Introduction to CMake: Easily Build C++ Projects

In C++ project development, the build process can often be cumbersome, especially in cross-platform development. Today, I would like to introduce a powerful build tool—CMake.

1. What is CMake

CMake is a cross-platform automated build tool widely used in C++ projects. It is primarily used to manage the software compilation process by controlling the compilation flow through the CMakeLists.txt file. This is like a project’s “conductor,” telling the build system how to construct our project step by step.

2. Basic Components of CMake

1. CMakeLists.txt file

• This is the core of CMake; it is a text file that can exist in any directory of the project. This file contains a series of CMake commands. For example, we can specify the project’s compilation rules, such as telling the compiler which standard (like C++11 or C++20) to use for compiling the code; define dependencies, if our project relies on other libraries, we specify how to find and link them here; we can also determine the name of the generated executable file, among other information.

• This is the command line tool to run CMake. After we have written the CMakeLists.txt file, we need to use this tool to parse it. It will generate the corresponding build files for the platform based on the instructions in the file. For example, on Unix systems, it may generate a Makefile, while on Windows systems, it may generate Visual Studio project files.

• Tools like make, nmake, and Visual Studio are build tools. They will perform the actual compilation process based on the build files generated by CMake.

3. Building a Simple Project with CMake

1. Preparation

• First, ensure that CMake is installed on your system. If installed via a package manager (for example, on Ubuntu, you can use sudo apt - get install cmake), follow the prompts; you can also download the installation package from the CMake official website.

simple_cmake_tutorial/
├── CMakeLists.txt
├── main.cpp
└── src/
    └── utils.cpp

• Here, main.cpp is the main program file, and src/utils.cpp is an auxiliary source file.

• Assuming we want to create a simple C++ project, the project directory structure can be set up like this:

cmake_minimum_required(VERSION 3.10)
project(simple_cmake_tutorial LANGUAGES CXX)
set(SOURCE_FILES main.cpp src/utils.cpp)
add_executable(${PROJECT_NAME} ${SOURCE_FILES})

• Here, we first specify the minimum required CMake version as 3.10. Then we set the project name to simple_cmake_tutorial and indicate that this is a C++ project. Next, we define a source file variable SOURCE_FILES that includes the main program file and auxiliary source file. Finally, we create an executable file with the add_executable command, naming it after the project.

• Create the CMakeLists.txt file in the project root directory and fill in the following content:

mkdir build
cd build
cmake ..

• Here, we create a directory named build specifically for storing build files, then enter that directory and run the cmake command to generate the corresponding platform build files.

• Open the command line tool, switch to the project root directory, and execute the following operations:

make
./simple_cmake_tutorial

• If using Visual Studio, you can directly open the generated .sln file and compile and run the project in the IDE.

• If building the project using Makefile on a Unix system, you can run in the build directory:

CMake provides a clean, efficient, and cross-platform way to build C++ projects. By mastering its basic usage, we can more easily develop and manage our projects. I hope everyone can try out this powerful build tool.