gdbsupport/intrusive-list: add owning_intrusive_list

It occured to me that `intrusive_list<solib>`, as returned by
`solib_ops::current_sos`, for instance, is not very safe.  The
current_sos method returns the ownership of the solib objects
(heap-allocated) to its caller, but the `intrusive_list<solib>` type
does not convey it.  If a function is building an
`intrusive_list<solib>` and something throws, the solibs won't
automatically be deleted.  Introduce owning_intrusive_list to fill this
gap.

Interface
---------

The interface of owning_intrusive_list is mostly equivalent to
intrusive_list, with the following differences:

 - When destroyed, owning_intrusive_list deletes all element objects.
   The clear method does so as well.

 - The erase method destroys the removed object.

 - The push_front, push_back and insert methods accept a `unique_ptr<T>`
   (compared to `T &` for intrusive_list), taking ownership of the
   object.

 - owning_intrusive_list has emplace_front, emplace_back and emplace
   methods, allowing to allocate and construct an object directly in the
   list.  This is really just a shorthand over std::make_unique and
   insert (or push_back / push_front if you don't care about the return
   value), but I think it is nicer to read:

     list.emplace (pos, "hello", 2);

   rather than

     list.insert (pos, std::make_unique<Foo> ("hello", 2));

   These methods are not `noexcept`, since the allocation or the
   constructor could throw.

 - owning_intrusive_list has a release method, allowing to remove an
   element without destroying it.  The release method returns a
   pair-like struct with an iterator to the next element in the list
   (like the erase method) and a unique pointer transferring the
   ownership of the released element to the caller.

 - owning_intrusive_list does not have a clear_and_dispose method, since
   that is typically used to manually free items.

Implementation
--------------

owning_intrusive_list privately inherits from intrusive_list, in order
to re-use the linked list machinery.  It adds ownership semantics around
it.

Testing
-------

Because of the subtle differences in the behavior in behavior and what
we want to test for each type of intrusive list, I didn't see how to
share the tests for the two implementations.  I chose to copy the
intrusive_list tests and adjust them for owning_intrusive_list.

The verify_items function was made common though, and it tries to
dereference the items in the list, to make sure they have not been
deleted by mistake (which would be caught by Valgrind / ASan).

Change-Id: Idbde09c1417b79992a0a9534d6907433e706f760
Co-Authored-By: Pedro Alves <pedro@palves.net>
Reviewed-by: Keith Seitz <keiths@redhat.com>

diff --git a/gdb/unittests/intrusive_list-selftests.c b/gdb/unittests/intrusive_list-selftests.c
index 0c09a64627d9debbbf93f6142bd46d7aa5595706..fbd89ed8c91a4e0ac5a3d4ed5a076ae5127e04b6 100644 (file)
--- a/gdb/unittests/intrusive_list-selftests.c
+++ b/gdb/unittests/intrusive_list-selftests.c
@@ -18,9 +18,15 @@
 
 
 #include "gdbsupport/intrusive_list.h"
+#include "gdbsupport/owning_intrusive_list.h"
 #include "gdbsupport/selftest.h"
 #include <unordered_set>
 
+/* Count of how many item_with_base or item_with_member objects are
+   currently alive.  */
+
+static int items_alive = 0;
+
 /* An item type using intrusive_list_node by inheriting from it and its
    corresponding list type.  Put another base before intrusive_list_node
    so that a pointer to the node != a pointer to the item.  */
@@ -35,7 +41,13 @@ struct item_with_base : public other_base,
 {
   explicit item_with_base (const char *name)
     : name (name)
-  {}
+  {
+    ++items_alive;
+  }
+
+  DISABLE_COPY_AND_ASSIGN (item_with_base);
+
+  ~item_with_base () { --items_alive; }
 
   const char *const name;
 };
@@ -50,64 +62,78 @@ struct item_with_member
 {
   explicit item_with_member (const char *name)
     : name (name)
-  {}
+  {
+    ++items_alive;
+  }
+
+  DISABLE_COPY_AND_ASSIGN (item_with_member);
+
+  ~item_with_member () { --items_alive; }
 
   const char *const name;
   intrusive_list_node<item_with_member> node;
 };
 
-using item_with_member_node
-  = intrusive_member_node<item_with_member, &item_with_member::node>;
-using item_with_member_list
-  = intrusive_list<item_with_member, item_with_member_node>;
+/* Verify that LIST contains exactly the items in EXPECTED.
 
