Building with more than one version of a compiler

Question

How can I configure travis-ci such that my project builds with more than one version of a compiler?

Say, I want to build it with gcc-4.8, gcc-4.9, clang-3.4, clang-3.5 and clang-3.6.

I know how to build on both gcc and clang, but not on more than one version of them.

To give a little bit more context, my project is a C++ library and I want to ensure compatibility with those compilers.

Answer 1

It was (and still is) quite painful to figure out what is possible/allowed with Travis CI and what isn't. My current solution looks like this:

language: cpp
matrix:
  include:
    - os: linux
      compiler: gcc
      addons:
        apt:
          sources: ['ubuntu-toolchain-r-test']
          packages: ['g++-4.8']
      env: COMPILER=g++-4.8

    - os: linux
      compiler: gcc
      addons:
        apt:
          sources: ['ubuntu-toolchain-r-test']
          packages: ['g++-4.9']
      env: COMPILER=g++-4.9

    - os: linux
      compiler: gcc
      addons:
        apt:
          sources: ['ubuntu-toolchain-r-test']
          packages: ['g++-5']
      env: COMPILER=g++-5

    - os: linux
      compiler: clang
      env: COMPILER=clang++

    - os: linux
      compiler: clang
      addons:
        apt:
          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.5']
          packages: ['clang-3.5']
      env: COMPILER=clang++-3.5

    - os: linux
      compiler: clang
      addons:
        apt:
          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.6']
          packages: ['clang-3.6']
      env: COMPILER=clang++-3.6

# Activate when 3.7 is released and the repository is available
#    - os: linux
#      compiler: clang
#      addons:
#        apt:
#          sources: ['ubuntu-toolchain-r-test', 'llvm-toolchain-precise-3.7']
#          packages: ['clang-3.7']
#      env: COMPILER=clang++-3.7

# Activate when we are allowed to use MacOS X
#    - os: osx
#      compiler: clang
#      env: COMPILER=clang++

script:
  make CXX=$COMPILER -j3

Some remarks:

• The above uses the container-based infrastructure
• Only one compiler is installed per container - speeds up the build and avoids problems as you often can not install several packages/compilers in parallel
• You can not set CXX directly as Travis CI will overwrite it. You need an intermediate variable like COMPILER
• The clang++ without extension is currently Clang 3.4
• Clang 3.7 is not yet available, but should be shortly
• Clang 3.8 (the development version) from the llvm-toolchain-precise repository is currently black-listed

(Note that the above will change/improve over time, now (2016-01-11) Clang 3.7 is available, as is MacOS X. The above is meant as a starting point, adapt as needed)