Work around a change in PETSc 3.4.

git-svn-id: https://svn.dealii.org/trunk@30916 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/source/lac/petsc_matrix_base.cc b/deal.II/source/lac/petsc_matrix_base.cc
index fb96b311eb4ce3e7b7a6d3dec09dd3e3a4ff7541..81780da99d92e45529d987efede62f95c9e2e87c 100644 (file)
--- a/deal.II/source/lac/petsc_matrix_base.cc
+++ b/deal.II/source/lac/petsc_matrix_base.cc
@@ -358,13 +358,16 @@ namespace PETScWrappers
     ierr = MatGetRow(*this, row, &ncols, &colnums, &values);
     AssertThrow (ierr == 0, MatrixBase::ExcPETScError(ierr));
 
-    // then restore the matrix and return the
-    // number of columns in this row as
-    // queried previously
+    // then restore the matrix and return the number of columns in this row as
+    // queried previously. Starting with PETSc 3.4, MatRestoreRow actually
+    // resets the last three arguments to zero/NULL, to avoid abuse of pointers
+    // now dangling. as a consequence, we need to save the size of the array
+    // and return the saved value.
+    const PetscInt ncols_saved = ncols;
     ierr = MatRestoreRow(*this, row, &ncols, &colnums, &values);
     AssertThrow (ierr == 0, MatrixBase::ExcPETScError(ierr));
 
-    return ncols;
+    return ncols_saved;
   }