do not catch polymorphic types by value

This addresses several warnings from GCC 8 of the form

    ../dune/istl/test/matrixredisttest.cc:102:10: warning:
    catching polymorphic type ‘class Dune::ISTLError’ by value [-Wcatch-value=]

dune/istl/matrixredistribute.hh

@@ -578,7 +578,7 @@ namespace Dune
             cont.sparsity[column].insert(i);
         }
       }
-      catch(Dune::RangeError er) {
+      catch(const Dune::RangeError&) {
         // Entry not present in the new index set. Ignore!
 #ifdef DEBUG_REPART
         typedef typename Container::LookupIndexSet GlobalLookup;
@@ -593,7 +593,7 @@ namespace Dune
           MPI_Comm_rank(MPI_COMM_WORLD,&rank);
           std::cout<<rank<<cont.aggidxset<<std::endl;
           std::cout<<rank<<": row "<<i<<" (global="<<gi <<") not in index set for owner index "<<pi->global()<<std::endl;
-          throw er;
+          throw;
         }
 #endif
       }
@@ -657,7 +657,7 @@ namespace Dune
           cont.matrix[i][column]=data.second;
         }
       }
-      catch(Dune::RangeError er) {
+      catch(const Dune::RangeError&) {
         // This an overlap row and might therefore lack some entries!
       }
 
@@ -752,7 +752,7 @@ namespace Dune
       {
         try{
           newMatrix[col.index()][row.index()];
-        }catch(Dune::ISTLError e) {
+        }catch(const Dune::ISTLError&) {
           std::cerr<<newComm.communicator().rank()<<": entry ("
                    <<col.index()<<","<<row.index()<<") missing! for symmetry!"<<std::endl;
           ret=1;

dune/istl/test/bcrsassigntest.cc

@@ -6,41 +6,35 @@ using namespace Dune;
 
 int main (int argc, char** argv)
 {
-    try
-    {
-        typedef BCRSMatrix<FieldMatrix<double,2,2> >  Mat;
+  typedef BCRSMatrix<FieldMatrix<double,2,2> >  Mat;
 
-        Mat A(1,1, Mat::random);
+  Mat A(1,1, Mat::random);
 
-        A.setrowsize(0,1);
+  A.setrowsize(0,1);
 
-        A.endrowsizes();
+  A.endrowsizes();
 
-        A.addindex(0, 0);
+  A.addindex(0, 0);
 
-        A.endindices();
-        A = 0;
+  A.endindices();
+  A = 0;
 
-        Mat B(2,2, Mat::random);
+  Mat B(2,2, Mat::random);
 
-        B.setrowsize(0,2);
-        B.setrowsize(1,1);
+  B.setrowsize(0,2);
+  B.setrowsize(1,1);
 
-        B.endrowsizes();
+  B.endrowsizes();
 
-        B.addindex(0, 0);
-        B.addindex(0, 1);
+  B.addindex(0, 0);
+  B.addindex(0, 1);
 
-        B.addindex(1, 1);
+  B.addindex(1, 1);
 
-        B.endindices();
-        B = 0;
+  B.endindices();
+  B = 0;
 
-        B  = A;
+  B = A;
 
-    } catch(Exception e){
-        std::cout<<e<<std::endl;
-        return 1;
-    }
-    return 0;
+  return 0;
 }

dune/istl/test/bcrsbuild.cc

@@ -157,20 +157,15 @@ void testDoubleSetSize()
 
 int main()
 {
-  try{
-    Dune::TestSuite testSuite;
+  Dune::TestSuite testSuite;
 
-    Builder<Dune::BCRSMatrix<Dune::FieldMatrix<double,1,1> > > builder;
+  Builder<Dune::BCRSMatrix<Dune::FieldMatrix<double,1,1> > > builder;
 
-    testSuite.subTest(builder.randomBuild(5,4));
-    testSuite.subTest(builder.rowWiseBuild(5,4,13));
-    testSuite.subTest(builder.rowWiseBuild(5,4));
+  testSuite.subTest(builder.randomBuild(5,4));
+  testSuite.subTest(builder.rowWiseBuild(5,4,13));
+  testSuite.subTest(builder.rowWiseBuild(5,4));
 
-    testDoubleSetSize();
+  testDoubleSetSize();
 
-    return testSuite.exit();
-  }catch(Dune::Exception e) {
-    std::cerr << e<<std::endl;
-    return 1;
-  }
+  return testSuite.exit();
 }

dune/istl/test/matrixredisttest.cc

@@ -99,7 +99,7 @@ int testRepart(int N, int coarsenTarget)
       if(col.index()<=row.index())
         try{
           newMat[col.index()][row.index()];
-        }catch(Dune::ISTLError e) {
+        }catch(const Dune::ISTLError&) {
           std::cerr<<coarseComm->communicator().rank()<<": entry ("
                    <<col.index()<<","<<row.index()<<") missing!"<<std::endl;
           ret=1;