Docker Images for C++ CI Workflows

This repository provides two Docker images optimized for use in GitHub Actions CI workflows targeting C++ projects.

Available Images

1. ghcr.io/mattkretz/cplusplus-ci/base

A base image built on Ubuntu 24.04, with several useful packages installed via APT:

• make and ninja
• cmake
• GCC 13 and 14 with -m32 and -mx32 support
• Default gcc/g++ → GCC 14
• Clang 20 and 21 (trunk)

You can set the CXX environment variable to:

• g++-13
• g++-14
• clang++-20
• clang++-21

---

2. ghcr.io/mattkretz/cplusplus-ci/latest

This image builds on the base image and adds:

• GCC 15 and GCC master, compiled from the upstream releases/gcc-15 and master branches
• Installed in:
  • /opt/gcc-15
  • /opt/gcc-master
• Supports -m32 and -mx32 builds
• Default gcc/g++ → GCC 15

You can additionally set the CXX environment variable to:

• g++-15
• g++-master (alias: g++-trunk)

---

Example GitHub CI Workflow

name: Clang

on:
  push:
    branches: [ main ]
  pull_request:

jobs:
  clang:
    strategy:
      fail-fast: false
      matrix:
        version: [20, 21]

    runs-on: ubuntu-latest

    container:
      image: ghcr.io/mattkretz/cplusplus-ci/base

    steps:
      - uses: actions/checkout@v4

      - name: Run test suite
        env:
          CXX: clang++-${{ matrix.version }}
        run: make check

Updates

The images are automatically updated once per month (base) / once per week (latest). There may also be manual updates whenever the feature set needs to change.