CMake (2026-08-19 - 2026-08-20)

Course Information

• Course start: 2026-08-19 at 9:00am

• Setup instructions: Course Preparation, Attendee Workstation Setup

• Agenda: Agenda: CMake (2026-08-19 - 2026-08-20)

Day 1: Basics

Basic material, mandatory:

• Basic Usage: Generators, Building

• Libraries, And Dependencies

• Shared Libraries (Preview)

• Structure - Subdirectories, Dependencies, and Include Paths

• Exercise: Build BoilingPot/DataLogger C++ Project

Final agenda point for day 1: have a look in Agenda: CMake (2026-08-19 - 2026-08-20), and discuss topics for day 2.

Day 2: Less Structured, More Practical

The participants were well able to follow everything, and I was busy upholding my well-structured agenda against their demands 🥷. I really enjoyed day 2: much dynamicity, much live-hacking, less slide-presenting - all in all leading to severe trainer exhaustion.

Source code

We morphed the exercise project into something that is not quite what was foreseen by the agenda. Here’s the link to the outcome on Codeberg:

https://codeberg.org/jfasch/2026-08-19-gluehwein

Yesterday’s Exercise Solution

See also

• Screenplay: Public And Private Include Directories

• Solve Exercise: Build BoilingPot/DataLogger C++ Project together. Discussed matters like what target_include_directories() is, and especially what’s the meaning of PUBLIC, PRIVATE, and INTERFACE.

  See https://codeberg.org/jfasch/cmake-subdirs-structure-dependencies for the solution. The solution also covers installation.

• Installation (“Deployment”), shown live while doing the exercise.

• Targets, Properties, And More, which is actually what the exercise is about.

• The solution uses variables, though sparingly. Cover some of that: C++, Debug/Release, CMake “Programming”, Rants

Structure: public/, private/, src/

See also

• Screenplay: Public And Private Include Directories

Following the screenplay, we restructured the project into something that had more structure. Emphasis was put on when to use PRIVATE to reach one node’s own header files vs. INTERFACE to export usage requirements to using nodes.

For an immediate outcome it is probably best to look into the screenplay’s solution (https://codeberg.org/jfasch/cmake-public-private-src).

Find-Modules: SQLite3

See also

• Screenplay: Adding SQLite3 External Dependency

CMake comes with many “find modules”; show how to use FindSQLite3. Relevant places to look:

• Toplevel CMakeLists.txt for the configure/check step (CMakeLists.txt)

• Depending the data-logger library on SQLite3: data-logger/CMakeLists.txt)

• Source code, naturally: sink-sqlite3.h, sink-sqlite3.cpp

Hand-Writing A Find-Module

See also

• Screenplay: Integrating libmosquitto (MQTT - Handwritten Find-Module)

• Step 1: for the purpose of integrating our own project into another project, I created a simple brute-force find-module that is installed together with the project’s artifacts for use by others. It requires a little CMake programming knowledge, though, which I presented as necessary. See The Language for more.

  Relevant places:

  • The find-module: cmake/FindGluehwein.cmake

  • Installation of it in the toplevel CMakeLists.txt

  Build and install:

  $ cmake -DCMAKE_INSTALL_PREFIX=/home/jfasch/My-Installs/deployment ~/My-Projects/2026-08-19-gluehwein
  $ make
  $ make install
  

• Step 2: use our project from another project. We quickly created such a project (here); it only contains one trivial program that uses our project via the find-module from step1.

  cmake_minimum_required(VERSION 3.16)
  project(DecadentlyCookingWine)
  
  find_package(Gluehwein REQUIRED)     # <-- HERE
  
  add_executable(cook-it cook-it.cpp)
  target_link_libraries(
    cook-it
    Gluehwein::Gluehwein               # <-- AND HERE
  )
  

  Build and use cookery from what’s installed/deployed in /home/jfasch/My-Installs/deployment. We are using a FindGluehwein.cmake from a non-standard location, so we pass CMAKE_MODULE_PATH. The find-module is passed that location too which we also have to pass, separately, unfortunately.

  $ cmake \
      -DCMAKE_MODULE_PATH=/home/jfasch/My-Installs/deployment/share/Modules \
      -DDEPLOYMENT_DIR=/home/jfasch/My-Installs/deployment \
      \
      ~/My-Projects/2026-08-19-gluehwein-user
  $ make
  

Note

Conan is a package manager for C/C++, and probably better suited for such tasks.

CMake Function gluehwein_add_library()

See also

• Screenplay: Function Wrapping add_library()

To defend against code explosion, one usually writes functions to eliminate duplicate code. This is what we did near the end of day 2.

Relevant places:

• The function itself, in cmake/functions.cmake

• Toplevel CMakeLists.txt, including that file - thus inheriting the function’s definition into subdirectories.

• Usage in

  • base/CMakeLists.txt

  • boiling-pot/CMakeLists.txt

  • data-logger/CMakeLists.txt