn, struct ip_addr *addr, u16_t *port)
 {
   LWIP_ERROR("netconn_peer: invalid conn", (conn != NULL), return ERR_ARG;);
   switch (NETCONNTYPE_GROUP(conn->type)) {
+#if LWIP_RAW
   case NETCONN_RAW:
     /* return an error as connecting is only a helper for upper layers */
     return ERR_CONN;
+#endif /* LWIP_RAW */
+#if LWIP_UDP
   case NETCONN_UDP:
     if (conn->pcb.udp == NULL ||
   ((conn->pcb.udp->flags & UDP_FLAGS_CONNECTED) == 0))
@@ -195,12 +200,15 @@ netconn_peer(struct netconn *conn, struct ip_addr *addr, u16_t *port)
     *addr = (conn->pcb.udp->remote_ip);
     *port = conn->pcb.udp->remote_port;
     break;
+#endif /* LWIP_UDP */
+#if LWIP_TCP
   case NETCONN_TCP:
     if (conn->pcb.tcp == NULL)
       return ERR_CONN;
     *addr = (conn->pcb.tcp->remote_ip);
     *port = conn->pcb.tcp->remote_port;
     break;
+#endif /* LWIP_TCP */
   }
   return ERR_OK;
 }
@@ -221,18 +229,24 @@ netconn_addr(struct netconn *conn, struct ip_addr **addr, u16_t *port)
   LWIP_ERROR("netconn_addr: invalid addr", (addr != NULL), return ERR_ARG;);
   LWIP_ERROR("netconn_addr: invalid port", (port != NULL), return ERR_ARG;);
   switch (NETCONNTYPE_GROUP(conn->type)) {
+#if LWIP_RAW
   case NETCONN_RAW:
     *addr = &(conn->pcb.raw->local_ip);
     *port = conn->pcb.raw->protocol;
     break;
+#endif /* LWIP_RAW */
+#if LWIP_UDP
   case NETCONN_UDP:
     *addr = &(conn->pcb.udp->local_ip);
     *port = conn->pcb.udp->local_port;
     break;
+#endif /* LWIP_UDP */
+#if LWIP_TCP
   case NETCONN_TCP:
     *addr = &(conn->pcb.tcp->local_ip);
     *port = conn->pcb.tcp->local_port;
     break;
+#endif /* LWIP_TCP */
   }
   return ERR_OK;
 }
@@ -607,4 +621,4 @@ netconn_join_leave_group(struct netconn *conn,
 }
 #endif /* LWIP_IGMP */
 
-#endif /* !NO_SYS */
+#endif /* LWIP_NETCONN */
diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index 9c4439c4..afc2b737 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -37,15 +37,15 @@
  */
 
 #include "lwip/opt.h"
-#include "lwip/arch.h"
+
+#if LWIP_NETCONN /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/api_msg.h"
 #include "lwip/memp.h"
 #include "lwip/sys.h"
 #include "lwip/tcpip.h"
 #include "lwip/igmp.h"
 
-#if !NO_SYS
-
 /* forward declarations */
 #if LWIP_TCP
 static err_t do_writemore(struct netconn *conn);
@@ -931,4 +931,4 @@ do_join_leave_group(struct api_msg_msg *msg)
 }
 #endif /* LWIP_IGMP */
 
-#endif /* !NO_SYS */
+#endif /* LWIP_NETCONN */
diff --git a/src/api/netbuf.c b/src/api/netbuf.c
index 0e03177c..27120eb5 100644
--- a/src/api/netbuf.c
+++ b/src/api/netbuf.c
@@ -36,11 +36,15 @@
  *
  */
 
-#include <string.h>
 #include "lwip/opt.h"
+
+#if LWIP_NETCONN /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/netbuf.h"
 #include "lwip/memp.h"
 
+#include <string.h>
+
 /**
  * Create (allocate) and initialize a new netbuf.
  * The netbuf doesn't yet contain a packet buffer!
@@ -227,3 +231,5 @@ netbuf_first(struct netbuf *buf)
   LWIP_ERROR("netbuf_free: invalid buf", (buf != NULL), return;);
   buf->ptr = buf->p;
 }
+
+#endif /* LWIP_NETCONN */
diff --git a/src/api/netifapi.c b/src/api/netifapi.c
index 530ceeb3..e11efd91 100644
--- a/src/api/netifapi.c
+++ b/src/api/netifapi.c
@@ -32,12 +32,12 @@
  */
 
 #include "lwip/opt.h"
-#include "lwip/arch.h"
+
+#if LWIP_NETIF_API /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/netifapi.h"
 #include "lwip/tcpip.h"
 
-#if LWIP_NETIF_API
-
 /**
  * Call netif_add() in a thread-safe way by running that function inside the
  * tcpip_thread context.
diff --git a/src/api/sockets.c b/src/api/sockets.c
index 581c1dff..4287408a 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -38,20 +38,19 @@
  *
  */
 
-#include "lwip/sockets.h"
-
-#include <string.h>
-
 #include "lwip/opt.h"
+
+#if LWIP_SOCKET /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/sockets.h"
 #include "lwip/api.h"
-#include "lwip/arch.h"
 #include "lwip/sys.h"
 #include "lwip/igmp.h"
 #include "lwip/inet.h"
 #include "lwip/tcp.h"
 #include "lwip/tcpip.h"
 
-#if !NO_SYS
+#include <string.h>
 
 #define NUM_SOCKETS MEMP_NUM_NETCONN
 
@@ -1081,11 +1080,13 @@ int lwip_getsockopt(int s, int level, int optname, void *optval, socklen_t *optl
       if (*optlen < sizeof(int)) {
         err = EINVAL;
       }
+#if LWIP_UDP
       if ((sock->conn->type != NETCONN_UDP) ||
           ((udp_flags(sock->conn->pcb.udp) & UDP_FLAGS_UDPLITE) != 0)) {
         /* this flag is only available for UDP, not for UDP lite */
         err = EAFNOSUPPORT;
       }
+#endif /* LWIP_UDP */
       break;
 
     default:
@@ -1278,9 +1279,11 @@ static void lwip_getsockopt_internal(void *arg)
       *(int *)optval = sock->conn->recv_timeout;
       break;
 #endif /* LWIP_SO_RCVTIMEO */
+#if LWIP_UDP
     case SO_NO_CHECK:
       *(int*)optval = (udp_flags(sock->conn->pcb.udp) & UDP_FLAGS_NOCHKSUM) ? 1 : 0;
       break;
+#endif /* LWIP_UDP*/
     }  /* switch (optname) */
     break;
 
