From patch #7221: added flag NO_SYS_NO_TIMERS to drop timer support for NO_SYS==1 for easier upgrading

src/include/lwip/memp_std.h

@@ -71,7 +71,9 @@ LWIP_MEMPOOL(ARP_QUEUE,      MEMP_NUM_ARP_QUEUE,       sizeof(struct etharp_q_en
 LWIP_MEMPOOL(IGMP_GROUP,     MEMP_NUM_IGMP_GROUP,      sizeof(struct igmp_group),     "IGMP_GROUP")
 #endif /* LWIP_IGMP */
 
+#if LWIP_TIMERS
 LWIP_MEMPOOL(SYS_TIMEOUT,    MEMP_NUM_SYS_TIMEOUT,     sizeof(struct sys_timeo),      "SYS_TIMEOUT")
+#endif /* LWIP_TIMERS */
 
 #if LWIP_SNMP
 LWIP_MEMPOOL(SNMP_ROOTNODE,  MEMP_NUM_SNMP_ROOTNODE,   sizeof(struct mib_list_rootnode), "SNMP_ROOTNODE")

src/include/lwip/opt.h

@@ -68,6 +68,14 @@
 #define NO_SYS                          0
 #endif
 
+/**
+ * NO_SYS_NO_TIMERS==1: Drop support for sys_timeout when NO_SYS==1
+ * Mainly for compatibility to old versions.
+ */
+#ifndef NO_SYS_NO_TIMERS
+#define NO_SYS_NO_TIMERS                0
+#endif
+
 /**
  * MEMCPY: override this if you have a faster implementation at hand than the
  * one included in your C library

src/include/lwip/timers.h

@@ -35,6 +35,11 @@
 
 #include "lwip/opt.h"
 
+/* Timers are not supported when NO_SYS==1 and NO_SYS_NO_TIMERS==1 */
+#define LWIP_TIMERS (!NO_SYS || (NO_SYS && !NO_SYS_NO_TIMERS))
+
+#if LWIP_TIMERS
+
 #include "lwip/err.h"
 #include "lwip/sys.h"
 
@@ -89,4 +94,5 @@ void sys_timeouts_mbox_fetch(sys_mbox_t *mbox, void **msg);
 }
 #endif
 
+#endif /* LWIP_TIMERS */
 #endif /* __LWIP_TIMERS_H__ */