WIP: Add Mac OS CI workflow

.github/workflows/test_t8code_macos.yml

@@ -0,0 +1,175 @@
+name: CMake tests t8code on Mac OS
+
+
+#  This file is part of t8code.
+#  t8code is a C library to manage a collection (a forest) of multiple
+#  connected adaptive space-trees of general element types in parallel.
+#
+#  Copyright (C) 2026 the developers
+#
+#  t8code is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  t8code is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with t8code; if not, write to the Free Software Foundation, Inc.,
+#  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+
+#  This workflow checks whether building and testing works on Mac OS.
+#  In the past, this meant that Mac-OS-specific problems in t8code became
+#  apparrent only in Trixi and T8Code.jl, where they are very hard and
+#  cumbersome to debug. This workflow is intended to avoid that by catching
+#  such problems as early as possible, i.e., within t8code's CI.
+#  not just all of t8code's remaining CI workflows rely
+#  To reduce runtime, (for now) only one configuration is run, that is, Debug mode
+#  with MPI, mesh handle, and Fortran interface. The main reason the external
+#  libraries (VTK, OpenCASCADE) are deactivated is that github's Mac OS runners
+#  do not use containers, meaning we would have to install the libraries in every
+#  single CI run (or cache them).
+
+env:
+  DEBUG_CONFIG: "-O1"
+
+on:
+  workflow_call:
+    # Note: To simplify adding more configurations of this workflow later, the MPI mode and the BUILD_TYPE
+    #       are passed as input, although currently only MPI on and Debug mode are tested.
+    inputs:
+      MAKEFLAGS:
+        required: true
+        type: string
+        description: 'Make flags to use for compilation (like -j4)'
+      MPI:
+        required: true
+        type: string
+        description: 'Use MPI for compilation (ON/OFF)'
+      BUILD_TYPE:
+        required: true
+        type: string
+        description: 'Build type (Release/Debug)'
+      TEST_LEVEL:
+        required: true
+        type: string
+        description: 'Test level used for configuring (T8_TEST_LEVEL_FULL, T8_TEST_LEVEL_MEDIUM, or T8_TEST_LEVEL_BASIC)'
+        default: 'T8_TEST_LEVEL_FULL'
+
+jobs:
+  t8code_cmake_tests:
+  #
+  # Container setup: To avoid unwanted side effects of gcc or mpich, an own Clang version of the
+  #                  t8-dependencies Docker image is used. Aside from some basic packages, it contains a manually built
+  #                  Clang version of OpenMPI.
+    timeout-minutes: 60
+    runs-on: macos-latest
+    steps:
+  #
+  # Part 1: Preparation
+  # -------------------------------------
+    - uses: actions/checkout@v6
+      with:
+        fetch-depth: 0
+    - name: Update packages
+      run: brew update
+    - name: Install missing packages via Homebrew
+      run: |
+        brew install open-mpi ninja cmake googletest openssl
+    - name: Export correct OpenMPI path to environment variables
+      run: |
+        export OPENMPI_BIN="/opt/homebrew/opt/open-mpi/bin"
+        echo OPENMPI_BIN="$OPENMPI_BIN" >> $GITHUB_ENV
+    - name: Reinstall gfortran
+      run: brew reinstall gfortran
+    - name: Show gfortran version
+      run: $OPENMPI_BIN/mpifort --version
+    #    which gfortran
+    # - name: Show Clang version
+    #   run: clang --version
+    - name: Show mpicc version
+      run: $OPENMPI_BIN/mpicc --version
+    - name: Show mpiexec version
+      run: $OPENMPI_BIN/mpiexec --version
+    - name: MPI sanity check (should print hostname four times)
+      run: $OPENMPI_BIN/mpiexec --oversubscribe -n 4 hostname
