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