From: Timo Heister <timo.heister@gmail.com>
Date: Mon, 27 Jul 2015 15:36:16 +0000 (-0400)
Subject: avoid dereferencing empty std::vectors
X-Git-Tag: v8.4.0-rc2~706^2~4
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=448b2821fffaa33bd0b2f036dee9f2a42d66a160;p=dealii.git

avoid dereferencing empty std::vectors
---

diff --git a/include/deal.II/lac/parallel_vector.templates.h b/include/deal.II/lac/parallel_vector.templates.h
index 0230a8e926..89b280dfc9 100644
--- a/include/deal.II/lac/parallel_vector.templates.h
+++ b/include/deal.II/lac/parallel_vector.templates.h
@@ -633,19 +633,25 @@ namespace parallel
           // make sure that there are not outstanding requests from updating
           // ghost values or compress
           int flag = 1;
-          int ierr = MPI_Testall (update_ghost_values_requests.size(),
-                                  &update_ghost_values_requests[0],
-                                  &flag, MPI_STATUSES_IGNORE);
-          Assert (ierr == MPI_SUCCESS, ExcInternalError());
-          Assert (flag == 1,
-                  ExcMessage("MPI found unfinished update_ghost_values() requests"
-                             "when calling swap, which is not allowed"));
-          ierr = MPI_Testall (compress_requests.size(), &compress_requests[0],
-                              &flag, MPI_STATUSES_IGNORE);
-          Assert (ierr == MPI_SUCCESS, ExcInternalError());
-          Assert (flag == 1,
-                  ExcMessage("MPI found unfinished compress() requests "
-                             "when calling swap, which is not allowed"));
+          if (update_ghost_values_requests.size()>0)
+            {
+              int ierr = MPI_Testall (update_ghost_values_requests.size(),
+                                      &update_ghost_values_requests[0],
+                                      &flag, MPI_STATUSES_IGNORE);
+              Assert (ierr == MPI_SUCCESS, ExcInternalError());
+              Assert (flag == 1,
+                      ExcMessage("MPI found unfinished update_ghost_values() requests"
+                                 "when calling swap, which is not allowed"));
+            }
+          if (compress_requests.size()>0)
+            {
+              int ierr = MPI_Testall (compress_requests.size(), &compress_requests[0],
+                                      &flag, MPI_STATUSES_IGNORE);
+              Assert (ierr == MPI_SUCCESS, ExcInternalError());
+              Assert (flag == 1,
+                      ExcMessage("MPI found unfinished compress() requests "
+                                 "when calling swap, which is not allowed"));
+            }
         }
 #endif
 
diff --git a/source/base/partitioner.cc b/source/base/partitioner.cc
index 39240e1e4e..1b216a9d4e 100644
--- a/source/base/partitioner.cc
+++ b/source/base/partitioner.cc
@@ -281,8 +281,9 @@ namespace Utilities
           }
         AssertDimension (current_index_start, n_ghost_indices_data);
 
-        MPI_Waitall (import_requests.size(), &import_requests[0],
-                     MPI_STATUSES_IGNORE);
+        if (import_requests.size()>0)
+          MPI_Waitall (import_requests.size(), &import_requests[0],
+                       MPI_STATUSES_IGNORE);
 
         // transform import indices to local index space and compress
         // contiguous indices in form of ranges