communicator: Refine ompi_comm_set error check

The `ompi_comm_set` function never sets `NULL` to its first argument
`ncomm`.  So `NULL` check is unnecessary in its callers. Furthermore,
`NULL` check may obscure a real return code when an error occurs
if the variable is initialized to a `NULL` value.

Also, `NULL` check is added in the `ompi_comm_set` function to
avoid segmentation fault in an out-of-memory condition.

Signed-off-by: KAWASHIMA Takahiro <t-kawashima@jp.fujitsu.com>

ompi/communicator/comm.c

@@ -158,6 +158,9 @@ int ompi_comm_set_nb ( ompi_communicator_t **ncomm,
 
     /* ompi_comm_allocate */
     newcomm = OBJ_NEW(ompi_communicator_t);
+    if (NULL == newcomm) {
+        return OMPI_ERR_OUT_OF_RESOURCE;
+    }
     newcomm->super.s_info = NULL;
     /* fill in the inscribing hyper-cube dimensions */
     newcomm->c_cube_dim = opal_cube_dim(local_size);
@@ -354,11 +357,6 @@ int ompi_comm_create ( ompi_communicator_t *comm, ompi_group_t *group,
         goto exit;
     }
 
-    if ( NULL == newcomm ) {
-        rc =  MPI_ERR_INTERN;
-        goto exit;
-    }
-
     /* Determine context id. It is identical to f_2_c_handle */
     rc = ompi_comm_nextcid (newcomp, comm, NULL, NULL, NULL, false, mode);
     if ( OMPI_SUCCESS != rc ) {
@@ -580,10 +578,6 @@ int ompi_comm_split( ompi_communicator_t* comm, int color, int key,
                          local_group,       /* local group */
                          remote_group);     /* remote group */
 
-    if ( NULL == newcomp ) {
-        rc =  MPI_ERR_INTERN;
-        goto exit;
-    }
     if ( OMPI_SUCCESS != rc  ) {
         goto exit;
     }
@@ -1004,11 +998,7 @@ int ompi_comm_dup_with_info ( ompi_communicator_t * comm, opal_info_t *info, omp
                           true,                                   /* copy the topo */
                           comm->c_local_group,                    /* local group */
                           remote_group );                         /* remote group */
-    if ( NULL == newcomp ) {
-        rc =  MPI_ERR_INTERN;
-        return rc;
-    }
-    if ( MPI_SUCCESS != rc) {
+    if ( OMPI_SUCCESS != rc) {
         return rc;
     }
 
@@ -1103,7 +1093,7 @@ static int ompi_comm_idup_internal (ompi_communicator_t *comm, ompi_group_t *gro
                             group,                                  /* local group */
                             remote_group,                           /* remote group */
                             subreq);                                /* new subrequest */
-    if (NULL == context->newcomp) {
+    if (OMPI_SUCCESS != rc) {
         ompi_comm_request_return (request);
         return rc;
     }
@@ -1210,11 +1200,7 @@ int ompi_comm_create_group (ompi_communicator_t *comm, ompi_group_t *group, int
                           true,                                   /* copy the topo */
                           group,                                  /* local group */
                           NULL);                                  /* remote group */
-    if ( NULL == newcomp ) {
-        rc =  MPI_ERR_INTERN;
-        return rc;
-    }
-    if ( MPI_SUCCESS != rc) {
+    if ( OMPI_SUCCESS != rc) {
         return rc;
     }
 

ompi/dpm/dpm.c

@@ -467,8 +467,7 @@ int ompi_dpm_connect_accept(ompi_communicator_t *comm, int root,
                          group,                    /* local group */
                          new_group_pointer         /* remote group */
                          );
-    if ( NULL == newcomp ) {
-        rc = OMPI_ERR_OUT_OF_RESOURCE;
+    if (OMPI_SUCCESS != rc) {
         goto exit;
     }
 

ompi/mpi/c/intercomm_create.c

@@ -190,10 +190,6 @@ int MPI_Intercomm_create(MPI_Comm local_comm, int local_leader,
                          new_group_pointer                             /* remote group */
                          );
 
-    if ( NULL == newcomp ) {
-        rc = MPI_ERR_INTERN;
-        goto err_exit;
-    }
     if ( MPI_SUCCESS != rc ) {
         goto err_exit;
     }

ompi/mpi/c/intercomm_merge.c

@@ -109,10 +109,6 @@ int MPI_Intercomm_merge(MPI_Comm intercomm, int high,
                          new_group_pointer,        /* local group */
                          NULL                      /* remote group */
                          );
-    if ( NULL == newcomp ) {
-        rc = MPI_ERR_INTERN;
-        goto exit;
-    }
     if ( MPI_SUCCESS != rc ) {
         goto exit;
     }