[libc++][format] Updates feature-test macros.

[Mordante]

Summary

During the discussion on the SG-10 mailinglist regarding the format
feature-test macros voted in during the last plenary it turns out libc++
can't mark the format feature-test macro as implemented.

According to

https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations#__cpp_lib_format

the not yet implemented paper

P1361R2 Integration of chrono with text formatting

affects the feature test macro.

Note that P1361R2 doesn't mention the feature-test macro nor is there an
LWG-issue to address the issue. The reporter of the issue didn't recall
where this requirement exactly has been decided.

[ldionne]

libcxx/utils/generate_feature_test_macro_components.py

318

libcxx/docs/FeatureTestMacroTable.rst

.. table:: Current Status
     ``__cpp_lib_destroying_delete``                   ``201806L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_endian``                              ``201907L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_erase_if``                            ``202002L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_execution``                           *unimplemented*
     ------------------------------------------------- -----------------
-    ``__cpp_lib_format``                              ``202106L``
+    ``__cpp_lib_format``                              *unimplemented*
     ------------------------------------------------- -----------------
     ``__cpp_lib_generic_unordered_lookup``            ``201811L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_int_pow2``                            ``202002L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_integer_comparison_functions``        ``202002L``
     ------------------------------------------------- -----------------
     ``__cpp_lib_interpolate``                         ``201902L``

libcxx/include/version

 # if _LIBCPP_STD_VER > 17 && defined(__cpp_impl_destroying_delete) && __cpp_impl_destroying_delete >= 201806L
 #   define __cpp_lib_destroying_delete                  201806L
 # endif
 # define __cpp_lib_endian                               201907L
 # define __cpp_lib_erase_if                             202002L
 # undef  __cpp_lib_execution
 // # define __cpp_lib_execution                            201902L
 # if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
-#   define __cpp_lib_format                             202106L
+// #   define __cpp_lib_format                             202106L
 # endif
 # define __cpp_lib_generic_unordered_lookup             201811L
 # define __cpp_lib_int_pow2                             202002L
 # define __cpp_lib_integer_comparison_functions         202002L
 # define __cpp_lib_interpolate                          201902L
 # define __cpp_lib_is_constant_evaluated                201811L
 // # define __cpp_lib_is_layout_compatible                 201907L
 # define __cpp_lib_is_nothrow_convertible               201806L

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

 #elif TEST_STD_VER == 17
 
 # ifdef __cpp_lib_format
 #   error "__cpp_lib_format should not be defined before c++20"
 # endif
 
 #elif TEST_STD_VER == 20
 
-# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
+# if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++20"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++20"
 #   endif
-# else
+# else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined when the requirement '!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)' is not met!"
+#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
 #elif TEST_STD_VER > 20
 
-# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
+# if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++2b"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++2b"
 #   endif
-# else
+# else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined when the requirement '!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)' is not met!"
+#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
 #endif // TEST_STD_VER > 20
 

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

 #     error "__cpp_lib_filesystem should have the value 201703L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_filesystem
 #     error "__cpp_lib_filesystem should not be defined when the requirement '!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)' is not met!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
+# if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++20"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++20"
 #   endif
-# else
+# else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined when the requirement '!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)' is not met!"
+#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
 # ifdef __cpp_lib_forward_like
 #   error "__cpp_lib_forward_like should not be defined before c++2b"
 # endif
 
 # ifndef __cpp_lib_gcd_lcm

 #     error "__cpp_lib_filesystem should have the value 201703L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_filesystem
 #     error "__cpp_lib_filesystem should not be defined when the requirement '!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)' is not met!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)
+# if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_format
 #     error "__cpp_lib_format should be defined in c++2b"
 #   endif
 #   if __cpp_lib_format != 202106L
 #     error "__cpp_lib_format should have the value 202106L in c++2b"
 #   endif
-# else
+# else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_format
-#     error "__cpp_lib_format should not be defined when the requirement '!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)' is not met!"
+#     error "__cpp_lib_format should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_forward_like
 #   error "__cpp_lib_forward_like should be defined in c++2b"
 # endif
 # if __cpp_lib_forward_like != 202207L
 #   error "__cpp_lib_forward_like should have the value 202207L in c++2b"

libcxx/utils/generate_feature_test_macro_components.py

feature_test_macros = [ add_version_header(x) for x in [
   }, {
     "name": "__cpp_lib_filesystem",
     "values": { "c++17": 201703 },
     "headers": ["filesystem"],
     "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)",
     "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)"
   }, {
     "name": "__cpp_lib_format",
-    # P2508, P2286, and P2419 were accepted in the same plenary and modify this
-    # feature-test macro. We expect to see an LWG issue soon. For now keep the
-    # value as is.
-    # TODO FMT Set P2508's feature-test macro.
-    #"values": { "c++20": 202106, "c++23": 202207" },
-    "values": { "c++20": 202106 },
+    "values": {
+        # "c++20": 201907 Not implemented P1361R2 Integration of chrono with text formatting
+        # "c++20": 202106 Fully implemented
+        # "c++20": 202110 Not implemented P2372R3 Fixing locale handling in chrono formatters
+        "c++20": 202106,
+        # "c++23": 202207, Not implemented P2419R2 Clarify handling of encodings in localized formatting of chrono types
+        },
     "headers": ["format"],
     "test_suite_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
     "libcxx_guard": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_format) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_FORMAT)",
+    "unimplemented": True,
   }, {
     "name": "__cpp_lib_forward_like",
     "values": { "c++2b": 202207 },
     "headers": ["utility"],
   }, {
     "name": "__cpp_lib_gcd_lcm",
     "values": { "c++17": 201606 },
     "headers": ["numeric"],