[libc++] Make CC and CXX environment variables mandatory in run-buildbot (#166875)

Previously, the bootstrapping-build job defined in run-buildbot required the CC and CXX environment variables to be defined even though run-buildbot documents these environment variables as being optional. It also relied on ccache being available. Refactor run-buildbot to make CC and CXX mandatory, and refactor various places in the CI where we called run-buildbot without setting CC and CXX. After this patch, all places that use run-buildbot are setting CC and CXX before calling the script, which makes it easier to track what compiler is used where. This also allows simplifying run-buildbot itself. Finally, this patch makes ccache optional for running the bootstrapping build.
2025-12-02 08:58:00 -05:00 · 2025-12-02 08:58:00 -05:00 · cd5ed7ca87
commit cd5ed7ca87
parent 63f48fd829
5 changed files with 102 additions and 63 deletions
--- a/.github/workflows/libcxx-build-and-test.yaml
+++ b/.github/workflows/libcxx-build-and-test.yaml
@ -223,6 +223,9 @@ jobs:
          source .venv/bin/activate
          python -m pip install psutil
          xcrun bash libcxx/utils/ci/run-buildbot ${{ matrix.config }}
+        env:
+          CC: clang
+          CXX: clang++
      - uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
        if: always()  # Upload artifacts even if the build or test suite fails
        with:
@ -241,16 +244,16 @@ jobs:
      fail-fast: false
      matrix:
        include:
-        - { config: clang-cl-dll, mingw: false }
-        - { config: clang-cl-static, mingw: false }
-        - { config: clang-cl-no-vcruntime, mingw: false }
-        - { config: clang-cl-debug, mingw: false }
-        - { config: clang-cl-static-crt, mingw: false }
-        - { config: mingw-dll, mingw: true }
-        - { config: mingw-static, mingw: true }
-        - { config: mingw-dll-i686, mingw: true }
-        - { config: mingw-incomplete-sysroot, mingw: true }
-        - { config: mingw-static, mingw: true, runner: windows-11-arm }
+        - { config: clang-cl-dll,             mingw: false, cc: clang-cl, cxx: clang-cl }
+        - { config: clang-cl-static,          mingw: false, cc: clang-cl, cxx: clang-cl }
+        - { config: clang-cl-no-vcruntime,    mingw: false, cc: clang-cl, cxx: clang-cl }
+        - { config: clang-cl-debug,           mingw: false, cc: clang-cl, cxx: clang-cl }
+        - { config: clang-cl-static-crt,      mingw: false, cc: clang-cl, cxx: clang-cl }
+        - { config: mingw-dll,                mingw: true,  cc: cc,       cxx: c++ }
+        - { config: mingw-dll,                mingw: true,  cc: i686-w64-mingw32-clang, cxx: i686-w64-mingw32-clang++ }
+        - { config: mingw-static,             mingw: true,  cc: cc,       cxx: c++ }
+        - { config: mingw-incomplete-sysroot, mingw: true,  cc: cc,       cxx: c++ }
+        - { config: mingw-static,             mingw: true,  cc: cc,       cxx: c++, runner: windows-11-arm }
    runs-on: ${{ matrix.runner != '' && matrix.runner || 'windows-2022' }}
    steps:
      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
@ -286,5 +289,7 @@ jobs:
        run: |
          echo "c:\Program Files\LLVM\bin" | Out-File -FilePath $Env:GITHUB_PATH -Encoding utf8 -Append
      - name: Build and test
-        run: |
-          bash libcxx/utils/ci/run-buildbot ${{ matrix.config }}
+        run: bash libcxx/utils/ci/run-buildbot ${{ matrix.config }}
+        env:
+          CC: ${{ matrix.cc }}
+          CXX: ${{ matrix.cxx }}
--- a/.github/workflows/libcxx-check-generated-files.yml
+++ b/.github/workflows/libcxx-check-generated-files.yml
@ -22,3 +22,6 @@ jobs:

      - name: Check generated files
        run: libcxx/utils/ci/run-buildbot check-generated-output
+        env:
+          CC: cc
+          CXX: c++
--- a/libcxx/docs/AddingNewCIJobs.rst
+++ b/libcxx/docs/AddingNewCIJobs.rst
@ -28,6 +28,9 @@ An example of a job definition is:

