Getting Started with CMake

CMake is an open-source, cross-platform family of tools designed to build, test and package software. CMake is used to control the software compilation process using simple platform and compiler independent configuration files, and generate native makefiles and workspaces that can be used in the compiler environment of your choice.

I am skipping installation instructions and jumping directly to the usage.
Installed cmake version is 3.22.1

Minimal C++ Project

• Project structure

  <lab_dir>
  ├── build
  └── src
      ├── CMakeLists.txt
      └── main.cpp
    
  2 directories, 2 files
  

• main.cpp

  #include <iostream>
  #include <functional>
    
  int main()
  {
    [out = std::ref(std::cout << "Hello ")]() {
      out.get() << "World\n";
    }();
    return 0;
  }
  

• CMakeLists.txt

  cmake_minimum_required(VERSION 3.5)
  project(lab)
  add_compile_options(-Wall -Wextra -Wpedantic)
  add_executable(lab main.cpp)
  target_compile_features(lab PRIVATE cxx_lambda_init_captures)
  install(TARGETS lab DESTINATION bin)
  

• Run following commands

  cd build
  cmake ../src
  cmake --build . --config Release --target lab
  

Your build is ready!!
An executable with the name lab will be generated in the build directory

• Running the executable

  ➤ ./lab
  Hello World
  

---

Understanding the CMakeLists.txt file

All CMake projects start with a file called CMakeLists.txt and it is expected to be placed at the top of the source tree. CMakeLists.txt is just an ordinary text files that contains cmake commands.
CMake defines its own language which has many things, such as variables, functions, macros, conditional logic, looping, code comments and so on.

The bare minimum commands required for any cmake projects are:

cmake_minimum_required(VERSION 3.5)
project(lab)
add_executable(lab main.cpp)

• cmake_minimum_required command
  cmake_minimum_required(VERSION major.minor[.patch[.tweak]])
  • This should be the first line of CMakeLists.txt. It specifies the minimum version of CMake the project needs.
    This ensures that the particular CMake funtionality is available before proceeding.
  • It enforces policy settings to match CMake behaviour to the specified version.
• project command
  project(projectName [VERSION major[.minor[.patch[.tweak]]]] [LANGUAGES languageName ...])
  • projectName is required. Can contain alphabets, numbers, underscore, hyphen
  • VERSION is optional. Can be used to specify the project version here and other parts of the project can refer to it.
  • LANGUAGES defines the programming languages that should be enabled for the project.

  One of it’s important responsibility is to check the compilers for each enabled language and ensure that they are able to compile and link successfully.

• add_executable command
  add_executable(targetName source1 [source2 ...])
  Tells the CMake to create an executable from the source files.
  When the project is built, an executable with the targetName will be created in the build directory with a platform-dependent name(<targetName>.exe of windows, targetName on unix-based platforms etc.)

• Adding comments: Any line beginning with # is considered as comment.

Summary of commands used in CMakeLists.txt for lab project

Command	Summary
cmake_minimum_required	Sets the minimum required version of cmake for a project.
project	Sets the name of the project.
add_compile_options	Add options to the compilation of source files.
add_executable	Add an executable to the project using the specified source files.
target_compile_features	Add expected compiler features to a target. target_compile_features(<target> <PRIVATE|PUBLIC|INTERFACE> <feature> [...]) Adding this automatically figure out the std=c++ flag to be used for compiler
install	Specify rules to run at install time.

References

Chapter 3 - Professional CMake: A Practical Guide - By Craig Scott