opal/datatype: correctly handle zero size datatype or zero count

Signed-off-by: Gilles Gouaillardet <[email protected]>

(cherry picked from commit bf0fc4a)

Author: ggouaillardet

opal/datatype/opal_datatype.h

@@ -14,6 +14,8 @@
  *                         reserved.
  * Copyright (c) 2009      Sun Microsystems, Inc.  All rights reserved.
  * Copyright (c) 2009      Oak Ridge National Labs.  All rights reserved.
+ * Copyright (c) 2017      Research Organization for Information Science
+ *                         and Technology (RIST). All rights reserved.
  * $COPYRIGHT$
  *
  * Additional copyrights may follow
@@ -344,6 +346,9 @@ opal_datatype_span( const opal_datatype_t* pData, int64_t count,
 {
     OPAL_PTRDIFF_TYPE extent = (pData->ub - pData->lb);
     OPAL_PTRDIFF_TYPE true_extent = (pData->true_ub - pData->true_lb);
+    if (OPAL_UNLIKELY(0 == pData->size) || (0 == count)) {
+        return 0;
+    }
     *gap = pData->true_lb;
     return true_extent + (count - 1) * extent;
 }