hwloc: distances: when we fail to insert an intermediate group, don't try to group further above

Otherwise we'll have some NULL objects above, would be annoying.
No need to dig further, the distance matrix is likely buggy.

We still keep the inserted groups at this level (incomplete level)
because removing them is hard.

(cherry picked from commit open-mpi/hwloc@312a971ec9)
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

opal/mca/hwloc/hwloc191/hwloc/src/distances.c

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2010-2014 Inria.  All rights reserved.
+ * Copyright © 2010-2015 Inria.  All rights reserved.
  * Copyright © 2011-2012 Université Bordeaux 1
  * Copyright © 2011 Cisco Systems, Inc.  All rights reserved.
  * See COPYING in top-level directory.
@@ -832,6 +832,7 @@ hwloc__groups_by_distances(struct hwloc_topology *topology,
       hwloc_obj_t *groupobjs = NULL;
       unsigned *groupsizes = NULL;
       float *groupdistances = NULL;
+      unsigned failed = 0;
 
       groupobjs = malloc(sizeof(hwloc_obj_t) * nbgroups);
       groupsizes = malloc(sizeof(unsigned) * nbgroups);
@@ -863,10 +864,17 @@ hwloc__groups_by_distances(struct hwloc_topology *topology,
                                   groupsizes[i], group_obj->cpuset);
           res_obj = hwloc__insert_object_by_cpuset(topology, group_obj,
 						   fromuser ? hwloc_report_user_distance_error : hwloc_report_os_error);
-	  /* res_obj may be different from group_objs if we got groups from XML import before grouping */
+	  /* res_obj may be NULL on failure to insert. */
+	  if (!res_obj)
+	    failed++;
+	  /* or it may be different from groupobjs if we got groups from XML import before grouping */
           groupobjs[i] = res_obj;
       }
 
+      if (failed)
+	/* don't try to group above if we got a NULL group here, just keep this incomplete level */
+	goto inner_free;
+
       /* factorize distances */
       memset(&(groupdistances[0]), 0, sizeof(groupdistances[0]) * nbgroups * nbgroups);
 #undef DISTANCE