-/* To run all tests using both the base and member methods, all tests are
-   declared in this templated class, which is instantiated once for each
-   list type.  */
+   Traverse the list forward and backwards to exercise all links.  */
 
 template <typename ListType>
-struct intrusive_list_test
+static void
+verify_items (const ListType &list,
+             gdb::array_view<const typename ListType::value_type *> expected)
 {
   using item_type = typename ListType::value_type;
 
-  /* Verify that LIST contains exactly the items in EXPECTED.
+  int i = 0;
 
-     Traverse the list forward and backwards to exercise all links.  */
+  for (typename ListType::iterator it = list.begin (); it != list.end (); ++it)
+    {
+      const item_type &item = *it;
 
-  static void
-  verify_items (const ListType &list,
-               gdb::array_view<const typename ListType::value_type *> expected)
-  {
-    int i = 0;
+      SELF_CHECK (i < expected.size ());
+      SELF_CHECK (&item == expected[i]);
 
-    for (typename ListType::iterator it = list.begin ();
-        it != list.end ();
-        ++it)
-      {
-       const item_type &item = *it;
+      /* Access the item, to make sure the object is still alive.  */
+      SELF_CHECK (strcmp (item.name, expected[i]->name) == 0);
+
+      ++i;
+    }
 
-       SELF_CHECK (i < expected.size ());
-       SELF_CHECK (&item == expected[i]);
+  SELF_CHECK (i == expected.size ());
 
-       ++i;
-      }
+  for (typename ListType::reverse_iterator it = list.rbegin ();
+       it != list.rend (); ++it)
+    {
+      const item_type &item = *it;
 
-    SELF_CHECK (i == expected.size ());
+      --i;
 
-    for (typename ListType::reverse_iterator it = list.rbegin ();
-        it != list.rend ();
-        ++it)
-      {
-       const item_type &item = *it;
+      SELF_CHECK (i >= 0);
+      SELF_CHECK (&item == expected[i]);
+
+      /* Access the item, to make sure the object is still alive.  */
+      SELF_CHECK (strcmp (item.name, expected[i]->name) == 0);
+    }
 
-       --i;
+  SELF_CHECK (i == 0);
+}
 
-       SELF_CHECK (i >= 0);
-       SELF_CHECK (&item == expected[i]);
-      }
+/* intrusive_list tests
 
-    SELF_CHECK (i == 0);
-  }
+   To run all tests using both the base and member methods, all tests are
+   declared in this templated class, which is instantiated once for each
+   list type.  */
+
+using item_with_member_node
+  = intrusive_member_node<item_with_member, &item_with_member::node>;
+using item_with_member_list
+  = intrusive_list<item_with_member, item_with_member_node>;
+
+template <typename ListType>
+struct intrusive_list_test
+{
+  using item_type = typename ListType::value_type;
 
   static void
   test_move_constructor ()
@@ -781,44 +807,851 @@ test_intrusive_list_1 ()
   tests.test_begin_end ();
 }
 
-static void
-test_node_is_linked ()
+/* owning_intrusive_list tests
+
+   To run all tests using both the base and member methods, all tests are
+   declared in this templated class, which is instantiated once for each
+   list type.  */
+
+using item_with_base_owning_list = owning_intrusive_list<item_with_base>;
+using item_with_member_owning_list
+  = owning_intrusive_list<item_with_member, item_with_member_node>;
+
+template<typename ListType>
+struct owning_intrusive_list_test
 {
+  using item_type = typename ListType::value_type;
+
+  static void test_move_constructor ()
   {
-    item_with_base a ("a");
-    item_with_base_list list;
+    {
+      /* Other list is not empty.  */
+      ListType list1;
+      std::vector<const item_type *> expected;
 