@@ -1405,11 +1408,13 @@ int lwip_setsockopt(int s, int level, int optname, const void *optval, socklen_t
       if (optlen < sizeof(int)) {
         err = EINVAL;
       }
+#if LWIP_UDP
       if ((sock->conn->type != NETCONN_UDP) ||
           ((udp_flags(sock->conn->pcb.udp) & UDP_FLAGS_UDPLITE) != 0)) {
         /* this flag is only available for UDP, not for UDP lite */
         err = EAFNOSUPPORT;
       }
+#endif /* LWIP_UDP */
       break;
     default:
       LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, SOL_SOCKET, UNIMPL: optname=0x%x, ..)\n",
@@ -1585,11 +1590,12 @@ static void lwip_setsockopt_internal(void *arg)
       LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, SOL_SOCKET, optname=0x%x, ..) -> %s\n",
                   s, optname, (*(int*)optval?"on":"off")));
       break;
-#if LWIP_SO_RCVTIMEO      
+#if LWIP_SO_RCVTIMEO
     case SO_RCVTIMEO:
       sock->conn->recv_timeout = ( *(int*)optval );
       break;
 #endif /* LWIP_SO_RCVTIMEO */
+#if LWIP_UDP
     case SO_NO_CHECK:
       if (*(int*)optval) {
         udp_setflags(sock->conn->pcb.udp, udp_flags(sock->conn->pcb.udp) | UDP_FLAGS_NOCHKSUM);
@@ -1597,6 +1603,7 @@ static void lwip_setsockopt_internal(void *arg)
         udp_setflags(sock->conn->pcb.udp, udp_flags(sock->conn->pcb.udp) & ~UDP_FLAGS_NOCHKSUM);
       }
       break;
+#endif /* LWIP_UDP */
     }  /* switch (optname) */
     break;
 
@@ -1755,4 +1762,4 @@ int lwip_ioctl(int s, long cmd, void *argp)
   } /* switch (cmd) */
 }
 
-#endif /* !NO_SYS */
+#endif /* LWIP_SOCKET */
diff --git a/src/api/tcpip.c b/src/api/tcpip.c
index 476fa7ae..f9ccc736 100644
--- a/src/api/tcpip.c
+++ b/src/api/tcpip.c
@@ -38,21 +38,17 @@
 
 #include "lwip/opt.h"
 
-#include "lwip/sys.h"
+#if !NO_SYS /* don't build if not configured for use in lwipopts.h */
 
+#include "lwip/sys.h"
 #include "lwip/memp.h"
 #include "lwip/pbuf.h"
-
-#include "netif/etharp.h"
-#include "netif/ppp_oe.h"
-
 #include "lwip/ip_frag.h"
 #include "lwip/igmp.h"
-
 #include "lwip/tcpip.h"
 #include "lwip/init.h"
-
-#if !NO_SYS
+#include "netif/etharp.h"
+#include "netif/ppp_oe.h"
 
 /* global variables */
 static void (* tcpip_init_done)(void *arg) = NULL;
diff --git a/src/core/dhcp.c b/src/core/dhcp.c
index 40b11992..572591fe 100644
--- a/src/core/dhcp.c
+++ b/src/core/dhcp.c
@@ -67,23 +67,23 @@
  * to remove the DHCP client.
  *
  */
- 
-#include <string.h>
- 
+
+#include "lwip/opt.h"
+
+#if LWIP_DHCP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/stats.h"
 #include "lwip/mem.h"
 #include "lwip/udp.h"
 #include "lwip/ip_addr.h"
 #include "lwip/netif.h"
 #include "lwip/inet.h"
-#include "netif/etharp.h"
-
 #include "lwip/sys.h"
-#include "lwip/opt.h"
 #include "lwip/dhcp.h"
 #include "lwip/autoip.h"
+#include "netif/etharp.h"
 
-#if LWIP_DHCP /* don't build if not configured for use in lwipopts.h */
+#include <string.h>
 
 /** global transaction identifier, must be
  *  unique for each DHCP request. We simply increment, starting
diff --git a/src/core/inet.c b/src/core/inet.c
index 008595d1..76fa356f 100644
--- a/src/core/inet.c
+++ b/src/core/inet.c
@@ -39,11 +39,8 @@
 
 #include "lwip/opt.h"
 
-#include "lwip/arch.h"
-
 #include "lwip/def.h"
 #include "lwip/inet.h"
-
 #include "lwip/sys.h"
 
 /* These are some reference implementations of the checksum algorithm, with the
diff --git a/src/core/init.c b/src/core/init.c
index 6f15e1fe..f7de191e 100644
--- a/src/core/init.c
+++ b/src/core/init.c
@@ -37,6 +37,7 @@
  */
 
 #include "lwip/opt.h"
+
 #include "lwip/init.h"
 #include "lwip/stats.h"
 #include "lwip/sys.h"
@@ -45,14 +46,13 @@
 #include "lwip/pbuf.h"
 #include "lwip/netif.h"
 #include "lwip/sockets.h"
-#include "netif/etharp.h"
 #include "lwip/ip.h"
 #include "lwip/raw.h"
 #include "lwip/udp.h"
 #include "lwip/tcp.h"
 #include "lwip/autoip.h"
 #include "lwip/igmp.h"
-
+#include "netif/etharp.h"
 
 /* Compile-time sanity checks for configuration errors.
  * These can be done independently of LWIP_DEBUG, without penalty.
diff --git a/src/core/ipv4/autoip.c b/src/core/ipv4/autoip.c
index 33df78c9..bef32de9 100644
--- a/src/core/ipv4/autoip.c
+++ b/src/core/ipv4/autoip.c
@@ -62,8 +62,10 @@
  *
  */
 
-#include <stdlib.h>
-#include <string.h>
+#include "lwip/opt.h"
+
+#if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/mem.h"
 #include "lwip/udp.h"
 #include "lwip/ip_addr.h"
@@ -71,7 +73,8 @@
 #include "lwip/autoip.h"
 #include "netif/etharp.h"
 
-#if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */
+#include <stdlib.h>
+#include <string.h>
 
