[libc++] Remove old CI configurations and update the supported compiler versions

[philnik]

Summary

_LIBCPP_REMOVE_TRANSITIVE_INCLUDES doesn't do anything anymore in C++23 mode, so it's now just a duplicate of the C++23 configuration.
Also add new steps to the post-release checklist for updating the supported compilers.

[ldionne]

Please coordinate with @Mordante. I just approved a patch that removed support for Clang 13. I think this could become only a removal of the generic-no-transitive-includes CI configuration.

[Mordante]

Thanks for working on this!

libcxx/docs/index.rst

107

I would prefer to only mention releases here. Having Clang 16 may lead to confusion since it's not released yet.
For AppleClang we already have some version 14 support.
I feel having support for the work-in-progress function can be left implicit.

libcxx/utils/ci/buildkite-pipeline.yml

259

This part has already landed.

505

I didn't remove this part, and I would prefer it in a separate commit; which can be this commit.

[philnik]

libcxx/docs/index.rst

107

I was actually always confused by the latest two stable releases. The released versions also only claim support for the last two versions, i.e. libc++14 claims compatibility with clang 12 and 13, but not 14 (see https://releases.llvm.org/14.0.0/projects/libcxx/docs/index.html), which I find very confusing. The new wording makes the situation clear.

libcxx/utils/ci/buildkite-pipeline.yml

505

I'll split it if we want to reword the supported compilers.

[Mordante]

libcxx/docs/index.rst

107

I see what you mean. However I think this wording doesn't work. When LLVM 16 will be released and current trunk would refer to LLVM 17. So that means LLVM 16 supports 14, 15, and 17. Still not 16. Maybe then we should list it like suggested.

Then we need to make sure we update this just prior to a release. How about adding a pre-release checklist here https://libcxx.llvm.org/Contributing.html?

[ldionne]

Is this still relevant? If not, let's close.

[philnik]

Address comments

[ldionne]

libcxx/docs/Contributing.rst

65 ↗

(On Diff #484979)

The summary and commit message seem outdated.

73 ↗

(On Diff #484979)

74 ↗

(On Diff #484979)

libcxx/utils/ci/buildkite-pipeline.yml

490

You need to update run-buildbot as well to remove that job.

[philnik]

Address comments

libcxx/docs/index.rst

 
 Libc++ aims to support common compilers that implement the C++11 Standard. In order to strike a
 good balance between stability for users and maintenance cost, testing coverage and development
 velocity, libc++ drops support for older compilers as newer ones are released.
 
 ============ =============== ========================== =====================
 Compiler     Versions        Restrictions               Support policy
 ============ =============== ========================== =====================
-Clang        13, 14                                     latest two stable releases per `LLVM's release page <https://releases.llvm.org>`_
+Clang        14, 15, 16                                 latest two stable releases per `LLVM's release page <https://releases.llvm.org>`_ and current trunk
 AppleClang   13                                         latest stable release per `Xcode's release page <https://developer.apple.com/documentation/xcode-release-notes>`_
 Open XL      17.1 (AIX)                                 latest stable release per `Open XL's documentation page <https://www.ibm.com/docs/en/openxl-c-and-cpp-aix>`_
 GCC          12              In C++11 or later only     latest stable release per `GCC's release page <https://gcc.gnu.org/releases.html>`_
 ============ =============== ========================== =====================
 
 Libc++ also supports common platforms and architectures:
 
 =============== ========================= ============================

libcxx/utils/ci/buildkite-pipeline.yml

agents:
       queue: "libcxx-builders"
       os: "linux"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
     timeout_in_minutes: 120
 
-  - label: "Clang 13"
-    command: "libcxx/utils/ci/run-buildbot generic-cxx2b"
-    artifact_paths:
-      - "**/test-results.xml"
-      - "**/*.abilist"
-    env:
-        CC: "clang-13"
-        CXX: "clang++-13"
-    agents:
-      queue: "libcxx-builders"
-      os: "linux"
-    retry:
-      automatic:
-        - exit_status: -1  # Agent was lost
-          limit: 2
-    timeout_in_minutes: 120
-
   - label: "Clang 14"
     command: "libcxx/utils/ci/run-buildbot generic-cxx2b"
     artifact_paths:
       - "**/test-results.xml"
       - "**/*.abilist"
     env:
         CC: "clang-14"
         CXX: "clang++-14"
agents:
       queue: "libcxx-builders"
       os: "linux"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
     timeout_in_minutes: 120
 
-  - label: "No transitive includes"
-    command: "libcxx/utils/ci/run-buildbot generic-no-transitive-includes"
-    artifact_paths:
-      - "**/test-results.xml"
-      - "**/*.abilist"
-    env:
-        CC: "clang-${LLVM_HEAD_VERSION}"
-        CXX: "clang++-${LLVM_HEAD_VERSION}"
-    agents:
-      queue: "libcxx-builders"
-      os: "linux"
-    retry:
-      automatic:
-        - exit_status: -1  # Agent was lost
-          limit: 2
-    timeout_in_minutes: 120
-
   - label: "With LLVM's libunwind"
     command: "libcxx/utils/ci/run-buildbot generic-with_llvm_unwinder"
     artifact_paths:
       - "**/test-results.xml"
       - "**/*.abilist"
     env:
         CC: "clang-${LLVM_HEAD_VERSION}"
         CXX: "clang++-${LLVM_HEAD_VERSION}"