-    SELF_CHECK (!a.is_linked ());
-    list.push_back (a);
-    SELF_CHECK (a.is_linked ());
-    list.pop_back ();
-    SELF_CHECK (!a.is_linked ());
+      auto &a = list1.emplace_back ("a");
+      auto &b = list1.emplace_back ("b");
+      auto &c = list1.emplace_back ("c");
+
+      SELF_CHECK (items_alive == 3);
+      ListType list2 (std::move (list1));
+      SELF_CHECK (items_alive == 3);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = { &a, &b, &c };
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Other list contains 1 element.  */
+      ListType list1;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+
+      SELF_CHECK (items_alive == 1);
+      ListType list2 (std::move (list1));
+      SELF_CHECK (items_alive == 1);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = { &a };
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Other list is empty.  */
+      ListType list1;
+      std::vector<const item_type *> expected;
+
+      SELF_CHECK (items_alive == 0);
+      ListType list2 (std::move (list1));
+      SELF_CHECK (items_alive == 0);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
   }
 
+  static void test_move_assignment ()
   {
-    item_with_member a ("a");
-    item_with_member_list list;
+    {
+      /* Both lists are not empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
 
-    SELF_CHECK (!a.node.is_linked ());
-    list.push_back (a);
-    SELF_CHECK (a.node.is_linked ());
-    list.pop_back ();
-    SELF_CHECK (!a.node.is_linked ());
+      auto &a = list1.emplace_back ("a");
+      auto &b = list1.emplace_back ("b");
+      auto &c = list1.emplace_back ("c");
+
+      list2.emplace_back ("d");
+      list2.emplace_back ("e");
+
+      SELF_CHECK (items_alive == 5);
+      list2 = std::move (list1);
+      SELF_CHECK (items_alive == 3);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = { &a, &b, &c };
+      verify_items (list2, expected);
+    }
+
+    {
+      /* rhs list is empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      list2.emplace_back ("a");
+      list2.emplace_back ("b");
+      list2.emplace_back ("c");
+
+      SELF_CHECK (items_alive == 3);
+      list2 = std::move (list1);
+      SELF_CHECK (items_alive == 0);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+
+    {
+      /* lhs list is empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+      auto &b = list1.emplace_back ("b");
+      auto &c = list1.emplace_back ("c");
+
+      SELF_CHECK (items_alive == 3);
+      list2 = std::move (list1);
+      SELF_CHECK (items_alive == 3);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = { &a, &b, &c };
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Both lists contain 1 item.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+      list2.emplace_back ("b");
+
+      SELF_CHECK (items_alive == 2);
+      list2 = std::move (list1);
+      SELF_CHECK (items_alive == 1);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = { &a };
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Both lists are empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      SELF_CHECK (items_alive == 0);
+      list2 = std::move (list1);
+      SELF_CHECK (items_alive == 0);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
   }
-}
 
