[PATCH] Fix undefined behavior in ira-build.c

[Jakub Jelinek]

On Fri, Jun 27, 2014 at 11:34:48AM +0200, Richard Biener wrote:
> On Fri, Jun 27, 2014 at 9:16 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> > Hi!
> >
> > This fixes the most common source of the new runtime diagnostics
> > during bootstrap-ubsan, if num is 0, ira_object_id_map is often
> > 0 as well.
> >
> > Ok for trunk/4.9?
> 
> If it's also sometimes 1 then why not if (num > 1) - just as optimization...

Sure, if Vlad is ok with the patch, consider it changed to num > 1.

> > 2014-06-27  Jakub Jelinek  <jakub@redhat.com>
> >
> >         * ira-build.c (sort_conflict_id_map): Don't call
> >         qsort if num is 0, as ira_object_id_map might be NULL.
> >
> > --- gcc/ira-build.c.jj  2014-05-30 10:51:16.000000000 +0200
> > +++ gcc/ira-build.c     2014-06-26 20:21:43.428987181 +0200
> > @@ -2821,8 +2821,9 @@ sort_conflict_id_map (void)
> >        FOR_EACH_ALLOCNO_OBJECT (a, obj, oi)
> >         ira_object_id_map[num++] = obj;
> >      }
> > -  qsort (ira_object_id_map, num, sizeof (ira_object_t),
> > -        object_range_compare_func);
> > +  if (num)
> > +    qsort (ira_object_id_map, num, sizeof (ira_object_t),
> > +          object_range_compare_func);
> >    for (i = 0; i < num; i++)
> >      {
> >        ira_object_t obj = ira_object_id_map[i];
> >
> >         Jakub

	Jakub