  - label: "C++11"
    command: "libcxx/utils/ci/run-buildbot generic-cxx11"
+    env:
+      CC: clang
+      CXX: clang++
    artifact_paths:
      - "**/test-results.xml"
    agents:
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@ -37,6 +37,9 @@ steps:
  steps:
  - label: AArch64
    command: libcxx/utils/ci/run-buildbot aarch64
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: aarch64
@ -44,6 +47,9 @@ steps:

  - label: AArch64 -fno-exceptions
    command: libcxx/utils/ci/run-buildbot aarch64-no-exceptions
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: aarch64
@ -51,6 +57,9 @@ steps:

  - label: Armv8
    command: libcxx/utils/ci/run-buildbot armv8
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: armv8l
@ -58,6 +67,9 @@ steps:

  - label: Armv8 -fno-exceptions
    command: libcxx/utils/ci/run-buildbot armv8-no-exceptions
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: armv8l
@ -65,6 +77,9 @@ steps:

  - label: Armv7
    command: libcxx/utils/ci/run-buildbot armv7
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: armv8l
@ -72,6 +87,9 @@ steps:

  - label: Armv7 -fno-exceptions
    command: libcxx/utils/ci/run-buildbot armv7-no-exceptions
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: armv8l
@ -79,6 +97,9 @@ steps:

  - label: Armv7-M picolibc
    command: libcxx/utils/ci/run-buildbot armv7m-picolibc
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: aarch64
@ -86,6 +107,9 @@ steps:

  - label: Armv7-M picolibc -fno-exceptions
    command: libcxx/utils/ci/run-buildbot armv7m-picolibc-no-exceptions
+    env:
+      CC: cc
+      CXX: c++
    agents:
      queue: libcxx-builders-linaro-arm
      arch: aarch64
@ -131,6 +155,9 @@ steps:
  steps:
  - label: Android 5.0, x86 NDK
    command: libcxx/utils/ci/run-buildbot android-ndk-21-def-x86
+    env:
+      CC: /opt/android/clang/clang-current/bin/clang
+      CXX: /opt/android/clang/clang-current/bin/clang++
    agents:
      queue: libcxx-builders
      os: android
@ -138,6 +165,9 @@ steps:

  - label: Android 13, x86_64 NDK
    command: libcxx/utils/ci/run-buildbot android-ndk-33-goog-x86_64
+    env:
+      CC: /opt/android/clang/clang-current/bin/clang
+      CXX: /opt/android/clang/clang-current/bin/clang++
    agents:
      queue: libcxx-builders
      os: android
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@ -30,17 +30,41 @@ ${PROGNAME} [options] <BUILDER>

 Environment variables
 CC                  The C compiler to use, this value is used by CMake. This
-                    variable is optional.
+                    variable is mandatory.

 CXX                 The C++ compiler to use, this value is used by CMake. This
-                    variable is optional.
-
-CLANG_FORMAT        The clang-format binary to use when generating the format
-                    ignore list.
+                    variable is mandatory.

+CCACHE              The ccache binary to use. This variable is optional and is only
+                    used by the bootstrapping build.
 EOF
 }

+function step() {
+  endstep
+  set +x
+  if [[ ! -z ${GITHUB_ACTIONS+x} ]]; then
+    echo "::group::$1"
+    export IN_GROUP=1
+  else
+    echo "--- $1"
+  fi
+  set -x
+}
+
+function endstep() {
+  set +x
+  if [[ ! -z ${GITHUB_ACTIONS+x} ]] && [[ ! -z ${IN_GROUP+x} ]]; then
+    echo "::endgroup::"
+    unset IN_GROUP
+  fi
+  set -x
+}
+
+function error() {
+    echo "::error::$1"
+}
+
 if [[ $# == 0 ]]; then
   usage
   exit 0
@ -71,30 +95,22 @@ MONOREPO_ROOT="${MONOREPO_ROOT:="$(git rev-parse --show-toplevel)"}"
 BUILD_DIR="${BUILD_DIR:=${MONOREPO_ROOT}/build/${BUILDER}}"
 INSTALL_DIR="${BUILD_DIR}/install"