-static void
-test_intrusive_list ()
-{
-  test_intrusive_list_1<item_with_base_list> ();
-  test_intrusive_list_1<item_with_member_list> ();
-  test_node_is_linked ();
-}
+  static void test_swap ()
+  {
+    {
+      /* Two non-empty lists.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+      auto &b = list1.emplace_back ("b");
+      auto &c = list1.emplace_back ("c");
+
+      auto &d = list2.emplace_back ("d");
+      auto &e = list2.emplace_back ("e");
+
+      SELF_CHECK (items_alive == 5);
+      std::swap (list1, list2);
+      SELF_CHECK (items_alive == 5);
+
+      expected = { &d, &e };
+      verify_items (list1, expected);
+
+      expected = { &a, &b, &c };
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Other is empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+      auto &b = list1.emplace_back ("b");
+      auto &c = list1.emplace_back ("c");
+
+      SELF_CHECK (items_alive == 3);
+      std::swap (list1, list2);
+      SELF_CHECK (items_alive == 3);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = { &a, &b, &c };
+      verify_items (list2, expected);
+    }
+
+    {
+      /* *this is empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list2.emplace_back ("a");
+      auto &b = list2.emplace_back ("b");
+      auto &c = list2.emplace_back ("c");
+
+      SELF_CHECK (items_alive == 3);
+      std::swap (list1, list2);
+      SELF_CHECK (items_alive == 3);
+
+      expected = { &a, &b, &c };
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Both lists empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      SELF_CHECK (items_alive == 0);
+      std::swap (list1, list2);
+      SELF_CHECK (items_alive == 0);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Swap one element twice.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+
+      SELF_CHECK (items_alive == 1);
+      std::swap (list1, list2);
+      SELF_CHECK (items_alive == 1);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = { &a };
+      verify_items (list2, expected);
+
+      std::swap (list1, list2);
+      SELF_CHECK (items_alive == 1);
+
+      expected = { &a };
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+  }
+
+  static void test_front_back ()
+  {
+    ListType list;
+    const ListType &clist = list;
+
+    auto &a = list.emplace_back ("a");
+    list.emplace_back ("b");
+    auto &c = list.emplace_back ("c");
+
+    SELF_CHECK (&list.front () == &a);
+    SELF_CHECK (&clist.front () == &a);
+    SELF_CHECK (&list.back () == &c);
+    SELF_CHECK (&clist.back () == &c);
+  }
+
+  static void test_push_front ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    SELF_CHECK (items_alive == 0);
+    list.push_front (std::make_unique<item_type> ("a"));
+    auto &a = list.front ();
+    expected = { &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 1);
+
+    list.push_front (std::make_unique<item_type> ("b"));
+    auto &b = list.front ();
+    expected = { &b, &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 2);
+
+    list.push_front (std::make_unique<item_type> ("c"));
+    auto &c = list.front ();
+    expected = { &c, &b, &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 3);
+  }
+
+  static void test_push_back ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    SELF_CHECK (items_alive == 0);
+    list.push_back (std::make_unique<item_type> ("a"));
+    auto &a = list.back ();
+    expected = { &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 1);
+
+    list.push_back (std::make_unique<item_type> ("b"));
+    auto &b = list.back ();
+    expected = { &a, &b };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 2);
+
+    list.push_back (std::make_unique<item_type> ("c"));
+    auto &c = list.back ();
+    expected = { &a, &b, &c };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 3);
+  }
+
+  static void test_insert ()
+  {
+    std::vector<const item_type *> expected;
+
+    {
+      /* Insert at beginning.  */
+      ListType list;
+
+      auto &a = *list.insert (list.begin (), std::make_unique<item_type> ("a"));
+      expected = { &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 1);
+
+      auto &b = *list.insert (list.begin (), std::make_unique<item_type> ("b"));
+      expected = { &b, &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 2);
+
+      auto &c = *list.insert (list.begin (), std::make_unique<item_type> ("c"));
+      expected = { &c, &b, &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 3);
+    }
+
+    {
+      /* Insert at end.  */
+      ListType list;
+
+      auto &a = *list.insert (list.end (), std::make_unique<item_type> ("a"));
+      expected = { &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 1);
+
+      auto &b = *list.insert (list.end (), std::make_unique<item_type> ("b"));
+      expected = { &a, &b };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 2);
+
+      auto &c = *list.insert (list.end (), std::make_unique<item_type> ("c"));
+      expected = { &a, &b, &c };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 3);
