diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 853224023fd..a629dcdd84b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-01-20  Ulrich Drepper  <drepper@redhat.com>
+
+	Fix after C++ P0600 implementation.
+	* g++.dg/init/new39.C: Don't just ignore result of new.
+
 2019-01-20  Iain Buclaw  <ibuclaw@gdcproject.org>
 
 	* gdc.dg/runnable.d: Add more tests for comparing complex types.
diff --git a/gcc/testsuite/g++.dg/init/new39.C b/gcc/testsuite/g++.dg/init/new39.C
index f274ebb7b9d..430701db684 100644
--- a/gcc/testsuite/g++.dg/init/new39.C
+++ b/gcc/testsuite/g++.dg/init/new39.C
@@ -57,7 +57,7 @@ int
 main ()
 {
   try {
-    ::operator new(size_t(-1));
+    (void) ::operator new(size_t(-1));
     abort ();
   } catch (std::bad_alloc &) {
   }
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 4ca096d7b75..cb7f1a61af7 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,92 @@
+2019-01-20  Ulrich Drepper  <drepper@redhat.com>
+
+	Implement C++20 P0600r1.
+	* include/backward/hash_map: Add nodiscard attribute to empty.
+	* include/backward/hash_set: Likewise.
+	* backward/hashtable.h: Likewise.
+	* include/bits/basic_string.h: Likewise.
+	* include/bits/forward_list.h: Likewise.
+	* include/bits/hashtable.h: Likewise.
+	* include/bits/regex.h: Likewise.
+	* include/bits/stl_deque.h: Likewise.
+	* include/bits/stl_list.h: Likewise.
+	* include/bits/stl_map.h: Likewise.
+	* include/bits/stl_multimap.h: Likewise.
+	* include/bits/stl_multiset.h: Likewise.
+	* include/bits/stl_queue.h: Likewise.
+	* include/bits/stl_set.h: Likewise.
+	* include/bits/stl_stack.h: Likewise.
+	* include/bits/stl_tree.h: Likewise.
+	* include/bits/stl_vector.h: Likewise.
+	* include/bits/unordered_map.h: Likewise.
+	* include/bits/unordered_set.h: Likewise.
+	* include/debug/array: Likewise.
+	* include/experimental/any: Likewise.
+	* include/experimental/bits/fs_path.h: Likewise.
+	* include/experimental/internet: Likewise.
+	* include/experimental/string_view: Likewise.
+	* include/ext/pb_ds/detail/bin_search_tree_/info_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/binary_heap_/binary_heap_.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/binary_heap_/info_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/cc_hash_table_map_/cc_ht_map_.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/cc_hash_table_map_/info_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/cc_hash_table_map_/size_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/gp_hash_table_map_/gp_ht_map_.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/gp_hash_table_map_/info_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/left_child_next_sibling_heap_/
+	info_fn_imps.hpp: Likewise.
+	* include/ext/pb_ds/detail/left_child_next_sibling_heap_/
+	left_child_next_sibling_heap_.hpp: Likewise.
+	* include/ext/pb_ds/detail/list_update_map_/info_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/list_update_map_/lu_map_.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/ov_tree_map_/info_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/ov_tree_map_/ov_tree_map_.hp:
+	Likewise.
+	* include/ext/pb_ds/detail/pat_trie_/info_fn_imps.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/pat_trie_/pat_trie_.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/rc_binomial_heap_/rc.hpp:
+	Likewise.
+	* include/ext/pb_ds/detail/tree_trace_base.hpp: Likewise.
+	* include/ext/pb_ds/trie_policy.hpp: Likewise.
+	* include/ext/rope: Likewise.
+	* include/ext/slist: Likewise.
+	* include/ext/vstring.h: Likewise.
+	* include/profile/array: Likewise.
+	* include/std/array: Likewise.
+	* include/tr1/array: Likewise.
+	* include/tr1/hashtable.h: Likewise.
+	* include/tr1/regex: Likewise.
+	* include/tr2/dynamic_bitset: Likewise.
+	* include/bits/alloc_traits.h: Add nodiscard attribute to
+	allocate.
+	* include/experimental/memory_resource: Likewise.
+	* include/ext/alloc_traits.h: Likewise.
+	* include/ext/array_allocator.h: Likewise.
+	* include/ext/bitmap_allocator.h: Likewise.
+	* include/ext/debug_allocator.h: Likewise.
+	* include/ext/extptr_allocator.h: Likewise.
+	* include/ext/mt_allocator.h: Likewise.
+	* include/ext/new_allocator.h: Likewise.
+	* include/ext/pool_allocator.h: Likewise.
+	* include/ext/throw_allocator.h: Likewise.
+	* include/std/scoped_allocator: Likewise.
+	* libsupc++/eh_alloc.cc: Likewise.
+	* include/std/future: Add nodiscard attribute to async.
+	* libsupc++/new: Add nodiscard attribute to new.
+
 2019-01-18  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/87514
diff --git a/libstdc++-v3/include/backward/hash_map b/libstdc++-v3/include/backward/hash_map
index 9f47970767d..66a5218fc6f 100644
--- a/libstdc++-v3/include/backward/hash_map
+++ b/libstdc++-v3/include/backward/hash_map
@@ -166,7 +166,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       max_size() const
       { return _M_ht.max_size(); }
       
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return _M_ht.empty(); }
   
@@ -385,7 +385,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       max_size() const
       { return _M_ht.max_size(); }
 
