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Managing C++ Projects Using CMake

From studyplan.dev

This course is about how to use CMake to build C++ projects.

We learned C++ in my degree, but never how to use CMake (maybe because my already credited courses from my previous DEC talked about it). I actually used it a bit in an internship to build a program running on multiple ESP32s with the ESP-IDF.

I want to use it more in my next projects, be it in C or C++.

Sections

Chapter 1 - The C++ Build Process

This chapter was mostly revision of what I already knew about compilers, with added information about compiler flags and the ar program for static libraries.

It presents mostly each step of the compilation process (preprocessing, compiling, assembling, linking) and shows the different tools needed to do it by hand in the CLI before using CMake.

📌 Learned

  • Compiler flags for different steps of the compilation process
  • ar for archiving static libraries
  • Position-Independent Code for dynamic libraries
  • A simple Hello World program with <iostream> is 25k lines after preprocessing since it includes the whole iostream headers

Chapter 2 - Project Structure and Dependency Management

This chapter presents the organization of a C++ project as well as build systems and their limitations for complex projects. It talked about versioning, project layout, API vs ABI, etc.

📌 Learned

  • Typical C++ projet layout consisting of src folder for the source code and private headers, include folder for the public headers andlibs folder for external libraries
  • Two ways of separating multiple parts of a project like core and graphics by either having folder for each part under src and include or having src and include in each folder of each part
  • Compiler flags for linking libraries (-I, -L, -l)
  • Semantic versioning
  • Platform differences such has two file system for a dll on Windows (.lib and .dll) vs .so on Linux and macOS
  • Limitations of Makefiles and IDE Project files such as vendor lock-in, dependency on GUI or the monolithic unreadable single Makefile and duplication when splitting it

Chapter 3 - Introducing CMake

As said before, I had already used CMake in an intership before and was already a familiar with the basics. I therefore did not learn much about the basic commands like add_executable, add_library, target_link_libraries, etc.

I did learn more reasons as to why use CMake and little tips about structure and versions.

📌 Learned

  • Why CMake? portability, reproducibility and consistency, and maintainability and scalability
  • CMake alternatives such as Bazel or Meson, but CMake remains the most widely adopted
  • Tips on choosing a version of CMake:
    • Old enough to be compatible with most tools
    • New enough to have modern features and still be supported
  • Tips about choosing the target_ version of a command: granularity, clarity and transitivity

compile_commands

To generate a compile_commands.json file to be used by the clangd LSP for ease of programming (auto-completion, linting, etc.), add 

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)