 /* pseudo random macro based on netif informations. You could use "rand()" from the C Library if you define LWIP_AUTOIP_RAND in lwipopts.h */
 #ifndef LWIP_AUTOIP_RAND
diff --git a/src/core/ipv4/icmp.c b/src/core/ipv4/icmp.c
index 6163132b..e9dec868 100644
--- a/src/core/ipv4/icmp.c
+++ b/src/core/ipv4/icmp.c
@@ -39,9 +39,10 @@
 /* Some ICMP messages should be passed to the transport protocols. This
    is not implemented. */
 
-#include <string.h>
-
 #include "lwip/opt.h"
+
+#if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/icmp.h"
 #include "lwip/inet.h"
 #include "lwip/ip.h"
@@ -49,7 +50,7 @@
 #include "lwip/stats.h"
 #include "lwip/snmp.h"
 
-#if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
+#include <string.h>
 
 /**
  * Processes ICMP input packets, called from ip_input().
diff --git a/src/core/ipv4/igmp.c b/src/core/ipv4/igmp.c
index d5bc0b7f..1045d598 100644
--- a/src/core/ipv4/igmp.c
+++ b/src/core/ipv4/igmp.c
@@ -77,6 +77,10 @@ Steve Reynolds
  * Includes
  *----------------------------------------------------------------------------*/
 
+#include "lwip/opt.h"
+
+#if LWIP_IGMP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/debug.h"
 #include "lwip/def.h"
 #include "lwip/mem.h"
@@ -89,12 +93,8 @@ Steve Reynolds
 #include "lwip/stats.h"
 #include "lwip/igmp.h"
 
-#include "arch/perf.h"
-
 #include "string.h"
 
-#if LWIP_IGMP /* don't build if not configured for use in lwipopts.h */
-
 /*-----------------------------------------------------------------------------
  * Globales
  *----------------------------------------------------------------------------*/
diff --git a/src/core/ipv4/ip.c b/src/core/ipv4/ip.c
index c2117e97..de58019f 100644
--- a/src/core/ipv4/ip.c
+++ b/src/core/ipv4/ip.c
@@ -39,7 +39,6 @@
  */
 
 #include "lwip/opt.h"
-
 #include "lwip/def.h"
 #include "lwip/mem.h"
 #include "lwip/ip.h"
@@ -47,22 +46,14 @@
 #include "lwip/inet.h"
 #include "lwip/netif.h"
 #include "lwip/icmp.h"
+#include "lwip/igmp.h"
 #include "lwip/raw.h"
 #include "lwip/udp.h"
 #include "lwip/tcp.h"
-
-#include "lwip/stats.h"
-
-#include "arch/perf.h"
-
 #include "lwip/snmp.h"
-#if LWIP_DHCP
-#  include "lwip/dhcp.h"
-#endif /* LWIP_DHCP */
-
-#if LWIP_IGMP
-#  include "lwip/igmp.h"
-#endif /* LWIP_IGMP */
+#include "lwip/dhcp.h"
+#include "lwip/stats.h"
+#include "arch/perf.h"
 
 /**
  * Initializes the IP layer.
diff --git a/src/core/ipv4/ip_addr.c b/src/core/ipv4/ip_addr.c
index dafcd761..94bf4678 100644
--- a/src/core/ipv4/ip_addr.c
+++ b/src/core/ipv4/ip_addr.c
@@ -36,6 +36,7 @@
  *
  */
 
+#include "lwip/opt.h"
 #include "lwip/ip_addr.h"
 #include "lwip/inet.h"
 #include "lwip/netif.h"
diff --git a/src/core/ipv4/ip_frag.c b/src/core/ipv4/ip_frag.c
index ff23ac43..c34fd223 100644
--- a/src/core/ipv4/ip_frag.c
+++ b/src/core/ipv4/ip_frag.c
@@ -37,8 +37,6 @@
  * 
  */
 
-#include <string.h>
-
 #include "lwip/opt.h"
 #include "lwip/ip.h"
 #include "lwip/ip_frag.h"
@@ -46,6 +44,8 @@
 #include "lwip/snmp.h"
 #include "lwip/stats.h"
 
+#include <string.h>
+
 #if IP_REASSEMBLY
 static u8_t ip_reassbuf[IP_HLEN + IP_REASS_BUFSIZE];
 static u8_t ip_reassbitmap[IP_REASS_BUFSIZE / (8 * 8) + 1];
diff --git a/src/core/ipv6/icmp6.c b/src/core/ipv6/icmp6.c
index ec5d2adb..d552e63b 100644
--- a/src/core/ipv6/icmp6.c
+++ b/src/core/ipv6/icmp6.c
@@ -35,15 +35,14 @@
 
 #include "lwip/opt.h"
 
+#if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/icmp.h"
 #include "lwip/inet.h"
 #include "lwip/ip.h"
 #include "lwip/def.h"
-
 #include "lwip/stats.h"
 
-#if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
-
 void
 icmp_input(struct pbuf *p, struct netif *inp)
 {
diff --git a/src/core/ipv6/ip6_addr.c b/src/core/ipv6/ip6_addr.c
index f35b40ab..2da6cea4 100644
--- a/src/core/ipv6/ip6_addr.c
+++ b/src/core/ipv6/ip6_addr.c
@@ -34,7 +34,6 @@
 #include "lwip/ip_addr.h"
 #include "lwip/inet.h"
 
-
 u8_t
 ip_addr_netcmp(struct ip_addr *addr1, struct ip_addr *addr2,
                 struct ip_addr *mask)
diff --git a/src/core/mem.c b/src/core/mem.c
index 115e126d..1adad3b5 100644
--- a/src/core/mem.c
+++ b/src/core/mem.c
@@ -37,18 +37,17 @@
  *
  */
 
-#include <string.h>
-
-#include "lwip/arch.h"
 #include "lwip/opt.h"
+
+#if !MEM_LIBC_MALLOC /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/def.h"
 #include "lwip/mem.h"
-
 #include "lwip/sys.h"
-
 #include "lwip/stats.h"
 
-#if !MEM_LIBC_MALLOC
+#include <string.h>
+
 #if MEM_USE_POOLS
 /* lwIP head implemented with different sized pools */
 
@@ -511,4 +510,5 @@ void *mem_calloc(size_t count, size_t size)
   }
   return p;
 }
+
 #endif /* !MEM_LIBC_MALLOC */
diff --git a/src/core/memp.c b/src/core/memp.c
index 05d18dd1..0e1d7943 100644
--- a/src/core/memp.c
+++ b/src/core/memp.c
@@ -36,9 +36,8 @@
  *
  */
 
