Protect against 0-byte allocations in carte_create and cart_sub.

cmr=v1.7.5:reviewer=jsquyres

This commit was SVN r31146.

ompi/mca/topo/base/topo_base_cart_create.c

@@ -1,3 +1,4 @@
+/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
 /*
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
@@ -10,6 +11,8 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2008      Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2014      Los Alamos National Security, LLC. All right
+ *                         reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -127,6 +130,15 @@ int mca_topo_base_cart_create(mca_topo_base_module_t *topo,
         }
     }
 
+    /* Don't do any of the other initialization if we're not supposed
+       to be part of the new communicator (because nnodes has been
+       reset to 0, making things like index[nnodes-1] be junk).
+
+       JMS: This should really be refactored to use
+       comm_create_group(), because ompi_comm_allocate() still
+       complains about 0-byte mallocs in debug builds for 0-member
+       groups. */
+    if (num_procs > 0) {
         /* Copy the proc structure from the previous communicator over to
            the new one.  The topology module is then able to work on this
            copy and rearrange it as it deems fit. */
@@ -140,6 +152,7 @@ int mca_topo_base_cart_create(mca_topo_base_module_t *topo,
                 topo_procs[i] = ompi_group_peer_lookup(old_comm->c_local_group,i);
             }
         }
+    }
 
     /* allocate a new communicator */
     new_comm = ompi_comm_allocate(num_procs, 0);

ompi/mca/topo/base/topo_base_cart_sub.c

@@ -1,3 +1,4 @@
+/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
 /*
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
@@ -10,6 +11,8 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2008      Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2014      Los Alamos National Security, LLC. All rights
+ *                         reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -120,6 +123,9 @@ int mca_topo_base_cart_sub (ompi_communicator_t* comm,
         cart->ndims = ndim;
         cart->dims = dorig;
         cart->periods = porig;
+
+        /* NTH: protect against a 0-byte alloc in the ndims = 0 case */
+        if (ndim > 0) {
             cart->coords = (int*)malloc(sizeof(int) * ndim);
             if (NULL == cart->coords) {
                 free(cart->periods);
@@ -137,11 +143,14 @@ int mca_topo_base_cart_sub (ompi_communicator_t* comm,
                     rank %= nprocs;
                 }
             }
+        }
+
         temp_comm->c_topo           = topo;
         temp_comm->c_topo->mtc.cart = cart;
         temp_comm->c_topo->reorder  = false;
         temp_comm->c_flags         |= OMPI_COMM_CART;
     }
+
     *new_comm = temp_comm;
 
     return MPI_SUCCESS;