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return _M_ht.empty(); }
 
diff --git a/libstdc++-v3/include/backward/hash_set b/libstdc++-v3/include/backward/hash_set
index 2515cd1dafa..2dc0ed774fa 100644
--- a/libstdc++-v3/include/backward/hash_set
+++ b/libstdc++-v3/include/backward/hash_set
@@ -168,7 +168,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       max_size() const
       { return _M_ht.max_size(); }
       
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return _M_ht.empty(); }
       
@@ -369,7 +369,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       max_size() const
       { return _M_ht.max_size(); }
 
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return _M_ht.empty(); }
 
diff --git a/libstdc++-v3/include/backward/hashtable.h b/libstdc++-v3/include/backward/hashtable.h
index a8cf149873b..28c487a71c2 100644
--- a/libstdc++-v3/include/backward/hashtable.h
+++ b/libstdc++-v3/include/backward/hashtable.h
@@ -379,7 +379,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       max_size() const
       { return size_type(-1); }
 
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return size() == 0; }
 
diff --git a/libstdc++-v3/include/bits/alloc_traits.h b/libstdc++-v3/include/bits/alloc_traits.h
index cea28e04500..ed61ce845f8 100644
--- a/libstdc++-v3/include/bits/alloc_traits.h
+++ b/libstdc++-v3/include/bits/alloc_traits.h
@@ -301,7 +301,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        *
        *  Calls @c a.allocate(n)
       */
-      static pointer
+      _GLIBCXX_NODISCARD static pointer
       allocate(_Alloc& __a, size_type __n)
       { return __a.allocate(__n); }
 
@@ -316,7 +316,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        *  Returns <tt> a.allocate(n, hint) </tt> if that expression is
        *  well-formed, otherwise returns @c a.allocate(n)
       */
-      static pointer
+      _GLIBCXX_NODISCARD static pointer
       allocate(_Alloc& __a, size_type __n, const_void_pointer __hint)
       { return _S_allocate(__a, __n, __hint, 0); }
 
@@ -439,7 +439,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        *
        *  Calls @c a.allocate(n)
       */
-      static pointer
+      _GLIBCXX_NODISCARD static pointer
       allocate(allocator_type& __a, size_type __n)
       { return __a.allocate(__n); }
 
@@ -453,7 +453,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        *
        *  Returns <tt> a.allocate(n, hint) </tt>
       */
-      static pointer
+      _GLIBCXX_NODISCARD static pointer
       allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
       { return __a.allocate(__n, __hint); }
 
diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index 28ed337bdb6..0a6dd3cbc71 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -1027,7 +1027,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns true if the %string is empty.  Equivalent to 
        *  <code>*this == ""</code>.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return this->size() == 0; }
 
@@ -4007,7 +4007,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
        *  Returns true if the %string is empty.  Equivalent to 
        *  <code>*this == ""</code>.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return this->size() == 0; }
 
diff --git a/libstdc++-v3/include/bits/forward_list.h b/libstdc++-v3/include/bits/forward_list.h
index 4741c43376c..4c277845a51 100644
--- a/libstdc++-v3/include/bits/forward_list.h
+++ b/libstdc++-v3/include/bits/forward_list.h
@@ -774,7 +774,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
        *  Returns true if the %forward_list is empty.  (Thus begin() would
        *  equal end().)
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return this->_M_impl._M_head._M_next == nullptr; }
 
diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h
index 34946c75b0b..31794fb12c2 100644
--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -533,7 +533,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       size() const noexcept
       { return _M_element_count; }
 
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return size() == 0; }
 
diff --git a/libstdc++-v3/include/bits/regex.h b/libstdc++-v3/include/bits/regex.h
index 79645948af2..7576cd7a9c0 100644
--- a/libstdc++-v3/include/bits/regex.h
+++ b/libstdc++-v3/include/bits/regex.h
@@ -1705,7 +1705,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        * @retval true The %match_results object is empty.
        * @retval false The %match_results object is not empty.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return size() == 0; }
 
diff --git a/libstdc++-v3/include/bits/stl_deque.h b/libstdc++-v3/include/bits/stl_deque.h
index 341682c03a5..1574895a2c6 100644
--- a/libstdc++-v3/include/bits/stl_deque.h
+++ b/libstdc++-v3/include/bits/stl_deque.h
@@ -1377,7 +1377,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
        *  Returns true if the %deque is empty.  (Thus begin() would
        *  equal end().)
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return this->_M_impl._M_finish == this->_M_impl._M_start; }
 
diff --git a/libstdc++-v3/include/bits/stl_list.h b/libstdc++-v3/include/bits/stl_list.h
index 14a7881d0f5..68bab94af1e 100644
--- a/libstdc++-v3/include/bits/stl_list.h
+++ b/libstdc++-v3/include/bits/stl_list.h
@@ -1047,7 +1047,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
        *  Returns true if the %list is empty.  (Thus begin() would equal
        *  end().)
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return this->_M_impl._M_node._M_next == &this->_M_impl._M_node; }
 
diff --git a/libstdc++-v3/include/bits/stl_map.h b/libstdc++-v3/include/bits/stl_map.h
index c2c974a2003..a61d23cac68 100644
--- a/libstdc++-v3/include/bits/stl_map.h
+++ b/libstdc++-v3/include/bits/stl_map.h
@@ -459,7 +459,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       /** Returns true if the %map is empty.  (Thus begin() would equal
        *  end().)
       */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return _M_t.empty(); }
 
diff --git a/libstdc++-v3/include/bits/stl_multimap.h b/libstdc++-v3/include/bits/stl_multimap.h
index 98796fd2878..29a96d8a45b 100644
--- a/libstdc++-v3/include/bits/stl_multimap.h
+++ b/libstdc++-v3/include/bits/stl_multimap.h
@@ -452,7 +452,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
       // capacity
       /** Returns true if the %multimap is empty.  */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return _M_t.empty(); }
 
diff --git a/libstdc++-v3/include/bits/stl_multiset.h b/libstdc++-v3/include/bits/stl_multiset.h
index 175e0755543..7a0fb832480 100644
--- a/libstdc++-v3/include/bits/stl_multiset.h
+++ b/libstdc++-v3/include/bits/stl_multiset.h
@@ -406,7 +406,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #endif
 
