<algorithm>: Fix ranges::_Rotate_one_left (#2188)

Co-authored-by: Stephan T. Lavavej <[email protected]>
microsoft · Sep 11, 2021 · 75e7d21 · 75e7d21
1 parent 3d02211
commit 75e7d21
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diff --git a/stl/inc/algorithm b/stl/inc/algorithm
@@ -6667,7 +6667,7 @@ namespace ranges {
     void _Rotate_one_left(_It _First, _It _Mid, _It _Last) {
         // exchanges the range [_First, _Mid) with [_Mid, _Last)
         _STL_INTERNAL_CHECK(_RANGES next(_First) == _Mid);
-        auto _Temp   = _RANGES iter_move(_Mid);
+        auto _Temp   = _RANGES iter_move(_First);
         auto _Result = _RANGES _Move_unchecked(_STD move(_Mid), _STD move(_Last), _STD move(_First));
         *_Result.out = _STD move(_Temp);
     }

diff --git a/tests/std/tests/P0896R4_ranges_alg_stable_sort/test.cpp b/tests/std/tests/P0896R4_ranges_alg_stable_sort/test.cpp
@@ -51,6 +51,16 @@ struct instantiator {
     }
 };
 
+void test_gh2187() {
+    constexpr array orig{0, 1, 3, 2, 5, 6, 4, 7, 8, 12, 9, 10, 12, 11, 13, 14, 17, 15, 16, 24, 18, 21, 19, 20, 22, 25,
+        23, 26, 27, 28, 29, 30, 31};
+    auto v = orig;
+    ranges::stable_sort(v);
+    assert(is_sorted(v.begin(), v.end()));
+    assert(is_permutation(v.begin(), v.end(), orig.begin(), orig.end()));
+}
+
 int main() {
     test_random<instantiator, P>();
+    test_gh2187();
 }