Introduction to CMake

• We used to write makefiles to build our projects. But, for large projects, it becomes difficult to maintain and manage.
• CMake is a build system generator. It is used to generate build files for various build systems.
• CMake is a cross-platform build system.
• We write CMakeLists.txt file to configure the build system.
• To build a project, we need to run cmake command.

CMake must know!

• CMake is not a build system.
• CMake is a build-system generator. It generates the build system files.

What are build-system?

• A file that contains code for how to link different files, compile them, etc for the current os/hardware.
• e.g., Makefiles, Ninja, etc.

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A simple cpp file

// main.cpp
#include <iostream>

int main() {
    std::cout << "Hello World!" << std::endl;
    return 0;
}

---

CMakeLists.txt file

# CMakeLists.txt
cmake_minimum_required(VERSION 3.21)
project(cmake-example VERSION 1.0.0 LANGUAGES CXX) // project name, version, languages

add_executable(cpp-codes main.cpp) // executableName,  fileName

• We use CXX for C++ files. Since, '+' will be considered as a operator in CMake.

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Build the project

mkdir build && cd build # to keep the root directory clean
cmake .. # specifying the path of the CMakeLists.txt file
# the above command will generate the build files
cmake --build . # to build the project

---

Run executable

./cpp-codes # to run the executable

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Some important flags 🇬🇧

• -S specify the CMakeLists.txt file path
• -B specify the build directory
• -G specify the build generator name (makefile, ninja, etc.)

mkdir build && cd build
cmake -S .. -B . # option 1
cmake .. # option 2 (builds in the current directory by default)


# =================

# generate the build file for make/ninja
# run `cmake --help` for more info

cmake .. -G "Unix Makefiles"
cmake .. -G "Ninja"