[PATCH 01/32] [libx11] Using freed pointer "e"

[Peter Hutterer]

On Sun, Feb 13, 2011 at 12:00:10AM +0100, Mark Kettenis wrote:
> > Reordered code to first to do the comparison and then to release data
> 
> Your static analysis tool isn't all that good.  Using the value of a
> pointer after freeing the storage it points to is totally fine.

I disagree. It's _technically_ fine, but I'd consider any code actually
doing this as buggy.

quite frankly, in this particular case I'd even be in favour of setting e to
NULL after XFree, just to make sure.

Cheers,
  Peter
 
> > ---
> >  src/XlibInt.c |    4 ++--
> >  1 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/src/XlibInt.c b/src/XlibInt.c
> > index d55c26a..c385f4c 100644
> > --- a/src/XlibInt.c
> > +++ b/src/XlibInt.c
> > @@ -777,10 +777,10 @@ _XFreeEventCookies(Display *dpy)
> >      head = (struct stored_event**)&dpy->cookiejar;
> >  
> >      DL_FOREACH_SAFE(*head, e, tmp) {
> > -        XFree(e->ev.data);
> > -        XFree(e);
> >          if (dpy->cookiejar == e)
> >              dpy->cookiejar = NULL;
> > +        XFree(e->ev.data);
> > +        XFree(e);
> >      }
> >  }