What is cmake?

CMake is a free, open‑source tool that helps developers turn source code into executable programs. It reads a simple description file (called CMakeLists.txt) and automatically creates the build files needed for different platforms (like Makefiles on Linux, Visual Studio projects on Windows, etc.). In short, CMake is a “build system generator” that makes compiling code easier across many environments.

Let's break it down

  • Source code: the .cpp, .c, .h files you write.
  • CMakeLists.txt: a plain‑text file where you list the source files, required libraries, and build options.
  • Generator: CMake uses the information in CMakeLists.txt to produce native build files (Makefile, Ninja, Xcode, Visual Studio, etc.).
  • Configure step: you run cmake once to generate the native build files.
  • Build step: you run the native tool (e.g., make, ninja, or open the IDE) to actually compile the code.

Why does it matter?

  • Cross‑platform: Write one CMakeLists.txt and build on Windows, macOS, Linux, or embedded systems without rewriting scripts.
  • Scalable: Handles small projects and huge codebases with many libraries and dependencies.
  • Consistent: Keeps build instructions in one place, reducing errors that happen when different developers use different build tools.
  • Integration: Works well with testing frameworks, packaging tools, and continuous‑integration pipelines.

Where is it used?

  • Large open‑source projects like LLVM, OpenCV, Blender, and KDE use CMake.
  • Many commercial software companies adopt it for internal builds because it simplifies multi‑platform releases.
  • It is also common in academic and hobbyist projects that need to compile on several operating systems.

Good things about it

  • Easy to learn basics: Simple commands (add_executable, target_link_libraries) get you started quickly.
  • Extensible: Supports custom commands, modules, and scripts for advanced needs.
  • Active community: Plenty of tutorials, examples, and third‑party modules.
  • Supports modern C++: Can automatically detect compiler features and set appropriate flags.

Not-so-good things

  • Learning curve for advanced features: Complex projects may require deeper CMake knowledge, which can be confusing.
  • Verbose syntax: Some find the CMake language less intuitive than other build tools (e.g., Meson, Bazel).
  • Generated files: The extra step of generating native build files can feel redundant if you only target one platform.
  • Version differences: Older CMake versions lack newer commands, so projects sometimes require a minimum CMake version, causing compatibility issues on older systems.