       ///  Returns true if the %set is empty.
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return _M_t.empty(); }
 
diff --git a/libstdc++-v3/include/bits/stl_queue.h b/libstdc++-v3/include/bits/stl_queue.h
index 575cbf9bed8..aa8dd02ed6e 100644
--- a/libstdc++-v3/include/bits/stl_queue.h
+++ b/libstdc++-v3/include/bits/stl_queue.h
@@ -185,7 +185,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       /**
        *  Returns true if the %queue is empty.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return c.empty(); }
 
@@ -563,7 +563,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       /**
        *  Returns true if the %queue is empty.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return c.empty(); }
 
diff --git a/libstdc++-v3/include/bits/stl_set.h b/libstdc++-v3/include/bits/stl_set.h
index 7779007c2e2..7c903cf3a9a 100644
--- a/libstdc++-v3/include/bits/stl_set.h
+++ b/libstdc++-v3/include/bits/stl_set.h
@@ -410,7 +410,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #endif
 
       ///  Returns true if the %set is empty.
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return _M_t.empty(); }
 
diff --git a/libstdc++-v3/include/bits/stl_stack.h b/libstdc++-v3/include/bits/stl_stack.h
index 88650c15ba6..8581dce210c 100644
--- a/libstdc++-v3/include/bits/stl_stack.h
+++ b/libstdc++-v3/include/bits/stl_stack.h
@@ -181,7 +181,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       /**
        *  Returns true if the %stack is empty.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return c.empty(); }
 
diff --git a/libstdc++-v3/include/bits/stl_tree.h b/libstdc++-v3/include/bits/stl_tree.h
index 252ef959fcc..47ae0ae9531 100644
--- a/libstdc++-v3/include/bits/stl_tree.h
+++ b/libstdc++-v3/include/bits/stl_tree.h
@@ -1027,7 +1027,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       rend() const _GLIBCXX_NOEXCEPT
       { return const_reverse_iterator(begin()); }
 
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return _M_impl._M_node_count == 0; }
 
diff --git a/libstdc++-v3/include/bits/stl_vector.h b/libstdc++-v3/include/bits/stl_vector.h
index ebf105aa8fa..54de0e09ce7 100644
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -964,7 +964,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
        *  Returns true if the %vector is empty.  (Thus begin() would
        *  equal end().)
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return begin() == end(); }
 
diff --git a/libstdc++-v3/include/bits/unordered_map.h b/libstdc++-v3/include/bits/unordered_map.h
index 4b71db5d10a..ecb3ef411fc 100644
--- a/libstdc++-v3/include/bits/unordered_map.h
+++ b/libstdc++-v3/include/bits/unordered_map.h
@@ -300,7 +300,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       // size and capacity:
 
       ///  Returns true if the %unordered_map is empty.
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return _M_h.empty(); }
 
@@ -1441,7 +1441,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       // size and capacity:
 
       ///  Returns true if the %unordered_multimap is empty.
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return _M_h.empty(); }
 
diff --git a/libstdc++-v3/include/bits/unordered_set.h b/libstdc++-v3/include/bits/unordered_set.h
index e1ac398e363..3e1180f323a 100644
--- a/libstdc++-v3/include/bits/unordered_set.h
+++ b/libstdc++-v3/include/bits/unordered_set.h
@@ -294,7 +294,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       // size and capacity:
 
       ///  Returns true if the %unordered_set is empty.
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return _M_h.empty(); }
 
@@ -1102,7 +1102,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       // size and capacity:
 
       ///  Returns true if the %unordered_multiset is empty.
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return _M_h.empty(); }
 
diff --git a/libstdc++-v3/include/debug/array b/libstdc++-v3/include/debug/array
index 0ca2fcae937..9e94e656c04 100644
--- a/libstdc++-v3/include/debug/array
+++ b/libstdc++-v3/include/debug/array
@@ -71,7 +71,7 @@ namespace __debug
       template<std::size_t _Size>
 	struct _Array_check_nonempty
  	{
-	  bool empty() { return _Size == 0; }
+	  _GLIBCXX_NODISCARD bool empty() { return _Size == 0; }
 
 	  _Array_check_nonempty()
 	  { __glibcxx_check_nonempty(); }
@@ -145,7 +145,7 @@ namespace __debug
       constexpr size_type
       max_size() const noexcept { return _Nm; }
 
-      constexpr bool
+      _GLIBCXX_NODISCARD constexpr bool
       empty() const noexcept { return size() == 0; }
 
       // Element access.
diff --git a/libstdc++-v3/include/experimental/any b/libstdc++-v3/include/experimental/any
index f8cd4a78821..ed7a115f6b2 100644
--- a/libstdc++-v3/include/experimental/any
+++ b/libstdc++-v3/include/experimental/any
@@ -266,7 +266,7 @@ inline namespace fundamentals_v1
     // observers
 
     /// Reports whether there is a contained object or not.
-    bool empty() const noexcept { return _M_manager == nullptr; }
+    _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; }
 
