Re: [PATCH 1/2] qemu/queue.h: clear linked list pointers on remove

[Stefan Hajnoczi]

On Mon, Feb 24, 2020 at 12:51:54PM +0100, Philippe Mathieu-Daudé wrote:
> On 2/24/20 11:34 AM, Stefan Hajnoczi wrote:
> > @@ -304,8 +310,10 @@ struct {                                               
> >                  \
> >   } while (/*CONSTCOND*/0)
> >   #define QSIMPLEQ_REMOVE_HEAD(head, field) do {                          \
> > -    if (((head)->sqh_first = (head)->sqh_first->field.sqe_next) == NULL)\
> > +    typeof((head)->sqh_first) elm = (head)->sqh_first;                  \
> > +    if (((head)->sqh_first = elm->field.sqe_next) == NULL)              \
> >           (head)->sqh_last = &(head)->sqh_first;                          \
> 
> Here you check elm for NULL ...
> 
> > +    elm->field.sqe_next = NULL;                                         \
> 
> ... then you assign it.

The sqe_next field is copied into the head.  If this was the last
element in the list then the head's sqh_last needs to be fixed up.

Finally we clear the linked list sqe_next pointer inside the element
itself (which is no longer in the list).

Is there an issue?

Stefan

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