-#include <string.h>
-
 #include "lwip/opt.h"
+
 #include "lwip/memp.h"
 #include "lwip/pbuf.h"
 #include "lwip/udp.h"
@@ -50,10 +49,9 @@
 #include "lwip/tcpip.h"
 #include "lwip/sys.h"
 #include "lwip/stats.h"
-
-#if ARP_QUEUEING
 #include "netif/etharp.h"
-#endif
+
+#include <string.h>
 
 struct memp {
   struct memp *next;
diff --git a/src/core/netif.c b/src/core/netif.c
index 30f97cc5..e00a2d60 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -44,10 +44,7 @@
 #include "lwip/tcp.h"
 #include "lwip/snmp.h"
 #include "lwip/igmp.h"
-
-#if LWIP_ARP
 #include "netif/etharp.h"
-#endif /* LWIP_ARP */
 
 #if LWIP_NETIF_STATUS_CALLBACK
 #define NETIF_STATUS_CALLBACK(n) { if (n->status_callback) (n->status_callback)(n); }
diff --git a/src/core/pbuf.c b/src/core/pbuf.c
index fb7c08d4..ef97298b 100644
--- a/src/core/pbuf.c
+++ b/src/core/pbuf.c
@@ -61,9 +61,8 @@
  *
  */
 
-#include <string.h>
-
 #include "lwip/opt.h"
+
 #include "lwip/stats.h"
 #include "lwip/def.h"
 #include "lwip/mem.h"
@@ -72,6 +71,8 @@
 #include "lwip/sys.h"
 #include "arch/perf.h"
 
+#include <string.h>
+
 #define SIZEOF_STRUCT_PBUF        LWIP_MEM_ALIGN_SIZE(sizeof(struct pbuf))
 /* Since the pool is created in memp, PBUF_POOL_BUFSIZE will be automatically
    aligned there. Therefore, PBUF_POOL_BUFSIZE_ALIGNED can be used here. */
diff --git a/src/core/raw.c b/src/core/raw.c
index fb3f97b8..421c4933 100644
--- a/src/core/raw.c
+++ b/src/core/raw.c
@@ -38,23 +38,21 @@
  *
  */
 
-#include <string.h>
-
 #include "lwip/opt.h"
 
+#if LWIP_RAW /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/def.h"
 #include "lwip/memp.h"
 #include "lwip/inet.h"
 #include "lwip/ip_addr.h"
 #include "lwip/netif.h"
 #include "lwip/raw.h"
-
 #include "lwip/stats.h"
-
-#include "arch/perf.h"
 #include "lwip/snmp.h"
+#include "arch/perf.h"
 
-#if LWIP_RAW
+#include <string.h>
 
 /** The list of RAW PCBs */
 static struct raw_pcb *raw_pcbs = NULL;
diff --git a/src/core/snmp/asn1_dec.c b/src/core/snmp/asn1_dec.c
index eec4380e..650fb403 100644
--- a/src/core/snmp/asn1_dec.c
+++ b/src/core/snmp/asn1_dec.c
@@ -36,7 +36,8 @@
 
 #include "lwip/opt.h"
 
-#if LWIP_SNMP
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/snmp_asn1.h"
 
 /**
@@ -654,4 +655,3 @@ snmp_asn1_dec_raw(struct pbuf *p, u16_t ofs, u16_t len, u16_t raw_len, u8_t *raw
 }
 
 #endif /* LWIP_SNMP */
-
diff --git a/src/core/snmp/asn1_enc.c b/src/core/snmp/asn1_enc.c
index 4d04f285..77af6b4b 100644
--- a/src/core/snmp/asn1_enc.c
+++ b/src/core/snmp/asn1_enc.c
@@ -36,7 +36,8 @@
 
 #include "lwip/opt.h"
 
-#if LWIP_SNMP
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/snmp_asn1.h"
 
 /**
diff --git a/src/core/snmp/mib2.c b/src/core/snmp/mib2.c
index 6f37f938..8c379343 100644
--- a/src/core/snmp/mib2.c
+++ b/src/core/snmp/mib2.c
@@ -37,17 +37,17 @@
 
 #include "lwip/opt.h"
 
-#if LWIP_SNMP
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
 
 #include "lwip/snmp.h"
 #include "lwip/netif.h"
-#include "netif/etharp.h"
 #include "lwip/ip.h"
 #include "lwip/ip_frag.h"
 #include "lwip/tcp.h"
 #include "lwip/udp.h"
 #include "lwip/snmp_asn1.h"
 #include "lwip/snmp_structs.h"
+#include "netif/etharp.h"
 
 /**
  * IANA assigned enterprise ID for lwIP is 26381
diff --git a/src/core/snmp/mib_structs.c b/src/core/snmp/mib_structs.c
index 939e220e..ba78f857 100644
--- a/src/core/snmp/mib_structs.c
+++ b/src/core/snmp/mib_structs.c
@@ -34,12 +34,11 @@
 
 #include "lwip/opt.h"
 
-#if LWIP_SNMP
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/snmp_structs.h"
 #include "lwip/mem.h"
 
-
-
 /** .iso.org.dod.internet address prefix, @see snmp_iso_*() */
 const s32_t prefix[4] = {1, 3, 6, 1};
 
@@ -1182,4 +1181,3 @@ snmp_iso_prefix_expand(u8_t ident_len, s32_t *ident, struct snmp_obj_id *oidret)
 }
 
 #endif /* LWIP_SNMP */
-
diff --git a/src/core/snmp/msg_in.c b/src/core/snmp/msg_in.c
index 8a558da4..ab8b5216 100644
--- a/src/core/snmp/msg_in.c
+++ b/src/core/snmp/msg_in.c
@@ -34,19 +34,18 @@
 
 #include "lwip/opt.h"
 
-#if LWIP_SNMP
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
 
-#include <string.h>
 #include "lwip/ip_addr.h"
 #include "lwip/mem.h"
 #include "lwip/udp.h"
 #include "lwip/stats.h"
-
 #include "lwip/snmp.h"
 #include "lwip/snmp_asn1.h"
 #include "lwip/snmp_msg.h"
 #include "lwip/snmp_structs.h"
 
