[libc++] Implement part of P2562R1: constexpr ranges::stable_sort
#128860
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@llvm/pr-subscribers-libcxx Author: A. Jiang (frederick-vs-ja) ChangesDrive-by: Unblocks test coverage for Fixes #119395. Full diff: https://github.com/llvm/llvm-project/pull/128860.diff 6 Files Affected:
diff --git a/libcxx/include/__algorithm/ranges_stable_sort.h b/libcxx/include/__algorithm/ranges_stable_sort.h
index 9c7df80ae9872..6e17d0d0c7ec4 100644
--- a/libcxx/include/__algorithm/ranges_stable_sort.h
+++ b/libcxx/include/__algorithm/ranges_stable_sort.h
@@ -41,7 +41,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD
namespace ranges {
struct __stable_sort {
template <class _Iter, class _Sent, class _Comp, class _Proj>
- _LIBCPP_HIDE_FROM_ABI static _Iter __stable_sort_fn_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
+ _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR_SINCE_CXX26 _Iter
+ __stable_sort_fn_impl(_Iter __first, _Sent __last, _Comp& __comp, _Proj& __proj) {
auto __last_iter = ranges::next(__first, __last);
auto&& __projected_comp = std::__make_projected(__comp, __proj);
@@ -52,13 +53,14 @@ struct __stable_sort {
template <random_access_iterator _Iter, sentinel_for<_Iter> _Sent, class _Comp = ranges::less, class _Proj = identity>
requires sortable<_Iter, _Comp, _Proj>
- _LIBCPP_HIDE_FROM_ABI _Iter operator()(_Iter __first, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
+ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 _Iter
+ operator()(_Iter __first, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
return __stable_sort_fn_impl(std::move(__first), std::move(__last), __comp, __proj);
}
template <random_access_range _Range, class _Comp = ranges::less, class _Proj = identity>
requires sortable<iterator_t<_Range>, _Comp, _Proj>
- _LIBCPP_HIDE_FROM_ABI borrowed_iterator_t<_Range>
+ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 borrowed_iterator_t<_Range>
operator()(_Range&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
return __stable_sort_fn_impl(ranges::begin(__r), ranges::end(__r), __comp, __proj);
}
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 7b4cb8e496196..8ef2ba84e6cc5 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -422,11 +422,12 @@ namespace ranges {
template<random_access_iterator I, sentinel_for<I> S, class Comp = ranges::less,
class Proj = identity>
requires sortable<I, Comp, Proj>
- I ranges::stable_sort(I first, S last, Comp comp = {}, Proj proj = {}); // since C++20
+ constexpr I // constexpr in C++26
+ ranges::stable_sort(I first, S last, Comp comp = {}, Proj proj = {}); // since C++20
template<random_access_range R, class Comp = ranges::less, class Proj = identity>
requires sortable<iterator_t<R>, Comp, Proj>
- borrowed_iterator_t<R>
+ constexpr borrowed_iterator_t<R> // constexpr in C++26
ranges::stable_sort(R&& r, Comp comp = {}, Proj proj = {}); // since C++20
template<random_access_iterator I, sentinel_for<I> S, class Comp = ranges::less,
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/ranges.stable.sort.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/ranges.stable.sort.pass.cpp
index c8f76b20c6825..5dedd54a4c009 100644
--- a/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/ranges.stable.sort.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.sorting/alg.sort/stable.sort/ranges.stable.sort.pass.cpp
@@ -13,11 +13,12 @@
// template<random_access_iterator I, sentinel_for<I> S, class Comp = ranges::less,
// class Proj = identity>
// requires sortable<I, Comp, Proj>
-// I ranges::stable_sort(I first, S last, Comp comp = {}, Proj proj = {}); // since C++20
+// constexpr I // constexpr since C++26
+// ranges::stable_sort(I first, S last, Comp comp = {}, Proj proj = {}); // since C++20
//
// template<random_access_range R, class Comp = ranges::less, class Proj = identity>
// requires sortable<iterator_t<R>, Comp, Proj>
-// borrowed_iterator_t<R>
+// constexpr borrowed_iterator_t<R> // constexpr since C++26
// ranges::stable_sort(R&& r, Comp comp = {}, Proj proj = {}); // since C++20
#include <algorithm>
@@ -57,7 +58,7 @@ static_assert(!HasStableSortR<UncheckedRange<int*>, BadComparator>);
static_assert(!HasStableSortR<UncheckedRange<const int*>>); // Doesn't satisfy `sortable`.
template <class Iter, class Sent, std::size_t N>
-void test_one(std::array<int, N> input, std::array<int, N> expected) {
+TEST_CONSTEXPR_CXX26 void test_one(std::array<int, N> input, std::array<int, N> expected) {
{ // (iterator, sentinel) overload.
auto sorted = input;
auto b = Iter(sorted.data());
@@ -81,7 +82,7 @@ void test_one(std::array<int, N> input, std::array<int, N> expected) {
}
template <class Iter, class Sent>
-void test_iterators_2() {
+TEST_CONSTEXPR_CXX26 void test_iterators_2() {
// Empty sequence.
test_one<Iter, Sent, 0>({}, {});
// 1-element sequence.
