do not catch polymorphic type by value

dune/solvers/iterationsteps/cgstep.hh

@@ -46,6 +46,12 @@ namespace Dune {
                 p_.resize(r_.size());
             }
 
+            template<typename P>
+            void setPreconditioner(P&& preconditioner)
+            {
+                preconditioner_ = wrap_own_share<Preconditioner>(std::forward<P>(preconditioner));
+            }
+
             void check() const override;
             void preprocess() override;
             void iterate() override;

dune/solvers/test/energynormtest.cc

@@ -266,7 +266,7 @@ int main() try
     return 1;
 
   return 0;
-} catch(Dune::Exception e) {
+} catch(const Dune::Exception& e) {
   std::cout << e << std::endl;
   return 1;
 } catch(...) {

dune/solvers/test/sumoperatortest.cc

@@ -188,7 +188,7 @@ bool checkResize() try {
     DUNE_THROW(Exception, "Resize yields unexpected vector size.");
   std::cout << "passed" << std::endl;
   return true;
-} catch(Dune::Exception e) {
+} catch(const Dune::Exception& e) {
   std::cout << " FAILED." << std::endl;
   std::cout << "Exception was: " << e << std::endl;
   return false;