+#include <string.h>
 
 /* public (non-static) constants */
 /** SNMP v1 == 0 */
diff --git a/src/core/snmp/msg_out.c b/src/core/snmp/msg_out.c
index 81d051c2..b705aaca 100644
--- a/src/core/snmp/msg_out.c
+++ b/src/core/snmp/msg_out.c
@@ -44,11 +44,10 @@
 
 #include "lwip/opt.h"
 
-#if LWIP_SNMP
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
 
 #include "lwip/udp.h"
 #include "lwip/netif.h"
-
 #include "lwip/snmp.h"
 #include "lwip/snmp_asn1.h"
 #include "lwip/snmp_msg.h"
diff --git a/src/core/stats.c b/src/core/stats.c
index add1e6e0..640baab5 100644
--- a/src/core/stats.c
+++ b/src/core/stats.c
@@ -36,17 +36,16 @@
  *
  */
 
-#include <string.h>
-
 #include "lwip/opt.h"
 
-#include "lwip/def.h"
+#if LWIP_STATS /* don't build if not configured for use in lwipopts.h */
 
+#include "lwip/def.h"
 #include "lwip/stats.h"
 #include "lwip/mem.h"
 
+#include <string.h>
 
-#if LWIP_STATS
 struct stats_ lwip_stats;
 
 void
@@ -141,5 +140,6 @@ stats_display(void)
 #endif
 }
 #endif /* LWIP_STATS_DISPLAY */
+
 #endif /* LWIP_STATS */
 
diff --git a/src/core/sys.c b/src/core/sys.c
index 2c4f32c2..8f209277 100644
--- a/src/core/sys.c
+++ b/src/core/sys.c
@@ -36,14 +36,15 @@
  *
  */
 
-#include "lwip/sys.h"
 #include "lwip/opt.h"
+
+#if (NO_SYS == 0) /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/sys.h"
 #include "lwip/def.h"
 #include "lwip/memp.h"
 #include "lwip/tcpip.h"
 
-#if (NO_SYS == 0)
-
 /**
  * Struct used for sys_sem_wait_timeout() to tell wether the time
  * has run out or the semaphore has really become available.
diff --git a/src/core/tcp.c b/src/core/tcp.c
index afdc0f6c..ae14bb1c 100644
--- a/src/core/tcp.c
+++ b/src/core/tcp.c
@@ -40,16 +40,17 @@
  *
  */
 
-#include <string.h>
-
 #include "lwip/opt.h"
+
+#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/def.h"
 #include "lwip/mem.h"
 #include "lwip/memp.h"
 #include "lwip/snmp.h"
-
 #include "lwip/tcp.h"
-#if LWIP_TCP
+
+#include <string.h>
 
 /* Incremented every coarse grained timer shot (typically every 500 ms). */
 u32_t tcp_ticks;
@@ -1322,4 +1323,5 @@ tcp_pcbs_sane(void)
   return 1;
 }
 #endif /* TCP_DEBUG */
+
 #endif /* LWIP_TCP */
diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index fca912e1..8e212cc4 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -41,22 +41,21 @@
  *
  */
 
-#include "lwip/def.h"
 #include "lwip/opt.h"
 
+#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/def.h"
 #include "lwip/ip_addr.h"
 #include "lwip/netif.h"
 #include "lwip/mem.h"
 #include "lwip/memp.h"
-
 #include "lwip/inet.h"
 #include "lwip/tcp.h"
-
 #include "lwip/stats.h"
-#include "arch/perf.h"
 #include "lwip/snmp.h"
+#include "arch/perf.h"
 
-#if LWIP_TCP
 /* These variables are global to all functions involved in the input
    processing of TCP segments. They are set by the tcp_input()
    function. */
@@ -1279,4 +1278,5 @@ tcp_parseopt(struct tcp_pcb *pcb)
     }
   }
 }
+
 #endif /* LWIP_TCP */
diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index 8aee39cb..0eabea4e 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -38,10 +38,11 @@
  *
  */
 
-#include <string.h>
+#include "lwip/opt.h"
+
+#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
 
 #include "lwip/def.h"
-#include "lwip/opt.h"
 #include "lwip/mem.h"
 #include "lwip/memp.h"
 #include "lwip/sys.h"
@@ -52,7 +53,7 @@
 #include "lwip/stats.h"
 #include "lwip/snmp.h"
 
-#if LWIP_TCP
+#include <string.h>
 
 /* Forward declarations.*/
 static void tcp_output_segment(struct tcp_seg *seg, struct tcp_pcb *pcb);
diff --git a/src/core/udp.c b/src/core/udp.c
index 95dda50c..8f259a1c 100644
--- a/src/core/udp.c
+++ b/src/core/udp.c
@@ -43,10 +43,10 @@
  *
  */
 
-#include <string.h>
-
 #include "lwip/opt.h"
 
+#if LWIP_UDP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/def.h"
 #include "lwip/memp.h"
 #include "lwip/inet.h"
@@ -54,14 +54,13 @@
 #include "lwip/netif.h"
 #include "lwip/udp.h"
 #include "lwip/icmp.h"
-
 #include "lwip/stats.h"
-
-#include "arch/perf.h"
 #include "lwip/snmp.h"
+#include "arch/perf.h"
+
+#include <string.h>
 
 /* The list of UDP PCBs */
-#if LWIP_UDP
 /* exported in udp.h (was static) */
 struct udp_pcb *udp_pcbs = NULL;
 
diff --git a/src/include/ipv4/lwip/autoip.h b/src/include/ipv4/lwip/autoip.h
index 2ef530d7..076a2ed2 100644
--- a/src/include/ipv4/lwip/autoip.h
+++ b/src/include/ipv4/lwip/autoip.h
@@ -45,6 +45,9 @@
 #define __LWIP_AUTOIP_H__
 
 #include "lwip/opt.h"
+
+#if LWIP_AUTOIP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/netif.h"
 #include "lwip/udp.h"
 #include "netif/etharp.h"
@@ -97,4 +100,6 @@ void autoip_arp_reply(struct netif *netif, struct etharp_hdr *hdr);
 /** Has to be called in loop every AUTOIP_TMR_INTERVAL milliseconds */
 void autoip_tmr(void);
 
+#endif /* LWIP_AUTOIP */
+
 #endif /* __LWIP_AUTOIP_H__ */
diff --git a/src/include/ipv4/lwip/icmp.h b/src/include/ipv4/lwip/icmp.h
index 072e17e4..59a31f9c 100644
--- a/src/include/ipv4/lwip/icmp.h
+++ b/src/include/ipv4/lwip/icmp.h
@@ -32,16 +32,14 @@
 #ifndef __LWIP_ICMP_H__
 #define __LWIP_ICMP_H__
 
