[lwip-users] double free errors

[Diego Guglielmi]

Hi i'm having some serious trouble developing a modbus server in lwip using raw api, basically i got the server answering the requests, the problem is that seemingly at random i get the following

mem_free: illegal memory: non-linked: double freemem_free: illegal memory: non-linked: double free

The interesting part is that it seems to do so when closing a connection due to an error if im not mistaken
i put a breakpoint where the message is produced and got the following call stack

mem_free (void * rmem) Line: 717    
pbuf_free (struct pbuf * p) Line: 780   
tcp_seg_free (struct tcp_seg * seg) Line: 1631  
tcp_segs_free (struct tcp_seg * seg) Line: 1616 
tcp_pcb_purge (struct tcp_pcb * pcb, struct tcp_pcb * pcb@entry) Line: 2169 
tcp_pcb_purge (struct tcp_pcb * pcb) Line: 2139 
tcp_pcb_remove (struct tcp_pcb ** pcblist, struct tcp_pcb * pcb, struct tcp_pcb * pcb@entry) Line: 2191 
tcp_input (struct pbuf * p, struct pbuf * p@entry, struct netif * inp, struct netif * inp@entry) Line: 448  
ip4_input (struct pbuf * p, struct pbuf * p@entry, struct netif * inp, struct netif * inp@entry) Line: 709  
ethernet_input (struct pbuf * p, struct netif * netif) Line: 186    
ethernetif_input (struct netif * netif) Line: 788   
ethernet_task Line: 247 
main Line: 929

so maybe this is related to lwipopts rather than the app?

the lwipopts file is the following


#define LWIP_NETIF_HOSTNAME        1
#define LWIP_NETIF_API             0
#define LWIP_NETIF_STATUS_CALLBACK 1
#define LWIP_NETIF_LINK_CALLBACK   1

#define LWIP_SOCKET  0
#define LWIP_NETCONN 0

#define SO_REUSE     1
#define LWIP_IGMP    1

//#include <stmlib/rand.h>
//#define LWIP_RAND    rand_value

#define LWIP_STATS         1
#define LWIP_STATS_DISPLAY 1

extern int printf(const char *format, ...);
#define LWIP_PLATFORM_DIAG(x) {printf x;}
#define LWIP_DEBUG

#define LWIP_NOASSERT

#define LWIP_DBG_TYPES_ON               (LWIP_DBG_STATE | LWIP_DBG_ON)
#define ETHARP_DEBUG                    LWIP_DBG_OFF
#define NETIF_DEBUG                     LWIP_DBG_OFF
#define DHCP_DEBUG                      LWIP_DBG_OFF
#define AUTOIP_DEBUG                    LWIP_DBG_OFF
#define IGMP_DEBUG                      LWIP_DBG_OFF
#define IP_DEBUG                        LWIP_DBG_OFF
#define PBUF_DEBUG                      LWIP_DBG_LEVEL_SERIOUS
#define MEM_DEBUG                       LWIP_DBG_LEVEL_SERIOUS
#define SIMPLE_DISCOVERY_DEBUG          LWIP_DBG_LEVEL_SERIOUS

#define TCP_TMR_INTERVAL    10

attached are the application files 
if anyone can provide any lead i would be really grateful since i've been stuck with this for a while and i don't think i know the innards of lwip good enough to track this

modbusBal.h is the one that handles the queued packets

also i know this code isn't really clean and tidy, this is my first lwip app and initially i just want to get it working more or less reliably

best, diego

modbusTcp.h
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modbusBal.h
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modbusTcp.c
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