+    }
+
+    {
+      /* Insert in the middle.  */
+      ListType list;
+
+      auto &a = list.emplace_back ("a");
+      auto &b = list.emplace_back ("b");
+
+      SELF_CHECK (items_alive == 2);
+      auto &c = *list.insert (list.iterator_to (b),
+                             std::make_unique<item_type> ("c"));
+      expected = { &a, &c, &b };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 3);
+    }
+
+    {
+      /* Insert in empty list. */
+      ListType list;
+
+      SELF_CHECK (items_alive == 0);
+      auto &a = *list.insert (list.end (), std::make_unique<item_type> ("a"));
+      expected = { &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 1);
+    }
+  }
+
+  static void test_emplace_front ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    SELF_CHECK (items_alive == 0);
+    auto &a = list.emplace_front ("a");
+    expected = { &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 1);
+
+    auto &b = list.emplace_front ("b");
+    expected = { &b, &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 2);
+
+    auto &c = list.emplace_front ("c");
+    expected = { &c, &b, &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 3);
+  }
+
+  static void test_emplace_back ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    SELF_CHECK (items_alive == 0);
+    auto &a = list.emplace_back ("a");
+    expected = { &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 1);
+
+    auto &b = list.emplace_back ("b");
+    expected = { &a, &b };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 2);
+
+    auto &c = list.emplace_back ("c");
+    expected = { &a, &b, &c };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 3);
+  }
+
+  static void test_emplace ()
+  {
+    std::vector<const item_type *> expected;
+
+    {
+      /* Emplace at beginning.  */
+      ListType list;
+
+      auto &a = list.emplace (list.begin (), "a");
+      expected = { &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 1);
+
+      auto &b = list.emplace (list.begin (), "b");
+      expected = { &b, &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 2);
+
+      auto &c = list.emplace (list.begin (), "c");
+      expected = { &c, &b, &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 3);
+    }
+
+    {
+      /* Emplace at end.  */
+      ListType list;
+
+      auto &a = list.emplace (list.end (), "a");
+      expected = { &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 1);
+
+      auto &b = list.emplace (list.end (), "b");
+      expected = { &a, &b };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 2);
+
+      auto &c = list.emplace (list.end (), "c");
+      expected = { &a, &b, &c };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 3);
+    }
+
+    {
+      /* Emplace in the middle.  */
+      ListType list;
+
+      auto &a = list.emplace_back ("a");
+      auto &b = list.emplace_back ("b");
+
+      SELF_CHECK (items_alive == 2);
+      auto &c = list.emplace (list.iterator_to (b), "c");
+      expected = { &a, &c, &b };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 3);
+    }
+
+    {
+      /* Emplace in empty list. */
+      ListType list;
+
+      SELF_CHECK (items_alive == 0);
+      auto &a = list.emplace (list.end (), "a");
+      expected = { &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 1);
+    }
+  }
+
+  static void test_splice ()
+  {
+    {
+      /* Two non-empty lists.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+      auto &b = list1.emplace_back ("b");
+      auto &c = list1.emplace_back ("c");
+
+      auto &d = list2.emplace_back ("d");
+      auto &e = list2.emplace_back ("e");
+
+      SELF_CHECK (items_alive == 5);
+      list1.splice (std::move (list2));
+      SELF_CHECK (items_alive == 5);
+
+      expected = { &a, &b, &c, &d, &e };
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Receiving list empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list2.emplace_back ("a");
+      auto &b = list2.emplace_back ("b");
+      auto &c = list2.emplace_back ("c");
+
+      SELF_CHECK (items_alive == 3);
+      list1.splice (std::move (list2));
+      SELF_CHECK (items_alive == 3);
+
+      expected = { &a, &b, &c };
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Giving list empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      auto &a = list1.emplace_back ("a");
+      auto &b = list1.emplace_back ("b");
+      auto &c = list1.emplace_back ("c");
+
+      SELF_CHECK (items_alive == 3);
+      list1.splice (std::move (list2));
+      SELF_CHECK (items_alive == 3);
+
+      expected = { &a, &b, &c };
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+
+    {
+      /* Both lists empty.  */
+      ListType list1;
+      ListType list2;
+      std::vector<const item_type *> expected;
+
+      SELF_CHECK (items_alive == 0);
+      list1.splice (std::move (list2));
+      SELF_CHECK (items_alive == 0);
+
+      expected = {};
+      verify_items (list1, expected);
+
+      expected = {};
+      verify_items (list2, expected);
