Usa [[no_unique_address]] in join_with_view::sentinel

Author: JMazurkiewicz

libcxx/include/__ranges/join_with_view.h

@@ -400,7 +400,7 @@ struct join_with_view<_View, _Pattern>::__sentinel {
   using _Parent = __maybe_const<_Const, join_with_view>;
   using _Base   = __maybe_const<_Const, _View>;
 
-  sentinel_t<_Base> __end_ = sentinel_t<_Base>();
+  _LIBCPP_NO_UNIQUE_ADDRESS sentinel_t<_Base> __end_ = sentinel_t<_Base>();
 
   _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(_Parent& __parent) : __end_(ranges::end(__parent.__base_)) {}
 

libcxx/test/libcxx/ranges/range.adaptors/range.join.with/range.join.with.sentinel/no_unique_address.compile.pass.cpp

@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// XFAIL: msvc
+
+// <ranges>
+
+// This test ensures that we use `[[no_unique_address]]` in `join_with_view::sentinel`.
+
+#include <cstddef>
+#include <ranges>
+#include <string_view>
+
+template <bool Const>
+struct Iter {
+  using value_type      = std::string_view;
+  using difference_type = std::ptrdiff_t;
+
+  Iter& operator++();
+  Iter operator++(int);
+  value_type& operator*() const;
+  bool operator==(const Iter&) const;
+  bool operator==(std::default_sentinel_t) const;
+};
+
+struct View : std::ranges::view_base {
+  Iter<false> begin();
+  Iter<true> begin() const;
+  std::default_sentinel_t end() const;
+};
+
+using JWV = std::ranges::join_with_view<View, std::string_view>;
+
+template <class View>
+struct Test {
+  [[no_unique_address]] std::ranges::sentinel_t<View> se;
+  unsigned char pad;
+};
+
+static_assert(sizeof(Test<JWV>) == 1);
+static_assert(sizeof(Test<const JWV>) == 1);