@@ -105,25 +106,25 @@ void test_iterators_2() {
}
template <class Iter>
-void test_iterators_1() {
+TEST_CONSTEXPR_CXX26 void test_iterators_1() {
test_iterators_2<Iter, Iter>();
test_iterators_2<Iter, sentinel_wrapper<Iter>>();
}
-void test_iterators() {
+TEST_CONSTEXPR_CXX26 void test_iterators() {
test_iterators_1<random_access_iterator<int*>>();
test_iterators_1<contiguous_iterator<int*>>();
test_iterators_1<int*>();
}
-void test() {
+TEST_CONSTEXPR_CXX26 bool test() {
test_iterators();
struct OrderedValue {
int value;
double original_order;
bool operator==(const OrderedValue&) const = default;
- auto operator<=>(const OrderedValue& rhs) const { return value <=> rhs.value; }
+ TEST_CONSTEXPR_CXX26 auto operator<=>(const OrderedValue& rhs) const { return value <=> rhs.value; }
};
{ // The sort is stable (equivalent elements remain in the same order).
@@ -214,24 +215,24 @@ void test() {
{ // `std::invoke` is used in the implementation.
struct S {
int i;
- S(int i_) : i(i_) {}
+ TEST_CONSTEXPR_CXX26 S(int i_) : i(i_) {}
- bool comparator(const S& rhs) const { return i < rhs.i; }
- const S& projection() const { return *this; }
+ TEST_CONSTEXPR_CXX26 bool comparator(const S& rhs) const { return i < rhs.i; }
+ TEST_CONSTEXPR_CXX26 const S& projection() const { return *this; }
bool operator==(const S&) const = default;
};
{
std::array in = {S{2}, S{3}, S{1}};
- auto last = std::ranges::stable_sort(in.begin(), in.end(), &S::comparator, &S::projection);
+ auto last = std::ranges::stable_sort(in.begin(), in.end(), &S::comparator, &S::projection);
assert((in == std::array{S{1}, S{2}, S{3}}));
assert(last == in.end());
}
{
std::array in = {S{2}, S{3}, S{1}};
- auto last = std::ranges::stable_sort(in, &S::comparator, &S::projection);
+ auto last = std::ranges::stable_sort(in, &S::comparator, &S::projection);
assert((in == std::array{S{1}, S{2}, S{3}}));
assert(last == in.end());
}
@@ -242,8 +243,6 @@ void test() {
std::ranges::stable_sort(std::array{1, 2, 3});
}
- // TODO: Enable the tests once the implementation switched to use iter_move/iter_swap
- /*
{ // ProxyIterator
{
std::array in = {2, 1, 3};
@@ -260,12 +259,15 @@ void test() {
assert((in == std::array{1, 2, 3}));
}
}
- */
+
+ return true;
}
int main(int, char**) {
test();
- // Note: `stable_sort` is not `constexpr`.
+#if TEST_STD_VER >= 26
+ static_assert(test());
+#endif
return 0;
}
diff --git a/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp b/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
index 0624a6c2d49c7..299478da22072 100644
--- a/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_dangling.pass.cpp
@@ -200,8 +200,12 @@ constexpr bool test_all() {
if (!std::is_constant_evaluated())
dangling_1st(std::ranges::stable_partition, in, unary_pred);
dangling_1st(std::ranges::sort, in);
+#if TEST_STD_VER < 26
if (!std::is_constant_evaluated())
+#endif
+ {
dangling_1st(std::ranges::stable_sort, in);
+ }
dangling_1st(std::ranges::partial_sort, in, mid);
dangling_1st(std::ranges::nth_element, in, mid);
if (!std::is_constant_evaluated())
diff --git a/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp b/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp
index acd7640b418eb..a01cdf1d3a179 100644
--- a/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_omitting_invoke.pass.cpp
@@ -167,8 +167,12 @@ constexpr bool test_all() {
if (!std::is_constant_evaluated())
test(std::ranges::stable_partition, in, &Foo::unary_pred, &Bar::val);
test(std::ranges::sort, in, &Foo::binary_pred, &Bar::val);
+#if TEST_STD_VER < 26
if (!std::is_constant_evaluated())
+#endif
+ {
test(std::ranges::stable_sort, in, &Foo::binary_pred, &Bar::val);
+ }
test_mid(std::ranges::partial_sort, in, mid, &Foo::binary_pred, &Bar::val);
test_mid(std::ranges::nth_element, in, mid, &Foo::binary_pred, &Bar::val);
if (!std::is_constant_evaluated())
diff --git a/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp b/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
index ca1433b778751..d85052c51973a 100644
--- a/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
+++ b/libcxx/test/std/algorithms/ranges_robust_against_proxy_iterators.pass.cpp
@@ -170,8 +170,12 @@ constexpr void run_tests() {
if (!std::is_constant_evaluated())
test(std::ranges::stable_partition, in, unary_pred);
test(std::ranges::sort, in);
+#if TEST_STD_VER < 26
if (!std::is_constant_evaluated())
+#endif
+ {
test(std::ranges::stable_sort, in);
+ }
test_mid(std::ranges::partial_sort, in, mid);
test_mid(std::ranges::nth_element, in, mid);
if (!std::is_constant_evaluated())
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Drive-by: Enables test coverage for `ranges::stable_sort` with proxy iterators.
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mordante
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Thanks! LGTM, modulo one nit.
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Drive-by: Enables test coverage for
ranges::stable_sortwith proxy iterators, and changes "constexpr in" to "constexpr since" in comments in<algorithm>Fixes #119395.