[libc++] [docs] Update and move NOTES.txt to docs/Contributing.rst.

Also, add notes about exporting ABI symbols.
Later, we can add notes about using git-clang-format before sending a patch for review.

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D92300

Author: mkurdej

libcxx/NOTES.TXT

@@ -0,0 +1,46 @@
+.. _ContributingToLibcxx:
+
+======================
+Contributing to libc++
+======================
+
+.. contents::
+  :local:
+
+Please read `this document <https://www.llvm.org/docs/Contributing.html>`__ on general rules to contribute to LLVM projects.
+
+Tasks and processes
+===================
+
+This file contains notes about various tasks and processes specific to libc++.
+
+Post-Release TODO
+=================
+
+After branching for an LLVM release:
+
+1. Update ``_LIBCPP_VERSION`` in ``include/__config``
+2. Update the ``include/__libcpp_version`` file
+3. Update the version number in ``docs/conf.py``
+
+Adding a new header TODO
+========================
+
+When adding a new header to libc++:
+
+1. Add a test under ``test/libcxx`` that the new header defines ``_LIBCPP_VERSION``. See ``test/libcxx/algorithms/version.pass.cpp`` for an example.
+2. Update the following test files to include the new header:
+
+  * ``test/libcxx/double_include.sh.cpp``
+  * ``test/libcxx/min_max_macros.compile.pass.cpp``
+  * ``test/libcxx/no_assert_include.compile.pass.cpp``
+
+3. Create a submodule in ``include/module.modulemap`` for the new header.
+4. Update the ``include/CMakeLists.txt`` file to include the new header.
+
+Exporting new symbols from the library
+======================================
+
+When exporting new symbols from libc++, one must update the ABI lists located in ``lib/abi``.
+To test whether the lists are up-to-date, please run the target ``check-cxx-abilist``.
+To regenerate the lists, use the target ``generate-cxx-abilist``.

libcxx/docs/Contributing.rst

@@ -38,6 +38,7 @@ Getting Started with libc++
    UsingLibcxx
    BuildingLibcxx
    TestingLibcxx
+   Contributing
    Cxx1yStatus
    Cxx1zStatus
    Cxx2aStatus