Search code examples
github-actions

Paired values in github actions matrix

I want to build against three compiler versions for a C and C++ project: gcc, gcc-8 and clang (for the C compiler), which should use g++, g++-8 and clang++ respectively for the C++ compiler.

That's 3 configurations total. I won't want to build with the product of all C and C++ compiler versions, i.e,. no gcc/g++-8, etc.

How can I specify a matrix with those three configurations, each which sets two variables?

Currently I'm using this (note that 2 OSes are specified, so it's 6 configs in total):

    strategy:
      matrix:
        os: [ubuntu-16.04, ubuntu-latest]
        cpp_compiler: [g++, g++-8, clang++]
        include:
          - c_compiler: gcc
          - cpp_ompiler: g++-8
            c_compiler: gcc-8
          - cpp_compiler: clang++
            c_compiler: clang

Essentially, the C++ compiler (cpp_compiler) is used as the master version, and then include is used in a hacky way to set c_compiler based on the cpp_compiler version, but there must be something better...

Solution

  • Besides @jidicula's answer, which stores matrix as an array, you can also store it as a map, this will make the workflow more readable.

    So the following workflow should work prettier:

    # simplified

strategy:
  matrix:
    os: [ubuntu-16.04, ubuntu-latest]
    compiler: [ {cpp: g++, c: gcc}, {cpp: g++-8, c: gcc-8}, {cpp: clang++, c: clang} ]
steps:
  - name: Compile with C++ compiler
    run: ${{ matrix.compiler.cpp }} source.cpp
  - name: Compile with C compiler
    run: ${{ matrix.compiler.c }} source.c

    When this workflow is triggered, it will execute 6 times in parallel with different matrix.

    1: matrix.os == ubuntu-16.04, matrix.compiler.cpp == g++, matrix.compiler.c == gcc
2: matrix.os == ubuntu-16.04, matrix.compiler.cpp == g++-8, matrix.compiler.c == gcc-8
3: matrix.os == ubuntu-16.04, matrix.compiler.cpp == clang++, matrix.compiler.c == clang
4: matrix.os == ubuntu-latest, matrix.compiler.cpp == g++, matrix.compiler.c == gcc
5: matrix.os == ubuntu-latest, matrix.compiler.cpp == g++-8, matrix.compiler.c == gcc-8
6: matrix.os == ubuntu-latest, matrix.compiler.cpp == clang++, matrix.compiler.c == clang

    However, whether it is an array or a map, the syntax is currently undocumented, though as of a certain point in time the syntax checker no longer flags it as an error. So all of this may change in the future.