 #if __cpp_rtti
     /// The @c typeid of the contained object, or @c typeid(void) if empty.
diff --git a/libstdc++-v3/include/experimental/bits/fs_path.h b/libstdc++-v3/include/experimental/bits/fs_path.h
index e9d6619876a..239776df313 100644
--- a/libstdc++-v3/include/experimental/bits/fs_path.h
+++ b/libstdc++-v3/include/experimental/bits/fs_path.h
@@ -365,7 +365,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
 
     // query
 
-    bool empty() const noexcept { return _M_pathname.empty(); }
+    _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_pathname.empty(); }
     bool has_root_name() const;
     bool has_root_directory() const;
     bool has_root_path() const;
diff --git a/libstdc++-v3/include/experimental/internet b/libstdc++-v3/include/experimental/internet
index 07c62e697cd..80682efed53 100644
--- a/libstdc++-v3/include/experimental/internet
+++ b/libstdc++-v3/include/experimental/internet
@@ -1049,7 +1049,7 @@ namespace ip
 
     iterator begin() const noexcept { return _M_begin; }
     iterator end() const noexcept { return _M_end; }
-    bool empty() const noexcept { return _M_begin == _M_end; }
+    _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_begin == _M_end; }
 
     size_t
     size() const noexcept { return _M_end->to_uint() - _M_begin->to_uint(); }
@@ -1093,7 +1093,7 @@ namespace ip
 
     iterator begin() const noexcept { return _M_begin; }
     iterator end() const noexcept { return _M_end; }
-    bool empty() const noexcept { return _M_begin == _M_end; }
+    _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_begin == _M_end; }
 
     iterator
     find(const address_v6& __addr) const noexcept
@@ -1721,7 +1721,7 @@ namespace ip
       // size:
       size_type size() const noexcept { return _M_size; }
       size_type max_size() const noexcept { return _M_results.max_size(); }
-      bool empty() const noexcept { return _M_results.empty(); }
+      _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_results.empty(); }
 
       // element access:
       const_iterator begin() const { return _M_results.begin(); }
diff --git a/libstdc++-v3/include/experimental/memory_resource b/libstdc++-v3/include/experimental/memory_resource
index 4d96466f218..e9fece55cd0 100644
--- a/libstdc++-v3/include/experimental/memory_resource
+++ b/libstdc++-v3/include/experimental/memory_resource
@@ -88,7 +88,7 @@ namespace pmr {
 
     memory_resource& operator=(const memory_resource&) = default;
 
-    void*
+    _GLIBCXX_NODISCARD void*
     allocate(size_t __bytes, size_t __alignment = _S_max_align)
     { return do_allocate(__bytes, __alignment); }
 
@@ -145,7 +145,7 @@ namespace pmr {
       polymorphic_allocator&
 	operator=(const polymorphic_allocator& __rhs) = default;
 
-      _Tp* allocate(size_t __n)
+      _GLIBCXX_NODISCARD _Tp* allocate(size_t __n)
       { return static_cast<_Tp*>(_M_resource->allocate(__n * sizeof(_Tp),
 						       alignof(_Tp))); }
 
diff --git a/libstdc++-v3/include/experimental/string_view b/libstdc++-v3/include/experimental/string_view
index d233ecc743b..8cc0e90246b 100644
--- a/libstdc++-v3/include/experimental/string_view
+++ b/libstdc++-v3/include/experimental/string_view
@@ -169,7 +169,7 @@ inline namespace fundamentals_v1
 		/ sizeof(value_type) / 4;
       }
 
-      constexpr bool
+      _GLIBCXX_NODISCARD constexpr bool
       empty() const noexcept
       { return this->_M_len == 0; }
 
diff --git a/libstdc++-v3/include/ext/alloc_traits.h b/libstdc++-v3/include/ext/alloc_traits.h
index 5571d2692fb..65fa3de271c 100644
--- a/libstdc++-v3/include/ext/alloc_traits.h
+++ b/libstdc++-v3/include/ext/alloc_traits.h
@@ -128,7 +128,7 @@ template<typename _Alloc, typename = typename _Alloc::value_type>
     typedef typename _Alloc::size_type              size_type;
     typedef typename _Alloc::difference_type        difference_type;
 
-    static pointer
+    _GLIBCXX_NODISCARD static pointer
     allocate(_Alloc& __a, size_type __n)
     { return __a.allocate(__n); }
 
diff --git a/libstdc++-v3/include/ext/array_allocator.h b/libstdc++-v3/include/ext/array_allocator.h
index 6dd23cdbb82..c0d4a3497dc 100644
--- a/libstdc++-v3/include/ext/array_allocator.h
+++ b/libstdc++-v3/include/ext/array_allocator.h
@@ -151,7 +151,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       ~array_allocator() _GLIBCXX_USE_NOEXCEPT { }
 
-      pointer
+      _GLIBCXX_NODISCARD pointer
       allocate(size_type __n, const void* = 0)
       {
 	if (_M_array == 0 || _M_used + __n > _M_array->size())
diff --git a/libstdc++-v3/include/ext/bitmap_allocator.h b/libstdc++-v3/include/ext/bitmap_allocator.h
index 400030bfbc5..532bad295b6 100644
--- a/libstdc++-v3/include/ext/bitmap_allocator.h
+++ b/libstdc++-v3/include/ext/bitmap_allocator.h
@@ -90,7 +90,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	_M_space_left() const throw()
 	{ return _M_end_of_storage - _M_finish; }
 
-	pointer
+	_GLIBCXX_NODISCARD pointer
 	allocate(size_type __n)
 	{ return static_cast<pointer>(::operator new(__n * sizeof(_Tp))); }
 
@@ -1009,7 +1009,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       ~bitmap_allocator() _GLIBCXX_USE_NOEXCEPT
       { }
 
