cppcheck does not expand macro when checking C code?

Question

I have code like below, and I use cppcheck to do static analysis. I found that it cannot report null pointer for data.

#define MY_FREE(p) if(p) {free(p);(p)=NULL;}

for(i=0; i<10; i++)
{
    ret = list_insert(list, data);
    if (1 != ret)
    {
        MY_FREE(data);
    }

    other_process(data->item);
}

But if I expand macro "MY_FREE" directly, it worked.

for(i=0; i<10; i++)
{
    ret = list_insert(list, data);
    if (1 != ret)
    {
        if(data) {free(data);(data)=NULL;};
    }

    other_process(data->item);
}

Is there any configuration can resolve it?

Answer 1

I am a Cppcheck developer. What is the exact code your testing? Cppcheck warns about this code:

#define MY_FREE(p) if(p) {free(p);(p)=NULL;}

void f() {
    struct Data *data;
    for(i=0; i<10; i++)
    {
        ret = list_insert(list, data);
        if (1 != ret)
        {
             MY_FREE(data);
        }
        other_process(data->item);
    }
}

Reported warning:

[1.c:12]: (warning) Possible null pointer dereference: data

In your code.. it sounds like that we have false negatives for some reason.