+    }
+  }
+
+  static void test_pop_front ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    list.emplace_back ("a");
+    auto &b = list.emplace_back ("b");
+    auto &c = list.emplace_back ("c");
+
+    SELF_CHECK (items_alive == 3);
+    list.pop_front ();
+    expected = { &b, &c };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 2);
+
+    list.pop_front ();
+    expected = { &c };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 1);
+
+    list.pop_front ();
+    expected = {};
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 0);
+  }
+
+  static void test_pop_back ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    auto &a = list.emplace_back ("a");
+    auto &b = list.emplace_back ("b");
+    list.emplace_back ("c");
+
+    SELF_CHECK (items_alive == 3);
+    list.pop_back ();
+    expected = { &a, &b };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 2);
+
+    list.pop_back ();
+    expected = { &a };
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 1);
+
+    list.pop_back ();
+    expected = {};
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 0);
+  }
+
+  static void test_release ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    auto &a = list.emplace_back ("a");
+    auto &b = list.emplace_back ("b");
+    auto &c = list.emplace_back ("c");
+
+    {
+      SELF_CHECK (items_alive == 3);
+      auto [next_it, released] = list.release (list.iterator_to (b));
+      SELF_CHECK (&*next_it == &c);
+      expected = { &a, &c };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 3);
+      released.reset ();
+      SELF_CHECK (items_alive == 2);
+    }
+
+    {
+      auto [next_it, released] = list.release (list.iterator_to (c));
+      SELF_CHECK (next_it == list.end ());
+      expected = { &a };
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 2);
+      released.reset ();
+      SELF_CHECK (items_alive == 1);
+    }
+
+    {
+      auto [next_it, released] = list.release (list.iterator_to (a));
+      SELF_CHECK (next_it == list.end ());
+      expected = {};
+      verify_items (list, expected);
+      SELF_CHECK (items_alive == 1);
+      released.reset ();
+      SELF_CHECK (items_alive == 0);
+    }
+  }
+
+  static void test_clear ()
+  {
+    ListType list;
+    std::vector<const item_type *> expected;
+
+    list.emplace_back ("a");
+    list.emplace_back ("b");
+    list.emplace_back ("c");
+
+    SELF_CHECK (items_alive == 3);
+    list.clear ();
+    expected = {};
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 0);
+
+    /* Verify idempotency.  */
+    list.clear ();
+    expected = {};
+    verify_items (list, expected);
+    SELF_CHECK (items_alive == 0);
+  }
+
+  static void test_empty ()
+  {
+    ListType list;
+
+    SELF_CHECK (list.empty ());
+    auto &a = list.emplace_back ("a");
+    SELF_CHECK (!list.empty ());
+    list.erase (list.iterator_to (a));
+    SELF_CHECK (list.empty ());
+  }
+
+  static void test_begin_end ()
+  {
+    ListType list;
+    const ListType &clist = list;
+
+    auto &a = list.emplace_back ("a");
+    list.emplace_back ("b");
+    auto &c = list.emplace_back ("c");
+
+    SELF_CHECK (&*list.begin () == &a);
+    SELF_CHECK (&*list.cbegin () == &a);
+    SELF_CHECK (&*clist.begin () == &a);
+    SELF_CHECK (&*list.rbegin () == &c);
+    SELF_CHECK (&*list.crbegin () == &c);
+    SELF_CHECK (&*clist.rbegin () == &c);
+
+    /* At least check that they compile.  */
+    list.end ();
+    list.cend ();
+    clist.end ();
+    list.rend ();
+    list.crend ();
+    clist.end ();
+  }
+};
+
+template<typename ListType>
+static void
+test_owning_intrusive_list_1 ()
+{
+  owning_intrusive_list_test<ListType> tests;
+
+  tests.test_move_constructor ();
+  tests.test_move_assignment ();
+  tests.test_swap ();
+  tests.test_front_back ();
+  tests.test_push_front ();
+  tests.test_push_back ();
+  tests.test_insert ();
+  tests.test_emplace_front ();
+  tests.test_emplace_back ();
+  tests.test_emplace ();
+  tests.test_splice ();
+  tests.test_pop_front ();
+  tests.test_pop_back ();
+  tests.test_release ();
+  tests.test_clear ();
+  tests.test_empty ();
+  tests.test_begin_end ();
+}
+
+static void
+test_node_is_linked ()
+{
+  {
+    item_with_base a ("a");
+    item_with_base_list list;
+
+    SELF_CHECK (!a.is_linked ());
+    list.push_back (a);
+    SELF_CHECK (a.is_linked ());
+    list.pop_back ();
+    SELF_CHECK (!a.is_linked ());
+  }
+
+  {
+    item_with_member a ("a");
+    item_with_member_list list;
+
+    SELF_CHECK (!a.node.is_linked ());
+    list.push_back (a);
+    SELF_CHECK (a.node.is_linked ());
+    list.pop_back ();
+    SELF_CHECK (!a.node.is_linked ());
+  }
+}
+
+static void
+test_intrusive_list ()
+{
+  test_intrusive_list_1<item_with_base_list> ();
+  test_intrusive_list_1<item_with_member_list> ();
+  test_owning_intrusive_list_1<item_with_base_owning_list> ();
+  test_owning_intrusive_list_1<item_with_member_owning_list> ();
+  test_node_is_linked ();
+}
+
+void _initialize_intrusive_list_selftests ();
 
