CMake: Quickstart Guide

CMake remains one of the more mysterious of the cross-compilation utilities: an area in which confusion already runs rampant.

CMake, the popular cross-platform build system and project configuration tool, is a powerful ally in software development. It provides a standardized and efficient way to manage the build process for C, C++, and other programming languages. However, like any tool, CMake can present challenges to newcomers and experienced developers alike. I personally ran into multiple issues that seemed to have no source, which was extremely frustrating. In this blog post, we will explore some common struggles developers face with CMake and share strategies to overcome them.

1. Understanding CMake's Syntax

CMake's scripting language can seem daunting at first, especially for those new to it. The CMake syntax is used to define how your project is built and structured, and it consists of various commands and variables. To overcome this hurdle, consider the following:

• Documentation: The CMake documentation is comprehensive and invaluable. Spend time exploring it and understanding the available commands and variables.

• Start Simple: Begin with a basic project and gradually add complexity. This iterative approach will help you grasp CMake's fundamentals without feeling overwhelmed. Slowly expanding upon a simple “Hello World” implementation also allows you to easily discern what is causing your future errors.

• Online Resources: There are numerous online resources, tutorials, and forums where developers share their CMake experiences and solutions to common issues. Don't hesitate to seek guidance from the CMake community. Perhaps nothing is more valuable that getting 1 on 1 support. If you happen to know someone that has dabbled in CMake, getting their support could be invaluable.

2. Managing Dependencies

Dependency management is a critical aspect of software development, and CMake excels at it. However, handling external libraries and ensuring they are correctly integrated can be challenging.

• FindModules and Config Packages: Many libraries offer CMake support through either FindModules or Config Packages. Use these when available to simplify the integration process.

• Use FetchContent: CMake's FetchContent module can automate the download and integration of dependencies directly into your project, making it easier to manage external libraries.

• CMake's ExternalProject: For more complex scenarios, CMake's ExternalProject can be employed to build external dependencies as part of your project's build process.

3. Cross-Platform Compatibility

One of CMake's core strengths is its cross-platform capabilities. However, ensuring your project works seamlessly on different platforms can be a challenging task.

• Be Explicit: When writing CMake scripts, be explicit about the platforms you are targeting, and use platform-specific conditionals and variables as needed. Making system targeting dynamic can really improve your mental state when constantly switching between platforms.

# Define the target
option(ARM32 "Targeting the Device" OFF)
option(LINUX_X86 "Targeting WSL" OFF)
option(WINDOWS "Targeting Windows" ON)

• Continuous Integration: Utilize continuous integration (CI) tools such as Jenkins, Travis CI, or GitHub Actions to automate builds and tests on multiple platforms. This will help uncover platform-specific issues early in development.

• Compiler Abstraction: When configuring compiler options and flags, consider using CMake's compiler abstraction features. This allows you to write platform-independent code while still specifying compiler-specific settings.

4. Debugging CMake Scripts

Debugging CMake scripts can be challenging due to limited built-in debugging tools.

• message() Command: The message() command is your best friend. Use it to print variables and information during script execution, making it easier to pinpoint issues.

• IDE Integration: Many integrated development environments (IDEs) offer CMake integration with built-in debugging capabilities. Explore how your preferred IDE can assist in debugging CMake scripts. I use Visual Studio Code as my preferred CMake IDE, but I do most of my work from the command line with a custom build utility script.

• Version Updates: Keeping CMake up to date can also help resolve issues, as newer versions often include bug fixes and improvements.

5. Structuring Your Project

Properly structuring your project with CMake can be crucial for maintainability.

• Modularize Your Code: Break your project into smaller, modular components. Each module can have its own CMakeLists.txt file, making it easier to manage and understand your project's structure.

• CMake Presets: CMake Presets are a newer feature that simplifies project configuration. They allow you to define common project configurations and switch between them quickly.

In conclusion, while CMake can pose challenges, mastering it is a rewarding endeavor. With the right resources, a methodical approach, and perseverance, you can overcome common struggles and harness the full power of CMake to streamline your software development process. Whether you are new to CMake or a seasoned developer, embracing its capabilities can make your projects more efficient and cross-platform compatible.