.travis.yml

# ==================================================================================================
#     Header
# ==================================================================================================

# General settings
language: cpp
cache: apt

# Jobs are on linux/bionic unless specified otherwise
os: linux
dist: bionic

# We only want to run specific branches
branches:
  only:
    - master
    - dev

# We split the jobs into stages to get a better overview
stages:
  - "Default"
  - "Latest"
  - "Legacy"

# ==================================================================================================
#     Job Matrix
# ==================================================================================================

jobs:
  include:

    # ==========================================================================
    #     trusty
    # ==========================================================================

    # Cannot use gcc 4.8 because of missing regex implementation.

    # - name: "trusty / default / debug"
    #   stage: "Default"
    #   os: linux
    #   dist: trusty

    # - name: "trusty / default / release"
    #   stage: "Default"
    #   os: linux
    #   dist: trusty
    #   env: BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     trusty / gcc
    # --------------------------------------------------------------------------

    # # Cannot use gcc 4.8 because of missing regex implementation.
    # - name: "trusty / g++-4.8 / debug"
    #   stage: "Legacy"
    #   os: linux
    #   dist: trusty
    #   addons: { apt: { packages: ["g++-4.8"] } }
    #   env: COMPILER=g++-4.8

    - name: "trusty / g++-4.9 / debug"
      stage: "Legacy"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-4.9"] } }
      env: COMPILER=g++-4.9

    - name: "trusty / g++-5 / debug"
      stage: "Legacy"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-5"] } }
      env: COMPILER=g++-5

    - name: "trusty / g++-6 / debug"
      stage: "Legacy"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-6"] } }
      env: COMPILER=g++-6

    - name: "trusty / g++-7 / debug"
      stage: "Legacy"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-7"] } }
      env: COMPILER=g++-7

    - name: "trusty / g++-8 / debug"
      stage: "Legacy"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-8"] } }
      env: COMPILER=g++-8

    - name: "trusty / g++-9 / debug"
      stage: "Latest"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-9"] } }
      env: COMPILER=g++-9

    - name: "trusty / g++-9 / release"
      stage: "Latest"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-9"] } }
      env: COMPILER=g++-9 BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     trusty / clang
    # --------------------------------------------------------------------------

    # # Cannot use clang++ 3.5 because exception_ptr is not yet implemented.
    # - name: "trusty / clang++-3.5 / debug"
    #   stage: "Legacy"
    #   os: linux
    #   dist: trusty
    #   addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.5"] } }
    #   env: COMPILER=clang++-3.5 OPENMP=OFF

    - name: "trusty / clang++-3.6 / debug"
      stage: "Legacy"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.6"] } }
      env: COMPILER=clang++-3.6 OPENMP=OFF

    # # Somehow, this just does not work... leave it for now.
    # - name: "trusty / clang++-3.7 / debug"
    #   stage: "Legacy"
    #   os: linux
    #   dist: trusty
    #   addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.7", "libiomp-dev"] } }
    #   env: COMPILER=clang++-3.7

    - name: "trusty / clang++-3.8 / debug"
      stage: "Legacy"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.8", "libiomp-dev"] } }
      env: COMPILER=clang++-3.8

    - name: "trusty / clang++-3.9 / debug"
      stage: "Latest"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.9", "libiomp-dev"] } }
      env: COMPILER=clang++-3.9

    - name: "trusty / clang++-3.9 / release"
      stage: "Latest"
      os: linux
      dist: trusty
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.9", "libiomp-dev"] } }
      env: COMPILER=clang++-3.9 BUILD_TYPE=RELEASE

    # ==========================================================================
    #     xenial
    # ==========================================================================

    - name: "xenial / default / debug"
      stage: "Default"
      os: linux
      dist: xenial

    - name: "xenial / default / release"
      stage: "Default"
      os: linux
      dist: xenial
      env: BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     xenial / gcc
    # --------------------------------------------------------------------------

