example

Cross-Compilation Example

This example demonstrates how to use the docker-cross-cpp images to build a C++ application for multiple platforms from a single Dockerfile.

What's Included

• test.cpp: A simple C++ program
• CMakeLists.txt: CMake build configuration
• Dockerfile: Multi-stage build that cross-compiles the binary
• docker-bake.hcl: Docker Bake configuration for building multiple platforms

How to Use

Building for All Platforms

Build the binary for all configured platforms:

docker buildx bake

This will create binaries in the build/ directory for:

• Linux: amd64, arm64, armv7, 386, riscv64, s390x, ppc64le
• Windows: amd64, 386, arm64, armv7
• Macos: amd64, arm64

Building for Specific Platforms

Build for a single platform:

docker buildx build --platform linux/arm64 -o build .

Or specify multiple platforms:

docker buildx build --platform linux/amd64,linux/arm64,windows/amd64 -o build .

How It Works

The Dockerfile uses a multi-stage build:

1. Build stage: Uses the appropriate cross-cpp image based on $TARGETPLATFORM

   FROM --platform=$BUILDPLATFORM ghcr.io/dseif0x/cross-cpp-$TARGETPLATFORM:latest AS build

2. Copy and compile: Copies source files and runs CMake to build the binary

   COPY CMakeLists.txt .
   COPY test.cpp .
   RUN cmake -S . -B build && cmake --build build

3. Extract binary: The final stage extracts just the compiled binary

The cross-compilation toolchain is automatically configured through:

• CMAKE_TOOLCHAIN_FILE environment variable (pre-set in the images)
• Cross-compiler environment variables (CC, CXX, AR, etc.)

Customizing for Your Project

To adapt this for your own C++ project:

1. Replace test.cpp and CMakeLists.txt with your source files
2. Update the Dockerfile to copy your project files
3. Modify docker-bake.hcl to select which platforms you need
4. Add any additional dependencies to the Dockerfile build stage

Output

Built binaries are extracted to the build/ directory with platform-specific paths:

build/
  linux_amd64/
  linux_arm64/
  windows_amd64/
  ...

Notes

• The images include CMake 3.20+ and Ninja build system
• CMake toolchain files are pre-configured for each platform
• For macOS targets, you may need to adjust the SDK version in the main docker-bake.hcl
• Windows binaries are built with llvm-mingw and target Windows 7+