[gcc r14-5297] libstdc++: Fix forwarding in __take/drop_of_repeat_view [PR112453]

[gcc r14-5297] libstdc++: Fix forwarding in __take/drop_of_repeat_view [PR112453]

[Patrick Palka]

https://gcc.gnu.org/g:d63282fa5b587f1b994210212f236b998a332995

commit r14-5297-gd63282fa5b587f1b994210212f236b998a332995
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Nov 9 15:15:08 2023 -0500

    libstdc++: Fix forwarding in __take/drop_of_repeat_view [PR112453]
    
    We need to respect the value category of the repeat_view passed to these
    two functions when accessing the view's _M_value member.  This revealed
    that the space-efficient partial specialization of __box lacks && overloads
    of operator* to match those of the primary template (inherited from
    std::optional).
    
            PR libstdc++/112453
    
    libstdc++-v3/ChangeLog:
    
            * include/std/ranges (__detail::__box<_Tp>::operator*): Define
            && overloads as well.
            (__detail::__take_of_repeat_view): Forward __r when accessing
            its _M_value member.
            (__detail::__drop_of_repeat_view): Likewise.
            * testsuite/std/ranges/repeat/1.cc (test07): New test.
    
    Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

Diff:
---
 libstdc++-v3/include/std/ranges               | 20 +++++++++++++++-----
 libstdc++-v3/testsuite/std/ranges/repeat/1.cc | 13 +++++++++++++
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 7893e3a84c9..41f95dc8f78 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -250,13 +250,21 @@ namespace ranges
 	{ return true; };
 
 	constexpr _Tp&
-	operator*() noexcept
+	operator*() & noexcept
 	{ return _M_value; }
 
 	constexpr const _Tp&
-	operator*() const noexcept
+	operator*() const & noexcept
 	{ return _M_value; }
 
+	constexpr _Tp&&
+	operator*() && noexcept
+	{ return std::move(_M_value); }
+
+	constexpr const _Tp&&
+	operator*() const && noexcept
+	{ return std::move(_M_value); }
+
 	constexpr _Tp*
 	operator->() noexcept
 	{ return std::__addressof(_M_value); }
@@ -7799,9 +7807,10 @@ namespace views::__adaptor
 	  using _Tp = remove_cvref_t<_Range>;
 	  static_assert(__is_repeat_view<_Tp>);
 	  if constexpr (sized_range<_Tp>)
-	    return views::repeat(*__r._M_value, std::min(ranges::distance(__r), __n));
+	    return views::repeat(*std::forward<_Range>(__r)._M_value,
+				 std::min(ranges::distance(__r), __n));
 	  else
-	    return views::repeat(*__r._M_value, __n);
+	    return views::repeat(*std::forward<_Range>(__r)._M_value, __n);
 	}
 
       template<typename _Range>
@@ -7813,7 +7822,8 @@ namespace views::__adaptor
 	  if constexpr (sized_range<_Tp>)
 	    {
 	      auto __sz = ranges::distance(__r);
-	      return views::repeat(*__r._M_value, __sz - std::min(__sz, __n));
+	      return views::repeat(*std::forward<_Range>(__r)._M_value,
+				   __sz - std::min(__sz, __n));
 	    }
 	  else
 	    return __r;
diff --git a/libstdc++-v3/testsuite/std/ranges/repeat/1.cc b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
index 30636407ee2..0f6e551c1e9 100644
--- a/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
+++ b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
@@ -2,6 +2,7 @@
 
 #include <ranges>
 #include <algorithm>
+#include <memory>
 #include <testsuite_hooks.h>
 
 #if __cpp_lib_ranges_repeat != 202207L
@@ -137,6 +138,17 @@ test06()
   static_assert( requires { views::repeat(move_only{}, 2); } );
 }
 
+void
+test07()
+{
+  // PR libstdc++/112453
+  auto t1 = std::views::repeat(std::make_unique<int>(5)) | std::views::take(2);
+  auto d1 = std::views::repeat(std::make_unique<int>(5)) | std::views::drop(2);
+
+  auto t2 = std::views::repeat(std::make_unique<int>(5), 4) | std::views::take(2);
+  auto d2 = std::views::repeat(std::make_unique<int>(5), 4) | std::views::drop(2);
+}
+
 int
 main()
 {
@@ -146,4 +158,5 @@ main()
   static_assert(test04());
   test05();
   test06();
+  test07();
 }