cppcheck 2.6 : wrong assumption of "assigned value is never 0"

[fenugrec]

Hi,
I'm having what appears to be a false positive, compiling this section, where it goes through two elements of a linked-list :

    msg = msg->next;
    if (msg == NULL) {
        return CMD_OK;
    }

    msg = msg->next;
    if (msg == NULL) {
        return CMD_OK;
    }

(complete file: https://github.com/fenugrec/freediag/blob/master/scantool/scantool_850.c#L1240 )

cppcheck complains about that :

---

scantool/scantool_850.c:1241:10: style: Condition 'msg==NULL' is always false [knownConditionTrueFalse]
if (msg == NULL) {
^
scantool/scantool_850.c:1233:10: note: Assuming that condition 'msg==NULL' is not redundant
if (msg == NULL) {
^
scantool/scantool_850.c:1232:6: note: msg is assigned 'msg->next' here.
msg = msg->next;
^
scantool/scantool_850.c:1233:10: note: Assuming condition is false
if (msg == NULL) {
^
scantool/scantool_850.c:1240:11: note: Assignment 'msg=msg->next', assigned value is never 0
msg = msg->next;
^
scantool/scantool_850.c:1241:10: note: Condition 'msg==NULL' is always false
if (msg == NULL) {

---

Of course the issue is "msg->next" means something different the second time, and can be 0, but cppcheck fails to recognize this ?

[Daniel Marjamäki]

Thanks! I can reproduce. I have created https://trac.cppcheck.net/ticket/10649

[fenugrec]

Wow that was fast. Thanks a lot for your work on cppcheck, it's very useful even with occasional issues like this one.