-      pointer 
+      _GLIBCXX_NODISCARD pointer 
       allocate(size_type __n)
       {
 	if (__n > this->max_size())
@@ -1033,7 +1033,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  }
       }
 
-      pointer 
+      _GLIBCXX_NODISCARD pointer 
       allocate(size_type __n, typename bitmap_allocator<void>::const_pointer)
       { return allocate(__n); }
 
diff --git a/libstdc++-v3/include/ext/debug_allocator.h b/libstdc++-v3/include/ext/debug_allocator.h
index bf86470e8fc..c5fc57e68dd 100644
--- a/libstdc++-v3/include/ext/debug_allocator.h
+++ b/libstdc++-v3/include/ext/debug_allocator.h
@@ -118,7 +118,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       debug_allocator(const _Alloc& __a)
       : _M_allocator(__a), _M_extra(_S_extra()) { }
 
-      pointer
+      _GLIBCXX_NODISCARD pointer
       allocate(size_type __n)
       {
         pointer __res = _M_allocator.allocate(__n + _M_extra);      
@@ -127,7 +127,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
         return __res + _M_extra;
       }
 
-      pointer
+      _GLIBCXX_NODISCARD pointer
       allocate(size_type __n, const void* __hint)
       {
         pointer __res = _M_allocator.allocate(__n + _M_extra, __hint);
diff --git a/libstdc++-v3/include/ext/extptr_allocator.h b/libstdc++-v3/include/ext/extptr_allocator.h
index 388edb2e622..2ce87b60c44 100644
--- a/libstdc++-v3/include/ext/extptr_allocator.h
+++ b/libstdc++-v3/include/ext/extptr_allocator.h
@@ -92,7 +92,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       const_pointer address(const_reference __x) const _GLIBCXX_NOEXCEPT
       { return std::__addressof(__x); }
 
-      pointer allocate(size_type __n, void* __hint = 0)
+      _GLIBCXX_NODISCARD pointer allocate(size_type __n, void* __hint = 0)
       { return _M_real_alloc.allocate(__n,__hint); }
 
       void deallocate(pointer __p, size_type __n)
diff --git a/libstdc++-v3/include/ext/mt_allocator.h b/libstdc++-v3/include/ext/mt_allocator.h
index 7b07533f3df..43e84f47fbd 100644
--- a/libstdc++-v3/include/ext/mt_allocator.h
+++ b/libstdc++-v3/include/ext/mt_allocator.h
@@ -665,7 +665,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       ~__mt_alloc() _GLIBCXX_USE_NOEXCEPT { }
 
-      pointer
+      _GLIBCXX_NODISCARD pointer
       allocate(size_type __n, const void* = 0);
 
       void
@@ -684,7 +684,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     };
 
   template<typename _Tp, typename _Poolp>
-    typename __mt_alloc<_Tp, _Poolp>::pointer
+    _GLIBCXX_NODISCARD typename __mt_alloc<_Tp, _Poolp>::pointer
     __mt_alloc<_Tp, _Poolp>::
     allocate(size_type __n, const void*)
     {
diff --git a/libstdc++-v3/include/ext/new_allocator.h b/libstdc++-v3/include/ext/new_allocator.h
index 04db4bbc99f..e24539100f9 100644
--- a/libstdc++-v3/include/ext/new_allocator.h
+++ b/libstdc++-v3/include/ext/new_allocator.h
@@ -98,7 +98,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       // NB: __n is permitted to be 0.  The C++ standard says nothing
       // about what the return value is when __n == 0.
-      pointer
+      _GLIBCXX_NODISCARD pointer
       allocate(size_type __n, const void* = static_cast<const void*>(0))
       {
 	if (__n > this->max_size())
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/info_fn_imps.hpp
index 5e739551c52..4019f864307 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/bin_search_tree_/info_fn_imps.hpp
@@ -39,6 +39,7 @@
  */
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/binary_heap_.hpp b/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/binary_heap_.hpp
index 40ddeed5aad..dbfd612917e 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/binary_heap_.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/binary_heap_.hpp
@@ -144,7 +144,7 @@ namespace __gnu_pbds
 
       ~binary_heap();
 
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       inline size_type
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/info_fn_imps.hpp
index 29612faf13e..d81d5500659 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/binary_heap_/info_fn_imps.hpp
@@ -39,6 +39,7 @@
  */
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/cc_ht_map_.hpp b/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/cc_ht_map_.hpp
index 6706c1aab6e..1a6affc70b2 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/cc_ht_map_.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/cc_ht_map_.hpp
@@ -271,7 +271,7 @@ namespace __gnu_pbds
       max_size() const;
 
       /// True if size() == 0.
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       /// Return current hash_fn.
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/info_fn_imps.hpp
index 7b5318b64ec..9d38890f7f6 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/info_fn_imps.hpp
@@ -52,6 +52,7 @@ max_size() const
 { return m_entry_allocator.max_size(); }
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/size_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/size_fn_imps.hpp
index 500b92f0be0..bcc1fc47b12 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/size_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/cc_hash_table_map_/size_fn_imps.hpp
@@ -46,6 +46,7 @@ size() const
 { return m_num_used_e; }
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/gp_ht_map_.hpp b/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/gp_ht_map_.hpp
index bcac913597d..90dfd50ef8e 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/gp_ht_map_.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/gp_ht_map_.hpp
@@ -279,7 +279,7 @@ namespace __gnu_pbds
       max_size() const;
 
