02. CMake Tutorial, Multi-File C++

CMake

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Prerequisites

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1. How to use CMake with Multi-File?

In this tutorial, we extend the basic example to a more realistic project structure:

• 2 header files (.h)
• 2 source files (.cpp)
• 1 main.cpp

We will learn how to organize and build a multi-file C++ project using CMake.

2. Tutorial

2-1. Project Structure

project/
 ├── CMakeLists.txt
 ├── include/
 │    ├── math_utils.h
 │    └── print_utils.h
 └── src/
      ├── main.cpp
      ├── math_utils.cpp
      └── print_utils.cpp

2-2. Context

Header

include/math_utils.h

#pragma once

int add(int a, int b);
int multiply(int a, int b);

include/print_utils.h

#pragma once

void print_result(const char* label, int value);

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Source Files

src/math_utils.cpp

#include "math_utils.h"

int add(int a, int b) 
{
    return a + b;
}

int multiply(int a, int b) 
{
    return a * b;
}

src/print_utils.cpp

#include <iostream>
#include "print_utils.h"

void print_result(const char* label, int value) 
{
    std::cout << label << ": " << value << std::endl;
}

Main

src/main.cpp

#include "math_utils.h"
#include "print_utils.h"

int main() 
{
    int sum = add(3, 4);
    int product = multiply(3, 4);

    print_result("Sum", sum);
    print_result("Product", product);

    return 0;
}

CMakeLists

cmake_minimum_required(VERSION 3.10) 
project(MyApp) 

# Specify include directory 
include_directories(include) 

# Define executable and source files 
add_executable(MyApp 
	src/main.cpp 
	src/math_utils.cpp
	src/print_utils.cpp 
)

2-3. Context Detail

1. include_directories(include)

• Adds include/ folder to the compiler’s header search path

2. add_executable(...)

add_executable(MyApp
    src/main.cpp
    src/math_utils.cpp
    src/print_utils.cpp
)

• Compile all .cpp files
• Link them together
• Produce executable MyApp

2-4. Build Process

mkdir build
cd build
cmake ..
cmake --build .
Debug\MyApp.exe

3. Compilation Model

Each .cpp file is compiled separately:

math_utils.cpp → math_utils.o
print_utils.cpp → print_utils.o
main.cpp → main.o

Then linked:

math_utils.o + print_utils.o + main.o → MyApp