[libc++] Adds __cpp_lib_constexpr_algorithms to utility.

[Mordante]

Summary

Implements:

• LWG3792 __cpp_lib_constexpr_algorithms should also be defined in <utility>

Depends on D140407

[philnik]

LGTM with green CI.

libcxx/docs/Status/Cxx2bIssues.csv

234

I think we could claim this as implemented earlier, but I'm OK with claiming it in 16 too.

[Mordante]

Thanks for the review!

libcxx/docs/Status/Cxx2bIssues.csv

234

This issue is specifically about the missing feature-test macro. I agree the feature itself has been implemented earlier.

[philnik]

libcxx/docs/Status/Cxx2bIssues.csv

234

I mean that, since we provide all FTMs everywhere, we already provided this one in <utility> before.

[Mordante]

libcxx/docs/Status/Cxx2bIssues.csv

234

Ah yes I see. From that point of view we indeed added support before.

libcxx/docs/Status/Cxx2bIssues.csv

 "`3774 <https://wg21.link/LWG3774>`__","``<flat_set>`` should include ``<compare>``", "November 2022","","","|flat_containers|"
 "`3775 <https://wg21.link/LWG3775>`__","Broken dependencies in the ``Cpp17Allocator`` requirements", "November 2022","","",""
 "`3778 <https://wg21.link/LWG3778>`__","``vector<bool>`` missing exception specifications", "November 2022","","",""
 "`3781 <https://wg21.link/LWG3781>`__","The exposition-only alias templates ``cont-key-type`` and ``cont-mapped-type`` should be removed", "November 2022","","",""
 "`3782 <https://wg21.link/LWG3782>`__","Should ``<math.h>`` declare ``::lerp``?", "November 2022","","",""
 "`3784 <https://wg21.link/LWG3784>`__","std.compat should not provide ``::byte`` and its friends", "November 2022","","",""
 "`3785 <https://wg21.link/LWG3785>`__","``ranges::to`` is over-constrained on the destination type being a range", "November 2022","","","|ranges|"
 "`3788 <https://wg21.link/LWG3788>`__","``jthread::operator=(jthread&&)`` postconditions are unimplementable under self-assignment", "November 2022","","",""
-"`3792 <https://wg21.link/LWG3792>`__","``__cpp_lib_constexpr_algorithms`` should also be defined in ``<utility>``", "November 2022","","",""
+"`3792 <https://wg21.link/LWG3792>`__","``__cpp_lib_constexpr_algorithms`` should also be defined in ``<utility>``", "November 2022","|Complete|","16.0",""
 "`3795 <https://wg21.link/LWG3795>`__","Self-move-assignment of ``std::future`` and ``std::shared_future`` have unimplementable postconditions", "November 2022","","",""
 "`3796 <https://wg21.link/LWG3796>`__","``movable-box`` as member should use ``default-initialization`` instead of ``copy-initialization``", "November 2022","","","|ranges|"
 "`3798 <https://wg21.link/LWG3798>`__","Rvalue reference and ``iterator_category``", "November 2022","","",""
 "`3801 <https://wg21.link/LWG3801>`__","``cartesian_product_view::iterator::distance-from`` ignores the size of last underlying range", "November 2022","","","|ranges|"
 "`3814 <https://wg21.link/LWG3814>`__","Add freestanding items requested by NB comments", "November 2022","","",""
 "`3816 <https://wg21.link/LWG3816>`__","``flat_map`` and ``flat_multimap`` should impose sequence container requirements", "November 2022","","","|flat_containers|"
 "`3817 <https://wg21.link/LWG3817>`__","Missing preconditions on ``forward_list`` modifiers", "November 2022","","",""
 "`3818 <https://wg21.link/LWG3818>`__","Exposition-only concepts are not described in library intro", "November 2022","|Nothing to do|","",""
 "`3822 <https://wg21.link/LWG3822>`__","Avoiding normalization in ``filesystem::weakly_canonical``", "November 2022","","",""
 "`3823 <https://wg21.link/LWG3823>`__","Unnecessary precondition for ``is_aggregate``", "November 2022","","",""
 "`3824 <https://wg21.link/LWG3824>`__","Number of ``bind`` placeholders is underspecified", "November 2022","|Nothing to do|","",""
 "`3826 <https://wg21.link/LWG3826>`__","Redundant specification [for overload of yield_value]", "November 2022","","",""
 "","","","",""
 "`3631 <https://wg21.link/LWG3631>`__","``basic_format_arg(T&&)`` should use ``remove_cvref_t<T>`` throughout","Not voted in","|Complete|","15.0",""
 "`3645 <https://wg21.link/LWG3645>`__","``resize_and_overwrite`` is overspecified to call its callback with lvalues","Not voted in","|Complete|","14.0",""
 "","","","",""