       /// True if size() == 0.
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       /// Return current hash_fn.
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/info_fn_imps.hpp
index 64fa975e601..464216e45dd 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/gp_hash_table_map_/info_fn_imps.hpp
@@ -52,6 +52,7 @@ max_size() const
 { return s_entry_allocator.max_size(); }
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/info_fn_imps.hpp
index 8d31e5b711d..d12710a1218 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/info_fn_imps.hpp
@@ -39,6 +39,7 @@
  */
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/left_child_next_sibling_heap_.hpp b/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/left_child_next_sibling_heap_.hpp
index 746a3d8a39a..32d67eb3d3a 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/left_child_next_sibling_heap_.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/left_child_next_sibling_heap_/left_child_next_sibling_heap_.hpp
@@ -144,7 +144,7 @@ namespace __gnu_pbds
 
       ~left_child_next_sibling_heap();
 
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       inline size_type
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/info_fn_imps.hpp
index 2c44a513c82..5d2e81ff4a7 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/info_fn_imps.hpp
@@ -51,6 +51,7 @@ max_size() const
 { return s_entry_allocator.max_size(); }
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/lu_map_.hpp b/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/lu_map_.hpp
index e3539a57516..a3c0fb49c9a 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/lu_map_.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/list_update_map_/lu_map_.hpp
@@ -198,7 +198,7 @@ namespace __gnu_pbds
       inline size_type
       max_size() const;
 
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       inline mapped_reference
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/info_fn_imps.hpp
index 26f33bf5444..81e7305e315 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/info_fn_imps.hpp
@@ -54,6 +54,7 @@ max_size() const
 { return s_value_alloc.max_size(); }
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/ov_tree_map_.hpp b/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/ov_tree_map_.hpp
index efebc354cd6..0859da17d7a 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/ov_tree_map_.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/ov_tree_map_/ov_tree_map_.hpp
@@ -239,7 +239,7 @@ namespace __gnu_pbds
       inline size_type
       max_size() const;
 
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       inline size_type
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/info_fn_imps.hpp b/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/info_fn_imps.hpp
index 0f6eaf5c44a..33fc3e14ccf 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/info_fn_imps.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/info_fn_imps.hpp
@@ -39,6 +39,7 @@
  */
 
 PB_DS_CLASS_T_DEC
+_GLIBCXX_NODISCARD
 inline bool
 PB_DS_CLASS_C_DEC::
 empty() const
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/pat_trie_.hpp b/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/pat_trie_.hpp
index 13da3d4264a..3f7e054e249 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/pat_trie_.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/pat_trie_/pat_trie_.hpp
@@ -223,7 +223,7 @@ namespace __gnu_pbds
 	    }
 	}
 
-	inline bool
+	_GLIBCXX_NODISCARD inline bool
 	empty() const
 	{ return m_bag.empty(); }
       };
@@ -279,7 +279,7 @@ namespace __gnu_pbds
 
       ~PB_DS_PAT_TRIE_NAME();
 
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       inline size_type
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/rc_binomial_heap_/rc.hpp b/libstdc++-v3/include/ext/pb_ds/detail/rc_binomial_heap_/rc.hpp
index 2d1b4e795a3..5c996d11e28 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/rc_binomial_heap_/rc.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/rc_binomial_heap_/rc.hpp
@@ -87,7 +87,7 @@ namespace __gnu_pbds
       inline void
       pop();
 
-      inline bool
+      _GLIBCXX_NODISCARD inline bool
       empty() const;
 
       inline size_type
@@ -178,7 +178,7 @@ namespace __gnu_pbds
     }
 
     template<typename _Node, typename _Alloc>
-    inline bool
+    _GLIBCXX_NODISCARD inline bool
     rc<_Node, _Alloc>::
     empty() const
     {
diff --git a/libstdc++-v3/include/ext/pb_ds/detail/tree_trace_base.hpp b/libstdc++-v3/include/ext/pb_ds/detail/tree_trace_base.hpp
index 980ff9788a2..3b349c70d35 100644
--- a/libstdc++-v3/include/ext/pb_ds/detail/tree_trace_base.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/detail/tree_trace_base.hpp
@@ -80,7 +80,7 @@ namespace __gnu_pbds
       void
       trace_node(node_const_iterator, size_type) const;
 
-      virtual bool
+      _GLIBCXX_NODISCARD virtual bool
       empty() const = 0;
 
       virtual node_const_iterator
diff --git a/libstdc++-v3/include/ext/pb_ds/trie_policy.hpp b/libstdc++-v3/include/ext/pb_ds/trie_policy.hpp
index 0b0683dec51..9c750aa56b3 100644
--- a/libstdc++-v3/include/ext/pb_ds/trie_policy.hpp
+++ b/libstdc++-v3/include/ext/pb_ds/trie_policy.hpp
@@ -315,7 +315,7 @@ namespace __gnu_pbds
     typedef typename __rebind_ma::reference 		metadata_reference;
 
     /// Returns true if the container is empty.
-    virtual bool
+    _GLIBCXX_NODISCARD virtual bool
     empty() const = 0;
 
     /// Returns the iterator associated with the trie's first element.
diff --git a/libstdc++-v3/include/ext/pool_allocator.h b/libstdc++-v3/include/ext/pool_allocator.h
index 460f55dbbf0..4b23727abae 100644
--- a/libstdc++-v3/include/ext/pool_allocator.h
+++ b/libstdc++-v3/include/ext/pool_allocator.h
@@ -188,7 +188,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       destroy(pointer __p) { __p->~_Tp(); }
 #endif
 
