From 476047bf8e720f3dc359cf75d1241e13f8ba2350 Mon Sep 17 00:00:00 2001
From: Mark de Wever <koraq@xs4all.nl>
Date: Mon, 27 Sep 2021 20:53:59 +0200
Subject: [PATCH] [libc++] Adds back_insert_iterator::__get_container.

Adds a `__get_container` member as suggested by @Quuxplusone in D110497.

Includes  s/_LIBCPP_INLINE_VISIBILITY/_LIBCPP_HIDE_FROM_ABI/.

Reviewed By: Quuxplusone, #libc, ldionne

Differential Revision: https://reviews.llvm.org/D110573
---
 libcxx/include/__iterator/back_insert_iterator.h   |  2 ++
 .../back.insert.iter.ops/get_container.pass.cpp    | 37 ++++++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 libcxx/test/libcxx/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/get_container.pass.cpp

diff --git a/libcxx/include/__iterator/back_insert_iterator.h b/libcxx/include/__iterator/back_insert_iterator.h
index 9a4b057..7bbf5b09 100644
--- a/libcxx/include/__iterator/back_insert_iterator.h
+++ b/libcxx/include/__iterator/back_insert_iterator.h
@@ -55,6 +55,8 @@ public:
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 back_insert_iterator& operator*()     {return *this;}
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 back_insert_iterator& operator++()    {return *this;}
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 back_insert_iterator  operator++(int) {return *this;}
+
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _Container* __get_container() const { return container; }
 };
 
 template <class _Container>
diff --git a/libcxx/test/libcxx/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/get_container.pass.cpp b/libcxx/test/libcxx/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/get_container.pass.cpp
new file mode 100644
index 0000000..9f45848
--- /dev/null
+++ b/libcxx/test/libcxx/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/get_container.pass.cpp
@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <iterator>
+
+// back_insert_iterator
+
+// _Container* __get_container(); // constexpr in C++20
+
+#include <iterator>
+#include <vector>
+
+#include "test_macros.h"
+#include "nasty_containers.h"
+#include "test_constexpr_container.h"
+
+template <class C>
+TEST_CONSTEXPR_CXX20 bool test(C c) {
+  const std::back_insert_iterator<C> i(c);
+  assert(i.__get_container() == std::addressof(c));
+  return true;
+}
+
+int main(int, char**) {
+  test(std::vector<int>());
+  test(nasty_vector<int>());
+#if TEST_STD_VER >= 20
+  test(ConstexprFixedCapacityDeque<int, 10>());
+  static_assert(test(ConstexprFixedCapacityDeque<int, 10>()));
+#endif
+  return 0;
+}
-- 
2.7.4