libcxx/include/version

 __cpp_lib_char8_t                                       201907L <atomic> <filesystem> <istream>
                                                                 <limits> <locale> <ostream>
                                                                 <string> <string_view>
 __cpp_lib_chrono                                        201611L <chrono>
 __cpp_lib_chrono_udls                                   201304L <chrono>
 __cpp_lib_clamp                                         201603L <algorithm>
 __cpp_lib_complex_udls                                  201309L <complex>
 __cpp_lib_concepts                                      202002L <concepts>
-__cpp_lib_constexpr_algorithms                          201806L <algorithm>
+__cpp_lib_constexpr_algorithms                          201806L <algorithm> <utility>
 __cpp_lib_constexpr_bitset                              202207L <bitset>
 __cpp_lib_constexpr_charconv                            202207L <charconv>
 __cpp_lib_constexpr_cmath                               202202L <cmath> <cstdlib>
 __cpp_lib_constexpr_complex                             201711L <complex>
 __cpp_lib_constexpr_dynamic_alloc                       201907L <memory>
 __cpp_lib_constexpr_functional                          201907L <functional>
 __cpp_lib_constexpr_iterator                            201811L <iterator>
 __cpp_lib_constexpr_memory                              202202L <memory>

libcxx/test/std/language.support/support.limits/support.limits.general/utility.version.compile.pass.cpp

 // clang-format off
 
 // <utility>
 
 // Test the feature test macros defined by <utility>
 
 /*  Constant                                  Value
     __cpp_lib_as_const                        201510L [C++17]
+    __cpp_lib_constexpr_algorithms            201806L [C++20]
     __cpp_lib_constexpr_utility               201811L [C++20]
     __cpp_lib_exchange_function               201304L [C++14]
     __cpp_lib_forward_like                    202207L [C++2b]
     __cpp_lib_integer_comparison_functions    202002L [C++20]
     __cpp_lib_integer_sequence                201304L [C++14]
     __cpp_lib_ranges_zip                      202110L [C++2b]
     __cpp_lib_to_underlying                   202102L [C++2b]
     __cpp_lib_tuples_by_type                  201304L [C++14]
     __cpp_lib_unreachable                     202202L [C++2b]
 */
 
 #include <utility>
 #include "test_macros.h"
 
 #if TEST_STD_VER < 14
 
 # ifdef __cpp_lib_as_const
 #   error "__cpp_lib_as_const should not be defined before c++17"
 # endif
 
+# ifdef __cpp_lib_constexpr_algorithms
+#   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
+# endif
+
 # ifdef __cpp_lib_constexpr_utility
 #   error "__cpp_lib_constexpr_utility should not be defined before c++20"
 # endif
 
 # ifdef __cpp_lib_exchange_function
 #   error "__cpp_lib_exchange_function should not be defined before c++14"
 # endif
 

 # endif
 
 #elif TEST_STD_VER == 14
 
 # ifdef __cpp_lib_as_const
 #   error "__cpp_lib_as_const should not be defined before c++17"
 # endif
 
+# ifdef __cpp_lib_constexpr_algorithms
+#   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
+# endif
+
 # ifdef __cpp_lib_constexpr_utility
 #   error "__cpp_lib_constexpr_utility should not be defined before c++20"
 # endif
 