-function step() {
-  endstep
-  set +x
-  if [[ ! -z ${GITHUB_ACTIONS+x} ]]; then
-    echo "::group::$1"
-    export IN_GROUP=1
-  else
-    echo "--- $1"
-  fi
-  set -x
-}
+if [ -z ${CC+x} ]; then
+    error "Environment variable CC must be defined"
+    exit 1
+fi

-function endstep() {
-  set +x
-  if [[ ! -z ${GITHUB_ACTIONS+x} ]] && [[ ! -z ${IN_GROUP+x} ]]; then
-    echo "::endgroup::"
-    unset IN_GROUP
-  fi
-  set -x
-}
+if [ -z ${CXX+x} ]; then
+    error "Environment variable CXX must be defined"
+    exit 1
+fi

-function error() {
-    echo "::error::$1"
-}
+# Print the version of a few tools to aid diagnostics in some cases
+step "Diagnose tools in use"
+cmake --version
+ninja --version
+${CC} --version
+${CXX} --version

 function clean() {
    rm -rf "${BUILD_DIR}"
@ -127,11 +143,7 @@ function generate-cmake() {
 }

 function generate-cmake-libcxx-win() {
-    generate-cmake-base \
-          -DLLVM_ENABLE_RUNTIMES="libcxx" \
-          -DCMAKE_C_COMPILER=clang-cl \
-          -DCMAKE_CXX_COMPILER=clang-cl \
-          "${@}"
+    generate-cmake-base -DLLVM_ENABLE_RUNTIMES="libcxx" "${@}"
 }

 function generate-cmake-android() {
@ -216,12 +228,6 @@ function test-armv7m-picolibc() {
    check-runtimes
 }

-# Print the version of a few tools to aid diagnostics in some cases
-step "Diagnose tools in use"
-cmake --version
-ninja --version
-if [ ! -z "${CXX}" ]; then ${CXX} --version; fi
-
 case "${BUILDER}" in
 check-generated-output)
    # `! foo` doesn't work properly with `set -e`, use `! foo || false` instead.
@ -358,12 +364,16 @@ generic-ubsan)
 bootstrapping-build)
    clean

+    if [ ! -z ${CCACHE+x} ]; then
+        COMPILER_LAUNCHER="-DCMAKE_CXX_COMPILER_LAUNCHER=${CCACHE}"
+    fi
+
    step "Generating CMake"
    cmake \
          -S "${MONOREPO_ROOT}/llvm" \
          -B "${BUILD_DIR}" \
          -GNinja \
-          -DCMAKE_CXX_COMPILER_LAUNCHER="ccache" \
+          ${COMPILER_LAUNCHER} \
          -DCMAKE_BUILD_TYPE=Release \
          -DCMAKE_INSTALL_PREFIX="${INSTALL_DIR}" \
          -DLLVM_ENABLE_PROJECTS="clang;lldb" \
@ -691,14 +701,6 @@ mingw-static)
          -DLIBUNWIND_ENABLE_SHARED=OFF
    check-runtimes
 ;;
-mingw-dll-i686)
-    clean
-    generate-cmake \
-          -DCMAKE_C_COMPILER=i686-w64-mingw32-clang \
-          -DCMAKE_CXX_COMPILER=i686-w64-mingw32-clang++ \
-          -C "${MONOREPO_ROOT}/libcxx/cmake/caches/MinGW.cmake"
-    check-runtimes
-;;
 mingw-incomplete-sysroot)
    # When bringing up a new cross compiler from scratch, we build
    # libunwind/libcxx in a setup where the toolchain is incomplete and
@ -743,10 +745,6 @@ android-ndk-*)
    fi
    ARCH=$(arch_of_emu_img ${ANDROID_EMU_IMG})

-    # Use the Android compiler by default.
-    export CC=${CC:-/opt/android/clang/clang-current/bin/clang}
-    export CXX=${CXX:-/opt/android/clang/clang-current/bin/clang++}
-
    # The NDK libc++_shared.so is always built against the oldest supported API
    # level. When tests are run against a device with a newer API level, test
    # programs can be built for any supported API level, but building for the