Use shared_ptr to store the transfer operators to avoid memory leaks

dune/solvers/test/mmgtest.cc

@@ -83,13 +83,12 @@ void solveObstacleProblemByMMGSolver(const GridType& grid, const MatrixType& mat
 
     // we need a vector of pointers to the transfer operator base class
     using Transfer = TruncatedCompressedMGTransfer<VectorType>;
-    std::vector<Transfer*> transfer(grid.maxLevel());
+    std::vector<std::shared_ptr<Transfer> > transfer(grid.maxLevel());
     for (size_t i = 0; i < transfer.size(); ++i)
     {
         // create transfer operator from level i to i+1
-        Transfer* t = new Transfer;
-        t->setup(grid, i, i+1);
-        transfer[i] = t;
+        transfer[i] = std::make_shared<Transfer>();
+        transfer[i]->setup(grid, i, i+1);
     }
     mmgStep.setTransferOperators(transfer);