-      pointer
+      _GLIBCXX_NODISCARD pointer
       allocate(size_type __n, const void* = 0);
 
       void
@@ -210,7 +210,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     __pool_alloc<_Tp>::_S_force_new;
 
   template<typename _Tp>
-    _Tp*
+    _GLIBCXX_NODISCARD _Tp*
     __pool_alloc<_Tp>::allocate(size_type __n, const void*)
     {
       pointer __ret = 0;
diff --git a/libstdc++-v3/include/ext/rope b/libstdc++-v3/include/ext/rope
index 4cc8285a671..127d113c349 100644
--- a/libstdc++-v3/include/ext/rope
+++ b/libstdc++-v3/include/ext/rope
@@ -1797,7 +1797,7 @@ protected:
       static int _S_compare(const _RopeRep* __x, const _RopeRep* __y);
       
     public:
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return 0 == this->_M_tree_ptr; }
       
diff --git a/libstdc++-v3/include/ext/slist b/libstdc++-v3/include/ext/slist
index 532235f8c53..3b49ae20183 100644
--- a/libstdc++-v3/include/ext/slist
+++ b/libstdc++-v3/include/ext/slist
@@ -458,7 +458,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       max_size() const
       { return size_type(-1); }
 
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return this->_M_head._M_next == 0; }
 
diff --git a/libstdc++-v3/include/ext/throw_allocator.h b/libstdc++-v3/include/ext/throw_allocator.h
index 52d58e6ffc6..38e80f721da 100644
--- a/libstdc++-v3/include/ext/throw_allocator.h
+++ b/libstdc++-v3/include/ext/throw_allocator.h
@@ -829,7 +829,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       address(const_reference __x) const _GLIBCXX_NOEXCEPT
       { return std::__addressof(__x); }
 
-      pointer
+      _GLIBCXX_NODISCARD pointer
       allocate(size_type __n, std::allocator<void>::const_pointer hint = 0)
       {
 	if (__n > this->max_size())
diff --git a/libstdc++-v3/include/ext/vstring.h b/libstdc++-v3/include/ext/vstring.h
index ddffebf0893..5942218531f 100644
--- a/libstdc++-v3/include/ext/vstring.h
+++ b/libstdc++-v3/include/ext/vstring.h
@@ -518,7 +518,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        *  Returns true if the %string is empty.  Equivalent to 
        *  <code>*this == ""</code>.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const _GLIBCXX_NOEXCEPT
       { return this->size() == 0; }
 
diff --git a/libstdc++-v3/include/profile/array b/libstdc++-v3/include/profile/array
index dc7b594e29d..8f80e2a067f 100644
--- a/libstdc++-v3/include/profile/array
+++ b/libstdc++-v3/include/profile/array
@@ -124,7 +124,7 @@ namespace __profile
       constexpr size_type
       max_size() const noexcept { return _Nm; }
 
-      constexpr bool
+      _GLIBCXX_NODISCARD constexpr bool
       empty() const noexcept { return size() == 0; }
 
       // Element access.
diff --git a/libstdc++-v3/include/std/array b/libstdc++-v3/include/std/array
index ba52e3c2c89..02c6f4b4dbe 100644
--- a/libstdc++-v3/include/std/array
+++ b/libstdc++-v3/include/std/array
@@ -177,7 +177,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       constexpr size_type
       max_size() const noexcept { return _Nm; }
 
-      constexpr bool
+      _GLIBCXX_NODISCARD constexpr bool
       empty() const noexcept { return size() == 0; }
 
       // Element access.
diff --git a/libstdc++-v3/include/std/future b/libstdc++-v3/include/std/future
index 6cafde5ee6a..10136e57a84 100644
--- a/libstdc++-v3/include/std/future
+++ b/libstdc++-v3/include/std/future
@@ -1703,7 +1703,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   /// async
   template<typename _Fn, typename... _Args>
-    future<__async_result_of<_Fn, _Args...>>
+    _GLIBCXX_NODISCARD future<__async_result_of<_Fn, _Args...>>
     async(launch __policy, _Fn&& __fn, _Args&&... __args)
     {
       std::shared_ptr<__future_base::_State_base> __state;
@@ -1736,7 +1736,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   /// async, potential overload
   template<typename _Fn, typename... _Args>
-    inline future<__async_result_of<_Fn, _Args...>>
+    _GLIBCXX_NODISCARD inline future<__async_result_of<_Fn, _Args...>>
     async(_Fn&& __fn, _Args&&... __args)
     {
       return std::async(launch::async|launch::deferred,
diff --git a/libstdc++-v3/include/std/scoped_allocator b/libstdc++-v3/include/std/scoped_allocator
index 5a8495db21b..335df483f69 100644
--- a/libstdc++-v3/include/std/scoped_allocator
+++ b/libstdc++-v3/include/std/scoped_allocator
@@ -343,10 +343,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       const outer_allocator_type& outer_allocator() const noexcept
       { return static_cast<const _OuterAlloc&>(*this); }
 
-      pointer allocate(size_type __n)
+      _GLIBCXX_NODISCARD pointer allocate(size_type __n)
       { return __traits::allocate(outer_allocator(), __n); }
 
-      pointer allocate(size_type __n, const_void_pointer __hint)
+      _GLIBCXX_NODISCARD pointer allocate(size_type __n, const_void_pointer __hint)
       { return __traits::allocate(outer_allocator(), __n, __hint); }
 
       void deallocate(pointer __p, size_type __n)
diff --git a/libstdc++-v3/include/tr1/array b/libstdc++-v3/include/tr1/array
index e8266d7bc03..5c0857b960e 100644
--- a/libstdc++-v3/include/tr1/array
+++ b/libstdc++-v3/include/tr1/array
@@ -119,7 +119,7 @@ namespace tr1
       size_type 
       max_size() const { return _Nm; }
 
-      bool 
+      _GLIBCXX_NODISCARD bool 
       empty() const { return size() == 0; }
 
