Fix a memory leak in AlignedVector.

include/deal.II/base/aligned_vector.h

@@ -848,7 +848,7 @@ namespace internal
 
 
   /**
-   * A class that given a range of memory locations calls either calls
+   * A class that given a range of memory locations either calls
    * the placement-new operator on these memory locations (if
    * `initialize_memory==true`) or just copies the given initializer
    * into this memory location (if `initialize_memory==false`). The
@@ -1199,11 +1199,22 @@ template <class T>
 inline AlignedVector<T> &
 AlignedVector<T>::operator=(const AlignedVector<T> &vec)
 {
+  const size_type new_size = vec.used_elements_end - vec.elements.get();
+
+  // First throw away everything and re-allocate memory but leave that
+  // memory uninitialized for now:
   resize(0);
-  resize_fast(vec.used_elements_end - vec.elements.get());
+  reserve(new_size);
+
+  // Then copy the elements over by using the copy constructor on these
+  // elements:
   internal::AlignedVectorCopyConstruct<T>(vec.elements.get(),
                                           vec.used_elements_end,
                                           elements.get());
+
+  // Finally adjust the pointer to the end of the elements that are used:
+  used_elements_end = elements.get() + new_size;
+
   return *this;
 }
 

tests/base/aligned_vector_memory_02.cc

@@ -0,0 +1,109 @@
+// --------------------------------------------------------------------------------------------
+//
+// Copyright (C) 2021 by the deal.II authors
+//
+// This file is part of the deal.II library.
+//
+// The deal.II library is free software; you can use it, redistribute
+// it, and/or modify it under the terms of the GNU Lesser General
+// Public License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+// The full text of the license can be found in the file LICENSE.md at
+// the top level directory of deal.II.
+//
+// --------------------------------------------------------------------------------------------
+
+
+// Check for a bug in memory management in class Table (which uses
+// AlignedVector) that had crept in at some point.
+
+#include <deal.II/base/logstream.h>
+#include <deal.II/base/table.h>
+
+#include "../tests.h"
+
+
+int object_number     = 0;
+int objects_destroyed = 0;
+
+class C
+{
+public:
+  C()
+  {
+    object_number = ::object_number++;
+    deallog << "default constructor. Object number " << object_number
+            << std::endl;
+  }
+
+  C(const C &c)
+  {
+    object_number = ::object_number++;
+    deallog << "copy constructor from " << c.object_number << ". Object number "
+            << object_number << std::endl;
+  }
+
+  C(const C &&c)
+  {
+    object_number = ::object_number++;
+    deallog << "move constructor from " << c.object_number << ". Object number "
+            << object_number << std::endl;
+  }
+
+  C &
+  operator=(const C &c)
+  {
+    deallog << "copy operator called for " << object_number << " <- "
+            << c.object_number << std::endl;
+    return *this;
+  }
+
+  C &
+  operator=(const C &&c)
+  {
+    deallog << "move operator called for " << object_number << " <- std::move("
+            << c.object_number << ')' << std::endl;
+    return *this;
+  }
+
+
+  ~C()
+  {
+    deallog << "destructor. Object number " << object_number << std::endl;
+    ++objects_destroyed;
+  }
+
+private:
+  unsigned int object_number;
+};
+
+
+
+void
+test()
+{
+  deallog << "---- Creating outer table" << std::endl;
+  Table<1, C> table({1});
+
+  // Copy the object, then destroy the copy again.
+  {
+    deallog << "---- Cloning outer table" << std::endl;
+    Table<1, C> x(table);
+    deallog << "---- Destroying the clone" << std::endl;
+  }
+
+  deallog << "---- Destroying the source table" << std::endl;
+}
+
+
+
+int
+main(int argc, char **argv)
+{
+  initlog();
+
+  test();
+
+  deallog << "Objects created: " << object_number << std::endl;
+  deallog << "Objects destroyed: " << objects_destroyed << std::endl;
+}

tests/base/aligned_vector_memory_02.output

@@ -0,0 +1,13 @@
+
+DEAL::---- Creating outer table
+DEAL::default constructor. Object number 0
+DEAL::---- Cloning outer table
+DEAL::default constructor. Object number 1
+DEAL::destructor. Object number 1
+DEAL::copy constructor from 0. Object number 2
+DEAL::---- Destroying the clone
+DEAL::destructor. Object number 2
+DEAL::---- Destroying the source table
+DEAL::destructor. Object number 0
+DEAL::Objects created: 3
+DEAL::Objects destroyed: 3