Cmake

CMake is a cross-platform, open-source build system generator. It uses configuration files named CMakeLists.txt to define the build process. From these files, it generates native build files for various environments, such as Makefiles for Unix-like systems or Visual Studio projects for Windows, allowing developers to use their preferred native build tools.

CMake is an open-source, cross-platform family of tools designed to control the compilation process of software using simple configuration files

Unlike traditional build systems like Makefiles, which are often platform-specific, CMake acts as a “meta-build system”. This means developers write a single set of platform-independent CMakeLists.txt scripts, and CMake uses these scripts to generate native build files (like Makefiles, Visual Studio projects, or Xcode projects) for the target platform. This provides developers with a consistent build process across different operating systems and IDEs, from Windows and macOS to Linux. The primary benefit of this approach is that developers can maintain a single source tree that can be built on multiple platforms without modifying the build configuration.

One of CMake’s high-level features is its target-centric design, which defines build artifacts like executables and libraries. In modern CMake, the build description is a graph of targets and their dependencies. When a target, like an executable, depends on a library target, CMake automatically ensures the library is built before the executable and links them together correctly. This approach is a significant improvement over older, more manual methods. CMake also supports “out-of-source” builds, which generate all build files in a separate directory from the source code. This keeps the source tree clean and allows for multiple, different configurations (e.g., debug and release) to be built from the same source tree without conflict. Other features include cross-platform testing with CTest and packaging with CPack, which can generate installers and packages for various operating systems.

The CMakeLists.txt file uses an imperative, custom scripting language that is used to define a project’s build process. At its most basic, a CMakeLists.txt file requires only a few key commands.

  • cmake_minimum_required(VERSION version_number): Specifies the minimum version of CMake required to configure the project.
  • project(ProjectName): Declares a project and its name.
  • add_executable(TargetName SourceFile1.cpp SourceFile2.cpp): Creates an executable target from the specified source files.
  • add_library(TargetName SourceFile1.cpp): Creates a library target.
  • target_link_libraries(TargetName OtherLibraryTarget): Links a target to one or more libraries.

The language also supports variables, which are referenced using ${VAR_NAME} and can be set using the set() command. This allows for conditional logic using if/endif statements to handle variations in the build environment. For multi-directory projects, the add_subdirectory() command processes the CMakeLists.txt file in another directory, allowing for a hierarchical project structure. Together, these simple commands and features provide a powerful system for configuring and automating the build process for a wide range of software projects.