ompi/request: correctly handle zero count in ompi_request_default_wait_{all,any,some}

(cherry picked from commit open-mpi/ompi@91e1200)

Author: ggouaillardet

ompi/request/req_wait.c

@@ -16,6 +16,8 @@
  * Copyright (c) 2016      Los Alamos National Security, LLC. All rights
  *                         reserved.
  * Copyright (c) 2016      Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016      Research Organization for Information Science
+ *                         and Technology (RIST). All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -89,6 +91,11 @@ int ompi_request_default_wait_any(size_t count,
     ompi_request_t *request=NULL;
     ompi_wait_sync_t sync;
 
+    if (OPAL_UNLIKELY(0 == count)) {
+        *index = MPI_UNDEFINED;
+        return OMPI_SUCCESS;
+    }
+
     WAIT_SYNC_INIT(&sync, 1);
 
     num_requests_null_inactive = 0;
@@ -192,6 +199,10 @@ int ompi_request_default_wait_all( size_t count,
     int mpi_error = OMPI_SUCCESS;
     ompi_wait_sync_t sync;
 
+    if (OPAL_UNLIKELY(0 == count)) {
+        return OMPI_SUCCESS;
+    }
+
     WAIT_SYNC_INIT(&sync, count);
     rptr = requests;
     for (i = 0; i < count; i++) {
@@ -361,6 +372,11 @@ int ompi_request_default_wait_some(size_t count,
     ompi_wait_sync_t sync;
     size_t sync_sets = 0, sync_unsets = 0;
 
+    if (OPAL_UNLIKELY(0 == count)) {
+        *outcount = MPI_UNDEFINED;
+        return OMPI_SUCCESS;
+    }
+
     WAIT_SYNC_INIT(&sync, 1);
 
     *outcount = 0;