(original) (raw)

diff --git a/libcxx/include/__algorithm/ranges_clamp.h b/libcxx/include/__algorithm/ranges_clamp.h index 9613f7f37720a..e6c86207254a1 100644 --- a/libcxx/include/__algorithm/ranges_clamp.h +++ b/libcxx/include/__algorithm/ranges_clamp.h @@ -37,9 +37,10 @@ struct __fn { _LIBCPP_ASSERT_UNCATEGORIZED(!bool(std::invoke(__comp, std::invoke(__proj, __high), std::invoke(__proj, __low))), "Bad bounds passed to std::ranges::clamp"); - if (std::invoke(__comp, std::invoke(__proj, __value), std::invoke(__proj, __low))) + auto&& __projected = std::invoke(__proj, __value); + if (std::invoke(__comp, std::forward<decltype(__projected)>(__projected), std::invoke(__proj, __low))) return __low; - else if (std::invoke(__comp, std::invoke(__proj, __high), std::invoke(__proj, __value))) + else if (std::invoke(__comp, std::invoke(__proj, __high), std::forward<decltype(__projected)>(__projected))) return __high; else return __value; diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.clamp/ranges.clamp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.clamp/ranges.clamp.pass.cpp index 036552f75de4e..9dd749cf49619 100644 --- a/libcxx/test/std/algorithms/alg.sorting/alg.clamp/ranges.clamp.pass.cpp +++ b/libcxx/test/std/algorithms/alg.sorting/alg.clamp/ranges.clamp.pass.cpp @@ -19,6 +19,7 @@ #include #include #include +#include #include template @@ -38,6 +39,16 @@ static_assert(!HasClamp); static_assert(!HasClamp<int, nocomp="">); static_assert(!HasClamp<int, std::ranges::less,="" createnocomp="">); +struct EnsureValueCategoryComp { + constexpr bool operator()(const int&& x, const int&& y) const { return x < y; } + constexpr bool operator()(const int&& x, int& y) const { return x < y; } + constexpr bool operator()(int& x, const int&& y) const { return x < y; } + constexpr bool operator()(int& x, int& y) const { return x < y; } + constexpr bool operator()(std::same_as auto&& x, std::same_as auto&& y) const { + return x < y; + } +}; + constexpr bool test() { { // low < val < high int val = 2; @@ -68,45 +79,38 @@ constexpr bool test() { { // Check that a custom projection works. struct S { int i; - - constexpr const int& lvalue_proj() const { return i; } - constexpr int prvalue_proj() const { return i; } - }; - - struct Comp { - constexpr bool operator()(const int& lhs, const int& rhs) const { return lhs < rhs; } - constexpr bool operator()(int&& lhs, int&& rhs) const { return lhs > rhs; } + constexpr bool operator==(S const& other) const { return i == other.i; } }; auto val = S{10}; auto low = S{20}; auto high = S{30}; - // Check that the value category of the projection return type is preserved. - assert(&std::ranges::clamp(val, low, high, Comp{}, &S::lvalue_proj) == &low); - assert(&std::ranges::clamp(val, high, low, Comp{}, &S::prvalue_proj) == &low); + auto proj = [](S const& s) -> int const& { return s.i; }; + + assert(std::ranges::clamp(val, low, high, std::less{}, proj) == low); } - { // Check that the implementation doesn't cause double moves (which could result from calling the projection on - // `value` once and then forwarding the result into the comparator). - struct CheckDoubleMove { - int i; - bool moved = false; - - constexpr explicit CheckDoubleMove(int set_i) : i(set_i) {} - constexpr CheckDoubleMove(const CheckDoubleMove&) = default; - constexpr CheckDoubleMove(CheckDoubleMove&& rhs) noexcept : i(rhs.i) { - assert(!rhs.moved); - rhs.moved = true; - } + { // Ensure that we respect the value category of the projection when calling the comparator. + // This additional example was provided by Tim Song in https://github.com/microsoft/STL/issues/3970#issuecomment-1685120958\. + struct MoveProj { + constexpr int const&& operator()(int const& x) const { return std::move(x); } }; - auto val = CheckDoubleMove{20}; - auto low = CheckDoubleMove{10}; - auto high = CheckDoubleMove{30}; + static_assert(std::indirect_strict_weak_order<ensurevaluecategorycomp, std::projected<const="" int*,="" moveproj="">>); - auto moving_comp = [](CheckDoubleMove lhs, CheckDoubleMove rhs) { return lhs.i < rhs.i; }; - auto prvalue_proj = [](const CheckDoubleMove& x) -> CheckDoubleMove { return x; }; - assert(&std::ranges::clamp(val, low, high, moving_comp, prvalue_proj) == &val); + assert(std::ranges::clamp(0, 1, 2, EnsureValueCategoryComp{}, MoveProj{}) == 1); + } + + { // Make sure we don't call the projection more than three times per [alg.clamp], see #64717 + int counter = 0; + auto projection_function = [&counter](const int value) -> int { + counter++; + return value; + }; + assert(std::ranges::clamp(3, 2, 4, std::ranges::less{}, projection_function) == 3); +#if !(defined(_LIBCPP_ENABLE_SAFE_MODE) || defined(_LIBCPP_ENABLE_DEBUG_MODE)) + assert(counter <= 3); +#endif } return true; </ensurevaluecategorycomp,></int,></int,></decltype(__projected)></decltype(__projected)>