🛠️ CMake without pain: set up the build once and forget

If you've written in C++, you've probably encountered CMake. And maybe you had a moment of despair when everything just is not going to. CMake is a powerful tool, but its syntax and structure often cause pain. Let's figure out how to configure CMake once and correctlyto avoid returning to chaos 💡

🔰 What is CMake?

CMake is a build generation system. It does not compile the code directly, but creates files for assembly for your system: Makefile, Ninja, Xcode, or Visual Studio.

• ✅ Works cross-platform

• ✅ Allows you to customize dependencies

• ✅ Simplifies the assembly of large projects

• ✅ Compatible with IDE and CI/CD

🧱 Basic project structure with CMake

project-root/
├── CMakeLists.txt
├── src/
│   └── main.cpp
├── include/
│   └── mylib.hpp
├── CMakeLists.txt (внутри src/)

📌 Root CMakeLists.txt:

cmake_minimum_required(VERSION 3.15)
project(MyProject)

set(CMAKE_CXX_STANDARD 20)

add_subdirectory(src)

📌 src/CMakeLists.txt:

add_executable(my_app main.cpp)
target_include_directories(my_app PRIVATE ../include)

⚙️ Tips for setting up CMake without pain

1. Use target_* instead of global variables

❌ Bad:

include_directories(./include)

✅ Correct:

target_include_directories(my_app PRIVATE ./include)

2. Add compile_commands.json

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

Helps autocomplete and highlight errors in VS Code and clangd.

3. Always use out-of-source build

mkdir build && cd build
cmake ..
cmake --build .

4. Connect third-party libraries correctly

Example with FetchContent:

include(FetchContent)
FetchContent_Declare(
  json 
  URL https://github.com/nlohmann/json/releases/latest/download/json.hpp
)
FetchContent_MakeAvailable(json)

target_link_libraries(my_app PRIVATE nlohmann_json::nlohmann_json)

🧪 Checklist of a good CMake project

• ✅ CMakeLists.txt is no longer than 30 lines

• ✅ All dependencies through target_*

• ✅ Debug/Release support

• ✅ Out-of-source build

• ✅ Works in terminal and IDE

📚 Want to delve into the topic?
In the attachment Code you will find detailed lessons on CMake and C++, step-by-step exercises, error analysis and convenient practice right on your phone or browser.
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