From 4d1b19695669e6c67b9c3df07673bc22cae3a662 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomasz=20Kami=C5=84ski?= <tkaminsk@redhat.com>
Date: Mon, 24 Mar 2025 18:04:28 +0100
Subject: [PATCH] libstdc++: Fix handling of common cpp20-only ranges for flat
 sets [PR119415]
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These patch add check to verify if common range iterators satisfies
Cpp17LegacyIterator requirements (__detail::__cpp17_input_iterator),
before invoking overloads of insert that accepts two iterators.
As such overloads existed before c++20 iterators were introduced,
they commonly assume existence of iterator_traits<..>::iterator_category,
and passing a cpp20-only iterators, leads to hard errors.

In case if user-defined container wants to support more efficient
insertion in such cases, it should provided insert_range method,
as in the case of standard containers.

	PR libstdc++/119415

libstdc++-v3/ChangeLog:

	* include/std/flat_set (_Flat_set_impl:insert_range):
	Add __detail::__cpp17_input_iterator check.
	* testsuite/23_containers/flat_multiset/1.cc: New tests
	* testsuite/23_containers/flat_set/1.cc: New tests

Reviewed-by: Patrick Palka <ppalka@redhat.com>, Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
---
 libstdc++-v3/include/std/flat_set             |  3 ++-
 .../23_containers/flat_multiset/1.cc          | 27 +++++++++++++++++++
 .../testsuite/23_containers/flat_set/1.cc     | 27 +++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/flat_set b/libstdc++-v3/include/std/flat_set
index 9240f2b9a2e..bab56742ddd 100644
--- a/libstdc++-v3/include/std/flat_set
+++ b/libstdc++-v3/include/std/flat_set
@@ -480,7 +480,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  typename container_type::iterator __it;
 	  if constexpr (requires { _M_cont.insert_range(_M_cont.end(), __rg); })
 	    __it = _M_cont.insert_range(_M_cont.end(), __rg);
-	  else if constexpr (ranges::common_range<_Rg>)
+	  else if constexpr (ranges::common_range<_Rg>
+			     && __detail::__cpp17_input_iterator<ranges::iterator_t<_Rg>>)
 	    __it = _M_cont.insert(_M_cont.end(), ranges::begin(__rg), ranges::end(__rg));
 	  else
 	    {
diff --git a/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc b/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
index 910f5dca5be..cc31164315a 100644
--- a/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
+++ b/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
@@ -143,6 +143,32 @@ test06()
   VERIFY( std::ranges::equal(s, (int[]){1, 2, 3, 4, 5}) );
 }
 
+template<typename T>
+struct NoInsertRange : std::vector<T>
+{
+  using std::vector<T>::vector;
+
+  template<typename It, typename R>
+  void insert_range(typename std::vector<T>::const_iterator, R&&) = delete;
+};
+
+void test07()
+{
+#ifdef __SIZEOF_INT128__
+  // PR libstdc++/119415 - flat_foo::insert_range cannot handle common ranges
+  // on c++20 only iterators
+  auto r = std::views::iota(__int128(1), __int128(6));
+
+  std::flat_multiset<int> s;
+  s.insert_range(r);
+  VERIFY( std::ranges::equal(s, (int[]){1, 2, 3, 4, 5}) );
+
+  std::flat_multiset<int, std::less<int>, NoInsertRange<int>> s2;
+  s2.insert_range(r);
+  VERIFY( std::ranges::equal(s2, (int[]){1, 2, 3, 4, 5}) );
+#endif
+}
+
 int
 main()
 {
@@ -153,4 +179,5 @@ main()
   test04();
   test05();
   test06();
+  test07();
 }
diff --git a/libstdc++-v3/testsuite/23_containers/flat_set/1.cc b/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
index f0eaac936bf..16881d788fc 100644
--- a/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
+++ b/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
@@ -158,6 +158,32 @@ test06()
   VERIFY( std::ranges::equal(s, (int[]){1, 2, 3, 4, 5}) );
 }
 
+template<typename T>
+struct NoInsertRange : std::vector<T>
+{
+  using std::vector<T>::vector;
+
+  template<typename It, typename R>
+  void insert_range(typename std::vector<T>::const_iterator, R&&) = delete;
+};
+
+void test07()
+{
+#ifdef __SIZEOF_INT128__
+  // PR libstdc++/119415 - flat_foo::insert_range cannot handle common ranges
+  // on c++20 only iterators
+  auto r = std::views::iota(__int128(1), __int128(6));
+
+  std::flat_set<int> s;
+  s.insert_range(r);
+  VERIFY( std::ranges::equal(s, (int[]){1, 2, 3, 4, 5}) );
+
+  std::flat_set<int, std::less<int>, NoInsertRange<int>> s2;
+  s2.insert_range(r);
+  VERIFY( std::ranges::equal(s2, (int[]){1, 2, 3, 4, 5}) );
+#endif
+}
+
 int
 main()
 {
@@ -168,4 +194,5 @@ main()
   test04();
   test05();
   test06();
+  test07();
 }