    # # Cannot use gcc 4.8 because of missing regex implementation.
    # - name: "xenial / g++-4.8 / debug"
    #   stage: "Legacy"
    #   os: linux
    #   dist: xenial
    #   addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-4.8"] } }
    #   env: COMPILER=g++-4.8

    - name: "xenial / g++-4.9 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-4.9"] } }
      env: COMPILER=g++-4.9

    - name: "xenial / g++-5 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-5"] } }
      env: COMPILER=g++-5

    - name: "xenial / g++-6 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-6"] } }
      env: COMPILER=g++-6

    - name: "xenial / g++-7 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-7"] } }
      env: COMPILER=g++-7

    - name: "xenial / g++-8 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-8"] } }
      env: COMPILER=g++-8

    - name: "xenial / g++-9 / debug"
      stage: "Latest"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-9"] } }
      env: COMPILER=g++-9

    - name: "xenial / g++-9 / release"
      stage: "Latest"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-9"] } }
      env: COMPILER=g++-9 BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     xenial / clang
    # --------------------------------------------------------------------------

    # # Cannot use clang++ 3.5 because exception_ptr is not yet implemented.
    # - name: "xenial / clang++-3.5 / debug"
    #   stage: "Legacy"
    #   os: linux
    #   dist: xenial
    #   addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.5"] } }
    #   env: COMPILER=clang++-3.5 OPENMP=OFF

    - name: "xenial / clang++-3.6 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.6"] } }
      env: COMPILER=clang++-3.6 OPENMP=OFF

    # In theory, clang++-3.7 is the first version that supports OpenMP. But there are still issues,
    # so we have to deactivate OpenMP here.
    - name: "xenial / clang++-3.7 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.7", "libiomp-dev"] } }
      env: COMPILER=clang++-3.7 OPENMP=OFF

    - name: "xenial / clang++-3.8 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.8", "libiomp-dev"] } }
      env: COMPILER=clang++-3.8

    - name: "xenial / clang++-3.9 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.9", "libiomp-dev"] } }
      env: COMPILER=clang++-3.9

    - name: "xenial / clang++-4.0 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-4.0", "libiomp-dev"] } }
      env: COMPILER=clang++-4.0

    - name: "xenial / clang++-5.0 / debug"
      stage: "Legacy"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-5.0", "libiomp-dev"] } }
      env: COMPILER=clang++-5.0

    - name: "xenial / clang++-6.0 / debug"
      stage: "Latest"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-6.0", "libiomp-dev"] } }
      env: COMPILER=clang++-6.0

    - name: "xenial / clang++-6.0 / release"
      stage: "Latest"
      os: linux
      dist: xenial
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-6.0", "libiomp-dev"] } }
      env: COMPILER=clang++-6.0 BUILD_TYPE=RELEASE

    # ==========================================================================
    #     bionic
    # ==========================================================================

    - name: "bionic / default / debug"
      stage: "Default"
      os: linux
      dist: bionic

    - name: "bionic / default / release"
      stage: "Default"
      os: linux
      dist: bionic
      env: BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     bionic / gcc
    # --------------------------------------------------------------------------

    # # Cannot use gcc 4.8 because of missing regex implementation.
    # - name: "bionic / g++-4.8 / debug"
    #   stage: "Legacy"
    #   os: linux
    #   dist: bionic
    #   addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-4.8"] } }
    #   env: COMPILER=g++-4.8

    - name: "bionic / g++-5 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-5"] } }
      env: COMPILER=g++-5

    - name: "bionic / g++-6 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-6"] } }
      env: COMPILER=g++-6

    - name: "bionic / g++-7 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-7"] } }
      env: COMPILER=g++-7

    - name: "bionic / g++-8 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-8"] } }
      env: COMPILER=g++-8

    - name: "bionic / g++-9 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-9"] } }
      env: COMPILER=g++-9

    - name: "bionic / g++-10 / debug"
      stage: "Latest"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-10"] } }
      env: COMPILER=g++-10

    - name: "bionic / g++-10 / release"
      stage: "Latest"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["g++-10"] } }
      env: COMPILER=g++-10 BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     bionic / clang
    # --------------------------------------------------------------------------

