[PATCH] libstdc++: Fix handling of common cpp20-only ranges for flat sets [PR119415]

[Tomasz Kamiński]

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_multiset::insert_range,
	flat_set::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
---
Testing on x86_64-linux. OK for trunk?

 libstdc++-v3/include/std/flat_set             |  3 +-
 .../23_containers/flat_multiset/1.cc          | 18 ++++++++++++
 .../testsuite/23_containers/flat_set/1.cc     | 28 +++++++++++++++++++
 3 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/flat_set b/libstdc++-v3/include/std/flat_set
index 9240f2b9a2e..ea416e67503 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..0858be4a9fe 100644
--- a/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
+++ b/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
@@ -143,6 +143,23 @@ test06()
   VERIFY( std::ranges::equal(s, (int[]){1, 2, 3, 4, 5}) );
 }
 
+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 +170,5 @@ 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..374be80bb9d 100644
--- a/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
+++ b/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
@@ -8,6 +8,7 @@
 
 #include <deque>
 #include <ranges>
+#include <spanstream>
 #include <vector>
 #include <testsuite_allocator.h>
 #include <testsuite_hooks.h>
@@ -158,6 +159,32 @@ 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 +195,5 @@ main()
   test04();
   test05();
   test06();
+  test07();
 }
-- 
2.48.1