-#include "lwip/arch.h"
-
 #include "lwip/opt.h"
-#include "lwip/pbuf.h"
-
-#include "lwip/ip_addr.h"
-#include "lwip/netif.h"
 
 #if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
 
+#include "lwip/pbuf.h"
+#include "lwip/ip_addr.h"
+#include "lwip/netif.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/src/include/ipv4/lwip/inet.h b/src/include/ipv4/lwip/inet.h
index 2725150c..6dfad143 100644
--- a/src/include/ipv4/lwip/inet.h
+++ b/src/include/ipv4/lwip/inet.h
@@ -32,9 +32,8 @@
 #ifndef __LWIP_INET_H__
 #define __LWIP_INET_H__
 
-#include "lwip/arch.h"
-
 #include "lwip/opt.h"
+
 #include "lwip/pbuf.h"
 #include "lwip/ip_addr.h"
 
diff --git a/src/include/ipv4/lwip/ip.h b/src/include/ipv4/lwip/ip.h
index dc50b73d..47bd55d5 100644
--- a/src/include/ipv4/lwip/ip.h
+++ b/src/include/ipv4/lwip/ip.h
@@ -32,15 +32,13 @@
 #ifndef __LWIP_IP_H__
 #define __LWIP_IP_H__
 
-#include "lwip/arch.h"
+#include "lwip/opt.h"
 
 #include "lwip/def.h"
 #include "lwip/pbuf.h"
 #include "lwip/ip_addr.h"
-
 #include "lwip/err.h"
 
-
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/src/include/ipv4/lwip/ip_addr.h b/src/include/ipv4/lwip/ip_addr.h
index 84ec6e5d..0302277e 100644
--- a/src/include/ipv4/lwip/ip_addr.h
+++ b/src/include/ipv4/lwip/ip_addr.h
@@ -32,7 +32,7 @@
 #ifndef __LWIP_IP_ADDR_H__
 #define __LWIP_IP_ADDR_H__
 
-#include "lwip/arch.h"
+#include "lwip/opt.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/include/ipv6/lwip/icmp.h b/src/include/ipv6/lwip/icmp.h
index 987e3eb3..87e9ffd9 100644
--- a/src/include/ipv6/lwip/icmp.h
+++ b/src/include/ipv6/lwip/icmp.h
@@ -32,15 +32,13 @@
 #ifndef __LWIP_ICMP_H__
 #define __LWIP_ICMP_H__
 
-#include "lwip/arch.h"
-
 #include "lwip/opt.h"
-#include "lwip/pbuf.h"
-
-#include "lwip/netif.h"
 
 #if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
 
+#include "lwip/pbuf.h"
+#include "lwip/netif.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/src/include/ipv6/lwip/inet.h b/src/include/ipv6/lwip/inet.h
index 8228c205..de1a0b63 100644
--- a/src/include/ipv6/lwip/inet.h
+++ b/src/include/ipv6/lwip/inet.h
@@ -32,8 +32,6 @@
 #ifndef __LWIP_INET_H__
 #define __LWIP_INET_H__
 
-#include "lwip/arch.h"
-
 #include "lwip/opt.h"
 #include "lwip/pbuf.h"
 #include "lwip/ip_addr.h"
diff --git a/src/include/ipv6/lwip/ip_addr.h b/src/include/ipv6/lwip/ip_addr.h
index 02e6cee4..b2d8ae56 100644
--- a/src/include/ipv6/lwip/ip_addr.h
+++ b/src/include/ipv6/lwip/ip_addr.h
@@ -32,7 +32,7 @@
 #ifndef __LWIP_IP_ADDR_H__
 #define __LWIP_IP_ADDR_H__
 
-#include "lwip/arch.h"
+#include "lwip/opt.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/include/lwip/api.h b/src/include/lwip/api.h
index f16d8215..63df91dd 100644
--- a/src/include/lwip/api.h
+++ b/src/include/lwip/api.h
@@ -33,16 +33,16 @@
 #define __LWIP_API_H__
 
 #include "lwip/opt.h"
+
+#if LWIP_NETCONN /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/pbuf.h"
 #include "lwip/netbuf.h"
 #include "lwip/sys.h"
-
 #include "lwip/ip.h"
-
 #include "lwip/raw.h"
 #include "lwip/udp.h"
 #include "lwip/tcp.h"
-
 #include "lwip/err.h"
 
 #ifdef __cplusplus
@@ -122,7 +122,7 @@ struct netconn {
       this temporarily stores whether to wake up the original application task
       if data couldn't be sent in the first try. */
   u8_t write_delayed;
-#endif
+#endif /* LWIP_TCPIP_CORE_LOCKING */
 
   void (* callback)(struct netconn *, enum netconn_evt, u16_t len);
 };
@@ -174,4 +174,6 @@ err_t             netconn_join_leave_group (struct netconn *conn,
 }
 #endif
 
+#endif /* LWIP_NETCONN */
+
 #endif /* __LWIP_API_H__ */
diff --git a/src/include/lwip/api_msg.h b/src/include/lwip/api_msg.h
index c98f30e6..9f25f756 100644
--- a/src/include/lwip/api_msg.h
+++ b/src/include/lwip/api_msg.h
@@ -33,14 +33,14 @@
 #define __LWIP_API_MSG_H__
 
 #include "lwip/opt.h"
+
+#if LWIP_NETCONN /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/pbuf.h"
 #include "lwip/sys.h"
-
 #include "lwip/ip.h"
-
 #include "lwip/udp.h"
 #include "lwip/tcp.h"
-
 #include "lwip/api.h"
 
 #ifdef __cplusplus
@@ -102,4 +102,6 @@ void do_join_leave_group( struct api_msg_msg *msg);
 }
 #endif
 
+#endif /* LWIP_NETCONN */
+
 #endif /* __LWIP_API_MSG_H__ */
diff --git a/src/include/lwip/dhcp.h b/src/include/lwip/dhcp.h
index 8e5c8d2b..6f9f208c 100644
--- a/src/include/lwip/dhcp.h
+++ b/src/include/lwip/dhcp.h
@@ -5,6 +5,9 @@
 #define __LWIP_DHCP_H__
 
