On Thu, Aug 2, 2012 at 1:58 PM, Pete Batard <p...@akeo.ie> wrote:
>
> > Setting next and prev to NULL in list_del() caused a crash in
> > usbi_cond_destroy() in threads_windows.c (next was used after calling
> > list_del). Using list_for_each_entry_safe fixed it and cleaned up the
> code.
> >
> > int usbi_cond_destroy(usbi_cond_t *cond) {
> > // This assumes no one is using this anymore. The check MAY NOT BE
> > safe.
> > struct usbi_cond_perthread *pos, *next_pos = NULL;
> > if(!cond) return ((errno=EINVAL));
> > if(!list_empty(&cond->waiters)) return ((errno=EBUSY )); // (!see
> > above!)
> > list_for_each_entry_safe(pos, next_pos, &cond->not_waiting, list,
> > struct usbi_cond_perthread) {
> > CloseHandle(pos->event);
> > list_del(&pos->list);
> > free(pos);
> > }
> >
> > return 0;
> > }
>
>
> Interesting. Do you know in which call next was being used?
> Still, if we apply the nulling of prev/next, we're likely to get reports
> from Windows users with the same issue, that we can address then.
>
list_for_each_entry() uses next as it steps through the list.
list_for_each_entry_safe() avoids the problem by getting and saving the
next pointer in a temporary before the loop body.
Orin.
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