    - name: "bionic / clang++-3.9 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-3.9", "libiomp-dev"] } }
      env: COMPILER=clang++-3.9

    - name: "bionic / clang++-4.0 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-4.0", "libiomp-dev"] } }
      env: COMPILER=clang++-4.0

    - name: "bionic / clang++-5.0 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-5.0", "libiomp-dev"] } }
      env: COMPILER=clang++-5.0

    - name: "bionic / clang++-6.0 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-6.0", "libiomp-dev"] } }
      env: COMPILER=clang++-6.0

    - name: "bionic / clang++-7 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-7", "libiomp-dev"] } }
      env: COMPILER=clang++-7

    - name: "bionic / clang++-8 / debug"
      stage: "Legacy"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-8", "libiomp-dev"] } }
      env: COMPILER=clang++-8

    - name: "bionic / clang++-9 / debug"
      stage: "Latest"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-9", "libiomp-dev"] } }
      env: COMPILER=clang++-9

    - name: "bionic / clang++-9 / release"
      stage: "Latest"
      os: linux
      dist: bionic
      addons: { apt: { sources: ["ubuntu-toolchain-r-test"], packages: ["clang-9", "libiomp-dev"] } }
      env: COMPILER=clang++-9 BUILD_TYPE=RELEASE

    # ==========================================================================
    #     osx
    # ==========================================================================

    # Need to deactivate OpenMP for default build, as standard osx clang does not support it.

    - name: "osx / default / debug"
      stage: "Default"
      os: osx
      env: OPENMP=OFF

    - name: "osx / default / release"
      stage: "Default"
      os: osx
      env: OPENMP=OFF BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     osx versions / apple
    # --------------------------------------------------------------------------

    # Default apple clang does not support openmp, so deactivate it here.

    - name: "osx / xcode6.4 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode6.4
      env: OPENMP=OFF

    - name: "osx / xcode7.3 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode7.3
      env: OPENMP=OFF

    - name: "osx / xcode8 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode8
      env: OPENMP=OFF

    - name: "osx / xcode8.3 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode8.3
      env: OPENMP=OFF

    - name: "osx / xcode9 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode9
      env: OPENMP=OFF

    - name: "osx / xcode9.2 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode9.2
      env: OPENMP=OFF

    - name: "osx / xcode9.3 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode9.3
      env: OPENMP=OFF

    - name: "osx / xcode9.4 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode9.4
      env: OPENMP=OFF

    - name: "osx / xcode10 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10
      env: OPENMP=OFF

    - name: "osx / xcode10.1 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10.1
      env: OPENMP=OFF

    - name: "osx / xcode10.2 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10.2
      env: OPENMP=OFF

    - name: "osx / xcode10.3 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10.3
      env: OPENMP=OFF

    - name: "osx / xcode11 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode11
      env: OPENMP=OFF

    - name: "osx / xcode11.1 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode11.1
      env: OPENMP=OFF

    - name: "osx / xcode11.2 / apple / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode11.2
      env: OPENMP=OFF

    - name: "osx / xcode11.3 / apple / debug"
      stage: "Latest"
      os: osx
      osx_image: xcode11.3
      env: OPENMP=OFF

    - name: "osx / xcode11.3 / apple / release"
      stage: "Latest"
      os: osx
      osx_image: xcode11.3
      env: OPENMP=OFF BUILD_TYPE=RELEASE

    # --------------------------------------------------------------------------
    #     osx versions / clang
    # --------------------------------------------------------------------------

    # Here, we install llvm and openmp explicityly, to test that as well.

    # As of now (April 2020), travis homebrew is broken and needs to run `update` before it is able
    # to install anything. However, for the older versions of osx, the update takes longer than
    # travis max job time, so we cannot do this. That means, we cannot install llvm and libomp to
    # get OpenMP support. Without llvm, these runs are the same as the above apple clang runs,
    # and hence, for now, we can deactivate all of them. See
    # https://travis-ci.community/t/macos-build-fails-because-of-homebrew-bundle-unknown-command/7296/10

