CMake - How To Setup A C++ Project

In this post, we will walk through a dummy cmake setup for a C++ application. For the experienced folks this is not going to be very informative, however, can serve as a reference to start building complex projects with.

A Simple Application

I want to create a project called my_app with the following directory structure.

├── CMakeLists.txt
├── src
│   └── main.cc
├── test
│   ├── CMakeLists.txt
│   └── my_app_test.cc
└── third-party
    └── googletest -> /home/manoj/software/googletest

CMakeLists.txt

cmake is not really a replacement for make instead it is a generator of Makefile or other alternatives such as Ninja files.

Basic Config

cmake makes frequent releases, so this will require you to set a minimum required version.

cmake_minimum_required(VERSION 3.16)

Set the compiler version and the language standard version.

# Compiler and Standard
set(CMAKE_C_STANDARD 99)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_C_COMPILER clang-8)
set(CMAKE_CXX_COMPILER clang++-8)

I prefer to set the global project name in a variable and use that all over the rest of the file so that file is readable.

# set the project name
set(this_project my_app)

It’s nice to use variables for other project directories too.

# third party software
set(thirdparty third-party)

Here you are telling which languages are used in the project.

# RUST, Erlang, what else
project(${this_project} C CXX)

Here you are telling that you want to enable testing for this dir and it’s subdirs

enable_testing()

This is used to add googletest as your testing software.

# add google test
add_subdirectory(${thirdparty}/googletest)

Specify the source files and headers

# header files
set(headers
  include/my_app.h
  )

# src files
set(sources
  src/main.cc
  )

Finally, build the executable for this project

# add the executable
add_executable(${this_project} ${sources} ${headers})

I have not tested these, but they are useful if you are building library

target_include_directories(${this_project} PUBLIC include)
target_include_directories(${this_project} PRIVATE src)

The directory consisting tests and it’s own CMakeLists.txt

add_subdirectory(test)

Nice options, especially useful if you are using them with Emacs rtags

set(CMAKE_ENABLE_EXPORTS ON)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)