 #include "lwip/opt.h"
+
+#if LWIP_DHCP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/netif.h"
 #include "lwip/udp.h"
 
@@ -236,4 +239,6 @@ void dhcp_fine_tmr(void);
 }
 #endif
 
+#endif /* LWIP_DHCP */
+
 #endif /*__LWIP_DHCP_H__*/
diff --git a/src/include/lwip/init.h b/src/include/lwip/init.h
index 3f4be01b..c0869cfd 100644
--- a/src/include/lwip/init.h
+++ b/src/include/lwip/init.h
@@ -33,7 +33,6 @@
 #define __LWIP_INIT_H__
 
 #include "lwip/opt.h"
-#include "lwip/arch.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/include/lwip/mem.h b/src/include/lwip/mem.h
index 36c8781b..8018b18b 100644
--- a/src/include/lwip/mem.h
+++ b/src/include/lwip/mem.h
@@ -33,7 +33,6 @@
 #define __LWIP_MEM_H__
 
 #include "lwip/opt.h"
-#include "lwip/arch.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/include/lwip/memp.h b/src/include/lwip/memp.h
index 2d5f41e2..a0438633 100644
--- a/src/include/lwip/memp.h
+++ b/src/include/lwip/memp.h
@@ -91,4 +91,4 @@ void  memp_free(memp_t type, void *mem);
 }
 #endif
 
-#endif /* __LWIP_MEMP_H__  */
+#endif /* __LWIP_MEMP_H__ */
diff --git a/src/include/lwip/netifapi.h b/src/include/lwip/netifapi.h
index 19b84735..b9bb90e0 100644
--- a/src/include/lwip/netifapi.h
+++ b/src/include/lwip/netifapi.h
@@ -29,13 +29,14 @@
 #define __LWIP_NETIFAPI_H__
 
 #include "lwip/opt.h"
+
+#if LWIP_NETIF_API /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/sys.h"
 #include "lwip/netif.h"
 #include "lwip/dhcp.h"
 #include "lwip/autoip.h"
 
-#if LWIP_NETIF_API
-
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/src/include/lwip/pbuf.h b/src/include/lwip/pbuf.h
index f08c0af6..cbc17c34 100644
--- a/src/include/lwip/pbuf.h
+++ b/src/include/lwip/pbuf.h
@@ -33,7 +33,7 @@
 #ifndef __LWIP_PBUF_H__
 #define __LWIP_PBUF_H__
 
-#include "lwip/arch.h"
+#include "lwip/opt.h"
 #include "lwip/err.h"
 
 #ifdef __cplusplus
diff --git a/src/include/lwip/raw.h b/src/include/lwip/raw.h
index 6d141c51..56d21b18 100644
--- a/src/include/lwip/raw.h
+++ b/src/include/lwip/raw.h
@@ -32,7 +32,9 @@
 #ifndef __LWIP_RAW_H__
 #define __LWIP_RAW_H__
 
-#include "lwip/arch.h"
+#include "lwip/opt.h"
+
+#if LWIP_RAW /* don't build if not configured for use in lwipopts.h */
 
 #include "lwip/pbuf.h"
 #include "lwip/inet.h"
@@ -89,4 +91,6 @@ void             raw_init       (void);
 }
 #endif
 
+#endif /* LWIP_RAW */
+
 #endif /* __LWIP_RAW_H__ */
diff --git a/src/include/lwip/snmp.h b/src/include/lwip/snmp.h
index 9cf8fcba..36a087b4 100644
--- a/src/include/lwip/snmp.h
+++ b/src/include/lwip/snmp.h
@@ -79,8 +79,7 @@ enum snmp_ifType {
   snmp_ifType_frame_relay
 };
 
-/* SNMP support available? */
-#if defined(LWIP_SNMP) && (LWIP_SNMP > 0)
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
 
 /** fixed maximum length for object identifier type */
 #define LWIP_SNMP_OBJ_ID_LEN 32
@@ -350,7 +349,7 @@ void snmp_get_snmpenableauthentraps(u8_t *value);
 #define snmp_set_snmpenableauthentraps(value)
 #define snmp_get_snmpenableauthentraps(value)
 
-#endif
+#endif /* LWIP_SNMP */
 
 #ifdef __cplusplus
 }
diff --git a/src/include/lwip/snmp_asn1.h b/src/include/lwip/snmp_asn1.h
index a2a5bffc..3d70d330 100644
--- a/src/include/lwip/snmp_asn1.h
+++ b/src/include/lwip/snmp_asn1.h
@@ -94,4 +94,4 @@ err_t snmp_asn1_enc_raw(struct pbuf *p, u16_t ofs, u8_t raw_len, u8_t *raw);
 }
 #endif
 
-#endif
+#endif /* __LWIP_SNMP_ASN1_H__ */
diff --git a/src/include/lwip/snmp_msg.h b/src/include/lwip/snmp_msg.h
index 5eeead0b..d2028255 100644
--- a/src/include/lwip/snmp_msg.h
+++ b/src/include/lwip/snmp_msg.h
@@ -304,4 +304,4 @@ void snmp_authfail_trap(void);
 }
 #endif
 
-#endif
+#endif /* __LWIP_SNMP_MSG_H__ */
diff --git a/src/include/lwip/snmp_structs.h b/src/include/lwip/snmp_structs.h
index 22c96dc7..9f3f8a94 100644
--- a/src/include/lwip/snmp_structs.h
+++ b/src/include/lwip/snmp_structs.h
@@ -38,7 +38,8 @@
 #define __LWIP_SNMP_STRUCTS_H__
 
 #include "lwip/opt.h"
-#if LWIP_SNMP
+
+#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
 
 #include "lwip/snmp.h"
 
@@ -257,4 +258,5 @@ u8_t snmp_iso_prefix_expand(u8_t ident_len, s32_t *ident, struct snmp_obj_id *oi
 #endif
 
 #endif /* LWIP_SNMP */
-#endif
+
+#endif /* __LWIP_SNMP_STRUCTS_H__ */
diff --git a/src/include/lwip/sockets.h b/src/include/lwip/sockets.h
index d8d48c26..e1da4865 100644
--- a/src/include/lwip/sockets.h
+++ b/src/include/lwip/sockets.h
@@ -35,6 +35,9 @@
 #define __LWIP_SOCKETS_H__
 