+    - name: init submodules
+      run: git submodule init
+    - name: update submodules
+      run: git submodule update
+    - name: Get input vars
+      run: export MAKEFLAGS="${{ inputs.MAKEFLAGS }}"
+        && export MPI="${{ inputs.MPI }}"
+        && export BUILD_TYPE="${{ inputs.BUILD_TYPE }}"
+        && echo MAKEFLAGS="$MAKEFLAGS" >> $GITHUB_ENV
+        && echo MPI="$MPI" >> $GITHUB_ENV
+        && echo BUILD_TYPE="$BUILD_TYPE" >> $GITHUB_ENV
+  #
+  # Part 2: Build t8code
+  # --------------------
+    # Define build config
+    - name: Set test level
+      run: export TEST_LEVEL_FLAG="-DT8CODE_TEST_LEVEL=${{ inputs.TEST_LEVEL }}"
+           && echo TEST_LEVEL_FLAG="$TEST_LEVEL_FLAG" >> $GITHUB_ENV
+    - name: build config variables
+      run: |
+        export CONFIG_OPTIONS="-GNinja -DCMAKE_INSTALL_PREFIX=$(pwd)/install \
+                               -DT8CODE_ENABLE_MPI=ON -DCMAKE_BUILD_TYPE=$BUILD_TYPE ${TEST_LEVEL_FLAG} -DCMAKE_C_FLAGS_DEBUG=${DEBUG_CONFIG} -DCMAKE_CXX_FLAGS_DEBUG=${DEBUG_CONFIG} \
+                               -DT8CODE_BUILD_PEDANTIC=ON -DT8CODE_BUILD_WALL=ON -DT8CODE_BUILD_WERROR=OFF -DT8CODE_BUILD_WEXTRA=ON \
+                               -DT8CODE_BUILD_FORTRAN_INTERFACE=ON -DT8CODE_BUILD_MESH_HANDLE=ON \
+                               -DT8CODE_ENABLE_OCC=OFF -DT8CODE_ENABLE_VTK=OFF"
+        echo CONFIG_OPTIONS="$CONFIG_OPTIONS" >> $GITHUB_ENV
+    # Run cmake
+    # Note that DT8CODE_CUSTOM_PARALLEL_TEST_COMMAND is not included in $CONFIG_OPTIONS because of whitespace issues.
+    - name: echo cmake line
+      run: echo 'cmake ../ $CONFIG_OPTIONS -DT8CODE_CUSTOM_PARALLEL_TEST_COMMAND="mpirun --oversubscribe -np 4"'
+    - name: cmake
+      run: mkdir build && cd build && cmake ../ $CONFIG_OPTIONS -DT8CODE_CUSTOM_PARALLEL_TEST_COMMAND="mpirun --oversubscribe -np 4"
+    # On failure, upload logs
+    - name: OnFailUploadLog
+      if: failure()
+      uses: actions/upload-artifact@v7
+      with:
+        name: cmake_w_clang_and_ompi_${{ inputs.BUILD_TYPE }}_MPI_${{ inputs.MPI }}.log
+        path: build/CMakeFiles/CMakeOutput.log
+    # Build with ninja
+    - name: ninja
+      run: cd build && ninja $MAKEFLAGS
+    - name: ninja install
+      run: cd build && ninja install $MAKEFLAGS
+  #
+  # Part 3: Run t8code tests
+  # ------------------------
+    # - name: Manual test
+      # run: |
+      #   cd build/test/t8_cmesh/
+      #   ./t8_gtest_compute_first_element_serial
+    - name: serial tests (if MPI is enabled)
+      run: cd build && ctest -R _serial
+      if: ${{ inputs.MPI == 'ON' }}
+    - name: parallel tests (if MPI is enabled)
+      run: |
+        cd build
+        ctest -R _parallel
+      # env:
+      #   # Note: These openmpi options are required to ensure stable runs in github workflows and avoid stalling.
+      #   #       In particular, they activate oversubscription and define the communication channels, here tcp (and self).
+      #   OMPI_ALLOW_RUN_AS_ROOT: 1
+      #   OMPI_ALLOW_RUN_AS_ROOT_CONFIRM: 1
+      #   OMPI_MCA_rmaps_base_oversubscribe: 1
+      #   OMPI_MCA_btl: self,tcp
+      #   OMPI_MCA_pml: ob1
+      if: ${{ inputs.MPI == 'ON' }}
+    - name: tests (if MPI is disabled)
+      run: cd build && ctest $MAKEFLAGS
+      if: ${{ inputs.MPI == 'OFF' }}
+    # On failure, upload logs
+    - name: OnFailUploadLog
+      if: failure()
+      uses: actions/upload-artifact@v7
+      with:
+        name: test-suite_w_clang_and_ompi_${{ inputs.BUILD_TYPE }}_MPI_${{ inputs.MPI }}.log
+        path: build/Testing/Temporary/LastTest.log