CMake project builds with Github Actions with windows, but not Linux

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28-08-2024

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Troubleshooting CMake Builds with GitHub Actions: A Case Study

This article analyzes a common problem encountered when building CMake projects with GitHub Actions: successful builds on Windows but failures on Linux. We'll investigate a specific case provided by ElliotScher on Stack Overflow, discovering the root cause and proposing solutions.

The Problem:

ElliotScher encountered an issue building their CMake project with vcpkg on GitHub Actions. The project built successfully on Windows but failed on Linux during the installation of the OpenCV dependency.

Key Error Messages:

• OpenCV build failure: The build process failed when installing the OpenCV library in release mode, resulting in an error message "error: building opencv4:x64-linux failed with: BUILD_FAILED"
• CMake unable to find build program: The CMake configuration process failed, indicating a missing make program.
• Missing compilers: CMake reported that the C and C++ compilers were not set.

Understanding the Errors:

• The OpenCV build failure suggests issues with the build environment or dependencies specific to Linux.
• The missing make program and compilers point to a potential problem with the setup of the Linux environment within the GitHub Actions workflow.

Troubleshooting Steps:

1. Examine the Build Environment:

   • Compiler Compatibility: Ensure that the Linux distribution on GitHub Actions (ubuntu-latest) has the necessary C and C++ compilers installed and configured correctly. The default compilers on Ubuntu typically work well.
   • CMake Version: Verify that the CMake version used in GitHub Actions aligns with the one used on your local machine and virtual machine. Inconsistencies could lead to different build behaviors.
   • VCPkg Installation and Configuration: Double-check the vcpkg installation and configuration steps within your workflow. Ensure that vcpkg is installed correctly and the environment variables are set appropriately, including VCPKG_BINARY_SOURCES.

2. Investigate OpenCV Dependencies:

   • Package Dependencies: OpenCV might have specific dependencies that are not automatically installed on the GitHub Actions runner. Review the OpenCV documentation for any required packages and add them to your workflow.
   • Build Flags: Ensure that the OpenCV build flags used in GitHub Actions are consistent with those used locally.
   • System Libraries: Check if any system libraries or header files needed by OpenCV are missing on the runner. This could involve installing additional packages related to image processing or video.

3. Use a Docker Image:

   • Preconfigured Environment: Consider using a Docker image specifically designed for CMake and vcpkg builds. This image will likely have all necessary dependencies pre-installed, eliminating the potential for environment inconsistencies.
   • Example: DockerHub provides several pre-built images, such as https://hub.docker.com/r/vcpkg/vcpkg.

4. Debugging with Log Files:

   • Analyze Build Logs: Thoroughly examine the build logs generated by vcpkg and CMake for more specific error messages. These logs can provide valuable clues about the underlying cause of the problem.
   • Verbose Output: Use the --verbose flag with CMake commands and --debug flag with vcpkg commands to enable more detailed output during the build process. This can aid in identifying the exact point of failure.

5. Enable GitHub Actions Caching:

   • Speed Up Builds: Utilize the actions/cache action to cache vcpkg dependencies. This can significantly improve build times and reduce the chances of build failures due to network issues or dependency conflicts.

Additional Recommendations:

• Simplify the Workflow: Break down your workflow into smaller steps for easier debugging. This helps isolate the source of the problem.
• Use a dedicated environment for development: For testing and debugging, use a separate virtual machine or container that mirrors the GitHub Actions environment. This allows you to reproduce the issue and test potential solutions before deploying them to GitHub Actions.

Conclusion:

Building CMake projects with GitHub Actions can be challenging, especially when dealing with cross-platform compatibility and dependencies. By carefully analyzing the error messages, troubleshooting potential environment issues, and using debugging techniques, you can successfully identify and resolve build failures. Remember, thorough documentation and best practices for CI/CD workflows are crucial for maintaining a robust and reliable build process.