 #include "lwip/opt.h"
+
+#if LWIP_SOCKET /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/ip_addr.h"
 #include "lwip/inet.h"
 
@@ -327,4 +330,6 @@ int lwip_ioctl(int s, long cmd, void *argp);
 }
 #endif
 
+#endif /* LWIP_SOCKET */
+
 #endif /* __LWIP_SOCKETS_H__ */
diff --git a/src/include/lwip/tcp.h b/src/include/lwip/tcp.h
index 5ae63a26..9d05f59e 100644
--- a/src/include/lwip/tcp.h
+++ b/src/include/lwip/tcp.h
@@ -32,14 +32,15 @@
 #ifndef __LWIP_TCP_H__
 #define __LWIP_TCP_H__
 
+#include "lwip/opt.h"
+
+/*#if LWIP_TCP*/ /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/sys.h"
 #include "lwip/mem.h"
-
 #include "lwip/pbuf.h"
-#include "lwip/opt.h"
 #include "lwip/ip.h"
 #include "lwip/icmp.h"
-
 #include "lwip/err.h"
 
 #ifdef __cplusplus
@@ -591,4 +592,6 @@ extern struct tcp_pcb *tcp_tmp_pcb;      /* Only used for temporary storage. */
 }
 #endif
 
+/*#endif*/ /* LWIP_TCP */
+
 #endif /* __LWIP_TCP_H__ */
diff --git a/src/include/lwip/tcpip.h b/src/include/lwip/tcpip.h
index 3695a5dc..f395c38c 100644
--- a/src/include/lwip/tcpip.h
+++ b/src/include/lwip/tcpip.h
@@ -64,9 +64,7 @@ err_t tcpip_apimsg(struct api_msg *apimsg);
 err_t tcpip_apimsg_lock(struct api_msg *apimsg);
 #endif /* LWIP_TCPIP_CORE_LOCKING */
 
-#if LWIP_ARP
 err_t tcpip_input(struct pbuf *p, struct netif *inp);
-#endif /* LWIP_ARP */
 
 #if LWIP_NETIF_API
 err_t tcpip_netifapi(struct netifapi_msg *netifapimsg);
@@ -81,9 +79,7 @@ err_t tcpip_timeout(u32_t msecs, sys_timeout_handler h, void *arg);
 
 enum tcpip_msg_type {
   TCPIP_MSG_API,
-#if LWIP_ARP
   TCPIP_MSG_INPKT,
-#endif /* LWIP_ARP */
 #if LWIP_NETIF_API
   TCPIP_MSG_NETIFAPI,
 #endif /* LWIP_NETIF_API */
@@ -99,12 +95,10 @@ struct tcpip_msg {
 #if LWIP_NETIF_API
     struct netifapi_msg *netifapimsg;
 #endif /* LWIP_NETIF_API */
-#if LWIP_ARP
     struct {
       struct pbuf *p;
       struct netif *netif;
     } inp;
-#endif /* LWIP_ARP */
     struct {
       void (*f)(void *ctx);
       void *ctx;
diff --git a/src/include/lwip/udp.h b/src/include/lwip/udp.h
index 04b4e757..afc152da 100644
--- a/src/include/lwip/udp.h
+++ b/src/include/lwip/udp.h
@@ -32,7 +32,9 @@
 #ifndef __LWIP_UDP_H__
 #define __LWIP_UDP_H__
 
-#include "lwip/arch.h"
+#include "lwip/opt.h"
+
+#if LWIP_UDP /* don't build if not configured for use in lwipopts.h */
 
 #include "lwip/pbuf.h"
 #include "lwip/inet.h"
@@ -135,4 +137,6 @@ void udp_debug_print(struct udp_hdr *udphdr);
 }
 #endif
 
+#endif /* LWIP_UDP */
+
 #endif /* __LWIP_UDP_H__ */
diff --git a/src/include/netif/etharp.h b/src/include/netif/etharp.h
index 0080e2bd..dfe44019 100644
--- a/src/include/netif/etharp.h
+++ b/src/include/netif/etharp.h
@@ -36,6 +36,9 @@
 #define __NETIF_ETHARP_H__
 
 #include "lwip/opt.h"
+
+#if LWIP_ARP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/pbuf.h"
 #include "lwip/ip_addr.h"
 #include "lwip/netif.h"
@@ -136,7 +139,7 @@ struct etharp_q_entry {
   struct etharp_q_entry *next;
   struct pbuf *p;
 };
-#endif
+#endif /* ARP_QUEUEING */
 
 void etharp_init(void);
 void etharp_tmr(void);
@@ -165,4 +168,6 @@ extern const struct eth_addr ethbroadcast, ethzero;
 }
 #endif
 
+#endif /* LWIP_ARP */
+
 #endif /* __NETIF_ARP_H__ */
diff --git a/src/netif/etharp.c b/src/netif/etharp.c
index 90a75ab8..f611c3ea 100644
--- a/src/netif/etharp.c
+++ b/src/netif/etharp.c
@@ -43,22 +43,19 @@
  * This file is part of the lwIP TCP/IP stack.
  *
  */
-#include <string.h>
+ 
 #include "lwip/opt.h"
+
+#if LWIP_ARP /* don't build if not configured for use in lwipopts.h */
+
 #include "lwip/inet.h"
-#include "netif/etharp.h"
 #include "lwip/ip.h"
 #include "lwip/stats.h"
 #include "lwip/snmp.h"
-
-/* ARP needs to inform DHCP of any ARP replies? */
-#if (LWIP_DHCP && DHCP_DOES_ARP_CHECK)
-#  include "lwip/dhcp.h"
-#endif /* LWIP_DHCP && DHCP_DOES_ARP_CHECK */
-/* ARP needs to inform AUTOIP of any ARP replies? */
-#if (LWIP_AUTOIP)
-#  include "lwip/autoip.h"
-#endif /* LWIP_AUTOIP */
+#include "lwip/dhcp.h"
+#include "lwip/autoip.h"
+#include "netif/etharp.h"
+#include <string.h>
 
 /** the time an ARP entry stays valid after its last update,
  *  for ARP_TMR_INTERVAL = 5000, this is
@@ -1086,3 +1083,5 @@ etharp_request(struct netif *netif, struct ip_addr *ipaddr)
                     (struct eth_addr *)netif->hwaddr, &netif->ip_addr, &ethzero,
                     ipaddr, ARP_REQUEST);
 }
+
+#endif /* LWIP_ARP */