    # - name: "osx / xcode6.4 / clang / debug"
    #   stage: "Legacy"
    #   os: osx
    #   osx_image: xcode6.4
    #   addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }
    #
    # - name: "osx / xcode7.3 / clang / debug"
    #   stage: "Legacy"
    #   os: osx
    #   osx_image: xcode7.3
    #   addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }
    #
    # - name: "osx / xcode8 / clang / debug"
    #   stage: "Legacy"
    #   os: osx
    #   osx_image: xcode8
    #   addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }
    #
    # - name: "osx / xcode8.3 / clang / debug"
    #   stage: "Legacy"
    #   os: osx
    #   osx_image: xcode8.3
    #   addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }
    #
    # - name: "osx / xcode9 / clang / debug"
    #   stage: "Legacy"
    #   os: osx
    #   osx_image: xcode9
    #   addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }
    #
    # - name: "osx / xcode9.2 / clang / debug"
    #   stage: "Legacy"
    #   os: osx
    #   osx_image: xcode9.2
    #   addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode9.3 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode9.3
      addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode9.4 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode9.4
      addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode10 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10
      addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode10.1 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10.1
      addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode10.2 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10.2
      addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode10.3 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode10.3
      addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode11 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode11
      addons: { homebrew: { packages: ["llvm", "libomp"], update: true } }

    - name: "osx / xcode11.1 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode11.1
      addons: { homebrew: { packages: ["llvm", "libomp"] } }

    - name: "osx / xcode11.2 / clang / debug"
      stage: "Legacy"
      os: osx
      osx_image: xcode11.2
      addons: { homebrew: { packages: ["llvm", "libomp"] } }

    - name: "osx / xcode11.3 / clang / debug"
      stage: "Latest"
      os: osx
      osx_image: xcode11.3
      addons: { homebrew: { packages: ["llvm", "libomp"] } }

    - name: "osx / xcode11.3 / clang / release"
      stage: "Latest"
      os: osx
      osx_image: xcode11.3
      addons: { homebrew: { packages: ["llvm", "libomp"] } }
      env: BUILD_TYPE=RELEASE

    # ==========================================================================
    #     windows
    # ==========================================================================

    # Too many errors for now. Maybe later.
    # - name: "windows / default"
    #   stage: "Default"
    #   os: windows
    #   env: ZLIB=OFF OPENMP=OFF

    # ==========================================================================
    #     Exclude
    # ==========================================================================

  exclude:

    # Shortcuts to not have to comment out the whole matrix above for travis debugging.
    # - os: windows
    # - os: osx
    # - os: linux
    # - dist: trusty
    # - dist: xenial
    # - dist: bionic
    # - stage: "Default"
    # - stage: "Latest"
    # - stage: "Legacy"

# ==================================================================================================
#     Install
# ==================================================================================================

before_install:

  # --------------------------------------------------------------------------
  #     Toolchain
  # --------------------------------------------------------------------------

  # List available gcc and clang versions
  # - apt-cache pkgnames g++ | sort
  # - apt-cache pkgnames clang | sort

  # install ubuntu toolchain
  - |
    if [[ "${TRAVIS_OS_NAME}" == "linux" ]]; then
      echo "adding toolchain"
      sudo apt-get install -y software-properties-common
      sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
      sudo apt-get update -qq
    fi

  # --------------------------------------------------------------------------
  #     Paths and Environment
  # --------------------------------------------------------------------------

  # The following homebrew packages are not on the path by default. We need to prepend them to the
  # path explicitly, so that clang can find OpenMP.
  # set llvm path
  - |
    if [ "$TRAVIS_OS_NAME" == "osx" ]; then
      echo "exporting llvm path"
      export PATH="$(brew --prefix llvm)/bin:$PATH";