 # ifndef __cpp_lib_exchange_function
 #   error "__cpp_lib_exchange_function should be defined in c++14"
 # endif
 # if __cpp_lib_exchange_function != 201304L

 
 # ifndef __cpp_lib_as_const
 #   error "__cpp_lib_as_const should be defined in c++17"
 # endif
 # if __cpp_lib_as_const != 201510L
 #   error "__cpp_lib_as_const should have the value 201510L in c++17"
 # endif
 
+# ifdef __cpp_lib_constexpr_algorithms
+#   error "__cpp_lib_constexpr_algorithms should not be defined before c++20"
+# endif
+
 # ifdef __cpp_lib_constexpr_utility
 #   error "__cpp_lib_constexpr_utility should not be defined before c++20"
 # endif
 
 # ifndef __cpp_lib_exchange_function
 #   error "__cpp_lib_exchange_function should be defined in c++17"
 # endif
 # if __cpp_lib_exchange_function != 201304L

 
 # ifndef __cpp_lib_as_const
 #   error "__cpp_lib_as_const should be defined in c++20"
 # endif
 # if __cpp_lib_as_const != 201510L
 #   error "__cpp_lib_as_const should have the value 201510L in c++20"
 # endif
 
+# ifndef __cpp_lib_constexpr_algorithms
+#   error "__cpp_lib_constexpr_algorithms should be defined in c++20"
+# endif
+# if __cpp_lib_constexpr_algorithms != 201806L
+#   error "__cpp_lib_constexpr_algorithms should have the value 201806L in c++20"
+# endif
+
 # ifndef __cpp_lib_constexpr_utility
 #   error "__cpp_lib_constexpr_utility should be defined in c++20"
 # endif
 # if __cpp_lib_constexpr_utility != 201811L
 #   error "__cpp_lib_constexpr_utility should have the value 201811L in c++20"
 # endif
 
 # ifndef __cpp_lib_exchange_function

 
 # ifndef __cpp_lib_as_const
 #   error "__cpp_lib_as_const should be defined in c++2b"
 # endif
 # if __cpp_lib_as_const != 201510L
 #   error "__cpp_lib_as_const should have the value 201510L in c++2b"
 # endif
 
+# ifndef __cpp_lib_constexpr_algorithms
+#   error "__cpp_lib_constexpr_algorithms should be defined in c++2b"
+# endif
+# if __cpp_lib_constexpr_algorithms != 201806L
+#   error "__cpp_lib_constexpr_algorithms should have the value 201806L in c++2b"
+# endif
+
 # ifndef __cpp_lib_constexpr_utility
 #   error "__cpp_lib_constexpr_utility should be defined in c++2b"
 # endif
 # if __cpp_lib_constexpr_utility != 201811L
 #   error "__cpp_lib_constexpr_utility should have the value 201811L in c++2b"
 # endif
 
 # ifndef __cpp_lib_exchange_function

libcxx/utils/generate_feature_test_macro_components.py

feature_test_macros = [ add_version_header(x) for x in [
     "headers": ["complex"],
   }, {
     "name": "__cpp_lib_concepts",
     "values": { "c++20": 202002 },
     "headers": ["concepts"],
   }, {
     "name": "__cpp_lib_constexpr_algorithms",
     "values": { "c++20": 201806 },
-    "headers": ["algorithm"],
+    "headers": ["algorithm", "utility"],
   }, {
     "name": "__cpp_lib_constexpr_bitset",
     "values": { "c++2b": 202207 },
     "headers": ["bitset"],
   }, {
     "name": "__cpp_lib_constexpr_charconv",
     "values": { "c++2b": 202207 },
     "headers": ["charconv"],