-void _initialize_intrusive_list_selftests ();
 void
 _initialize_intrusive_list_selftests ()
 {
-  selftests::register_test
-    ("intrusive_list", test_intrusive_list);
+  selftests::register_test ("intrusive_list", test_intrusive_list);
 }

diff --git a/gdbsupport/intrusive_list.h b/gdbsupport/intrusive_list.h
index bfa06fc5604430753eda5b40740c824dfd876ecf..345fd7d18ad4e88968423ebea18412c43594e7b5 100644 (file)
--- a/gdbsupport/intrusive_list.h
+++ b/gdbsupport/intrusive_list.h
@@ -395,13 +395,13 @@ public:
   void pop_front () noexcept
   {
     gdb_assert (!this->empty ());
-    erase_element (*m_front);
+    unlink_element (*m_front);
   }
 
   void pop_back () noexcept
   {
     gdb_assert (!this->empty ());
-    erase_element (*m_back);
+    unlink_element (*m_back);
   }
 
 private:
@@ -461,7 +461,8 @@ private:
     return this->iterator_to (elem);
   }
 
-  void erase_element (reference elem) noexcept
+protected:
+  void unlink_element (reference elem) noexcept
   {
     intrusive_list_node<T> *elem_node = as_node (&elem);
 
@@ -504,7 +505,7 @@ public:
     iterator ret = i;
     ++ret;
 
-    erase_element (*i);
+    unlink_element (*i);
 
