ESP8266 Community Forum

- Thu Jan 19, 2017 4:59 pm #61244

GDB should give you a better insight into the compiled code

Thank you
That unblocked my problem.
GDB does not find my symbol, but I can load the adresses from the error message and display the source code intermingled with the diassassembly

Code: Select all(gdb) disass /m 0x000000004026041c,+0x400

for example roughly yields

Code: Select all57          source_ip.addr = pingopt->ip;
   0x4026041e <ping_received+6>:        l32i.n  a2, a2, 0
   0x4026042b <ping_received+19>:       l32i.n  a2, a2, 4
   0x4026042f <ping_received+23>:       addi    a3, a1, 16
   0x40260432 <ping_received+26>:       addmi   a14, a3, 0x400
   0x40260435 <ping_received+29>:       s32i.n  a2, a14, 16

58          ipaddr_ntoa_r(&source_ip, ipaddrstr, sizeof(ipaddrstr));
   0x40260437 <ping_received+31>:       movi    a2, 0x410
   0x4026043a <ping_received+34>:       add.n   a2, a3, a2
   0x4026043c <ping_received+36>:       movi.n  a4, 16


So when the offendig address was `0x4026042b` I can assume line 57 as the culprit - great .

Now I can apply the good old printing debug technique:

Code: Select allvoid ping_received(void *arg, void *data) {
    struct ping_msg *pingmsg = (struct ping_msg*)arg;
    struct ping_option *pingopt = pingmsg->ping_opt;
    struct ping_resp *pingresp = (struct ping_resp*)data;

    c_printf("[wjr] what do we have in ping_recieved? | arg= %X | data= %X | pingmsg= %X | pingopt= %X | pingresp = %X | \n",
         arg, data, pingmsg, pingopt, pingresp);
   
    char ipaddrstr[16];
    ip_addr_t source_ip;
   
    c_printf("[wjr] before accessing pingopt\n");
    source_ip.addr = pingopt->ip;
    c_printf("[wjr] after accessing pingopt\n");


yields

Code: Select all> [wjr] what do we have in ping_recieved? | arg= 3FFF0598 | data= 3FFFFE50 | pingmsg= 3FFF0598 | pingopt= 4 | pingresp = 3FFFFE50 |
[wjr] before accessing pingopt
Fatal exception 28(LoadProhibitedCause):
epc1=0x4026046b, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000008, depc=0x00000000


Bingo!
Looks like we have some data in `pingopt` instead of a pointer.
So either the tutorial was never able to run - maybe because ist was intended to be a debugging tutorial, or the interface has changed.

Anyway, my confidence is growing again