Implement feature test macros using a script.
Summary:
This patch implements all the feature test macros libc++ currently supports, as specified by the standard or cppreference prior to C++2a.
The tests and `<version>` header are generated using a script. The script contains a table of each feature test macro, the headers it should be accessible from, and its values of each dialect of C++.
When a new feature test macro is added or needed, the table should be updated and the script re-run.
Reviewers: mclow.lists, jfb, serge-sans-paille
Reviewed By: mclow.lists
Subscribers: arphaman, jfb, ldionne, libcxx-commits
Differential Revision: https://reviews.llvm.org/D56750
llvm-svn: 351286
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 32784a740a0282dc6f4390b683ed6c6516f4d66c
diff --git a/docs/DesignDocs/FeatureTestMacros.rst b/docs/DesignDocs/FeatureTestMacros.rst
new file mode 100644
index 0000000..d55af96
--- /dev/null
+++ b/docs/DesignDocs/FeatureTestMacros.rst
@@ -0,0 +1,44 @@
+===================
+Feature Test Macros
+===================
+
+.. contents::
+ :local:
+
+Overview
+========
+
+Libc++ implements the C++ feature test macros as specified in the C++2a standard,
+and before that in non-normative guiding documents (`See cppreference <https://en.cppreference.com/w/User:D41D8CD98F/feature_testing_macros>`)
+
+Design
+======
+
+Feature test macros are tricky to track, implement, test, and document correctly.
+They must be available from a list of headers, they may have different values in
+different dialects, and they may or may not be implemented by libc++. In order to
+track all of these conditions correctly and easily, we want a Single Source of
+Truth (SSoT) that defines each feature test macro, its values, the headers it
+lives in, and whether or not is is implemented by libc++. From this SSoA we
+have enough information to automatically generate the `<version>` header,
+the tests, and the documentation.
+
+Therefore we maintain a SSoA in
+`libcxx/test/std/language.support/support.limits/support.limits.general/generate_feature_test_macro_components.py`
+which doubles as a script to generate the following components:
+
+* The `<version>` header.
+* The version tests under `support.limits.general`.
+* Documentation of libc++'s implementation of each macro.
+
+Usage
+=====
+
+The `generate_feature_test_macro_components.py` script is used to track and
+update feature test macros in libc++.
+
+Whenever a feature test macro is added or changed, the table should be updated
+and the script should be re-ran. The script will clobber the existing test files
+and the documentation and it will generate a new `<version>` header as a
+temporary file. The generated `<version>` header should be merged with the
+existing one.
\ No newline at end of file
diff --git a/docs/FeatureTestMacroTable.rst b/docs/FeatureTestMacroTable.rst
new file mode 100644
index 0000000..d900497
--- /dev/null
+++ b/docs/FeatureTestMacroTable.rst
@@ -0,0 +1,200 @@
+.. _FeatureTestMacroTable:
+
+==========================
+Feature Test Macro Support
+==========================
+
+.. contents::
+ :local:
+
+Overview
+========
+
+This file documents the feature test macros currently supported by libc++.
+
+.. _feature-status:
+
+Status
+======
+
+.. table:: Current Status
+ :name: feature-status-table
+ :widths: auto
+
+ ================================================= =================
+ Macro Name Value
+ ================================================= =================
+ **C++ 14**
+ -------------------------------------------------------------------
+ ``__cpp_lib_chrono_udls`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_complex_udls`` ``201309L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_exchange_function`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_generic_associative_lookup`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_integer_sequence`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_integral_constant_callable`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_is_final`` ``201402L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_is_null_pointer`` ``201309L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_make_reverse_iterator`` ``201402L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_make_unique`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_null_iterators`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_quoted_string_io`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_result_of_sfinae`` ``201210L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_robust_nonmodifying_seq_ops`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_shared_timed_mutex`` ``201402L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_string_udls`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_transformation_trait_aliases`` ``201304L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_transparent_operators`` ``201210L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_tuple_element_t`` ``201402L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_tuples_by_type`` ``201304L``
+ ------------------------------------------------- -----------------
+ **C++ 17**
+ -------------------------------------------------------------------
+ ``__cpp_lib_addressof_constexpr`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_allocator_traits_is_always_equal`` ``201411L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_any`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_apply`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_array_constexpr`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_as_const`` ``201510L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_atomic_is_always_lock_free`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_bool_constant`` ``201505L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_boyer_moore_searcher`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_byte`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_chrono`` ``201611L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_clamp`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_enable_shared_from_this`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_execution`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_filesystem`` ``201703L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_gcd_lcm`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_hardware_interference_size`` ``201703L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_has_unique_object_representations`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_hypot`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_incomplete_container_elements`` ``201505L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_invoke`` ``201411L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_is_aggregate`` ``201703L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_is_invocable`` ``201703L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_is_swappable`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_launder`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_logical_traits`` ``201510L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_make_from_tuple`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_map_try_emplace`` ``201411L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_math_special_functions`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_memory_resource`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_node_extract`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_nonmember_container_access`` ``201411L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_not_fn`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_optional`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_parallel_algorithm`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_raw_memory_algorithms`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_sample`` ``201603L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_scoped_lock`` ``201703L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_shared_mutex`` ``201505L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_shared_ptr_arrays`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_shared_ptr_weak_type`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_string_view`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_to_chars`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_transparent_operators`` ``201510L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_type_trait_variable_templates`` ``201510L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_uncaught_exceptions`` ``201411L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_unordered_map_try_emplace`` ``201411L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_variant`` ``201606L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_void_t`` ``201411L``
+ ------------------------------------------------- -----------------
+ **C++ 2a**
+ -------------------------------------------------------------------
+ ``__cpp_lib_atomic_ref`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_bind_front`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_bit_cast`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_char8_t`` ``201811L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_concepts`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_constexpr_misc`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_constexpr_swap_algorithms`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_destroying_delete`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_erase_if`` ``201811L``
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_generic_unordered_lookup`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_is_constant_evaluated`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_list_remove_return_type`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_ranges`` *unimplemented*
+ ------------------------------------------------- -----------------
+ ``__cpp_lib_three_way_comparison`` *unimplemented*
+ ================================================= =================
+
+
diff --git a/docs/index.rst b/docs/index.rst
index bb56f2d..fddf74b 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -40,6 +40,11 @@
TestingLibcxx
+.. toctree::
+ :hidden:
+
+ FeatureTestMacroTable
+
Current Status
--------------
@@ -107,6 +112,7 @@
* `C++14 - Complete <http://libcxx.llvm.org/cxx1y_status.html>`__
* `C++17 - In Progress <http://libcxx.llvm.org/cxx1z_status.html>`__
* `Post C++14 Technical Specifications - In Progress <http://libcxx.llvm.org/ts1z_status.html>`__
+* :ref:`C++ Feature Test Macro Status <feature-status>`
Notes and Known Issues
----------------------
@@ -136,6 +142,7 @@
DesignDocs/VisibilityMacros
DesignDocs/ThreadingSupportAPI
DesignDocs/FileTimeType
+ DesignDocs/FeatureTestMacros
* `<atomic> design <http://libcxx.llvm.org/atomic_design.html>`_
* `<type_traits> design <http://libcxx.llvm.org/type_traits_design.html>`_