False alarm on doublefree

[Dotan Barak]

Hi.

I'm using cppcheck-2.7 and i noticed that there is a false alarm on double free,
i get the following error message:
/home/db/example.c:31:2: error: Memory pointed to by 'ptr' is freed twice. [doubleFree]

On the following piece of code:

#include <stdlib.h>

struct buf_t {
        void *ptr;
};

int alloc_buf(struct buf_t *buf)
{
        buf->ptr = malloc(10);
        if (buf->ptr == NULL)
                return 1;

        return 0;
}

int main()
{
        struct buf_t buf;

        if (alloc_buf(&buf))
                exit(1);

        free(buf.ptr);

        if (alloc_buf(&buf))
                exit(1);

        free(buf.ptr);

        return 0;
}

Maybe it is worth mentioning that for the following piece code there isn't any warning at all (i.e. using the struct causes this false alarm):

#include <stdlib.h>

int alloc_buf(void **buf)
{
        *buf = malloc(10);
        if (*buf == NULL)
                return 1;

        return 0;
}

int main()
{
        void *buf;

        if (alloc_buf(&buf))
                exit(1);

        free(buf);

        if (alloc_buf(&buf))
                exit(1);

        free(buf);

        return 0;
}

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/11008