     return ret;
   }

diff --git a/gdbsupport/owning_intrusive_list.h b/gdbsupport/owning_intrusive_list.h
new file mode 100644 (file)
index 0000000..4c72d9b
--- /dev/null
+++ b/gdbsupport/owning_intrusive_list.h
@@ -0,0 +1,168 @@
+/* Owning version of intrusive_list for GDB, the GNU debugger.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_OWNING_INTRUSIVE_LIST_H
+#define GDBSUPPORT_OWNING_INTRUSIVE_LIST_H
+
+#include "intrusive_list.h"
+
+/* An owning version of intrusive_list.  */
+
+template<typename T, typename AsNode = intrusive_base_node<T>>
+class owning_intrusive_list : private intrusive_list<T, AsNode>
+{
+  using base = intrusive_list<T, AsNode>;
+
+public:
+  using value_type = typename base::value_type;
+  using reference = typename base::reference;
+  using iterator = typename base::iterator;
+  using reverse_iterator = typename base::reverse_iterator;
+  using const_iterator = typename base::const_iterator;
+  using unique_pointer = std::unique_ptr<T>;
+
+  using base::iterator_to;
+  using base::front;
+  using base::back;
+  using base::empty;
+  using base::begin;
+  using base::cbegin;
+  using base::end;
+  using base::cend;
+  using base::rbegin;
+  using base::crbegin;
+  using base::rend;
+  using base::crend;
+
+  owning_intrusive_list () noexcept = default;
+
+  owning_intrusive_list (owning_intrusive_list &&other) noexcept
+    : base (std::move (other))
+  {
+  }
+
+  ~owning_intrusive_list ()
+  { this->clear (); }
+
+  owning_intrusive_list &operator= (owning_intrusive_list &&other) noexcept
+  {
+    this->clear ();
+    this->base::operator= (std::move (other));
+    return *this;
+  }
+
+  void swap (owning_intrusive_list &other) noexcept
+  { this->base::swap (other); }
+
+  /* Insert ELEM at the front of the list.
+
+     The list takes ownership of ELEM.  */
+  void push_front (unique_pointer elem) noexcept
+  { this->base::push_front (*elem.release ()); }
+
+  /* Insert ELEM at the back of the list.
+
+     The list takes ownership of ELEM.  */
+  void push_back (unique_pointer elem) noexcept
+  { this->base::push_back (*elem.release ()); }
+
+  /* Insert ELEM before POS in the list.
+
+     The list takes ownership of ELEM.  */
+  iterator insert (const_iterator pos, unique_pointer elem) noexcept
+  { return  this->base::insert (pos, *elem.release ());  }
+
+  void splice (owning_intrusive_list &&other) noexcept
+  { this->base::splice (std::move (other)); }
+
+  /* Remove the element at the front of the list.  The element is destroyed.  */
+  void pop_front () noexcept
+  {
+    unique_pointer holder (&this->front ());
+    this->base::pop_front ();
+  }
+
+  /* Remove the element at the back of the list.  The element is destroyed.  */
+  void pop_back () noexcept
+  {
+    unique_pointer holder (&this->back ());
+    this->base::pop_back ();
+  }
+
+  /* Remove the element pointed by I from the list.  The element
+     pointed by I is destroyed.  */
+  iterator erase (const_iterator i) noexcept
+  {
+    unique_pointer holder (&*i);
+    return this->base::erase (i);
+  }
+
+  /* Remove all elements from the list.  All elements are destroyed.  */
+  void clear () noexcept
+  {
+    while (!this->empty ())
+      this->pop_front ();
+  }
+
+  /* Construct an element in-place at the front of the list.
+
+     Return a reference to the new element.  */
+  template<typename... Args>
+  reference emplace_front (Args &&...args)
+  { return this->emplace (this->begin (), std::forward<Args> (args)...); }
+
+  /* Construct an element in-place at the back of the list.
+
+     Return a reference to the new element.  */
+  template<typename... Args>
+  reference emplace_back (Args &&...args)
+  { return this->emplace (this->end (), std::forward<Args> (args)...); }
+
+  /* Construct an element in-place in the list, before POS.
+
+     Return a reference to the new element.  */
+  template<typename... Args>
+  reference emplace (const_iterator pos, Args &&...args)
+  {
+    return *this->insert (pos,
+                        std::make_unique<T> (std::forward<Args> (args)...));
+  }
+
+  /* Return type for the release method.  */
+  struct release_ret
+  {
+    /* Iterator to the following element in the list.  */
+    iterator next;
+
+    /* The released element.  */
+    unique_pointer released;
+  };
+
+  release_ret release (const_iterator i) noexcept
+  {
+    iterator next = i;
+    ++next;
+    unique_pointer released (&*i);
+
+    this->unlink_element (*i);
+
+    return { next, std::move (released) };
+  }
+};
+
+#endif /* GDBSUPPORT_OWNING_INTRUSIVE_LIST_H */