1.. _ContributingToLibcxx: 2 3====================== 4Contributing to libc++ 5====================== 6 7.. contents:: 8 :local: 9 10Please read `this document <https://www.llvm.org/docs/Contributing.html>`__ on general rules to contribute to LLVM projects. 11 12Tasks and processes 13=================== 14 15This file contains notes about various tasks and processes specific to libc++. 16 17Looking for pre-existing reviews 18================================ 19 20Before you start working on any feature, please take a look at the open reviews 21to avoid duplicating someone else's work. You can do that by going to the website 22where code reviews are held, `Differential <https://reviews.llvm.org/differential>`__, 23and clicking on ``Libc++ Open Reviews`` in the sidebar to the left. If you see 24that your feature is already being worked on, please consider chiming in instead 25of duplicating work! 26 27Post-Release TODO 28================= 29 30After branching for an LLVM release: 31 321. Update ``_LIBCPP_VERSION`` in ``include/__config`` 332. Update the ``include/__libcpp_version`` file 343. Update the version number in ``docs/conf.py`` 35 36Modifying feature-test macros 37============================= 38 39When adding or updating feature-test macros, you should update the corresponding tests. 40To do that, modify ``feature_test_macros`` table in the script 41``utils/generate_feature_test_macro_components.py``, run it, and commit updated 42files. Running ``utils/generate_feature_test_macro_components.py`` should never 43generate diffs in a clean checkout; feel free to run it in your local checkout 44any time you want. 45 46 47Adding a new header TODO 48======================== 49 50When adding a new header to libc++: 51 521. Add a test under ``test/libcxx`` that the new header defines ``_LIBCPP_VERSION``. See ``test/libcxx/algorithms/version.pass.cpp`` for an example. 532. Run ``python utils/generate_header_tests.py``; verify and commit the changes. 543. Modify ``python utils/generate_header_inclusion_tests.py``; run it; verify and commit the changes. 554. Create a submodule in ``include/module.modulemap`` for the new header. 565. Update the ``include/CMakeLists.txt`` file to include the new header. 57 58Exporting new symbols from the library 59====================================== 60 61When exporting new symbols from libc++, you must update the ABI lists located in ``lib/abi``. 62To test whether the lists are up-to-date, please run the target ``check-cxx-abilist``. 63To regenerate the lists, use the target ``generate-cxx-abilist``. 64The ABI lists must be updated for all supported platforms; currently Linux and 65Apple. If you don't have access to one of these platforms, you can download an 66updated list from the failed build at 67`Buildkite <https://buildkite.com/llvm-project/libcxx-ci>`__. 68Look for the failed build and select the ``artifacts`` tab. There, download the 69abilist for the platform, e.g.: 70 71* C++20 for the Linux platform. 72* MacOS C++20 for the Apple platform. 73