By default the LwIP standard debug prints are disabled to save memory and re-use the same for other parts of application threads. But in-case, you need to enable the standard debug prints in LwIP stack, which is done by LWIP_DEBUGF, you need to follow the steps mentioned below.
lwipopts for WICED SDK can be found in 43xxx_Wi-Fi/WICED/network/LwIP/WWD/FreeRTOS/lwipopts.h. If you are on a DEBUG build (specified by -debug in the make target), WICED_LWIP_DEBUG macro will be enabled, but the prints are still disabled by default.
A standard snip example is considered to demonstrate the how-to operation for a DEBUG build.
2. Switch the LWIP_DBG_TYPES_ON to LWIP_DBG_ON
3. To enable specific debug messages in LWIP, just set the specific define value for the *_DEBUG value to " LWIP_DBG_ON". A comprehensive list of debug defines that can be enabled usually found in the 43xxx_Wi-Fi/WICED/network/LwIP/ver2.0.3/src/include/lwip/opt.h file. You need to copy the defines for the debug messages you want to enable into the lwipopts.h file and enable them there. As an example, I have switched the following on in my lwipopts.h file
#define TCP_DEBUG LWIP_DBG_ON
#define ETHARP_DEBUG LWIP_DBG_ON
#define PBUF_DEBUG LWIP_DBG_ON
#define IP_DEBUG LWIP_DBG_ON
#define TCPIP_DEBUG LWIP_DBG_ON
#define DHCP_DEBUG LWIP_DBG_ON
#define UDP_DEBUG LWIP_DBG_ON
Attached is the modified lwipopts.h file and and the uart terminal print. Please note that enabling debug prints can add extra size (approximately 20 kB for the mentioned settings) to the code. It will also slow down performance of the LwIP code due to required run-time checks and output. It's is recommended to enable debug support only if there is no chance of attaching an external debugger to the target platform and step through the code.