      # To use OpenMP on Mac, we need custom clang versions. So, we need to set custom paths here.
      if [ "${OPENMP}" != "OFF" ]; then
        export COMPILER=/usr/local/opt/llvm/bin/clang++
        export CFLAGS="-I /usr/local/include -I/usr/local/opt/llvm/include"
        export CXXFLAGS="-I /usr/local/include -I/usr/local/opt/llvm/include"
        export LDFLAGS="-L /usr/local/lib -L/usr/local/opt/llvm/lib"
      fi

      # Bugfix for https://github.com/Homebrew/homebrew-core/issues/52461-mlinker-version=450
      # Otherwise, we get "ld: unknown option: -platform_version"
      if [[ "${TRAVIS_OSX_IMAGE}" == "xcode10.2" || "${TRAVIS_OSX_IMAGE}" == "xcode10.3" ]]; then
        export CXXFLAGS="${CXXFLAGS} -mlinker-version=450"
        export LDFLAGS="${LDFLAGS} -mlinker-version=450"
      fi
    fi

  # We need a few backs and forths between the variables, in the following order:
  #  1. For default builds, COMPILER is not set, so we use CXX instead.
  #  2. We also need to set CXX, as travis is so nice as to override this otherwise.
  - if [[ "${COMPILER}" == "" ]]; then COMPILER=${CXX}; fi
  - export CXX=${COMPILER}

install:

  # --------------------------------------------------------------------------
  #     Directories
  # --------------------------------------------------------------------------

  # Dependencies required by the CI are installed in ${TRAVIS_BUILD_DIR}/ci/
  - DEPS_DIR="${TRAVIS_BUILD_DIR}/ci"
  - mkdir -p "${DEPS_DIR}"
  - cd "${DEPS_DIR}"

  # --------------------------------------------------------------------------
  #     Clang libc++
  # --------------------------------------------------------------------------

  # clang install libc++
  # based on https://github.com/ldionne/hana/blob/master/.travis.yml
  - |
    LLVM_INSTALL=${DEPS_DIR}/llvm/install
    if [[ "${TRAVIS_OS_NAME}" == "linux" && "${CXX%%+*}" == "clang" ]]; then
      if   [[ "${CXX}" == "clang++-3.5" ]]; then LLVM_VERSION="3.5.1";
      elif [[ "${CXX}" == "clang++-3.6" ]]; then LLVM_VERSION="3.6.2";
      elif [[ "${CXX}" == "clang++-3.7" ]]; then LLVM_VERSION="3.7.1";
      elif [[ "${CXX}" == "clang++-3.8" ]]; then LLVM_VERSION="3.8.1";
      elif [[ "${CXX}" == "clang++-3.9" ]]; then LLVM_VERSION="3.9.1";
      elif [[ "${CXX}" == "clang++-4.0" ]]; then LLVM_VERSION="4.0.1";
      elif [[ "${CXX}" == "clang++-5.0" ]]; then LLVM_VERSION="5.0.2";
      elif [[ "${CXX}" == "clang++-6.0" ]]; then LLVM_VERSION="6.0.1";
      elif [[ "${CXX}" == "clang++-7" ]];   then LLVM_VERSION="7.0.1";
      elif [[ "${CXX}" == "clang++-8" ]];   then LLVM_VERSION="8.0.0";
      elif [[ "${CXX}" == "clang++-9" ]];   then LLVM_VERSION="9.0.0";
      else
        echo "Unknown clang version ${CXX}"
        exit 1
      fi

      # bionic clang 3.9 and 4.0 miss a file in their libstdc++, hence linking fails
      # solution from https://github.com/carla-simulator/carla/issues/503#issuecomment-397658790
      if [[ "${TRAVIS_DIST}" == "bionic" ]] && [[ "${CXX}" == "clang++-3.9" ||  "${CXX}" == "clang++-4.0" ]]; then
        sudo ln -s /usr/include/locale.h /usr/include/xlocale.h
      fi

      if [[ "${TRAVIS_DIST}" == "bionic" ]] ; then
        # Tests to get clang to compile with libc++ instead of libstdc++ on bionic.
        # Did not work after several tries, so for now, we just compile with the given standard
        # library. After all, we are interested in whether our code compiles - the standard library
        # implementation should not change that.
        :