       // Element access.
diff --git a/libstdc++-v3/include/tr1/hashtable.h b/libstdc++-v3/include/tr1/hashtable.h
index eed79effb3c..c1b5c9e8fda 100644
--- a/libstdc++-v3/include/tr1/hashtable.h
+++ b/libstdc++-v3/include/tr1/hashtable.h
@@ -244,7 +244,7 @@ namespace tr1
       size() const
       { return _M_element_count; }
 
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return size() == 0; }
 
diff --git a/libstdc++-v3/include/tr1/regex b/libstdc++-v3/include/tr1/regex
index f0d0742860f..73c610d2bbd 100644
--- a/libstdc++-v3/include/tr1/regex
+++ b/libstdc++-v3/include/tr1/regex
@@ -1870,7 +1870,7 @@ namespace regex_constants
        * @retval true The %match_results object is empty.
        * @retval false The %match_results object is not empty.
        */
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const
       { return size() == 0; }
       
diff --git a/libstdc++-v3/include/tr2/dynamic_bitset b/libstdc++-v3/include/tr2/dynamic_bitset
index fb022f3b188..434a4cc87ec 100644
--- a/libstdc++-v3/include/tr2/dynamic_bitset
+++ b/libstdc++-v3/include/tr2/dynamic_bitset
@@ -1014,7 +1014,7 @@ namespace tr2
       { return this->_M_size(); }
 
       /// Returns true if the dynamic_bitset is empty.
-      bool
+      _GLIBCXX_NODISCARD bool
       empty() const noexcept
       { return (this->_M_Nb == 0); }
 
diff --git a/libstdc++-v3/libsupc++/eh_alloc.cc b/libstdc++-v3/libsupc++/eh_alloc.cc
index ad16699e7b8..005c28dbb11 100644
--- a/libstdc++-v3/libsupc++/eh_alloc.cc
+++ b/libstdc++-v3/libsupc++/eh_alloc.cc
@@ -86,7 +86,7 @@ namespace
     public:
       pool();
 
-      void *allocate (std::size_t);
+      _GLIBCXX_NODISCARD void *allocate (std::size_t);
       void free (void *);
 
       bool in_pool (void *);
diff --git a/libstdc++-v3/libsupc++/new b/libstdc++-v3/libsupc++/new
index a35972b08b3..6347d21b26f 100644
--- a/libstdc++-v3/libsupc++/new
+++ b/libstdc++-v3/libsupc++/new
@@ -122,9 +122,9 @@ namespace std
  *  Placement new and delete signatures (take a memory address argument,
  *  does nothing) may not be replaced by a user's program.
 */
-void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
+_GLIBCXX_NODISCARD void* operator new(std::size_t) _GLIBCXX_THROW (std::bad_alloc)
   __attribute__((__externally_visible__));
-void* operator new[](std::size_t) _GLIBCXX_THROW (std::bad_alloc)
+_GLIBCXX_NODISCARD void* operator new[](std::size_t) _GLIBCXX_THROW (std::bad_alloc)
   __attribute__((__externally_visible__));
 void operator delete(void*) _GLIBCXX_USE_NOEXCEPT
   __attribute__((__externally_visible__));
@@ -136,26 +136,26 @@ void operator delete(void*, std::size_t) _GLIBCXX_USE_NOEXCEPT
 void operator delete[](void*, std::size_t) _GLIBCXX_USE_NOEXCEPT
   __attribute__((__externally_visible__));
 #endif
-void* operator new(std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
+_GLIBCXX_NODISCARD void* operator new(std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
   __attribute__((__externally_visible__, __malloc__));
-void* operator new[](std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
+_GLIBCXX_NODISCARD void* operator new[](std::size_t, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
   __attribute__((__externally_visible__, __malloc__));
 void operator delete(void*, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
   __attribute__((__externally_visible__));
 void operator delete[](void*, const std::nothrow_t&) _GLIBCXX_USE_NOEXCEPT
   __attribute__((__externally_visible__));
 #if __cpp_aligned_new
-void* operator new(std::size_t, std::align_val_t)
+_GLIBCXX_NODISCARD void* operator new(std::size_t, std::align_val_t)
   __attribute__((__externally_visible__));
-void* operator new(std::size_t, std::align_val_t, const std::nothrow_t&)
+_GLIBCXX_NODISCARD void* operator new(std::size_t, std::align_val_t, const std::nothrow_t&)
   _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__, __malloc__));
 void operator delete(void*, std::align_val_t)
   _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
 void operator delete(void*, std::align_val_t, const std::nothrow_t&)
   _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
-void* operator new[](std::size_t, std::align_val_t)
+_GLIBCXX_NODISCARD void* operator new[](std::size_t, std::align_val_t)
   __attribute__((__externally_visible__));
-void* operator new[](std::size_t, std::align_val_t, const std::nothrow_t&)
+_GLIBCXX_NODISCARD void* operator new[](std::size_t, std::align_val_t, const std::nothrow_t&)
   _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__, __malloc__));
 void operator delete[](void*, std::align_val_t)
   _GLIBCXX_USE_NOEXCEPT __attribute__((__externally_visible__));
@@ -170,9 +170,9 @@ void operator delete[](void*, std::size_t, std::align_val_t)
 #endif // __cpp_aligned_new
 
 // Default placement versions of operator new.
-inline void* operator new(std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
+_GLIBCXX_NODISCARD inline void* operator new(std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
 { return __p; }
-inline void* operator new[](std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
+_GLIBCXX_NODISCARD inline void* operator new[](std::size_t, void* __p) _GLIBCXX_USE_NOEXCEPT
 { return __p; }
 
 // Default placement versions of operator delete.