CMake Build Tooling

Learning about CMake while doing my C++ Developments

CMake is a cross-platform build system generator that helps manage and automate the build process for software projects. Its primary purpose is to generate build files for different platforms and environments, allowing developers to compile code in a consistent way. CMake supports multiple compilers and operating systems and can generate native build environments like Makefiles, Ninja, or Visual Studio projects.

Facilities provided by CMake include:

• Platform Independence: Simplifies creating build scripts that work across different platforms.
• Modularity: Allows separation of project components into reusable modules.
• Custom Build Configuration: Offers flexible options for debugging, optimizing, and testing builds.
• Dependency Management: Helps manage project dependencies, especially for large and complex projects.
• Integration: Supports various compilers and tools, including IDEs, unit testing frameworks, and version control systems.

It’s widely used for C/C++ projects but is adaptable for many programming languages.

CMakeLists.txt example from my Tic-Tac-Toe C++ project

Here is the output from ChatGPT when asked to document my CMakeLists.txt from my Tic-Tac-Toe C++ application.

1. Setting the Minimum CMake Version

   cmake_minimum_required(VERSION 3.10)
   

   • Purpose: This command specifies the minimum version of CMake required to build the project. In this case, it’s CMake 3.10.
   • Why it’s important: Ensures that users have a compatible version of CMake with features that your build requires.
2. Project Declaration

   project(tic-tac-toe VERSION 1.0.0 LANGUAGES CXX)
   

   • Purpose: Defines the project name (tic-tac-toe) and the programming language used (CXX for C++). The project is also versioned (1.0.0), which is useful for version control and packaging.
   • Why it’s important: This sets the global project metadata, ensuring that tools and packages can reference the correct version and language.
3. Version Variables

   set(VERSION_MAJOR 1)
   set(VERSION_MINOR 0)
   set(VERSION_PATCH 0)
   

   • Purpose: These variables define the version components of the project (major, minor, and patch numbers).
   • Why it’s important: Allows easy modification of the version and enables version-based configuration or output.
4. Operating System and Architecture Detection

   if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
    set(OS_NAME "Windows")
   elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
    set(OS_NAME "Linux")
   elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
    set(OS_NAME "macOS")
   else()
    set(OS_NAME "UnknownOS")
   endif()
   

   • Purpose: This block checks the system’s OS and sets an OS_NAME variable accordingly.
   • Why it’s important: Different OSes may require different configurations or file paths. This helps in producing OS-specific build artifacts.

     if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|amd64")
      set(ARCH_NAME "x64")
     elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64")
      set(ARCH_NAME "ARM64")
     elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "armv7l")
      set(ARCH_NAME "ARMv7")
     elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "i386|i686")
      set(ARCH_NAME "x86")
     else()
      set(ARCH_NAME "UnknownArch")
     endif()
     

   • Purpose: Detects the system’s processor architecture and sets the ARCH_NAME variable accordingly.
   • Why it’s important: Architectures (e.g., x64, ARM) may also affect build settings or target binaries. This provides flexibility in naming or configuration.
5. Executable Naming

   Copy code
   set(EXECUTABLE_NAME "tic-tac-toe_v${VERSION_MAJOR}.${VERSION_MINOR}.${VERSION_PATCH}_${ARCH_NAME}_${OS_NAME}")
   

   • Purpose: Constructs the executable name based on the version number, architecture, and operating system.
   • Why it’s important: Creates a more informative and unique output file name, especially for cross-platform builds or versioned releases.
6. Include Directories and Source Files

   include_directories(${PROJECT_SOURCE_DIR}/include)
   file(GLOB SOURCES "${PROJECT_SOURCE_DIR}/src/*.cpp")
   

   • Purpose:
     • include_directories tells CMake where to find header files (in the include directory).
     • file(GLOB SOURCES …) collects all .cpp files from the src directory.
   • Why it’s important: Ensures that all necessary source and header files are included for the build process.
7. Executable Target

   add_executable(${EXECUTABLE_NAME} ${SOURCES})
   

   • Purpose: Defines the target executable with the name ${EXECUTABLE_NAME} (constructed earlier) and uses the collected source files ${SOURCES}.
   • Why it’s important: This step tells CMake what to compile and how to name the resulting executable.
8. Output Directory

   set_target_properties(${EXECUTABLE_NAME} PROPERTIES
    RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/build
   )
   

   • Purpose: Specifies where the final executable should be placed (build directory within the project folder).
   • Why it’s important: Keeps the project structure clean by placing the compiled files in a separate directory.

Summary

This CMakeLists.txt file configures a basic C++ project with:

• Cross-platform and cross-architecture support.
• A dynamic naming convention for the output executable based on OS, architecture, and version.
• Organized source and header directories.
• A clean output directory for the compiled executable.

This structure provides flexibility, especially in a multi-platform, multi-architecture environment, making it a great example for projects that need scalable build systems.

As always, happy to hear your thoughts…

Modified By: Martin Thompson

Last Modified: September 11, 2024-12:00:00