        # export CXXFLAGS="-isystem /usr/local/include/c++/v1 -stdlib=libc++ -nostdinc++"
        # export LDFLAGS="-L /usr/local/lib -L /usr/local/lib/c++/v1 -l c++ -l c++abi"
        # export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:/usr/local/lib:/usr/local/lib/c++/v1"

        # export CXXFLAGS="-stdlib=libc++ -nostdinc++"
        # export LDFLAGS="-l c++ -l c++abi"
      else
        LLVM_URL="http://llvm.org/releases/${LLVM_VERSION}/llvm-${LLVM_VERSION}.src.tar.xz"
        LIBCXX_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxx-${LLVM_VERSION}.src.tar.xz"
        LIBCXXABI_URL="http://llvm.org/releases/${LLVM_VERSION}/libcxxabi-${LLVM_VERSION}.src.tar.xz"

        mkdir -p llvm llvm/build llvm/projects/libcxx llvm/projects/libcxxabi
        travis_retry wget -O - ${LLVM_URL} | tar --strip-components=1 -xJ -C llvm
        travis_retry wget -O - ${LIBCXX_URL} | tar --strip-components=1 -xJ -C llvm/projects/libcxx
        travis_retry wget -O - ${LIBCXXABI_URL} | tar --strip-components=1 -xJ -C llvm/projects/libcxxabi
        (cd llvm/build && cmake .. -DCMAKE_INSTALL_PREFIX=${LLVM_INSTALL})
        (cd llvm/build/projects/libcxx && make install -j2)
        (cd llvm/build/projects/libcxxabi && make install -j2)

        export CXXFLAGS="-isystem ${LLVM_INSTALL}/include/c++/v1"
        export LDFLAGS="-L ${LLVM_INSTALL}/lib -l c++ -l c++abi"
        export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${LLVM_INSTALL}/lib"
      fi
    fi

# ==================================================================================================
#     Script
# ==================================================================================================

before_script:

  # --------------------------------------------------------------------------
  #     Info Output
  # --------------------------------------------------------------------------

  # travis environment
  - echo "PATH = $PATH"
  - echo "HOME = $HOME"
  - echo ${CXX}
  - echo ${COMPILER}
  - ${CXX} --version
  - ${COMPILER} --version
  - cmake --version

  # export cmake variables
  # in this CI environment, we default to building debug, so that we do not have to set that
  # for the majority of the jobs in the build matrix, and only set to release if the env is set.
  - export GENESIS_DEBUG=ON
  - export GENESIS_BUILD_TYPE=DEBUG
  - export GENESIS_USE_OPENMP=ON
  - export GENESIS_USE_ZLIB=ON
  - if [[ "${BUILD_TYPE}" == "RELEASE" ]]; then export GENESIS_DEBUG=OFF; fi
  - if [[ "${BUILD_TYPE}" == "RELEASE" ]]; then export GENESIS_BUILD_TYPE=RELEASE; fi
  - if [[ "${OPENMP}" == "OFF" ]]; then export GENESIS_USE_OPENMP=OFF; fi
  - if [[ "${ZLIB}" == "OFF" ]]; then export GENESIS_USE_ZLIB=OFF; fi

script:

  # --------------------------------------------------------------------------
  #     Build Script
  # --------------------------------------------------------------------------

  # set up directories
  - cd "${TRAVIS_BUILD_DIR}"
  - mkdir build
  - cd build

  # build
  - cmake -DCMAKE_CXX_COMPILER=${COMPILER} -DGENESIS_USE_OPENMP=${GENESIS_USE_OPENMP} -DGENESIS_USE_ZLIB=${GENESIS_USE_ZLIB} -DCMAKE_BUILD_TYPE=${GENESIS_BUILD_TYPE} ..
  - make -j 2
  - cd ..