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Altera_Forum
Honored Contributor I
1,202 Views

LwIP issue: "undefined reference".

Hi, I'm working on a project for school that will be using lwIP, and I need to familiarize myself with how it works. For now I'm just trying to write a simple test program. It doesn't even do anything yet, but I cannot for the life of me get it to compile: 

#include "lwip\udp.h" void udp_packet_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port); main(){ // Create a new pcb. struct udp_pcb * pcb; pcb = udp_new(); if (pcb == NULL) return -1; // Bind to any IP on port 60,000. if (udp_bind(pcb, IP_ADDR_ANY, 60000) != ERR_OK) return -2; // On datagram receipt, call udp_packet_recv. udp_recv(pcb, udp_packet_recv, NULL); } void udp_packet_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port){ if (p != NULL){ // TODO: Case handling GET packet. // TODO: Case handling data receipt. pbuf_free(p); // Free pbuf when finished. } } Every time I try to compile this, I get the following errors: 

C:\Users\ZACHAR~1\AppData\Local\Temp\cc1kZ7BP.o:client.c:(.text+0xf): undefined reference to `udp_new()' C:\Users\ZACHAR~1\AppData\Local\Temp\cc1kZ7BP.o:client.c:(.text+0x3d): undefined reference to `udp_bind(udp_pcb*, ip_addr*, unsigned short)' C:\Users\ZACHAR~1\AppData\Local\Temp\cc1kZ7BP.o:client.c:(.text+0x5d): undefined reference to `udp_packet_recv(void*, udp_pcb*, pbuf*, ip_addr*, unsigned short)' C:\Users\ZACHAR~1\AppData\Local\Temp\cc1kZ7BP.o:client.c:(.text+0x69): undefined reference to `udp_recv(udp_pcb*, void (*)(void*, udp_pcb*, pbuf*, ip_addr*, unsigned short), void*)' C:\Users\ZACHAR~1\AppData\Local\Temp\cc1kZ7BP.o:client.c:(.text+0x8e): undefined reference to `pbuf_free(pbuf*)' collect2: ld returned 1 exit status I read something online about linking "lwip4", but have not been able to find anything about that file elsewhere. (I can't even figure out where I originally read that...) 

 

 

 

I'm using "lwip-win32-msvc-0.1", which is based on the CVS version of lwIP from 23-01-2002. 

 

The computer I am attempting to compile on is a Sony VPCF126FM, with no hardware modifications of any kind. 

 

I'm using MiniGW command line " g++ client.c -o client.exe" to compile. (Nothing fancy.) 

Can anybody help me out here? This has become a real sticking point.
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Altera_Forum
Honored Contributor I
77 Views

I managed to find "lwip4.dsp" and "lwip4.dsw" in the "lwip-win32-msvc-0.1\proj\msvc6" directory. I'm not sure these are the right files though, and attempting to link them with the following commands has not worked. 

 

-llwip4.dsp -llwip4.dsw -l lwip4.dsp -l lwip4.dsw -llwip4 -l lwip4 

 

I keep getting some variation of "ld.exe: cannot find -llwip4".