<algorithm>: ranges::minmax should dereference iterators only once

stl/inc/algorithm

@@ -10102,9 +10102,14 @@ namespace ranges {
             if constexpr (forward_range<_Rng> && _Prefer_iterator_copies<iterator_t<_Rng>>) {
                 const auto _Found = _RANGES _Minmax_element_unchecked(
                     _STD move(_UFirst), _STD move(_ULast), _Pass_fn(_Pred), _Pass_fn(_Proj));
+                if (_Found.min == _Found.max) {
+                    _Vty _Temp{*_Found.min};
+                    return {_Temp, _Temp};
+                }
                 return {static_cast<_Vty>(*_Found.min), static_cast<_Vty>(*_Found.max)};
             } else {
-                minmax_result<_Vty> _Found = {static_cast<_Vty>(*_UFirst), static_cast<_Vty>(*_UFirst)};
+                _Vty _Temp{*_UFirst};
+                minmax_result<_Vty> _Found = {_Temp, _Temp};
                 if (_UFirst == _ULast) {
                     return _Found;
                 }

tests/std/tests/P0896R4_ranges_alg_minmax/test.cpp

@@ -361,6 +361,16 @@ void test_gh_1893() {
     ASSERT(val == "meow");
 }
 
+void test_gh_2900() {
+    // GH-2900: <algorithm>: ranges::minmax initializes minmax_result with the moved value
+    {
+        vector<string> v{"1"};
+        auto [min, max] = ranges::minmax(ranges::subrange{make_move_iterator(v.begin()), make_move_iterator(v.end())});
+        assert(min == "1");
+        assert(max == "1");
+    }
+}
+
 int main() {
     STATIC_ASSERT((nonrange_tests(), true));
     nonrange_tests();
@@ -378,4 +388,5 @@ int main() {
     test_in<mm, const P>();
 
     test_gh_1893();
+    test_gh_2900();
 }